Pub Date : 2026-02-05DOI: 10.1088/1475-7516/2026/02/011
Yan-Heng Yu, Zhe Chang and Sai Wang
Dissipation is an intrinsic property of the cosmic fluid, leading to the damping of curvature perturbations at small scales. In this paper, we comprehensively study dissipative effects in gravitational waves induced by curvature perturbations, known as induced gravitational waves (IGWs). We find dissipative effects become especially significant at wavenumber k ∼ kℋ,dec where kℋ,dec corresponds to the horizon scale at the decoupling of weakly-interacting particles. They can leave characteristic features on the IGW spectrum, including a notable suppression with a “double-valley” structure at k ≲ kℋ,dec and a modified infrared behavior without logarithmic running at k ≲ k_ℋ,dec. Within the Standard Model of particle physics, dissipative effects caused by neutrinos at the nanohertz frequencies can be important in the analysis of pulsar timing array data. Furthermore, dissipation-induced features associated with possible new weakly-interacting particles can be detectable by a wide range of gravitational-wave experiments, serving as a promising probe of new physics at extremely high energy scales. As an extension, we also discuss dissipative effects in the presence of primordial non-Gaussianity and their impacts on the anisotropies of IGWs and the poltergeist mechanism. These dissipative effects not only provide a more realistic description of IGWs but also exhibit rich phenomenology and profound physical implications, opening a new window into understanding the early Universe and fundamental physics.
耗散是宇宙流体的固有特性，导致小尺度曲率扰动的衰减。本文全面研究了曲率扰动诱导引力波中的耗散效应，即诱导引力波。我们发现耗散效应在波数k ~ k h时变得特别显著，其中k h对应于弱相互作用粒子解耦时的视界尺度。它们可以在IGW光谱上留下一些特征，包括在k > k h h h处具有明显的“双谷”结构的抑制，以及在k > k h h h h h处没有对数运行的改进的红外行为。在粒子物理的标准模型中，由纳赫兹频率的中微子引起的耗散效应在脉冲星定时阵列数据的分析中是重要的。此外，耗散诱导的特征与可能的新弱相互作用粒子相关，可以通过广泛的引力波实验检测到，作为在极高能量尺度上的新物理的有希望的探针。作为扩展，我们还讨论了原始非高斯性存在下的耗散效应及其对igw各向异性的影响和鬼扰机制。这些耗散效应不仅提供了对igw更为真实的描述，而且展现了丰富的现象学和深刻的物理含义，为理解早期宇宙和基础物理学打开了一扇新的窗口。
{"title":"Comprehensive analysis of dissipative effects in the induced gravitational waves","authors":"Yan-Heng Yu, Zhe Chang and Sai Wang","doi":"10.1088/1475-7516/2026/02/011","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/011","url":null,"abstract":"Dissipation is an intrinsic property of the cosmic fluid, leading to the damping of curvature perturbations at small scales. In this paper, we comprehensively study dissipative effects in gravitational waves induced by curvature perturbations, known as induced gravitational waves (IGWs). We find dissipative effects become especially significant at wavenumber k ∼ kℋ,dec where kℋ,dec corresponds to the horizon scale at the decoupling of weakly-interacting particles. They can leave characteristic features on the IGW spectrum, including a notable suppression with a “double-valley” structure at k ≲ kℋ,dec and a modified infrared behavior without logarithmic running at k ≲ k_ℋ,dec. Within the Standard Model of particle physics, dissipative effects caused by neutrinos at the nanohertz frequencies can be important in the analysis of pulsar timing array data. Furthermore, dissipation-induced features associated with possible new weakly-interacting particles can be detectable by a wide range of gravitational-wave experiments, serving as a promising probe of new physics at extremely high energy scales. As an extension, we also discuss dissipative effects in the presence of primordial non-Gaussianity and their impacts on the anisotropies of IGWs and the poltergeist mechanism. These dissipative effects not only provide a more realistic description of IGWs but also exhibit rich phenomenology and profound physical implications, opening a new window into understanding the early Universe and fundamental physics.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"217 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146121939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-04DOI: 10.1088/1475-7516/2026/02/010
Nicolás Bernal, Sagnik Mukherjee and James Unwin
If the dark matter mass m exceeds the maximum temperature of the Universe (Tmax < m) then its production rate will be Boltzmann suppressed. The important implications of this Boltzmann suppression have been explored for dark matter freeze-in via renormalizable operators. Here we extend these considerations to the case of ultraviolet (UV) freeze-in for which freeze-in proceeds via non-renormalizable operators. The UV freeze-in variant has a number of appealing features, not least that a given effective field theory can describe a multitude of UV completions, and thus such analyses are model agnostic for a given high dimension freeze-in operator. We undertake model independent analyses of UV freeze-in for portal operators of general mass dimensions. Subsequently, we explore a number of specific examples, namely, Higgs portals, bino dark matter, and gravitino dark matter. Finally, we discuss how significant differences arise if one departs from the standard assumptions regarding inflationary reheating (i.e. transitions from an early matter dominated era to radiation domination). As a motivated example we examine the implications of early kination domination. Boltzmann suppressed UV freeze-in is well motivated and permits a number of compelling scenarios. In particular, we highlight that for Tmax ∼ 1 TeV it is feasible that the freeze-in mechanism is entirely realized within a couple of orders of magnitude of the TeV scale, making it experimentally accessible in contrast to traditional freeze-in scenarios.
