Marcus V. Bomfim, Emmanuel Frion, Nelson Pinto-Neto, Sandro D. P. Vitenti
We investigate primordial magnetogenesis within a quantum bouncing model driven by a scalar field, focusing on various non-minimal couplings between the electromagnetic field and the scalar field. We test three cases: no coupling, a Cauchy coupling with gradual decay, and a Gaussian coupling with rapid fall-off. By exploring these scenarios, we assess a wide range of coupling strengths across different scales. The scalar field, with an exponential potential, behaves as pressureless matter in the asymptotic past of the contracting phase, as stiff matter around the bounce, and as dark energy during the expanding phase. Our findings reveal that, among the tested cases, only the Gaussian coupling can explain the generation of primordial magnetic fields on cosmological scales.
{"title":"Primordial magnetogenesis in a bouncing model with dark energy","authors":"Marcus V. Bomfim, Emmanuel Frion, Nelson Pinto-Neto, Sandro D. P. Vitenti","doi":"arxiv-2409.05329","DOIUrl":"https://doi.org/arxiv-2409.05329","url":null,"abstract":"We investigate primordial magnetogenesis within a quantum bouncing model\u0000driven by a scalar field, focusing on various non-minimal couplings between the\u0000electromagnetic field and the scalar field. We test three cases: no coupling, a\u0000Cauchy coupling with gradual decay, and a Gaussian coupling with rapid\u0000fall-off. By exploring these scenarios, we assess a wide range of coupling\u0000strengths across different scales. The scalar field, with an exponential\u0000potential, behaves as pressureless matter in the asymptotic past of the\u0000contracting phase, as stiff matter around the bounce, and as dark energy during\u0000the expanding phase. Our findings reveal that, among the tested cases, only the\u0000Gaussian coupling can explain the generation of primordial magnetic fields on\u0000cosmological scales.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thomas F. M. Spieksma, Vitor Cardoso, Gregorio Carullo, Matteo Della Rocca, Francisco Duque
The ringdown phase following a binary black hole coalescence is a powerful tool for measuring properties of the remnant black hole. Future gravitational wave detectors will increase the precision of these measurements and may be sensitive to the environment surrounding the black hole. This work examines how environments affect the ringdown from a binary coalescence. Our analysis shows that for astrophysical parameters and sensitivity of planned detectors, the ringdown signal is indistinguishable from its vacuum counterpart, suggesting that ringdown-only analyses can reliably extract the (redshifted) mass and spin of the remnant black hole. These conclusions include models with spectral instabilities, suggesting that these are not relevant from an observational viewpoint. Deviations from inspiral-only estimates could then enhance the characterisation of environmental effects present during the coalescence.
{"title":"Black hole spectroscopy in environments: detectability prospects","authors":"Thomas F. M. Spieksma, Vitor Cardoso, Gregorio Carullo, Matteo Della Rocca, Francisco Duque","doi":"arxiv-2409.05950","DOIUrl":"https://doi.org/arxiv-2409.05950","url":null,"abstract":"The ringdown phase following a binary black hole coalescence is a powerful\u0000tool for measuring properties of the remnant black hole. Future gravitational\u0000wave detectors will increase the precision of these measurements and may be\u0000sensitive to the environment surrounding the black hole. This work examines how\u0000environments affect the ringdown from a binary coalescence. Our analysis shows\u0000that for astrophysical parameters and sensitivity of planned detectors, the\u0000ringdown signal is indistinguishable from its vacuum counterpart, suggesting\u0000that ringdown-only analyses can reliably extract the (redshifted) mass and spin\u0000of the remnant black hole. These conclusions include models with spectral\u0000instabilities, suggesting that these are not relevant from an observational\u0000viewpoint. Deviations from inspiral-only estimates could then enhance the\u0000characterisation of environmental effects present during the coalescence.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We perform an observational study of modified gravity considering a potential inflationary interpretation of pulsar timing arrays (PTA). We use a motivated model known as no slip in which the gravitational wave propagation is modified. Specifically, by using two different parametrizations for the model, we find the approximate transfer functions for tensor perturbations. In this way, we obtain the spectral energy density of gravitational waves and use NANOGrav and IPTA second data release to constrain parameters of the model. We find that there is degeneracy between the model parameters $xi$ and $c_M$. For $c_M$, we only get an upper bound on the parameter. Thus, it is difficult to constrain them with percent level accuracy with the current PTA data.
