We provide a general framework for self-interacting warm dark matter (WDM) in cosmological perturbations, by deriving from first principles a Boltzmann hierarchy which retains certain independence from a particular interaction Lagrangian. We consider elastic interactions among the massive particles, and obtain a hierarchy which is more general than the ones usually obtained for non-relativistic (as for cold DM) or for ultra-relativistic (as for neutrinos) approximations. The more general momentum-dependent kernel integrals in the Boltzmann collision terms, are explicitly calculated for different field-mediator models, including examples of a scalar field (either massive or massless) or a massive vector field. As an application, we study the evolution of the interaction rate per particle under the relaxation time approximation, and assess when a given self-interaction is relevant in comparison with the Hubble expansion rate. Our framework aims to be a useful starting point to evaluate DM self-interaction effects in the linear power spectrum, necessary to then study its evolution all the way to non-linear stages of structure formation, where certain DM interactions were proven to be relevant.
Within cosmological perturbation theory, the cosmic microwave background anisotropies are usually computed from a Boltzmann hierarchy coupled to the perturbed Einstein equations. In this setup, one set of multipoles describes the temperature anisotropies, while two other sets, of electric and magnetic types, describe the polarization anisotropies. In order to reduce the number of multipoles types needed for polarization, and thus to speed up the numerical resolution, an optimal hierarchy has been proposed in the literature for Einstein-Boltzmann codes. However, it has been recently shown that …
We show that, in warm inflation, the nearly constant Hubble rate and temperature lead to an adiabatic evolution of the number density of particles interacting with the thermal bath, even if thermal equilibrium cannot be maintained. In this case, the number density is suppressed compared to the equilibrium value but the associated phase-space distribution retains approximately an equilibrium form, with a smaller amplitude and a slightly smaller effective temperature. As an application, we explicitly construct a baryogenesis mechanism during warm inflation based on the out-of-equilibrium decay o…
We present a formulation of cosmological perturbation theory where the Boltzmann hierarchies that evolve the neutrino phase-space distributions are replaced by integrals that can be evaluated easily with fast Fourier transforms. The simultaneous evaluation of these integrals combined with the differential equations for the rest of the system (dark matter, photons, baryons) are then solved with an iterative scheme that converges quickly. The formulation is particularly powerful for massive neutrinos, where the effective phase space is three-dimensional rather than two-dimensional, and even more…
We study quasi-single field inflation with a warm inflation background. The thermal effects at small scales can sufficiently enhance the magnitude of the primordial standard clock signal. This scenario offers us the possibility of probing the UV physics of the very early universe without the exponentially small Boltzmann factor when the mass of the isocurvaton is much heavier than Hubble. The thermal effects at small scales can be studied using the flat space thermal field theory, connected to an effective description using non-Bunch-Davies vacuum at large scales, with large clock signal.
Warm fermionic dark matter from freeze-in at stronger coupling
Departamento de Física da Universidade de Aveiro（阿威罗大学物理系）；Laboratório de Instrumentação e Física Experimental de Partículas (LIP), Universidade do Minho（米尼奥大学粒子物理实验仪器实验室）
We study the evolution of cosmological perturbations in dark-matter models with elastic and velocity-independent self interactions. Such interactions are imprinted in the matter-power spectrum as dark acoustic oscillations, which can be experimentally explored to determine the strength of the self scatterings. Models with self interactions have similarities to warm dark matter, as they lead to suppression of power on small scales when the dark-matter velocity dispersion is sizable. Nonetheless, both the physical origin and the extent of the suppression differ for self-interacting dark matter f…
In this work we present a summary of recent studies on the effects of elastic self interactions in the evolution of Warm Dark Matter models (WDM), focusing on structure formation and the evolution of cosmological perturbations. We pay special attention to a particular class of sterile neutrino WDM known as $ν$MSM and provide examples for the case of vector field self interactions. We calculate the effects of assuming self interacting dark matter in X-Ray astrophysical observations, in the formation of fermionic DM halos in (quasi) equilibrium states and in the evolution of DM perturbations in …
Using the Reduced Relativistic Gas (RRG) model, we analytically determine the matter power spectrum for Warm Dark Matter (WDM) on small scales, $k>1\ h\text{/Mpc}$. The RRG is a simplified model for the ideal relativistic gas, but very accurate in the cosmological context. In another work, we have shown that, for typical allowed masses for dark matter particles, $m>5\ \text{keV}$, the higher order multipoles, $\ell>2$, in the Einstein-Boltzmann system of equations are negligible on scales $k<10\ h\text{/Mpc}$. Hence, we can follow the perturbations of WDM using the ideal fluid framework, with …
