Pub Date : 2026-02-01DOI: 10.1016/j.dark.2026.102227
J. Lorca Espiro , Yerko Vásquez , M. Le Delliou
Under the existence of a massless spinor with respect to the total connection in a spacetime modeled as a Lorentzian manifold with internal boundaries, such as finite volume semi-classical Black Holes, we show that a topological mechanism naturally induces terms in the Einstein-Cartan gravitational action that can be interpreted as General Relativity with dark energy This may alleviate the problems of dark energy.. The topological information is carried by a harmonic 1-form associated to the first co-holomology group of the spacetime, which induces a spacetime contortion acting on the horizontal bundle.
{"title":"Emergence of dark energy from topology and chiral spinors","authors":"J. Lorca Espiro , Yerko Vásquez , M. Le Delliou","doi":"10.1016/j.dark.2026.102227","DOIUrl":"10.1016/j.dark.2026.102227","url":null,"abstract":"<div><div>Under the existence of a massless spinor with respect to the total connection in a spacetime modeled as a Lorentzian manifold with internal boundaries, such as finite volume semi-classical Black Holes, we show that a topological mechanism naturally induces terms in the Einstein-Cartan gravitational action that can be interpreted as General Relativity with dark energy This may alleviate the problems of dark energy.. The topological information is carried by a harmonic 1-form associated to the first co-holomology group of the spacetime, which induces a spacetime contortion acting on the horizontal bundle.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102227"},"PeriodicalIF":6.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077978","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: 10.1016/j.dark.2026.102235
Yang Cao , Benrong Mu , Jun Tao , Xuetao Yang
This paper explores the observational appearance of black holes surrounded by the Moore dark matter halo, utilizing the celestial sphere and accretion disks as light sources. We can obtain the equations for circular orbits by employing the weak-field expansion approximation of the black hole metric within a Moore dark matter halo. The study explores the variations in the visual characteristics of black holes when observed from different observational points within the celestial sphere model. For both rotating and stationary accretion disks, we investigated the effects of the radius and characteristic density of the Moore dark matter halo on observable phenomena, while examining the angular dependence in both types of disks. Our investigation shows that in rotating accretion disks, the blue shift effect of photons becomes more prominent as the observation angle increases.
{"title":"Images of black holes in the center of Moore dark matter halo","authors":"Yang Cao , Benrong Mu , Jun Tao , Xuetao Yang","doi":"10.1016/j.dark.2026.102235","DOIUrl":"10.1016/j.dark.2026.102235","url":null,"abstract":"<div><div>This paper explores the observational appearance of black holes surrounded by the Moore dark matter halo, utilizing the celestial sphere and accretion disks as light sources. We can obtain the equations for circular orbits by employing the weak-field expansion approximation of the black hole metric within a Moore dark matter halo. The study explores the variations in the visual characteristics of black holes when observed from different observational points within the celestial sphere model. For both rotating and stationary accretion disks, we investigated the effects of the radius and characteristic density of the Moore dark matter halo on observable phenomena, while examining the angular dependence in both types of disks. Our investigation shows that in rotating accretion disks, the blue shift effect of photons becomes more prominent as the observation angle increases.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"52 ","pages":"Article 102235"},"PeriodicalIF":6.4,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146116670","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 : 2026-01-19DOI: 10.1016/j.dark.2026.102232
Miguel Barroso Varela , Álvaro de la Cruz-Dombriz
We provide insight about the full form of the equations for matter density perturbations and the scalar Bardeen metric potentials in general f(R) theories of gravity. When considering viable modifications to the standard ΛCDM background, the full scale-dependent equations for the metric perturbations are provided and are shown to match the ones obtained with the quasistatic approximation. We investigate the impact of the Hu-Sawicki model on the late-time growth of structures. We find that updated late-time growth of structure data imposes and thus conclude that the Hu-Sawicki f(R) model contributes no significant phenomenology at both background and perturbative level beyond the effective cosmological constant encompassed in its definition. This conclusion points to the survival of the present tension between early and late measurements of σ8, as the Hu-Sawicki model can only worsen this issue or at best reproduce the results from the current concordance cosmological model. The generalized perturbative method showcased in this work can be applied to more elaborate f(R) models to isolate genuine higher-order signatures beyond the quasistatic approximation.
