Journal of High Energy Astrophysics最新文献

{"title":"Variability study of classical supergiant X-ray binary 4U 1907+09 using NuSTAR","authors":"Raj Kumar ,&nbsp;Sayantan Bhattacharya ,&nbsp;Sudip Bhattacharyya ,&nbsp;Subir Bhattacharyya","doi":"10.1016/j.jheap.2025.100412","DOIUrl":"10.1016/j.jheap.2025.100412","url":null,"abstract":"<div><div>We investigate the X-ray variability of the supergiant X-ray binary 4U 1907+09 using the new <em>NuSTAR</em> observation of 2024. Unlike the previous <em>NuSTAR</em> observations, the source shows significant flux variation during the current one. The light curve exhibits dips (off-state) and flares (on-state). The phase-coherent timing analysis during the on-state yields a pulse period of <span><math><mn>443.99</mn><mo>(</mo><mn>4</mn><mo>)</mo><mspace></mspace><mi>s</mi></math></span>, showing the pulsar's continued spin-down. The pulse profiles show an asymmetric double-peaked structure with a phase separation of 0.47 between the two peaks. A cyclotron resonance scattering feature (CRSF) is also detected at <span><math><mo>∼</mo><mn>17.6</mn><mspace></mspace><mrow><mi>keV</mi></mrow></math></span>, along with its harmonic at <span><math><mo>∼</mo><mn>38</mn><mspace></mspace><mrow><mi>keV</mi></mrow></math></span>, persisting across all flux states. Flux-resolved spectroscopy reveals that the CRSF energy remains constant despite a 25-fold change in flux. The spectral parameters, like photon index and e-fold energy, are out of phase with the pulse shape, whereas the cutoff energy is in phase with the pulse shape. The source's luminosity during the on-state is <span><math><mn>2.85</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>35</mn></mrow></msup><mspace></mspace><mrow><mi>erg</mi><mspace></mspace><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>, consistent with a “pencil” beam radiation pattern expected at this flux level from a collisionless gas-mediated shock. These results offer further insights into the accretion dynamics and magnetic field geometry of this system.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100412"},"PeriodicalIF":10.2,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144255388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A New Master Supernovae Ia sample and the investigation of the Hubble tension","authors":"M.G. Dainotti ,&nbsp;B. De Simone ,&nbsp;A. Garg ,&nbsp;K. Kohri ,&nbsp;A. Bashyal ,&nbsp;A. Aich ,&nbsp;A. Mondal ,&nbsp;S. Nagataki ,&nbsp;G. Montani ,&nbsp;T. Jareen ,&nbsp;V.M. Jabir ,&nbsp;S. Khanjani ,&nbsp;M. Bogdan ,&nbsp;N. Fraija ,&nbsp;A.C.C. do E.S. Pedreira ,&nbsp;R.H. Dejrah ,&nbsp;A. Singh ,&nbsp;M. Parakh ,&nbsp;R. Mandal ,&nbsp;K. Jarial ,&nbsp;H. Sarkar","doi":"10.1016/j.jheap.2025.100405","DOIUrl":"10.1016/j.jheap.2025.100405","url":null,"abstract":"<div><div>Modern cosmological research still thoroughly debates the discrepancy between local probes and the Cosmic Microwave Background observations in the Hubble constant (<span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>) measurements, ranging from 4 to 6<em>σ</em>. In the current study, we examine this tension using the Supernovae Ia (SNe Ia) data from the Pantheon, Pantheon+ (P+), Joint Lightcurve Analysis (JLA), and Dark Energy Survey, (DES) catalogs combined together into the so-called Master Sample. The sample contains 3714 SNe Ia, and is divided all of them into redshift-ordered bins. Three binning techniques are presented: the equi-population, the moving window (MW), and the equi-spacing in the <span><math><mi>log</mi><mo>⁡</mo><mo>−</mo><mi>z</mi></math></span>. We perform a Markov-Chain Monte Carlo analysis (MCMC) for each bin to determine the <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> value, estimating it within the standard flat ΛCDM and the <span><math><msub><mrow><mi>w</mi></mrow><mrow><mn>0</mn></mrow></msub><msub><mrow><mi>w</mi></mrow><mrow><mi>a</mi></mrow></msub></math></span>CDM models. These <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> values are then fitted with the following phenomenological function: <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>(</mo><mi>z</mi><mo>)</mo><mo>=</mo><msub><mrow><mover><mrow><mi>H</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub><mo>/</mo><msup><mrow><mo>(</mo><mn>1</mn><mo>+</mo><mi>z</mi><mo>)</mo></mrow><mrow><mi>α</mi></mrow></msup></math></span>, where <span><math><msub><mrow><mover><mrow><mi>H</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub></math></span> is a free parameter