Pub Date : 2026-03-16DOI: 10.1088/1475-7516/2026/03/049
Camilo García-Cely and Andreas Ringwald
Using the bimetric formalism, we compute the production and emission rates of light spin-2 particles in non-degenerate stellar interiors through photoproduction and bremsstrahlung processes, including the effects of plasma screening. By comparing the resulting energy-loss rates with observational limits on stellar cooling, we derive bounds on the coupling strength and mass of the spin-2 particle. Assuming these particles are the dark matter of the Universe, the obtained constraints are competitive with existing astrophysical and cosmological limits, excluding a wide region of parameter space in the mass range 5–30 eV.
{"title":"Stellar bounds on light spin-2 particles in bimetric theories","authors":"Camilo García-Cely and Andreas Ringwald","doi":"10.1088/1475-7516/2026/03/049","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/049","url":null,"abstract":"Using the bimetric formalism, we compute the production and emission rates of light spin-2 particles in non-degenerate stellar interiors through photoproduction and bremsstrahlung processes, including the effects of plasma screening. By comparing the resulting energy-loss rates with observational limits on stellar cooling, we derive bounds on the coupling strength and mass of the spin-2 particle. Assuming these particles are the dark matter of the Universe, the obtained constraints are competitive with existing astrophysical and cosmological limits, excluding a wide region of parameter space in the mass range 5–30 eV.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"52 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-16DOI: 10.1088/1475-7516/2026/03/047
Kaito Yura, Shohei Saga, Maresuke Shiraishi and Shuichiro Yokoyama
Some recent observations of the cosmic microwave background (CMB) anisotropies and the large-scale structure of the Universe suggest cosmic parity violation. Among possible parity-violating sources, helical primordial magnetic fields (PMFs) are of particular interest, as they inherently violate parity symmetry and can explain the observed magnetic fields, especially in void regions. PMFs, if generated in the early universe, can source curvature perturbations, which evolve into the present density fluctuations observed in CMB and galaxy surveys. Motivated by this, we study the trispectrum of primordial curvature perturbations induced by helical PMFs, which serves as the leading-order statistical observable sensitive to parity-violating signals. We derive full expressions for the trispectrum of the primordial curvature perturbations sourced by both the helical and non-helical PMFs and reduce them to computationally-feasible ones using a proper approximation. We numerically confirm that parity-odd signals are efficiently enhanced and surpass parity-even ones in specific momentum and parameter spaces. Parity-violating signatures found in this paper are partially testable with the observational results obtained so far. Assuming nearly scale-invariant power spectra for non-helical and helical PMFs with identical spectral indices (nB = nH = -2.9), we estimate an upper bound on the helical-to-non-helical power ratio, rH, satisfying |rH| ≤ 1 as |rH| ≲ 10-4(B1Mpc/5nG)-8. Our findings highlight the primordial trispectrum as a promising probe of helical PMFs and provide a theoretical basis for future precise observations of higher-order statistics in the CMB anisotropies and the 3D galaxy clustering.
{"title":"Parity-violating scalar trispectrum from helical primordial magnetic fields","authors":"Kaito Yura, Shohei Saga, Maresuke Shiraishi and Shuichiro Yokoyama","doi":"10.1088/1475-7516/2026/03/047","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/047","url":null,"abstract":"Some recent observations of the cosmic microwave background (CMB) anisotropies and the large-scale structure of the Universe suggest cosmic parity violation. Among possible parity-violating sources, helical primordial magnetic fields (PMFs) are of particular interest, as they inherently violate parity symmetry and can explain the observed magnetic fields, especially in void regions. PMFs, if generated in the early universe, can source curvature perturbations, which evolve into the present density fluctuations observed in CMB and galaxy surveys. Motivated by this, we study the trispectrum of primordial curvature perturbations induced by helical PMFs, which serves as the leading-order statistical observable sensitive to parity-violating signals. We derive full expressions for the trispectrum of the primordial curvature perturbations sourced by both the helical and non-helical PMFs and reduce them to computationally-feasible ones using a proper approximation. We numerically confirm that parity-odd signals are efficiently enhanced and surpass parity-even ones in specific momentum and parameter spaces. Parity-violating signatures found in this paper are partially testable with the observational results obtained so far. Assuming nearly scale-invariant power spectra for non-helical and helical PMFs with identical spectral indices (nB = nH = -2.9), we estimate an upper bound on the helical-to-non-helical power ratio, rH, satisfying |rH| ≤ 1 as |rH| ≲ 10-4(B1Mpc/5nG)-8. Our findings highlight the primordial trispectrum as a promising probe of helical PMFs and provide a theoretical basis for future precise observations of higher-order statistics in the CMB anisotropies and the 3D galaxy clustering.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"95 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-16DOI: 10.1088/1475-7516/2026/03/051
Quan Chen, Siyu Jiang, Dayun Qiu, Peilin Chen and Fa Peng Huang
Recent study [1] has suggested that warm inflation may be realized with a minimal extension of the Standard Model by a single scalar inflaton field with an axion-like coupling to gluons. Motivated by this framework, we investigate the gravitational wave spectrum and graviton-portal dark matter production through the freeze-in process generated during warm inflation scenarios. We perform a comparative analysis for different dissipation terms, focusing on their distinct gravitational wave signatures in the high-frequency regime. Our findings reveal qualitative and quantitative differences in the spectral behavior, offering a preliminary pathway for exploring inflationary and dark matter models through high-frequency gravitational wave signals.