{"title":"Implications of f(R) gravity on late-time cosmic structure growth through a complete description of density perturbations","authors":"Miguel Barroso Varela , Álvaro de la Cruz-Dombriz","doi":"10.1016/j.dark.2026.102232","DOIUrl":"10.1016/j.dark.2026.102232","url":null,"abstract":"<div><div>We provide insight about the full form of the equations for matter density perturbations and the scalar Bardeen metric potentials in general <em>f</em>(<em>R</em>) theories of gravity. When considering viable modifications to the standard ΛCDM background, the full scale-dependent equations for the metric perturbations are provided and are shown to match the ones obtained with the quasistatic approximation. We investigate the impact of the <span><math><mrow><mi>n</mi><mo>=</mo><mn>2</mn></mrow></math></span> Hu-Sawicki model on the late-time growth of structures. We find that updated late-time growth of structure data imposes <span><math><mrow><mrow><mo>|</mo></mrow><msub><mi>f</mi><msub><mi>R</mi><mn>0</mn></msub></msub><mrow><mo>|</mo><mo>≲</mo></mrow><msup><mn>10</mn><mrow><mo>−</mo><mn>6</mn></mrow></msup><mo>−</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup></mrow></math></span> and thus conclude that the Hu-Sawicki <em>f</em>(<em>R</em>) model contributes no significant phenomenology at both background and perturbative level beyond the effective cosmological constant encompassed in its definition. This conclusion points to the survival of the present tension between early and late measurements of <em>σ</em><sub>8</sub>, as the Hu-Sawicki model can only worsen this issue or at best reproduce the results from the current concordance cosmological model. The generalized perturbative method showcased in this work can be applied to more elaborate <em>f</em>(<em>R</em>) models to isolate genuine higher-order signatures beyond the quasistatic approximation.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102232"},"PeriodicalIF":6.4,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022823","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 : 2026-01-17DOI: 10.1016/j.dark.2026.102229
Shubham Barua, Shantanu Desai
Recent DESI results indicate a strong preference for dynamical dark energy (DE) when baryon acoustic oscillation (BAO) measurements are combined with supernovae (SNe) and cosmic microwave background (CMB) data using the Chevallier-Polarski-Linder (CPL) parameterization. We analyze the exponential (EXP) parameterization, which introduces a second-order correction to CPL. We determine and compare the 95% upper bounds on the sum of neutrino masses for three dark energy (DE) models—ΛCDM, CPL, and EXP—across four neutrino mass hierarchies (1 massive/2 massless, degenerate, normal, inverted) and multiple dataset combinations (CMB + BAO, CMB + BAO + PantheonPlus, CMB + BAO + DESY5), employing both Bayesian and frequentist frameworks with physical lower limits from oscillation experiments (0.059 eV and 0.11 eV). Our results show that CPL yields tighter ( ≲ 10%) bounds compared to EXP. We further confirm earlier findings that neutrino mass constraints are only mildly sensitive to the assumed hierarchy and that the frequentist bounds are tighter than Bayesian ones. Furthermore, the imposed oscillation lower limits, the datasets used and the DE parameterizations play a crucial role in the inferred cosmological neutrino mass bounds. For the datasets, hierarchies, and DE parameterizations considered, we find no statistically significant evidence for nonzero neutrino mass consistent with oscillation lower limits.
