Pub Date : 2024-10-21DOI: 10.1088/1475-7516/2024/10/071
F.B.M. dos Santos, R. de Souza and J.S. Alcaniz
In the warm inflation scenario, the early cosmic acceleration is driven by the inflaton coupled to thermal fields, decaying into radiation and leaving a hot universe populated by relativistic particles after the end of inflation. The interaction is usually modeled by a dissipation coefficient Υ that contains the microphysics of the model. In this work, we adopt a well-motivated potential V(ϕ)=λ/4ϕ4 and constrain a variety of Υ parameterizations by using updated Cosmic Microwave Background data from the Planck and BICEP/Keck Array collaborations. We also use a Bayesian statistical criterion to compare the observational viability of these models. Our results show a significant improvement in the constraints over past results reported in the literature and also that some of these warm inflation models can be competitive compared to Starobinsky inflation.
{"title":"A comparative analysis of dissipation coefficients in warm inflation","authors":"F.B.M. dos Santos, R. de Souza and J.S. Alcaniz","doi":"10.1088/1475-7516/2024/10/071","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/10/071","url":null,"abstract":"In the warm inflation scenario, the early cosmic acceleration is driven by the inflaton coupled to thermal fields, decaying into radiation and leaving a hot universe populated by relativistic particles after the end of inflation. The interaction is usually modeled by a dissipation coefficient Υ that contains the microphysics of the model. In this work, we adopt a well-motivated potential V(ϕ)=λ/4ϕ4 and constrain a variety of Υ parameterizations by using updated Cosmic Microwave Background data from the Planck and BICEP/Keck Array collaborations. We also use a Bayesian statistical criterion to compare the observational viability of these models. Our results show a significant improvement in the constraints over past results reported in the literature and also that some of these warm inflation models can be competitive compared to Starobinsky inflation.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"210 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486749","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 : 2024-10-21DOI: 10.1088/1475-7516/2024/10/066
Tieguang Zi, Chang-Qing Ye and Peng-Cheng Li
The horizon of a classical black hole (BH), functioning as a one-way membrane, plays a vital role in the dynamic evolution of binary BHs, capable of absorbing fluxes entirely. Tidal heating, stemming from this phenomenon, exerts a notable influence on the production of gravitational waves (GWs). If at least one member of a binary is an exotic compact object (ECO) instead of a BH, the absorption of fluxes is expected to be incomplete and the tidal heating would be different. Thus, tidal heating can be utilized for model-independent investigations into the nature of compact object. In this paper, assuming that the extreme mass-ratio inspiral (EMRI) contains a stellar-mass compact object orbiting around a massive ECO with a reflective surface, we compute the GWs from the generic EMRI orbits. Using the accurate and analytic flux formulas in the black hole spacetime, we adapted these formulas in the vicinity of the ECO surface by incorporating a reflectivity parameter. Under the adiabatic approximation, we can evolve the orbital parameters and compute the EMRI waveforms. The effect of tidal heating for the spinning and non-spinning objects can be used to constrain the reflectivity of the surface at the level of 𝒪(10-6) by computing the mismatch and fisher information matrix.
