Pub Date : 2026-01-05DOI: 10.1088/1475-7516/2026/01/002
Minxi He, Muzi Hong and Kyohei Mukaida
We investigate the matter current couplings with the scalar degrees of freedom originated from the torsion in Einstein–Cartan (EC) gravity. It has been shown in previous studies that the presence of the operators consisting of torsion components up to dimension four can naturally induce a (pseudo-)scalar degree of freedom, the scalaron. In this work, we consider the couplings between torsion and matter currents in this framework, and show that they can lead to couplings between these currents and the scalaron in the equivalent metric theory. We consider both gauge-invariant and gauge-dependent currents, showing general results and several concrete examples. These results are useful for the discussion of particle production processes after inflation in the EC framework, such as reheating and baryogenesis, and show the connection to the QCD θ term.
{"title":"Torsion induced current-scalaron coupling in Einstein–Cartan gravity","authors":"Minxi He, Muzi Hong and Kyohei Mukaida","doi":"10.1088/1475-7516/2026/01/002","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/002","url":null,"abstract":"We investigate the matter current couplings with the scalar degrees of freedom originated from the torsion in Einstein–Cartan (EC) gravity. It has been shown in previous studies that the presence of the operators consisting of torsion components up to dimension four can naturally induce a (pseudo-)scalar degree of freedom, the scalaron. In this work, we consider the couplings between torsion and matter currents in this framework, and show that they can lead to couplings between these currents and the scalaron in the equivalent metric theory. We consider both gauge-invariant and gauge-dependent currents, showing general results and several concrete examples. These results are useful for the discussion of particle production processes after inflation in the EC framework, such as reheating and baryogenesis, and show the connection to the QCD θ term.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"3 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1088/1475-7516/2026/01/007
Faizuddin Ahmed and Edilberto O. Silva
This paper presents a comprehensive theoretical study of a Schwarzschild-like Anti-de Sitter (AdS) black hole (BH) influenced by a new cloud of strings (NCS) and a dark matter halo (DMH) characterized by a Dehnen-type density profile. We analyze the geodesic motion of both massless and massive test particles, highlighting how the NCS and DMH parameters affect the effective potentials, photon spheres, circular orbits, the BH shadow, and the innermost stable circular orbit (ISCO) of test particles. Additionally, we investigate the thermodynamic behavior of the BH in an extended phase space by deriving key quantities, including the Hawking temperature, the equation of state (EoS), the Gibbs free energy, the internal energy, and the specific heat capacity. Our results show that the presence of NCS and DMH induces significant modifications in both the dynamical and thermodynamic behavior of the BH, including shifts in the Hawking-Page transition and divergences in the heat capacity, thereby reshaping the BH's phase structure.
{"title":"Black hole solution in anti-de Sitter space with a new cloud of strings surrounded by dark matter halo","authors":"Faizuddin Ahmed and Edilberto O. Silva","doi":"10.1088/1475-7516/2026/01/007","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/007","url":null,"abstract":"This paper presents a comprehensive theoretical study of a Schwarzschild-like Anti-de Sitter (AdS) black hole (BH) influenced by a new cloud of strings (NCS) and a dark matter halo (DMH) characterized by a Dehnen-type density profile. We analyze the geodesic motion of both massless and massive test particles, highlighting how the NCS and DMH parameters affect the effective potentials, photon spheres, circular orbits, the BH shadow, and the innermost stable circular orbit (ISCO) of test particles. Additionally, we investigate the thermodynamic behavior of the BH in an extended phase space by deriving key quantities, including the Hawking temperature, the equation of state (EoS), the Gibbs free energy, the internal energy, and the specific heat capacity. Our results show that the presence of NCS and DMH induces significant modifications in both the dynamical and thermodynamic behavior of the BH, including shifts in the Hawking-Page transition and divergences in the heat capacity, thereby reshaping the BH's phase structure.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"87 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1088/1475-7516/2026/01/008
Anirban Chakraborty and Tirthankar Roy Choudhury
