Pub Date : 2026-03-25DOI: 10.1088/1475-7516/2026/03/075
P. Béchaz, G. Fanizza, G. Marozzi and M.R. Medeiros Silva
We develop a second-order cosmological perturbation theory on a background geometry expressed in terms of light-cone coordinates, extending the first-order analyses available in the literature. In particular, we investigate the gauge transformations of second-order perturbative quantities on the light-cone and establish their connection with standard perturbation theory. Through a consistent matching procedure, we identify the second-order gauge fixing that corresponds to the non-linear Geodesic Light-Cone gauge within standard perturbation theory, known as the Observational Synchronous Gauge. We then emphasize its conceptual similarities and differences w.r.t. the standard Synchronous Gauge. Finally, within this new perturbative framework, and adopting a fully gauge-invariant approach, we compute the luminosity distance-redshift relation up to second order with anisotropic stress as seen by a free-falling observer. Remarkably, we show how divergences at the observer position can be eliminated in a completely model-independent way. These results validate our perturbative framework and establish it as a novel formalism for evaluating cosmological observables at second order.
{"title":"A light-cone approach to higher-order cosmological observables","authors":"P. Béchaz, G. Fanizza, G. Marozzi and M.R. Medeiros Silva","doi":"10.1088/1475-7516/2026/03/075","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/075","url":null,"abstract":"We develop a second-order cosmological perturbation theory on a background geometry expressed in terms of light-cone coordinates, extending the first-order analyses available in the literature. In particular, we investigate the gauge transformations of second-order perturbative quantities on the light-cone and establish their connection with standard perturbation theory. Through a consistent matching procedure, we identify the second-order gauge fixing that corresponds to the non-linear Geodesic Light-Cone gauge within standard perturbation theory, known as the Observational Synchronous Gauge. We then emphasize its conceptual similarities and differences w.r.t. the standard Synchronous Gauge. Finally, within this new perturbative framework, and adopting a fully gauge-invariant approach, we compute the luminosity distance-redshift relation up to second order with anisotropic stress as seen by a free-falling observer. Remarkably, we show how divergences at the observer position can be eliminated in a completely model-independent way. These results validate our perturbative framework and establish it as a novel formalism for evaluating cosmological observables at second order.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"21 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-25DOI: 10.1088/1475-7516/2026/03/078
Alexa Bartlett, Joseph DeRose and Martin White
In this work, we forecast the number of, and requirements on, N-body simulations needed to train hybrid effective field theory (HEFT) emulators for a range of use cases, using a hybrid of HMcode and perturbation theory as a surrogate model. Our accuracy goals, determined with careful consideration of statistical and systematic uncertainties, are 1% accurate in the high-likelihood range of cosmological parameters, and 2% accurate over a broader parameter space volume for k < 1 h Mpc-1 and z < 3. Focusing in part on the 8-parameter w0waCDM+mν cosmological model, we find that < 225 simulations are required to meet our error goals over our wide parameter space, including models with rapidly evolving dark energy, given our simulation and emulator recommendations. For a more restricted parameter space volume, as few as 80 simulations are sufficient. We additionally present simulation forecasts for example use cases, and make the code used in our analyses publicly available. These results offer practical guidance for efficient emulator design and simulation budgeting in future cosmological analyses.