最近的DESI结果表明，当使用Chevallier-Polarski-Linder （CPL）参数化将重子声学振荡（BAO）测量与超新星（SNe）和宇宙微波背景（CMB）数据相结合时，强烈倾向于动态暗能量（DE）。我们分析了指数（EXP）参数化，该参数化引入了二阶校正。我们确定并比较了三种暗能量（DE）模型-ΛCDM， CPL和EXP -跨越四个中微子质量层次（1个质量/2个无质量，简并，正常，反向）和多个数据集组合（CMB + BAO, CMB + BAO + PantheonPlus, CMB + BAO + DESY5）的中微子质量总和的95%上界。采用贝叶斯框架和频率框架，振荡实验的物理下限（0.059 eV和0.11 eV）。我们的结果表明，与EXP相比，CPL产生了更严格的边界（ > 10%）。我们进一步证实了早期的发现，即中微子质量约束对假设的层次结构只有轻微的敏感性，并且频率界比贝叶斯界更严格。此外，强加的振荡下限、使用的数据集和DE参数化在推断的宇宙中微子质量界中起着至关重要的作用。对于考虑的数据集、层次结构和DE参数化，我们没有发现统计上显著的证据表明非零中微子质量与振荡下限一致。
{"title":"Cosmological constraints on neutrino masses in a second-order CPL dark energy model","authors":"Shubham Barua, Shantanu Desai","doi":"10.1016/j.dark.2026.102229","DOIUrl":"10.1016/j.dark.2026.102229","url":null,"abstract":"<div><div>Recent DESI results indicate a strong preference for dynamical dark energy (DE) when baryon acoustic oscillation (BAO) measurements are combined with supernovae (SNe) and cosmic microwave background (CMB) data using the Chevallier-Polarski-Linder (CPL) parameterization. We analyze the exponential (EXP) parameterization, which introduces a second-order correction to CPL. We determine and compare the 95% upper bounds on the sum of neutrino masses for three dark energy (DE) models—ΛCDM, CPL, and EXP—across four neutrino mass hierarchies (1 massive/2 massless, degenerate, normal, inverted) and multiple dataset combinations (CMB + BAO, CMB + BAO + PantheonPlus, CMB + BAO + DESY5), employing both Bayesian and frequentist frameworks with physical lower limits from oscillation experiments (0.059 eV and 0.11 eV). Our results show that CPL yields tighter ( ≲ 10%) bounds compared to EXP. We further confirm earlier findings that neutrino mass constraints are only mildly sensitive to the assumed hierarchy and that the frequentist bounds are tighter than Bayesian ones. Furthermore, the imposed oscillation lower limits, the datasets used and the DE parameterizations play a crucial role in the inferred cosmological neutrino mass bounds. For the datasets, hierarchies, and DE parameterizations considered, we find no statistically significant evidence for nonzero neutrino mass consistent with oscillation lower limits.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102229"},"PeriodicalIF":6.4,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022821","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 : 2026-01-16DOI: 10.1016/j.dark.2026.102225
Yu-Xiang Huang , Sen Guo , En-Wei Liang , Kai Lin
Understanding how dark matter affects the immediate environment of black holes (BHs) is crucial for interpreting horizon-scale observations. We study rotating BHs surrounded by perfect fluid dark matter (PFDM), exploring their observable features through both analytical and numerical approaches. Using the existence criterion of the innermost stable circular orbit (ISCO), we first derive joint constraints on the PFDM intensity parameter k and the spin parameter a. Within the resulting physically allowed parameter regime, we perform high-resolution, general-relativistic ray-tracing simulations of thin accretion disks at 87 GHz and 230 GHz, capturing the detailed brightness morphology and photon ring structure shaped by PFDM. By incorporating angular diameter measurements of M87* and Sgr A* from the Event Horizon Telescope (EHT), we further narrow down the viable parameter space and directly compare synthetic images with EHT observations of M87*. We find that the inclusion of PFDM improves the agreement with the observed compact shadow and asymmetric brightness distribution, suggesting that dark matter may leave observable imprints on horizon-scale images. Our results position PFDM as a physically motivated extension to the Kerr geometry and highlight a promising astrophysical pathway for probing dark matter near BHs with current and future VLBI campaigns.