The James Webb Space Telescope (JWST) has transformed our understanding of early galaxy formation, providing an unprecedented view of the first billion years of cosmic history. These observations offer a crucial opportunity to probe the interplay between galaxy formation and reionization, placing stringent constraints on theoretical models. In this work, we build upon our previously developed semi-analytical framework that self-consistently models the evolving UV luminosity function (UVLF) of galaxies and the global reionization history while incorporating the effects of radiative feedback. Comparing our predictions with JWST and HST data, we identify a fundamental tension: models that match the UVLF fail to reproduce the observed evolution of galaxy clustering (bias) with redshift, and vice versa. To resolve this, we introduce a redshift- and mass-dependent duty cycle linked to the duration of star formation. This duty cycle increases towards higher redshifts, requiring either an enhanced production of UV radiation or increased star formation efficiency at z > 10 to match the JWST UVLFs, but declines at lower redshifts (5 < z ≤ 9) and towards low-mass halos to remain consistent with the bias and HST UVLF measurements. Reconciling theory with observations requires the characteristic star formation timescale to be longer in massive halos, and to decrease with redshift at fixed halo mass, evolving from ≈ 85 Myr at z = 6 to ≈ 45 Myr at z = 14 for 1010M⊙ halos. Finally, our extended model, assuming a halo mass-dependent escaping ionizing efficiency (εesc ≡ fesc × ξion), whose population-averaged value gradually increases with redshift and corresponds to 〈fesc〉 ≈ 15% at z = 5 for a fixed value of ξion = 1025.23 erg-1 Hz across all galaxies, produces a reionization history consistent with current constraints. These findings underscore the importance of jointly constraining high-redshift galaxy models using both UVLF and bias statistics to accurately interpret JWST data and refine our understanding of early cosmic evolution.
{"title":"Probing reionization-era galaxies with JWST UV luminosity functions and large-scale clustering","authors":"Anirban Chakraborty and Tirthankar Roy Choudhury","doi":"10.1088/1475-7516/2026/01/008","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/008","url":null,"abstract":"The James Webb Space Telescope (JWST) has transformed our understanding of early galaxy formation, providing an unprecedented view of the first billion years of cosmic history. These observations offer a crucial opportunity to probe the interplay between galaxy formation and reionization, placing stringent constraints on theoretical models. In this work, we build upon our previously developed semi-analytical framework that self-consistently models the evolving UV luminosity function (UVLF) of galaxies and the global reionization history while incorporating the effects of radiative feedback. Comparing our predictions with JWST and HST data, we identify a fundamental tension: models that match the UVLF fail to reproduce the observed evolution of galaxy clustering (bias) with redshift, and vice versa. To resolve this, we introduce a redshift- and mass-dependent duty cycle linked to the duration of star formation. This duty cycle increases towards higher redshifts, requiring either an enhanced production of UV radiation or increased star formation efficiency at z > 10 to match the JWST UVLFs, but declines at lower redshifts (5 < z ≤ 9) and towards low-mass halos to remain consistent with the bias and HST UVLF measurements. Reconciling theory with observations requires the characteristic star formation timescale to be longer in massive halos, and to decrease with redshift at fixed halo mass, evolving from ≈ 85 Myr at z = 6 to ≈ 45 Myr at z = 14 for 1010M⊙ halos. Finally, our extended model, assuming a halo mass-dependent escaping ionizing efficiency (εesc ≡ fesc × ξion), whose population-averaged value gradually increases with redshift and corresponds to 〈fesc〉 ≈ 15% at z = 5 for a fixed value of ξion = 1025.23 erg-1 Hz across all galaxies, produces a reionization history consistent with current constraints. These findings underscore the importance of jointly constraining high-redshift galaxy models using both UVLF and bias statistics to accurately interpret JWST data and refine our understanding of early cosmic evolution.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"29 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1088/1475-7516/2026/01/013
Konstantin Leyde, Tessa Baker and Wolfgang Enzi
The dark siren method exploits the complementarity between gravitational-wave binary coalescence signals and galaxy catalogs originating from the same regions of space. However, all galaxy catalogs are incomplete, i.e. they only include a subset of all galaxies, typically being biased towards the bright end of the luminosity distribution. This sub-selection systematically affects the dark siren inference of the Hubble constant H0, so a completeness relation has to be introduced that accounts for the missing objects. In the literature it is standard to assume that the missing galaxies are uniformly distributed across the sky and that the galaxy magnitude distribution is known. In this work we develop a novel method which improves upon these assumptions and reconstructs the underlying true galaxy field, respecting the spatial correlation of galaxies on large scales. In our method the true magnitude distribution of galaxies is inferred alongside the spatial galaxy distribution. Our method results in an improved three-dimensional prior in redshift and sky position for the host galaxy of a GW event, which is expected to make the resulting H0 posterior more robust. Building on our previous work, we make a number of improvements, and validate our method on simulated data based on the Millennium simulation. The inference results can be reproduced through our publicly available code base LIGHThttps://github.com/KonstantinLeyde/light.