{"title":"Freeze-in gravitational waves and dark matter in warm inflation","authors":"Quan Chen, Siyu Jiang, Dayun Qiu, Peilin Chen and Fa Peng Huang","doi":"10.1088/1475-7516/2026/03/051","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/051","url":null,"abstract":"Recent study [1] has suggested that warm inflation may be realized with a minimal extension of the Standard Model by a single scalar inflaton field with an axion-like coupling to gluons. Motivated by this framework, we investigate the gravitational wave spectrum and graviton-portal dark matter production through the freeze-in process generated during warm inflation scenarios. We perform a comparative analysis for different dissipation terms, focusing on their distinct gravitational wave signatures in the high-frequency regime. Our findings reveal qualitative and quantitative differences in the spectral behavior, offering a preliminary pathway for exploring inflationary and dark matter models through high-frequency gravitational wave signals.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"31 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-16DOI: 10.1088/1475-7516/2026/03/048
Benjamin Koch, Gonzalo J. Olmo, Ali Riahinia, Ángel Rincón and Diego Rubiera-Garcia
In this paper we investigate how a regular scale-dependent black hole, characterized by a single extra parameter ϵ, behaves under perturbations by a test field (quasi-normal modes) and under light imaging (shadows) in a four-dimensional space-time background. On the quasi-normal modes side, we study how it responds to scalar and Dirac perturbations. To do this, we implement the well known WKB semi-analytic method of 6th order for obtaining the quasi-normal frequencies. We derive analytic expressions for the quasinormal frequencies beyond the eikonal limit for both scalar and Dirac perturbations, finding excellent agreement with the WKB approximation. We discuss the behavior of the real and imaginary parts of the quasi-normal modes for different values of the parameter ϵ and the overtone n and multipole ℓ numbers. On the black hole imaging side, we ray-trace the geometry and illuminate it with a thin-accretion disk. Choosing ϵ = 1.0 we compute the size of the central brightness depression and generate full images of the black hole. We discuss the features (i.e. luminosity) of successive photon rings through the Lyapunov exponent of nearly-bound, unstable geodesics. Furthermore we use the correspondence (in the limit ℓ ≫ n) between quasi-normal mode frequencies and unstable bound light orbits to infer the numerical values of the latter using the former and find a remarkable accuracy of the correspondence in providing the right numbers. Our results support the usefulness of this correspondence in order to perform cross-tests of black holes using these two messengers.
