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Quantum Recoherence in Presence of Excited States in the Early Universe
Authors:
Mattia Cielo,
Simone Scarlatella,
Gianpiero Mangano,
Ofelia Pisanti,
Louis Hamaide
Abstract:
We investigate the quantum-to-classical transition of primordial perturbations within a two-field inflationary framework where an adiabatic mode interacts with an entropic environment. In the case of a massive entropic environment, the attractor Bunch--Davies vacuum plays a special role: it is the only state that can undergo full recoherence, whereas all excited initial states exhibit persistent l…
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We investigate the quantum-to-classical transition of primordial perturbations within a two-field inflationary framework where an adiabatic mode interacts with an entropic environment. In the case of a massive entropic environment, the attractor Bunch--Davies vacuum plays a special role: it is the only state that can undergo full recoherence, whereas all excited initial states exhibit persistent loss of purity. To characterize this behavior, we parameterize excited Gaussian initial states by their Bogoliubov coefficients and compute the purity and Rényi-2 entropy of the reduced adiabatic state as information-theoretic indicators of decoherence dynamics. We find that excited states display \emph{purity-freezing} at a non-zero plateau, where residual quantum correlations persist indefinitely, a qualitative departure from the complete recoherence observed for the Bunch--Davies vacuum. This sensitivity to initial conditions highlights the non-generic nature of full recoherence in the quantum-to-classical transition of inflationary perturbations.
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Submitted 1 December, 2025;
originally announced December 2025.
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Steepest Growth in the Primordial Power Spectrum from Excited States at a Sudden Transition
Authors:
Mattia Cielo,
Gianpiero Mangano,
Ofelia Pisanti,
David Wands
Abstract:
Sudden phase transitions during inflation can give rise to strongly enhanced primordial density perturbations on scales much smaller than those directly probed by cosmic microwave background anisotropies. In this paper, we study the effect of the incoming quantum state on the steepest growth found in the primordial power spectrum using a simple model of an instantaneous transition during single-fi…
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Sudden phase transitions during inflation can give rise to strongly enhanced primordial density perturbations on scales much smaller than those directly probed by cosmic microwave background anisotropies. In this paper, we study the effect of the incoming quantum state on the steepest growth found in the primordial power spectrum using a simple model of an instantaneous transition during single-field inflation. We consider the case of a general de Sitter-invariant initial state for the inflaton field (the $α$-vacuum), and also an incoming state perturbed by a preceding transition. For the $α$-vacua we find that $k^6$ growth is possible for $α>0$, while $k^4$ growth is seen for $α\leq0$, including the standard case of an initial Bunch-Davies vacuum state. The features of an enhanced primordial power spectrum on small scales are thus sensitive to the initial quantum state during inflation. We calculate the scalar-induced gravitational wave power spectrum for each case.
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Submitted 25 November, 2024; v1 submitted 29 October, 2024;
originally announced October 2024.
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Gravitational Wave non-Gaussianity from trans-Planckian Quantum Noise
Authors:
Mattia Cielo,
Matteo Fasiello,
Gianpiero Mangano,
Ofelia Pisanti
Abstract:
We examine the effect of a trans-Planckian phase on the dynamics of inflationary tensor perturbations. To remedy the fact that this regime is not fully captured by standard perturbation theory, we introduce an effective quantum noise source, whose role is regulated by the energy scale $Λ$. The presence of the source modifies the initial conditions for the tensor modes, leaving a distinct imprint.…
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We examine the effect of a trans-Planckian phase on the dynamics of inflationary tensor perturbations. To remedy the fact that this regime is not fully captured by standard perturbation theory, we introduce an effective quantum noise source, whose role is regulated by the energy scale $Λ$. The presence of the source modifies the initial conditions for the tensor modes, leaving a distinct imprint. We study the amplitude and shape of the gravitational wave bispectrum of the model and compare these with their counterparts obtained under the assumptions of Bunch-Davies initial conditions and $α$-vacua states. Depending on the value of the scale $Λ$, we find distinctive signatures associated with both the bispectrum shape and the non-linear parameter $f_{\rm NL}$.
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Submitted 21 September, 2023;
originally announced September 2023.
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Impact of trans-Planckian quantum noise on the Primordial Gravitational Wave spectrum
Authors:
Mattia Cielo,
Gianpiero Mangano,
Ofelia Pisanti
Abstract:
We investigate the impact of stochastic quantum noise due to trans--Planckian effects on the primordial power spectrum for gravity waves during inflation. Given an energy scale Lambda, expected to be close to the Planck scale m_Pl and larger than the Hubble scale H, this noise is described in terms of a source term in the evolution equation for comoving modes k which changes its amplitude growth f…
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We investigate the impact of stochastic quantum noise due to trans--Planckian effects on the primordial power spectrum for gravity waves during inflation. Given an energy scale Lambda, expected to be close to the Planck scale m_Pl and larger than the Hubble scale H, this noise is described in terms of a source term in the evolution equation for comoving modes k which changes its amplitude growth from early times as long as the mode physical wavelength is smaller than Lambda^-1. We model the source term as due to a gas of black holes in the trans--Planckian regime and the corresponding Hawking radiation. In fact, for energy scales larger than, or of the order of Lambda, it is expected that trapped surfaces may form due to large energy densities. At later times the evolution then follows the standard sourceless evolution. We find that this mechanism still leads to a scale-invariant power spectrum of tensor perturbations, with an amplitude that depends upon the ratio Lambda/m_Pl.
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Submitted 17 November, 2022; v1 submitted 8 November, 2022;
originally announced November 2022.
