Pub Date : 2025-12-05DOI: 10.1088/1475-7516/2025/12/012
Boris Betancourt Kamenetskaia, Alejandro Ibarra and Chris Kouvaris
A strongly self-interacting component of asymmetric dark matter particles can form compact dark stars. The high dark matter density in these objects may allow significant dark matter annihilation into Standard Model particles, even when the portals to the visible sector are extremely weak. In this paper we argue that compact dark stars could constitute an important source of energy injection during the cosmic dawn era in addition to that of the baryonic stars. Therefore, if dark stars annihilate into photons, the luminosity of dark stars may significantly raise the gas temperature of the Universe at small redshifts. This modification to the standard thermal history of standard Cosmology would have implications for the observed 21-cm signal and the process of reionization, thus providing a new probe for particle dark matter.
{"title":"Imprints of energy injection by compact dark stars in the 21-cm signal","authors":"Boris Betancourt Kamenetskaia, Alejandro Ibarra and Chris Kouvaris","doi":"10.1088/1475-7516/2025/12/012","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/12/012","url":null,"abstract":"A strongly self-interacting component of asymmetric dark matter particles can form compact dark stars. The high dark matter density in these objects may allow significant dark matter annihilation into Standard Model particles, even when the portals to the visible sector are extremely weak. In this paper we argue that compact dark stars could constitute an important source of energy injection during the cosmic dawn era in addition to that of the baryonic stars. Therefore, if dark stars annihilate into photons, the luminosity of dark stars may significantly raise the gas temperature of the Universe at small redshifts. This modification to the standard thermal history of standard Cosmology would have implications for the observed 21-cm signal and the process of reionization, thus providing a new probe for particle dark matter.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"124 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145673744","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 : 2025-12-03DOI: 10.1088/1475-7516/2025/12/003
Yu Miyauchi and Takahiro Tanaka
Boson stars, hypothetical astrophysical objects bound by the self-gravity of a scalar field, have been widely studied as a type of exotic compact object that is horizonless and provides a testing ground for physics beyond the Standard Model. In particular, many previous works have demonstrated methods for distinguishing compact boson stars from black holes in general relativity through gravitational wave observations. However, the formation scenario of compact boson stars within the age of the universe remains unclear. In this paper, we explore a possible scenario for the formation of compact boson stars. The model we consider requires two coupled scalar fields: a complex scalar field that forms a boson star and a spatially homogeneous background field, as formation of a compact boson star cannot be achieved in a single filed model. Using the adiabatic approximation, we show that non-relativistic boson clouds can evolve into compact boson stars through the cosmological time-evolution of the background field. In our model the background field evolves to increase the effective mass of the scalar field, and as a result compact boson stars can form within the cosmological timescale, if the variation of the background field is as large as the Planck scale. However, further investigation is required because the required initial states are not the configurations that can be described by the well-studied Schrödinger-Poisson system.
