Pub Date : 2026-02-06DOI: 10.1088/1475-7516/2026/02/020
Federico Cima and Francesco D'Eramo
Observations of the hydrogen hyperfine transition through the 21 cm line near the end of the cosmic dark ages provide unique opportunities to probe new physics. In this work, we investigate the potential of the sky-averaged 21 cm signal to constrain metastable particles produced in the early universe that decay at later times, thereby modifying the thermal and ionization history of the intergalactic medium. The study begins by extending previous analyses of decaying dark matter (DM), incorporating back-reaction effects and tightening photon decay constraints down to DM masses as low as 20.4 eV. The focus then shifts to non-minimal dark sectors with multiple interacting components. The analysis covers two key scenarios: a hybrid setup comprising a stable cold DM component alongside a metastable sub-component, and a two-component dark sector of nearly degenerate states with a metastable heavier partner. A general parameterization based on effective mass spectra and fractional densities allows for a model-independent study. The final part presents two explicit realizations: an axion-like particle coupled to photons, and pseudo-Dirac DM interacting via vector portals or electromagnetic dipoles. These scenarios illustrate how 21 cm cosmology can set leading bounds and probe otherwise inaccessible regions of parameter space.
{"title":"Probing non-minimal dark sectors via the 21 cm line at cosmic dawn","authors":"Federico Cima and Francesco D'Eramo","doi":"10.1088/1475-7516/2026/02/020","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/020","url":null,"abstract":"Observations of the hydrogen hyperfine transition through the 21 cm line near the end of the cosmic dark ages provide unique opportunities to probe new physics. In this work, we investigate the potential of the sky-averaged 21 cm signal to constrain metastable particles produced in the early universe that decay at later times, thereby modifying the thermal and ionization history of the intergalactic medium. The study begins by extending previous analyses of decaying dark matter (DM), incorporating back-reaction effects and tightening photon decay constraints down to DM masses as low as 20.4 eV. The focus then shifts to non-minimal dark sectors with multiple interacting components. The analysis covers two key scenarios: a hybrid setup comprising a stable cold DM component alongside a metastable sub-component, and a two-component dark sector of nearly degenerate states with a metastable heavier partner. A general parameterization based on effective mass spectra and fractional densities allows for a model-independent study. The final part presents two explicit realizations: an axion-like particle coupled to photons, and pseudo-Dirac DM interacting via vector portals or electromagnetic dipoles. These scenarios illustrate how 21 cm cosmology can set leading bounds and probe otherwise inaccessible regions of parameter space.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"30 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-06DOI: 10.1088/1475-7516/2026/02/022
Zhiyao Lu, Lian-Tao Wang and Huangyu Xiao
We use the precision measurements of the arrival time differences of the same fast radio burst (FRB) source along multiple sightlines to measure the primordial power spectrum and Non-Gaussianities. The anticipated experiment requires a sightline separation of 100 AU, achieved by sending three or more radio telescopes to the outer solar system. The Shapiro time delays, measured relatively between different telescopes, are sensitive to the gradient field of the gravitational potential between different sightlines. Since the arrival time difference is independent of when the transient signal is emitted from the source, every measurement of the detected FRB source can be correlated. With enough FRB sources discovered, we can map the gravitational potential across the sky. We further calculate the two-point and three-point correlation function of the arrival time difference between telescopes for different FRB sources in the sky. If 104 FRBs were to be detected, our results suggest that this technique can test the inflationary scale-invariant power spectrum down to ∼ 103 Mpc-1 and primordial Non-Gaussianities at a level of fNL ∼ 1.
