Astroparticle Physics最新文献

{"title":"Solar flare observations with the Radio Neutrino Observatory Greenland (RNO-G)","authors":"S. Agarwal ,&nbsp;J.A. Aguilar ,&nbsp;S. Ali ,&nbsp;P. Allison ,&nbsp;M. Betts ,&nbsp;D. Besson ,&nbsp;A. Bishop ,&nbsp;O. Botner ,&nbsp;S. Bouma ,&nbsp;S. Buitink ,&nbsp;M. Cataldo ,&nbsp;B.A. Clark ,&nbsp;A. Coleman ,&nbsp;K. Couberly ,&nbsp;S. de Kockere ,&nbsp;K.D. de Vries ,&nbsp;C. Deaconu ,&nbsp;M.A. DuVernois ,&nbsp;C. Glaser ,&nbsp;T. Glüsenkamp ,&nbsp;A. Zink","doi":"10.1016/j.astropartphys.2024.103024","DOIUrl":"10.1016/j.astropartphys.2024.103024","url":null,"abstract":"<div><p>The Radio Neutrino Observatory – Greenland (RNO-G) seeks discovery of ultra-high energy neutrinos from the cosmos through their interactions in ice. The science program extends beyond particle astrophysics to include radioglaciology and, as we show herein, solar observations, as well. Currently seven of 35 planned radio-receiver stations (24 antennas/station) are operational. These stations are sensitive to impulsive radio signals with frequencies between 80 and 700 MHz and feature a neutrino trigger threshold for recording data close to the thermal floor. RNO-G can also trigger on elevated signals from the Sun, resulting in nanosecond resolution time-domain flare data; such temporal resolution is significantly shorter than from most dedicated solar observatories. In addition to possible RNO-G solar flare polarization measurements, the Sun also represents an extremely useful above-surface calibration source.</p><p>Using RNO-G data recorded during the summers of 2022 and 2023, we find signal excesses during solar flares reported by the solar-observing Callisto network and also in coincidence with <span><math><mo>∼</mo></math></span>2/3 of the brightest excesses recorded by the SWAVES satellite. These observed flares are characterized by significant time-domain impulsivity. Using the known position of the Sun, the flare sample is used to calibrate the RNO-G absolute pointing on the radio signal arrival direction to sub-degree resolution. We thus establish the Sun as a regularly observed astronomical calibration source to provide the accurate absolute pointing required for neutrino astronomy.</p></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"164 ","pages":"Article 103024"},"PeriodicalIF":4.2,"publicationDate":"2024-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0927650524001014/pdfft?md5=f876aff9a99915b0bc2280db28087cf9&pid=1-s2.0-S0927650524001014-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141933628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bulk viscous cosmological model in f(T,T) modified gravity","authors":"Raja Solanki,&nbsp;Aaqid Bhat,&nbsp;P.K. Sahoo","doi":"10.1016/j.astropartphys.2024.103013","DOIUrl":"10.1016/j.astropartphys.2024.103013","url":null,"abstract":"&lt;div&gt;&lt;p&gt;This article explores the impact of bulk viscosity on understanding the universe’s accelerated expansion within the context of modified &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; gravity, which is an extension of the &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; gravitational theory, allowing a broad coupling between the energy–momentum scalar &lt;span&gt;&lt;math&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; and the torsion scalar &lt;span&gt;&lt;math&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;. We consider two &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; functions, specifically &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mi&gt;β&lt;/mi&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;msqrt&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;/msqrt&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mi&gt;β&lt;/mi&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, where &lt;span&gt;&lt;math&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mi&gt;β&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; are arbitrary constants, along with the fluid part incorporating the coefficient of bulk viscosity &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;ζ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ζ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. We calculate the analytical solutions of the corresponding field equations for a flat FLRW environment, and then we constrain the free parameters of the obtained solution using CC, Pantheon+, and the CC+Pantheon+ samples. We perform the Bayesian statistical analysis to estimate the posterior probability utilizing the likelihood function and the MCMC random sampling technique. Further, to assess the effectiveness of our MCMC analysis, we estimate the corresponding AIC and BIC values, and we find that there is strong evidence supporting the assumed viscous modified gravity models for all three data sets. Also, we find that the linear model precisely mimics the &lt;span&gt;&lt;math&gt;&lt;mi&gt;Λ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;CDM model. We also investigate the evolutionary behavior of some prominent cosmological parameters. We observe that the effective equation of state parameter for both models predict the accelerating behavior of the cosmic expansion phase. In addition, from the statefinder test, we find that the parameters of the considered MOG models favor the quintessence-type behavior. Further, we observe that the behavior of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;z&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; curves