{"title":"The possibility of formation of compact boson stars via cosmological evolution of a background scalar field","authors":"Yu Miyauchi and Takahiro Tanaka","doi":"10.1088/1475-7516/2025/12/003","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/12/003","url":null,"abstract":"Boson stars, hypothetical astrophysical objects bound by the self-gravity of a scalar field, have been widely studied as a type of exotic compact object that is horizonless and provides a testing ground for physics beyond the Standard Model. In particular, many previous works have demonstrated methods for distinguishing compact boson stars from black holes in general relativity through gravitational wave observations. However, the formation scenario of compact boson stars within the age of the universe remains unclear. In this paper, we explore a possible scenario for the formation of compact boson stars. The model we consider requires two coupled scalar fields: a complex scalar field that forms a boson star and a spatially homogeneous background field, as formation of a compact boson star cannot be achieved in a single filed model. Using the adiabatic approximation, we show that non-relativistic boson clouds can evolve into compact boson stars through the cosmological time-evolution of the background field. In our model the background field evolves to increase the effective mass of the scalar field, and as a result compact boson stars can form within the cosmological timescale, if the variation of the background field is as large as the Planck scale. However, further investigation is required because the required initial states are not the configurations that can be described by the well-studied Schrödinger-Poisson system.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"57 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145658303","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 : 2025-12-03DOI: 10.1088/1475-7516/2025/12/004
Shao-Jun Zhang
We investigate the magnetic Penrose process in the Quevedo-Mashhoon spacetime, immersed in a uniform magnetic field B. This metric is a stationary, axisymmetric, asymptotically flat vacuum solution to Einstein's equations with an arbitrary anomalous quadrupole moment 𝒬. A non-vanishing 𝒬 significantly modifies the near-horizon geometry, creating a multi-lobe ergoregion. Both 𝒬 and B strongly influence the negative-energy region, which can extend well beyond the ergoregion, enabling the magnetic Penrose process to operate far from the ergoregion. Their combined effects allow energy extraction efficiency η to far exceed that of the mechanical Penrose process. The maximum efficiency undergoes three distinct evolutionary stages as 𝒬 varies. In the absence of the magnetic field, efficiency is optimized for more negative 𝒬 (yielding a more oblate spacetime than Kerr). When electromagnetic interactions dominate, efficiency peaks when the infalling fragment's charge and B share the same sign and 𝒬 is more positive (producing a more prolate spacetime than Kerr). These findings support the magnetic Penrose process as a theoretical framework for high-energy cosmic phenomena (e.g., extragalactic high-energy radiation) and as a tool to test the Kerr hypothesis.
{"title":"Penrose process in magnetized non-Kerr rotating spacetime with anomalous quadrupole moment","authors":"Shao-Jun Zhang","doi":"10.1088/1475-7516/2025/12/004","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/12/004","url":null,"abstract":"We investigate the magnetic Penrose process in the Quevedo-Mashhoon spacetime, immersed in a uniform magnetic field B. This metric is a stationary, axisymmetric, asymptotically flat vacuum solution to Einstein's equations with an arbitrary anomalous quadrupole moment 𝒬. A non-vanishing 𝒬 significantly modifies the near-horizon geometry, creating a multi-lobe ergoregion. Both 𝒬 and B strongly influence the negative-energy region, which can extend well beyond the ergoregion, enabling the magnetic Penrose process to operate far from the ergoregion. Their combined effects allow energy extraction efficiency η to far exceed that of the mechanical Penrose process. The maximum efficiency undergoes three distinct evolutionary stages as 𝒬 varies. In the absence of the magnetic field, efficiency is optimized for more negative 𝒬 (yielding a more oblate spacetime than Kerr). When electromagnetic interactions dominate, efficiency peaks when the infalling fragment's charge and B share the same sign and 𝒬 is more positive (producing a more prolate spacetime than Kerr). These findings support the magnetic Penrose process as a theoretical framework for high-energy cosmic phenomena (e.g., extragalactic high-energy radiation) and as a tool to test the Kerr hypothesis.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"198200 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145658302","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 : 2025-12-03DOI: 10.1088/1475-7516/2025/12/005
Beatriz Hernández-Molinero, Matteo Calabrese, Carmelita Carbone, Alessandro Greco, Raul Jimenez and Carlos Peña Garay
We use the high-resolution HR-DEMNUni simulations to compute cross-correlations of the Cosmic Neutrino Background quantities, like neutrino density, deflection angle, and velocity, with other quantities, like cold dark matter density and effective weak lensing convergence, by accounting for the space-time delay between signals on Earth. We provide this to theoretically illustrate how much can be learned from these cross-correlation signals, once the cosmic neutrino background is detected with instruments in multiple locations. Against a naive expectation of null cross-correlation, we show that the signal is non zero, specially at the largest scales. We also discuss the scenario of co-located cross-correlations between dark matter, weak lensing and a future neutrino-induced photon emission signal. As cross-correlations will be comparable to auto-correlations of the cosmic neutrino background itself and are less affected by cosmic variance and shotnoise, these might be the ones to be measured first. Our predictions thus provide the imprint of what cosmological massive neutrinos, with total mass ∑mν ∼ 0.1 eV, should look like from cosmological observations.
