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A timelike entangled island at the initial singularity in a JT FLRW ($Λ>0$) universe
Authors:
K. Sreeman Reddy
Abstract:
It has been argued that there are no islands in FLRW cosmologies with $Λ>0$ and $k=0$ arXiv:2008.01022. We argue that there is a timelike separated island at the initial singularity, and it will resolve the cosmological information paradox. The information about the particles that went beyond the horizon is not lost for our observer. By measuring Hawking radiation, we can get that information from…
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It has been argued that there are no islands in FLRW cosmologies with $Λ>0$ and $k=0$ arXiv:2008.01022. We argue that there is a timelike separated island at the initial singularity, and it will resolve the cosmological information paradox. The information about the particles that went beyond the horizon is not lost for our observer. By measuring Hawking radiation, we can get that information from the past when those particles were near the initial singularity. Similar to how islands inside black holes violate locality, we observe a violation of causality or noncausality but only at the initial singularity, possibly the only region where it is acceptable. We start with a review of timelike entanglement. We will follow an approach similar to the one followed in arXiv:2104.00006 for normal islands. In the end, we conjecture a generalization of the Ryu-Takayanagi or QES prescription for the case of bulk timelike entanglement in dS/CFT correspondence and comment on the emergence of time in dS/CFT correspondence.
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Submitted 27 November, 2022;
originally announced November 2022.
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Constraining properties of asymmetric dark matter candidates from gravitational-wave observations
Authors:
Divya Singh,
Anuradha Gupta,
Emanuele Berti,
Sanjay Reddy,
B. S. Sathyaprakash
Abstract:
The accumulation of certain types of dark matter particles in neutron star cores due to accretion over long timescales can lead to the formation of a mini black hole. In this scenario, the neutron star is destabilized and implodes to form a black hole without significantly increasing its mass. When this process occurs in neutron stars in coalescing binaries, one or both stars might be converted to…
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The accumulation of certain types of dark matter particles in neutron star cores due to accretion over long timescales can lead to the formation of a mini black hole. In this scenario, the neutron star is destabilized and implodes to form a black hole without significantly increasing its mass. When this process occurs in neutron stars in coalescing binaries, one or both stars might be converted to a black hole before they merge. Thus, in the mass range of $\sim \mbox{1--2}\, M_\odot,$ the Universe might contain three distinct populations of compact binaries: one containing only neutron stars, the second population of only black holes, and a third, mixed population consisting of a neutron star and a black hole. However, it is unlikely to have a mixed population as the various timescales allow for both neutron stars to remain or collapse within a short timescale. In this paper, we explore the capability of future gravitational-wave detector networks, including upgrades of Advanced LIGO and Virgo, and new facilities such as the Cosmic Explorer and Einstein Telescope (XG network), to discriminate between different populations by measuring the effective tidal deformability of the binary, which is zero for binary black holes but nonzero for binary neutron stars. Furthermore, we show that observing the relative abundances of the different populations can be used to infer the timescale for neutron stars to implode into black holes, and in turn, provide constraints on the particle nature of dark matter. The XG network will infer the implosion timescale to within an accuracy of 0.01 Gyr at 90% credible interval and determine the dark matter mass and interaction cross section to within a factor of 2 GeV and 10 cm$^{-2}$, respectively.
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Submitted 27 October, 2022;
originally announced October 2022.
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The Next Generation Global Gravitational Wave Observatory: The Science Book
Authors:
Vicky Kalogera,
B. S. Sathyaprakash,
Matthew Bailes,
Marie-Anne Bizouard,
Alessandra Buonanno,
Adam Burrows,
Monica Colpi,
Matt Evans,
Stephen Fairhurst,
Stefan Hild,
Mansi M. Kasliwal,
Luis Lehner,
Ilya Mandel,
Vuk Mandic,
Samaya Nissanke,
Maria Alessandra Papa,
Sanjay Reddy,
Stephan Rosswog,
Chris Van Den Broeck,
P. Ajith,
Shreya Anand,
Igor Andreoni,
K. G. Arun,
Enrico Barausse,
Masha Baryakhtar
, et al. (66 additional authors not shown)
Abstract:
The next generation of ground-based gravitational-wave detectors will observe coalescences of black holes and neutron stars throughout the cosmos, thousands of them with exceptional fidelity. The Science Book is the result of a 3-year effort to study the science capabilities of networks of next generation detectors. Such networks would make it possible to address unsolved problems in numerous area…
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The next generation of ground-based gravitational-wave detectors will observe coalescences of black holes and neutron stars throughout the cosmos, thousands of them with exceptional fidelity. The Science Book is the result of a 3-year effort to study the science capabilities of networks of next generation detectors. Such networks would make it possible to address unsolved problems in numerous areas of physics and astronomy, from Cosmology to Beyond the Standard Model of particle physics, and how they could provide insights into workings of strongly gravitating systems, astrophysics of compact objects and the nature of dense matter. It is inevitable that observatories of such depth and finesse will make new discoveries inaccessible to other windows of observation. In addition to laying out the rich science potential of the next generation of detectors, this report provides specific science targets in five different areas in physics and astronomy and the sensitivity requirements to accomplish those science goals.
