Showing 1–50 of 239 results for author: Russo, F

CubeSats Reach the Millisecond X-Ray Domain: Crab Pulsar Timing with SpIRIT/HERMES

Authors: Wladimiro Leone, R. Mearns, T. Di Salvo, L. Burderi, M. Thomas, M. Trenti, F. Fiore, E. J. Marchesini, R. Campana, G. Baroni, M. Dafcikova, A. Anitra, Y. Evangelista, A. Sanna, S. Puccetti, R. Iaria, S. Barraclough, M. Ortiz del Castillo, R. Bertacin, P. Bellutti, G. Bertuccio, A. Chapman, G. Cabras, F. Ceraudo, T. Chen , et al. (48 additional authors not shown)

Abstract: The High Energy Rapid Modular Ensemble of Satellites (HERMES) instrument is a compact X/$γ$-ray spectrometer operating on board the 6U (11 kg) SpIRIT CubeSat. The payload is particularly well suited for the observation of cosmic transients such as Gamma-Ray Bursts and bright pulsars thanks to its unique broadband sensitivity from a few keV to a few MeV and the temporal resolution down to half a mi… ▽ More The High Energy Rapid Modular Ensemble of Satellites (HERMES) instrument is a compact X/$γ$-ray spectrometer operating on board the 6U (11 kg) SpIRIT CubeSat. The payload is particularly well suited for the observation of cosmic transients such as Gamma-Ray Bursts and bright pulsars thanks to its unique broadband sensitivity from a few keV to a few MeV and the temporal resolution down to half a microsecond. We report here the detection of the $\sim$33~ms Crab pulsar double-peaked pulse profile obtained by considering the canonical Crab ephemerides as provided by the Jodrell Bank catalog. We collected approximately 5.7$\cdot$10$^4$ photons from 730~s of observations, in the 3 keV -- 2 MeV energy band, during a single operation, and achieved a 5$σ$ pulse profile significance in the 3--11.5 keV energy band with binning at the ms scale. The results demonstrate that SpIRIT/HERMES can achieve millisecond timing accuracy at high energies and, thanks to its wide field of view and broad energy band, has the potential to contribute to GRB monitoring in the near future. Such capabilities were previously the domain of flagship observatories, underscoring the performance of the HERMES instrument with its compact form factor. △ Less

Submitted 10 March, 2026; originally announced March 2026.

Comments: Accepted for publication in ApJ (9 March 2026)

Report number: The Astrophysical Journal, 1001, 5 (2026)

Journal ref: ApJ 1001, 5 (2026)

A Note on the Peter-Weyl Theorem

Authors: Y. Bavuma, E. Stevenson, F. G. Russo

Abstract: We introduce some classical concepts in the representation theory of compact groups, in order to use them for a new generalization of the Peter-Weyl Theorem. We mostly deal with functions on locally compact groups possessing large nontrivial compact open subgroups: in fact, we show that these functions can be approximated via others which are locally identical to the well known representative func… ▽ More We introduce some classical concepts in the representation theory of compact groups, in order to use them for a new generalization of the Peter-Weyl Theorem. We mostly deal with functions on locally compact groups possessing large nontrivial compact open subgroups: in fact, we show that these functions can be approximated via others which are locally identical to the well known representative functions. △ Less

Submitted 7 March, 2026; originally announced March 2026.

Comments: 11 pages, 4 figures

MSC Class: 22A10; 22D10; 42A20; 22E35

Leveraging Large Language Models for Causal Discovery: a Constraint-based, Argumentation-driven Approach

Authors: Zihao Li, Fabrizio Russo

Abstract: Causal discovery seeks to uncover causal relations from data, typically represented as causal graphs, and is essential for predicting the effects of interventions. While expert knowledge is required to construct principled causal graphs, many statistical methods have been proposed to leverage observational data with varying formal guarantees. Causal Assumption-based Argumentation (ABA) is a framew… ▽ More Causal discovery seeks to uncover causal relations from data, typically represented as causal graphs, and is essential for predicting the effects of interventions. While expert knowledge is required to construct principled causal graphs, many statistical methods have been proposed to leverage observational data with varying formal guarantees. Causal Assumption-based Argumentation (ABA) is a framework that uses symbolic reasoning to ensure correspondence between input constraints and output graphs, while offering a principled way to combine data and expertise. We explore the use of large language models (LLMs) as imperfect experts for Causal ABA, eliciting semantic structural priors from variable names and descriptions and integrating them with conditional-independence evidence. Experiments on standard benchmarks and semantically grounded synthetic graphs demonstrate state-of-the-art performance, and we additionally introduce an evaluation protocol to mitigate memorisation bias when assessing LLMs for causal discovery. △ Less

Submitted 18 February, 2026; originally announced February 2026.

Comments: 26 pages, including appendix

Some Consequences of the Grunewald-O'Halloran Conjecture for Pseudoquonic Operators

Authors: Fabio Bagarello, Yanga Bavuma, Francesco G. Russo

Abstract: Investigating a recent positive solution of a conjecture of Grunewald and O'Halloran for complex finite dimensional nilpotent Lie algebras, we are in the position to find results of existence and uniqueness for the construction of complex nilpotent Lie algebras of arbitrary dimension via pseudobosonic operators. We involve the so-called theory of the deformation of Lie algebras of Gerstenhaber, in… ▽ More Investigating a recent positive solution of a conjecture of Grunewald and O'Halloran for complex finite dimensional nilpotent Lie algebras, we are in the position to find results of existence and uniqueness for the construction of complex nilpotent Lie algebras of arbitrary dimension via pseudobosonic operators. We involve the so-called theory of the deformation of Lie algebras of Gerstenhaber, in order to prove our main results. There isn't a generalized version of the Grunewald-O'Halloran Conjecture when we consider pseudoquonic operators, which specialize to pseudobosonic operators in many cirumstances. Therefore we prove a result of existence (and a direct construction) of pseudobosonic $O^*$-algebras of operators, but leave open the problem of the uniqueness of the construction. △ Less

Submitted 20 January, 2026; originally announced January 2026.

Comments: A more recent version of this paper, with little changes, will appear in Forum Mathematicum

Forward stochastic integration for adapted processes w.r.t. Riemann-Liouville fractional Brownian motion (Full version)

Authors: Paulo Henrique da Costa, Alberto Ohashi, Francesco Russo

Abstract: This paper provides the time-dependent $L^2$-martingale representation of the forward stochastic integral where the driving noise is the Riemann-Liouville fractional Brownian motion with parameter $\frac{1}{2} < H < 1$ and the integrand is a square-integrable adapted process. As a by-product, we obtain the exact $L^2$-isometry of the forward stochastic integrals based on suitable conditions on tim… ▽ More This paper provides the time-dependent $L^2$-martingale representation of the forward stochastic integral where the driving noise is the Riemann-Liouville fractional Brownian motion with parameter $\frac{1}{2} < H < 1$ and the integrand is a square-integrable adapted process. As a by-product, we obtain the exact $L^2$-isometry of the forward stochastic integrals based on suitable conditions on time-dependent martingale representations of adapted integrands combined with the Nelson's stochastic derivative of the underlying Gaussian driving noise. △ Less

Submitted 14 December, 2025; originally announced December 2025.

Comments: 43 pages

Heterogeneous Graph Neural Networks for Assumption-Based Argumentation

Authors: Preesha Gehlot, Anna Rapberger, Fabrizio Russo, Francesca Toni

Abstract: Assumption-Based Argumentation (ABA) is a powerful structured argumentation formalism, but exact computation of extensions under stable semantics is intractable for large frameworks. We present the first Graph Neural Network (GNN) approach to approximate credulous acceptance in ABA. To leverage GNNs, we model ABA frameworks via a dependency graph representation encoding assumptions, claims and rul… ▽ More Assumption-Based Argumentation (ABA) is a powerful structured argumentation formalism, but exact computation of extensions under stable semantics is intractable for large frameworks. We present the first Graph Neural Network (GNN) approach to approximate credulous acceptance in ABA. To leverage GNNs, we model ABA frameworks via a dependency graph representation encoding assumptions, claims and rules as nodes, with heterogeneous edge labels distinguishing support, derive and attack relations. We propose two GNN architectures - ABAGCN and ABAGAT - that stack residual heterogeneous convolution or attention layers, respectively, to learn node embeddings. Our models are trained on the ICCMA 2023 benchmark, augmented with synthetic ABAFs, with hyperparameters optimised via Bayesian search. Empirically, both ABAGCN and ABAGAT outperform a state-of-the-art GNN baseline that we adapt from the abstract argumentation literature, achieving a node-level F1 score of up to 0.71 on the ICCMA instances. Finally, we develop a sound polynomial time extension-reconstruction algorithm driven by our predictor: it reconstructs stable extensions with F1 above 0.85 on small ABAFs and maintains an F1 of about 0.58 on large frameworks. Our work opens new avenues for scalable approximate reasoning in structured argumentation. △ Less

Submitted 14 November, 2025; v1 submitted 12 November, 2025; originally announced November 2025.

Comments: Accepted to AAAI2026. Version with Appendix

McKean-Vlasov equations with singular coefficients - a review of recent results

Authors: Luca Bondi, Elena Issoglio, Francesco Russo

Abstract: This paper focuses on recent works on McKean-Vlasov stochastic differential equations (SDEs) involving singular coefficients. After recalling the classical framework, we review existing recent literature depending on the type of singularities of the coefficients: on the one hand they satisfy some integrability and measurability conditions only, while on the other hand the drift is allowed to be a… ▽ More This paper focuses on recent works on McKean-Vlasov stochastic differential equations (SDEs) involving singular coefficients. After recalling the classical framework, we review existing recent literature depending on the type of singularities of the coefficients: on the one hand they satisfy some integrability and measurability conditions only, while on the other hand the drift is allowed to be a generalised function. Different types of dependencies on the law of the unknown and different noises will also be considered. McKean-Vlasov SDEs are closely related to non-linear Fokker-Planck equations that are satisfied by the law (or its density) of the unknown. These connections are often established also in this singular setting and will be reviewed here. Important tools for dealing with singular coefficients are also included in the paper, such as Figalli-Trevisan superposition principle, Zvonkin transformation, Markov marginal uniqueness, and stochastic sewing lemma. △ Less

Submitted 31 July, 2025; originally announced July 2025.