{"title":"Cross-correlations of the Cosmic Neutrino Background with the dark matter field: HR-DEMNUni simulation analysis","authors":"Beatriz Hernández-Molinero, Matteo Calabrese, Carmelita Carbone, Alessandro Greco, Raul Jimenez and Carlos Peña Garay","doi":"10.1088/1475-7516/2025/12/005","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/12/005","url":null,"abstract":"We use the high-resolution HR-DEMNUni simulations to compute cross-correlations of the Cosmic Neutrino Background quantities, like neutrino density, deflection angle, and velocity, with other quantities, like cold dark matter density and effective weak lensing convergence, by accounting for the space-time delay between signals on Earth. We provide this to theoretically illustrate how much can be learned from these cross-correlation signals, once the cosmic neutrino background is detected with instruments in multiple locations. Against a naive expectation of null cross-correlation, we show that the signal is non zero, specially at the largest scales. We also discuss the scenario of co-located cross-correlations between dark matter, weak lensing and a future neutrino-induced photon emission signal. As cross-correlations will be comparable to auto-correlations of the cosmic neutrino background itself and are less affected by cosmic variance and shotnoise, these might be the ones to be measured first. Our predictions thus provide the imprint of what cosmological massive neutrinos, with total mass ∑mν ∼ 0.1 eV, should look like from cosmological observations.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"28 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145658304","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 : 2025-12-03DOI: 10.1088/1475-7516/2025/12/007
Fernanda Oliveira, Bruno Ribeiro, Wiliam S. Hipólito-Ricaldi, Felipe Avila and Armando Bernui
Several models based on General Relativity and Modified Gravity aim to reproduce the observed universe with precision comparable to the flat-ΛCDM cosmological model. In this study, we investigate the consistency of some of these models with current high-redshift cosmic data, assessing their ability to simultaneously describe both the background expansion and matter clustering, using measurements of the Hubble parameter H(z), the luminosity distance DL(z), and the growth rate of structures [fσ8](z) through parametric and non-parametric methods. Our results indicate that background observables alone offer limited capacity to distinguish between models, while the inclusion of growth of structures data proves useful in revealing deviations, even if small. An F(Q) model, the non-flat ΛCDM and the ωCDM emerge as alternatives well supported by data, closely matching the growth data and showing performance comparable to ΛCDM, as revealed by the Akaike Information Criterion. In contrast, F(R) models are strongly disfavored compared to ΛCDM and F(Q). However, according to the Bayesian Information Criterion, ΛCDM remains the preferred model among the models analysed. These analyses illustrate the usefulness of both parametric and non-parametric approaches to explore the observational viability of alternative cosmological models.
基于广义相对论和修正引力的几个模型旨在以与平坦的-ΛCDM宇宙模型相当的精度再现观测到的宇宙。在这项研究中，我们通过参数和非参数方法测量哈勃参数H(z)、光度距离DL(z)和结构增长率[fσ8](z)，研究了这些模型与当前高红移宇宙数据的一致性，评估了它们同时描述背景膨胀和物质聚类的能力。我们的研究结果表明，单独的背景可观测值提供了有限的能力来区分模型，而包含结构增长数据在揭示偏差时被证明是有用的，即使很小。F(Q)模型、非平坦ΛCDM和ωCDM作为备选模型得到了数据的良好支持，与增长数据密切匹配，并显示出与赤池信息标准（Akaike Information Criterion）所揭示的ΛCDM相当的性能。相反，与ΛCDM和F(Q)相比，F(R)模型非常不受欢迎。然而，根据贝叶斯信息准则，ΛCDM仍然是所分析模型中的首选模型。这些分析说明了参数方法和非参数方法在探索其他宇宙学模型的观测可行性方面的有效性。
{"title":"Viability of general relativity and modified gravity cosmologies using high-redshift cosmic probes","authors":"Fernanda Oliveira, Bruno Ribeiro, Wiliam S. Hipólito-Ricaldi, Felipe Avila and Armando Bernui","doi":"10.1088/1475-7516/2025/12/007","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/12/007","url":null,"abstract":"Several models based on General Relativity and Modified Gravity aim to reproduce the observed universe with precision comparable to the flat-ΛCDM cosmological model. In this study, we investigate the consistency of some of these models with current high-redshift cosmic data, assessing their ability to simultaneously describe both the background expansion and matter clustering, using measurements of the Hubble parameter H(z), the luminosity distance DL(z), and the growth rate of structures [fσ8](z) through parametric and non-parametric methods. Our results indicate that background observables alone offer limited capacity to distinguish between models, while the inclusion of growth of structures data proves useful in revealing deviations, even if small. An F(Q) model, the non-flat ΛCDM and the ωCDM emerge as alternatives well supported by data, closely matching the growth data and showing performance comparable to ΛCDM, as revealed by the Akaike Information Criterion. In contrast, F(R) models are strongly disfavored compared to ΛCDM and F(Q). However, according to the Bayesian Information Criterion, ΛCDM remains the preferred model among the models analysed. These analyses illustrate the usefulness of both parametric and non-parametric approaches to explore the observational viability of alternative cosmological models.