经典黑洞（BH）的视界是一个单向膜，在双黑洞的动态演化过程中起着至关重要的作用，能够完全吸收通量。由这一现象产生的潮汐加热对引力波（GWs）的产生有着显著的影响。如果双星中至少有一个成员是外来紧凑天体（ECO）而不是 BH，那么对通量的吸收预计将是不完全的，潮汐加热也会有所不同。因此，潮汐加热可以用来研究紧凑天体的性质，而不依赖于模型。在本文中，我们假定极端质量比吸积（EMRI）包含一个恒星质量的紧凑天体，围绕一个具有反射面的大质量 ECO 运行，计算一般 EMRI 轨道的 GWs。利用黑洞时空中精确的解析通量公式，我们在 ECO 表面附近调整了这些公式，加入了一个反射率参数。在绝热近似条件下，我们可以演化轨道参数并计算 EMRI 波形。旋转和非旋转物体的潮汐加热效应可以通过计算错配和渔夫信息矩阵，在𝒪(10-6)的水平上约束表面的反射率。
{"title":"Detecting the tidal heating with the generic extreme mass-ratio inspirals","authors":"Tieguang Zi, Chang-Qing Ye and Peng-Cheng Li","doi":"10.1088/1475-7516/2024/10/066","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/10/066","url":null,"abstract":"The horizon of a classical black hole (BH), functioning as a one-way membrane, plays a vital role in the dynamic evolution of binary BHs, capable of absorbing fluxes entirely. Tidal heating, stemming from this phenomenon, exerts a notable influence on the production of gravitational waves (GWs). If at least one member of a binary is an exotic compact object (ECO) instead of a BH, the absorption of fluxes is expected to be incomplete and the tidal heating would be different. Thus, tidal heating can be utilized for model-independent investigations into the nature of compact object. In this paper, assuming that the extreme mass-ratio inspiral (EMRI) contains a stellar-mass compact object orbiting around a massive ECO with a reflective surface, we compute the GWs from the generic EMRI orbits. Using the accurate and analytic flux formulas in the black hole spacetime, we adapted these formulas in the vicinity of the ECO surface by incorporating a reflectivity parameter. Under the adiabatic approximation, we can evolve the orbital parameters and compute the EMRI waveforms. The effect of tidal heating for the spinning and non-spinning objects can be used to constrain the reflectivity of the surface at the level of 𝒪(10-6) by computing the mismatch and fisher information matrix.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"19 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486746","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 : 2024-10-21DOI: 10.1088/1475-7516/2024/10/068
Gargi Sen, Debaprasad Maity and Santabrata Das
We investigate the structure of relativistic, low-angular momentum, inviscid advective accretion flow in a stationary axisymmetric Kerr-like wormhole (WH) spacetime, characterized by the spin parameter (ak), the dimensionless parameter (β), and the source mass (MWH). In doing so, we self-consistently solve the set of governing equations describing the relativistic accretion flow around a Kerr-like WH in the steady state, and for the first time, we obtain all possible classes of global accretion solutions for transonic as well as subsonic flows. We study the properties of dynamical and thermodynamical flow variables and examine how the nature of the accretion solutions alters due to the change of the model parameters, namely energy (ℰ), angular momentum (λ), ak, and β. Further, we separate the parameter space in λ-ℰ plane according to the nature of the flow solutions, and study the modification of the parameter space by varying ak and β. Moreover, we retrace the parameter space in ak-β plane that allows accretion solutions containing multiple critical points. Finally, we calculate the disc luminosity (L) considering free-free emissions for transonic solutions as these solutions are astrophysically relevant and discuss the implication of this model formalism in the context of astrophysical applications.
{"title":"Study of relativistic hot accretion flow around Kerr-like wormhole","authors":"Gargi Sen, Debaprasad Maity and Santabrata Das","doi":"10.1088/1475-7516/2024/10/068","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/10/068","url":null,"abstract":"We investigate the structure of relativistic, low-angular momentum, inviscid advective accretion flow in a stationary axisymmetric Kerr-like wormhole (WH) spacetime, characterized by the spin parameter (ak), the dimensionless parameter (β), and the source mass (MWH). In doing so, we self-consistently solve the set of governing equations describing the relativistic accretion flow around a Kerr-like WH in the steady state, and for the first time, we obtain all possible classes of global accretion solutions for transonic as well as subsonic flows. We study the properties of dynamical and thermodynamical flow variables and examine how the nature of the accretion solutions alters due to the change of the model parameters, namely energy (ℰ), angular momentum (λ), ak, and β. Further, we separate the parameter space in λ-ℰ plane according to the nature of the flow solutions, and study the modification of the parameter space by varying ak and β. Moreover, we retrace the parameter space in ak-β plane that allows accretion solutions containing multiple critical points. Finally, we calculate the disc luminosity (L) considering free-free emissions for transonic solutions as these solutions are astrophysically relevant and discuss the implication of this model formalism in the context of astrophysical applications.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"1 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486747","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 : 2024-10-21DOI: 10.1088/1475-7516/2024/10/072
Antonio De Felice, Ryotaro Kase and Shinji Tsujikawa
In a subclass of generalized Proca theories where a cubic vector Galileon term breaks the U(1) gauge invariance, it is known that there are static and spherically symmetric black hole (BH) solutions endowed with nonvanishing temporal and longitudinal vector components. Such hairy BHs are present for a vanishing vector-field mass (m=0) with a non-zero cubic Galileon coupling β3. We study the linear stability of those hairy BHs by considering even-parity perturbations in the eikonal limit. In the angular direction, we show that one of the three dynamical perturbations has a nontrivial squared propagation speed cΩ,12, while the other two dynamical modes are luminal. We could detect two different unstable behaviors of perturbations in all the parameter spaces of hairy asymptotically flat BH solutions we searched for. In the first case, an angular Laplacian instability on the horizon is induced by negative cΩ,12. For the second case, it is possible to avoid this horizon instability, but in such cases, the positivity of cΩ,12 is violated at large distances. Hence these hairy BHs are generally prone to Laplacian instabilities along the angular direction in some regions outside the horizon. Moreover, we also encounter a pathological behavior of the radial propagation speeds cr possessing two different values of cr2 for one of the dynamical perturbations. Introducing the vector-field mass m to cubic vector Galileons, however, we show that the resulting no-hair Schwarzschild BH solution satisfies all the linear stability conditions in the small-scale limit, with luminal propagation speeds of three dynamical even-parity perturbations.