This report is the second in a six part series of reports by the GWIC 3G Subcommittee: i) Expanding the Reach of Gravitational Wave Observatories to the Edge of the Universe, ii) The Next Generation Global Gravitational Wave Observatory: The Science Book (this report), iii) 3G R&D: R&D for the Next Generation of Ground-based Gravitational Wave Detectors, iv) Gravitational Wave Data Analysis: Computing Challenges in the 3G Era, v) Future Ground-based Gravitational-wave Observatories: Synergies with Other Scientific Communities, and vi) An Exploration of Possible Governance Models for the Future Global Gravitational-Wave Observatory Network.
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Submitted 12 November, 2021;
originally announced November 2021.
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Stringent constraints on neutron-star radii from multimessenger observations and nuclear theory
Authors:
Collin D. Capano,
Ingo Tews,
Stephanie M. Brown,
Ben Margalit,
Soumi De,
Sumit Kumar,
Duncan A. Brown,
Badri Krishnan,
Sanjay Reddy
Abstract:
The properties of neutron stars are determined by the nature of the matter that they contain. These properties can be constrained by measurements of the star's size. We obtain stringent constraints on neutron-star radii by combining multimessenger observations of the binary neutron-star merger GW170817 with nuclear theory that best accounts for density-dependent uncertainties in the equation of st…
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The properties of neutron stars are determined by the nature of the matter that they contain. These properties can be constrained by measurements of the star's size. We obtain stringent constraints on neutron-star radii by combining multimessenger observations of the binary neutron-star merger GW170817 with nuclear theory that best accounts for density-dependent uncertainties in the equation of state. We construct equations of state constrained by chiral effective field theory and marginalize over these using the gravitational-wave observations. Combining this with the electromagnetic observations of the merger remnant that imply the presence of a short-lived hyper-massive neutron star, we find that the radius of a $1.4\,\rm{M}_\odot$ neutron star is $R_{1.4\,\mathrm{M}_\odot} = 11.0^{+0.9}_{-0.6}~{\rm km}$ (90% credible interval). Using this constraint, we show that neutron stars are unlikely to be disrupted in neutron-star black-hole mergers; subsequently, such events will not produce observable electromagnetic emission.
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Submitted 24 March, 2020; v1 submitted 27 August, 2019;
originally announced August 2019.
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Constraining the neutron-matter equation of state with gravitational waves
Authors:
Michael McNeil Forbes,
Sukanta Bose,
Sanjay Reddy,
Dake Zhou,
Arunava Mukherjee,
Soumi De
Abstract:
We show how observations of gravitational waves from binary neutron star (BNS) mergers over the next few years can be combined with insights from nuclear physics to obtain useful constraints on the equation of state (EoS) of dense matter, in particular, constraining the neutron-matter EoS to within 20% between one and two times the nuclear saturation density $n_0\approx 0.16\ {\text{fm}^{-3}}$. Us…
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We show how observations of gravitational waves from binary neutron star (BNS) mergers over the next few years can be combined with insights from nuclear physics to obtain useful constraints on the equation of state (EoS) of dense matter, in particular, constraining the neutron-matter EoS to within 20% between one and two times the nuclear saturation density $n_0\approx 0.16\ {\text{fm}^{-3}}$. Using Fisher information methods, we combine observational constraints from simulated BNS merger events drawn from various population models with independent measurements of the neutron star radii expected from x-ray astronomy (the Neutron Star Interior Composition Explorer (NICER) observations in particular) to directly constrain nuclear physics parameters. To parameterize the nuclear EoS, we use a different approach, expanding from pure nuclear matter rather than from symmetric nuclear matter to make use of recent quantum Monte Carlo (QMC) calculations. This method eschews the need to invoke the so-called parabolic approximation to extrapolate from symmetric nuclear matter, allowing us to directly constrain the neutron-matter EoS. Using a principal component analysis, we identify the combination of parameters most tightly constrained by observational data. We discuss sensitivity to various effects such as different component masses through population-model sensitivity, phase transitions in the core EoS, and large deviations from the central parameter values.
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Submitted 8 April, 2019;
originally announced April 2019.
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The Yet-Unobserved Multi-Messenger Gravitational-Wave Universe
Authors:
Vassiliki Kalogera,
Marrie-Anne Bizouard,
Adam Burrows,
Thomas Janka,
Kei Kotake,
Bronson Messer,
Tony Mezzacappa,
Bernhard Mueller,
Ewald Mueller,
Maria Alessandra Papa,
Sanjay Reddy,
Stephan Rosswog
Abstract:
Observations with next-generation ground-based detectors further enhanced with multi-messenger (electromagnetic and neutrino) detections will allow us to probe new extreme astrophysics. Target sources included: core-collapse supernovae, continuous emission from isolated or accreting neutron stars, and bursts from magnetars and other pulsars.
