Journal of Cosmology and Astroparticle Physics最新文献

{"title":"New analysis of SNeIa Pantheon Catalog: Variable speed of light as an alternative to dark energy","authors":"Hoang Ky Nguyen","doi":"10.1088/1475-7516/2025/04/005","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/04/005","url":null,"abstract":"In ref. [4] Blanchard, Douspis, Rowan-Robinson, and Sarkar (BDRS) slightly modified the primordial fluctuation spectrum and produced an excellent fit to WMAP's CMB power spectrum for an Einstein-de Sitter (EdS) universe, bypassing dark energy. Curiously, they obtained a Hubble value of H0 ≈ 46, in sharp conflict with the canonical range ∼ 67–73. However, we will demonstrate that the reduced value of H0 ≈ 46 achieved by BDRS is fully compatible with the use of variable speed of light in analyzing the late-time cosmic acceleration observed in Type Ia supernovae (SNeIa). In ref. [6] we considered a generic class of scale-invariant actions that allow matter to couple non-minimally with gravity via a dilaton field χ. We discovered a hidden aspect of these actions: the dynamics of the dilaton can induce a variation in the speed of light c as c ∝ χ1/2, thereby causing c to vary alongside χ across spacetime. For an EdS universe with varying c, besides the effects of cosmic expansion, light waves emitted from distant SNeIa are further subject to a refraction effect, which alters the Lemaître redshift relation to 1 + z = a3/2. Based on this new formula, we achieve a fit to the SNeIa Pantheon Catalog exceeding the quality of the ΛCDM model. Crucially, our approach does not require dark energy and produces H0 = 47.2±0.4 (95% CL) in strong alignment with the BDRS finding of H0 ≈ 46. The reduction in H0 in our work, compared with the canonical range ∼ 67–73, arises due to the 3/2-exponent in the modified Lemaître redshift formula. Hence, BDRS's analysis of the (early-time) CMB power spectrum and our variable-c analysis of the (late-time) Hubble diagram of SNeIa fully agree on two counts: (i) the dark energy hypothesis is avoided, and (ii) H0 is reduced to ∼ 47, which also yields an age t0 = 2/(3H0)=13.8Gy for an EdS universe, without requiring dark energy. Most importantly, we will demonstrate that the late-time acceleration can be attributed to the declining speed of light in an expanding EdS universe, rather than to a dark energy component.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"36 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143744934","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}

{"title":"More is different: multi-axion dynamics changes topological defect evolution","authors":"Junseok Lee, Kai Murai, Fuminobu Takahashi and Wen Yin","doi":"10.1088/1475-7516/2025/04/002","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/04/002","url":null,"abstract":"We study topological defects in multi-axion models arising from multiple Peccei-Quinn (PQ) scalars. Using a simplified two-axion system, we reveal fundamental differences in the evolution of these defects compared to single-axion scenarios. This finding is particularly significant because, despite the fact that integrating out heavier axions reduces these models to an effective single PQ scalar theory at low energies, the actual physical behavior of topological defects differs markedly from single-axion predictions. Unlike single-axion models where conventional cosmic strings form, multi-axion scenarios with post-inflationary or mixed initial conditions generically produce networks of strings interconnected by high-tension domain walls. This results in a severe cosmological domain wall problem. We determine string-wall network instability conditions and discuss cosmological implications including the application to the QCD axion and gravitational wave generation. Our findings highlight that multi-axion dynamics can lead to qualitatively different outcomes for topological defects, challenging the conventional picture of cosmic evolution of topological defects based on single-axion models.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"28 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143744932","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}

{"title":"Constraints on long-ranged interactions between dark matter and the Standard Model","authors":"Zachary Bogorad, Peter W. Graham and Harikrishnan Ramani","doi":"10.1088/1475-7516/2025/04/006","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/04/006","url":null,"abstract":"Dark matter's existence is known thanks to its gravitational interaction with Standard Model particles, but it remains unknown whether this is the only force present between them. While many searches for such new interactions with dark matter focus on short-range, contact-like interactions, it is also possible that there exist weak, long-ranged forces between dark matter and the Standard Model. In this work, we present two types of constraints on such new interactions. First, we consider constraints arising from the fact that such a force would also induce long range interactions between Standard Model particles themselves, as well as between dark matter particles themselves. Combining the constraints on these individual forces generally sets the strongest constraints available on new Standard Model-dark matter interactions. Second, we consider the possibility of constraining new long-ranged interactions between dark matter and the Standard Model using the effects of dynamical friction in ultrafaint dwarf galaxies, especially Segue I. Such new interactions would accelerate the transfer of kinetic energy from stars to their surrounding dark matter, slowly reducing their orbits; the present-day stellar half-light radius of Segue I therefore allows us to exclude new forces which would have reduced stars' orbital radii below this scale by now.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"216 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143744935","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}