{"title":"Scrutinizing black hole stability in cubic vector Galileon theories","authors":"Antonio De Felice, Ryotaro Kase and Shinji Tsujikawa","doi":"10.1088/1475-7516/2024/10/072","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/10/072","url":null,"abstract":"In a subclass of generalized Proca theories where a cubic vector Galileon term breaks the U(1) gauge invariance, it is known that there are static and spherically symmetric black hole (BH) solutions endowed with nonvanishing temporal and longitudinal vector components. Such hairy BHs are present for a vanishing vector-field mass (m=0) with a non-zero cubic Galileon coupling β3. We study the linear stability of those hairy BHs by considering even-parity perturbations in the eikonal limit. In the angular direction, we show that one of the three dynamical perturbations has a nontrivial squared propagation speed cΩ,12, while the other two dynamical modes are luminal. We could detect two different unstable behaviors of perturbations in all the parameter spaces of hairy asymptotically flat BH solutions we searched for. In the first case, an angular Laplacian instability on the horizon is induced by negative cΩ,12. For the second case, it is possible to avoid this horizon instability, but in such cases, the positivity of cΩ,12 is violated at large distances. Hence these hairy BHs are generally prone to Laplacian instabilities along the angular direction in some regions outside the horizon. Moreover, we also encounter a pathological behavior of the radial propagation speeds cr possessing two different values of cr2 for one of the dynamical perturbations. Introducing the vector-field mass m to cubic vector Galileons, however, we show that the resulting no-hair Schwarzschild BH solution satisfies all the linear stability conditions in the small-scale limit, with luminal propagation speeds of three dynamical even-parity perturbations.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"22 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486658","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 : 2024-10-21DOI: 10.1088/1475-7516/2024/10/073
Andreas Nygaard, Emil Brinch Holm, Steen Hannestad and Thomas Tram
Cosmological emulators of observables such as the Cosmic Microwave Background (CMB) spectra and matter power spectra commonly use training data sampled from a Latin hypercube. This method often incurs high computational costs by covering less relevant parts of the parameter space, especially in high dimensions where only a small fraction of the parameter space yields a significant likelihood. In this paper, we make use of hypersphere sampling, which instead concentrates sample points in regions with higher likelihoods, significantly enhancing the efficiency and accuracy of emulators. A novel algorithm for sampling within a high-dimensional hyperellipsoid aligned with axes of correlation in the cosmological parameters is presented. This method focuses the distribution of training data points on areas of the parameter space that are most relevant to the models being tested, thereby avoiding the computational redundancies common in Latin hypercube approaches. Comparative analysis using the connect emulation tool demonstrates that hypersphere sampling can achieve similar or improved emulation precision with more than an order of magnitude fewer data points and thus less computational effort than traditional methods. This was tested for both the ΛCDM model and a 5-parameter extension including Early Dark Energy, massive neutrinos, and additional ultra-relativistic degrees of freedom. Our results suggest that hypersphere sampling holds potential as a more efficient approach for cosmological emulation, particularly suitable for complex, high-dimensional models.