The New Architecture of the Online Observation Quality System for the ASTRI Mini-Array Project

Authors: N. Parmiggiani, A. Bulgarelli, L. Castaldini, V. Fioretti, I. Abu, M. Capalbi, O. Catalano, V. Conforti, M. Corpora, A. Di Piano, R. Falco, M. Fiori, F. Gianotti, S. Iovenitti, F. Lucarelli M. C. Maccarone, T. Mineo, D. Mollica, S. Lombardi, G. Panebianco, V. Pastore, A. Rizzo, F. Russo, P. Sangiorgi, S. Scuderi, G. Tosti , et al. (1 additional authors not shown)

Abstract: The ASTRI Mini-Array is an international collaboration led by the Italian National Institute for Astrophysics. The project aims to construct and operate an array of nine Imaging Atmospheric Cherenkov Telescopes to study gamma-ray sources at very high energy (TeV) and perform stellar intensity interferometry observations. We describe the updated Online Observation Quality System (OOQS) software arc… ▽ More The ASTRI Mini-Array is an international collaboration led by the Italian National Institute for Astrophysics. The project aims to construct and operate an array of nine Imaging Atmospheric Cherenkov Telescopes to study gamma-ray sources at very high energy (TeV) and perform stellar intensity interferometry observations. We describe the updated Online Observation Quality System (OOQS) software architecture. The OOQS is one of the subsystems of the Supervisory Control and Data Acquisition (SCADA) system. It aims to execute real-time data quality checks on the data acquired by the Cherenkov cameras and intensity interferometry instruments and provide feedback to both SCADA and the Operator about abnormal conditions detected. The data quality results are stored in the Quality Archive for further investigation and sent to the Operator Human Machine Interface (HMI) through Kafka. △ Less

Submitted 21 July, 2025; originally announced July 2025.

Comments: 4 pages, 1 figure, proceedings of the ADASS XXXIV (2024) conference, to appear in ASP Conference Serie

On the subdirect product of graph bundles

Authors: Yanga Bavuma, Francesco G. Russo, Stefano Spessato

Abstract: The subdirect product of two finite groups $A$ and $B$ is defined as a subgroup of the direct product $A \times B$, which is a well-known notion in finite group theory. While it is clear that, under appropriate choices of sets of generators $S$, $S_A$ and $S_B$, the Cayley graph $Cay(A \times B, S)$ corresponds to the Cartesian product $Cay(A, S_A) \square Cay(B, S_B)$ of two graphs, there is no a… ▽ More The subdirect product of two finite groups $A$ and $B$ is defined as a subgroup of the direct product $A \times B$, which is a well-known notion in finite group theory. While it is clear that, under appropriate choices of sets of generators $S$, $S_A$ and $S_B$, the Cayley graph $Cay(A \times B, S)$ corresponds to the Cartesian product $Cay(A, S_A) \square Cay(B, S_B)$ of two graphs, there is no analogue at the level of graph product that reflects the notion of subdirect product of groups. This is precisely the problem which we discuss here. By using the concept of graph bundles and the corresponding pullbacks, we introduce an operation on graph bundles such that the Cayley graph of the subdirect product of two groups can be described as the total space of the product of the Cayley graphs. This allows us to define the so-called ``network $K$-theory group of a graph'', inspired by the notion of topological $K$-theory, and we are able to investigate an interesting functor from the category of graphs to the category of abelian groups. △ Less

Submitted 19 July, 2025; originally announced July 2025.

Comments: Part of a series of works on the topic; 27pp

MSC Class: 05C76; 05C25; 05C90

Journal ref: Lithuanian Mathematical Journal, 2026 [with some revisions]

On Gradual Semantics for Assumption-Based Argumentation

Authors: Anna Rapberger, Fabrizio Russo, Antonio Rago, Francesca Toni

Abstract: In computational argumentation, gradual semantics are fine-grained alternatives to extension-based and labelling-based semantics . They ascribe a dialectical strength to (components of) arguments sanctioning their degree of acceptability. Several gradual semantics have been studied for abstract, bipolar and quantitative bipolar argumentation frameworks (QBAFs), as well as, to a lesser extent, for… ▽ More In computational argumentation, gradual semantics are fine-grained alternatives to extension-based and labelling-based semantics . They ascribe a dialectical strength to (components of) arguments sanctioning their degree of acceptability. Several gradual semantics have been studied for abstract, bipolar and quantitative bipolar argumentation frameworks (QBAFs), as well as, to a lesser extent, for some forms of structured argumentation. However, this has not been the case for assumption-based argumentation (ABA), despite it being a popular form of structured argumentation with several applications where gradual semantics could be useful. In this paper, we fill this gap and propose a family of novel gradual semantics for equipping assumptions, which are the core components in ABA frameworks, with dialectical strengths. To do so, we use bipolar set-based argumentation frameworks as an abstraction of (potentially non-flat) ABA frameworks and generalise state-of-the-art modular gradual semantics for QBAFs. We show that our gradual ABA semantics satisfy suitable adaptations of desirable properties of gradual QBAF semantics, such as balance and monotonicity. We also explore an argument-based approach that leverages established QBAF modular semantics directly, and use it as baseline. Finally, we conduct experiments with synthetic ABA frameworks to compare our gradual ABA semantics with its argument-based counterpart and assess convergence. △ Less

Submitted 31 July, 2025; v1 submitted 14 July, 2025; originally announced July 2025.

Comments: Accepted to KR2025 - With Appendix

Heavy-Heavy-Light Asymptotics from Thermal Correlators

Authors: Ilija Burić, Francesco Mangialardi, Francesco Russo, Volker Schomerus, Alessandro Vichi

Abstract: We revisit the calculation of spectral densities and heavy-heavy-light (HHL) operator product expansion (OPE) coefficients in three-dimensional conformal field theories using thermal one-point functions on $S^1 \times S^2$. A central element of our analysis is a new inversion formula for one-point functions which is derived via Casimir differential equations. We develop systematic expansions of th… ▽ More We revisit the calculation of spectral densities and heavy-heavy-light (HHL) operator product expansion (OPE) coefficients in three-dimensional conformal field theories using thermal one-point functions on $S^1 \times S^2$. A central element of our analysis is a new inversion formula for one-point functions which is derived via Casimir differential equations. We develop systematic expansions of the spectral density and HHL OPE coefficients in the regime of large $Δ_H$. We validate our analytic tools by comparing the results with the partial wave expansions of thermal one-point functions in free field theories. The algorithms developed for these expansions make full use of Casimir recursion relations, thereby extending their applicability into the heavy exchange regime. In the end, we observe excellent agreement with our analytic predictions and an improvement of up to three orders of magnitude compared to all previous leading order estimates of the CFT data even for moderate values of $Δ_H$. △ Less

Submitted 26 June, 2025; originally announced June 2025.

On the global breadth of finite groups with nontrivial partitions

Authors: Seid Kassaw Muhie, Daniele Ettore Otera, Francesco G. Russo

Abstract: In a series of recent contributions on the notion of global breadth $\mathbf{B}(G)$ of a finite group $G$, it was interesting to observe the structural conditions arising from the classification of finite groups of $\mathbf{B}(G)=8$. This motivated the study of a new class of finite groups, namely… ▽ More In a series of recent contributions on the notion of global breadth $\mathbf{B}(G)$ of a finite group $G$, it was interesting to observe the structural conditions arising from the classification of finite groups of $\mathbf{B}(G)=8$. This motivated the study of a new class of finite groups, namely $\mathcal{H}=\{G \ | \ G \ \mbox{satisfies the condition } \ |G| \le \mathbf{B}(G)(\mathbf{B}(G) + 1)\}$ and very little is known about $\mathcal{H}$. Here we focus on the groups with nontrivial partitions (according to the terminology of Baer, Kegel and Kontorovich), determining first that $\mathbf{B}(G)$ is achieved via the local breadth in connection with the order of maximal cyclic subgroups. Then we show that $\mathcal{H}$ contains projective special linear groups, projective general linear groups and Suzuki groups, supporting the conjecture that all finite groups with nontrivial partitions belong to $\mathcal{H}$. The presence of large families of simple groups in $\mathcal{H}$ is shown for the first time here. △ Less

Submitted 24 June, 2025; originally announced June 2025.

Comments: Continuation of a series of works of the 3rd author on the topic; 14pp

MSC Class: 20D15; 20D60; 20D15

$C^{ 0,1}$ -It{ô} chain rules and generalized solutions of parabolic PDEs

Authors: Carlo Ciccarella, Francesco Russo

Abstract: In this paper we first establish an Itô formula for a finite quadratic variation process $X$ expanding $f(t,X_t),$ when $f$ is of class $C^2$ in space and is absolutely continuous in time. Second, via a Fukushima-Dirichlet decomposition we obtain an explicit chain rule for $f(t,X_t)$, when $X$ is a continuous semimartingale and $f$ is a ``quasi-strong solution'' (in the sense of approximation of c… ▽ More In this paper we first establish an Itô formula for a finite quadratic variation process $X$ expanding $f(t,X_t),$ when $f$ is of class $C^2$ in space and is absolutely continuous in time. Second, via a Fukushima-Dirichlet decomposition we obtain an explicit chain rule for $f(t,X_t)$, when $X$ is a continuous semimartingale and $f$ is a ``quasi-strong solution'' (in the sense of approximation of classical solutions) of a parabolic PDE. △ Less

Submitted 12 May, 2025; originally announced May 2025.