{"title":"Quasi-normal modes and shadows of scale-dependent regular black holes","authors":"Benjamin Koch, Gonzalo J. Olmo, Ali Riahinia, Ángel Rincón and Diego Rubiera-Garcia","doi":"10.1088/1475-7516/2026/03/048","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/048","url":null,"abstract":"In this paper we investigate how a regular scale-dependent black hole, characterized by a single extra parameter ϵ, behaves under perturbations by a test field (quasi-normal modes) and under light imaging (shadows) in a four-dimensional space-time background. On the quasi-normal modes side, we study how it responds to scalar and Dirac perturbations. To do this, we implement the well known WKB semi-analytic method of 6th order for obtaining the quasi-normal frequencies. We derive analytic expressions for the quasinormal frequencies beyond the eikonal limit for both scalar and Dirac perturbations, finding excellent agreement with the WKB approximation. We discuss the behavior of the real and imaginary parts of the quasi-normal modes for different values of the parameter ϵ and the overtone n and multipole ℓ numbers. On the black hole imaging side, we ray-trace the geometry and illuminate it with a thin-accretion disk. Choosing ϵ = 1.0 we compute the size of the central brightness depression and generate full images of the black hole. We discuss the features (i.e. luminosity) of successive photon rings through the Lyapunov exponent of nearly-bound, unstable geodesics. Furthermore we use the correspondence (in the limit ℓ ≫ n) between quasi-normal mode frequencies and unstable bound light orbits to infer the numerical values of the latter using the former and find a remarkable accuracy of the correspondence in providing the right numbers. Our results support the usefulness of this correspondence in order to perform cross-tests of black holes using these two messengers.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"11 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-16DOI: 10.1088/1475-7516/2026/03/046
Yue-Yan Dong, Ji-Yu Song, Jing-Fei Zhang and Xin Zhang
Gravitational-wave (GW) detection offers a novel approach to exploring intermediate-mass black holes (IMBHs). The GW signals from IMBH mergers mainly fall in the decihertz frequency band. The lunar-based GW detector, the Lunar Gravitational-Wave Antenna (LGWA), exhibits high sensitivity in this band, making it particularly well-suited for detecting IMBHs. However, for lower-mass IMBHs, the late inspiral and merger signals enter the sensitive frequency range of ground-based GW detectors. In this work, we aim to explore how multi-band observations with LGWA and the third-generation ground-based GW detector, the Einstein Telescope (ET), can contribute to detecting the population of IMBHs. We consider three population distribution cases of IMBHs, including two population models based on astrophysical motivations and a uniform distribution, and compute the signal-to-noise ratios for LGWA, ET, and their combination to directly compare their capabilities in detecting IMBH mergers. Our results suggest that LGWA possesses strong detection capability for high-mass IMBH mergers. At redshift z = 1, LGWA's detection rate for IMBH binaries with primary masses above 5 × 104 M⊙ is largely insensitive to orbital inclination and mass ratio. In contrast, ET is more suited for detecting IMBH binaries with primary masses below 103 M⊙. The multi-band observation of LGWA and ET possesses strong detection capabilities across the full IMBH mass spectrum. Furthermore, we find that the multi-band detection can significantly and effectively recover the IMBH population distributions. In summary, we conclude that the multi-band observations of LGWA and ET will provide powerful detection capabilities for IMBHs and are expected to significantly enhance our understanding of this important yet still poorly observed class of black holes.
{"title":"Prospects for joint multiband detection of intermediate-mass black holes by LGWA and the Einstein Telescope","authors":"Yue-Yan Dong, Ji-Yu Song, Jing-Fei Zhang and Xin Zhang","doi":"10.1088/1475-7516/2026/03/046","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/046","url":null,"abstract":"Gravitational-wave (GW) detection offers a novel approach to exploring intermediate-mass black holes (IMBHs). The GW signals from IMBH mergers mainly fall in the decihertz frequency band. The lunar-based GW detector, the Lunar Gravitational-Wave Antenna (LGWA), exhibits high sensitivity in this band, making it particularly well-suited for detecting IMBHs. However, for lower-mass IMBHs, the late inspiral and merger signals enter the sensitive frequency range of ground-based GW detectors. In this work, we aim to explore how multi-band observations with LGWA and the third-generation ground-based GW detector, the Einstein Telescope (ET), can contribute to detecting the population of IMBHs. We consider three population distribution cases of IMBHs, including two population models based on astrophysical motivations and a uniform distribution, and compute the signal-to-noise ratios for LGWA, ET, and their combination to directly compare their capabilities in detecting IMBH mergers. Our results suggest that LGWA possesses strong detection capability for high-mass IMBH mergers. At redshift z = 1, LGWA's detection rate for IMBH binaries with primary masses above 5 × 104 M⊙ is largely insensitive to orbital inclination and mass ratio. In contrast, ET is more suited for detecting IMBH binaries with primary masses below 103 M⊙. The multi-band observation of LGWA and ET possesses strong detection capabilities across the full IMBH mass spectrum. Furthermore, we find that the multi-band detection can significantly and effectively recover the IMBH population distributions. In summary, we conclude that the multi-band observations of LGWA and ET will provide powerful detection capabilities for IMBHs and are expected to significantly enhance our understanding of this important yet still poorly observed class of black holes.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"8 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-16DOI: 10.1088/1475-7516/2026/03/050
Xinpeng Wang, Kazunori Kohri and Tsutomu T. Yanagida
In light of the latest Planck and Atacama Cosmology Telescope (P-ACT) joint results on the primordial scalar power spectrum, we show that the R2 inflation model extended with a non-minimally coupled scalar field χ — namely the χ-extended R2 inflation model — can naturally accommodate a larger spectral index ns and a small positive running αs at cosmic microwave background (CMB) scales, both of which are consistent with the latest P-ACT constraints. This is because the χ field contributes a blue-tilted component to the primordial power spectrum, which both modifies the large-scale power and, as a result, significantly enhances power on small scales. The deviation of the ns and αs from the single field R2 inflation is related to the non-minimal coupling constant ξ. The consequent enhancement in the primordial power spectrum can be large enough to lead to the formation of primordial black holes (PBHs) of mass ≲1020 g as dark matter candidates. Furthermore, future observations of the small-scale power spectrum, CMB spectral distortions, and stochastic gravitational waves will provide decisive tests of this model and its predictions for PBHs. We stress its strong connection to the seesaw mechanism for the generation of the observed small masses.