{"title":"Cosmic cartography. Part II. Completing galaxy catalogs for gravitational-wave cosmology","authors":"Konstantin Leyde, Tessa Baker and Wolfgang Enzi","doi":"10.1088/1475-7516/2026/01/013","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/013","url":null,"abstract":"The dark siren method exploits the complementarity between gravitational-wave binary coalescence signals and galaxy catalogs originating from the same regions of space. However, all galaxy catalogs are incomplete, i.e. they only include a subset of all galaxies, typically being biased towards the bright end of the luminosity distribution. This sub-selection systematically affects the dark siren inference of the Hubble constant H0, so a completeness relation has to be introduced that accounts for the missing objects. In the literature it is standard to assume that the missing galaxies are uniformly distributed across the sky and that the galaxy magnitude distribution is known. In this work we develop a novel method which improves upon these assumptions and reconstructs the underlying true galaxy field, respecting the spatial correlation of galaxies on large scales. In our method the true magnitude distribution of galaxies is inferred alongside the spatial galaxy distribution. Our method results in an improved three-dimensional prior in redshift and sky position for the host galaxy of a GW event, which is expected to make the resulting H0 posterior more robust. Building on our previous work, we make a number of improvements, and validate our method on simulated data based on the Millennium simulation. The inference results can be reproduced through our publicly available code base LIGHThttps://github.com/KonstantinLeyde/light.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"29 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1088/1475-7516/2026/01/012
Guillermo Ballesteros, Jesús Gambín Egea, Thomas Konstandin, Alejandro Pérez Rodríguez, Mathias Pierre and Julián Rey
We study the non-Gaussian tail of the curvature fluctuation, ζ, in an inflationary scenario with a transient ultra slow-roll phase that generates a localized large enhancement of the spectrum of ζ. To do so, we implement a numerical procedure that provides the probability distribution of ζ order by order in perturbation theory. The non-Gaussianities of ζ can be shown to arise from its non-linear relation to the inflaton fluctuations and from the intrinsic non-Gaussianities of the latter, which stem from its self interactions. We find that intrinsic non-Gaussianities, which have often been ignored to estimate the abundance of primordial black holes in this kind of scenario, are important. The relevance of the intrinsic contribution depends on the rapidity with which the transient ultra slow-roll phase occurs, as well as on its duration. Our method cannot be used accurately when the perturbative in-in formalism fails to apply, highlighting the relevance of developing fully non-perturbative approaches to the problem.
{"title":"Intrinsic non-Gaussianity of ultra slow-roll inflation","authors":"Guillermo Ballesteros, Jesús Gambín Egea, Thomas Konstandin, Alejandro Pérez Rodríguez, Mathias Pierre and Julián Rey","doi":"10.1088/1475-7516/2026/01/012","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/012","url":null,"abstract":"We study the non-Gaussian tail of the curvature fluctuation, ζ, in an inflationary scenario with a transient ultra slow-roll phase that generates a localized large enhancement of the spectrum of ζ. To do so, we implement a numerical procedure that provides the probability distribution of ζ order by order in perturbation theory. The non-Gaussianities of ζ can be shown to arise from its non-linear relation to the inflaton fluctuations and from the intrinsic non-Gaussianities of the latter, which stem from its self interactions. We find that intrinsic non-Gaussianities, which have often been ignored to estimate the abundance of primordial black holes in this kind of scenario, are important. The relevance of the intrinsic contribution depends on the rapidity with which the transient ultra slow-roll phase occurs, as well as on its duration. Our method cannot be used accurately when the perturbative in-in formalism fails to apply, highlighting the relevance of developing fully non-perturbative approaches to the problem.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"41 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1088/1475-7516/2026/01/005
João Luís Rosa, Nicolas Aimar and Diego Rubiera-Garcia