Comments: arXiv admin note: substantial text overlap with arXiv:2407.06243

Quantum Dissipative Continuous Time Crystals

Authors: Felix Russo, Thomas Pohl

Abstract: Continuous time crystals, i.e., nonequilibrium phases with a spontaneously broken continuous time-translational symmetry, have been studied and recently observed in the long-time dynamics of open quantum systems. Here, we investigate a lattice of interacting three-level particles and find two distinct time-crystal phases that cannot be described within mean-field theory. Remarkably, one of them em… ▽ More Continuous time crystals, i.e., nonequilibrium phases with a spontaneously broken continuous time-translational symmetry, have been studied and recently observed in the long-time dynamics of open quantum systems. Here, we investigate a lattice of interacting three-level particles and find two distinct time-crystal phases that cannot be described within mean-field theory. Remarkably, one of them emerges only in the presence of correlations, upon accounting for beyond-mean-field effects. Our findings extend explorations of continuous time-translational symmetry breaking in dissipative systems beyond the classical phenomenology of periodic orbits in a low-dimensional nonlinear system. The proposed model applies directly to the laser-driven dynamics of interacting Rydberg states in neutral atom arrays and suggests that the predicted time-crystal phases are observable in such experiments. △ Less

Submitted 12 September, 2025; v1 submitted 20 March, 2025; originally announced March 2025.

An entropy penalized approach for stochastic optimization with marginal law constraints. Complete version

Authors: Thibaut Bourdais, Nadia Oudjane, Francesco Russo

Abstract: This paper focuses on stochastic optimal control problems with constraints in law, which are rewritten as optimization (minimization) of probability measures problem on the canonical space. We introduce a penalized version of this type of problems by splitting the optimization variable and adding an entropic penalization term. We prove that this penalized version constitutes a good approximation… ▽ More This paper focuses on stochastic optimal control problems with constraints in law, which are rewritten as optimization (minimization) of probability measures problem on the canonical space. We introduce a penalized version of this type of problems by splitting the optimization variable and adding an entropic penalization term. We prove that this penalized version constitutes a good approximation of the original control problem and we provide an alternating procedure which converges, under a so called ''Stability Condition'', to an approximate solution of the original problem. We extend the approach introduced in a previous paperof the same authors including a jump dynamics, non-convex costs and constraints on the marginal laws of the controlled process. The interest of our approach is illustrated by numerical simulations related to demand-side management problems arising in power systems. △ Less

Submitted 17 March, 2025; originally announced March 2025.

Explainable AI in Time-Sensitive Scenarios: Prefetched Offline Explanation Model

Authors: Fabio Michele Russo, Carlo Metta, Anna Monreale, Salvatore Rinzivillo, Fabio Pinelli

Abstract: As predictive machine learning models become increasingly adopted and advanced, their role has evolved from merely predicting outcomes to actively shaping them. This evolution has underscored the importance of Trustworthy AI, highlighting the necessity to extend our focus beyond mere accuracy and toward a comprehensive understanding of these models' behaviors within the specific contexts of their… ▽ More As predictive machine learning models become increasingly adopted and advanced, their role has evolved from merely predicting outcomes to actively shaping them. This evolution has underscored the importance of Trustworthy AI, highlighting the necessity to extend our focus beyond mere accuracy and toward a comprehensive understanding of these models' behaviors within the specific contexts of their applications. To further progress in explainability, we introduce Poem, Prefetched Offline Explanation Model, a model-agnostic, local explainability algorithm for image data. The algorithm generates exemplars, counterexemplars and saliency maps to provide quick and effective explanations suitable for time-sensitive scenarios. Leveraging an existing local algorithm, \poem{} infers factual and counterfactual rules from data to create illustrative examples and opposite scenarios with an enhanced stability by design. A novel mechanism then matches incoming test points with an explanation base and produces diverse exemplars, informative saliency maps and believable counterexemplars. Experimental results indicate that Poem outperforms its predecessor Abele in speed and ability to generate more nuanced and varied exemplars alongside more insightful saliency maps and valuable counterexemplars. △ Less

Submitted 6 March, 2025; originally announced March 2025.

Journal ref: Discovery Science 2024, Springer Nature

HERMES Pathfinder & SpIRIT: a progress report

Authors: F. Fiore, M. Trenti, Y. Evangelista, R. Campana, G. Baroni, F. Ceraudo, M. Citossi, G. Della Casa, G. Dilillo, M. Feroci, M. Fiorini, G. Ghirlanda, C. Labanti, G. La Rosa, E. J. Marchesini, G. Morgante, L. Nava, P. Nogara, A. Nuti, M. Perri, F. Russo, G. Sottile, M. Lavagna. A. Colagrossi, S. Silvestrini, M. Quirino , et al. (65 additional authors not shown)

Abstract: HERMES Pathfinder is an in-orbit demonstration consisting of a constellation of six 3U cubesats hosting simple but innovative X-ray/gamma-ray detectors for the monitoring of cosmic high-energy transients. HERMES-PF, funded by ASI and by the EC Horizon 2020 grant, is scheduled for launch in Q1 2025. An identical X-ray/gamma-ray detector is hosted by the Australian 6U cubesat SpIRIT, launched on Dec… ▽ More HERMES Pathfinder is an in-orbit demonstration consisting of a constellation of six 3U cubesats hosting simple but innovative X-ray/gamma-ray detectors for the monitoring of cosmic high-energy transients. HERMES-PF, funded by ASI and by the EC Horizon 2020 grant, is scheduled for launch in Q1 2025. An identical X-ray/gamma-ray detector is hosted by the Australian 6U cubesat SpIRIT, launched on December 1st 2023. The main objective of HERMES-PF/SpIRIT is to demonstrate that high energy cosmic transients can be detected efficiently by miniatured hardware and localized using triangulation techniques. The HERMES-PF X-ray/gamma-ray detector is made by 60 GAGG:Ce scintillator crystals and 12 2x5 silicon drift detector (SDD) mosaics, used to detect both the cosmic X-rays directly and the optical photons produced by gamma-ray interactions with the scintillator crystals. This design provides a unique broad band spectral coverage from a few keV to a few MeV. Furthermore, the use of fast GAGG:Ce crystals and small SDD cells allows us to reach an exquisite time resolution better than a microsecond. We present a progress report on the missions focusing the discussion on the scientific innovation of the project and on the main lessons learned during the project development including: the importance and the challenges of using distributed architectures to achieve ambitious scientific objectives; the importance of developing critical technologies under science agreements for the realization of high-performing but low-cost payloads; best use of COTS technologies in scientific missions. We finally discuss the prospects of applying these concepts for the creation of an all-sky, all-time monitor to search for the high-energy counterparts of gravitational wave events that Advanced LIGO/Virgo/Kagra will find at the end of this decade and the Einstein Telescope during the 2030s. △ Less

Submitted 25 February, 2025; originally announced February 2025.

Comments: proceedings of the 75th International Astronautical Congress (IAC), Milan, Italy, 14-18 October 2024

Existence and uniqueness of solution to a hyperbolic-parabolic free boundary problem for biofilm growth

Authors: Dieudonné Zirhumanana Balike, Luigi Frunzo, Maria Rosaria Mattei, Fabiana Russo

Abstract: This work presents the existence and uniqueness of solution to a free boundary value problem related to biofilm growth. The problem consists of a system of nonlinear hyperbolic partial differential equations governing the microbial species growth, and a system of parabolic partial differential equations describing the substrate dynamics. The free boundary evolution is governed by an ordinary diffe… ▽ More This work presents the existence and uniqueness of solution to a free boundary value problem related to biofilm growth. The problem consists of a system of nonlinear hyperbolic partial differential equations governing the microbial species growth, and a system of parabolic partial differential equations describing the substrate dynamics. The free boundary evolution is governed by an ordinary differential equation that accounts for the thickness of the biofilm. We use the method of characteristics and fixed point strategies to prove the existence and uniqueness theorem in small and all times. All the equations are converted into integral equations, in particular this transformation is made for the parabolic equations by using the Green's functions. We consider Dirichlet-Neumann and Neumann-Robin boundary conditions for the substrates equations and their extension to the case with variable △ Less

Submitted 25 March, 2025; v1 submitted 26 November, 2024; originally announced November 2024.

Comments: We kindly request the withdrawal of our submission due to a misunderstanding among the co-authors regarding the decision to upload the work to arXiv. Not all authors had agreed to its public release, and the submission was made based on an internal miscommunication. We regret this oversight and appreciate your assistance in addressing this matter

The ground calibration of the HERMES-Pathfinder payload flight models

Authors: G. Dilillo, E. J. Marchesini, G. Baroni, G. Della Casa, R. Campana., Y. Evangelista, A. Guzmán, P. Hedderman, P. Bellutti, G. Bertuccio, F. Ceraudo, M. Citossi, D. Cirrincione, I. Dedolli, E. Demenev, M. Feroci, F. Ficorella, M. Fiorini, M. Gandola, M. Grassi, G. La Rosa, G. Lombardi, P. Malcovati, F. Mele, P. Nogara , et al. (15 additional authors not shown)

Abstract: HERMES-Pathfinder is a space-borne mission based on a constellation of six nano-satellites flying in a low-Earth orbit. The 3U CubeSats, to be launched in early 2025, host miniaturized instruments with a hybrid Silicon Drift Detector/scintillator photodetector system, sensitive to both X-rays and gamma-rays. A seventh payload unit is installed onboard SpIRIT, an Australian-Italian nano-satellite d… ▽ More HERMES-Pathfinder is a space-borne mission based on a constellation of six nano-satellites flying in a low-Earth orbit. The 3U CubeSats, to be launched in early 2025, host miniaturized instruments with a hybrid Silicon Drift Detector/scintillator photodetector system, sensitive to both X-rays and gamma-rays. A seventh payload unit is installed onboard SpIRIT, an Australian-Italian nano-satellite developed by a consortium led by the University of Melbourne and launched in December 2023. The project aims at demonstrating the feasibility of Gamma-Ray Burst detection and localization using miniaturized instruments onboard nano-satellites. The HERMES flight model payloads were exposed to multiple well-known radioactive sources for spectroscopic calibration under controlled laboratory conditions. The analysis of the calibration data allows both to determine the detector parameters, necessary to map instrumental units to accurate energy measurements, and to assess the performance of the instruments. We report on these efforts and quantify features such as spectroscopic resolution and energy thresholds, at different temperatures and for all payloads of the constellation. Finally we review the performance of the HERMES payload as a photon counter, and discuss the strengths and the limitations of the architecture. △ Less

Submitted 8 October, 2024; originally announced October 2024.