corresponding to both models represent a consistent negative slope across the entire domain. We infer that our cosmological setting utilizing &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; gravity models with the viscous matter fluid embodies quintessence-like behavior","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"163 ","pages":"Article 103013"},"PeriodicalIF":4.2,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141851661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Observational constrained Weyl type f(Q,T) gravity cosmological model and the dynamical system analysis","authors":"Rahul Bhagat,&nbsp;B. Mishra","doi":"10.1016/j.astropartphys.2024.103011","DOIUrl":"10.1016/j.astropartphys.2024.103011","url":null,"abstract":"<div><p>Using the cosmological date sets, the cosmological parameters are constrained in this paper, with well known phantom behavioural Hubble parameter. To understand the dynamics of the Weyl type <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>Q</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> gravity, functional form of <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>Q</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> has been introduced, where <span><math><mi>Q</mi></math></span> and <span><math><mi>T</mi></math></span> respectively represents the nonmetricity scalar that depends on the Weyl vector <span><math><mrow><mo>(</mo><mi>Q</mi><mo>=</mo><mo>−</mo><mn>6</mn><msup><mrow><mi>w</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></mrow></math></span> and trace of energy–momentum tensor. Using the constrained values of the parameters, the other geometrical parameters are analysed and the accelerating behaviour has been shown. The dynamical parameters and energy conditions are also analysed. Further to get the complete evolutionary behaviour of the Universe, the dynamical system analysis has been performed.</p></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"163 ","pages":"Article 103011"},"PeriodicalIF":4.2,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141847877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Investigating early dark energy with new observations","authors":"Wei Zheng ,&nbsp;Shang Li ,&nbsp;Jun-Qing Xia","doi":"10.1016/j.astropartphys.2024.103012","DOIUrl":"10.1016/j.astropartphys.2024.103012","url":null,"abstract":"<div><p>This paper mainly presents updated constraints on several types of early dark energy (EDE) models proposed by V. Pettorino <em>et al.</em> using observations of cosmic microwave background radiation (CMB) from Planck satellite, the Pantheon Type Ia supernovae (SNIa) sample, and baryon acoustic oscillation (BAO) measurements. The results yield stringent upper limits on the constant EDE fraction parameter <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span>. While the present equation of state (EoS) of dark energy <span><math><msub><mrow><mi>w</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> in the EDE1 model suggests a mild tendency towards a value less than <span><math><mrow><mo>−</mo><mn>1</mn></mrow></math></span>, these models remain compatible with the <span><math><mi>Λ</mi></math></span>CDM scenario. Partly as a result of this slight tendency towards phantom late-time physics, EDE1 model supports a higher Hubble constant value, potentially narrowing the Hubble tension gap. The global fitting results also align with the notion that the constraint ability on <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> weakens when dark energy is present only over a limited period after last scattering. Furthermore, by using the formalism of Fisher information matrix, we forecast uncertainties in the measured parameters of EDE models from the next-generation “Stage 4” CMB (CMB-S4) experiment. Forecasted precision of <span><math><msub><mrow><mi>w</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> surpasses certain prior works, and most other basic parameters exhibit significantly higher limit precision compared to Planck 2018 results within the <span><math><mi>Λ</mi></math></span>CDM framework. To confirm the presence of EDE within the EDE1<span><math><mo>∼</mo></math></span>EDE4 parameterization frameworks, further advancements in observations are crucial.</p></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"163 ","pages":"Article 103012"},"PeriodicalIF":4.2,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141690922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geometric Hawking radiation of Schwarzschild Black Hole with novel quantum algebra","authors":"Mauricio Bellini ,&nbsp;Juan Ignacio Musmarra ,&nbsp;Daniela Magos Cortes","doi":"10.1016/j.astropartphys.2024.103010","DOIUrl":"10.1016/j.astropartphys.2024.103010","url":null,"abstract":"<div><p>In the context of an extended General Relativity theory with boundary terms included, we introduce a new nonlinear quantum algebra involving a quantum differential operator, with the aim to calculate quantum geometric alterations when a particle is created in the vicinity of a Schwarzschild black-hole by the Hawking radiation mechanism. The boundary terms in the varied action give rise to modifications in the geometric background, which are investigated by analyzing the metric tensor and the Ricci curvature within the framework of a renormalized quantum theory of gravity.