{"title":"Testing No slip model with pulsar timing arrays: NANOGrav and IPTA","authors":"Mohammadreza Davari, Alireza Allahyari, Shahram Khosravi","doi":"arxiv-2409.05956","DOIUrl":"https://doi.org/arxiv-2409.05956","url":null,"abstract":"We perform an observational study of modified gravity considering a potential\u0000inflationary interpretation of pulsar timing arrays (PTA). We use a motivated\u0000model known as no slip in which the gravitational wave propagation is modified.\u0000Specifically, by using two different parametrizations for the model, we find\u0000the approximate transfer functions for tensor perturbations. In this way, we\u0000obtain the spectral energy density of gravitational waves and use NANOGrav and\u0000IPTA second data release to constrain parameters of the model. We find that\u0000there is degeneracy between the model parameters $xi$ and $c_M$. For $c_M$, we\u0000only get an upper bound on the parameter. Thus, it is difficult to constrain\u0000them with percent level accuracy with the current PTA data.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. M. Becerra, F. Cipolletta, C. L. Fryer, Débora P. Menezes, Constança Providência, J. A. Rueda, R. Ruffini
The binary-driven hypernova (BdHN) model proposes long gamma-ray bursts (GRBs) originate in binaries composed of a carbon-oxygen (CO) star and a neutron star (NS) companion. The CO core collapse generates a newborn NS and a supernova that triggers the GRB by accreting onto the NSs, rapidly transferring mass and angular momentum to them. We perform three-dimensional, smoothed-particle-hydrodynamics simulations of BdHNe using up-to-date NS nuclear equations of state (EOS), with and without hyperons, and calculate the structure evolution in full general relativity. We assess the binary parameters leading either NS to the critical mass for gravitational collapse into a black hole (BH) and its occurrence time, $t_textrm{col}$. We include a non-zero angular momentum of the NSs and find that $t_textrm{col}$ ranges from a few tens of seconds to hours for decreasing NS initial angular momentum values. BdHNe I are the most compact (about five minutes orbital period), promptly form a BH and release $gtrsim 10^{52}$ erg. They form NS-BH binaries with tens of kyr merger timescale by gravitational-wave emission. BdHNe II and III do not form BHs, release $sim 10^{50}$-$10^{52}$ erg and $lesssim 10^{50}$ erg. They form NS-NS with a wider range of merger timescales. In some compact BdHNe II, either NS can become supramassive, i.e., above the critical mass of a non-rotating NS. Magnetic braking by a $10^{13}$ G field can delay BH formation, leading to BH-BH or NS-BH of tens of kyr merger timescale.
{"title":"Occurrence of gravitational collapse in the accreting neutron stars of binary-driven hypernovae","authors":"L. M. Becerra, F. Cipolletta, C. L. Fryer, Débora P. Menezes, Constança Providência, J. A. Rueda, R. Ruffini","doi":"arxiv-2409.05767","DOIUrl":"https://doi.org/arxiv-2409.05767","url":null,"abstract":"The binary-driven hypernova (BdHN) model proposes long gamma-ray bursts\u0000(GRBs) originate in binaries composed of a carbon-oxygen (CO) star and a\u0000neutron star (NS) companion. The CO core collapse generates a newborn NS and a\u0000supernova that triggers the GRB by accreting onto the NSs, rapidly transferring\u0000mass and angular momentum to them. We perform three-dimensional,\u0000smoothed-particle-hydrodynamics simulations of BdHNe using up-to-date NS\u0000nuclear equations of state (EOS), with and without hyperons, and calculate the\u0000structure evolution in full general relativity. We assess the binary parameters\u0000leading either NS to the critical mass for gravitational collapse into a black\u0000hole (BH) and its occurrence time, $t_textrm{col}$. We include a non-zero\u0000angular momentum of the NSs and find that $t_textrm{col}$ ranges from a few\u0000tens of seconds to hours for decreasing NS initial angular momentum values.\u0000BdHNe I are the most compact (about five minutes orbital period), promptly form\u0000a BH and release $gtrsim 10^{52}$ erg. They form NS-BH binaries with tens of\u0000kyr merger timescale by gravitational-wave emission. BdHNe II and III do not\u0000form BHs, release $sim 10^{50}$-$10^{52}$ erg and $lesssim 10^{50}$ erg. They\u0000form NS-NS with a wider range of merger timescales. In some compact BdHNe II,\u0000either NS can become supramassive, i.e., above the critical mass of a\u0000non-rotating NS. Magnetic braking by a $10^{13}$ G field can delay BH\u0000formation, leading to BH-BH or NS-BH of tens of kyr merger timescale.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"165 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Andronikos Paliathanasis, Kevin Duffy, Amlan Halder, Amare Abebe
We revise the cosmological interaction between dark energy and dark matter. More precisely, we focus on models that support compartmentalization or co-existence in the dark sector of the universe. Within the framework of a homogeneous and isotropic, spatially flat Friedmann--Lema^itre--Robertson--Walker geometry, we analyse the asymptotic behaviour of the physical parameters for two interacting models, where dark energy and dark matter have constant equations of state parameters, in the presence of dark radiation, when dark energy is described by a quintessence scalar field. For each model, we determine the asymptotic solutions and attempt to understand how the interaction affects the cosmological evolution and history.
