Pub Date : 2024-11-21DOI: 10.1088/1475-7516/2024/11/035
Martin Kerscher and Jochen Weller
With several examples and in an analysis of the Pantheon+ supernova sample we discuss the properties of the marginal posterior distribution versus the profiled posterior distribution — the profile likelihood in a Bayesian disguise. We investigate whether maximisation, as used for the profiling, or integration, as used for the marginalisation, is more appropriate. To report results we recommend the marginal posterior distribution.
{"title":"On marginals and profiled posteriors for cosmological parameter estimation","authors":"Martin Kerscher and Jochen Weller","doi":"10.1088/1475-7516/2024/11/035","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/11/035","url":null,"abstract":"With several examples and in an analysis of the Pantheon+ supernova sample we discuss the properties of the marginal posterior distribution versus the profiled posterior distribution — the profile likelihood in a Bayesian disguise. We investigate whether maximisation, as used for the profiling, or integration, as used for the marginalisation, is more appropriate. To report results we recommend the marginal posterior distribution.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"13 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678531","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 : 2024-11-21DOI: 10.1088/1475-7516/2024/11/033
R.J. van den Hoogen and H. Forance
We present the proper co-frame and its corresponding (diagonal) co-frame/spin connection pair for spherically symmetric geometries which can be used as an initial ansatz in any theory of teleparallel gravity. The Lorentz transformation facilitating the move from one co-frame to the other is also presented in factored form. The factored form also illustrates the nature of the two degrees of freedom found in the spin connection. The choice of coordinates in restricting the number of arbitrary functions is also presented. Beginning with a thorough presentation of teleparallel gravity using the metric affine gauge theory approach and concentrating on f(T) teleparallel gravity, we express the field equations in the diagonal co-frame. We argue that the choice of diagonal co-frame may be more advantageous over the proper co-frame choice. Finally, assuming one additional symmetry, we restrict ourselves to the Kantowski-Sachs teleparallel geometries, and determine some solutions.
{"title":"Teleparallel geometry with spherical symmetry: the diagonal and proper frames","authors":"R.J. van den Hoogen and H. Forance","doi":"10.1088/1475-7516/2024/11/033","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/11/033","url":null,"abstract":"We present the proper co-frame and its corresponding (diagonal) co-frame/spin connection pair for spherically symmetric geometries which can be used as an initial ansatz in any theory of teleparallel gravity. The Lorentz transformation facilitating the move from one co-frame to the other is also presented in factored form. The factored form also illustrates the nature of the two degrees of freedom found in the spin connection. The choice of coordinates in restricting the number of arbitrary functions is also presented. Beginning with a thorough presentation of teleparallel gravity using the metric affine gauge theory approach and concentrating on f(T) teleparallel gravity, we express the field equations in the diagonal co-frame. We argue that the choice of diagonal co-frame may be more advantageous over the proper co-frame choice. Finally, assuming one additional symmetry, we restrict ourselves to the Kantowski-Sachs teleparallel geometries, and determine some solutions.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"14 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678528","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 : 2024-11-21DOI: 10.1088/1475-7516/2024/11/036
Ankur Barsode and Tirthankar Roy Choudhury
Simulating the distribution of cosmological neutral hydrogen (HI) during the epoch of reionization requires a high dynamic range and is hence computationally expensive. The size of the simulation is dictated by the largest scales one aims to probe, while the resolution is determined by the smallest dark matter haloes capable of hosting the first stars. We present a hybrid approach where the density and tidal fields of a large-volume, low-resolution simulation are combined with small haloes from a small-volume, high-resolution box. By merging these two boxes of relatively lower dynamic range, we achieve an effective high-dynamic range simulation using only 13% of the computational resources required for a full high-dynamic range simulation. Our method accurately reproduces the one- and two-point statistics of the halo field, its cross-correlation with the dark matter density field, and the two-point statistics of the HI field computed using a semi-numerical code, all within 10% accuracy at large scales and across different redshifts. Our technique, combined with semi-numerical models of reionization, provides a resource-efficient tool for modeling the HI distribution at high redshifts.