We analyze the observational features of hot-spots orbiting parametrized black hole (BH) spacetimes. We select a total of four BH spacetimes, two of them adapted from the Johanssen-Psaltis (JP) parametrization, and two from the Konoplya-Rezzolla-Zhidenko (KRZ) parametrization, corresponding to the most extreme configurations whose shadow sizes are within the 2σ-constraints of the Event Horizon Telescope (EHT). We use the ray-tracing software GYOTO to simulate the orbit of a spherically symmetric hot-spot emitting synchrotron radiation close to a central parametrized BH object, in a vertical magnetic field configuration, and we extract the corresponding astrometric and polarimetric observables for the Stokes parameters I, Q and U, namely the time integrated fluxes, temporal fluxes and magnitudes, temporal centroid, temporal QU-loops, and temporal Electric Field Position Angle (EVPA). Our results indicate that at low inclination the astrometric observables extracted from the parametrized BH spacetimes considered are qualitatively similar to those extracted from the Schwarzschild one, with minor quantitative deviations caused by differences in the size and position of the secondary images. On the other hand, the polarimetric observables at high inclination present qualitative differences, but these are only visible for a short portion of the whole hot-spot orbit. Furthermore, the observables extracted from the JP parametrized BH models deviate more prominently from those of the Schwarzschild model than the ones extracted from the KRZ parametrized BH models, with the JP model with a positive free parameter deviating the most among all models tested. Given the strong similarity among the observables extracted from all models tested, we point out that more precise observations are needed to successfully impose constraints on parametrized BH models via this method.
{"title":"Astrometric and polarimetric imprints of hot-spots orbiting parametrized black holes","authors":"João Luís Rosa, Nicolas Aimar and Diego Rubiera-Garcia","doi":"10.1088/1475-7516/2026/01/005","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/005","url":null,"abstract":"We analyze the observational features of hot-spots orbiting parametrized black hole (BH) spacetimes. We select a total of four BH spacetimes, two of them adapted from the Johanssen-Psaltis (JP) parametrization, and two from the Konoplya-Rezzolla-Zhidenko (KRZ) parametrization, corresponding to the most extreme configurations whose shadow sizes are within the 2σ-constraints of the Event Horizon Telescope (EHT). We use the ray-tracing software GYOTO to simulate the orbit of a spherically symmetric hot-spot emitting synchrotron radiation close to a central parametrized BH object, in a vertical magnetic field configuration, and we extract the corresponding astrometric and polarimetric observables for the Stokes parameters I, Q and U, namely the time integrated fluxes, temporal fluxes and magnitudes, temporal centroid, temporal QU-loops, and temporal Electric Field Position Angle (EVPA). Our results indicate that at low inclination the astrometric observables extracted from the parametrized BH spacetimes considered are qualitatively similar to those extracted from the Schwarzschild one, with minor quantitative deviations caused by differences in the size and position of the secondary images. On the other hand, the polarimetric observables at high inclination present qualitative differences, but these are only visible for a short portion of the whole hot-spot orbit. Furthermore, the observables extracted from the JP parametrized BH models deviate more prominently from those of the Schwarzschild model than the ones extracted from the KRZ parametrized BH models, with the JP model with a positive free parameter deviating the most among all models tested. Given the strong similarity among the observables extracted from all models tested, we point out that more precise observations are needed to successfully impose constraints on parametrized BH models via this method.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"16 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1088/1475-7516/2026/01/001
A. Antony, S.A. Appleby, W.L. Matthewson and A. Shafieloo
To assess the significance and scale dependence of anomalous large scale modes in the CatWISE quasar data, we generate smoothed number density fields on the sphere and study their extreme values — maximum, minimum, maximum antipodal difference. By comparing these summary statistics to those obtained from random isotropic realisations of the data, we determine the statistical significance of large scale modes as a function of smoothing scale. We perform our analysis using five different versions of the data — the original quasar map, the maps after separately subtracting the ecliptic bias and the CMB dipole, the map obtained after subtracting both, and the map after subtracting the ecliptic bias and anomalous dipole inferred inAstrophys. J. Lett.908 (2021) L51. We find that the ecliptic-corrected, CMB dipole-removed map exhibits large scale modes that are in tension with random realisations of the data (p-values p ≲ 10-4), over a wide range of smoothing scales π/8 ≤ δ ≤ π/2. The most prominent feature in the data is an under-density in the southern galactic plane at (b,ℓ) = (-31°,78°), which reaches its highest statistical significance when smoothed on scales δ = π/6 (p = 1.2 × 10-6). Notably, the minima statistics align with the maximum antipodal difference statistics, whereas the maxima do not. This suggests that the observed dipole-like behavior in the data is primarily driven by the under-density in the southern sky. The ecliptic corrected, anomalous dipole subtracted map reduces the significance of any residual anisotropic features, but an under-density in the south sky persists with p-value p = 0.0018.