{"title":"Boltzmann suppressed ultraviolet freeze-in","authors":"Nicolás Bernal, Sagnik Mukherjee and James Unwin","doi":"10.1088/1475-7516/2026/02/010","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/010","url":null,"abstract":"If the dark matter mass m exceeds the maximum temperature of the Universe (Tmax < m) then its production rate will be Boltzmann suppressed. The important implications of this Boltzmann suppression have been explored for dark matter freeze-in via renormalizable operators. Here we extend these considerations to the case of ultraviolet (UV) freeze-in for which freeze-in proceeds via non-renormalizable operators. The UV freeze-in variant has a number of appealing features, not least that a given effective field theory can describe a multitude of UV completions, and thus such analyses are model agnostic for a given high dimension freeze-in operator. We undertake model independent analyses of UV freeze-in for portal operators of general mass dimensions. Subsequently, we explore a number of specific examples, namely, Higgs portals, bino dark matter, and gravitino dark matter. Finally, we discuss how significant differences arise if one departs from the standard assumptions regarding inflationary reheating (i.e. transitions from an early matter dominated era to radiation domination). As a motivated example we examine the implications of early kination domination. Boltzmann suppressed UV freeze-in is well motivated and permits a number of compelling scenarios. In particular, we highlight that for Tmax ∼ 1 TeV it is feasible that the freeze-in mechanism is entirely realized within a couple of orders of magnitude of the TeV scale, making it experimentally accessible in contrast to traditional freeze-in scenarios.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"159 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146115744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-04DOI: 10.1088/1475-7516/2026/02/009
Haipeng An, Shuailiang Ge, Jia Liu and Zhiyao Lu
In this study, we propose an investigation into dark photon dark matter (DPDM) within the infrared frequency band, utilizing highly sensitive infrared light detectors commonly integrated into space telescopes, such as the James Webb Space Telescope (JWST). The presence of DPDM induces electron oscillations in both the reflectors and the interior of the detectors. Consequently, these oscillating electrons can emit monochromatic electromagnetic waves with a frequency almost equivalent to the mass of DPDM. By employing the stationary phase approximation, we can demonstrate that when the size of the reflector significantly exceeds the wavelength of the electromagnetic wave, the contribution to the electromagnetic wave field at a given position primarily stems from the surface unit perpendicular to the relative position vector. This simplification results in the reduction of electromagnetic wave calculations to ray optics. Through a careful analysis of photon generation induced by DPDM on the various optical elements of JWST, we find that the contribution of these photons to the detected signal is negligible. Nevertheless, we propose a modified configuration of the JWST mirrors that would enable the DPDM-induced photons to be focused onto the detector. This approach can be applied to future space telescopes during their ground-testing phases. Using the JWST parameters as a representative example, the achievable upper limits on the DPDM-photon mixing constant are ϵ ∼ 10-12–10-14 in the frequency range 10–500 THz at the 95% confidence level. This reveals the strong potential of future space telescopes for DPDM detection during ground testing, with sensitivities exceeding current limits by 1 to 2 orders of magnitude compared with the XENON1T result and the solar cooling bound.
