分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Dark photon dark matter that has a kinetic mixing with the Standard Model photon can resonantly convert in environments where its mass $m_{A'}$ coincides with the plasma frequency. We show that such conversion in neutron stars or accreting white dwarfs in the galactic centre can lead to detectable radio signals. Depending on the dark matter spatial distribution, future radio telescopes could be sensitive to values of the kinetic mixing parameter that exceed current constraints by orders of magnitude for $m_{A'} \in \left(6\times 10^{-6},7\times 10^{-4}\right)$ eV.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Theories of large extra dimensions (LEDs) such as the Arkani-Hamed, Dimopoulos & Dvali scenario predict a "true" Planck scale $M_\star$ near the TeV scale, while the observed $M_{pl}$ is due to the geometric effect of compact extra dimensions. These theories allow for the creation of primordial black holes (PBHs) in the early Universe, from the collisional formation and subsequent accretion of black holes in the high-temperature plasma, leading to a novel cold dark matter (sub)component. Because of their existence in a higher-dimensional space, the usual relationship between mass, radius and temperature is modified, leading to distinct behaviour with respect to their 4-dimensional counterparts. Here, we derive the cosmological creation and evolution of such PBH candidates, including the greybody factors describing their evaporation, and obtain limits on LED PBHs from direct observation of evaporation products, effects on big bang nucleosynthesis, and the cosmic microwave background angular power spectrum. Our limits cover scenarios of 2 to 6 extra dimensions, and PBH masses ranging from 10 to $10^{21}$ g. We find that for two extra dimensions, LED PBHs represent a viable dark matter candidate with a range of possible black hole masses between $10^{17}$ and $10^{23}$ g depending on the Planck scale and reheating temperature. For $M_\star = 10$ TeV, this corresponds to PBH dark matter with a mass of $M \simeq 10^{21}$ g, unconstrained by current observations. We further refine and update constraints on "ordinary" four-dimension black holes.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The direct capture and accumulation of Galactic dark matter in astrophysical bodies can occur as a result of its scattering with nuclei. In this work we investigate the detailed capture and evaporation of dark matter in terrestrial planets, taking Earth as an example. We focus on the strongly interacting case in which Earth may be opaque to dark matter, referred to as the "optically thick" limit. We investigate light dark matter in particular, addressing important dynamical processes such as the "ping-pong effect" during dark matter capture and the heating of Earth by dark matter annihilation. We do this using Monte-Carlo simulations as well as detailed analytical computations, and obtain improved bounds on dark matter direct detection for both spin-dependent and spin-independent scattering, and also allowing for the interacting species to make up a sub-component of the dark matter density.
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