Pub Date : 2026-03-06DOI: 10.1088/1475-7516/2026/03/018
Albert Escrivà, Jaume Garriga and Shi Pi
We investigate the formation of primordial black holes (PBHs) in inflationary scenarios featuring an ultra-slow-roll (USR) plateau with a sharp transition to slow roll. We focus on two coexisting production channels: PBHs originating from relic vacuum bubbles where the inflaton got trapped on the plateau, and PBHs arising from standard adiabatic density perturbations. From detailed numerical simulations we find that the bubbles are generically surrounded by type-II curvature fluctuations. Special attention is given to the distribution of initial conditions, including the relevant mean profiles and shape dispersion around them. For the adiabatic channel, we extend the logarithmic template formula ζ[ζG], which maps the Gaussian curvature perturbation to the fully non-Gaussian one while incorporating mode evolution, and we compare this with numerical results obtained using the δN formalism. While the template departs from numerical results near its logarithmic divergence, it still provides accurate threshold values for PBH formation in the parameter range relevant to our analysis. Finally, we compute the PBH mass functions for both channels. We find that the adiabatic channel dominates over the bubble-induced channel by a factor ∼𝒪(10-102), and that both contributions are largely dominated by the mean profiles.
{"title":"Inflationary relics from an ultra-slow-roll plateau","authors":"Albert Escrivà, Jaume Garriga and Shi Pi","doi":"10.1088/1475-7516/2026/03/018","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/018","url":null,"abstract":"We investigate the formation of primordial black holes (PBHs) in inflationary scenarios featuring an ultra-slow-roll (USR) plateau with a sharp transition to slow roll. We focus on two coexisting production channels: PBHs originating from relic vacuum bubbles where the inflaton got trapped on the plateau, and PBHs arising from standard adiabatic density perturbations. From detailed numerical simulations we find that the bubbles are generically surrounded by type-II curvature fluctuations. Special attention is given to the distribution of initial conditions, including the relevant mean profiles and shape dispersion around them. For the adiabatic channel, we extend the logarithmic template formula ζ[ζG], which maps the Gaussian curvature perturbation to the fully non-Gaussian one while incorporating mode evolution, and we compare this with numerical results obtained using the δN formalism. While the template departs from numerical results near its logarithmic divergence, it still provides accurate threshold values for PBH formation in the parameter range relevant to our analysis. Finally, we compute the PBH mass functions for both channels. We find that the adiabatic channel dominates over the bubble-induced channel by a factor ∼𝒪(10-102), and that both contributions are largely dominated by the mean profiles.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"53 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360983","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 : 2026-03-06DOI: 10.1088/1475-7516/2026/03/017
Mahboubeh Shahrbaf, Prashant Thakur and Davood Rafiei Karkevandi
We investigate the impact of a hypothetical bosonic dark matter (DM) candidate, the sexaquark, on the fundamental (f-mode) oscillations of neutron stars (NSs). By varying the DM particle mass and considering different core compositions including hypernuclear matter, sexaquark DM, and deconfined quark matter (QM), we construct hybrid equations of state (EOS) with a smooth hadron-quark crossover that remain consistent with current astrophysical constraints on mass (M), radius (R), and tidal deformability (Λ). Our analysis shows that the presence of these exotic components systematically alters quasi-universal f-mode relations considering f-mode frequency (f), damping time (τ), compactness (C), and angular velocity (ω). In particular, relations involving f-√(M/R3), (R4/M3τ)(C), ωM(C), require higher-order polynomial fits compared to standard studies. Quadratic forms remain sufficient for f-√(M/R3) and ωM(C), while damping-time relations such as (R4/M3τ)(C) demand higher-order corrections to capture their curvature. For f(Λ), a cubic fit provides a satisfactory description. Within this extended framework the relations remain tight and effectively composition independent. These results suggest that precise f-mode measurements with future gravitational-wave detectors could provide clear signatures of DM and other exotic matter in NS interiors.