{"title":"Probing primordial power spectrum and non-Gaussianities with fast radio bursts","authors":"Zhiyao Lu, Lian-Tao Wang and Huangyu Xiao","doi":"10.1088/1475-7516/2026/02/022","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/022","url":null,"abstract":"We use the precision measurements of the arrival time differences of the same fast radio burst (FRB) source along multiple sightlines to measure the primordial power spectrum and Non-Gaussianities. The anticipated experiment requires a sightline separation of 100 AU, achieved by sending three or more radio telescopes to the outer solar system. The Shapiro time delays, measured relatively between different telescopes, are sensitive to the gradient field of the gravitational potential between different sightlines. Since the arrival time difference is independent of when the transient signal is emitted from the source, every measurement of the detected FRB source can be correlated. With enough FRB sources discovered, we can map the gravitational potential across the sky. We further calculate the two-point and three-point correlation function of the arrival time difference between telescopes for different FRB sources in the sky. If 104 FRBs were to be detected, our results suggest that this technique can test the inflationary scale-invariant power spectrum down to ∼ 103 Mpc-1 and primordial Non-Gaussianities at a level of fNL ∼ 1.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"107 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-06DOI: 10.1088/1475-7516/2026/02/018
Katsuki Aoki, Tomohiro Fujita, Ryodai Kawaguchi and Kazuki Yanagihara
When a (non-)Abelian gauge field acquires an isotropic background configuration during inflation, strong gravitational waves (GWs) with parity-violating polarization, known as chiral GWs, can be produced in addition to the intrinsic unpolarized GWs. However, previous studies have analyzed individual models, leaving the generality of this phenomenon unclear. To perform a model-independent analysis, we construct an effective field theory (EFT) of chiral GWs by extending the EFT of inflation and incorporating gauge fields. The resulting action unifies inflationary models with a SU(2) gauge field, such as chromo-natural inflation and gauge-flation, and ones with a triplet of U(1) gauge fields, systematically encompassing all possible GW production mechanisms consistent with the symmetry breaking induced by the gauge field background. We find that chiral GWs are generically and inevitably produced, provided that the effective energy density of the background gauge field is positive and the gauge kinetic function is not fine-tuned to a specific time dependence. This EFT offers a useful foundation for future phenomenological studies as well as for deepening our theoretical understanding of chiral GWs.
{"title":"Effective field theory of chiral gravitational waves","authors":"Katsuki Aoki, Tomohiro Fujita, Ryodai Kawaguchi and Kazuki Yanagihara","doi":"10.1088/1475-7516/2026/02/018","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/018","url":null,"abstract":"When a (non-)Abelian gauge field acquires an isotropic background configuration during inflation, strong gravitational waves (GWs) with parity-violating polarization, known as chiral GWs, can be produced in addition to the intrinsic unpolarized GWs. However, previous studies have analyzed individual models, leaving the generality of this phenomenon unclear. To perform a model-independent analysis, we construct an effective field theory (EFT) of chiral GWs by extending the EFT of inflation and incorporating gauge fields. The resulting action unifies inflationary models with a SU(2) gauge field, such as chromo-natural inflation and gauge-flation, and ones with a triplet of U(1) gauge fields, systematically encompassing all possible GW production mechanisms consistent with the symmetry breaking induced by the gauge field background. We find that chiral GWs are generically and inevitably produced, provided that the effective energy density of the background gauge field is positive and the gauge kinetic function is not fine-tuned to a specific time dependence. This EFT offers a useful foundation for future phenomenological studies as well as for deepening our theoretical understanding of chiral GWs.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"72 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-06DOI: 10.1088/1475-7516/2026/02/024
Odelia V. Hartl, Evan Vienneau, Evan Batteas, Addy J. Evans, Nassim Bozorgnia and Louis E. Strigari
We examine velocity-dependent dark matter annihilation in subhalos using a sample of six Milky Way-like galaxies from the Aurgia simulation suite. We quantify the enhancement in the annihilation rate in subhalos when including the contribution from particles in the smooth component of the halo that overlap with the subhalos. The enhancement in the annihilation rate scales with the smooth component of the host halo dark matter density, and is evident for subhalos over the resolvable mass range. Maximal enhancement factors are ∼ 48 for p-wave models, and ∼ 37,000 for d-wave models. For p and d-wave annihilation models, ∼ 13 and ∼ 6 subhalos, respectively, across all six host halos have emission from dark matter annihilation in their direction that is above the foreground emission from the smooth dark matter component, and would therefore be resolvable as sources. Such subhalos with the most significant enhancement factors tend to be on the lower end of the mass range and located closer to the center of the host galaxy. We provide a prescription to calculate the enhancement for subhalos as a function of distance from the Galactic center, and use this to examine the impact on dark matter limits from a couple of example dwarf spheroidals. We show that, including the enhancement factors, limits from individual dwarf spheroidals are at a cross section scale that may approach those derived from the Galactic center.