Design and development of the HERMES Pathfinder payloads

Authors: R. Campana, Y. Evangelista, F. Fiore, A. Guzman, G. Baroni, G. Della Casa, G. Dilillo, P. Hedderman, E. J. Marchesini, G. Bertuccio, F. Ceraudo, E. Demenev, M. Fiorini, M. Grassi, P. Malcovati, F. Mele, P. Nogara, A. Nuti, M. Perri, S. Pirrotta, S. Pliego-Caballero, S. Puccetti, G. Sottile, F. Russo, S. Trevisan

Abstract: HERMES (High Energy Rapid Modular Ensemble of Satellites) Pathfinder mission aims to observe and localize Gamma Ray Bursts (GRBs) and other transients using a constellation of nanosatellites in low-Earth orbit (LEO). Scheduled for launch in early 2025, the 3U CubeSats will host miniaturized instruments featuring a hybrid Silicon Drift Detector (SDD) and GAGG:Ce scintillator photodetector system, s… ▽ More HERMES (High Energy Rapid Modular Ensemble of Satellites) Pathfinder mission aims to observe and localize Gamma Ray Bursts (GRBs) and other transients using a constellation of nanosatellites in low-Earth orbit (LEO). Scheduled for launch in early 2025, the 3U CubeSats will host miniaturized instruments featuring a hybrid Silicon Drift Detector (SDD) and GAGG:Ce scintillator photodetector system, sensitive to X-rays and gamma-rays across a wide energy range. Each HERMES payload contains 120 SDD cells, each with a sensitive area of 45 mm^2, organized into 12 matrices, reading out 60 12.1x6.94x15.0 mm^3 GAGG:Ce scintillators. Photons interacting with an SDD are identified as X-ray events (2-60 keV), while photons in the 20-2000 keV range absorbed by the crystals produce scintillation light, which is read by two SDDs, allowing event discrimination. The detector system, including front-end and back-end electronics, a power supply unit, a chip-scale atomic clock, and a payload data handling unit, fits within a 10x10x10 cm^3 volume, weighs 1.5 kg, and has a maximum power consumption of about 2 W. This paper outlines the development of the HERMES constellation, the design and selection of the payload detectors, and laboratory testing, presenting the results of detector calibrations and environmental tests to provide a comprehensive status update of the mission. △ Less

Submitted 23 September, 2024; originally announced September 2024.

Comments: 8 pages, 6 figures. Proceedings of SPIE 13093, Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray

Journal ref: Proceedings Volume 13093, Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray; 130936F (2024)

The HERMES (High Energy Rapid Modular Ensemble of Satellites) Pathfinder mission

Authors: Y. Evangelista, F. Fiore, R. Campana, G. Baroni, F. Ceraudo, G. Della Casa, E. Demenev, G. Dilillo, M. Fiorini, G. Ghirlanda, M. Grassi, A. Guzmán, P. Hedderman, E. J. Marchesini, G. Morgante, F. Mele, L. Nava, P. Nogara, A. Nuti, S. Pliego Caballero, I. Rashevskaya, F. Russo, G. Sottile, M. Lavagna, A. Colagrossi , et al. (46 additional authors not shown)

Abstract: HERMES (High Energy Rapid Modular Ensemble of Satellites) Pathfinder is a space-borne mission based on a constellation of six nano-satellites flying in a low-Earth orbit (LEO). The 3U CubeSats, to be launched in early 2025, host miniaturized instruments with a hybrid Silicon Drift Detector/GAGG:Ce scintillator photodetector system, sensitive to X-rays and gamma-rays in a large energy band. HERMES… ▽ More HERMES (High Energy Rapid Modular Ensemble of Satellites) Pathfinder is a space-borne mission based on a constellation of six nano-satellites flying in a low-Earth orbit (LEO). The 3U CubeSats, to be launched in early 2025, host miniaturized instruments with a hybrid Silicon Drift Detector/GAGG:Ce scintillator photodetector system, sensitive to X-rays and gamma-rays in a large energy band. HERMES will operate in conjunction with Australian Space Industry Responsive Intelligent Thermal (SpIRIT) 6U CubeSat, launched in December 2023. HERMES will probe the temporal emission of bright high-energy transients such as Gamma-Ray Bursts (GRBs), ensuring a fast transient localization in a field of view of several steradians exploiting the triangulation technique. HERMES intrinsically modular transient monitoring experiment represents a keystone capability to complement the next generation of gravitational wave experiments. In this paper we outline the scientific case, development and programmatic status of the mission △ Less

Submitted 2 September, 2024; originally announced September 2024.

Comments: 13 pages, 16 figures. Proceedings of SPIE "Astronomical Telescopes and Instrumentation" 2024. arXiv admin note: text overlap with arXiv:2210.13866

Journal ref: Proceedings Volume 13093, Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray; 130931Z (2024)

Thermal One-point Functions and Their Partial Wave Decomposition

Authors: Ilija Buric, Francesco Russo, Volker Schomerus, Alessandro Vichi

Abstract: In this work we address partial wave decompositions of thermal one-point functions in conformal field theories on $S^1 \times S^{d-1}$. With the help of Casimir differential equations we develop efficient algorithms to compute the relevant conformal blocks for an external field of arbitrary spin and with any spin exchange along the thermal circle, at least in three dimensions. This is achieved by… ▽ More In this work we address partial wave decompositions of thermal one-point functions in conformal field theories on $S^1 \times S^{d-1}$. With the help of Casimir differential equations we develop efficient algorithms to compute the relevant conformal blocks for an external field of arbitrary spin and with any spin exchange along the thermal circle, at least in three dimensions. This is achieved by identifying solutions to the Casimir equations with a special class of spherical functions in the harmonic analysis of the conformal group. The resulting blocks are then applied to study the decomposition of one-point functions of the scalar $φ^2$ and the stress tensor $T$ for a three-dimensional free scalar field $φ$. We are able to read off averaged OPE coefficients into exchanged fields of high weight and spin for a complete set of tensor structures. We also extract an asymptotic behaviour of conformal blocks and use it to analyse the density of heavy-heavy-light OPE coefficients for spinning operators, comparing it with semi-classical predictions, such as the dimensions of operators at large charge. △ Less

Submitted 5 August, 2024; originally announced August 2024.

Characteristics and It{ô}'s formula for weak Dirichlet processes: an equivalence result

Authors: Elena Bandini, Francesco Russo

Abstract: The main objective consists in generalizing a well-known It{ô} formula of J. Jacod and A. Shiryaev: given a c{à}dl{à}g process S, there is an equivalence between the fact that S is a semimartingale with given characteristics (B^k , C, $ν$) and a It{ô} formula type expansion of F (S), where F is a bounded function of class C2. This result connects weak solutions of path-dependent SDEs and related m… ▽ More The main objective consists in generalizing a well-known It{ô} formula of J. Jacod and A. Shiryaev: given a c{à}dl{à}g process S, there is an equivalence between the fact that S is a semimartingale with given characteristics (B^k , C, $ν$) and a It{ô} formula type expansion of F (S), where F is a bounded function of class C2. This result connects weak solutions of path-dependent SDEs and related martingale problems. We extend this to the case when S is a weak Dirichlet process. A second aspect of the paper consists in discussing some untreated features of stochastic calculus for finite quadratic variation processes. △ Less

Submitted 24 July, 2024; originally announced July 2024.

Exponential twist of probability measures: drift correction in term of a generalized gradient

Authors: Thibaut Bourdais, Nadia Oudjane, Francesco Russo

Abstract: In this paper we study the exponential twist, i.e. a path-integral exponential change of measure, of a Markovian reference probability measure $¶$. This type of transformation naturally appears in variational representation formulae originating from the theory of large deviations and can be interpreted in some cases, as the solution of a specific stochastic control problem. Under a very general Ma… ▽ More In this paper we study the exponential twist, i.e. a path-integral exponential change of measure, of a Markovian reference probability measure $¶$. This type of transformation naturally appears in variational representation formulae originating from the theory of large deviations and can be interpreted in some cases, as the solution of a specific stochastic control problem. Under a very general Markovian assumption on $¶$, we fully characterize the exponential twist probability measure as the solution of a martingale problem and prove that it inherits the Markov property of the reference measure. The ''generator'' of the martingale problem shows a drift depending on a {\it generalized gradient} of some suitable {\it value function} $v$. △ Less

Submitted 31 March, 2026; v1 submitted 11 July, 2024; originally announced July 2024.

Verification theorem related to a zero sum stochastic differential game, based on a chain rule for non-smooth functions

Authors: Carlo Ciccarella, Francesco Russo

Abstract: In the framework of stochastic zero-sum differential games, we establish a verification theorem, inspired by those existing in stochastic control, to provide sufficient conditions for a pair of feedback controls to form a Nash equilibrium. Suppose the validity of the classical Isaacs' condition and the existence of a (what is termed) quasi-strong solution to the Bellman-Isaacs (BI) equations. If t… ▽ More In the framework of stochastic zero-sum differential games, we establish a verification theorem, inspired by those existing in stochastic control, to provide sufficient conditions for a pair of feedback controls to form a Nash equilibrium. Suppose the validity of the classical Isaacs' condition and the existence of a (what is termed) quasi-strong solution to the Bellman-Isaacs (BI) equations. If the diffusion coefficient of the state equation is non-degenerate, we are able to show the existence of a saddle point constituted by a couple of feedback controls that achieve the value of the game: moreover, the latter is equal to the (necessarily unique) solution of the BI equations. A suitable generalization is available when the diffusion is possibly degenerate. Similarly we have also improved a well-known verification theorem in stochastic control theory. The techniques of stochastic calculus via regularization we use, in particular specific chain rules, are borrowed from a companion paper of the authors. △ Less

Submitted 14 October, 2025; v1 submitted 8 July, 2024; originally announced July 2024.