</p></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"163 ","pages":"Article 103010"},"PeriodicalIF":4.2,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141623270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Detection limits and trigger rates for ultra-high energy cosmic ray detection with the EUSO-TA ground-based fluorescence telescope","authors":"J.H. Adams Jr. ,&nbsp;L. Anchordoqui ,&nbsp;D. Barghini ,&nbsp;M. Battisti ,&nbsp;A.A. Belov ,&nbsp;J.W. Belz ,&nbsp;M. Bertaina ,&nbsp;F. Bisconti ,&nbsp;C. Blaksley ,&nbsp;S. Blin-Bondil ,&nbsp;F. Capel ,&nbsp;M. Casolino ,&nbsp;A. Cummings ,&nbsp;T. Ebisuzaki ,&nbsp;J. Eser ,&nbsp;S. Falk ,&nbsp;F. Fenu ,&nbsp;S. Ferrarese ,&nbsp;G. Filippatos ,&nbsp;M. Fouka ,&nbsp;M.Yu. Zotov","doi":"10.1016/j.astropartphys.2024.103007","DOIUrl":"https://doi.org/10.1016/j.astropartphys.2024.103007","url":null,"abstract":"<div><p>EUSO-TA is a ground-based fluorescence telescope built to validate the design of ultra-high energy cosmic ray fluorescence detectors to be operated in space with the technology developed within the Joint Exploratory Missions for Extreme Universe Space Observatory (JEM-EUSO) program. It operates at the Telescope Array (TA) site in Utah, USA. With an external trigger provided by the Black Rock Mesa fluorescence detectors of the Telescope Array experiment, with EUSO-TA we observed air-showers from ultra-high energy cosmic rays, as well as laser events from the Central Laser Facility at the TA site and from portable lasers like the JEM-EUSO Global Light System prototype. Since the Black Rock Mesa fluorescence detectors have a <span><math><mo>∼</mo></math></span>30 times larger field of view than EUSO-TA, they allow a primary energy reconstruction based on the observation of a large part of the shower evolution, including the shower maximum, while EUSO-TA observes only a part of it, usually far away from the maximum. To estimate the detection limits of EUSO-TA in energy and distance, a method was developed to re-scale their energy, taking into account that EUSO-TA observes only a portion of the air-showers. The method was applied on simulation sets with showers with different primaries, energy, direction, and impact point on the ground, as well as taking into account the experimental environment. EUSO-TA was simulated with an internal trigger and different elevation angles and electronics. The same method was then applied also to real measurements and compared to the simulations. In addition, the method can also be used to estimate the detection limits for experiments that are operated at high altitudes and in most cases can see the maximum of the showers. This was done for EUSO-SPB1, an instrument installed on a super-pressure balloon. Finally, the expected detection rates for EUSO-TA were also assessed using the prepared simulated event sets. The rates correspond to a few detections per recording session of 30 h of observation, depending on the background level and the configuration of the detector.</p></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"163 ","pages":"Article 103007"},"PeriodicalIF":4.2,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0927650524000847/pdfft?md5=a964f46404a79038e01b92faa3b63380&pid=1-s2.0-S0927650524000847-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141595251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cosmic rays: High energy particle interactions in the atmosphere - Memorial issue for Prof. Dr. Thomas K. Gaisser","authors":"Frank G. Schröder ,&nbsp;Serap Tilav","doi":"10.1016/j.astropartphys.2024.103009","DOIUrl":"https://doi.org/10.1016/j.astropartphys.2024.103009","url":null,"abstract":"","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"163 ","pages":"Article 103009"},"PeriodicalIF":4.2,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141595250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Seminal electromagnetic fields from preinflation","authors":"Daniela Magos ,&nbsp;Mauricio Bellini","doi":"10.1016/j.astropartphys.2024.103006","DOIUrl":"https://doi.org/10.1016/j.astropartphys.2024.103006","url":null,"abstract":"<div><p>We investigate the geometric dynamics of the primordial electric and magnetic fields during the early stages of the universe by extending a recently introduced quantum algebra (Bellini et al., 2023). We work on an extended model of gravity that considers the boundary terms from the Einstein–Hilbert action as geometric quantum fluctuations of the spacetime. We propose that the extended Riemann manifold is generated by a new connection <span><math><msubsup><mrow><mover><mrow><mi>δ</mi><mi>Γ</mi></mrow><mrow><mo>ˆ</mo></mrow></mover></mrow><mrow><mi>α</mi><mi>β</mi></mrow><mrow><mi>μ</mi></mrow></msubsup></math></span>. This connection contains geometric information about the fluctuations of gravitational and electromagnetic fields in the vacuum, which could have been crucial during the primordial stages of the universe’s evolution. We revisit a preinflationary cosmological model (Bellini, 2023) with a variable time scale and negative spatial curvature, such that the universe begins with a null initial background energy density. We observed the emergence of large scale magnetic fields starting from small values during the early phases of the universe’s evolution. Subsequently, these fields decrease to reach present day values on the order of <span><math><mrow><mfenced><mrow><mover><mrow><mi>δ</mi><mi>B</mi></mrow><mrow><mo>ˆ</mo></mrow></mover></mrow></mfenced><mo>≃</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>12</mn></mrow></msup><mspace></mspace><mi>G</mi></mrow></math></span> on cosmological scales (between <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>24</mn></mrow></msup></mrow></math></span> and <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>26</mn></mrow></msup></mrow></math></span> meters). This significant deviation from inflationary models eliminates the need to impose excessively large initial values on these fields.