{"title":"Isotropy test with quasars using method of smoothed residuals","authors":"A. Antony, S.A. Appleby, W.L. Matthewson and A. Shafieloo","doi":"10.1088/1475-7516/2026/01/001","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/001","url":null,"abstract":"To assess the significance and scale dependence of anomalous large scale modes in the CatWISE quasar data, we generate smoothed number density fields on the sphere and study their extreme values — maximum, minimum, maximum antipodal difference. By comparing these summary statistics to those obtained from random isotropic realisations of the data, we determine the statistical significance of large scale modes as a function of smoothing scale. We perform our analysis using five different versions of the data — the original quasar map, the maps after separately subtracting the ecliptic bias and the CMB dipole, the map obtained after subtracting both, and the map after subtracting the ecliptic bias and anomalous dipole inferred inAstrophys. J. Lett.908 (2021) L51. We find that the ecliptic-corrected, CMB dipole-removed map exhibits large scale modes that are in tension with random realisations of the data (p-values p ≲ 10-4), over a wide range of smoothing scales π/8 ≤ δ ≤ π/2. The most prominent feature in the data is an under-density in the southern galactic plane at (b,ℓ) = (-31°,78°), which reaches its highest statistical significance when smoothed on scales δ = π/6 (p = 1.2 × 10-6). Notably, the minima statistics align with the maximum antipodal difference statistics, whereas the maxima do not. This suggests that the observed dipole-like behavior in the data is primarily driven by the under-density in the southern sky. The ecliptic corrected, anomalous dipole subtracted map reduces the significance of any residual anisotropic features, but an under-density in the south sky persists with p-value p = 0.0018.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"79 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1088/1475-7516/2026/01/004
Giorgio Orlando, Shingo Akama and Chunshan Lin
In this paper, we explore parity violation in a scalar trispectrum from a dynamical Chern-Simons gravity theory. So far, a graviton-mediated diagram with two vertexes being of general relativity has been studied in this theory by taking into account the impact of a modified dispersion relation of gravitons on graviton's bulk propagators. We instead study a parity-odd trispectrum from both a graviton-mediated diagram, where one of the two vertexes originates from the Chern-Simons term, and a contact diagram by using the bulk propagators in general relativity. After computing the scalar-scalar-tensor cubic interactions and the scalar quartic ones originating from the Chern-Simons term, first we show that the resultant parity-odd trispectrum vanishes in the case of Bunch-Davies initial conditions, which is consistent with a no-go theorem for a non-vanishing parity-odd trispectrum. Then, we discuss a way to acquire a non-vanishing parity-odd trispectrum from the viewpoint of non-Bunch-Davies initial conditions.