{"title":"Enhancements in velocity-dependent dark matter annihilation in Galactic subhalos","authors":"Odelia V. Hartl, Evan Vienneau, Evan Batteas, Addy J. Evans, Nassim Bozorgnia and Louis E. Strigari","doi":"10.1088/1475-7516/2026/02/024","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/024","url":null,"abstract":"We examine velocity-dependent dark matter annihilation in subhalos using a sample of six Milky Way-like galaxies from the Aurgia simulation suite. We quantify the enhancement in the annihilation rate in subhalos when including the contribution from particles in the smooth component of the halo that overlap with the subhalos. The enhancement in the annihilation rate scales with the smooth component of the host halo dark matter density, and is evident for subhalos over the resolvable mass range. Maximal enhancement factors are ∼ 48 for p-wave models, and ∼ 37,000 for d-wave models. For p and d-wave annihilation models, ∼ 13 and ∼ 6 subhalos, respectively, across all six host halos have emission from dark matter annihilation in their direction that is above the foreground emission from the smooth dark matter component, and would therefore be resolvable as sources. Such subhalos with the most significant enhancement factors tend to be on the lower end of the mass range and located closer to the center of the host galaxy. We provide a prescription to calculate the enhancement for subhalos as a function of distance from the Galactic center, and use this to examine the impact on dark matter limits from a couple of example dwarf spheroidals. We show that, including the enhancement factors, limits from individual dwarf spheroidals are at a cross section scale that may approach those derived from the Galactic center.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"224 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-06DOI: 10.1088/1475-7516/2026/02/019
Yo Toda and Osamu Seto
Primarily motivated by the Hubble tension, we analyze the varying electron mass model and axionlike early dark energy model (EDE) using baryon acoustic oscillation data from DESI DR2 data and including the recent results from ACT DR6. Our analysis indicates that me/me0 = 1.0078 ± 0.0047 in the varying me model, me/me0 = 1.0034 ± 0.0050 and α/α0 = 1.0039 ± 0.0016 in the varying me+α model, and the energy fraction of EDE is constrained as fEDE < 0.014. Since those cosmological models fit with different spectral index ns, we show the posterior of those models on the (ns-r) plane and point out that, for example, Starobinsky inflation works for varying electron mass model while the standard supersymmetric hybrid inflation is preferred in the EDE model.