在这项工作中，我们使用HMcode和微扰理论的混合模型作为替代模型，预测了训练混合有效场理论（HEFT）模拟器所需的n体仿真的数量和需求。我们的精度目标是在仔细考虑统计和系统不确定性的情况下确定的，在宇宙学参数的高似然范围内精度为1%，在k < 1 h Mpc-1和z < 3的更广泛的参数空间体积内精度为2%。部分关注8参数w0waCDM+mν宇宙学模型，我们发现需要< 225次模拟才能满足我们在宽参数空间中的误差目标，包括具有快速演化暗能量的模型，鉴于我们的仿真和模拟器建议。对于更受限制的参数空间体积，只需80次模拟就足够了。另外，我们还为示例用例提供模拟预测，并使我们分析中使用的代码公开可用。这些结果对未来宇宙分析中有效的仿真器设计和仿真预算具有实际指导意义。
{"title":"Simulation budgeting for hybrid effective field theories","authors":"Alexa Bartlett, Joseph DeRose and Martin White","doi":"10.1088/1475-7516/2026/03/078","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/078","url":null,"abstract":"In this work, we forecast the number of, and requirements on, N-body simulations needed to train hybrid effective field theory (HEFT) emulators for a range of use cases, using a hybrid of HMcode and perturbation theory as a surrogate model. Our accuracy goals, determined with careful consideration of statistical and systematic uncertainties, are 1% accurate in the high-likelihood range of cosmological parameters, and 2% accurate over a broader parameter space volume for k < 1 h Mpc-1 and z < 3. Focusing in part on the 8-parameter w0waCDM+mν cosmological model, we find that < 225 simulations are required to meet our error goals over our wide parameter space, including models with rapidly evolving dark energy, given our simulation and emulator recommendations. For a more restricted parameter space volume, as few as 80 simulations are sufficient. We additionally present simulation forecasts for example use cases, and make the code used in our analyses publicly available. These results offer practical guidance for efficient emulator design and simulation budgeting in future cosmological analyses.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"16 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-25DOI: 10.1088/1475-7516/2026/03/077
Toshiki Takadera, Shin'ichi Hirano and Tsutomu Kobayashi
Cosmic voids in the large-scale structure are among the useful probes for testing gravity on cosmological scales. In this paper, we investigate the evolution of voids in the Horndeski theory using the effective field theory (EFT) of dark energy. Modeling the void formation with the dynamics of spherical mass shells, we study how modifications of gravity encoded into the EFT of dark energy change the linearly extrapolated critical density contrast that is relevant for the criterion for void formation, with particular focus on the time-dependent parameter characterizing the effect of kinetic braiding. It is found that the change in the critical density contrast is one order of magnitude smaller than the dimensionless EFT parameter because of a slight imbalance between two compensating effects. We then compute the void abundance using the Sheth-van de Weygaert void size function and demonstrate that it exhibits scale-dependent modifications. It is shown that the modifications to the void size function on small scales are almost entirely determined by the modified linear matter power spectrum, while the modifications on large scales are dominated by the contributions from the linear matter spectrum and the critical density contrast.
大尺度结构中的宇宙空洞是在宇宙尺度上测试重力的有用探测器之一。本文利用暗能量的有效场论（EFT）研究了Horndeski理论中空洞的演化。通过球形质量壳的动力学建模，我们研究了编码到暗能量EFT中的重力变化如何改变与空洞形成标准相关的线性外推临界密度对比，特别关注表征动力学编织效应的时间相关参数。结果表明，由于两种补偿效应之间的轻微不平衡，临界密度对比度的变化比无量纲EFT参数的变化小一个数量级。然后，我们使用Sheth-van de Weygaert空隙尺寸函数计算空隙丰度，并证明它具有尺度相关的修改。结果表明，在小尺度上对空洞尺寸函数的修正几乎完全由修正后的线性物质功率谱决定，而在大尺度上对空洞尺寸函数的修正主要由线性物质谱和临界密度对比的贡献决定。
{"title":"Abundance of cosmic voids in EFT of dark energy","authors":"Toshiki Takadera, Shin'ichi Hirano and Tsutomu Kobayashi","doi":"10.1088/1475-7516/2026/03/077","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/077","url":null,"abstract":"Cosmic voids in the large-scale structure are among the useful probes for testing gravity on cosmological scales. In this paper, we investigate the evolution of voids in the Horndeski theory using the effective field theory (EFT) of dark energy. Modeling the void formation with the dynamics of spherical mass shells, we study how modifications of gravity encoded into the EFT of dark energy change the linearly extrapolated critical density contrast that is relevant for the criterion for void formation, with particular focus on the time-dependent parameter characterizing the effect of kinetic braiding. It is found that the change in the critical density contrast is one order of magnitude smaller than the dimensionless EFT parameter because of a slight imbalance between two compensating effects. We then compute the void abundance using the Sheth-van de Weygaert void size function and demonstrate that it exhibits scale-dependent modifications. It is shown that the modifications to the void size function on small scales are almost entirely determined by the modified linear matter power spectrum, while the modifications on large scales are dominated by the contributions from the linear matter spectrum and the critical density contrast.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"78 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-25DOI: 10.1088/1475-7516/2026/03/079