{"title":"Direct detection of dark photon dark matter with the James Webb Space Telescope","authors":"Haipeng An, Shuailiang Ge, Jia Liu and Zhiyao Lu","doi":"10.1088/1475-7516/2026/02/009","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/009","url":null,"abstract":"In this study, we propose an investigation into dark photon dark matter (DPDM) within the infrared frequency band, utilizing highly sensitive infrared light detectors commonly integrated into space telescopes, such as the James Webb Space Telescope (JWST). The presence of DPDM induces electron oscillations in both the reflectors and the interior of the detectors. Consequently, these oscillating electrons can emit monochromatic electromagnetic waves with a frequency almost equivalent to the mass of DPDM. By employing the stationary phase approximation, we can demonstrate that when the size of the reflector significantly exceeds the wavelength of the electromagnetic wave, the contribution to the electromagnetic wave field at a given position primarily stems from the surface unit perpendicular to the relative position vector. This simplification results in the reduction of electromagnetic wave calculations to ray optics. Through a careful analysis of photon generation induced by DPDM on the various optical elements of JWST, we find that the contribution of these photons to the detected signal is negligible. Nevertheless, we propose a modified configuration of the JWST mirrors that would enable the DPDM-induced photons to be focused onto the detector. This approach can be applied to future space telescopes during their ground-testing phases. Using the JWST parameters as a representative example, the achievable upper limits on the DPDM-photon mixing constant are ϵ ∼ 10-12–10-14 in the frequency range 10–500 THz at the 95% confidence level. This reveals the strong potential of future space telescopes for DPDM detection during ground testing, with sensitivities exceeding current limits by 1 to 2 orders of magnitude compared with the XENON1T result and the solar cooling bound.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"75 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146115739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-02DOI: 10.1088/1475-7516/2026/02/002
Itzi Aldecoa-Tamayo, Christian T. Byrnes and David Seery
We reconsider primordial black hole physics in Randall-Sundrum Type-II universes, focusing on constraints from cosmological and astrophysical observables. We pay particular attention to scenarios that allow the entirety of dark matter to be in the form of higher-dimensional primordial black holes. This is possible for a range of AdS radii and black hole masses. Observable constraints are generally modified due to the changes in the higher-dimensional gravitational sector, and come from low-energy e± emission, microlensing, and possibly from contributions to unresolved radiation backgrounds. We discuss constraints from the cosmic microwave background due to injection of Hawking quanta into the intergalactic medium. Finally, we comment on recent discussions on the compatibility of higher-dimensional black holes and the KM3-230213A event.
{"title":"Primordial black holes in Randall-Sundrum: cosmological signatures","authors":"Itzi Aldecoa-Tamayo, Christian T. Byrnes and David Seery","doi":"10.1088/1475-7516/2026/02/002","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/002","url":null,"abstract":"We reconsider primordial black hole physics in Randall-Sundrum Type-II universes, focusing on constraints from cosmological and astrophysical observables. We pay particular attention to scenarios that allow the entirety of dark matter to be in the form of higher-dimensional primordial black holes. This is possible for a range of AdS radii and black hole masses. Observable constraints are generally modified due to the changes in the higher-dimensional gravitational sector, and come from low-energy e± emission, microlensing, and possibly from contributions to unresolved radiation backgrounds. We discuss constraints from the cosmic microwave background due to injection of Hawking quanta into the intergalactic medium. Finally, we comment on recent discussions on the compatibility of higher-dimensional black holes and the KM3-230213A event.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"91 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146098033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-02DOI: 10.1088/1475-7516/2026/02/001
Andrea Lapi, Francesco Shankar, Michele Bosi, Daniel Roberts, Hao Fu, Karthik M. Varadarajan and Lumen Boco
The evolution of the supermassive Black Hole (BH) population across cosmic times remains a central unresolved issue in modern astrophysics, due to the many noticeable uncertainties in the involved physical processes that span a huge range of spatial, temporal and energy scales. Here we tackle the problem via a semi-empirical approach with minimal assumptions and data-driven inputs. This is based on a continuity plus Smoluchowski equation framework that allows to unitarily describe the two primary modes of BH growth: gas accretion and binary mergers. Key quantities related to the latter processes are incorporated through educated parameterizations, and then constrained in a Bayesian setup from joint observational estimates of the local BH mass function, of the large-scale BH clustering, and of the nano-Hz stochastic gravitational wave (GW) background measured from Pulsar Timimg Array (PTA) experiments. We find that the BH accretion-related parameters are strongly dependent on the local BH mass function determination: higher normalizations and flatter high-mass slopes in the latter imply lower radiative efficiencies and mean Eddington ratios with a stronger redshift evolution. Additionally, the binary BH merger rate is estimated to be a fraction ≲ 10-1 of the galaxy merger rate derived from galaxy pairs counts by JWST, and constrained not to exceed the latter at ≳ 2σ. Relatedly, we highlight hints of a possible tension between current constraints on BH demographics and the interpretation of the nano-Hz GW background as predominantly caused by binary BH mergers. Specifically, we bound the latter's contribution to ≲ 30-50% at ∼ 3σ, suggesting that either systematics in the datasets considered here have been underestimated so far, or that additional astrophysical/cosmological sources are needed to explain the residual part of the signal measured by PTA experiments.