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"34 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145658305","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 : 2025-12-03DOI: 10.1088/1475-7516/2025/12/006
Matthew R. Buckley, Peizhi Du, Nicolas Fernandez and Mitchell J. Weikert
Current cosmological data are well-described by the Lambda-Cold Dark Matter (ΛCDM) model, which assumes adiabatic initial conditions for the primordial density perturbations. This agreement between data and theory enables strong constraints on new physics that generates isocurvature perturbations. Existing constraints typically assume a simple power law form for the isocurvature power spectrum. However, many new physics scenarios — such as cosmological phase transitions and gravitational particle production — can deviate from this assumption. To derive general constraints which apply to a wide variety of new physics scenarios, we consider four types of isocurvature modes (dark matter, baryon, dark radiation and neutrino density isocurvature) and parametrize the isocurvature power spectrum using two general forms: a delta function and a broken power law. Using data from the cosmic microwave background (CMB), baryon acoustic oscillations, the Lyman-α forest, and CMB spectral distortions, we place constraints on the isocurvature power spectrum across a wide range of scales, from 10-4 Mpc-1 to 104 Mpc-1.
{"title":"General constraints on isocurvature from the CMB and Ly-α forest","authors":"Matthew R. Buckley, Peizhi Du, Nicolas Fernandez and Mitchell J. Weikert","doi":"10.1088/1475-7516/2025/12/006","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/12/006","url":null,"abstract":"Current cosmological data are well-described by the Lambda-Cold Dark Matter (ΛCDM) model, which assumes adiabatic initial conditions for the primordial density perturbations. This agreement between data and theory enables strong constraints on new physics that generates isocurvature perturbations. Existing constraints typically assume a simple power law form for the isocurvature power spectrum. However, many new physics scenarios — such as cosmological phase transitions and gravitational particle production — can deviate from this assumption. To derive general constraints which apply to a wide variety of new physics scenarios, we consider four types of isocurvature modes (dark matter, baryon, dark radiation and neutrino density isocurvature) and parametrize the isocurvature power spectrum using two general forms: a delta function and a broken power law. Using data from the cosmic microwave background (CMB), baryon acoustic oscillations, the Lyman-α forest, and CMB spectral distortions, we place constraints on the isocurvature power spectrum across a wide range of scales, from 10-4 Mpc-1 to 104 Mpc-1.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"157 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145658309","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 : 2025-12-01DOI: 10.1088/1475-7516/2025/12/002
E. Gleave and A.H. Jaffe
Gravitational wave (GW) observations probe both a diffuse, stochastic gravitational wave background (SGWB) as well as individual cataclysmic events such as the merger of two compact objects. The detection and description of the gravitational-wave background requires somewhat different techniques than required for individual events. In this paper, we probe the sensitivity of present and future GW telescopes to different background sources, including both those expected from unresolved compact binaries in both their quasi-Newtonian quiescent and their eventual mergers, as well as more speculative cosmological sources such as inflation, cosmic strings, and phase transitions, over regions in which those sources can be described by a single power law. We develop a Fisher matrix formalism to forecast coming sensitivities of single and multiple experiments, and novel visualizations taking into account the increase in sensitivity to a background over time.