模拟再电离时代宇宙学中性氢（HI）的分布需要很高的动态范围，因此计算成本很高。模拟的规模由所要探测的最大尺度决定，而分辨率则由能够容纳第一批恒星的最小暗物质晕决定。我们提出了一种混合方法，即把大体积、低分辨率模拟的密度场和潮汐场与小体积、高分辨率框中的小晕结合起来。通过合并这两个动态范围相对较低的方框，我们实现了有效的高动态范围模拟，所需的计算资源仅为全面高动态范围模拟的 13%。我们的方法精确地再现了晕场的单点和两点统计量、晕场与暗物质密度场的交叉相关性，以及使用半数字代码计算的 HI 场的两点统计量，在大尺度和不同红移下的精确度都在 10%以内。我们的技术与再电离的半数字模型相结合，为高红移下的 HI 分布建模提供了一种资源节约型工具。
{"title":"Efficient hybrid technique for generating sub-grid haloes in reionization simulations","authors":"Ankur Barsode and Tirthankar Roy Choudhury","doi":"10.1088/1475-7516/2024/11/036","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/11/036","url":null,"abstract":"Simulating the distribution of cosmological neutral hydrogen (HI) during the epoch of reionization requires a high dynamic range and is hence computationally expensive. The size of the simulation is dictated by the largest scales one aims to probe, while the resolution is determined by the smallest dark matter haloes capable of hosting the first stars. We present a hybrid approach where the density and tidal fields of a large-volume, low-resolution simulation are combined with small haloes from a small-volume, high-resolution box. By merging these two boxes of relatively lower dynamic range, we achieve an effective high-dynamic range simulation using only 13% of the computational resources required for a full high-dynamic range simulation. Our method accurately reproduces the one- and two-point statistics of the halo field, its cross-correlation with the dark matter density field, and the two-point statistics of the HI field computed using a semi-numerical code, all within 10% accuracy at large scales and across different redshifts. Our technique, combined with semi-numerical models of reionization, provides a resource-efficient tool for modeling the HI distribution at high redshifts.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"81 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678532","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 : 2024-11-21DOI: 10.1088/1475-7516/2024/11/034
Ashmita, Kinjal Banerjee and Prasanta Kumar Das
We study the evolution of k = -1 FLRW cosmological models for two interacting Dark Matter-Dark Energy Models using dynamical system analysis. Since we are interested in late time evolution, the sign of the interaction term is chosen such that it facilitates the transfer of energy from dark matter to dark energy. We also explore the k = 0 invariant subspace of these models. We find that both these models have sectors which have a stable fixed point where we can recover an accelerating universe with a negative equation of state. This indicates these can be viable models for our universe. We also rule out certain sectors of these models because they do not give the correct late time observational features. We observe that although we start with a dust-like Dark Matter, its effective equation of state evolves due to its interaction with Dark Energy. As a result, the Dark Matter can display features of stiff matter and exotic matter in the course of evolution.