Gerardo Morales-Navarrete and Jorge L. Cervantes-Cota
We make use of the perturbation theory for modified gravity models that we developed in previous works and apply it to construct the fullshape galaxy power spectrum for the Symmetron modified gravity model. First, we study the growth rate, that is a scale dependent quantity, and compare our results with those of the n = 1 Hu-Sawcki (HS) model, finding that the Symmetron has a growth quite similar to the HS F6 in the wavenumber interval 0.01 ≤ k ≤ 0.1 and for redshifts where Symmetron model is viable. We also propose a growth parametrization that turns to be a good approximation for the HS and Symmetron models, with a deviation less than 0.6 %. To compute the RSD multipoles we employ an expansion of the velocity moments generating function that is suitable for general modified gravity models. Later, we apply the fk-Perturbation Theory (fkPT) approximation to reduce the computation time of nonlinear kernels, to find the fullshape galaxy power spectrum for the Symmetron, and study the differences with HS model. The RSD multipoles of the Symmetron result similar to those of the HS F6 model. Next, we integrate this theory to an MCMC sampler and validate our results by fitting our parameters to EZMocks to recover the parameters that bring the model to GR. We found a similar agreement in the model validation between Symmetron and F6 model, recovering the simulation cosmological parameters, and concluding that our pipeline is ready to make cosmological parameters' inference with real data.
{"title":"Fullshape power spectrum for the Symmetron modified gravity model","authors":"Gerardo Morales-Navarrete and Jorge L. Cervantes-Cota","doi":"10.1088/1475-7516/2026/03/079","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/079","url":null,"abstract":"We make use of the perturbation theory for modified gravity models that we developed in previous works and apply it to construct the fullshape galaxy power spectrum for the Symmetron modified gravity model. First, we study the growth rate, that is a scale dependent quantity, and compare our results with those of the n = 1 Hu-Sawcki (HS) model, finding that the Symmetron has a growth quite similar to the HS F6 in the wavenumber interval 0.01 ≤ k ≤ 0.1 and for redshifts where Symmetron model is viable. We also propose a growth parametrization that turns to be a good approximation for the HS and Symmetron models, with a deviation less than 0.6 %. To compute the RSD multipoles we employ an expansion of the velocity moments generating function that is suitable for general modified gravity models. Later, we apply the fk-Perturbation Theory (fkPT) approximation to reduce the computation time of nonlinear kernels, to find the fullshape galaxy power spectrum for the Symmetron, and study the differences with HS model. The RSD multipoles of the Symmetron result similar to those of the HS F6 model. Next, we integrate this theory to an MCMC sampler and validate our results by fitting our parameters to EZMocks to recover the parameters that bring the model to GR. We found a similar agreement in the model validation between Symmetron and F6 model, recovering the simulation cosmological parameters, and concluding that our pipeline is ready to make cosmological parameters' inference with real data.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"4 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-25DOI: 10.1088/1475-7516/2026/03/076
Hananeh Sadat Modirzadeh, Raihaneh Moti and Mohammad Hossein Namjoo
Non-relativistic effective field theories (NREFTs) play a crucial role in various areas of physics, from cold atom experiments to cosmology. In this paper, we present a systematic framework for deriving NREFTs from relativistic theories with generic self-interactions. Our approach allows for (but is not limited to) non-power-law potentials (such as those arising from dilatons or axions) or potentials that are non-analytic around the classical vacuum (such as those with logarithmic radiative corrections). These are of theoretical and phenomenological interest but have largely been unexplored in the non-relativistic regime. NREFTs are typically viewed as approximations for systems with low velocities, weak couplings, and small field amplitudes. The latter assumption is relaxed in our approach, as long as the mass term remains dominant (ensuring the validity of the non-relativistic limit). Additionally, we establish an effective fluid description for the non-relativistic scalar field, identifying key quantities such as energy density, pressure, and sound speed. To enable cosmological applications, we extend our formalism to account for the expanding universe, providing a reliable tool for investigating ultra-light dark matter models with arbitrary self-interactions. Finally, we demonstrate the applicability of our NREFT in analyzing solitons, which is also relevant to cosmology for studying celestial objects such as boson stars and the cores of dark matter halos.