{"title":"Impact of perfect fluid dark matter on the appearance of rotating black hole","authors":"Yu-Xiang Huang , Sen Guo , En-Wei Liang , Kai Lin","doi":"10.1016/j.dark.2026.102225","DOIUrl":"10.1016/j.dark.2026.102225","url":null,"abstract":"<div><div>Understanding how dark matter affects the immediate environment of black holes (BHs) is crucial for interpreting horizon-scale observations. We study rotating BHs surrounded by perfect fluid dark matter (PFDM), exploring their observable features through both analytical and numerical approaches. Using the existence criterion of the innermost stable circular orbit (ISCO), we first derive joint constraints on the PFDM intensity parameter <em>k</em> and the spin parameter <em>a</em>. Within the resulting physically allowed parameter regime, we perform high-resolution, general-relativistic ray-tracing simulations of thin accretion disks at 87 GHz and 230 GHz, capturing the detailed brightness morphology and photon ring structure shaped by PFDM. By incorporating angular diameter measurements of M87* and Sgr A* from the Event Horizon Telescope (EHT), we further narrow down the viable parameter space and directly compare synthetic images with EHT observations of M87*. We find that the inclusion of PFDM improves the agreement with the observed compact shadow and asymmetric brightness distribution, suggesting that dark matter may leave observable imprints on horizon-scale images. Our results position PFDM as a physically motivated extension to the Kerr geometry and highlight a promising astrophysical pathway for probing dark matter near BHs with current and future VLBI campaigns.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102225"},"PeriodicalIF":6.4,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022830","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 : 2026-01-16DOI: 10.1016/j.dark.2026.102224
Wei Yang , Yu-Xuan Kang , Arshad Ali , Tao-Tao Sui , Chen-Hao Wu , Ya-Peng Hu
Scalar perturbations in the inflation can be amplified when the base inflation potential Vb(ϕ) incorporates a local bump f(ϕ) such as . This modification will lead to a peak in the curvature power spectrum, increasing a significant abundance of primordial black holes (PBHs). However, since there is no underlying physical reason for the choice of f(ϕ), it is essential to investigate the effects of various bump functions on PBH generation. In this paper, we choose the well-known Starobinsky potential as the base inflation potential to compare the effects produced by different bumps, specifically focusing on the Lorentz and Gaussian bumps which are widely used. To clearly illustrate the differences between these two bumps, we keep parameters in bump functions the same. We find an interesting and novel result that the Lorentz cases manifest a stronger ability to enhance the power spectrum and produce more abundance of PBHs than Gaussian cases. Moreover, we also investigate the different effects of bump functions on the scalar-induced gravitational waves (SIGWs). The results indicate that the Lorentz bump generates SIGWs with a higher energy density, which can be potentially detected in the future. Our study gives valuable insights into the choice and constraints on the bump functions, and the different effects may distinguish the two bump cases for practical purposes in future experiments.
{"title":"Different effects of the Lorentz and Gaussian bump functions on the formation of primordial black holes and secondary gravitational waves","authors":"Wei Yang , Yu-Xuan Kang , Arshad Ali , Tao-Tao Sui , Chen-Hao Wu , Ya-Peng Hu","doi":"10.1016/j.dark.2026.102224","DOIUrl":"10.1016/j.dark.2026.102224","url":null,"abstract":"<div><div>Scalar perturbations in the inflation can be amplified when the base inflation potential <em>V<sub>b</sub></em>(<em>ϕ</em>) incorporates a local bump <em>f</em>(<em>ϕ</em>) such as <span><math><mrow><mi>V</mi><mrow><mo>(</mo><mi>ϕ</mi><mo>)</mo></mrow><mo>=</mo><msub><mi>V</mi><mi>b</mi></msub><mrow><mo>(</mo><mi>ϕ</mi><mo>)</mo></mrow><mrow><mo>(</mo><mn>1</mn><mo>+</mo><mi>f</mi><mrow><mo>(</mo><mi>ϕ</mi><mo>)</mo></mrow><mo>)</mo></mrow></mrow></math></span>. This modification will lead to a peak in the curvature power spectrum, increasing a significant abundance of primordial black holes (PBHs). However, since there is no underlying physical reason for the choice of <em>f</em>(<em>ϕ</em>), it is essential to investigate the effects of various bump functions on PBH generation. In this paper, we choose the well-known Starobinsky potential as the base inflation potential to compare the effects produced by different bumps, specifically focusing on the Lorentz and Gaussian bumps which are widely used. To clearly illustrate the differences between these two bumps, we keep parameters in bump functions the same. We find an interesting and novel result that the Lorentz cases manifest a stronger ability to enhance the power spectrum and produce more abundance of PBHs than Gaussian cases. Moreover, we also investigate the different effects of bump functions on the scalar-induced gravitational waves (SIGWs). The results indicate that the Lorentz bump generates SIGWs with a higher energy density, which can be potentially detected in the future. Our study gives valuable insights into the choice and constraints on the bump functions, and the different effects may distinguish the two bump cases for practical purposes in future experiments.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102224"},"PeriodicalIF":6.4,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022831","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 : 2026-01-16DOI: 10.1016/j.dark.2026.102223