{"title":"Constraints on the varying electron mass and early dark energy in light of ACT DR6 and DESI DR2 and the implications for inflation","authors":"Yo Toda and Osamu Seto","doi":"10.1088/1475-7516/2026/02/019","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/019","url":null,"abstract":"Primarily motivated by the Hubble tension, we analyze the varying electron mass model and axionlike early dark energy model (EDE) using baryon acoustic oscillation data from DESI DR2 data and including the recent results from ACT DR6. Our analysis indicates that me/me0 = 1.0078 ± 0.0047 in the varying me model, me/me0 = 1.0034 ± 0.0050 and α/α0 = 1.0039 ± 0.0016 in the varying me+α model, and the energy fraction of EDE is constrained as fEDE < 0.014. Since those cosmological models fit with different spectral index ns, we show the posterior of those models on the (ns-r) plane and point out that, for example, Starobinsky inflation works for varying electron mass model while the standard supersymmetric hybrid inflation is preferred in the EDE model.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"6 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-06DOI: 10.1088/1475-7516/2026/02/023
Yun Wang and Katherine Freese
Using DESI DR2 baryon acoustic oscillation (BAO) distance measurements and Planck cosmic microwave background distance priors, we have measured the dark energy density ρX(z) and dark energy equation of state wX(z) as free functions of redshift (smoothly interpolated from values at {zi}={0, 1/3, 2/3, 1, 4/3, 2.33}), and find both to be consistent with a cosmological constant, with only deviations of ∼ 1σ for ρX(z) and ∼ 2σ for wX(z) at z = 2/3. We also find that measuring {ρX(zi)} is preferred to measuring {wX(zi)} by model selection using the Akaike Information Criterion (AIC) as well as the Bayesian Information Criterion (BIC); we confirm our earlier finding in Wang & Freese (2006) that wX(z) is significantly less constrained by data than ρX(z). We show that varying the choice of redshift values of the ρX(z) measurements leads to very consistent results, with AIC/BIC slightly favoring the case of our fiducial redshifts {zi} but with z = 4/3 omitted. We find agreement with a cosmological constant except for the 1–2σ deviation at 0.4 ≲ z ≲ 0.9, where DESI DR2 BAO measurements deviate from a cosmological constant at similar statistical significance. Our results differ noticeably from those of the DESI Collaboration, in which they used the same DESI DR2 data combined with Planck data and found a 3.1σ deviation from a cosmological constant, a finding which is primarily the consequence of their assuming the parametrization wX(z) = w0+wa(1-a). Our results indicate that assuming a linear wX(z) could be misleading and precludes discovering how dark energy actually varies with time at higher redshifts. In our quest to discover the physical nature of dark energy, the most urgent goal at present is to determine definitively whether dark energy density varies with time. We have demonstrated that it is of critical importance to measure dark energy density as a free function of redshift from data. Future galaxy redshift surveys by Euclid and Roman at higher redshifts will significantly advance our understanding of dark energy.
{"title":"Model-independent dark energy measurements from DESI DR2 and Planck 2015 data","authors":"Yun Wang and Katherine Freese","doi":"10.1088/1475-7516/2026/02/023","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/023","url":null,"abstract":"Using DESI DR2 baryon acoustic oscillation (BAO) distance measurements and Planck cosmic microwave background distance priors, we have measured the dark energy density ρX(z) and dark energy equation of state wX(z) as free functions of redshift (smoothly interpolated from values at {zi}={0, 1/3, 2/3, 1, 4/3, 2.33}), and find both to be consistent with a cosmological constant, with only deviations of ∼ 1σ for ρX(z) and ∼ 2σ for wX(z) at z = 2/3. We also find that measuring {ρX(zi)} is preferred to measuring {wX(zi)} by model selection using the Akaike Information Criterion (AIC) as well as the Bayesian Information Criterion (BIC); we confirm our earlier finding in Wang & Freese (2006) that wX(z) is significantly less constrained by data than ρX(z). We show that varying the choice of redshift values of the ρX(z) measurements leads to very consistent results, with AIC/BIC slightly favoring the case of our fiducial redshifts {zi} but with z = 4/3 omitted. We find agreement with a cosmological constant except for the 1–2σ deviation at 0.4 ≲ z ≲ 0.9, where DESI DR2 BAO measurements deviate from a cosmological constant at similar statistical significance. Our results differ noticeably from those of the DESI Collaboration, in which they used the same DESI DR2 data combined with Planck data and found a 3.1σ deviation from a cosmological constant, a finding which is primarily the consequence of their assuming the parametrization wX(z) = w0+wa(1-a). Our results indicate that assuming a linear wX(z) could be misleading and precludes discovering how dark energy actually varies with time at higher redshifts. In our quest to discover the physical nature of dark energy, the most urgent goal at present is to determine definitively whether dark energy density varies with time. We have demonstrated that it is of critical importance to measure dark energy density as a free function of redshift from data. Future galaxy redshift surveys by Euclid and Roman at higher redshifts will significantly advance our understanding of dark energy.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"30 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-05DOI: 10.1088/1475-7516/2026/02/e01
A.A. Araújo Filho
In a recent analysis presented in ref. [1], the particle creation process, the evaporation lifetimes, and the greybody bounds for the metric andmetric-affine formulations were examined. Some aspects require correction: a typo in ref. [2] concerning the black hole shadow radii affected the evaporation-lifetime and emission-rate results for the metric-affine case of the previous work, and the computational routine employed in ref. [1] introduced errors in the greybody bounds for tensor perturbations and in the bounds analysis.