{"title":"Semi-empirical framework of supermassive black hole evolution: highlighting a possible tension between demographics and gravitational wave background","authors":"Andrea Lapi, Francesco Shankar, Michele Bosi, Daniel Roberts, Hao Fu, Karthik M. Varadarajan and Lumen Boco","doi":"10.1088/1475-7516/2026/02/001","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/001","url":null,"abstract":"The evolution of the supermassive Black Hole (BH) population across cosmic times remains a central unresolved issue in modern astrophysics, due to the many noticeable uncertainties in the involved physical processes that span a huge range of spatial, temporal and energy scales. Here we tackle the problem via a semi-empirical approach with minimal assumptions and data-driven inputs. This is based on a continuity plus Smoluchowski equation framework that allows to unitarily describe the two primary modes of BH growth: gas accretion and binary mergers. Key quantities related to the latter processes are incorporated through educated parameterizations, and then constrained in a Bayesian setup from joint observational estimates of the local BH mass function, of the large-scale BH clustering, and of the nano-Hz stochastic gravitational wave (GW) background measured from Pulsar Timimg Array (PTA) experiments. We find that the BH accretion-related parameters are strongly dependent on the local BH mass function determination: higher normalizations and flatter high-mass slopes in the latter imply lower radiative efficiencies and mean Eddington ratios with a stronger redshift evolution. Additionally, the binary BH merger rate is estimated to be a fraction ≲ 10-1 of the galaxy merger rate derived from galaxy pairs counts by JWST, and constrained not to exceed the latter at ≳ 2σ. Relatedly, we highlight hints of a possible tension between current constraints on BH demographics and the interpretation of the nano-Hz GW background as predominantly caused by binary BH mergers. Specifically, we bound the latter's contribution to ≲ 30-50% at ∼ 3σ, suggesting that either systematics in the datasets considered here have been underestimated so far, or that additional astrophysical/cosmological sources are needed to explain the residual part of the signal measured by PTA experiments.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"5 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146098032","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-30DOI: 10.1088/1475-7516/2026/01/064
Paolo Creminelli, Sébastien Renaux-Petel, Giovanni Tambalo and Vicharit Yingcharoenrat
We investigate a qualitatively new regime of inflationary models with small and rapid oscillations in the potential — resonant non-Gaussianity. In contrast to the standard scenario, where most of the observable information is encoded in the power spectrum, in this regime the oscillatory signal predominantly appears in higher-order correlation functions with large n. This behavior emerges when the oscillation frequency ω exceeds the naive cutoff of the theory, 4π f. However, as noted by Hook and Rattazzi [1], the actual cutoff is somewhat higher — though only logarithmically — when the amplitude of the oscillations is small. We identify a phenomenologically relevant window in which n-point functions with 3 ≲ n ≲ 9 are potentially observable. In this regime, the signal exhibits 350–1000 oscillations per decade in k.