{"title":"Compartmental and Coexistence in the Dark Sector of the Universe","authors":"Andronikos Paliathanasis, Kevin Duffy, Amlan Halder, Amare Abebe","doi":"arxiv-2409.05348","DOIUrl":"https://doi.org/arxiv-2409.05348","url":null,"abstract":"We revise the cosmological interaction between dark energy and dark matter.\u0000More precisely, we focus on models that support compartmentalization or\u0000co-existence in the dark sector of the universe. Within the framework of a\u0000homogeneous and isotropic, spatially flat\u0000Friedmann--Lema^itre--Robertson--Walker geometry, we analyse the asymptotic\u0000behaviour of the physical parameters for two interacting models, where dark\u0000energy and dark matter have constant equations of state parameters, in the\u0000presence of dark radiation, when dark energy is described by a quintessence\u0000scalar field. For each model, we determine the asymptotic solutions and attempt\u0000to understand how the interaction affects the cosmological evolution and\u0000history.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"128 2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) black hole with a magnetic charge (or an electric charge) has noteworthy features that its scalar curvature near the event horizon of the black hole with the almost maximal charge can be extremely large. The large curvature, which is related with the gravity on a finite-sized object or between two points, causes high center-of-mass energy for two neutral particles near the almost maximally charged GMGHS black hole. Recently, the Event Horizon Telescope Collaboration gave the bound on the charge of black holes from the shadow and mass observations of black holes under an assumption that the diameter of observed rings are proportion to that of photon spheres. The photon sphere would be less related with the curvature, since it is determined by the behavior of one photon or one ray neither two photons nor two rays. Thus, the high-energy neutral particle collision and the black hole shadow observations would be complementary to distinguish the GMGHS black hole from other black hole solutions. In this paper, we investigate a new way to compare the center-of-mass energy for neutral particle collisions in the GMGHS spacetime and other black hole spacetimes. From the shadow observations and the mass observations under the assumptions on the effect of black hole charges, we can put constraints on the center-of-mass energy of the particles. We apply our method to shadow and mass observations of M87* and Sagittarius~A*. We find that the center-of-mass energy of neutral particles near the GMGHS black holes cannot be extremely large under the observational constraints, and conclude that the GMGHS spacetimes are hardly distinguishable from the Reissner-Nordstr"{o}m spacetimes by the particle collisions if we apply the shadow and mass observations at $1 sigma$ probability.
{"title":"Neutral particle collisions near Gibbons-Maeda-Garfinkle-Horowitz-Strominger black holes after shadow observations","authors":"Naoki Tsukamoto, Ryotaro Kase","doi":"arxiv-2409.04990","DOIUrl":"https://doi.org/arxiv-2409.04990","url":null,"abstract":"A Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) black hole with a\u0000magnetic charge (or an electric charge) has noteworthy features that its scalar\u0000curvature near the event horizon of the black hole with the almost maximal\u0000charge can be extremely large. The large curvature, which is related with the\u0000gravity on a finite-sized object or between two points, causes high\u0000center-of-mass energy for two neutral particles near the almost maximally\u0000charged GMGHS black hole. Recently, the Event Horizon Telescope Collaboration\u0000gave the bound on the charge of black holes from the shadow and mass\u0000observations of black holes under an assumption that the diameter of observed\u0000rings are proportion to that of photon spheres. The photon sphere would be less\u0000related with the curvature, since it is determined by the behavior of one\u0000photon or one ray neither two photons nor two rays. Thus, the high-energy\u0000neutral particle collision and the black hole shadow observations would be\u0000complementary to distinguish the GMGHS black hole from other black hole\u0000solutions. In this paper, we investigate a new way to compare the\u0000center-of-mass energy for neutral particle collisions in the GMGHS spacetime\u0000and other black hole spacetimes. From the shadow observations and the mass\u0000observations under the assumptions on the effect of black hole charges, we can\u0000put constraints on the center-of-mass energy of the particles. We apply our\u0000method to shadow and mass observations of M87* and Sagittarius~A*. We find that\u0000the center-of-mass energy of neutral particles near the GMGHS black holes\u0000cannot be extremely large under the observational constraints, and conclude\u0000that the GMGHS spacetimes are hardly distinguishable from the\u0000Reissner-Nordstr\"{o}m spacetimes by the particle collisions if we apply the\u0000shadow and mass observations at $1 sigma$ probability.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sergei D. Odintsov, Tanmoy Paul, Soumitra SenGupta
We demonstrate a deep connection between cosmology in thermodynamic description of apparent horizon and information theory. In particular, we show how the Landauer principle gets satisfied during the entire cosmic evolution of the universe starting from inflation to the late dark energy era. This in turn reveals why the matter fields are not in thermal equilibrium with the apparent horizon during most of the cosmic era of the universe, except for the fluids with $omega = -1/3$ leading to the transitions of the universe from an accelerating to a decelerating era and vice-versa.