{"title":"Non-relativistic effective theories for fields with general potentials and their implications for cosmology","authors":"Hananeh Sadat Modirzadeh, Raihaneh Moti and Mohammad Hossein Namjoo","doi":"10.1088/1475-7516/2026/03/076","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/076","url":null,"abstract":"Non-relativistic effective field theories (NREFTs) play a crucial role in various areas of physics, from cold atom experiments to cosmology. In this paper, we present a systematic framework for deriving NREFTs from relativistic theories with generic self-interactions. Our approach allows for (but is not limited to) non-power-law potentials (such as those arising from dilatons or axions) or potentials that are non-analytic around the classical vacuum (such as those with logarithmic radiative corrections). These are of theoretical and phenomenological interest but have largely been unexplored in the non-relativistic regime. NREFTs are typically viewed as approximations for systems with low velocities, weak couplings, and small field amplitudes. The latter assumption is relaxed in our approach, as long as the mass term remains dominant (ensuring the validity of the non-relativistic limit). Additionally, we establish an effective fluid description for the non-relativistic scalar field, identifying key quantities such as energy density, pressure, and sound speed. To enable cosmological applications, we extend our formalism to account for the expanding universe, providing a reliable tool for investigating ultra-light dark matter models with arbitrary self-interactions. Finally, we demonstrate the applicability of our NREFT in analyzing solitons, which is also relevant to cosmology for studying celestial objects such as boson stars and the cores of dark matter halos.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"52 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-25DOI: 10.1088/1475-7516/2026/03/074
Virgile Dandoy, Christian Döring, Gaétan Facchinetti, Laura Lopez-Honorez and Justus Roman Schwagereit
The 21 cm signal originating from Cosmic Dawn to the Epoch of Reionisation is highly sensitive to the processes governing star formation in the early universe as well as new physics. In this work, we focus on the imprint of non-cold dark matter (DM), which impacts the formation of the smallest halos. Our goal in particular is to clarify whether near-future radio telescopes such as the Hydrogen Epoch of Reionisation Array (HERA), will be able to distinguish between free-streaming dark matter, specifically in the form of thermal warm DM (WDM), and collisional damping due to neutrino-DM (νDM) interactions giving rise to larger overdensities on small scales. For that purpose we first implement a mapping between the two models in terms of a cutoff scale and determine detection thresholds for the two DM models. Using Fisher matrix forecasts, we show that νDM interaction strengths down to σνDM ∼ 3×10-35 cm2 could be probed by 21 cm cosmology when considering two populations of galaxies for a GeV mass DM. This would allow to either confirm or rule out a recent claimed preference for a non-zero νDM interaction in Lyman-α data. Furthermore, we find that HERA will not be able to distinguish between νDM and WDM. In the latter context, the threshold for detection of νDM interactions translates into WDM with mass up to mWDM ∼ 9 keV that could be detected by HERA.