{"title":"Primordial black holes save R 2 inflation","authors":"Xinpeng Wang, Kazunori Kohri and Tsutomu T. Yanagida","doi":"10.1088/1475-7516/2026/03/050","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/050","url":null,"abstract":"In light of the latest Planck and Atacama Cosmology Telescope (P-ACT) joint results on the primordial scalar power spectrum, we show that the R2 inflation model extended with a non-minimally coupled scalar field χ — namely the χ-extended R2 inflation model — can naturally accommodate a larger spectral index ns and a small positive running αs at cosmic microwave background (CMB) scales, both of which are consistent with the latest P-ACT constraints. This is because the χ field contributes a blue-tilted component to the primordial power spectrum, which both modifies the large-scale power and, as a result, significantly enhances power on small scales. The deviation of the ns and αs from the single field R2 inflation is related to the non-minimal coupling constant ξ. The consequent enhancement in the primordial power spectrum can be large enough to lead to the formation of primordial black holes (PBHs) of mass ≲1020 g as dark matter candidates. Furthermore, future observations of the small-scale power spectrum, CMB spectral distortions, and stochastic gravitational waves will provide decisive tests of this model and its predictions for PBHs. We stress its strong connection to the seesaw mechanism for the generation of the observed small masses.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"407 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-12DOI: 10.1088/1475-7516/2026/03/045
Bianca De Caro, Isabella P. Carucci, Stefano Camera, Mathieu Remazeilles and Carmelita Carbone
Intensity Mapping (IM) of the 21-cm line of the neutral hydrogen (Hi) has become a compelling new technique to map the large-scale structure of the Universe. One of the main challenges is the presence of strong foreground emissions of several orders of magnitude larger than the Hi signal. Here, we implement a version of the Principal Component Analysis, a blind component-separation technique, based on a kind of spherical wavelets called needlets. These functions exploit double localization both in real and in harmonic space. We test Need-PCA performances on a set of maps that simulates the SKA MID radio telescope in the AA4 configuration. We compare our results with other component separation methods such as Generalised Morphological Component Analysis (GMCA) and Generalized Needlet Internal Linear Combination (GNILC). All the methods have comparable results, recovering the Hi signal within 10% accuracy across the frequency channels, in the multipole range 30 ≲ ℓ ≲ 136. We also test our pipeline in the presence of systematics such as polarization leakage. We find that the cleaning methods are insensitive to the presence of such systematic, yielding the same results as in the leakage-free case. Finally, under the assumption of a realistic telescope beam with sidelobes, we find that standard PCA and GMCA fails to recover the Hi signal at larger scales, while the Need-PCA and Need-GMCA are less affected. GNILC tends to over-clean, yielding to a loss of the signal.