Vishnu S Namboothiri , Krishna P․B․ , Adithya P․S․ , Titus K Mathew
Taking account of the thermal nature of the Hubble horizon of the expanding universe, we analysed the evolution of relative fluctuations of horizon energy. For this analysis, we used two approaches: (i) by treating the Hubble horizon as a system in canonical ensemble, and (ii) by considering the microscopic degrees of freedom on the horizon. In both approaches, we obtained the relative fluctuations by using two different definitions of the horizon temperature; first, the Gibbons-Hawking temperature, and second, the Kodama-Hayward temperature. For a given temperature, both approaches yield the same general evolution for the fluctuations. In the asymptotic limit, the relative energy fluctuations corresponding to the Gibbons-Hawking temperature, is [ℏG/2π]H2, and 2/Nsur for the first and second approaches respectively. Similarly, using the Kodama-Hayward temperature, the asymptotic fluctuations are [5ℏG/2π]H2, and 10/Nsur. This implies that, the magnitude of the relative fluctuations of the horizon energy is higher in the case of Kodama-Hayward temperature. The inverse dependence of the fluctuation on Nsur, the number of degrees of freedom on the horizon, reflects a familiar behaviour in ordinary thermal systems: fluctuations decrease as the number of degrees of freedom increases. Notably, we also found that the relative energy fluctuations establish a connection between the Planck length scale Lp, characteristic length scale of the very early epoch of the universe, and the length scale associated with the late-time accelerated phase. This relationship can offer valuable insights that could help in addressing the cosmological constant problem.
{"title":"Evolution of fluctuations in horizon energy and its dependence on the degrees of freedom","authors":"Vishnu S Namboothiri , Krishna P․B․ , Adithya P․S․ , Titus K Mathew","doi":"10.1016/j.dark.2026.102223","DOIUrl":"10.1016/j.dark.2026.102223","url":null,"abstract":"<div><div>Taking account of the thermal nature of the Hubble horizon of the expanding universe, we analysed the evolution of relative fluctuations of horizon energy. For this analysis, we used two approaches: (i) by treating the Hubble horizon as a system in canonical ensemble, and (ii) by considering the microscopic degrees of freedom on the horizon. In both approaches, we obtained the relative fluctuations by using two different definitions of the horizon temperature; first, the Gibbons-Hawking temperature, and second, the Kodama-Hayward temperature. For a given temperature, both approaches yield the same general evolution for the fluctuations. In the asymptotic limit, the relative energy fluctuations corresponding to the Gibbons-Hawking temperature, is [ℏ<em>G</em>/2<em>π</em>]<em>H</em><sup>2</sup>, and 2/<em>N<sub>sur</sub></em> for the first and second approaches respectively. Similarly, using the Kodama-Hayward temperature, the asymptotic fluctuations are [5ℏ<em>G</em>/2<em>π</em>]<em>H</em><sup>2</sup>, and 10/<em>N<sub>sur</sub></em>. This implies that, the magnitude of the relative fluctuations of the horizon energy is higher in the case of Kodama-Hayward temperature. The inverse dependence of the fluctuation on <em>N<sub>sur</sub></em>, the number of degrees of freedom on the horizon, reflects a familiar behaviour in ordinary thermal systems: fluctuations decrease as the number of degrees of freedom increases. Notably, we also found that the relative energy fluctuations establish a connection between the Planck length scale <em>L<sub>p</sub></em>, characteristic length scale of the very early epoch of the universe, and <span><math><mrow><msqrt><mrow><mn>3</mn><mo>/</mo><mstyle><mi>Λ</mi></mstyle></mrow></msqrt><mo>,</mo></mrow></math></span> the length scale associated with the late-time accelerated phase. This relationship can offer valuable insights that could help in addressing the cosmological constant problem.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102223"},"PeriodicalIF":6.4,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022825","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 : 2026-01-16DOI: 10.1016/j.dark.2026.102226
Agripino Sousa-Neto , Maria Aldinêz Dantas , Javier E. González , Joel C. Carvalho , Jailson Alcaniz