我们利用动力学系统分析研究了两个相互作用的暗物质-暗能量模型的 k = -1 FLRW 宇宙学模型的演化。由于我们对晚期演化感兴趣，相互作用项的符号被选择为有利于能量从暗物质转移到暗能量。我们还探索了这些模型的 k = 0 不变子空间。我们发现，这两个模型都有一些具有稳定固定点的扇区，在这些扇区中，我们可以恢复一个具有负状态方程的加速宇宙。这表明它们可以成为我们宇宙的可行模型。我们还排除了这些模型的某些部分，因为它们没有给出正确的晚期观测特征。我们观察到，虽然我们一开始使用的是类似尘埃的暗物质，但由于它与暗能量的相互作用，其有效状态方程会发生演变。因此，暗物质在演化过程中会表现出僵硬物质和奇异物质的特征。
{"title":"Constructing viable interacting dark matter and dark energy models: a dynamical systems approach","authors":"Ashmita, Kinjal Banerjee and Prasanta Kumar Das","doi":"10.1088/1475-7516/2024/11/034","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/11/034","url":null,"abstract":"We study the evolution of k = -1 FLRW cosmological models for two interacting Dark Matter-Dark Energy Models using dynamical system analysis. Since we are interested in late time evolution, the sign of the interaction term is chosen such that it facilitates the transfer of energy from dark matter to dark energy. We also explore the k = 0 invariant subspace of these models. We find that both these models have sectors which have a stable fixed point where we can recover an accelerating universe with a negative equation of state. This indicates these can be viable models for our universe. We also rule out certain sectors of these models because they do not give the correct late time observational features. We observe that although we start with a dust-like Dark Matter, its effective equation of state evolves due to its interaction with Dark Energy. As a result, the Dark Matter can display features of stiff matter and exotic matter in the course of evolution.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"57 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678534","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 : 2024-11-20DOI: 10.1088/1475-7516/2024/11/032
Matteo Braglia, Gianluca Calcagni, Gabriele Franciolini, Jacopo Fumagalli, Germano Nardini, Marco Peloso, Mauro Pieroni, Sébastien Renaux-Petel, Angelo Ricciardone, Gianmassimo Tasinato, Ville Vaskonen and the LISA Cosmology Working Group
Various scenarios of cosmic inflation enhance the amplitude of the stochastic gravitational wave background (SGWB) at frequencies detectable by the LISA detector. We develop tools for a template-based analysis of the SGWB and introduce a template databank to describe well-motivated signals from inflation, prototype their template-based searches, and forecast their reconstruction with LISA. Specifically, we classify seven templates based on their signal frequency shape, and we identify representative fundamental physics models leading to them. By running a template-based analysis, we forecast the accuracy with which LISA can reconstruct the template parameters of representative benchmark signals, with and without galactic and extragalactic foregrounds. We identify the parameter regions that can be probed by LISA within each template. Finally, we investigate how our signal reconstructions shed light on fundamental physics models of inflation: we discuss their impact for measurements of e.g., the couplings of inflationary axions to gauge fields; the graviton mass during inflation; the fluctuation seeds of primordial black holes; the consequences of excited states during inflation, and the presence of small-scale spectral features.
宇宙膨胀的各种情况都会增强随机引力波背景（SGWB）在 LISA 探测器可探测频率上的振幅。我们开发了基于模板的 SGWB 分析工具，并引入了一个模板数据库来描述来自暴胀的动机良好的信号、基于模板的搜索原型，以及预测它们与 LISA 的重构。具体来说，我们根据信号频率形状对七个模板进行了分类，并确定了导致这些模板的代表性基本物理模型。通过运行基于模板的分析，我们预测了 LISA 在有银河系和银河系外前景和没有银河系和银河系外前景的情况下重建代表性基准信号的模板参数的准确性。我们确定了 LISA 在每个模板中可以探测到的参数区域。最后，我们研究了我们的信号重建如何揭示暴胀的基本物理模型：我们讨论了它们对测量的影响，例如暴胀轴子与规规场的耦合；暴胀期间的引力子质量；原始黑洞的波动种子；暴胀期间激发态的后果，以及小尺度光谱特征的存在。
{"title":"Gravitational waves from inflation in LISA: reconstruction pipeline and physics interpretation","authors":"Matteo Braglia, Gianluca Calcagni, Gabriele Franciolini, Jacopo Fumagalli, Germano Nardini, Marco Peloso, Mauro Pieroni, Sébastien Renaux-Petel, Angelo Ricciardone, Gianmassimo Tasinato, Ville Vaskonen and the LISA Cosmology Working Group","doi":"10.1088/1475-7516/2024/11/032","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/11/032","url":null,"abstract":"Various scenarios of cosmic inflation enhance the amplitude of the stochastic gravitational wave background (SGWB) at frequencies detectable by the LISA detector. We develop tools for a template-based analysis of the SGWB and introduce a template databank to describe well-motivated signals from inflation, prototype their template-based searches, and forecast their reconstruction with LISA. Specifically, we classify seven templates