{"title":"Probing strange dark matter through f-mode oscillations of neutron stars with hyperons and quark matter","authors":"Mahboubeh Shahrbaf, Prashant Thakur and Davood Rafiei Karkevandi","doi":"10.1088/1475-7516/2026/03/017","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/017","url":null,"abstract":"We investigate the impact of a hypothetical bosonic dark matter (DM) candidate, the sexaquark, on the fundamental (f-mode) oscillations of neutron stars (NSs). By varying the DM particle mass and considering different core compositions including hypernuclear matter, sexaquark DM, and deconfined quark matter (QM), we construct hybrid equations of state (EOS) with a smooth hadron-quark crossover that remain consistent with current astrophysical constraints on mass (M), radius (R), and tidal deformability (Λ). Our analysis shows that the presence of these exotic components systematically alters quasi-universal f-mode relations considering f-mode frequency (f), damping time (τ), compactness (C), and angular velocity (ω). In particular, relations involving f-√(M/R3), (R4/M3τ)(C), ωM(C), require higher-order polynomial fits compared to standard studies. Quadratic forms remain sufficient for f-√(M/R3) and ωM(C), while damping-time relations such as (R4/M3τ)(C) demand higher-order corrections to capture their curvature. For f(Λ), a cubic fit provides a satisfactory description. Within this extended framework the relations remain tight and effectively composition independent. These results suggest that precise f-mode measurements with future gravitational-wave detectors could provide clear signatures of DM and other exotic matter in NS interiors.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"32 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360982","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 : 2026-03-06DOI: 10.1088/1475-7516/2026/03/016
Kazuma Minami, Kyohei Mukaida and Kazunori Nakayama
In order for an inflationary universe to evolve into a hot universe, a process known as reheating is required. However, the precise mechanism of reheating remains unknown. We show that if the reheating is triggered by thermal dissipation effects, distinctive features appear in the spectrum of primordial gravitational waves. This suggests a possible way to observationally probe the physics of reheating.
{"title":"Reheating with thermal dissipation and primordial gravitational waves","authors":"Kazuma Minami, Kyohei Mukaida and Kazunori Nakayama","doi":"10.1088/1475-7516/2026/03/016","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/016","url":null,"abstract":"In order for an inflationary universe to evolve into a hot universe, a process known as reheating is required. However, the precise mechanism of reheating remains unknown. We show that if the reheating is triggered by thermal dissipation effects, distinctive features appear in the spectrum of primordial gravitational waves. This suggests a possible way to observationally probe the physics of reheating.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"16 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360920","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 : 2026-03-06DOI: 10.1088/1475-7516/2026/03/020
Jens Boos and Felix Wunsch
We report on a novel set of very-high-frequency quasi-periodic oscillations (VHFQPO's) in the context of compact, non-singular horizonless objects. Focussing on the static, spherically symmetric case we utilize metrics of non-singular black holes that are accompanied by a regulator length scale L > 0. The choice L ≳ GM generically removes the horizon from these metrics leading to compact, horizonless but non-singular objects. This generically guarantees the existence of a stable orbit at small radii r ≪ rISCO, independent of the angular momentum of the massive particle. Crucially, the absence of a horizon allows the resulting VHFQPO's to escape to infinity, spanning the range from 1kHz (M = 10M⊙) to 25 kHz (M = 2M⊙). Within the paradigm of non-singular spacetime geometries, the absence of such VHFQPO's from X-ray binary spectra implies the presence of a horizon around the central, compact object.