{"title":"Landauer principle in cosmology as the link to information theory","authors":"Sergei D. Odintsov, Tanmoy Paul, Soumitra SenGupta","doi":"arxiv-2409.05009","DOIUrl":"https://doi.org/arxiv-2409.05009","url":null,"abstract":"We demonstrate a deep connection between cosmology in thermodynamic\u0000description of apparent horizon and information theory. In particular, we show\u0000how the Landauer principle gets satisfied during the entire cosmic evolution of\u0000the universe starting from inflation to the late dark energy era. This in turn\u0000reveals why the matter fields are not in thermal equilibrium with the apparent\u0000horizon during most of the cosmic era of the universe, except for the fluids\u0000with $omega = -1/3$ leading to the transitions of the universe from an\u0000accelerating to a decelerating era and vice-versa.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A gravitational wave (GW) signal carries imprints of the properties of its source. The ability to extract source properties crucially depends on our prior knowledge of the signal morphology. Even though binary black hole (BBH) mergers are the cleanest system to model in general relativity, currently, there are no waveform models which include all physical effects. This thesis focuses on three subdominant effects: orbital eccentricity, spin-precession, and non-quadrupole or higher-order modes (HMs). We study the interplay of these effects on data analysis of GW signals, highlighting the shortcomings and emphasizing the need for more advanced waveforms. For instance, we investigate whether orbital eccentricity and spin-precession can mimic each other and thus caution the GW community towards the biases that may arise due to the neglect of eccentricity and/or spins in the waveform models. Using waveforms with full spin-precession and HMs, we extend the existing spin-induced quadrupole moment (SIQM) test - a null test to distinguish BBH systems from other black hole mimickers - and show that these improved waveforms give significantly better bounds. Additionally, we quantify the parameter space where the effect of HMs is most significant and show the importance of detecting these modes in GW events for future ground-based GW detectors such as Cosmic Explorer and Einstein Telescope.
{"title":"Synergies in analysing binary black hole mergers: Effect of orbital eccentricity, spin-precession, and non-quadrupole modes","authors":"Divyajyoti","doi":"arxiv-2409.05167","DOIUrl":"https://doi.org/arxiv-2409.05167","url":null,"abstract":"A gravitational wave (GW) signal carries imprints of the properties of its\u0000source. The ability to extract source properties crucially depends on our prior\u0000knowledge of the signal morphology. Even though binary black hole (BBH) mergers\u0000are the cleanest system to model in general relativity, currently, there are no\u0000waveform models which include all physical effects. This thesis focuses on\u0000three subdominant effects: orbital eccentricity, spin-precession, and\u0000non-quadrupole or higher-order modes (HMs). We study the interplay of these\u0000effects on data analysis of GW signals, highlighting the shortcomings and\u0000emphasizing the need for more advanced waveforms. For instance, we investigate\u0000whether orbital eccentricity and spin-precession can mimic each other and thus\u0000caution the GW community towards the biases that may arise due to the neglect\u0000of eccentricity and/or spins in the waveform models. Using waveforms with full\u0000spin-precession and HMs, we extend the existing spin-induced quadrupole moment\u0000(SIQM) test - a null test to distinguish BBH systems from other black hole\u0000mimickers - and show that these improved waveforms give significantly better\u0000bounds. Additionally, we quantify the parameter space where the effect of HMs\u0000is most significant and show the importance of detecting these modes in GW\u0000events for future ground-based GW detectors such as Cosmic Explorer and\u0000Einstein Telescope.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Davide Batic, Marek Nowakowski, Neelima Govind Kelkar
We set up the Wheeler-DeWitt (WDW) equation for late gravitational collapse. The fact that the gravitational collapse and the expanding/ collapsing universe can be described within the realm of the Robertson-Walker metric renders the corresponding WDW equation for collapsing matter a timeless Schr"odinger equation. We explore the consequences of such an equation and find the density to be quantized in terms of the Planck density. Apart from that, the wave function as a solution of the WDW equation shows that the initial singularity is avoided. We concentrate on different factor orderings in the kinetic term of the equation and show how after splitting off an exponential ansatz, new polynomials entering the solution can be constructed. This enables us to conclude that the factor ordering changes the details of the solution and interpretation, but overall on a qualitative level the results remain the same. We also probe into the effects of a positive cosmological constant. It offers the possibility of a tunneling scenario at the cosmological horizon.