{"title":"How to constrain the stochastic gravitational wave background with multi-frequency detections","authors":"E. Gleave and A.H. Jaffe","doi":"10.1088/1475-7516/2025/12/002","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/12/002","url":null,"abstract":"Gravitational wave (GW) observations probe both a diffuse, stochastic gravitational wave background (SGWB) as well as individual cataclysmic events such as the merger of two compact objects. The detection and description of the gravitational-wave background requires somewhat different techniques than required for individual events. In this paper, we probe the sensitivity of present and future GW telescopes to different background sources, including both those expected from unresolved compact binaries in both their quasi-Newtonian quiescent and their eventual mergers, as well as more speculative cosmological sources such as inflation, cosmic strings, and phase transitions, over regions in which those sources can be described by a single power law. We develop a Fisher matrix formalism to forecast coming sensitivities of single and multiple experiments, and novel visualizations taking into account the increase in sensitivity to a background over time.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"29 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145645264","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 : 2025-12-01DOI: 10.1088/1475-7516/2025/12/001
Parsa Ghafour, Saeed Tavasoli and Mohammad Reza Shojaei
Cosmic voids are large, nearly empty regions that lie between the web of galaxies, filaments and walls, and are recognized for their extensive applications in the field of cosmology and astrophysics. Despite their significance, a universal definition of voids remains unsettled as various void-finding methods identify different types of voids, each differing in shape and density, based on the method that were used. In this paper, we present VEGA, a novel algorithm for void identification. VEGA utilizes Voronoi tessellation to divide the dataset space into spatial cells and applies the Convex Hull algorithm to estimate the volume of each cell. It then integrates Genetic Algorithm analysis with luminosity density contrast to filter out over-dense cells and retain the remaining ones, referred to as void block cells. These filtered cells form the basis for constructing the final void structures. VEGA operates on a grid of points, which increases the algorithm's spatial accessibility to the dataset and facilitates the identification of seed points around which the algorithm constructs the voids. To evaluate VEGA's performance, we applied both VEGA and the Aikio-Mähönen method to the same test dataset. We compared the resulting void populations in terms of their luminosity and number density contrast, as well as their morphological features such as sphericity. This comparison demonstrated that the VEGA void-finding method yields reliable results and can be effectively applied to various tracer distributions.
{"title":"VEGA: Voids idEntification using Genetic Algorithm","authors":"Parsa Ghafour, Saeed Tavasoli and Mohammad Reza Shojaei","doi":"10.1088/1475-7516/2025/12/001","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/12/001","url":null,"abstract":"Cosmic voids are large, nearly empty regions that lie between the web of galaxies, filaments and walls, and are recognized for their extensive applications in the field of cosmology and astrophysics. Despite their significance, a universal definition of voids remains unsettled as various void-finding methods identify different types of voids, each differing in shape and density, based on the method that were used. In this paper, we present VEGA, a novel algorithm for void identification. VEGA utilizes Voronoi tessellation to divide the dataset space into spatial cells and applies the Convex Hull algorithm to estimate the volume of each cell. It then integrates Genetic Algorithm analysis with luminosity density contrast to filter out over-dense cells and retain the remaining ones, referred to as void block cells. These filtered cells form the basis for constructing the final void structures. VEGA operates on a grid of points, which increases the algorithm's spatial accessibility to the dataset and facilitates the identification of seed points around which the algorithm constructs the voids. To evaluate VEGA's performance, we applied both VEGA and the Aikio-Mähönen method to the same test dataset. We compared the resulting void populations in terms of their luminosity and number density contrast, as well as their morphological features such as sphericity. This comparison demonstrated that the VEGA void-finding method yields reliable results and can be effectively applied to various tracer distributions.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"14 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145645311","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 : 2025-11-28DOI: 10.1088/1475-7516/2025/11/088
Shuntaro Aoki, Hajime Otsuka and Ryota Yanagita
Recent results from the Atacama Cosmology Telescope (ACT), when combined with Planck and DESI datasets, indicate a scalar spectral index ns larger than that reported in the Planck 2018 baseline, thereby challenging conventional Starobinsky-type (α-attractor) inflationary scenarios at the 2σ level. In addition, the positive running of the spectral index αs implied by the data provides strong constraints on these models. In this paper, we explore the possibility that the presence of an additional heavy field during inflation, with a mass of order the Hubble scale and a sizable mixing coupling to the inflaton, can reconcile such inflationary models with the ACT results by increasing both ns and αs, particularly in the strong-mixing regime. Furthermore, we extend this framework to traditional inflation models such as chaotic inflation and natural inflation, which have already been excluded by Planck alone, and show that they can be revived in certain regions of parameter space. Inflationary observables, including the spectral index ns, the tensor-to-scalar ratio r, and the running αs, are computed within the single-field EFT approach, which is applicable even in the presence of a heavy field with large mixing. We also discuss the non-Gaussianity signatures arising from the heavy field, noting that parts of the parameter space are already excluded or can be tested in future observations. Finally, we present concrete model realizations that allow for such a large mixing.