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Sensitivity of KM3NeT to Violation of Equivalence Principle
Authors:
Marco Chianese,
Damiano F. G. Fiorillo,
Gianpiero Mangano,
Gennaro Miele,
Stefano Morisi,
Ofelia Pisanti
Abstract:
The symmetry of the theory of relativity under diffeomorphisms strongly depends on the equivalence principle. Violation of Equivalence Principle (VEP) can be tested by looking for deviations from the standard framework of neutrino oscillations. In recent works, it has been shown that strong constraints on the VEP parameter space can be placed by means of the atmospheric neutrinos observed by the I…
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The symmetry of the theory of relativity under diffeomorphisms strongly depends on the equivalence principle. Violation of Equivalence Principle (VEP) can be tested by looking for deviations from the standard framework of neutrino oscillations. In recent works, it has been shown that strong constraints on the VEP parameter space can be placed by means of the atmospheric neutrinos observed by the IceCube neutrino telescope. In this paper, we focus on the KM3NeT neutrino telescope and perform a forecast analysis to assess its capacity to probe VEP. Most importantly, we examine the crucial role played by systematic uncertainties affecting the neutrino observations. We find that KM3NeT will constrain VEP parameters times the local gravitational potential at the level of $10^{-27}$. Due to the systematic-dominated regime, independent analyses from different neutrino telescopes are fundamental for robustly testing the equivalence principle.
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Submitted 27 July, 2021;
originally announced July 2021.
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IceCube constraints on Violation of Equivalence Principle
Authors:
Damiano F. G. Fiorillo,
Gianpiero Mangano,
Stefano Morisi,
Ofelia Pisanti
Abstract:
Among the information provided by high energy neutrinos, a promising possibility is to analyze the effects of a Violation of Equivalence Principle (VEP) on neutrino oscillations. We analyze the recently released IceCube data on atmospheric neutrino fluxes under the assumption of a VEP and obtain updated constraints on the parameter space with the benchmark choice that neutrinos with different mass…
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Among the information provided by high energy neutrinos, a promising possibility is to analyze the effects of a Violation of Equivalence Principle (VEP) on neutrino oscillations. We analyze the recently released IceCube data on atmospheric neutrino fluxes under the assumption of a VEP and obtain updated constraints on the parameter space with the benchmark choice that neutrinos with different masses couple with different strengths to the gravitational field. In this case we find that the VEP parameters times the local gravitational potential at Earth can be constrained at the level of $10^{-27}$. We show that the constraints from atmospheric neutrinos strongly depend on the assumption that the neutrino eigenstates interacting diagonally with the gravitational field coincide with the mass eigenstates, which is not \textit{a priori} justified: this is particularly clear in the case that the basis of diagonal gravitational interaction coincide with the flavor basis, which cannot be constrained by the observation of atmospheric neutrinos. Finally, we quantitatively study the effect of a VEP on the flavor composition of the astrophysical neutrinos, stressing again the interplay with the basis in which the VEP is diagonal: we find that for some choices of such basis the flavor ratio measured by IceCube can significantly change.
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Submitted 19 May, 2021; v1 submitted 14 December, 2020;
originally announced December 2020.
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Testing Standard and Degenerate Big Bang Nucleosynthesis with BOOMERanG and MAXIMA-1
Authors:
S. Esposito,
G. Mangano,
A. Melchiorri,
G. Miele,
O. Pisanti
Abstract:
We test different Big Bang Nucleosynthesis scenarios using the recent results on the Cosmic Microwave Background Anisotropies provided by the BOOMERanG and MAXIMA-1 experiments versus the observed abundances of 4He, D and 7Li. The likelihood analysis, based on Bayesian approach, shows that, in the case of high deuterium abundance, Y_D=(2.0\pm0.5) 10^{-4}, both standard and degenerate BBN are inc…
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We test different Big Bang Nucleosynthesis scenarios using the recent results on the Cosmic Microwave Background Anisotropies provided by the BOOMERanG and MAXIMA-1 experiments versus the observed abundances of 4He, D and 7Li. The likelihood analysis, based on Bayesian approach, shows that, in the case of high deuterium abundance, Y_D=(2.0\pm0.5) 10^{-4}, both standard and degenerate BBN are inconsistent with the CMBR measurement at more than 3 σ. Assuming low deuterium abundance, Y_D=(3.4\pm0.3) 10^{-5}, the standard BBN model is still inconsistent with present observations at 2 σlevel, while the degenerate BBN results to be compatible. Unless systematics effects will be found in nuclide abundances and/or in CMBR data analysis this result may be a signal in favour of new physics like a large chemical potential of the relic neutrino-antineutrino background.
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Submitted 31 July, 2000; v1 submitted 27 July, 2000;
originally announced July 2000.
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Precision Rates for Nucleon Weak Interactions in Primordial Nucleosynthesis and He-4 Abundance
Authors:
S. Esposito,
G. Mangano,
G. Miele,
O. Pisanti
Abstract:
We report the results of a detailed calculation of nucleon weak interactions relevant for the neutron to proton density ratio at the onset of primordial nucleosynthesis. Radiative electromagnetic corrections, finite nucleon mass terms, thermal radiative effects on weak processes and on neutrino temperature are taken into account to reduce the theoretical uncertainty on $n \leftrightarrow p $ rat…
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We report the results of a detailed calculation of nucleon weak interactions relevant for the neutron to proton density ratio at the onset of primordial nucleosynthesis. Radiative electromagnetic corrections, finite nucleon mass terms, thermal radiative effects on weak processes and on neutrino temperature are taken into account to reduce the theoretical uncertainty on $n \leftrightarrow p $ rates to 1%. This translates into a sensitivity in $^4 He$ mass fraction $Y_p$ prediction up to $10^{-4}$. We find a positive total correction to the Born prediction $δY_p \simeq 0.004$.
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Submitted 9 November, 1998; v1 submitted 19 August, 1998;
originally announced August 1998.