representing <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>(</mo><mi>z</mi><mo>)</mo></math></span> fitted in <span><math><mi>z</mi><mo>=</mo><mn>0</mn></math></span>, and <em>α</em> is the evolutionary parameter. Our results indicate a decreasing trend characterized by <span><math><mi>α</mi><mo>∼</mo><mn>0.01</mn></math></span>, whose consistency with zero ranges from 1<em>σ</em> in 5 cases to 1 case at 3 <em>σ</em> and 11 cases at <span><math><mo>&gt;</mo><mn>3</mn><mi>σ</mi></math></span> in several samples and configurations. Such a trend in the SNe Ia catalogs could be due to evolution with redshift for the astrophysical variables or unveiled selection biases. Alternatively, intrinsic physics, possibly the <span><math><mi>f</mi><mo>(</mo><mi>R</mi><mo>)</mo></math></span> theory of gravity, could be responsible for this trend.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100405"},"PeriodicalIF":10.2,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144223597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraining dark energy evolution in f(Q,C) gravity using observational datasets and geometric diagnostics","authors":"Amit Samaddar,&nbsp;S. Surendra Singh","doi":"10.1016/j.jheap.2025.100404","DOIUrl":"10.1016/j.jheap.2025.100404","url":null,"abstract":"<div><div>We investigate the cosmological implications of <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>,</mo><mi>C</mi><mo>)</mo></math></span> gravity with <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>,</mo><mi>C</mi><mo>)</mo><mo>=</mo><mi>α</mi><mi>Q</mi><mo>+</mo><mi>β</mi><mi>C</mi></math></span>, where <em>Q</em> is the non-metricity scalar and <em>C</em> encapsulates cosmological expansion terms. Three parameterizations of the EoS for dark energy, <span><math><mi>ω</mi><mo>=</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>+</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub><mi>z</mi></math></span>, <span><math><mi>ω</mi><mo>=</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>+</mo><mfrac><mrow><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub><mi>z</mi><mo>(</mo><mn>1</mn><mo>+</mo><mi>z</mi><mo>)</mo></mrow><mrow><mn>1</mn><mo>+</mo><msup><mrow><mi>z</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac></math></span> and <span><math><mi>ω</mi><mo>=</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>+</mo><mfrac><mrow><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub><msup><mrow><mi>z</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow><mrow><mn>1</mn><mo>+</mo><msup><mrow><mi>z</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac></math></span> are tested using the Hubble, Hubble+BAO, and Hubble+BAO+Pantheon datasets to constrain model parameters. The resulting Hubble and deceleration parameters reveal a transition from deceleration to acceleration, supporting current cosmic acceleration observations. Analysis of the energy density and pressure confirms positive energy density and a negative pressure for dark energy, potentially driving the late-time acceleration. We examine energy conditions, showing compliance with NEC, WEC and DEC, while SEC remains negative, supporting an accelerated expansion. Statefinder diagnostics suggest that two of the EoS parameterizations lead to Quintessence-like behavior with a time-varying dark energy component, while the third closely approaches ΛCDM showing slight deviations consistent with recent observations. Sound speed analysis demonstrates the physical stability of all parameterizations. Overall, our findings support <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>,</mo><mi>C</mi><mo>)</mo></math></span> gravity as a viable framework for describing diverse dark energy dynamics, providing insights into the Universe's accelerated expansion.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100404"},"PeriodicalIF":10.2,"publicationDate":"2025-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144205145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Solving an interacting quintessence model with a sound horizon initial condition and its observational constraints","authors":"Wenzhong Liu ,&nbsp;Yabo Wu ,&nbsp;Supriya Pan ,&nbsp;Weiqiang Yang","doi":"10.1016/j.jheap.2025.100403","DOIUrl":"10.1016/j.jheap.2025.100403","url":null,"abstract":"<div><div>Astronomical observations suggest that the current standard Λ-Cold Dark Matter model in modern cosmology has some discrepancies when fitting the data during the whole expansion history of the universe. To solve the Hubble