HERMES: Gamma Ray Burst and Gravitational Wave counterpart hunter

Authors: G. Ghirlanda, L. Nava, O. Salafia, F. Fiore, R. Campana, R. Salvaterra, A. Sanna, W. Leone, Y. Evangelista, G. Dilillo, S. Puccetti, A. Santangelo, M. Trenti, A. Guzmán, P. Hedderman, G. Amelino-Camelia, M. Barbera, G. Baroni, M. Bechini, P. Bellutti, G. Bertuccio, G. Borghi, A. Brandonisio, L. Burderi, C. Cabras , et al. (45 additional authors not shown)

Abstract: Gamma Ray Bursts (GRBs) bridge relativistic astrophysics and multi-messenger astronomy. Space-based gamma/X-ray wide field detectors have proven essential to detect and localize the highly variable GRB prompt emission, which is also a counterpart of gravitational wave events. We study the capabilities to detect long and short GRBs by the High Energy Rapid Modular Ensemble of Satellites (HERMES) Pa… ▽ More Gamma Ray Bursts (GRBs) bridge relativistic astrophysics and multi-messenger astronomy. Space-based gamma/X-ray wide field detectors have proven essential to detect and localize the highly variable GRB prompt emission, which is also a counterpart of gravitational wave events. We study the capabilities to detect long and short GRBs by the High Energy Rapid Modular Ensemble of Satellites (HERMES) Pathfinder (HP) and SpIRIT, namely a swarm of six 3U CubeSats to be launched in early 2025, and a 6U CubeSat launched on December 1st 2023. We also study the capabilities of two advanced configurations of swarms of >8 satellites with improved detector performances (HERMES Constellations). The HERMES detectors, sensitive down to ~2-3 keV, will be able to detect faint/soft GRBs which comprise X-ray flashes and high redshift bursts. By combining state-of-the-art long and short GRB population models with a description of the single module performance, we estimate that HP will detect ~195^{+22}_{-21} long GRBs (3.4^{+0.3}_{-0.8} at redshift z>6) and ~19^{+5}_{-3} short GRBs per year. The larger HERMES Constellations under study can detect between ~1300 and ~3000 long GRBs per year and between ~160 and ~400 short GRBs per year, depending on the chosen configuration, with a rate of long GRBs above z>6 between 30 and 75 per year. Finally, we explore the capabilities of HERMES to detect short GRBs as electromagnetic counterparts of binary neutron star (BNS) mergers detected as gravitational signals by current and future ground-based interferometers. Under the assumption that the GRB jets are structured, we estimate that HP can provide up to 1 (14) yr^{-1} joint detections during the fifth LIGO-Virgo-KAGRA observing run (Einstein Telescope single triangle 10 km arm configuration). These numbers become 4 (100) yr^{-1}, respectively, for the HERMES Constellation configuration. △ Less

Submitted 27 May, 2024; originally announced May 2024.

Comments: 13 pages, 6 figures, 4 tabels. Accepted for publication by Astronomy & Astrophysics

Journal ref: A&A 689, A175 (2024)

Argumentative Causal Discovery

Authors: Fabrizio Russo, Anna Rapberger, Francesca Toni

Abstract: Causal discovery amounts to unearthing causal relationships amongst features in data. It is a crucial companion to causal inference, necessary to build scientific knowledge without resorting to expensive or impossible randomised control trials. In this paper, we explore how reasoning with symbolic representations can support causal discovery. Specifically, we deploy assumption-based argumentation… ▽ More Causal discovery amounts to unearthing causal relationships amongst features in data. It is a crucial companion to causal inference, necessary to build scientific knowledge without resorting to expensive or impossible randomised control trials. In this paper, we explore how reasoning with symbolic representations can support causal discovery. Specifically, we deploy assumption-based argumentation (ABA), a well-established and powerful knowledge representation formalism, in combination with causality theories, to learn graphs which reflect causal dependencies in the data. We prove that our method exhibits desirable properties, notably that, under natural conditions, it can retrieve ground-truth causal graphs. We also conduct experiments with an implementation of our method in answer set programming (ASP) on four datasets from standard benchmarks in causal discovery, showing that our method compares well against established baselines. △ Less

Submitted 3 August, 2024; v1 submitted 18 May, 2024; originally announced May 2024.

Comments: Accepted to KR2024. Version with Appendix

Contestable AI needs Computational Argumentation

Authors: Francesco Leofante, Hamed Ayoobi, Adam Dejl, Gabriel Freedman, Deniz Gorur, Junqi Jiang, Guilherme Paulino-Passos, Antonio Rago, Anna Rapberger, Fabrizio Russo, Xiang Yin, Dekai Zhang, Francesca Toni

Abstract: AI has become pervasive in recent years, but state-of-the-art approaches predominantly neglect the need for AI systems to be contestable. Instead, contestability is advocated by AI guidelines (e.g. by the OECD) and regulation of automated decision-making (e.g. GDPR). In this position paper we explore how contestability can be achieved computationally in and for AI. We argue that contestable AI req… ▽ More AI has become pervasive in recent years, but state-of-the-art approaches predominantly neglect the need for AI systems to be contestable. Instead, contestability is advocated by AI guidelines (e.g. by the OECD) and regulation of automated decision-making (e.g. GDPR). In this position paper we explore how contestability can be achieved computationally in and for AI. We argue that contestable AI requires dynamic (human-machine and/or machine-machine) explainability and decision-making processes, whereby machines can (i) interact with humans and/or other machines to progressively explain their outputs and/or their reasoning as well as assess grounds for contestation provided by these humans and/or other machines, and (ii) revise their decision-making processes to redress any issues successfully raised during contestation. Given that much of the current AI landscape is tailored to static AIs, the need to accommodate contestability will require a radical rethinking, that, we argue, computational argumentation is ideally suited to support. △ Less

Submitted 3 August, 2024; v1 submitted 17 May, 2024; originally announced May 2024.

Comments: Accepted at KR 2024

About semilinear low dimension Bessel PDEs

Authors: Alberto Ohashi, Francesco Russo, Alan Teixeira

Abstract: We prove existence and uniqueness of solutions of a semilinear PDE driven by a Bessel type generator$L^δ$ with low dimension $0 < δ< 1$. $L^δ$ is a local operator, whose drift is thederivative of $x \mapsto \log (\vert x\vert)$:in particular it is a Schwartz distribution, whichis not the derivative of a continuous function.The solutions are intended in a duality (''weak'') sensewith respect to… ▽ More We prove existence and uniqueness of solutions of a semilinear PDE driven by a Bessel type generator$L^δ$ with low dimension $0 < δ< 1$. $L^δ$ is a local operator, whose drift is thederivative of $x \mapsto \log (\vert x\vert)$:in particular it is a Schwartz distribution, whichis not the derivative of a continuous function.The solutions are intended in a duality (''weak'') sensewith respect to state space$L^2(\mathbb{R}_+, dμ),$ $μ$ being an invariant measure for the Bessel semigroup. △ Less

Submitted 4 April, 2024; originally announced April 2024.

The Online Observation Quality System Implementation for the ASTRI Mini-Array Project

Authors: L. Castaldini, N. Parmiggiani, A. Bulgarelli, L. Baroncelli, V. Fioretti, A. Di Piano, I. Abu, M. Capalbi, O. Catalano, V. Conforti, M. Fiori, F. Gianotti, F. Lucarelli, M. C. Maccarone, T. Mineo, S. Lombardi, V. Pastore, F. Russo, P. Sangiorgi, S. Scuderi, G. Tosti, M. Trifoglio, L. Zampieri

Abstract: The ASTRI Mini-Array project, led by the Italian National Institute for Astrophysics, aims to construct and operate nine Imaging Atmospheric Cherenkov Telescopes for high-energy gamma-ray source study and stellar intensity interferometry. Located at the Teide Astronomical Observatory in Tenerife, the project's software is essential for remote operation, emphasizing the need for prompt feedback on… ▽ More The ASTRI Mini-Array project, led by the Italian National Institute for Astrophysics, aims to construct and operate nine Imaging Atmospheric Cherenkov Telescopes for high-energy gamma-ray source study and stellar intensity interferometry. Located at the Teide Astronomical Observatory in Tenerife, the project's software is essential for remote operation, emphasizing the need for prompt feedback on observations. This contribution introduces the Online Observation Quality System (OOQS) as part of the Supervisory Control And Data Acquisition (SCADA) software. OOQS performs real-time data quality checks on data from Cherenkov cameras and Intensity Interferometry instruments. It provides feedback to SCADA and operators, highlighting abnormal conditions and ensuring quick corrective actions for optimal observations. Results are archived for operator visualization and further analysis. The OOQS data quality pipeline prototype utilizes a distributed application with three main components to handle the maximum array data rate of 1.15 Gb/s. The first is a Kafka consumer that manages the data stream from the Array Data Acquisition System through Apache Kafka, handling the data serialization and deserialization involved in the transmission. The data stream is divided into batches of data written in files. The second component monitors new files and conducts analyses using the Slurm workload scheduler, leveraging its parallel processing capabilities and scalability. Finally, the process results are collected by the last component and stored in the Quality Archive. △ Less

Submitted 2 April, 2024; originally announced April 2024.

Comments: 4 pages, 2 figures, proceedings of the Astronomical Data Analysis Software & Systems XXXIII (ADASS 2023) conference, to appear in ASP Conference Serie

Covariant projective representations of Hilbert-Lie groups

Authors: Karl-Hermann Neeb, Francesco G. Russo

Abstract: Hilbert--Lie groups are Lie groups whose Lie algebra is a real Hilbert space whose scalar product is invariant under the adjoint action. These infinite-dimensional Lie groups are the closest relatives to compact Lie groups. Here we study unitary representations of these groups from various perspectives. First, we address norm-continuous, also called bounded, representations: they are well-known fo… ▽ More Hilbert--Lie groups are Lie groups whose Lie algebra is a real Hilbert space whose scalar product is invariant under the adjoint action. These infinite-dimensional Lie groups are the closest relatives to compact Lie groups. Here we study unitary representations of these groups from various perspectives. First, we address norm-continuous, also called bounded, representations: they are well-known for simple groups, but the general picture is more complicated. Our first main result is a characterization of the discrete decomposability of all bounded representations in terms of boundedness of the set of coroots. We also show that bounded representations of type II and III exist if the set of coroots is unbounded. Second, we use covariance with respect to a one-parameter group of automorphisms to implement some regularity. Here we develop some perturbation theory based on half Lie groups that reduces matters to the case where a ``maximal torus'' is fixed, so that compatible weight decompositions can be studied. Third, we extend the context to projective representations which are covariant for a one-parameter group of automorphisms. Here important families of representations arise from ``bounded extremal weights'', and for these the corresponding central extensions can be determined explicitly, together with all one-parameter groups for which a covariant extension exists. △ Less

Submitted 21 February, 2024; originally announced February 2024.