{"title":"Novel very-high-frequency quasi-periodic oscillations of compact, non-singular objects","authors":"Jens Boos and Felix Wunsch","doi":"10.1088/1475-7516/2026/03/020","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/020","url":null,"abstract":"We report on a novel set of very-high-frequency quasi-periodic oscillations (VHFQPO's) in the context of compact, non-singular horizonless objects. Focussing on the static, spherically symmetric case we utilize metrics of non-singular black holes that are accompanied by a regulator length scale L > 0. The choice L ≳ GM generically removes the horizon from these metrics leading to compact, horizonless but non-singular objects. This generically guarantees the existence of a stable orbit at small radii r ≪ rISCO, independent of the angular momentum of the massive particle. Crucially, the absence of a horizon allows the resulting VHFQPO's to escape to infinity, spanning the range from 1kHz (M = 10M⊙) to 25 kHz (M = 2M⊙). Within the paradigm of non-singular spacetime geometries, the absence of such VHFQPO's from X-ray binary spectra implies the presence of a horizon around the central, compact object.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"5 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360985","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 : 2026-03-06DOI: 10.1088/1475-7516/2026/03/019
H. Ebina, M. White, A. Raichoor, Arjun Dey, D. Schlegel, D. Lang, Y. Luo, J. Aguilar, S. Ahlen, A. Anand, D. Bianchi, D. Brooks, F.J. Castander, T. Claybaugh, A. Cuceu, K.S. Dawson, A. de la Macorra, Biprateep Dey, P. Doel, S. Ferraro, A. Font-Ribera, J.E. Forero-Romero, E. Gaztañaga, S.Gontcho A. Gontcho, G. Gutierrez, H.K. Herrera-Alcantar, C. Howlett, M. Ishak, R. Joyce, R. Kehoe, D. Kirkby, T. Kisner, A. Kremin, O. Lahav, A. Lambert, M. Landriau, L. Le Guillou, C. Magneville, M. Manera, P. Martini, A. Meisner, R. Miquel, J. Moustakas, E. Mueller, S. Nadathur, N. Palanque-Delabrouille, W.J. Percival, C. Poppett, F. Prada, I. Pérez-Ràfols, G. Rossi, E. Sanchez, M. Schubnell, J. Silber, D. Sprayberry, G. Tarlé, B.A. Weaver, C. Yèche, R. Zhou and H. Zou
Next-generation large-scale structure spectroscopic surveys will probe cosmology at high redshifts (2.3 < z < 3.5), relying on abundant galaxy tracers such as Lyα emitters (LAEs) and Lyman break galaxies (LBGs). Medium-band photometry has emerged as a potential technique for efficiently selecting these high-redshift galaxies. In this work, we present clustering analysis of medium-band selected galaxies at high redshift, utilizing photometric data from the Intermediate Band Imaging Survey (IBIS) and spectroscopic data from the Dark Energy Spectroscopic Instrument (DESI). We interpret the clustering of such samples using both Halo Occupation Distribution (HOD) modeling and a perturbation theory description of large-scale structure. Our modeling indicates that the current target sample is composed from an overlapping mixture of LAEs and LBGs with emission lines. Despite differences in target selection, we find that the clustering properties are consistent with previous studies, with correlation lengths r0 ≃ 3-4 h-1Mpc and a linear bias of b ∼ 1.8-2.5. Finally, we discuss the simulation requirements implied by these measurements and demonstrate that the properties of the samples would make them excellent targets to enhance our understanding of the high-z universe.