{"title":"Cutting corners: hypersphere sampling as a new standard for cosmological emulators","authors":"Andreas Nygaard, Emil Brinch Holm, Steen Hannestad and Thomas Tram","doi":"10.1088/1475-7516/2024/10/073","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/10/073","url":null,"abstract":"Cosmological emulators of observables such as the Cosmic Microwave Background (CMB) spectra and matter power spectra commonly use training data sampled from a Latin hypercube. This method often incurs high computational costs by covering less relevant parts of the parameter space, especially in high dimensions where only a small fraction of the parameter space yields a significant likelihood. In this paper, we make use of hypersphere sampling, which instead concentrates sample points in regions with higher likelihoods, significantly enhancing the efficiency and accuracy of emulators. A novel algorithm for sampling within a high-dimensional hyperellipsoid aligned with axes of correlation in the cosmological parameters is presented. This method focuses the distribution of training data points on areas of the parameter space that are most relevant to the models being tested, thereby avoiding the computational redundancies common in Latin hypercube approaches. Comparative analysis using the connect emulation tool demonstrates that hypersphere sampling can achieve similar or improved emulation precision with more than an order of magnitude fewer data points and thus less computational effort than traditional methods. This was tested for both the ΛCDM model and a 5-parameter extension including Early Dark Energy, massive neutrinos, and additional ultra-relativistic degrees of freedom. Our results suggest that hypersphere sampling holds potential as a more efficient approach for cosmological emulation, particularly suitable for complex, high-dimensional models.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"12 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486839","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 : 2024-10-21DOI: 10.1088/1475-7516/2024/10/070
Chao Zhang and Anzhong Wang
In this paper, we study the quasi-normal modes (QNMs) of a scalar field in the background of a large class of quantum black holes that can be formed from gravitational collapse of a dust fluid in the framework of effective loop quantum gravity. The loop quantum black holes (LQBHs) are characterized by three free parameters, one of which is the mass parameter, while the other two are purely due to quantum geometric effects. Among these two quantum parameters, one is completely fixed by black hole thermodynamics and its effects are negligible for macroscopic black holes, while the second parameter is completely free (in principle). In the studies of the QNMs of such LQBHs, we pay particular attention to the difference of the QNMs between LQBHs and classical ones, so that they can be observed for the current and forthcoming gravitational wave observations, whereby place the LQBH theory directly under the test of observations.
{"title":"Quasi-normal modes of loop quantum black holes formed from gravitational collapse","authors":"Chao Zhang and Anzhong Wang","doi":"10.1088/1475-7516/2024/10/070","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/10/070","url":null,"abstract":"In this paper, we study the quasi-normal modes (QNMs) of a scalar field in the background of a large class of quantum black holes that can be formed from gravitational collapse of a dust fluid in the framework of effective loop quantum gravity. The loop quantum black holes (LQBHs) are characterized by three free parameters, one of which is the mass parameter, while the other two are purely due to quantum geometric effects. Among these two quantum parameters, one is completely fixed by black hole thermodynamics and its effects are negligible for macroscopic black holes, while the second parameter is completely free (in principle). In the studies of the QNMs of such LQBHs, we pay particular attention to the difference of the QNMs between LQBHs and classical ones, so that they can be observed for the current and forthcoming gravitational wave observations, whereby place the LQBH theory directly under the test of observations.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"21 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486748","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 : 2024-10-21DOI: 10.1088/1475-7516/2024/10/067
Tong Jiang, Yungui Gong and Xuchen Lu
The accurate sky localization of gravitational wave (GW) sources is an important scientific goal for space-based GW detectors. The main differences between future space-based GW detectors, such as Laser Interferometer Space Antenna (LISA), Taiji, and TianQin, include the time-changing orientation of the detector plane, the arm length, the orbital period of the spacecraft and the noise curve. Because of the effects of gravity on three spacecraft, it is impossible to maintain the equality of the arm length, so the time-delay interferometry (TDI) method is needed to cancel out the laser frequency noise for space-based GW detectors. Extending previous work based on equal-arm Michelson interferometer, we explore the impacts of different first-generation TDI combinations and detector's constellations on the sky localization for monochromatic sources. We find that the sky localization power is almost unaffected by the inclusion of the TDI Michelson (X, Y, Z) combination in the analysis. We also find that the variation in the sky localization power for different TDI combinations is entirely driven by the variation in the sensitivities of these combinations. For the six particular TDI combinations studied, the Michelson (X, Y, Z) combination is the best for source localization.