{"title":"Erratum: How does non-metricity affect particle creation and evaporation in bumblebee gravity?","authors":"A.A. Araújo Filho","doi":"10.1088/1475-7516/2026/02/e01","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/e01","url":null,"abstract":"In a recent analysis presented in ref. [1], the particle creation process, the evaporation lifetimes, and the greybody bounds for the metric andmetric-affine formulations were examined. Some aspects require correction: a typo in ref. [2] concerning the black hole shadow radii affected the evaporation-lifetime and emission-rate results for the metric-affine case of the previous work, and the computational routine employed in ref. [1] introduced errors in the greybody bounds for tensor perturbations and in the bounds analysis.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"34 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146121938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-05DOI: 10.1088/1475-7516/2026/02/015
Igor Reis, Andre Scaffidi, Emmanuel Moulin and Martin White
This paper explores the sensitivity of the Cherenkov Telescope Array Observatory to dark matter annihilation in the Galactic Center, within the frameworks of Effective Field Theory and Simplified Models. We present sensitivity forecasts, utilizing an up-to-date instrument configuration and incorporating the latest models for Galactic Diffuse Emission. A key aspect of our work is the inclusion of updated dark matter density profiles, J-factors, and velocity dispersion distributions derived from the FIRE-2 cosmological hydrodynamical simulations, which significantly impact the expected indirect detection signals. Furthermore, we update the constraints from direct detection experiments (Xenon1T and LZ) taking into account the astrophysical uncertainties informed by the FIRE-2 simulations, and also investigate limits coming from collider searches (ATLAS and CMS). Our analysis reveals improved constraints on the effective suppression scale (M*) in the Effective Field Theory framework and on the mediator mass (Mmed) in Simplified Models compared to previous studies, highlighting the complementarity of the Cherenkov Telescope Array Observatory with direct and collider searches in probing a wide range of dark matter scenarios. We discuss the implications of these results for various dark matter interaction types, including scalar, pseudoscalar, vector, and axial-vector mediators, and emphasize the importance of considering realistic astrophysical inputs in interpreting dark matter search results across different experimental fronts.
{"title":"The complementary of CTAO, direct detection and collider searches for dark matter in Effective Field Theories and Simplified Models","authors":"Igor Reis, Andre Scaffidi, Emmanuel Moulin and Martin White","doi":"10.1088/1475-7516/2026/02/015","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/015","url":null,"abstract":"This paper explores the sensitivity of the Cherenkov Telescope Array Observatory to dark matter annihilation in the Galactic Center, within the frameworks of Effective Field Theory and Simplified Models. We present sensitivity forecasts, utilizing an up-to-date instrument configuration and incorporating the latest models for Galactic Diffuse Emission. A key aspect of our work is the inclusion of updated dark matter density profiles, J-factors, and velocity dispersion distributions derived from the FIRE-2 cosmological hydrodynamical simulations, which significantly impact the expected indirect detection signals. Furthermore, we update the constraints from direct detection experiments (Xenon1T and LZ) taking into account the astrophysical uncertainties informed by the FIRE-2 simulations, and also investigate limits coming from collider searches (ATLAS and CMS). Our analysis reveals improved constraints on the effective suppression scale (M*) in the Effective Field Theory framework and on the mediator mass (Mmed) in Simplified Models compared to previous studies, highlighting the complementarity of the Cherenkov Telescope Array Observatory with direct and collider searches in probing a wide range of dark matter scenarios. We discuss the implications of these results for various dark matter interaction types, including scalar, pseudoscalar, vector, and axial-vector mediators, and emphasize the importance of considering realistic astrophysical inputs in interpreting dark matter search results across different experimental fronts.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"38 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146122420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-05DOI: 10.1088/1475-7516/2026/02/017
Valerie Domcke, Miguel Escudero, Mario Fernández Navarro and Stefan Sandner