中性氢（Hi）的21厘米线的强度映射（IM）已经成为一种引人注目的新技术来绘制宇宙的大尺度结构。主要的挑战之一是存在比Hi信号大几个数量级的强烈前景发射。在这里，我们实现了一个版本的主成分分析，这是一种盲成分分离技术，基于一种称为针尖的球形小波。这些函数在实空间和调和空间中都具有双局域性。我们在一组模拟SKA MID射电望远镜AA4配置的地图上测试了Need-PCA的性能。我们将结果与其他成分分离方法如广义形态成分分析（GMCA）和广义针尖内线性组合（GNILC）进行了比较。所有方法的结果都具有可比性，在多极子范围30 > r > 136的频率通道上，恢复Hi信号的精度在10%以内。我们还测试了我们的管道在系统的存在，如极化泄漏。我们发现清洁方法对这种系统的存在不敏感，产生与无泄漏情况相同的结果。最后，在具有副瓣的真实望远镜波束假设下，我们发现标准PCA和GMCA无法在更大尺度上恢复Hi信号，而Need-PCA和Need-GMCA受影响较小。GNILC倾向于过度清洁，导致信号丢失。
{"title":"Needlets and foreground removal for SKAO hydrogen intensity maps","authors":"Bianca De Caro, Isabella P. Carucci, Stefano Camera, Mathieu Remazeilles and Carmelita Carbone","doi":"10.1088/1475-7516/2026/03/045","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/045","url":null,"abstract":"Intensity Mapping (IM) of the 21-cm line of the neutral hydrogen (Hi) has become a compelling new technique to map the large-scale structure of the Universe. One of the main challenges is the presence of strong foreground emissions of several orders of magnitude larger than the Hi signal. Here, we implement a version of the Principal Component Analysis, a blind component-separation technique, based on a kind of spherical wavelets called needlets. These functions exploit double localization both in real and in harmonic space. We test Need-PCA performances on a set of maps that simulates the SKA MID radio telescope in the AA4 configuration. We compare our results with other component separation methods such as Generalised Morphological Component Analysis (GMCA) and Generalized Needlet Internal Linear Combination (GNILC). All the methods have comparable results, recovering the Hi signal within 10% accuracy across the frequency channels, in the multipole range 30 ≲ ℓ ≲ 136. We also test our pipeline in the presence of systematics such as polarization leakage. We find that the cleaning methods are insensitive to the presence of such systematic, yielding the same results as in the leakage-free case. Finally, under the assumption of a realistic telescope beam with sidelobes, we find that standard PCA and GMCA fails to recover the Hi signal at larger scales, while the Need-PCA and Need-GMCA are less affected. GNILC tends to over-clean, yielding to a loss of the signal.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"8 9-10 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147439673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-12DOI: 10.1088/1475-7516/2026/03/044
Ruiqi Chen, James M. Cline, Varun Muralidharan and Benjamin Salewicz
Motivated by recent results from the DESI collaboration, we explore two classes of quintessence models that can give rise to crossing of the dark energy equation of state through the “phantom divide” w = -1. These are models with Lagrangians that involve higher powers of the kinetic energy ϕ̇2, or where the dark matter (DM) mass is a function of ϕ. Both have similar features with respect to the reconstructed redshift-dependent w(z): moderate tuning of parameters is required to achieve the desired shape, and it is difficult or impossible for w(z) to continue evolving smoothly as z becomes large. Nevertheless, they give a strong improvement over ΛCDM in fitting the data. We point out that models of coupled dark matter and dark energy that cross the phantom divide are under pressure from constraints on long-range DM forces. They rule out the simplest renormalizable coupling of scalar DM to quintessence, but leave the fermionic case allowed, and exponentially coupled models of either kind of DM are safe from current constraints.
{"title":"Quintessential dark energy crossing the phantom divide","authors":"Ruiqi Chen, James M. Cline, Varun Muralidharan and Benjamin Salewicz","doi":"10.1088/1475-7516/2026/03/044","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/044","url":null,"abstract":"Motivated by recent results from the DESI collaboration, we explore two classes of quintessence models that can give rise to crossing of the dark energy equation of state through the “phantom divide” w = -1. These are models with Lagrangians that involve higher powers of the kinetic energy ϕ̇2, or where the dark matter (DM) mass is a function of ϕ. Both have similar features with respect to the reconstructed redshift-dependent w(z): moderate tuning of parameters is required to achieve the desired shape, and it is difficult or impossible for w(z) to continue evolving smoothly as z becomes large. Nevertheless, they give a strong improvement over ΛCDM in fitting the data. We point out that models of coupled dark matter and dark energy that cross the phantom divide are under pressure from constraints on long-range DM forces. They rule out the simplest renormalizable coupling of scalar DM to quintessence, but leave the fermionic case allowed, and exponentially coupled models of either kind of DM are safe from current constraints.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"76 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147439672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-12DOI: 10.1088/1475-7516/2026/03/041
Sanjeev Sanyal, Sanjeet K. Patel, Pavan K. Aluri and Arman Shafieloo
We undertake a reassessment of one of the large angular scale anomalies observed in cosmic microwave background (CMB) temperature signal referred to as Hemispherical Power Asymmetry (HPA). For the present analysis we use SEVEM cleaned CMB maps from Planck's 2020 final data release (public release 4/PR4). To probe HPA, we employed the local variance estimator (LVE) method with different disc radii ranging from 0.5° to 90°. Our emphasis here is to revalidate the LVE method in various ways for its optimal usage and probe the hemispherical power asymmetry in the form of a dipole modulation field underlying CMB sky. By and large, our results are in agreement with earlier reported ones with more detailed presentation of explicit and not-so-explicit assumptions involved in the estimation process. It is reaffirmed that HPA is confined to low multipoles or large angular scales of the CMB sky. A dipole like anisotropy was found in the LVE maps with anomalous power for disc radii of 2° and upward up to 36° at ≳ 2σ level. In the range 4° to 10° none of the 600 SEVEM CMB simulations were found to have a dipole amplitude higher than the data when using LVE method as originally proposed. The above reported values fall in the reliability range of LVE method after this extensive re-evaluation. We also observe a scale dependence of the HPA dipole amplitude and model it as a power-law. We conclude that the hemispherical power asymmetry still remains as a challenge to the standard model.