{"title":"Sky localization of space-based detectors with time-delay interferometry","authors":"Tong Jiang, Yungui Gong and Xuchen Lu","doi":"10.1088/1475-7516/2024/10/067","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/10/067","url":null,"abstract":"The accurate sky localization of gravitational wave (GW) sources is an important scientific goal for space-based GW detectors. The main differences between future space-based GW detectors, such as Laser Interferometer Space Antenna (LISA), Taiji, and TianQin, include the time-changing orientation of the detector plane, the arm length, the orbital period of the spacecraft and the noise curve. Because of the effects of gravity on three spacecraft, it is impossible to maintain the equality of the arm length, so the time-delay interferometry (TDI) method is needed to cancel out the laser frequency noise for space-based GW detectors. Extending previous work based on equal-arm Michelson interferometer, we explore the impacts of different first-generation TDI combinations and detector's constellations on the sky localization for monochromatic sources. We find that the sky localization power is almost unaffected by the inclusion of the TDI Michelson (X, Y, Z) combination in the analysis. We also find that the variation in the sky localization power for different TDI combinations is entirely driven by the variation in the sensitivities of these combinations. For the six particular TDI combinations studied, the Michelson (X, Y, Z) combination is the best for source localization.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"55 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142487005","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 : 2024-10-21DOI: 10.1088/1475-7516/2024/10/069
Alan Junzhe Zhou, Yin Li, Scott Dodelson, Rachel Mandelbaum, Yucheng Zhang, Xiangchong Li and Giulio Fabbian
The analyses of the next generation cosmological surveys demand an accurate, efficient, and differentiable method for simulating the universe and its observables across cosmological volumes. We present Hamiltonian ray tracing (HRT) — the first post-Born (accounting for lens-lens coupling and without relying on the Born approximation), three-dimensional (without assuming the thin-lens approximation), and on-the-fly (applicable to any structure formation simulations) ray tracing algorithm based on the Hamiltonian formalism. HRT performs symplectic integration of the photon geodesics in a weak gravitational field, and can integrate tightly with any gravity solver, enabling co-evolution of matter particles and light rays with minimal additional computations. We implement HRT in the particle-mesh library pmwd, leveraging hardware accelerators such as GPUs and automatic differentiation capabilities based on JAX. When tested on a point-mass lens, HRT achieves sub-percent accuracy in deflection angles above the resolution limit across both weak and moderately strong lensing regimes. We also test HRT in cosmological simulations on the convergence maps and their power spectra.
{"title":"A Hamiltonian, post-Born, three-dimensional, on-the-fly ray tracing algorithm for gravitational lensing","authors":"Alan Junzhe Zhou, Yin Li, Scott Dodelson, Rachel Mandelbaum, Yucheng Zhang, Xiangchong Li and Giulio Fabbian","doi":"10.1088/1475-7516/2024/10/069","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/10/069","url":null,"abstract":"The analyses of the next generation cosmological surveys demand an accurate, efficient, and differentiable method for simulating the universe and its observables across cosmological volumes. We present Hamiltonian ray tracing (HRT) — the first post-Born (accounting for lens-lens coupling and without relying on the Born approximation), three-dimensional (without assuming the thin-lens approximation), and on-the-fly (applicable to any structure formation simulations) ray tracing algorithm based on the Hamiltonian formalism. HRT performs symplectic integration of the photon geodesics in a weak gravitational field, and can integrate tightly with any gravity solver, enabling co-evolution of matter particles and light rays with minimal additional computations. We implement HRT in the particle-mesh library pmwd, leveraging hardware accelerators such as GPUs and automatic differentiation capabilities based on JAX. When tested on a point-mass lens, HRT achieves sub-percent accuracy in deflection angles above the resolution limit across both weak and moderately strong lensing regimes. We also test HRT in cosmological simulations on the convergence maps and their power spectra.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"30 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142487011","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 : 2024-10-17DOI: 10.1088/1475-7516/2024/10/062
Abolhassan Mohammadi
Loop quantum cosmology is a symmetry-reduced application of loop quantum gravity. The theory predicts a bounce for the universe at the Planck scale and resolves the singularity of standard cosmology. The dynamics is also governed by an effective Hamiltonian, which predicts a modified Friedmann equation containing the quadratic terms of the energy density. The term plays an essential role in the high energy regime, but the equations return to the standard form in the low energy regime. The evolution of the universe in the pre-inflationary period is studied in the framework of loop quantum cosmology, where the DBI scalar field is assumed to be the dominant component of the universe. Using the numerical method, we provide the evolution of the DBI field. The background evolution shows that there are three phases as: bouncing phase, transition phase and slow-roll inflationary phase. There is also a short period of super-inflation just at the beginning of the bounce phase. The field first climbs the potential and then reaches the turning point where ϕ̇ disappears and the potential energy becomes the dominant part of the energy density. This is the time when the slow roll inflation begins and the field slowly rolls down the potential. The results indicate that there are a few e-fold expansions in the bounce phase, about N = 3.5–4, and the universe experiences about N = 59 e-fold expansions in the slow-roll inflation phase.