constant (<span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>) tension, usually an unknown mechanism is considered that shifts the sound horizon at the decoupling era. On the other hand, dynamical dark energy models are also considered to resolve the problems of the cosmological constant, and the additional degrees of freedom require initial conditions for a solution. In this article we have considered a coupled quintessence dark energy model with a special focus on its early-time behaviour. In our solution the initial conditions are naturally decided by setting the value of the sound horizon at the recombination time, <span><math><msup><mrow><mi>θ</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>. We find that during this process, <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> could be derived and its value rises with the coupling strength of the interaction. We also performed the background and cosmic microwave background power spectrum analysis, and find that the existence of the interaction term affects the energy density during a narrow time interval range and shifts the early cosmic microwave background spectrum. We also constrained the parameter space of the underlying scenario using the Markov chain Monte Carlo analysis. We find that the best-fit values of <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>S</mi></mrow><mrow><mn>8</mn></mrow></msub></math></span> are improved slightly for the interacting model, but not enough to release the tensions.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"47 ","pages":"Article 100403"},"PeriodicalIF":10.2,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144189937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"BL Lacertae under the flare of 2024: Probing temporal and spectral dynamics","authors":"Joysankar Majumdar,&nbsp;Sakshi Maurya,&nbsp;Raj Prince","doi":"10.1016/j.jheap.2025.100402","DOIUrl":"10.1016/j.jheap.2025.100402","url":null,"abstract":"<div><div>In October 2024, the object BL Lacertae experienced the brightest flaring event in gamma-ray (&gt;100 MeV) with a historically bright <em>γ</em>-ray flux of ∼2.59 <span><math><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>5</mn></mrow></msup></math></span> erg cm⁻² s⁻¹ with a detection of a 175.7 GeV photon with Fermi-LAT. This event was also followed by very high-energy <em>γ</em>-ray detection with LHAASO, VERITAS, and MAGIC. Soon after, Swift-XRT and Swift-UVOT follow-up confirmed the concurrent flare in X-ray, UV, and optical bands. A minimum flux doubling/halving time of 1.06 ± 0.26 hour with 4<em>σ</em> significance has been observed with the Fermi-LAT orbit binned light curve. No compelling correlation has been found between <em>γ</em>-ray spectral indices and fluxes. The log-normal <em>γ</em>-ray flux distribution during the flare confirms the multiplicative nature of the non-linear perturbation causing the flare. We applied a one-zone leptohadronic model to fit the broadband SED during the flaring period. The broadband SED modeling reveals that the sudden enhancement of the magnetic field and bulk factor might promote the flare. The SED modeling also suggested a more compact emission region, which may be described by a shorter variability time than the observed one. The hadronic part best fitted the high energy part of the spectrum, suggesting the jets of BL Lac could provide a promising environment to accelerate the cosmic ray particles, such as protons. The jets of BL Lacertae could also be the possible source of astrophysical neutrinos, as an upper limit on neutrinos has already been reported from IceCube.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"48 ","pages":"Article 100402"},"PeriodicalIF":10.2,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144223097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Antisymmetric tensor influence on charged black hole lensing phenomena and time delay","authors":"A.A. Araújo Filho","doi":"10.1016/j.jheap.2025.100401","DOIUrl":"10.1016/j.jheap.2025.100401","url":null,"abstract":"<div><div>In this work, we investigate the gravitational lensing of a charged black hole (spherically symmetric) within the context of Lorentz violation triggered by an antisymmetric tensor field. Our calculations consider two different scenarios: the weak and strong deflection limits. For the weak deflection limit, we employ the <em>Gauss–Bonnet</em> theorem to obtain our results. In the strong deflection limit, we utilize the <em>Tsukamoto</em> methodology, which provides measurable outcomes such as relativistic image positions and magnifications. Applying the latter methodology, we analyze the gravitational lensing by Sagittarius <span><math><msup><mrow><mi>A</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> and derive the related observables, which are expressed as functions of the Lorentz violation parameter. Finally, the time delay is addressed as well.