{"title":"Dark matter freeze-in from non-equilibrium QFT: towards a consistent treatment of thermal effects","authors":"Mathias Becker, Emanuele Copello, Julia Harz and Carlos Tamarit","doi":"10.1088/1475-7516/2025/03/071","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/03/071","url":null,"abstract":"We study thermal corrections to a model of real scalar dark matter (DM) interacting feebly with a SM fermion and a gauge-charged vector-like fermion mediator. We employ the Closed-Time-Path (CTP) formalism for our calculation and go beyond previous works by including the full dependence on the relevant mass scales as opposed to using (non)relativistic approximations. In particular, we calculate the DM production rate by employing 1PI-resummed propagators constructed from the leading order term in the loop expansion of the 2PI effective action, beyond the Hard-Thermal-Loop (HTL) approximation. We compare our findings to commonly used approximation schemes, including solving the Boltzmann equation using momentum-independent thermal masses in decay processes and as regulators for t-channel divergences. We also compare with the result when employing HTL propagators and their tree-level limit. We find that the DM relic abundance when using thermal masses in the Boltzmann approach deviates between -10% and +30% from our calculation, where the size and sign strongly depend on the mass splitting between the DM candidate and the gauge-charged mediator. The HTL-approximated result is more accurate at small gauge couplings, only deviating by a few percent at large mass splittings, whereas it overestimates the relic density up to 25% for small mass splittings. Calculations using tree-level propagators in the CTP formalism or semiclassical Boltzmann equations without scatterings underestimate the dark matter abundance and can lead to deviations of up to -100% from the 1PI-resummed result.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"25 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143733886","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}

{"title":"Multi-messenger cosmology: A route to accurate inference of dark energy beyond CPL parametrization from XG detectors","authors":"Samsuzzaman Afroz and Suvodip Mukherjee","doi":"10.1088/1475-7516/2025/03/070","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/03/070","url":null,"abstract":"One of the central challenges in modern cosmology is understanding the nature of dark energy and its evolution throughout the history of the Universe. Dark energy is commonly modeled as a perfect fluid with a time-varying equation-of-state parameter, w(z), often modeled under CPL parametrization using two parameters w0 and wa. In this study, we explore both parametric and non-parametric methods to reconstruct the dark energy Equation of State (EoS) using Gravitational Wave (GW) sources, with and without electromagnetic (EM) counterparts called bright sirens and dark sirens respectively. In the parametric approach, we extend the widely used w0-wa model by introducing an additional term, wb, to better capture the evolving dynamics of dark energy up to high redshift which is accessible from GW sources. This extension provides increased flexibility in modeling the EoS and enables a more detailed investigation of dark energy's evolution. Our analysis indicates that, with five years of observation time and a 75% duty cycle using Cosmic Explorer and the Einstein Telescope, it will be possible to measure the dark energy EoS with remarkable precision, better than any other cosmological probe in the coming years, from bright standard sirens using a multi-messenger approach. These findings highlight the potential of GW observations in synergy with EM telescopes to offer valuable insights into the nature of dark energy, overcoming the current limitations in cosmological measurements.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"36 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143733885","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}

{"title":"On the virialization threshold for halo mass functions","authors":"Ronaldo C. Batista","doi":"10.1088/1475-7516/2025/03/068","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/03/068","url":null,"abstract":"In a recent study by Euclid collaboration, the Halo Mass Function (HMF) has been fitted with accuracy better than 1% for the ΛCDM model. Several parameters were introduced and fitted against N-body simulations, assuming the usual linearly extrapolated matter density contrast at the collapse time, δc, as a basic threshold for halo formation. As a result, a new function that multiplies δc was introduced, producing an effective threshold that varies both with redshift and mass scale. We show that the redshift evolution of this effective threshold is similar to the one of the linear extrapolated matter density contrast at the virialization time, δv. Assuming the Euclid HMF as a fiducial model, we refit the Sheth-Tormen (ST) HMF using δv as a threshold. This new fit improves the agreement between ST-HMF and the Euclid one with respect to Despali et al. (2016) fit, specially at high masses. Interestingly, the parameters a and p in this refit have values closer to the Press-Schechter limit of the ST-HMF, showing that the use of δv can provide semi-analytical HMF less dependent on extra parameters, while providing better agreement with the Euclid HMF. Moreover, we analyze the consistency of the ST-HMF fitted with δv in smooth dark energy models with time-varying equation of state, finding an overall good agreement with the evolution of halo abundances expected from the linear evolution of perturbations and the Euclid HMF extrapolated to these scenarios. These findings suggest that the use of δv as a basic function to describe the threshold for halo formation can be a good guide when considering extrapolations for models beyond ΛCDM, which are typically harder to study in simulations. We also provide a fitting formula for δv in the ΛCDM model and a code to compute it for smooth dark energy with equation of state described by the w0wa parametrization.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"7 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143733884","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}