At temperatures below the QCD phase transition, any substantial lepton number in the Universe can only be present within the neutrino sector. In this work, we systematically explore the impact of a non-vanishing lepton number on Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background (CMB). Relying on our recently developed framework based on momentum averaged quantum kinetic equations for the neutrino density matrix, we solve the full BBN reaction network to obtain the abundances of primordial elements. We find that the maximal primordial total lepton number L allowed by BBN and the CMB is -0.12 (-0.10) ≤ L ≤ 0.13 (0.12) for NH (IH), while specific flavor directions can be even more constrained. This bound is complementary to the limits obtained from avoiding baryon overproduction through sphaleron processes at the electroweak phase transition since, although numerically weaker, it applies at lower temperatures and is obtained completely independently. We publicly release the C++ code COFLASY-C on GitHub (https://github.com/mariofnavarro/COFLASY/tree/COFLASY-C) which solves for the evolution of the neutrino quantum kinetic equations numerically.
{"title":"A limit on the total lepton number in the Universe from BBN and the CMB","authors":"Valerie Domcke, Miguel Escudero, Mario Fernández Navarro and Stefan Sandner","doi":"10.1088/1475-7516/2026/02/017","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/02/017","url":null,"abstract":"At temperatures below the QCD phase transition, any substantial lepton number in the Universe can only be present within the neutrino sector. In this work, we systematically explore the impact of a non-vanishing lepton number on Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background (CMB). Relying on our recently developed framework based on momentum averaged quantum kinetic equations for the neutrino density matrix, we solve the full BBN reaction network to obtain the abundances of primordial elements. We find that the maximal primordial total lepton number L allowed by BBN and the CMB is -0.12 (-0.10) ≤ L ≤ 0.13 (0.12) for NH (IH), while specific flavor directions can be even more constrained. This bound is complementary to the limits obtained from avoiding baryon overproduction through sphaleron processes at the electroweak phase transition since, although numerically weaker, it applies at lower temperatures and is obtained completely independently. We publicly release the C++ code COFLASY-C on GitHub (https://github.com/mariofnavarro/COFLASY/tree/COFLASY-C) which solves for the evolution of the neutrino quantum kinetic equations numerically.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"17 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146121979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-05DOI: 10.1088/1475-7516/2026/02/012
Julien Grain and Hugo Holland
In this article we extend a study of the validity conditions of the separate-universe approach of cosmological perturbations to models of inflation with multiple fields. The separate-universe approach consists in describing the universe as a collection of homogeneous and isotropic patches, giving us an effective description of perturbation theory at large scales through phase-space reduction. This approximation is a necessary step in stochastic inflation, an effective theory of coarse-grained, super-Hubble, scalar fields fluctuations. One needs a stochastic inflation description in the context of primordial black hole productions since it needs enhancements of the curvature power spectrum. It is easily achievable in multifield inflation models but necessarily comes with strong diffusive effects. We study and compare cosmological perturbation theory and the separate-universe approach in said non-linear sigma models as a typical framework of multifield inflation and employ the Hamiltonian formalism to keep track of the complete phase space (or the reduced isotropic phase space in the separate-universe approach). We find that the separate-universe approach adequately describes the cosmological perturbation theory provided the wavelength of the modes considered is greater that several lower bounds that depend on the cosmological horizon and the inverse of the effective Hamiltonian masses of the fields; the latter being fixed by the coupling potential and the field-space geometry. We also compare gauge-invariant variables and several gauge fixing procedures in both approaches. For instance, we showed that the uniform-expansion gauge is nicely described by the separate-universe picture, hence justifying its use in stochastic inflation as commonly done.
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