The Universe consists of a variety of objects that formed at different epochs, leading to variations in the formation time which represents the time elapsed from the onset of structure formation until the formation of a particular object. In this work, we present two approaches to reconstruct and constrain the galaxy formation time tf(z) using non-parametric reconstruction methods, such as Gaussian Processes (GP) and High-performance Symbolic Regression (SR). Our analysis uses age estimates of 32 old passive galaxies and the Pantheon+ type Ia supernova sample, and considers two different values of the Hubble constant H0 from the SH0ES and Planck Collaborations. When adopting the ΛCDM model and the GP reconstructions, A direct comparison of the reconstructions shows that the GP-based implementations are mutually consistent across the redshift range considered. The SR reconstructions also show good agreement with the GP results and exhibit a compatible redshift evolution of tf(z), with full agreement at intermediate and high redshifts and only a mild deviation at very low redshifts. The results also show significant differences in the formation time from SH0ES and Planck values, highlighting the impact of the H0 tension on the cosmological estimates of tf(z). Overall, this study suggests that galaxies have different evolutionary timescales and that tf is not constant, with noticeable variations at lower redshifts (z ≲ 0.5).
{"title":"Exploring cosmological constraints on galaxy formation time","authors":"Agripino Sousa-Neto , Maria Aldinêz Dantas , Javier E. González , Joel C. Carvalho , Jailson Alcaniz","doi":"10.1016/j.dark.2026.102226","DOIUrl":"10.1016/j.dark.2026.102226","url":null,"abstract":"<div><div>The Universe consists of a variety of objects that formed at different epochs, leading to variations in the formation time which represents the time elapsed from the onset of structure formation until the formation of a particular object. In this work, we present two approaches to reconstruct and constrain the galaxy formation time <em>t<sub>f</sub></em>(<em>z</em>) using non-parametric reconstruction methods, such as Gaussian Processes (GP) and High-performance Symbolic Regression (SR). Our analysis uses age estimates of 32 old passive galaxies and the Pantheon+ type Ia supernova sample, and considers two different values of the Hubble constant <em>H</em><sub>0</sub> from the SH0ES and Planck Collaborations. When adopting the ΛCDM model and the GP reconstructions, A direct comparison of the reconstructions shows that the GP-based implementations are mutually consistent across the redshift range considered. The SR reconstructions also show good agreement with the GP results and exhibit a compatible redshift evolution of <em>t<sub>f</sub></em>(<em>z</em>), with full agreement at intermediate and high redshifts and only a mild deviation at very low redshifts. The results also show significant differences in the formation time from SH0ES and Planck values, highlighting the impact of the <em>H</em><sub>0</sub> tension on the cosmological estimates of <em>t<sub>f</sub></em>(<em>z</em>). Overall, this study suggests that galaxies have different evolutionary timescales and that <em>t<sub>f</sub></em> is not constant, with noticeable variations at lower redshifts (<em>z</em> ≲ 0.5).</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102226"},"PeriodicalIF":6.4,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022826","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 : 2026-01-14DOI: 10.1016/j.dark.2026.102217
Heng-Sen Jiao , Hong-Bo Jin , Yun-Long Zhang
We investigate a framework for extracting parameters of stochastic gravitational wave background (SGWB) with peak-like templates in the millihertz frequency band, and we analyze transient contamination effects on parameter reconstruction. We present the spectrum and spectrogram under different conditions and provide the results of parameter reconstruction. Using templates from the early universe, we demonstrate that the peak-like templates outperform the broken power law (BPL) templates in power-law exponents recovery and peak frequency localization. The reconstruction results obtained using data from Fast Fourier Transform (FFT) are better than those obtained using data from Short-Time Fourier Transform (STFT) which is based on the spectrogram. For the single-peak(SP) template, the estimation accuracy of the exponent and peak frequency surpasses that of the BPL template by an order of magnitude, but it demonstrates less precision in amplitude estimation compared to the BPL template. Regarding the double-peak template, parameter estimation results derived from the FFT methodology consistently outperform those obtained using STFT. Nevertheless, transient signals exhibit a detrimental impact on parameter estimation precision, causing errors to increase by an order of magnitude, particularly in multi-peak scenarios. This framework provides an example of using templates to analyze data from space-based gravitational wave detectors.