Comments: 52 pages

Online Handbook of Argumentation for AI: Volume 4

Authors: Lars Bengel, Lydia Blümel, Elfia Bezou-Vrakatseli, Federico Castagna, Giulia D'Agostino, Isabelle Kuhlmann, Jack Mumford, Daphne Odekerken, Fabrizio Russo, Stefan Sarkadi, Madeleine Waller, Andreas Xydis

Abstract: This volume contains revised versions of the papers selected for the fourth volume of the Online Handbook of Argumentation for AI (OHAAI). Previously, formal theories of argument and argument interaction have been proposed and studied, and this has led to the more recent study of computational models of argument. Argumentation, as a field within artificial intelligence (AI), is highly relevant for… ▽ More This volume contains revised versions of the papers selected for the fourth volume of the Online Handbook of Argumentation for AI (OHAAI). Previously, formal theories of argument and argument interaction have been proposed and studied, and this has led to the more recent study of computational models of argument. Argumentation, as a field within artificial intelligence (AI), is highly relevant for researchers interested in symbolic representations of knowledge and defeasible reasoning. The purpose of this handbook is to provide an open access and curated anthology for the argumentation research community. OHAAI is designed to serve as a research hub to keep track of the latest and upcoming PhD-driven research on the theory and application of argumentation in all areas related to AI. △ Less

Submitted 20 December, 2023; originally announced January 2024.

Degenerate McKean-Vlasov equations with drift in anisotropic negative Besov spaces

Authors: Elena Issoglio, Stefano Pagliarani, Francesco Russo, Davide Trevisani

Abstract: The paper is concerned with a McKean-Vlasov type SDE with drift in anisotropic Besov spaces with negative regularity and with degenerate diffusion matrix under the weak H{ö}rmander condition. The main result is of existence and uniqueness of a solution in law for the McKean-Vlasov equation, which is formulated as a suitable martingale problem. All analytical tools needed are derived in the paper,… ▽ More The paper is concerned with a McKean-Vlasov type SDE with drift in anisotropic Besov spaces with negative regularity and with degenerate diffusion matrix under the weak H{ö}rmander condition. The main result is of existence and uniqueness of a solution in law for the McKean-Vlasov equation, which is formulated as a suitable martingale problem. All analytical tools needed are derived in the paper, such as the well-posedness of the Fokker-Planck and Kolmogorov PDEs with distributional drift, as well as continuity dependence on the coefficients. The solutions to these PDEs naturally live in anisotropic Besov spaces, for which we developed suitable analytical inequalities, such as Schauder estimates. △ Less

Submitted 18 March, 2026; v1 submitted 17 January, 2024; originally announced January 2024.

Shapley-PC: Constraint-based Causal Structure Learning with a Shapley Inspired Framework

Authors: Fabrizio Russo, Francesca Toni

Abstract: Causal Structure Learning (CSL), also referred to as causal discovery, amounts to extracting causal relations among variables in data. CSL enables the estimation of causal effects from observational data alone, avoiding the need to perform real life experiments. Constraint-based CSL leverages conditional independence tests to perform causal discovery. We propose Shapley-PC, a novel method to impro… ▽ More Causal Structure Learning (CSL), also referred to as causal discovery, amounts to extracting causal relations among variables in data. CSL enables the estimation of causal effects from observational data alone, avoiding the need to perform real life experiments. Constraint-based CSL leverages conditional independence tests to perform causal discovery. We propose Shapley-PC, a novel method to improve constraint-based CSL algorithms by using Shapley values over the possible conditioning sets, to decide which variables are responsible for the observed conditional (in)dependences. We prove soundness, completeness and asymptotic consistency of Shapley-PC and run a simulation study showing that our proposed algorithm is superior to existing versions of PC. △ Less

Submitted 10 February, 2025; v1 submitted 18 December, 2023; originally announced December 2023.

Comments: Accepted for CLeaR 2025 - 47 pages (with appendix)

On complete intersections of three quadrics in $\mathbb{P}^7$

Authors: Francesco Russo, Giovanni Staglianò

Abstract: We describe explicit birational maps from some rational complete intersections of three quadrics in $\mathbb{P}^7$ to some prime Fano manifolds together with their Sarkisov decomposition via a single Secant Flop, allowing us to recover the cohomologically associated Castelnuovo surface of general type with $K^2=2$ and $χ=4$ (the double cover of $\mathbb{P}^2$ ramified along the discriminant curve… ▽ More We describe explicit birational maps from some rational complete intersections of three quadrics in $\mathbb{P}^7$ to some prime Fano manifolds together with their Sarkisov decomposition via a single Secant Flop, allowing us to recover the cohomologically associated Castelnuovo surface of general type with $K^2=2$ and $χ=4$ (the double cover of $\mathbb{P}^2$ ramified along the discriminant curve of the net of quadrics defining the complete intersection) as the minimal model of the non ruled irreducible component of the base locus of the inverse maps. In passing we also revisit and reformulate the results in [arXiv:1706.01371] about the existence of infinitely many loci of rational complete intersection of three quadrics in $\mathbb{P}^7$ to produce explicitly some of these loci of low codimension together with many other irreducible unirational components of the Noether--Lefschetz locus. △ Less

Submitted 4 December, 2023; originally announced December 2023.

Comments: 38 pages, 4 tables

MSC Class: 14E08; 14M20; 14M07; 14N05; 14J28; 14J70

The $L^2$-norm of the forward stochastic integral w.r.t. Fractional Brownian motion $H > \frac{1}{2}$

Authors: Alberto Ohashi, Francesco Russo

Abstract: In this article, we present the exact expression of the $L^2$-norm of the forward stochastic integral driven by the multi-dimensional fractional Brownian motion with parameter $\frac{1}{2} < H < 1$. The class of integrands only requires rather weak integrability conditions compatible w.r.t. a random finite measure whose density is expressed as a second-order polynomial of the underlying driving Ga… ▽ More In this article, we present the exact expression of the $L^2$-norm of the forward stochastic integral driven by the multi-dimensional fractional Brownian motion with parameter $\frac{1}{2} < H < 1$. The class of integrands only requires rather weak integrability conditions compatible w.r.t. a random finite measure whose density is expressed as a second-order polynomial of the underlying driving Gaussian noise. A simple consequence of our results is the exact expression of the $L^2$-norm for the pathwise Young integral. △ Less

Submitted 24 October, 2023; originally announced October 2023.

Comments: 31 pages

Chasing Gravitational Waves with the Cherenkov Telescope Array

Authors: Jarred Gershon Green, Alessandro Carosi, Lara Nava, Barbara Patricelli, Fabian Schüssler, Monica Seglar-Arroyo, Cta Consortium, :, Kazuki Abe, Shotaro Abe, Atreya Acharyya, Remi Adam, Arnau Aguasca-Cabot, Ivan Agudo, Jorge Alfaro, Nuria Alvarez-Crespo, Rafael Alves Batista, Jean-Philippe Amans, Elena Amato, Filippo Ambrosino, Ekrem Oguzhan Angüner, Lucio Angelo Antonelli, Carla Aramo, Cornelia Arcaro, Luisa Arrabito , et al. (545 additional authors not shown)

Abstract: The detection of gravitational waves from a binary neutron star merger by Advanced LIGO and Advanced Virgo (GW170817), along with the discovery of the electromagnetic counterparts of this gravitational wave event, ushered in a new era of multimessenger astronomy, providing the first direct evidence that BNS mergers are progenitors of short gamma-ray bursts (GRBs). Such events may also produce very… ▽ More The detection of gravitational waves from a binary neutron star merger by Advanced LIGO and Advanced Virgo (GW170817), along with the discovery of the electromagnetic counterparts of this gravitational wave event, ushered in a new era of multimessenger astronomy, providing the first direct evidence that BNS mergers are progenitors of short gamma-ray bursts (GRBs). Such events may also produce very-high-energy (VHE, > 100GeV) photons which have yet to be detected in coincidence with a gravitational wave signal. The Cherenkov Telescope Array (CTA) is a next-generation VHE observatory which aims to be indispensable in this search, with an unparalleled sensitivity and ability to slew anywhere on the sky within a few tens of seconds. New observing modes and follow-up strategies are being developed for CTA to rapidly cover localization areas of gravitational wave events that are typically larger than the CTA field of view. This work will evaluate and provide estimations on the expected number of of gravitational wave events that will be observable with CTA, considering both on- and off-axis emission. In addition, we will present and discuss the prospects of potential follow-up strategies with CTA. △ Less

Submitted 5 February, 2024; v1 submitted 11 October, 2023; originally announced October 2023.

Comments: Presented at the 38th International Cosmic Ray Conference (ICRC 2023), 2023 (arXiv:2309.08219)

Report number: CTA-ICRC/2023/30

The isometry of symmetric-Stratonovich integrals w.r.t. Fractional Brownian motion $H< \frac{1}{2}$

Authors: Alberto Ohashi, Francesco Russo, Frederi Viens

Abstract: In this work, we present a detailed analysis on the exact expression of the $L^2$-norm of the symmetric-Stratonovich stochastic integral driven by a multi-dimensional fractional Brownian motion $B$ with parameter $\frac{1}{4} < H < \frac{1}{2}$. Our main result is a complete description of a Hilbert space of integrand processes which realizes the $L^2$-isometry where none regularity condition in t… ▽ More In this work, we present a detailed analysis on the exact expression of the $L^2$-norm of the symmetric-Stratonovich stochastic integral driven by a multi-dimensional fractional Brownian motion $B$ with parameter $\frac{1}{4} < H < \frac{1}{2}$. Our main result is a complete description of a Hilbert space of integrand processes which realizes the $L^2$-isometry where none regularity condition in the sense of Malliavin calculus is imposed. The main idea is to exploit the regularity of the conditional expectation of the tensor product of the increments $B_{t-δ,t+δ}\otimes B_{s-ε,s+ε}$ onto the Gaussian space generated by $(B_s,B_t)$ as $(δ,ε)\downarrow 0$. The Hilbert space is characterized in terms of a random Radon $σ$-finite measure on $[0,T]^2$ off diagonal which can be characterized as a product of a non-Markovian version of the stochastic Nelson derivatives. As a by-product, we present the exact explicit expression of the $L^2$-norm of the pathwise rough integral in the sense of Gubinelli. △ Less

Submitted 18 September, 2023; originally announced September 2023.