下一代大规模结构光谱调查将在高红移（2.3 < z < 3.5）下探测宇宙，依靠丰富的星系示踪剂，如Lyα发射体（LAEs）和Lyman break星系（LBGs）。中波段光度法已经成为一种有效选择这些高红移星系的潜在技术。在这项工作中，我们利用中间波段成像调查（IBIS）的光度数据和暗能量光谱仪器（DESI）的光谱数据，对高红移的中波段选定星系进行了聚类分析。我们使用Halo职业分布（HOD）模型和大尺度结构的微扰理论描述来解释这些样本的聚类。我们的模型表明，当前的目标样品是由LAEs和lbg的重叠混合物组成的，并且具有发射线。尽管在目标选择上存在差异，但我们发现聚类性质与前人的研究一致，相关长度为r0≃3-4 h-1Mpc，线性偏差为b ~ 1.8-2.5。最后，我们讨论了这些测量所隐含的模拟要求，并证明了样品的性质将使它们成为增强我们对高z宇宙理解的优秀目标。
{"title":"Clustering analysis of medium-band selected high-redshift galaxies","authors":"H. Ebina, M. White, A. Raichoor, Arjun Dey, D. Schlegel, D. Lang, Y. Luo, J. Aguilar, S. Ahlen, A. Anand, D. Bianchi, D. Brooks, F.J. Castander, T. Claybaugh, A. Cuceu, K.S. Dawson, A. de la Macorra, Biprateep Dey, P. Doel, S. Ferraro, A. Font-Ribera, J.E. Forero-Romero, E. Gaztañaga, S.Gontcho A. Gontcho, G. Gutierrez, H.K. Herrera-Alcantar, C. Howlett, M. Ishak, R. Joyce, R. Kehoe, D. Kirkby, T. Kisner, A. Kremin, O. Lahav, A. Lambert, M. Landriau, L. Le Guillou, C. Magneville, M. Manera, P. Martini, A. Meisner, R. Miquel, J. Moustakas, E. Mueller, S. Nadathur, N. Palanque-Delabrouille, W.J. Percival, C. Poppett, F. Prada, I. Pérez-Ràfols, G. Rossi, E. Sanchez, M. Schubnell, J. Silber, D. Sprayberry, G. Tarlé, B.A. Weaver, C. Yèche, R. Zhou and H. Zou","doi":"10.1088/1475-7516/2026/03/019","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/019","url":null,"abstract":"Next-generation large-scale structure spectroscopic surveys will probe cosmology at high redshifts (2.3 < z < 3.5), relying on abundant galaxy tracers such as Lyα emitters (LAEs) and Lyman break galaxies (LBGs). Medium-band photometry has emerged as a potential technique for efficiently selecting these high-redshift galaxies. In this work, we present clustering analysis of medium-band selected galaxies at high redshift, utilizing photometric data from the Intermediate Band Imaging Survey (IBIS) and spectroscopic data from the Dark Energy Spectroscopic Instrument (DESI). We interpret the clustering of such samples using both Halo Occupation Distribution (HOD) modeling and a perturbation theory description of large-scale structure. Our modeling indicates that the current target sample is composed from an overlapping mixture of LAEs and LBGs with emission lines. Despite differences in target selection, we find that the clustering properties are consistent with previous studies, with correlation lengths r0 ≃ 3-4 h-1Mpc and a linear bias of b ∼ 1.8-2.5. Finally, we discuss the simulation requirements implied by these measurements and demonstrate that the properties of the samples would make them excellent targets to enhance our understanding of the high-z universe.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"20 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360984","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 : 2026-03-06DOI: 10.1088/1475-7516/2026/03/021
Zi-Yu Tang and Eleftherios Papantonopoulos
It is known that the axion-photon coupling can lead to quantum stimulated emission of photons and classic exponential amplification of electromagnetic (EM) fields at half the axion mass frequency, when the axion density or the coupling constant is sufficiently large. In this work, we studied the EM photon cloud induced from an axion cloud around a Kerr black hole in the first order of the coupling constant classically. In the presence of a static EM background (such as the extended Wald solution motivated by astrophysical environments), we found that an EM photon cloud emerges, oscillating at the same frequency as the axion cloud and growing exponentially in accordance with the axion cloud when the superradiant condition for the axion field is satisfied. The evolution of the EM photon cloud with time and azimuthal angle is obtained analytically while the cross-sectional distribution is solved numerically. The induced EM field exhibits symmetries that are markedly different from those of the background EM field. Consequently, the induced photon cloud forms an unstable bound configuration that emits EM waves to spatial infinity while being replenished by the axion cloud, providing a potential observational signature of both the presence of an axion cloud and axion-photon coupling.
