A small admixture of dark matter gravitationally bound to the proto-Solar gas cloud could be adiabatically contracted into Earth-crossing orbits with a local density comparable to (or even exceeding) the Galactic halo density. We show that a significant fraction (~25%) of the resulting 'Solar halo' would remain today, surviving perturbations from Jupiter and close encounters with Earth, and would be potentially observable in direct detection experiments. The population would have distinct signatures, including a nonstandard annual modulation and extremely low velocity dispersion compared with the Galactic halo, making it an especially interesting target for coherent or resonant detection of ultralight particles such as axions or dark photons.
We investigate photon signatures of general decaying dark-matter particles in halos of primordial black holes. We derive the halo-profile density and the total decay rate for these combined dark-matter scenarios. For the case of axion-like particles of masses below $\mathcal{O}( 1 )\,$keV, we find strong bounds on the decay constant which are several orders of magnitude stronger than the strongest existing bounds, for all halo masses above $\mathcal{O}( 10^{-5} )$ solar masses. Using future X-ray measurements, it will be possible to push these bounds on such combined dark-matter scenarios even…
A lower bound on primordial power spectrum from halo substructure
University of Amsterdam（阿姆斯特丹大学）；Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo（东京大学宇宙起源研究科）；Yokohama National University（横滨国立大学）；RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS)（理化学研究所交叉理论数学科学部）；Institute for Theoretical Physics, Kanazawa University（金泽大学理论物理研究所）；Saga University（佐贺大学）
Even if massive ($10\,M_\odot \lesssim M \lesssim 10^4 M_\odot$) primordial black holes (PBHs) can only account for a small fraction of the dark matter (DM) in the universe, they may still be responsible for a sizable fraction of the coalescence events measured by LIGO/Virgo, and/or act as progenitors of the supermassive black holes (SMBHs) observed already at high redshift ($z\gtrsim 6$). In presence of a dominant, non-PBH DM component, the bounds set by CMB via an altered ionization history are modified. We revisit the cosmological accretion of a DM halo around PBHs via toy models and dedica…
The first-order electroweak phase transition in the early universe could occur in multiple steps leading to specific multi-peaked signatures in the primordial gravitational wave (GW) spectrum. We argue that these signatures are generic phenomena in multi-scalar extensions of the Standard Model. In a simple example of such an extension, we have studied the emergence of reoccurring and nested vacuum bubble configurations and their role in the formation of multiple peaks in the GW spectrum. The conditions for potential detectability of these features by the forthcoming generation of interferomete…
Primordial black holes (PBHs) are a potential dark matter candidate whose masses can span over many orders of magnitude. If they have masses in the $10^{15}-10^{17}$ g range, they can emit sizeable fluxes of MeV neutrinos through evaporation via Hawking radiation. We explore the possibility of detecting light (non-)rotating PBHs with future neutrino experiments. We focus on two next generation facilities: the Deep Underground Neutrino Experiment (DUNE) and THEIA. We simulate the expected event spectra at both experiments assuming different PBH mass distributions and spins, and we extract the e…
We discuss formation of dark matter (DM) mini-halos around primordial black holes (PBHs) and its implication on DM direct detection experiments, including axion searches. Motivated by LIGO observations, we consider $f_{\textrm{DM}} \simeq 0.01$ as the fraction of DM in PBHs with masses $10 M_{\odot} - 70 M_{\odot}$. In this case, we expect the presence of dressed PBHs after Milky Way halo formation with mini-halo masses peaked around $M_{\textrm{halo}} \sim (50-55) M_{\textrm{PBH}}$. We analyze the effect of tidal forces acting on dressed PBHs within the Milky Way galaxy. In the solar neighbor…
The primordial Lithium Problem is intimately connected to the assumption that ${}^{7}{\rm Li}$ observed in metal-poor halo stars retains its primordial abundance, which lies significantly below the predictions of standard big-bang nucleosynthesis. Two key lines of evidence have argued that these stars have not significantly depleted their initial ${}^{7}{\rm Li}$: i) the lack of dispersion in Li abundances measured at low metallicity; and ii) the detection of the more fragile ${}^{6}{\rm Li}$ isotope in at least two halo stars. The purported ${}^{6}{\rm Li}$ detections were in good agreement w…
We describe a new scenario for the formation of primordial black holes (PBHs). In the early Universe, the long-range forces mediated by the scalar fields can lead to formation of halos of heavy particles even during the radiation-dominated era. The same interactions result in the emission of scalar radiation from the motion and close encounters of particles in such halos. Radiative cooling due the scalar radiation allows the halos to collapse to black holes. We illustrate this scenario on a simple model with fermions interacting via the Yukawa forces. The abundance and the mass function of PBH…
Primordial Physics in the Nonlinear Universe: signatures of inflationary resonances, excitations, and scale dependence
University of Chicago（芝加哥大学）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙物理学研究所）；NSF-Simons AI Institute for the Sky (SkAI)（NSF-西蒙斯天空人工智能研究所（SkAI））；University of Pennsylvania（宾夕法尼亚大学）；Center for Particle Cosmology, Department of Physics and Astronomy, University of Pennsylvania（宾夕法尼亚大学物理与天文学系粒子宇宙学中心）