based on their signal frequency shape, and we identify representative fundamental physics models leading to them. By running a template-based analysis, we forecast the accuracy with which LISA can reconstruct the template parameters of representative benchmark signals, with and without galactic and extragalactic foregrounds. We identify the parameter regions that can be probed by LISA within each template. Finally, we investigate how our signal reconstructions shed light on fundamental physics models of inflation: we discuss their impact for measurements of e.g., the couplings of inflationary axions to gauge fields; the graviton mass during inflation; the fluctuation seeds of primordial black holes; the consequences of excited states during inflation, and the presence of small-scale spectral features.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"178 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673360","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 : 2024-11-20DOI: 10.1088/1475-7516/2024/11/030
J.D.F. Dias, Nils Schöneberg, Léo Vacher, C.J.A.P. Martins and Samy Vinzl
The rolling tachyon is a non-canonical scalar field model well motivated in string theory which naturally predicts variations of the fine-structure constant. Such variations can in principle lead to interesting observable consequences, but they can also lead to extremely tight constraints on these kinds of models. In this work we subject the rolling tachyon model evolving in a variety of potentials to current data and show that most cosmologically interesting evolutions are already strongly excluded. We find |1 + w0| < 10-3 from cosmological data and |1 + w0| < 10-9 from fine-structure data, leaving the rolling tachyon to either play a role almost entirely equivalent to a cosmological constant or that of a test field. We also find that in most of the allowed parameter space the field evolves very slowly, allowing its evolution to be approximated as an equivalent canonical scalar field.
{"title":"A speed limit on tachyon fields from cosmological and fine-structure data","authors":"J.D.F. Dias, Nils Schöneberg, Léo Vacher, C.J.A.P. Martins and Samy Vinzl","doi":"10.1088/1475-7516/2024/11/030","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/11/030","url":null,"abstract":"The rolling tachyon is a non-canonical scalar field model well motivated in string theory which naturally predicts variations of the fine-structure constant. Such variations can in principle lead to interesting observable consequences, but they can also lead to extremely tight constraints on these kinds of models. In this work we subject the rolling tachyon model evolving in a variety of potentials to current data and show that most cosmologically interesting evolutions are already strongly excluded. We find |1 + w0| < 10-3 from cosmological data and |1 + w0| < 10-9 from fine-structure data, leaving the rolling tachyon to either play a role almost entirely equivalent to a cosmological constant or that of a test field. We also find that in most of the allowed parameter space the field evolves very slowly, allowing its evolution to be approximated as an equivalent canonical scalar field.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"229 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673326","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 : 2024-11-20DOI: 10.1088/1475-7516/2024/11/031
Ginevra Braga, Alice Garoffolo, Angelo Ricciardone, Nicola Bartolo and Sabino Matarrese
When gravitational waves travel from their source to an observer, they interact with matter structures along their path, causing distinct deformations in their waveforms. In this study we introduce a novel theoretical framework for wave optics effects in gravitational lensing, addressing the limitations of existing approaches. We achieve this by incorporating the proper time technique, typically used in field theory studies, into gravitational lensing. This approach allows us to extend the standard formalism beyond the eikonal and paraxial approximations, which are traditionally assumed, and to account for polarization effects, which are typically neglected in the literature. We demonstrate that our method provides a robust generalization of conventional approaches, including them as special cases. Our findings enhance our understanding of gravitational wave propagation, which is crucial for accurately interpreting gravitational wave observations and extracting unbiased information about the lenses from the gravitational wave waveforms.