{"title":"A photon cloud induced from an axion cloud","authors":"Zi-Yu Tang and Eleftherios Papantonopoulos","doi":"10.1088/1475-7516/2026/03/021","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/021","url":null,"abstract":"It is known that the axion-photon coupling can lead to quantum stimulated emission of photons and classic exponential amplification of electromagnetic (EM) fields at half the axion mass frequency, when the axion density or the coupling constant is sufficiently large. In this work, we studied the EM photon cloud induced from an axion cloud around a Kerr black hole in the first order of the coupling constant classically. In the presence of a static EM background (such as the extended Wald solution motivated by astrophysical environments), we found that an EM photon cloud emerges, oscillating at the same frequency as the axion cloud and growing exponentially in accordance with the axion cloud when the superradiant condition for the axion field is satisfied. The evolution of the EM photon cloud with time and azimuthal angle is obtained analytically while the cross-sectional distribution is solved numerically. The induced EM field exhibits symmetries that are markedly different from those of the background EM field. Consequently, the induced photon cloud forms an unstable bound configuration that emits EM waves to spatial infinity while being replenished by the axion cloud, providing a potential observational signature of both the presence of an axion cloud and axion-photon coupling.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"46 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360936","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 : 2026-03-06DOI: 10.1088/1475-7516/2026/03/022
L. Pizzuti, A. Biviano, K. Umetsu, E. Agostoni, A. Autorino, A.M. Pombo, A. Mercurio and M. D'Addona
We investigate the anisotropic stress parameter, η = Ψ/Φ, defined as the ratio of the gravitational potentials in the linearly perturbed Friedmann-Lemaître Robertson-Walker metric, as a probe of deviations from general relativity across astrophysical to cosmological scales. Using mass profiles reconstructed from high-precision lensing and kinematics of nine galaxy clusters from the CLASH-VLT sample, we derive η(r) as a function of the radial distance from the cluster centres, over the range [0.1 Mpc,1.2 r200L], where r200L is virial radius best-fit from lensing data. When using a Navarro-Frenk-White or an Hernquist profile to model the total matter distribution, we find consistency with general relativity (η = 1) within 2σ for the full radial range for all the sampled clusters. However, adopting a Burkert profile introduces mild tension with general relativity, reaching the 3σ level in two systems. Assuming a negligible time-dependence in the redshift range spawned by the clusters, we obtain the joint constraint η (η = 1.0 Mpc) = 0.93+0.48-0.40 (stat) ± 0.47 (syst) at 95% confidence level — an improvement of approximately 40% over previous estimates. We discuss the impact of systematics on the constraints, and we highlight the implications of this result for current and upcoming cluster surveys.
{"title":"CLASH-VLT: Constraining deviation from GR with the mass profiles of nine massive galaxy clusters","authors":"L. Pizzuti, A. Biviano, K. Umetsu, E. Agostoni, A. Autorino, A.M. Pombo, A. Mercurio and M. D'Addona","doi":"10.1088/1475-7516/2026/03/022","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/022","url":null,"abstract":"We investigate the anisotropic stress parameter, η = Ψ/Φ, defined as the ratio of the gravitational potentials in the linearly perturbed Friedmann-Lemaître Robertson-Walker metric, as a probe of deviations from general relativity across astrophysical to cosmological scales. Using mass profiles reconstructed from high-precision lensing and kinematics of nine galaxy clusters from the CLASH-VLT sample, we derive η(r) as a function of the radial distance from the cluster centres, over the range [0.1 Mpc,1.2 r200L], where r200L is virial radius best-fit from lensing data. When using a Navarro-Frenk-White or an Hernquist profile to model the total matter distribution, we find consistency with general relativity (η = 1) within 2σ for the full radial range for all the sampled clusters. However, adopting a Burkert profile introduces mild tension with general relativity, reaching the 3σ level in two systems. Assuming a negligible time-dependence in the redshift range spawned by the clusters, we obtain the joint constraint η (η = 1.0 Mpc) = 0.93+0.48-0.40 (stat) ± 0.47 (syst) at 95% confidence level — an improvement of approximately 40% over previous estimates. We discuss the impact of systematics on the constraints, and we highlight the implications of this result for current and upcoming cluster surveys.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"46 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147360986","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 : 2026-03-05DOI: 10.1088/1475-7516/2026/03/015
Tal Adi
We present a model-independent null test of the late-time cosmological response to a reduced sound horizon, as typically required by early-universe solutions to the Hubble tension. In this approach, we phenomenologically impose a shorter sound horizon without modeling early-universe physics to isolate its impact on late-time dark energy inference. Using baryon acoustic oscillations (BAO), supernovae (SN), big bang nucleosynthesis (BBN), and local H0 data, while explicitly avoiding CMB anisotropies, we examine how this calibration shift propagates into constraints on the dark energy equation of state. We find that lowering rd systematically drives the w0-wa posterior toward less dynamical, quintessence-like behavior, bringing it closer to ΛCDM. This result underscores that some of the apparent evidence for evolving or phantom-like dark energy may reflect early-universe assumptions rather than genuine late-time dynamics. More broadly, our analysis highlights the importance of carefully disentangling calibration effects from physical evolution in interpreting forthcoming results from DESI and future surveys.