Prospects for $γ$-ray observations of the Perseus galaxy cluster with the Cherenkov Telescope Array

Authors: The Cherenkov Telescope Array Consortium, :, K. Abe, S. Abe, F. Acero, A. Acharyya, R. Adam, A. Aguasca-Cabot, I. Agudo, A. Aguirre-Santaella, J. Alfaro, R. Alfaro, N. Alvarez-Crespo, R. Alves Batista, J. -P. Amans, E. Amato, E. O. Angüner, L. A. Antonelli, C. Aramo, M. Araya, C. Arcaro, L. Arrabito, K. Asano, Y. Ascasíbar, J. Aschersleben , et al. (542 additional authors not shown)

Abstract: Galaxy clusters are expected to be dark matter (DM) reservoirs and storage rooms for the cosmic-ray protons (CRp) that accumulate along the cluster's formation history. Accordingly, they are excellent targets to search for signals of DM annihilation and decay at gamma-ray energies and are predicted to be sources of large-scale gamma-ray emission due to hadronic interactions in the intracluster med… ▽ More Galaxy clusters are expected to be dark matter (DM) reservoirs and storage rooms for the cosmic-ray protons (CRp) that accumulate along the cluster's formation history. Accordingly, they are excellent targets to search for signals of DM annihilation and decay at gamma-ray energies and are predicted to be sources of large-scale gamma-ray emission due to hadronic interactions in the intracluster medium. We estimate the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse gamma-ray emission from the Perseus galaxy cluster. We perform a detailed spatial and spectral modelling of the expected signal for the DM and the CRp components. For each, we compute the expected CTA sensitivity. The observing strategy of Perseus is also discussed. In the absence of a diffuse signal (non-detection), CTA should constrain the CRp to thermal energy ratio within the radius $R_{500}$ down to about $X_{500}<3\times 10^{-3}$, for a spatial CRp distribution that follows the thermal gas and a CRp spectral index $α_{\rm CRp}=2.3$. Under the optimistic assumption of a pure hadronic origin of the Perseus radio mini-halo and depending on the assumed magnetic field profile, CTA should measure $α_{\rm CRp}$ down to about $Δα_{\rm CRp}\simeq 0.1$ and the CRp spatial distribution with 10% precision. Regarding DM, CTA should improve the current ground-based gamma-ray DM limits from clusters observations on the velocity-averaged annihilation cross-section by a factor of up to $\sim 5$, depending on the modelling of DM halo substructure. In the case of decay of DM particles, CTA will explore a new region of the parameter space, reaching models with $τ_χ>10^{27}$s for DM masses above 1 TeV. These constraints will provide unprecedented sensitivity to the physics of both CRp acceleration and transport at cluster scale and to TeV DM particle models, especially in the decay scenario. △ Less

Submitted 7 September, 2023; originally announced September 2023.

Comments: 93 pages (including author list, appendix and references), 143 figures. Submitted to JCAP

Journal ref: JCAP10(2024)004

An entropy penalized approach for stochastic control problems. Complete version

Authors: Thibaut Bourdais, Nadia Oudjane, Francesco Russo

Abstract: In this paper, we propose an original approach to stochastic control problems. We consider a weak formulation that is written as an optimization (minimization) problem on the space of probability measures. We then introduce a penalized version of this problem obtained by splitting the minimization variables and penalizing the discrepancy between the two variables via an entropy term. We show that… ▽ More In this paper, we propose an original approach to stochastic control problems. We consider a weak formulation that is written as an optimization (minimization) problem on the space of probability measures. We then introduce a penalized version of this problem obtained by splitting the minimization variables and penalizing the discrepancy between the two variables via an entropy term. We show that the penalized problem provides a good approximation of the original problem when the weight of the entropy penalization term is large enough. Moreover, the penalized problem has the advantage of giving rise to two optimization subproblems that are easy to solve in each of the two optimization variables when the other is fixed. We take advantage of this property to propose an alternating optimization procedure that converges to the infimum of the penalized problem with a rate $O(1/k)$, where $k$ is the number of iterations. The relevance of this approach is illustrated by solving a high-dimensional stochastic control problem aimed at controlling consumption in electrical systems. △ Less

Submitted 4 August, 2025; v1 submitted 4 September, 2023; originally announced September 2023.

Continuity Equation for the Flow of Fisher Information in Wave Scattering

Authors: Jakob Hüpfl, Felix Russo, Lukas M. Rachbauer, Dorian Bouchet, Junjie Lu, Ulrich Kuhl, Stefan Rotter

Abstract: Using waves to explore our environment is a widely used paradigm, ranging from seismology to radar technology, and from bio-medical imaging to precision measurements. In all of these fields, the central aim is to gather as much information as possible about an object of interest by sending a probing wave at it and processing the information delivered back to the detector. Here, we demonstrate that… ▽ More Using waves to explore our environment is a widely used paradigm, ranging from seismology to radar technology, and from bio-medical imaging to precision measurements. In all of these fields, the central aim is to gather as much information as possible about an object of interest by sending a probing wave at it and processing the information delivered back to the detector. Here, we demonstrate that an electromagnetic wave scattered at an object carries locally defined and conserved information about all of the object's constitutive parameters. Specifically, we introduce here the density and flux of Fisher information for very general types of wave fields and identify corresponding sources and sinks of information through which all these new quantities satisfy a fundamental continuity equation. We experimentally verify our theoretical predictions by studying a movable object embedded inside a disordered environment and by measuring the corresponding Fisher information flux at microwave frequencies. Our results provide a new understanding of the generation and propagation of information and open up new possibilities for tracking and designing the flow of information even in complex environments. △ Less

Submitted 15 August, 2023; originally announced September 2023.

Comments: 17 pages, 4 figures, plus a methods section and supplementary material

Journal ref: Nature Physics 20, 1294 (2024)

On the Pauli group on 2-qubits in dynamical systems with pseudofermions

Authors: Fabio Bagarello, Yanga Bavuma, Francesco G. Russo

Abstract: The group of matrices $P_1$ of Pauli is a finite 2-group of order 16 and plays a fundamental role in quantum information theory, since it is related to the quantum information on the 1-qubit. Here we show that both $P_1$ and the Pauli 2-group $P_2$ of order 64 on 2-qubits, other than in quantum computing, can also appear in dynamical systems which are described by non self-adjoint Hamiltonians. Th… ▽ More The group of matrices $P_1$ of Pauli is a finite 2-group of order 16 and plays a fundamental role in quantum information theory, since it is related to the quantum information on the 1-qubit. Here we show that both $P_1$ and the Pauli 2-group $P_2$ of order 64 on 2-qubits, other than in quantum computing, can also appear in dynamical systems which are described by non self-adjoint Hamiltonians. This will allow us to represent $P_1$ and $P_2$ in terms of pseudofermionic operators. △ Less

Submitted 9 August, 2023; originally announced August 2023.

Comments: Version of December 2022; 12pp; accepted for publication in Forum Math. after changes due to the report

MSC Class: Primary 81R05; 22E10; Secondary 22E70; 81R30; 81Q12

Stochastic transport by Gaussian noise with regularity greater than 1/2

Authors: Franco Flandoli, Francesco Russo

Abstract: Diffusion with stochastic transport is investigated here when the randomdriving process is a very general Gaussian process, including FractionalBrownian motion. The purpose is the comparison with a deterministic PDE, whichin certain cases represents the equation for the mean value. From thisequation we observe a reduced dissipation property for small times and anenhanced diffusion for large times,… ▽ More Diffusion with stochastic transport is investigated here when the randomdriving process is a very general Gaussian process, including FractionalBrownian motion. The purpose is the comparison with a deterministic PDE, whichin certain cases represents the equation for the mean value. From thisequation we observe a reduced dissipation property for small times and anenhanced diffusion for large times, with respect to delta correlated noisewhen regularity is higher than the one of Brownian motion, a fact interpretedqualitatively here as a signature of the modified dissipation observed for 2Dturbulent fluids due to the inverse cascade. We give results also for thevariance of the solution and for a scaling limit of a two-component noise input. △ Less

Submitted 29 January, 2025; v1 submitted 30 May, 2023; originally announced May 2023.

Spinning Partial Waves for Scattering Amplitudes in $d$ Dimensions

Authors: Ilija Buric, Francesco Russo, Alessandro Vichi

Abstract: Partial wave decomposition is one of the main tools within the modern S-matrix studies. We present a method to compute partial waves for $2\to2$ scattering of spinning particles in arbitrary spacetime dimension. We identify partial waves as matrix elements of the rotation group with definite covariance properties under a subgroup. This allows to use a variety of techniques from harmonic analysis i… ▽ More Partial wave decomposition is one of the main tools within the modern S-matrix studies. We present a method to compute partial waves for $2\to2$ scattering of spinning particles in arbitrary spacetime dimension. We identify partial waves as matrix elements of the rotation group with definite covariance properties under a subgroup. This allows to use a variety of techniques from harmonic analysis in order to construct a novel algebra of weight-shifting operators. All spinning partial waves are generated by the action of these operators on a set of known scalar seeds. The text is accompanied by a {\it Mathematica} notebook to automatically generate partial waves. These results pave the way to a systematic studies of spinning S-matrix bootstrap and positivity bounds. △ Less

Submitted 6 November, 2023; v1 submitted 29 May, 2023; originally announced May 2023.