{"title":"Proper time path integrals for gravitational waves: an improved wave optics framework","authors":"Ginevra Braga, Alice Garoffolo, Angelo Ricciardone, Nicola Bartolo and Sabino Matarrese","doi":"10.1088/1475-7516/2024/11/031","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/11/031","url":null,"abstract":"When gravitational waves travel from their source to an observer, they interact with matter structures along their path, causing distinct deformations in their waveforms. In this study we introduce a novel theoretical framework for wave optics effects in gravitational lensing, addressing the limitations of existing approaches. We achieve this by incorporating the proper time technique, typically used in field theory studies, into gravitational lensing. This approach allows us to extend the standard formalism beyond the eikonal and paraxial approximations, which are traditionally assumed, and to account for polarization effects, which are typically neglected in the literature. We demonstrate that our method provides a robust generalization of conventional approaches, including them as special cases. Our findings enhance our understanding of gravitational wave propagation, which is crucial for accurately interpreting gravitational wave observations and extracting unbiased information about the lenses from the gravitational wave waveforms.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"178 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673327","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 : 2024-11-19DOI: 10.1088/1475-7516/2024/11/025
Alessio Notari, Michele Redi and Andrea Tesi
We search for physically consistent realizations of evolving dark energy suggested by the cosmological fit of DESI, Planck and Supernovae data. First we note that any lagrangian description of the standard Chevallier-Polarski-Linder (CPL) parametrization for the dark energy equation of state w, allows for the addition of a cosmological constant. We perform the cosmological fit finding new regions of parameter space that however continue to favour dark energy with w < -1 at early times, that is challenging to realize in consistent theories. Next, in the spirit of effective field theories, we consider the effect of higher order terms in the Taylor expansion of the equation of state of dark energy around the present epoch. We find that non-linear corrections of the equation of state are weakly constrained, thus opening the way to scenarios that differ from CPL at early times, possibly with w > -1 at all times. We present indeed scenarios where evolving dark energy can be realized through quintessence models. We introduce in particular the ramp model where dark energy coincides with CPL at late times and approximates to a cosmological constant at early times. The latter model provides a much better fit than ΛCDM, and only slightly worse than w0waCDM, but with the notable advantage of being described by a simple and theoretically consistent lagrangian of a canonical quintessence model.
我们通过对 DESI、普朗克和超新星数据的宇宙学拟合，寻找物理上一致的演化暗能量的实现方式。首先，我们注意到暗能量状态方程 w 的标准切瓦利埃-波兰斯基-林德（CPL）参数的任何拉格朗日描述都允许添加一个宇宙学常数。我们进行了宇宙学拟合，发现了参数空间的新区域，然而这些区域在早期继续倾向于 w < -1 的暗能量，这在一致理论中是难以实现的。接下来，本着有效场理论的精神，我们考虑了暗能量状态方程泰勒扩展中的高阶项在本纪附近的影响。我们发现，状态方程的非线性修正受到弱约束，从而为早期不同于CPL的情景开辟了道路，可能在任何时候w都>-1。我们确实提出了可以通过五重模型实现暗能量演化的情景。我们特别介绍了斜坡模型，即暗能量在晚期与CPL重合，而在早期近似于宇宙常数。后一种模型的拟合效果比ΛCDM好得多，只比w0waCDM稍差一些，但它有一个显著的优点，即可以用一个简单的、理论上一致的经典五元模型的拉格朗日来描述。
{"title":"Consistent theories for the DESI dark energy fit","authors":"Alessio Notari, Michele Redi and Andrea Tesi","doi":"10.1088/1475-7516/2024/11/025","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/11/025","url":null,"abstract":"We search for physically consistent realizations of evolving dark energy suggested by the cosmological fit of DESI, Planck and Supernovae data. First we note that any lagrangian description of the standard Chevallier-Polarski-Linder (CPL) parametrization for the dark energy equation of state w, allows for the addition of a cosmological constant. We perform the cosmological fit finding new regions of parameter space that however continue to favour dark energy with w < -1 at early times, that is challenging to realize in consistent theories. Next, in the spirit of effective field theories, we consider the effect of higher order terms in the Taylor expansion of the equation of state of dark energy around the present epoch. We find that non-linear corrections of the equation of state are weakly constrained, thus opening the way to scenarios that differ from CPL at early times, possibly with w > -1 at all times. We present indeed scenarios where evolving dark energy can be realized through quintessence models. We introduce in particular the ramp model where dark energy coincides with CPL at late times and approximates to a cosmological constant at early times. The latter model provides a much better fit than ΛCDM, and only slightly worse than w0waCDM, but with the notable advantage of being described by a simple and theoretically consistent lagrangian of a canonical quintessence model.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"106 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142671010","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 : 2024-11-19DOI: 10.1088/1475-7516/2024/11/028