{"title":"Large n-point functions in resonant inflation","authors":"Paolo Creminelli, Sébastien Renaux-Petel, Giovanni Tambalo and Vicharit Yingcharoenrat","doi":"10.1088/1475-7516/2026/01/064","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/064","url":null,"abstract":"We investigate a qualitatively new regime of inflationary models with small and rapid oscillations in the potential — resonant non-Gaussianity. In contrast to the standard scenario, where most of the observable information is encoded in the power spectrum, in this regime the oscillatory signal predominantly appears in higher-order correlation functions with large n. This behavior emerges when the oscillation frequency ω exceeds the naive cutoff of the theory, 4π f. However, as noted by Hook and Rattazzi [1], the actual cutoff is somewhat higher — though only logarithmically — when the amplitude of the oscillations is small. We identify a phenomenologically relevant window in which n-point functions with 3 ≲ n ≲ 9 are potentially observable. In this regime, the signal exhibits 350–1000 oscillations per decade in k.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"93 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146071995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1088/1475-7516/2026/01/062
Sêcloka L. Guedezounme, Bikash R. Dinda and Roy Maartens
Recent results from DESI BAO measurements, together with Planck CMB and Pantheon+ data, suggest that there may be a 'phantom' phase (wde < -1) in the expansion of the Universe. This inference follows when the w0, wa parametrization for the dark energy equation of state wde is used to fit the data. Since phantom dark energy in general relativity is unphysical, we investigate the possibility that the phantom behaviour is not intrinsic, but effective — due to a non-gravitational interaction between dark matter and non-phantom dark energy. To this end, we assume a physically motivated thawing quintessence-like form of the intrinsic dark energy equation of state wde. Then we use a w0, wa model for the effective equation of state of dark energy. We find that the data favours a phantom crossing for the effective dark energy, but only at low significance. The intrinsic equation of state of dark energy is non-phantom, without imposing any non-phantom priors. A nonzero interaction is favoured at more than 3σ at z ∼ 0.3. The energy flows from dark matter to dark energy at early times and reverses at later times.
{"title":"Phantom crossing or dark interaction?","authors":"Sêcloka L. Guedezounme, Bikash R. Dinda and Roy Maartens","doi":"10.1088/1475-7516/2026/01/062","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/062","url":null,"abstract":"Recent results from DESI BAO measurements, together with Planck CMB and Pantheon+ data, suggest that there may be a 'phantom' phase (wde < -1) in the expansion of the Universe. This inference follows when the w0, wa parametrization for the dark energy equation of state wde is used to fit the data. Since phantom dark energy in general relativity is unphysical, we investigate the possibility that the phantom behaviour is not intrinsic, but effective — due to a non-gravitational interaction between dark matter and non-phantom dark energy. To this end, we assume a physically motivated thawing quintessence-like form of the intrinsic dark energy equation of state wde. Then we use a w0, wa model for the effective equation of state of dark energy. We find that the data favours a phantom crossing for the effective dark energy, but only at low significance. The intrinsic equation of state of dark energy is non-phantom, without imposing any non-phantom priors. A nonzero interaction is favoured at more than 3σ at z ∼ 0.3. The energy flows from dark matter to dark energy at early times and reverses at later times.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"78 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146070525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1088/1475-7516/2026/01/063
J.R. Espinosa and T. Konstandin
In the standard lore the decay of the false vacuum of a single-field potential is described by a semi-classical Euclidean bounce configuration that can be found using overshoot/undershoot algorithms, and whose action suppresses exponentially the decay rate. While this is generically correct, we show in a few concrete examples of potentials, previously studied in the literature for other purposes, that the vacuum decay structure can be far richer. In some cases there is no bounce and decay proceeds via the so-called pseudo-bounce configurations. In the general case with bounce, there are 2n+1 bounces, with n ranging from 0 (the standard case) to ∞. Some of these decay configurations we call antibounces as they have the wrong behavior for overshoot/undershoot algorithms, which can miss them. Bounce and antibounce configurations form n pairs connected by pseudo-bounces. Our analysis benefits from a combined use of Euclidean and tunneling potential methods.