{"title":"21 cm cosmology sensitivity to small-scale structure: warm vs. neutrino-interacting dark matter","authors":"Virgile Dandoy, Christian Döring, Gaétan Facchinetti, Laura Lopez-Honorez and Justus Roman Schwagereit","doi":"10.1088/1475-7516/2026/03/074","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/074","url":null,"abstract":"The 21 cm signal originating from Cosmic Dawn to the Epoch of Reionisation is highly sensitive to the processes governing star formation in the early universe as well as new physics. In this work, we focus on the imprint of non-cold dark matter (DM), which impacts the formation of the smallest halos. Our goal in particular is to clarify whether near-future radio telescopes such as the Hydrogen Epoch of Reionisation Array (HERA), will be able to distinguish between free-streaming dark matter, specifically in the form of thermal warm DM (WDM), and collisional damping due to neutrino-DM (νDM) interactions giving rise to larger overdensities on small scales. For that purpose we first implement a mapping between the two models in terms of a cutoff scale and determine detection thresholds for the two DM models. Using Fisher matrix forecasts, we show that νDM interaction strengths down to σνDM ∼ 3×10-35 cm2 could be probed by 21 cm cosmology when considering two populations of galaxies for a GeV mass DM. This would allow to either confirm or rule out a recent claimed preference for a non-zero νDM interaction in Lyman-α data. Furthermore, we find that HERA will not be able to distinguish between νDM and WDM. In the latter context, the threshold for detection of νDM interactions translates into WDM with mass up to mWDM ∼ 9 keV that could be detected by HERA.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"31 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-25DOI: 10.1088/1475-7516/2026/03/080
Stephon Alexander, Geoff Beck, Santiago Loane and Tucker Manton
Axions are a leading dark matter candidate. In this work, we study the detectability of a multi-axion-like model, dubbed the π-axiverse, that is distinguishable from the string axiverse. The dark matter candidates are N2-1 pseudo-Nambu-Goto modes (pion- and kaon-like states) stemming from spontaneous breaking of a global SU(N) flavor symmetry. The low energy theory includes N-1 axionic couplings with additional couplings to the Standard Model photon kinetic energy, reminiscent of the string theory dilaton-photon coupling. We explore the parametric resonance of photons interacting with such a dark sector. Axions are well known to form macroscopic solitonic-like objects (axion stars), which experience instabilities due to overdensities stemming from mergers or accretion processes. The instabilities produce high-intensity bursts of radiation via parametric resonance that may be detected at observatories such as MeerKAT, the Square Kilometre Array (SKA), and the next generation Very Large Array (ngVLA). Using numerical methods, we systematically explore the multi-dimensional parameter space of the π-axiverse to search for regions where such signals are detectable, which generically differ from single axion models. We identify regions of the parameter space where MeerKAT, SKA, and ngVLA can resolve such signals, assessing the potential of transient searches to constrain the model. Our results provide a significant step forward in understanding the phenomenology and indirect detection of multi-axion-dilaton dark matter.