Dark matter coupled solely gravitationally can be produced through the decay of primordial black holes in the early universe. If the dark matter is lighter than the initial black hole temperature, it could be warm enough to be subject to structure formation constraints. In this paper we perform a more precise determination of these constraints. We first evaluate the dark matter phase-space distribution, without relying on the instantaneous decay approximation. We then interface this phase-space distribution with the Boltzmann code CLASS to extract the corresponding matter power spectrum, which…
The small scale structure opens a window to constrain the dynamical properties of Dark Matter. Here we study the clustering of warm dark matter (WDM) in a semi-analytical approach and compared the linear power spectrum of WDM with cold dark matter (CDM) employing a new transfer function $T_v(a,k)$ in terms of the viral wave number $k_v=2π/λ_v$ corresponding to a structure with a viral radius $r_v=λ_v/2$, half the size of the free streaming scale radius $r_v=r_{fs}/2=λ_{fs}/4$. The virial mass $M_v$ contained in this structure corresponds to the lightest structure formed for a WDM particle beco…
Towards the Chalonge Meudon Workshop 2013. Highlights and Conclusions of the Chalonge Meudon workshop 2012: warm dark matter galaxy formation in agreement with observations
暖暗物质（WDM），大大澄清和简化了星系和星系形成与观察一致。WDM基本上是工作的，自然地再现了所有尺度上的天文观测，小CDM，CDM+重子和建议的定制治疗在星系中不起作用的证据是惊人的，Chalonge Meudon Workshop 2012以四重一致的方式接近DM：天文观测（星系和星系团性质，晕，旋转曲线，密度分布，表面密度），LambdaWDM N体模拟，WDM理论（玻尔兹曼-弗拉索夫演化，晕质量函数，晕模型，改进的微扰方法），量子WDM费米子形成观察到的核心，WDM粒子和核物理（无菌中微子）及其实验研究。N Amorisco，P Biermann，S Das，H J de Vega，A Kamada，E Ferri（MARE），I D Karanchetsev，W Liao，M Lovell，M Papastergis，N G Sanchez，P Valageas，C Watson，J Zavala，He Zhang介绍了他们的研究成果。在星系核内部，N体经典物理模拟不适用于WDM，因为在这样的尺度下，存在重要的量子效应。量子WDM计算（D-Fermi）计算结果提供了与观测一致的星系核、星系质量、速度色散和密度分布，重子（占DM的16%）对纯WDM结果进行了修正。H. de Vega和N. G.桑切斯强调，所有的证据都表明DM粒子的质量在2 keV左右。彼得·比尔曼在他的…
This paper presents a systematic and accurate treatment of the evolution of cosmological perturbations in self-interacting dark matter models, for particles which decoupled from the primordial plasma while relativistic. We provide a numerical implementation of the Boltzmann hierarchies developed in a previous paper [JCAP, 09 (2020) 041] in a publicly available Boltzmann code and show how it can be applied to realistic DM candidates such as sterile neutrinos either under resonant or non-resonant production mechanisms, and for different field mediators. At difference with traditional fluid appro…
Many models of dark matter have been proposed in attempt to ease the $S_8$ tension between weak lensing and CMB experiments. One such exciting possibility is cannibalistic dark matter (CanDM), which has exothermal number-changing interactions allowing it to stay warm far into its non-relativistic regime. Here we investigate the cosmological implications of CanDM and how it impacts CMB anisotropies and the matter power spectrum, by implementing the model within a linear Einstein-Boltzmann solver. We show that CanDM suppresses the small scale matter power spectrum in a way very similar to light …
Consistent treatment of flavour-specific neutrino self-interactions in cosmology
Instituto de Física Corpuscular, CSIC-Universitat de València（粒子物理研究所，西班牙瓦伦西亚大学）；Departament de Física Tèorica, Universitat de València（理论物理系，西班牙瓦伦西亚大学）；UCLouvain, Centre for Cosmology, Particle Physics and Phenomenology (CP3)（天主教鲁汶大学，宇宙学、粒子物理与现象学中心）；Technische Universität München（慕尼黑工业大学）；Bielefeld University（比勒费尔德大学）
Mesoamerican Centre for Theoretical Physics, Universidad Autónoma de Chiapas（中美洲理论物理中心，恰帕斯自治大学）；Consejo Nacional de Ciencia y Tecnología（国家科学技术委员会）；Instituto de Física, Universidad Nacional Autonoma de México（墨西哥国立自治大学物理研究所）；Instituto de Ciencias del Cosmos, University of Barcelona（巴塞罗那大学宇宙科学研究所）
We study the imprints of secluded dark sectors with a mass gap and self-interactions on the matter power spectrum. When Dark Matter (DM) is sufficiently light, in the ballpark of a few KeV, and self-interacting we find qualitative difference with respect to $Λ$CDM and also to free streaming DM. In order to emphasize the role of interactions for the evolution of the primordial perturbations we discuss various regimes: ranging from the ideal case of a tightly coupled perfect fluid to the free case of Warm Dark Matter, including the realistic case of small but non-vanishing self-interactions. We …
Towards a complete scheme of cosmological neutrino self-interactions: Collision term for a wide range of mediator masses
Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional（墨西哥国立理工学院高级研究中心）；Secretaría de Ciencia, Humanidades, Tecnología e Innovación（科学、人文、技术与创新秘书处）；Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México（墨西哥国立自治大学物理科学研究所）；Tecnológico de Monterrey, Escuela de Ingeniería y Ciencias（蒙特雷理工学院工程与科学学院）
Cosmic Structure Strikes Back: The Elimination of Vector-Mediated Nonstandard Interaction Models as a Mechanism for Sterile Neutrino Dark Matter Production
The system of stability equations for galactic halos is under-determined in most of the models of dark matter (DM). Conventionally, the issue is resolved by taking the temperature as a constant, and the chemical potential and the mass density as position-dependent variables. In this paper, to close the under-determined set of equations, we remove the mass density using observations and leave the temperature and the chemical potential as position-dependent variables. We analyze observations of the mass profiles of 175 late-type galaxies in the Spitzer Photometry \& Accurate Rotation Curves (SPA…