{"title":"An exploration of vacuum-decay valleys","authors":"J.R. Espinosa and T. Konstandin","doi":"10.1088/1475-7516/2026/01/063","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/063","url":null,"abstract":"In the standard lore the decay of the false vacuum of a single-field potential is described by a semi-classical Euclidean bounce configuration that can be found using overshoot/undershoot algorithms, and whose action suppresses exponentially the decay rate. While this is generically correct, we show in a few concrete examples of potentials, previously studied in the literature for other purposes, that the vacuum decay structure can be far richer. In some cases there is no bounce and decay proceeds via the so-called pseudo-bounce configurations. In the general case with bounce, there are 2n+1 bounces, with n ranging from 0 (the standard case) to ∞. Some of these decay configurations we call antibounces as they have the wrong behavior for overshoot/undershoot algorithms, which can miss them. Bounce and antibounce configurations form n pairs connected by pseudo-bounces. Our analysis benefits from a combined use of Euclidean and tunneling potential methods.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"86 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146070526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-28DOI: 10.1088/1475-7516/2026/01/056
Raphaël Picard, Luis E. Padilla, Karim A. Malik and David J. Mulryne
In this work, we revisit and evaluate new source terms which contribute to the induced gravitational wave background. We study their respective contributions to the stochastic gravitational wave background by computing their spectral densities in a radiation-dominated universe. These terms appear at third order in cosmological perturbation theory, however, their correlations with primordial gravitational waves are non-trivial and appear at the same order as so-called scalar induced and scalar-tensor induced gravitational waves. We find that these gravitational wave sources suppress the spectral density at the scales we consider. Furthermore, similarly to scalar-tensor source terms at second order, we find that some terms are enhanced when the input primordial power spectrum of scalar fluctuations is not sufficiently peaked. Hence, where possible, we show that under certain limits the integrands of these terms diverge in the UV sector.
{"title":"Suppression of the induced gravitational wave background due to third-order perturbations","authors":"Raphaël Picard, Luis E. Padilla, Karim A. Malik and David J. Mulryne","doi":"10.1088/1475-7516/2026/01/056","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/056","url":null,"abstract":"In this work, we revisit and evaluate new source terms which contribute to the induced gravitational wave background. We study their respective contributions to the stochastic gravitational wave background by computing their spectral densities in a radiation-dominated universe. These terms appear at third order in cosmological perturbation theory, however, their correlations with primordial gravitational waves are non-trivial and appear at the same order as so-called scalar induced and scalar-tensor induced gravitational waves. We find that these gravitational wave sources suppress the spectral density at the scales we consider. Furthermore, similarly to scalar-tensor source terms at second order, we find that some terms are enhanced when the input primordial power spectrum of scalar fluctuations is not sufficiently peaked. Hence, where possible, we show that under certain limits the integrands of these terms diverge in the UV sector.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"30 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146057070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-28DOI: 10.1088/1475-7516/2026/01/059
Soroush Zare, Tao Zhu, Luis M. Nieto, Shuo Lu and Hassan Hassanabadi
Extreme mass-ratio inspirals (EMRIs) are among the key targets for future space-based gravitational wave detectors. The gravitational waveforms emitted by EMRIs are highly sensitive to the orbital dynamics of the small compact object, which in turn are determined by the geometry of the underlying spacetime. In this paper, we explore the detectability of regular black holes with sub-Planckian curvature, which can be interpreted as regularized versions of the Schwarzschild black hole (RSBH). To do so, we begin by analyzing the metric and geodesics, determining the effective potential, and investigating the marginally bound orbits and the innermost stable circular orbits for timelike particles. Our analysis reveals that orbital radius, angular momentum, and energy significantly depend on the model parameter α for both orbits. In addition, we study how variations in α influence the photon sphere and the corresponding shadow silhouette. Observations of M87* and Sgr A* motivate testing whether α falls within an observationally constrained range, narrower than the theoretical bound ensuring a singularity-free BH structure. Our main aim is to focus on the influence of the model parameter on a specific kind of orbit, the periodic orbit, surrounding a supermassive RSBH. The findings show that, for a constant rational integer, α has a significant impact on the energy and angular momentum of the periodic orbit. Utilising the numerical kludge method, we further investigate the gravitational waveforms of the small celestial body over various periodic orbits. The waveforms display discrete zoom and spin phases within a complete orbital period, influenced by the RSBH parameter α. As the system evolves, the phase shift in the gravitational waveforms grows progressively more pronounced, with cumulative deviations amplifying over time. With the ongoing advancements in space-based gravitational wave detection systems, our results will aid in leveraging EMRIs to probe and characterize the RSBH properties.
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