{"title":"Detecting the π-axiverse through parametric resonance","authors":"Stephon Alexander, Geoff Beck, Santiago Loane and Tucker Manton","doi":"10.1088/1475-7516/2026/03/080","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/080","url":null,"abstract":"Axions are a leading dark matter candidate. In this work, we study the detectability of a multi-axion-like model, dubbed the π-axiverse, that is distinguishable from the string axiverse. The dark matter candidates are N2-1 pseudo-Nambu-Goto modes (pion- and kaon-like states) stemming from spontaneous breaking of a global SU(N) flavor symmetry. The low energy theory includes N-1 axionic couplings with additional couplings to the Standard Model photon kinetic energy, reminiscent of the string theory dilaton-photon coupling. We explore the parametric resonance of photons interacting with such a dark sector. Axions are well known to form macroscopic solitonic-like objects (axion stars), which experience instabilities due to overdensities stemming from mergers or accretion processes. The instabilities produce high-intensity bursts of radiation via parametric resonance that may be detected at observatories such as MeerKAT, the Square Kilometre Array (SKA), and the next generation Very Large Array (ngVLA). Using numerical methods, we systematically explore the multi-dimensional parameter space of the π-axiverse to search for regions where such signals are detectable, which generically differ from single axion models. We identify regions of the parameter space where MeerKAT, SKA, and ngVLA can resolve such signals, assessing the potential of transient searches to constrain the model. Our results provide a significant step forward in understanding the phenomenology and indirect detection of multi-axion-dilaton dark matter.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"23 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-24DOI: 10.1088/1475-7516/2026/03/069
Lucy Brissenden, Konstantinos Dimopoulos and Eemeli Tomberg
Cosmic inflation is the leading theory to explain early Universe history and structure formation. Non-oscillatory inflation is a class of models which can naturally introduce a post-inflationary stiff period of the Universe's evolution which boosts the signal of primordial gravitational waves (GWs), making it possible to observe them in forthcoming GW experiments. However, this pushes the GW energy density high enough to destabilise the process of Big Bang Nucleosynthesis (BBN). This problem can be overcome by “softening” the stiff period, so that the field is gradually tending towards freefall from a frozen start. Here, we consider a modified hybrid inflation model where the stiff period is driven by the waterfall field, allowing the barotropic parameter of the Universe to vary, so that it does not violate the ΔNeff constraint but produces a characteristic gravitational wave spectrum soon to be observable.
{"title":"Evading the BBN bound with a soft stiff period","authors":"Lucy Brissenden, Konstantinos Dimopoulos and Eemeli Tomberg","doi":"10.1088/1475-7516/2026/03/069","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/069","url":null,"abstract":"Cosmic inflation is the leading theory to explain early Universe history and structure formation. Non-oscillatory inflation is a class of models which can naturally introduce a post-inflationary stiff period of the Universe's evolution which boosts the signal of primordial gravitational waves (GWs), making it possible to observe them in forthcoming GW experiments. However, this pushes the GW energy density high enough to destabilise the process of Big Bang Nucleosynthesis (BBN). This problem can be overcome by “softening” the stiff period, so that the field is gradually tending towards freefall from a frozen start. Here, we consider a modified hybrid inflation model where the stiff period is driven by the waterfall field, allowing the barotropic parameter of the Universe to vary, so that it does not violate the ΔNeff constraint but produces a characteristic gravitational wave spectrum soon to be observable.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"148 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-24DOI: 10.1088/1475-7516/2026/03/068
J.-H. Ha and I. Alikhanov
Blazars, particularly Flat Spectrum Radio Quasars (FSRQs), are well-known for their ability to accelerate a substantial population of electrons and positrons, as inferred from multiwavelength radiation observations. Therefore, these astrophysical objects are promising candidates for studying high-energy electron-positron interactions, such as the production of W± and Z bosons. In this work, we explore the implications of electron-positron annihilation processes in the jet environments of FSRQs, focusing on the resonant production of electroweak bosons and their potential contribution to the diffuse neutrino flux. By modeling the electron distribution in the jet of the FSRQ 3C 279 during a flaring state, we calculate the reaction rates for W± and Z bosons and estimate the resulting diffuse fluxes from the cosmological population of FSRQs. We incorporate the FSRQ luminosity function and its redshift evolution to account for the population distribution across cosmic time, finding that the differential flux contribution exhibits a pronounced peak at redshift z ∼ 1. While the expected fluxes remain well below the detection thresholds of current neutrino observatories such as IceCube, KM3NeT, or Baikal-GVD, the flux from Z boson production within the jet blob is many orders of magnitude smaller than the total diffuse astrophysical neutrino flux. These results provide a theoretical benchmark for the role of Standard Model electroweak processes in extreme astrophysical environments, highlighting the interplay between particle physics and astrophysics, and illustrating that even extremely rare high-energy interactions can leave a subtle, theoretically meaningful imprint on the diffuse astrophysical neutrino background.