{"title":"Geometric reheating of the Universe","authors":"Daniel G. Figueroa and Nicolás Loayza","doi":"10.1088/1475-7516/2025/03/073","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/03/073","url":null,"abstract":"We study the post-inflationary energy transfer from the inflaton (ϕ) into a scalar field (χ) non-minimally coupled to gravity through ξR|χ|2, considering models with inflaton potential Vinf ≈ |ϕ|p around ϕ = 0. This corresponds to the paradigm of geometric preheating, which we extend to its non-linear regime via lattice simulations. Considering α-attractor T-model potentials as a proxy, we study the viability of proper reheating for p = 2, 4, 6, determining whether radiation domination (RD) due to energetic dominance of χ over ϕ, can be achieved. For large inflationary scales Λ, reheating is frustrated for p = 2, it can be partially achieved for p = 4, and it becomes very efficient for p = 6. Efficient reheating can be however blocked if χ sustains self-interactions (unless these are extremely feeble), or if Λ is low enough, so that inflaton fragmentation brings the universe rapidly into RD. Whenever RD is achieved, either due to reheating (into χ) or to inflaton fragmentation, we characterize the energy and time scales of the problem, as a function of Λ and ξ.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"132 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143733890","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}

{"title":"Field-level emulation of cosmic structure formation with cosmology and redshift dependence","authors":"Drew Jamieson, Yin Li, Francisco Villaescusa-Navarro, Shirley Ho and David N. Spergel","doi":"10.1088/1475-7516/2025/03/072","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/03/072","url":null,"abstract":"We present a field-level emulator for large-scale structure, capturing the cosmology dependence and the time evolution of cosmic structure formation. The emulator maps linear displacement fields to their corresponding nonlinear displacements from N-body simulations at specific redshifts. Designed as a neural network, the emulator incorporates style parameters that encode dependencies on Ωm and the linear growth factor D(z) at redshift z. We train our model on the six-dimensional N-body phase space, predicting particle velocities as the time derivative of the model's displacement outputs. This innovation results in significant improvements in training efficiency and model accuracy. Tested on diverse cosmologies and redshifts not seen during training, the emulator achieves percent-level accuracy on scales of k ∼ 1 Mpc-1h at z = 0, with improved performance at higher redshifts. We compare predicted structure formation histories with N-body simulations via merger trees, finding consistent merger event sequences and statistical properties.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"49 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143733887","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}

{"title":"The principled-parameterized approach to gravitational collapse","authors":"Héloïse Delaporte and Astrid Eichhorn","doi":"10.1088/1475-7516/2025/03/074","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/03/074","url":null,"abstract":"New physics beyond General Relativity impacts black-hole spacetimes. The effects of new physics can be investigated in a largely theory-agnostic way by following the principled-parameterized approach. In this approach, a classical black-hole metric is upgraded by following a set of principles, such as regularity, i.e., the absence of curvature singularities. We expect these principles to hold in many theories beyond General Relativity. In the present paper, we implement this approach for time-dependent spacetimes describing gravitational collapse. We find that the Vaidya spacetime becomes regular through the same modification of the spacetime metric as stationary black-hole spacetimes [1–3]. We investigate null geodesics and find indications that the modification is even sufficient to render null geodesics future complete. Finally, we find that the modification of the spacetime structure results in violations of the null energy condition in a finite region inside the apparent horizon of the black hole that forms. Null geodesics are attracted to the boundary of this region, such that the new-physics effects are shielded from asymptotic observers. An exception occurs, if the classical spacetime has a naked singularity. Then, the upgraded spacetime is singularity-free and null geodesics from the regular core can escape towards asymptotic observers.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"30 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143733888","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}

{"title":"On the correlation between Lyα forest opacity and galaxy density in late reionization models","authors":"Nakul Gangolli, Anson D'Aloisio, Christopher Cain, George D. Becker and Holly Christenson","doi":"10.1088/1475-7516/2025/03/069","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/03/069","url":null,"abstract":"Observations of quasar absorption spectra provide strong evidence that reionization extended below z = 6. The relationship between Lyα forest opacity and local galaxy density (the opacity-density relation) is a key observational test of this scenario. Using narrow-band surveys of z ≈ 5.7 Lyα emitters (LAEs) centered on quasar sight lines, ref. [1] showed that two of the most transmissive Lyα forest segments at this redshift intersect under-densities in the galaxy distribution. This result is in tension with models of a strongly fluctuating ionizing background, including some models of late reionization, which predict that the vast majority of these segments should intersect over-densities where the ionizing intensity is strongest. In this paper, we use radiative transfer simulations to explore in more detail the opacity-density relation predicted by late reionization models. We find that fields like the one toward quasar PSO J359-06 — the more under-dense of the two transmissive sight lines in ref. [1] — are typically associated with recently reionized gas inside of cosmic voids where the hotter temperatures and rarefied densities enhance Lyα transmission. The opacity-density relation's transmissive end is sensitive to the amount of neutral gas in the voids, as well as its morphology, set by the clustering of reionization sources. These effects are, however, largely degenerate with each other. We demonstrate that models with very different source clustering can nonetheless yield nearly identical opacity-density relations when their reionization histories are calibrated to match Lyα forest mean flux measurements at z < 6. In models with fixed source clustering, a lower neutral fraction increases the likelihood of intersecting hot, recently reionized gas in the voids, increasing the likelihood of observing fields like PSO J359-06. For instance, the probability of observing this field is 15% in a model with neutral fraction xHI = 5% at z = 5.7, three times more likely than in a model with xHI = 15%. The opacity-density relation may thus provide a complementary probe of reionization's tail end.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"53 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143733987","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}