{"title":"Lowering the horizon on Dark Energy: A late-time response to early solutions for the Hubble tension","authors":"Tal Adi","doi":"10.1088/1475-7516/2026/03/015","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/015","url":null,"abstract":"We present a model-independent null test of the late-time cosmological response to a reduced sound horizon, as typically required by early-universe solutions to the Hubble tension. In this approach, we phenomenologically impose a shorter sound horizon without modeling early-universe physics to isolate its impact on late-time dark energy inference. Using baryon acoustic oscillations (BAO), supernovae (SN), big bang nucleosynthesis (BBN), and local H0 data, while explicitly avoiding CMB anisotropies, we examine how this calibration shift propagates into constraints on the dark energy equation of state. We find that lowering rd systematically drives the w0-wa posterior toward less dynamical, quintessence-like behavior, bringing it closer to ΛCDM. This result underscores that some of the apparent evidence for evolving or phantom-like dark energy may reflect early-universe assumptions rather than genuine late-time dynamics. More broadly, our analysis highlights the importance of carefully disentangling calibration effects from physical evolution in interpreting forthcoming results from DESI and future surveys.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"1 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147358772","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 : 2026-03-05DOI: 10.1088/1475-7516/2026/03/006
Alexander B. Kaganovich
The Higgs sector of the Two-Measure Theory (TMT) extension of the electroweak SM (TMSM) is studied in the context of cosmology, where the only non-zero component φ of the cosmologically averaged Higgs field plays the role of the inflaton. The self-consistency of the system of equations obtained from the original action has the form of an algebraic constraint defining the scalar ζ, which is the ratio of two volume measures, as a function of the field φ and its first derivatives. The scalar ζ is present in all equations of motion and has a significant effect on the dynamics of the fields. After the transition in the equations of motion to the Einstein frame with the spatially flat Friedmann metric, it is convenient to describe the resulting system of equations using the action Seff and the Lagrangian Leff, which we call the TMT-effective action and the TMT-effective Lagrangian and from which these equations can be obtained. Due to the constraint, the original model parameters are converted in Leff into φ-dependent classical effective parameters. In particular, the effective potential Ueff(φ) in Leff has the form Ueff = λ/4ξ2MP4· F(φ)·tanh4(√(ξ)φ/MP), where F(φ) is a smooth function equal to F(φ) ≈ 1/2 for φ > 6MP. It is fundamentally important that the constant ξ of non-minimal coupling to the scalar curvature can be chosen small. If ξ = 1/6, then to ensure agreement with CMB observational data, the Higgs field self-coupling parameter λ in the original action must be of the order of ∼ 10-11. During cosmological evolution after the end of inflation, the decrease of φ leads to a change in the sign of the effective Higgs mass term in Leff. This TMSM effect provides an answer to the mystery of the Higgs potential structure and leads to spontaneous symmetry breaking. As φ approaches VEV, the scalar function ζ(φ) changes in such a way that the classical TMT-effective self-coupling parameter λ(ζ(φ)) increases by 10 orders of magnitude compared to λ, which is necessary for the implementation of the GWS theory. Applying the model to the very beginning of the classical evolution of the Universe shows that under certain initial conditions, cosmological dynamics can begin with a “pathological” and even phantom regime preceding inflation. However, if evolution begins with normal dynamics, then it proceeds only as inflation, and the problem of initial conditions for the onset of inflation does not arise. The fermion preheating model is described as a preliminary study of preheatig after inflation. Mathematical and physical arguments in favor of using the TMT are presented.