{"title":"Wheeler-DeWitt equation and the late gravitational collapse: effects of factor ordering and the tunneling scenario","authors":"Davide Batic, Marek Nowakowski, Neelima Govind Kelkar","doi":"arxiv-2409.05077","DOIUrl":"https://doi.org/arxiv-2409.05077","url":null,"abstract":"We set up the Wheeler-DeWitt (WDW) equation for late gravitational collapse.\u0000The fact that the gravitational collapse and the expanding/ collapsing universe\u0000can be described within the realm of the Robertson-Walker metric renders the\u0000corresponding WDW equation for collapsing matter a timeless Schr\"odinger\u0000equation. We explore the consequences of such an equation and find the density\u0000to be quantized in terms of the Planck density. Apart from that, the wave\u0000function as a solution of the WDW equation shows that the initial singularity\u0000is avoided. We concentrate on different factor orderings in the kinetic term of\u0000the equation and show how after splitting off an exponential ansatz, new\u0000polynomials entering the solution can be constructed. This enables us to\u0000conclude that the factor ordering changes the details of the solution and\u0000interpretation, but overall on a qualitative level the results remain the same.\u0000We also probe into the effects of a positive cosmological constant. It offers\u0000the possibility of a tunneling scenario at the cosmological horizon.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The dispersion measures of fast radio bursts have been identified as a powerful tool for testing the zero-mass hypothesis of the photon. The classical approach treats the massive photon-induced and plasma-induced time delays as two separate phenomena. Recently, Wang et al. (2024) suggested that the joint influence of the nonzero photon mass and plasma effects should be considered, and proposed a revised time delay for massive photons propagating in a plasma medium, denoted as $Delta t'_{m_{gamma}} propto nu^{-4}$, which departures from the classical dispersion relation ($propto nu^{-2}$). Here we discuss the derivation presented by Wang et al. (2024) and show that the classical dispersion relation remains valid based on Proca equations.
快速射电暴的频散测量被认为是检验光子零质量假说的有力工具。经典方法将大质量光子诱导的时间延迟和等离子体诱导的时间延迟视为两种不同的现象。最近，Wang 等（2024）提出应该考虑非零光子质量和等离子体效应的共同影响，并提出了一种修正的大质量光子在等离子体中传播的时间延迟，表示为 $Delta t'_{m_{gamma}}propto nu^{-4}$，它偏离了经典色散关系（$propto nu^{-2}$）。在此，我们讨论了 Wang 等人（2024 年）提出的推导，并证明基于普罗卡方程的经典弥散关系仍然有效。
{"title":"The Dispersion Relation of Massive Photons in Plasma: A Comment on \"Bounding the Photon Mass with Ultrawide Bandwidth Pulsar Timing Data and Dedispersed Pulses of Fast Radio Bursts\"","authors":"Bao Wang, Jun-Jie Wei","doi":"arxiv-2409.04672","DOIUrl":"https://doi.org/arxiv-2409.04672","url":null,"abstract":"The dispersion measures of fast radio bursts have been identified as a\u0000powerful tool for testing the zero-mass hypothesis of the photon. The classical\u0000approach treats the massive photon-induced and plasma-induced time delays as\u0000two separate phenomena. Recently, Wang et al. (2024) suggested that the joint\u0000influence of the nonzero photon mass and plasma effects should be considered,\u0000and proposed a revised time delay for massive photons propagating in a plasma\u0000medium, denoted as $Delta t'_{m_{gamma}} propto nu^{-4}$, which departures\u0000from the classical dispersion relation ($propto nu^{-2}$). Here we discuss\u0000the derivation presented by Wang et al. (2024) and show that the classical\u0000dispersion relation remains valid based on Proca equations.","PeriodicalId":501041,"journal":{"name":"arXiv - PHYS - General Relativity and Quantum Cosmology","volume":"70 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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