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"47 ","pages":"Article 100401"},"PeriodicalIF":10.2,"publicationDate":"2025-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144139105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-wavelength analysis of FSRQ B2 1348+30B: Constraints on the jet power","authors":"Sajad Ahanger ,&nbsp;Sunder Sahayanathan ,&nbsp;Sitha K. Jagan ,&nbsp;Shah Zahir ,&nbsp;Naseer Iqbal","doi":"10.1016/j.jheap.2025.100400","DOIUrl":"10.1016/j.jheap.2025.100400","url":null,"abstract":"<div><div>We present 14.5-year multi-wavelength analysis of flat-spectrum radio quasar B2<!--> <!-->1348+30B using Swift-UVOT, Swift-XRT, and <em>Fermi</em>-LAT observations. In the <em>γ</em>-ray band, the 3<!--> <!-->day bin lightcurve reveals two major flaring events on 2010-09-19 (55458 MJD) and 2022-05-26 (59725 MJD) detected at flux levels <span><math><mo>(</mo><mn>2.5</mn><mo>±</mo><mn>0.5</mn><mo>)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>7</mn></mrow></msup><mspace></mspace><mrow><mi>ph c</mi><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup><mspace></mspace><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span> and <span><math><mo>(</mo><mn>5.2</mn><mo>±</mo><mn>0.6</mn><mo>)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>7</mn></mrow></msup><mspace></mspace><mrow><mi>ph c</mi><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup><mspace></mspace><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>. The Bayesian block analysis of the flares suggested the variability timescale to be ≤ 3<!--> <!-->day. To study the dynamic nature of the source, multi-wavelength spectrum was obtained for three flux states which includes the two flaring state and a relative low state. The <em>γ</em>-ray spectra of the source in all the states are well fitted by a power-law model with maximum photon energy &lt; 20 GeV. In X-ray, a power-law model can explain the flaring state spectra while a broken power-law with extremely hard high energy component was required to model the low flux state. This indicates the presence of the low energy cutoff in the Compton spectral component. A simple one-zone leptonic model involving synchrotron, synchrotron self Compton and external Compton mechanism can successfully reproduce the broad-band spectral energy distribution of all the flux states. The model parameters suggest significant increase in the jet Lorentz factor during the high flux states. Further, the best fit parameters are used to constrain the minimum energy of the emitting electron distribution from the hard high energy spectrum of the low flux state. This analysis was extended to draw limits on the kinetic power of the blazar jet and was compared with the Eddington luminosity of the central black hole.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"47 ","pages":"Article 100400"},"PeriodicalIF":10.2,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144146737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Einstein-Gauss-Bonnet cosmology confronted with observations","authors":"Sergei D. Odintsov ,&nbsp;V.K. Oikonomou ,&nbsp;German S. Sharov","doi":"10.1016/j.jheap.2025.100398","DOIUrl":"10.1016/j.jheap.2025.100398","url":null,"abstract":"<div><div>Several models within the framework of Einstein-Gauss-Bonnet gravities are considered with regard their late-time phenomenological viability. The models contain a non-minimally coupled scalar field and satisfy a constraint on the scalar field Gauss-Bonnet coupling, that guarantees that the speed of the tensor perturbations is equal to the speed of light. The late-time cosmological evolution of these Einstein-Gauss-Bonnet models is confronted with the observational data including the Pantheon plus Type Ia supernovae catalogue, the Hubble parameter measurements (cosmic chronometers), data from cosmic microwave background radiation (CMB) and baryon acoustic oscillations (BAO) including the latest measurements from Dark Energy Spectroscopic Instrument (DESI). Among the considered class of models some of them do not fit the CMB and BAO data. However, there exists some models that generate a viable Einstein-Gauss-Bonnet scenario with well-behaved late-time cosmological evolution that fits the observational data essentially better in comparison to the standard Λ-Cold-Dark-Matter model.