{"title":"Heavy field effects on inflationary models in light of ACT data","authors":"Shuntaro Aoki, Hajime Otsuka and Ryota Yanagita","doi":"10.1088/1475-7516/2025/11/088","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/11/088","url":null,"abstract":"Recent results from the Atacama Cosmology Telescope (ACT), when combined with Planck and DESI datasets, indicate a scalar spectral index ns larger than that reported in the Planck 2018 baseline, thereby challenging conventional Starobinsky-type (α-attractor) inflationary scenarios at the 2σ level. In addition, the positive running of the spectral index αs implied by the data provides strong constraints on these models. In this paper, we explore the possibility that the presence of an additional heavy field during inflation, with a mass of order the Hubble scale and a sizable mixing coupling to the inflaton, can reconcile such inflationary models with the ACT results by increasing both ns and αs, particularly in the strong-mixing regime. Furthermore, we extend this framework to traditional inflation models such as chaotic inflation and natural inflation, which have already been excluded by Planck alone, and show that they can be revived in certain regions of parameter space. Inflationary observables, including the spectral index ns, the tensor-to-scalar ratio r, and the running αs, are computed within the single-field EFT approach, which is applicable even in the presence of a heavy field with large mixing. We also discuss the non-Gaussianity signatures arising from the heavy field, noting that parts of the parameter space are already excluded or can be tested in future observations. Finally, we present concrete model realizations that allow for such a large mixing.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"1 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145611182","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 : 2025-11-27DOI: 10.1088/1475-7516/2025/11/084
Arhum Ansari, Arka Banerjee, Sachin Jain and Sahil Lalsodagar
Bootstrap techniques relying on the constraints imposed by Extended Galilean Invariance (EGI), have proved to be very useful in the context of perturbation theory of the Large Scale Structure (LSS). It has been formulated in both the Eulerian as well as Lagrangian space. While the Eulerian bootstrap formalism has been successfully applied to both tracer and matter kernels, the application of bootstrap methods in Lagrangian space has so far been restricted to matter. Up to third order, it has been shown that implementing EGI constraints in Eulerian space fully reproduces the bias expansion for tracers. Previous studies have demonstrated that time non-locality affects the bias expansion in a non-trivial way starting from fifth order. Motivated by this fact, we extend the bootstrap approach upto fifth order in both Eulerian and Lagrangian space and demonstrate that it fully captures the time non-local effects. For this, we generalize the Lagrangian bootstrap for tracers, and found that it agrees with the corresponding results obtained in Eulerian space. One of the major challenges in implementing EGI constraints in Eulerian space, is to systematically find out all the “spurious poles” and make them vanish. We have proposed a method that bypasses this difficulty making the procedure tractable at higher orders. From Lagrangian perspective, we have identified coefficients in the tracer kernel whose ratios are independent of tracer properties and may serve as direct probes of the underlying cosmology.
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