Observations with next-generation ground-based detectors further enhanced with multi-messenger (electromagnetic and neutrino) detections will allow us to probe new extreme astrophysics. Target sources included: core-collapse supernovae, continuous emission from isolated or accreting neutron stars, and bursts from magnetars and other pulsars.
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Submitted 21 March, 2019;
originally announced March 2019.
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Extreme Gravity and Fundamental Physics
Authors:
B. S. Sathyaprakash,
Alessandra Buonanno,
Luis Lehner,
Chris Van Den Broeck,
P. Ajith,
Archisman Ghosh,
Katerina Chatziioannou,
Paolo Pani,
Michael Puerrer,
Sanjay Reddy,
Thomas Sotiriou,
Salvatore Vitale,
Nicolas Yunes,
K. G. Arun,
Enrico Barausse,
Masha Baryakhtar,
Richard Brito,
Andrea Maselli,
Tim Dietrich,
William East,
Ian Harry,
Tanja Hinderer,
Geraint Pratten,
Lijing Shao,
Maaretn van de Meent
, et al. (4 additional authors not shown)
Abstract:
Future gravitational-wave observations will enable unprecedented and unique science in extreme gravity and fundamental physics answering questions about the nature of dynamical spacetimes, the nature of dark matter and the nature of compact objects.
Future gravitational-wave observations will enable unprecedented and unique science in extreme gravity and fundamental physics answering questions about the nature of dynamical spacetimes, the nature of dark matter and the nature of compact objects.
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Submitted 10 September, 2019; v1 submitted 21 March, 2019;
originally announced March 2019.
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Gravitational waves from compact dark matter objects in the solar system
Authors:
C. J. Horowitz,
M. A. Papa,
S. Reddy
Abstract:
Dark matter could be composed of compact dark objects (CDOs). A close binary of CDOs orbiting in the interior of solar system bodies can be a loud source of gravitational waves (GWs) for the LIGO and VIRGO detectors. We perform the first search ever for this type of signal and rule out close binaries, with separations of order 300 m, orbiting near the center of the Sun with GW frequencies (twice t…
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Dark matter could be composed of compact dark objects (CDOs). A close binary of CDOs orbiting in the interior of solar system bodies can be a loud source of gravitational waves (GWs) for the LIGO and VIRGO detectors. We perform the first search ever for this type of signal and rule out close binaries, with separations of order 300 m, orbiting near the center of the Sun with GW frequencies (twice the orbital frequency) between 50 and 550 Hz and CDO masses above $\approx 10^{-9} M_\odot$. This mass limit is eight orders of magnitude lower than the mass probed in a LIGO search at extra galactic distances.
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Submitted 29 October, 2019; v1 submitted 21 February, 2019;
originally announced February 2019.
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Gravitational Waves from Compact Dark Objects in Neutron Stars
Authors:
C. J. Horowitz,
Sanjay Reddy
Abstract:
Dark matter could be composed of compact dark objects (CDOs). We find that the oscillation of CDOs inside neutron stars can be a detectable source of gravitational waves (GWs). The GW strain amplitude depends on the mass of the CDO, and its frequency is typically in the range 3-5 kHz as determined by the central density of the star. In the best cases, LIGO may be sensitive to CDO masses greater th…
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Dark matter could be composed of compact dark objects (CDOs). We find that the oscillation of CDOs inside neutron stars can be a detectable source of gravitational waves (GWs). The GW strain amplitude depends on the mass of the CDO, and its frequency is typically in the range 3-5 kHz as determined by the central density of the star. In the best cases, LIGO may be sensitive to CDO masses greater than or of order $10^{-8}$ solar masses.
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Submitted 12 February, 2019;
originally announced February 2019.
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Particle motion and scattering in Finslerian Schwarzschild metric
Authors:
V. Sai sumith Reddy
Abstract:
Finsler geometry is just riemannian geometry without the quadratic restriction[1]. In this paper, we study the motion of massive(non-zero rest mass) and massless particles for schwarzschild metric in finsler spacetime in the case of two dimensional Randers-Finsler space with unit positive flag curvature instead of two dimensional riemann sphere. We provide qualitative study of potential energy of…
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Finsler geometry is just riemannian geometry without the quadratic restriction[1]. In this paper, we study the motion of massive(non-zero rest mass) and massless particles for schwarzschild metric in finsler spacetime in the case of two dimensional Randers-Finsler space with unit positive flag curvature instead of two dimensional riemann sphere. We provide qualitative study of potential energy of particles at various distances near schwarzschild black hole and the results are then compared with schwarzschild metric in riemannian geometry. We will also describe the scattering of particles near schwarzschild black hole in finsler spacetime by finding capture cross section of absorption by the black hole.
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Submitted 3 January, 2018;
originally announced January 2018.