{"title":"Resonant W and Z boson production in FSRQ jets: implications for diffuse neutrino fluxes","authors":"J.-H. Ha and I. Alikhanov","doi":"10.1088/1475-7516/2026/03/068","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/068","url":null,"abstract":"Blazars, particularly Flat Spectrum Radio Quasars (FSRQs), are well-known for their ability to accelerate a substantial population of electrons and positrons, as inferred from multiwavelength radiation observations. Therefore, these astrophysical objects are promising candidates for studying high-energy electron-positron interactions, such as the production of W± and Z bosons. In this work, we explore the implications of electron-positron annihilation processes in the jet environments of FSRQs, focusing on the resonant production of electroweak bosons and their potential contribution to the diffuse neutrino flux. By modeling the electron distribution in the jet of the FSRQ 3C 279 during a flaring state, we calculate the reaction rates for W± and Z bosons and estimate the resulting diffuse fluxes from the cosmological population of FSRQs. We incorporate the FSRQ luminosity function and its redshift evolution to account for the population distribution across cosmic time, finding that the differential flux contribution exhibits a pronounced peak at redshift z ∼ 1. While the expected fluxes remain well below the detection thresholds of current neutrino observatories such as IceCube, KM3NeT, or Baikal-GVD, the flux from Z boson production within the jet blob is many orders of magnitude smaller than the total diffuse astrophysical neutrino flux. These results provide a theoretical benchmark for the role of Standard Model electroweak processes in extreme astrophysical environments, highlighting the interplay between particle physics and astrophysics, and illustrating that even extremely rare high-energy interactions can leave a subtle, theoretically meaningful imprint on the diffuse astrophysical neutrino background.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"15 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-24DOI: 10.1088/1475-7516/2026/03/070
Guillem Domènech, Alexander Ganz, Mohammad Ali Gorji and Masahide Yamaguchi
We study gravitational waves induced by scalar primordial fluctuations in Gleyzes-Langlois-Piazza-Vernizzi (GLPV), beyond Horndeski, scalar-tensor theories. We uncover, at the level of the action, a new scalar-scalar-tensor interaction, unique to GLPV models disconnected from Horndeski via disformal transformation. The new interaction, arising in the unitary-degenerate (U-DHOST) sector of GLPV, leads to third derivatives in the source for scalar-induced tensor modes, which are absent in Horndeski-related theories. Such new higher-derivative terms lead to a further enhanced production of induced gravitational waves. We predict that for a scale-invariant primordial spectrum, the induced gravitational wave spectral density has a characteristic frequency dependence proportional to f5. Such a fast-rising spectrum offers a potential unique signature of modified gravity in the early universe.
{"title":"Unique gravitational wave signatures of GLPV scalar-tensor theories","authors":"Guillem Domènech, Alexander Ganz, Mohammad Ali Gorji and Masahide Yamaguchi","doi":"10.1088/1475-7516/2026/03/070","DOIUrl":"https://doi.org/10.1088/1475-7516/2026/03/070","url":null,"abstract":"We study gravitational waves induced by scalar primordial fluctuations in Gleyzes-Langlois-Piazza-Vernizzi (GLPV), beyond Horndeski, scalar-tensor theories. We uncover, at the level of the action, a new scalar-scalar-tensor interaction, unique to GLPV models disconnected from Horndeski via disformal transformation. The new interaction, arising in the unitary-degenerate (U-DHOST) sector of GLPV, leads to third derivatives in the source for scalar-induced tensor modes, which are absent in Horndeski-related theories. Such new higher-derivative terms lead to a further enhanced production of induced gravitational waves. We predict that for a scale-invariant primordial spectrum, the induced gravitational wave spectral density has a characteristic frequency dependence proportional to f5. Such a fast-rising spectrum offers a potential unique signature of modified gravity in the early universe.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"14 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147506760","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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