{"title":"Parameter extraction of the stochastic gravitational wave background with peak-like templates in millihertz","authors":"Heng-Sen Jiao , Hong-Bo Jin , Yun-Long Zhang","doi":"10.1016/j.dark.2026.102217","DOIUrl":"10.1016/j.dark.2026.102217","url":null,"abstract":"<div><div>We investigate a framework for extracting parameters of stochastic gravitational wave background (SGWB) with peak-like templates in the millihertz frequency band, and we analyze transient contamination effects on parameter reconstruction. We present the spectrum and spectrogram under different conditions and provide the results of parameter reconstruction. Using templates from the early universe, we demonstrate that the peak-like templates outperform the broken power law (BPL) templates in power-law exponents recovery and peak frequency localization. The reconstruction results obtained using data from Fast Fourier Transform (FFT) are better than those obtained using data from Short-Time Fourier Transform (STFT) which is based on the spectrogram. For the single-peak(SP) template, the estimation accuracy of the exponent and peak frequency surpasses that of the BPL template by an order of magnitude, but it demonstrates less precision in amplitude estimation compared to the BPL template. Regarding the double-peak template, parameter estimation results derived from the FFT methodology consistently outperform those obtained using STFT. Nevertheless, transient signals exhibit a detrimental impact on parameter estimation precision, causing errors to increase by an order of magnitude, particularly in multi-peak scenarios. This framework provides an example of using templates to analyze data from space-based gravitational wave detectors.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102217"},"PeriodicalIF":6.4,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022827","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 : 2026-01-14DOI: 10.1016/j.dark.2026.102214
K. El Bourakadi , M. Yu Khlopov , M. Krasnov , H. Chakir , M. Bennai
We explore how inflationary features shape the early stages of cosmic structure formation. Using the transfer function formalism, we trace the evolution of primordial perturbations, showing how causal physics and oscillatory signatures from inflation influence the matter power spectrum. The variance of smoothed density fields is then applied to model the collapse of overdense regions and predict dark matter halo abundances through the Press–Schechter framework. Extending to the baryonic sector, we analyze primordial gas collapse in minihalos, emphasizing molecular hydrogen cooling and the thermochemical pathways leading to Population III star formation. Finally, we examine primordial black holes as potential seeds for early galaxies, connecting their accretion-driven growth to the stellar masses and disk properties of high-redshift systems. Our results indicate that oscillatory features from inflation can leave measurable imprints on halo abundances and early galaxy properties, providing a testable link between high-energy physics and astrophysical observations with JWST.
{"title":"Tracing inflationary imprints through the dark ages: Implications for early stars and galaxies formation","authors":"K. El Bourakadi , M. Yu Khlopov , M. Krasnov , H. Chakir , M. Bennai","doi":"10.1016/j.dark.2026.102214","DOIUrl":"10.1016/j.dark.2026.102214","url":null,"abstract":"<div><div>We explore how inflationary features shape the early stages of cosmic structure formation. Using the transfer function formalism, we trace the evolution of primordial perturbations, showing how causal physics and oscillatory signatures from inflation influence the matter power spectrum. The variance of smoothed density fields is then applied to model the collapse of overdense regions and predict dark matter halo abundances through the Press–Schechter framework. Extending to the baryonic sector, we analyze primordial gas collapse in minihalos, emphasizing molecular hydrogen cooling and the thermochemical pathways leading to Population III star formation. Finally, we examine primordial black holes as potential seeds for early galaxies, connecting their accretion-driven growth to the stellar masses and disk properties of high-redshift systems. Our results indicate that oscillatory features from inflation can leave measurable imprints on halo abundances and early galaxy properties, providing a testable link between high-energy physics and astrophysical observations with JWST.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"51 ","pages":"Article 102214"},"PeriodicalIF":6.4,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022822","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}
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