</p></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"163 ","pages":"Article 103006"},"PeriodicalIF":4.2,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141539231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 hybrid approach to event reconstruction for atmospheric Cherenkov Telescopes combining machine learning and likelihood fitting","authors":"Georg Schwefer ,&nbsp;Robert Parsons ,&nbsp;Jim Hinton","doi":"10.1016/j.astropartphys.2024.103008","DOIUrl":"https://doi.org/10.1016/j.astropartphys.2024.103008","url":null,"abstract":"<div><p>The imaging atmospheric Cherenkov technique provides potentially the highest angular resolution achievable in astronomy at energies above the X-ray waveband. High-resolution measurements provide the key to progress on many of the major questions in high energy astrophysics, including the sites and mechanisms of particle acceleration to PeV energies. The huge potential of the next-generation CTA observatory in this regard can be realised with the help of improved algorithms for the reconstruction of the air-shower direction and energy.</p><p>Hybrid methods combining maximum-likelihood-fitting techniques with neural networks represent a particularly promising approach and have recently been successfully applied for the reconstruction of astrophysical neutrinos. Here, we present the <em>FreePACT</em> algorithm, a hybrid reconstruction method for IACTs. In this, making use of the neural ratio estimation technique from the field of likelihood-free inference, the analytical likelihood used in traditional image likelihood fitting is replaced by a neural network that approximates the charge probability density function for each pixel in the camera.</p><p>The performance of this improved algorithm is demonstrated using simulations of the planned CTA southern array. For this setup<em>FreePACT</em> provides significant performance improvements over analytical likelihood techniques, with improvements in angular and energy resolution of 25% or more over a wide energy range and an angular resolution as low as <span><math><mrow><mtext>40</mtext><mo>′</mo><mo>′</mo></mrow></math></span> at energies above <span><math><mrow><mn>50</mn><mspace></mspace><mi>TeV</mi></mrow></math></span> for observations at <span><math><mrow><mn>20</mn><mo>°</mo></mrow></math></span> zenith angle. It also yields more accurate estimations of the uncertainties on the reconstructed parameters and significantly speeds up the reconstruction compared to analytical likelihood techniques while showing the same stability with respect to changes in the observation conditions. Therefore, the <em>FreePACT</em> method is a promising upgrade over the current state-of-the-art likelihood event reconstruction techniques.</p></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"163 ","pages":"Article 103008"},"PeriodicalIF":4.2,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0927650524000859/pdfft?md5=5e050cfcd2be1db5eef601e5935e2423&pid=1-s2.0-S0927650524000859-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141539234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anisotropies of diffusive ultra-high energy cosmic rays in f(R) gravity theory","authors":"Swaraj Pratim Sarmah,&nbsp;Umananda Dev Goswami","doi":"10.1016/j.astropartphys.2024.103005","DOIUrl":"https://doi.org/10.1016/j.astropartphys.2024.103005","url":null,"abstract":"<div><p>Understanding the anisotropy of ultra high-energy cosmic rays (UHECRs) is crucial for unravelling the origins and propagation mechanisms of these enigmatic particles. In this work, we studied the dipolar anisotropy of UHECRs in the diffusive regime by considering three cosmological models: the standard <span><math><mi>Λ</mi></math></span>CDM model, <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>)</mo></mrow></mrow></math></span> gravity power-law model and the Starobinsky model. This work aims to see the role of the <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>)</mo></mrow></mrow></math></span> gravity theory in understanding the anisotropy of UHECRs without condoning the standard cosmology. We found that the amplitude of the dipolar anisotropy is sensitive to these cosmological models, with the <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>)</mo></mrow></mrow></math></span> power-law model predicting the largest amplitude, while the <span><math><mi>Λ</mi></math></span>CDM model predicting the smallest amplitude at most of the energies in the range considered. The predicted amplitude of the Starobinsky model lies within the range of the <span><math><mi>Λ</mi></math></span>CDM one. This work not only provides a way for exploration of UHECRs anisotropy within different cosmological contexts but also may pave the way for new avenues of research at the intersection of high-energy astrophysics.</p></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"163 ","pages":"Article 103005"},"PeriodicalIF":4.2,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141485839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}