{"title":"Higgs inflation model with small non-minimal coupling constant","authors":"Alexander B. Kaganovich","doi":"10.1088/1475-7516/2026/03/006","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/006","url":null,"abstract":"The Higgs sector of the Two-Measure Theory (TMT) extension of the electroweak SM (TMSM) is studied in the context of cosmology, where the only non-zero component φ of the cosmologically averaged Higgs field plays the role of the inflaton. The self-consistency of the system of equations obtained from the original action has the form of an algebraic constraint defining the scalar ζ, which is the ratio of two volume measures, as a function of the field φ and its first derivatives. The scalar ζ is present in all equations of motion and has a significant effect on the dynamics of the fields. After the transition in the equations of motion to the Einstein frame with the spatially flat Friedmann metric, it is convenient to describe the resulting system of equations using the action Seff and the Lagrangian Leff, which we call the TMT-effective action and the TMT-effective Lagrangian and from which these equations can be obtained. Due to the constraint, the original model parameters are converted in Leff into φ-dependent classical effective parameters. In particular, the effective potential Ueff(φ) in Leff has the form Ueff = λ/4ξ2MP4· F(φ)·tanh4(√(ξ)φ/MP), where F(φ) is a smooth function equal to F(φ) ≈ 1/2 for φ > 6MP. It is fundamentally important that the constant ξ of non-minimal coupling to the scalar curvature can be chosen small. If ξ = 1/6, then to ensure agreement with CMB observational data, the Higgs field self-coupling parameter λ in the original action must be of the order of ∼ 10-11. During cosmological evolution after the end of inflation, the decrease of φ leads to a change in the sign of the effective Higgs mass term in Leff. This TMSM effect provides an answer to the mystery of the Higgs potential structure and leads to spontaneous symmetry breaking. As φ approaches VEV, the scalar function ζ(φ) changes in such a way that the classical TMT-effective self-coupling parameter λ(ζ(φ)) increases by 10 orders of magnitude compared to λ, which is necessary for the implementation of the GWS theory. Applying the model to the very beginning of the classical evolution of the Universe shows that under certain initial conditions, cosmological dynamics can begin with a “pathological” and even phantom regime preceding inflation. However, if evolution begins with normal dynamics, then it proceeds only as inflation, and the problem of initial conditions for the onset of inflation does not arise. The fermion preheating model is described as a preliminary study of preheatig after inflation. Mathematical and physical arguments in favor of using the TMT are presented.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"14 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147358764","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 : 2026-03-05DOI: 10.1088/1475-7516/2026/03/013
Julian Adamek and Renan Boschetti
Spatial curvature is one of the fundamental cosmological parameters that is routinely constrained from observations. The forward modelling of observations, in particular of large-scale structure, often relies on large cosmological simulations. While the so-called separate universe approach allows one to account for the effect of curvature on the expansion rate in small sub-volumes, the non-Euclidean geometry is harder to accommodate. It becomes important when observables are computed over large distances, e.g. when photons travel to us from high redshift. Here we present a fully relativistic framework to run cosmological simulations for curved spatial geometry. The issue of consistent boundary conditions is solved by embedding a spherical cap of the curved spacetime into a hole within a flat exterior, where it can undergo free expansion. The geometric nature of gravity is made explicit in our framework, allowing for a consistent forward modelling of observables inside the curved patch. Our methodology would also work with any Newtonian code to a good approximation, requiring changes only to the initial conditions and post-processing.
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