Comments: v2: minor edits, version published on JHEP

A short note on coproducts of abelian pro-Lie groups

Authors: Wolfgang Herfort, Karl H. Hofmann, Francesco G. Russo

Abstract: The notion of conditional coproduct of a family of abelian pro-Lie groups in the category of abelian pro-Lie groups is introduced. It is shown that the cartesian product of an arbitrary family of abelian pro-Lie groups can be characterized by the universal property of the conditional coproduct. The notion of conditional coproduct of a family of abelian pro-Lie groups in the category of abelian pro-Lie groups is introduced. It is shown that the cartesian product of an arbitrary family of abelian pro-Lie groups can be characterized by the universal property of the conditional coproduct. △ Less

Submitted 23 April, 2023; originally announced April 2023.

Comments: 6 pages

MSC Class: 22E20; 22A05

Factorization number and subgroup commutativity degree via spectral invariants

Authors: Seid Kassaw Muhie, Daniele Ettore Otera, Francesco G. Russo

Abstract: The factorization number $F_2(G)$ of a finite group $G$ is the number of all possible factorizations of $G=HK$ as product of its subgroups $H$ and $K$, while the subgroup commutativity degree $\mathrm{sd}(G)$ of $G$ is the probability of finding two commuting subgroups in $G$ at random. It is known that $\mathrm{sd}(G)$ can be expressed in terms of $F_2(G)$. Denoting by $\mathrm{L}(G)$ the subgrou… ▽ More The factorization number $F_2(G)$ of a finite group $G$ is the number of all possible factorizations of $G=HK$ as product of its subgroups $H$ and $K$, while the subgroup commutativity degree $\mathrm{sd}(G)$ of $G$ is the probability of finding two commuting subgroups in $G$ at random. It is known that $\mathrm{sd}(G)$ can be expressed in terms of $F_2(G)$. Denoting by $\mathrm{L}(G)$ the subgroups lattice of $G$, the non--permutability graph of subgroups $Γ_{\mathrm{L}(G)}$ of $G$ is the graph with vertices in $\mathrm{L}(G) \setminus \mathfrak{C}_{\mathrm{L}(G)}(\mathrm{L}(G))$, where $\mathfrak{C}_{\mathrm{L}(G)}(\mathrm{L}(G))$ is the smallest sublattice of $\mathrm{L}(G)$ containing all permutable subgroups of $G$, and edges obtained by joining two vertices $X,Y$ such that $XY\neq YX$. The spectral properties of $Γ_{\mathrm{L}(G)}$ have been recently investigated in connection with $F_2(G)$ and $\mathrm{sd}(G)$. Here we show a new combinatorial formula, which allows us to express $F_2(G)$, and so $\mathrm{sd}(G)$, in terms of adjacency and Laplacian matrices of $Γ_{\mathrm{L}(G)}$. △ Less

Submitted 17 April, 2023; originally announced April 2023.

Comments: 12 pages, 3 figures, preliminary version

MSC Class: 20D60; 05C25; 05C07; 05C15; 20K27

On locally compact groups of small topological entropy

Authors: Francesco G. Russo, Olwethu Waka

Abstract: We discuss the finiteness of the topological entropy of continuous endomorphims for some classes of locally compact groups. Firstly, we focus on the abelian case, imposing the condition of being compactly generated, and note an interesting behaviour of slender groups. Secondly, we remove the condition of being abelian and consider nilpotent periodic locally compact $p$-groups ($p$ prime), reducing… ▽ More We discuss the finiteness of the topological entropy of continuous endomorphims for some classes of locally compact groups. Firstly, we focus on the abelian case, imposing the condition of being compactly generated, and note an interesting behaviour of slender groups. Secondly, we remove the condition of being abelian and consider nilpotent periodic locally compact $p$-groups ($p$ prime), reducing the computations to the case of Sylow $p$-subgroups. Finally, we investigate locally compact Heisenberg $p$-groups $\mathbb{H}_{n}(\mathbb{Q}_{p})$ on the field $\mathbb{Q}_{p}$ of the $p$-adic rationals with $n$ arbitrary positive integer. △ Less

Submitted 17 April, 2023; originally announced April 2023.

Comments: 11 pages ; 1 figure

MSC Class: 22A05; 37B40; 54C70

The Online Observation Quality System Software Architecture for the ASTRI Mini-Array Project

Authors: N. Parmiggiani, A. Bulgarelli, L. Baroncelli, A. Addis, V. Fioretti, A. Di Piano, M. Capalbi, O. Catalano, V. Conforti, M. Fiori, F. Gianotti, S. Iovenitti, F. Lucarelli, M. C. Maccarone, T. Mineo, S. Lombardi, V. Pastore, F. Russo, P. Sangiorgi, S. Scuderi, G. Tosti, M. Trifoglio, L. Zampieri, the ASTRI Project

Abstract: The ASTRI Mini-Array is an international collaboration led by the Italian National Institute for Astrophysics. This project aims to construct and operate an array of nine Imaging Atmospheric Cherenkov Telescopes to study gamma-ray sources at very high energy (TeV) and perform stellar intensity interferometry observations. We describe the software architecture and the technologies used to implement… ▽ More The ASTRI Mini-Array is an international collaboration led by the Italian National Institute for Astrophysics. This project aims to construct and operate an array of nine Imaging Atmospheric Cherenkov Telescopes to study gamma-ray sources at very high energy (TeV) and perform stellar intensity interferometry observations. We describe the software architecture and the technologies used to implement the Online Observation Quality System (OOQS) for the ASTRI Mini-Array project. The OOQS aims to execute data quality checks on the data acquired in real-time by the Cherenkov cameras and intensity interferometry instruments, and provides feedback to both the Central Control System and the Operator about abnormal conditions detected. The OOQS can notify other sub-systems, triggering their reaction to promptly correct anomalies. The results from the data quality analyses (e.g. camera plots, histograms, tables, and more) are stored in the Quality Archive for further investigation and they are summarised in reports available to the Operator. Once the OOQS results are stored, the operator can visualize them using the Human Machine Interface. The OOQS is designed to manage the high data rate generated by the instruments (up to 4.5 GB/s) and received from the Array Data Acquisition System through the Kafka service. The data are serialized and deserialized during the transmission using the Avro framework. The Slurm workload scheduler executes the analyses exploiting key features such as parallel analyses and scalability. △ Less

Submitted 27 February, 2023; originally announced February 2023.

Comments: 12 pages, 7 Figures. arXiv admin note: text overlap with arXiv:2108.04515

Journal ref: Proceedings Volume 12189, Software and Cyberinfrastructure for Astronomy VII; 121892H (2022)

Analysis of a spherical free boundary problem modelling granular biofilms

Authors: F. Russo, M. R. Mattei, A. Tenore, B. D'Acunto, V. Luongo, L. Frunzo

Abstract: A free boundary value problem related to the genesis of multispecies granular biofilms is presented. The granular biofilm is modelled as a spherical free boundary domain with radial symmetry. The proposed model is conceived in the framework of continuum mechanics and consists of: nonlinear hyperbolic PDEs which model the advective transport and growth of attached species that constitute the granul… ▽ More A free boundary value problem related to the genesis of multispecies granular biofilms is presented. The granular biofilm is modelled as a spherical free boundary domain with radial symmetry. The proposed model is conceived in the framework of continuum mechanics and consists of: nonlinear hyperbolic PDEs which model the advective transport and growth of attached species that constitute the granular biofilm matrix; semilinear elliptic PDEs which govern the diffusive transport and conversion of nutrients; and semilinear elliptic PDEs describing the invasion phenomena and conversion of planktonic cells suspended in the surrounding environment. The evolution of the free boundary is governed by an ODE accounting for microbial growth, attachment, and detachment. By using the method of characteristics, the system of equations constituting the granular biofilm model is converted into an equivalent integral system. Existence and uniqueness of solutions are discussed and proved for the attachment regime using the fixed point theorem. △ Less

Submitted 28 January, 2023; originally announced January 2023.

Comments: 18 pages, preprint version

MSC Class: 35R35; 35L45; 35BXX; 92B05

Multiscale modelling of heavy metals adsorption on algal-bacterial photogranules

Authors: F. Russo, A. Tenore, M. R. Mattei, L. Frunzo

Abstract: A multiscale mathematical model describing the genesis and ecology of algal-bacterial photogranules and the metals biosorption on their solid matrix within a sequencing batch reactor (SBR) is presented. The granular biofilm is modelled as a spherical free boundary domain with radial symmetry and a vanishing initial value. The free boundary evolution is governed by an ODE accounting for microbial g… ▽ More A multiscale mathematical model describing the genesis and ecology of algal-bacterial photogranules and the metals biosorption on their solid matrix within a sequencing batch reactor (SBR) is presented. The granular biofilm is modelled as a spherical free boundary domain with radial symmetry and a vanishing initial value. The free boundary evolution is governed by an ODE accounting for microbial growth, attachment and detachment phenomena. The model is based on systems of PDEs derived from mass conservation principles. Specifically, two systems of nonlinear hyperbolic PDEs model the growth of attached species and the dynamics of free adsorption sites; and two systems of quasi-linear parabolic PDEs govern the diffusive transport and conversion of nutrients and metals. The model is completed with systems of impulsive ordinary differential equations (IDEs) describing the evolution of dissolved substrates, metals, and planktonic and detached biomasses within the granular-based SBR. All main phenomena involved in the process are considered in the mathematical model. Moreover, the dual effect of metal presence on the formation process of photogranules is accounted: metal stimulates the production of EPS by sessile species and negatively affects the metabolic activities of microbial species. To describe the effects related to metal presence, a stimulation term for EPS production and an inhibition term for metal are included in all microbial kinetics. The model is used to examine the role of the microbial species and EPS in the adsorption process, and the effect of metal concentration and adsorption proprieties of biofilm components on the metal removal. Numerical results show that the model accurately describes the photogranules evolution and ecology and confirm the applicability of algal-bacterial photogranules systems for metal-rich wastewater treatment. △ Less

Submitted 28 January, 2023; originally announced January 2023.

Comments: 43 pages, 18 figures, preprint version

MSC Class: 92D25; 35R35; 35Lxx