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"47 ","pages":"Article 100398"},"PeriodicalIF":10.2,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144089269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chasing super-horizon correlations: The promise of LiteBIRD polarization measurements","authors":"Francesca Di Nella,&nbsp;Alessandro Melchiorri","doi":"10.1016/j.jheap.2025.100399","DOIUrl":"10.1016/j.jheap.2025.100399","url":null,"abstract":"<div><div>It is well known that, since Cosmic Microwave Background (CMB) polarization originates at the surface of last scattering, scenarios in which perturbations are generated causally within the horizon cannot produce correlations at angular scales larger than about 2 degrees. In contrast, inflationary models predict a distinctive peak in the correlation functions at these large angular scales. By comparing the null hypothesis (no <em>TE</em> signal at large scales) with the ΛCDM prediction, we show that while Planck already provides strong statistical evidence for super-horizon perturbations, a future CMB satellite experiment as LiteBIRD will further reinforce this conclusion by improving current constraints by more than a factor of 3. We then consider an alternative explanation for the observed suppression of large-scale polarization: a low-<em>k</em> cutoff in the primordial power spectrum. We forecast the sensitivity of LiteBIRD to this cutoff scale, <span><math><msub><mrow><mi>k</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span>. In particular, we find that LiteBIRD will improve the constraint on <span><math><msub><mrow><mi>k</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span> by a factor of 1.4, outperforming Planck. These results highlight the critical role of large-scale polarization in establishing the presence of super-horizon correlations and offer new avenues to probe deviations from a scale-invariant primordial spectrum.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"47 ","pages":"Article 100399"},"PeriodicalIF":10.2,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144084191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cosmological phase-space analysis of f(G)-theories of gravity","authors":"Giannis Papagiannopoulos ,&nbsp;Orlando Luongo ,&nbsp;Genly Leon ,&nbsp;Andronikos Paliathanasis","doi":"10.1016/j.jheap.2025.100397","DOIUrl":"10.1016/j.jheap.2025.100397","url":null,"abstract":"<div><div>The impact of topological terms that modify the Hilbert-Einstein action is here explored by virtue of a further <span><math><mi>f</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span> contribution. In particular, we investigate the phase-space stability and critical points of an equivalent scalar field representation that makes use of a massive field, whose potential is function of the topological correction. To do so, we introduce to the gravitational Action Integral a Lagrange multiplier and model the modified Friedmann equations by virtue of new non-dimensional variables. We single out dimensionless variables that permit <em>a priori</em> the Hubble rate change of sign, enabling regions in which the Hubble parameter either vanishes or becomes negative. In this respect, we thus analyze the various possibilities associated with a universe characterized by such topological contributions and find the attractors, saddle points and regions of stability, in general. The overall analysis is carried out considering the exponential potential first and then shifting to more complicated cases, where the underlying variables do not simplify. We compute the eigenvalues of our coupled differential equations and, accordingly, the stability of the system, in both a spatially-flat and non-flat universe. Quite remarkably, regardless of the spatial curvature, we show that a stable de Sitter-like phase that can model current time appears only a small fraction of the entire phase-space, suggesting that the model under exam is unlikely in describing the whole universe dynamics, i.e., the topological terms appear disfavored in framing the entire evolution of the universe.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"47 ","pages":"Article 100397"},"PeriodicalIF":10.2,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143918193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}