{"title":"A reassessment of LVE method and hemispherical power asymmetry in CMB temperature data from Planck PR4","authors":"Sanjeev Sanyal, Sanjeet K. Patel, Pavan K. Aluri and Arman Shafieloo","doi":"10.1088/1475-7516/2026/03/041","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/041","url":null,"abstract":"We undertake a reassessment of one of the large angular scale anomalies observed in cosmic microwave background (CMB) temperature signal referred to as Hemispherical Power Asymmetry (HPA). For the present analysis we use SEVEM cleaned CMB maps from Planck's 2020 final data release (public release 4/PR4). To probe HPA, we employed the local variance estimator (LVE) method with different disc radii ranging from 0.5° to 90°. Our emphasis here is to revalidate the LVE method in various ways for its optimal usage and probe the hemispherical power asymmetry in the form of a dipole modulation field underlying CMB sky. By and large, our results are in agreement with earlier reported ones with more detailed presentation of explicit and not-so-explicit assumptions involved in the estimation process. It is reaffirmed that HPA is confined to low multipoles or large angular scales of the CMB sky. A dipole like anisotropy was found in the LVE maps with anomalous power for disc radii of 2° and upward up to 36° at ≳ 2σ level. In the range 4° to 10° none of the 600 SEVEM CMB simulations were found to have a dipole amplitude higher than the data when using LVE method as originally proposed. The above reported values fall in the reliability range of LVE method after this extensive re-evaluation. We also observe a scale dependence of the HPA dipole amplitude and model it as a power-law. We conclude that the hemispherical power asymmetry still remains as a challenge to the standard model.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"57 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147439669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-12DOI: 10.1088/1475-7516/2026/03/043
Martin Teuscher, Ruth Durrer, Killian Martineau and Aurélien Barrau
We study the inflationary gravitational wave background induced by Abelian gauge fields generated by non-minimal kinetic and axial couplings to the inflaton. We show that, up to slow-roll corrections, for coupling functions that share the same dependence on conformal time, the gravitational wave spectrum is nearly scale invariant. We also derive its amplitude for generic gauge field coupling parameters, within the slow-roll approximation. The coupling values and the scale of inflation for which the induced gravitational wave background is observable, while ensuring that back-reaction on the inflationary dynamics remains negligible, are calculated. We find that a sizeable axial coupling can boost this secondary gravitational wave signal above the standard inflationary background. In the course of our analysis, we also show how to analytically match tensor perturbations across an arbitrary number of eras with different equations of state.
{"title":"Gravitational waves sourced by gauge fields during inflation","authors":"Martin Teuscher, Ruth Durrer, Killian Martineau and Aurélien Barrau","doi":"10.1088/1475-7516/2026/03/043","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/043","url":null,"abstract":"We study the inflationary gravitational wave background induced by Abelian gauge fields generated by non-minimal kinetic and axial couplings to the inflaton. We show that, up to slow-roll corrections, for coupling functions that share the same dependence on conformal time, the gravitational wave spectrum is nearly scale invariant. We also derive its amplitude for generic gauge field coupling parameters, within the slow-roll approximation. The coupling values and the scale of inflation for which the induced gravitational wave background is observable, while ensuring that back-reaction on the inflationary dynamics remains negligible, are calculated. We find that a sizeable axial coupling can boost this secondary gravitational wave signal above the standard inflationary background. In the course of our analysis, we also show how to analytically match tensor perturbations across an arbitrary number of eras with different equations of state.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"30 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147439671","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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