{"title":"Scalar parity-odd trispectrum from gravitational Chern-Simons interaction vertices","authors":"Giorgio Orlando, Shingo Akama and Chunshan Lin","doi":"10.1088/1475-7516/2026/01/004","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/01/004","url":null,"abstract":"In this paper, we explore parity violation in a scalar trispectrum from a dynamical Chern-Simons gravity theory. So far, a graviton-mediated diagram with two vertexes being of general relativity has been studied in this theory by taking into account the impact of a modified dispersion relation of gravitons on graviton's bulk propagators. We instead study a parity-odd trispectrum from both a graviton-mediated diagram, where one of the two vertexes originates from the Chern-Simons term, and a contact diagram by using the bulk propagators in general relativity. After computing the scalar-scalar-tensor cubic interactions and the scalar quartic ones originating from the Chern-Simons term, first we show that the resultant parity-odd trispectrum vanishes in the case of Bunch-Davies initial conditions, which is consistent with a no-go theorem for a non-vanishing parity-odd trispectrum. Then, we discuss a way to acquire a non-vanishing parity-odd trispectrum from the viewpoint of non-Bunch-Davies initial conditions.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"24 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897697","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 : 2025-12-23DOI: 10.1088/1475-7516/2025/12/057
C. Gimeno-Amo, F.K. Hansen, E. Martínez-González, R.B. Barreiro and A.J. Banday
The origin of small deviations from statistical isotropy in the Cosmic Microwave Background (CMB) — the so-called CMB anomalies — remains an open question in modern cosmology. In this work, we test statistical isotropy in Planck Data Release 4 (PR4) by estimating the temperature and E-mode power spectra across independent sky regions. We find that the directions with higher local bandpower amplitudes in intensity are clustered for multipoles between 200 and 2000 with clustering probabilities consistently below 1% for all these scales when compared to end-to-end (E2E) Planck simulations; notably, this range extends beyond that reported in Planck Data Release 3 (PR3). On the other hand, no significant clustering is observed in the polarisation E-modes. In a complementary analysis, we search for dipolar variations in cosmological parameters fitted using the previously computed power spectra. When combining temperature and polarisation power spectra, we identify a potential anomaly in the amplitude of the primordial power spectrum, As, with only 5 out of 600 simulations exhibiting a dipole amplitude as large as that observed in the data. Interestingly, the dipole direction aligns closely with the known hemispherical power asymmetry, suggesting a potential link between these anomalies. All other cosmological parameters remain consistent with ΛCDM expectations. Our findings highlight the need to further investigate these anomalies and understand their nature and potential implications for better understanding of the early Universe.
{"title":"Exploring statistical isotropy in Planck Data Release 4: Angular clustering and cosmological parameter variations across the sky","authors":"C. Gimeno-Amo, F.K. Hansen, E. Martínez-González, R.B. Barreiro and A.J. Banday","doi":"10.1088/1475-7516/2025/12/057","DOIUrl":"https://doi.org/10.1088/1475-7516/2025/12/057","url":null,"abstract":"The origin of small deviations from statistical isotropy in the Cosmic Microwave Background (CMB) — the so-called CMB anomalies — remains an open question in modern cosmology. In this work, we test statistical isotropy in Planck Data Release 4 (PR4) by estimating the temperature and E-mode power spectra across independent sky regions. We find that the directions with higher local bandpower amplitudes in intensity are clustered for multipoles between 200 and 2000 with clustering probabilities consistently below 1% for all these scales when compared to end-to-end (E2E) Planck simulations; notably, this range extends beyond that reported in Planck Data Release 3 (PR3). On the other hand, no significant clustering is observed in the polarisation E-modes. In a complementary analysis, we search for dipolar variations in cosmological parameters fitted using the previously computed power spectra. When combining temperature and polarisation power spectra, we identify a potential anomaly in the amplitude of the primordial power spectrum, As, with only 5 out of 600 simulations exhibiting a dipole amplitude as large as that observed in the data. Interestingly, the dipole direction aligns closely with the known hemispherical power asymmetry, suggesting a potential link between these anomalies. All other cosmological parameters remain consistent with ΛCDM expectations. Our findings highlight the need to further investigate these anomalies and understand their nature and potential implications for better understanding of the early Universe.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"117 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145813134","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 : 2025-12-23DOI: 10.1088/1475-7516/2025/12/056
Sourav Bhattacharya and Kinsuk Roy
We consider a scalar field theory with quartic self interaction, Yukawa coupled to fermions in the inflationary de Sitter spacetime background. The scalar has a classical background plus quantum fluctuations, whereas the fermions are taken to be quantum. We derive for this system the effective action and the effective potential via the two particle irreducible (2PI) formalism. This formalism provides an opportunity to find out resummed or non-perturbative expressions for some series of diagrams. We have considered the two loop vacuum graphs and have computed the local part of the effective action. The various resummed counterterms corresponding to self energies, vertex functions and the tadpole have been explicitly found out. The variation of the renormalised effective potential for massless fields has been investigated numerically. We show that for the potential to be bounded from below, we must have λ ≳ 16g2, where λ and g are respectively the quartic and Yukawa couplings. We emphasise the qualitative differences of this non-perturbative calculation with that of the standard 1PI perturbative ones in de Sitter. The qualitative differences of our result with that of the flat spacetime has also been pointed out.
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