{"title":"Exploring the pre-inflationary dynamics in loop quantum cosmology with a DBI scalar field","authors":"Abolhassan Mohammadi","doi":"10.1088/1475-7516/2024/10/062","DOIUrl":"https://doi.org/10.1088/1475-7516/2024/10/062","url":null,"abstract":"Loop quantum cosmology is a symmetry-reduced application of loop quantum gravity. The theory predicts a bounce for the universe at the Planck scale and resolves the singularity of standard cosmology. The dynamics is also governed by an effective Hamiltonian, which predicts a modified Friedmann equation containing the quadratic terms of the energy density. The term plays an essential role in the high energy regime, but the equations return to the standard form in the low energy regime. The evolution of the universe in the pre-inflationary period is studied in the framework of loop quantum cosmology, where the DBI scalar field is assumed to be the dominant component of the universe. Using the numerical method, we provide the evolution of the DBI field. The background evolution shows that there are three phases as: bouncing phase, transition phase and slow-roll inflationary phase. There is also a short period of super-inflation just at the beginning of the bounce phase. The field first climbs the potential and then reaches the turning point where ϕ̇ disappears and the potential energy becomes the dominant part of the energy density. This is the time when the slow roll inflation begins and the field slowly rolls down the potential. The results indicate that there are a few e-fold expansions in the bounce phase, about N = 3.5–4, and the universe experiences about N = 59 e-fold expansions in the slow-roll inflation phase.","PeriodicalId":15445,"journal":{"name":"Journal of Cosmology and Astroparticle Physics","volume":"66 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142448756","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 : 2024-10-17DOI: 10.1088/1475-7516/2024/10/064
Suman Pal and Gargi Chaudhuri
We have explored the effect of dark matter interaction on hybrid star (HS) in the light of recent astrophysical observational constraints. The presence of dark matter is assumed to be there in both the hadron as well as the quark sector. The dark matter particle interacts with both hadron and quark matter through the exchange of a scalar as well as a vector meson. The equation of state (EOS) of the hadron part is computed using the NL3 version of the relativistic mean field(RMF) model, whereas the quark part is taken care of using the well-known MIT Bag model with the vector interaction. We investigate the effect of the dark matter density and the mass of the dark matter particle on various observables like mass, radius, tidal deformability of the dark matter admixed hybrid star(DMAHS). In this study, we have noted an intriguing aspect that is the speed of sound in the DMAHS is insensitive to both the mass as well as the density of dark matter. We also observe a striking similarity in the variation of transition mass and its corresponding radius, as well as the maximum mass of neutron stars, with dark matter density and mass. We employ observational constraints from neutron stars to narrow down the allowed range of the parameters of dark matter.
我们根据最近的天体物理观测约束条件，探讨了暗物质相互作用对混合星（HS）的影响。我们假定在强子和夸克扇区都存在暗物质。暗物质粒子通过交换标量和矢量介子与强子和夸克物质相互作用。强子部分的状态方程（EOS）是用相对论平均场（RMF）模型的 NL3 版本计算的，而夸克部分则是用著名的 MIT Bag 向量相互作用模型计算的。我们研究了暗物质密度和暗物质粒子质量对暗物质混合混合星（DMAHS）的质量、半径、潮汐变形性等各种观测指标的影响。在这项研究中，我们注意到一个耐人寻味的方面，即 DMAHS 的声速对暗物质的质量和密度都不敏感。我们还观察到过渡质量及其相应半径的变化，以及中子星的最大质量与暗物质密度和质量的变化有着惊人的相似性。我们利用中子星的观测约束来缩小暗物质参数的允许范围。
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