Yi Zhang, Hong Liu, Dan Wen and Hongsheng Zhang
For the first time, we use the Event Horizon Telescope (EHT) data to constrain the parameters of braneworld black holes which constrain ϵ = 0.0285+0.0888+0.1456-0.0895-0.1475 for the anisotropic black hole and q = -0.0305+0.1034+0.1953-0.0895-0.1470 for the tidal Reissner-Nordström (RN) black hole. Based on the fitted data and physical requirement, we calculate the photon deflection, the angular separation and time delay between different relativistic images of the anisotropic black hole and the tidal RN black hole in the ranges -0.1190 < ϵ < 0 and -0.1775 < q < 0. And furthermore, we study the quasinormal modes (QNMs) for the braneworld black holes. The results shed light on existence of extra dimension.
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Pub Date : 2024-11-19DOI: 10.1088/1475-7516/2024/11/027
Massimo Giovannini
Stationary processes do not accurately describe the diffuse backgrounds of relic gravitons whose correlations are homogeneous in space (i.e. only dependent upon the distance between the two spatial locations) but not in time. The symmetries of the autocorrelations ultimately reflect the quantum mechanical origin of the diffuse backgrounds and lead to non-stationary observables at late time. In particular, large oscillations are believed to arise in the spectral energy density that is customarily (but approximately) related to the tensor power spectrum. When the full expression of the spectral energy density is employed the amplitudes of oscillation are instead suppressed in the large-scale limit and the non-stationary features of the late-time signal practically disappear. For similar reasons the relations between the spectral energy density and the spectral amplitude are ambiguous in the presence of non-stationary features. While it is debatable if the non-stationary features are (or will be) directly detectable, we argue that the spectral amplitude following from the Wiener-Khintchine theorem is generally inappropriate for a consistent description of the relic signal. Nevertheless the strong oscillatory behaviour of the late-time observables is naturally smeared out provided the spectral energy density is selected as pivotal variable.
{"title":"Relic gravitons and non-stationary processes","authors":"Massimo Giovannini","doi":"10.1088/1475-7516/2024/11/027","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/11/027","url":null,"abstract":"Stationary processes do not accurately describe the diffuse backgrounds of relic gravitons whose correlations are homogeneous in space (i.e. only dependent upon the distance between the two spatial locations) but not in time. The symmetries of the autocorrelations ultimately reflect the quantum mechanical origin of the diffuse backgrounds and lead to non-stationary observables at late time. In particular, large oscillations are believed to arise in the spectral energy density that is customarily (but approximately) related to the tensor power spectrum. When the full expression of the spectral energy density is employed the amplitudes of oscillation are instead suppressed in the large-scale limit and the non-stationary features of the late-time signal practically disappear. For similar reasons the relations between the spectral energy density and the spectral amplitude are ambiguous in the presence of non-stationary features. While it is debatable if the non-stationary features are (or will be) directly detectable, we argue that the spectral amplitude following from the Wiener-Khintchine theorem is generally inappropriate for a consistent description of the relic signal. Nevertheless the strong oscillatory behaviour of the late-time observables is naturally smeared out provided the spectral energy density is selected as pivotal variable.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"18 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142671018","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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