Liao Liu
We introduce first a new road to quantize the Schwarzschild black hole. Then we find that the ground state or relic of the quantum evaporating black hole can be identified as dark matter.
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Vilkovisky has claimed to have solved the black hole backreaction problem and finds that black holes lose only ten percent of their mass to Hawking radiation before evaporation ceases. We examine the implications of this scenario for cold dark matter, assuming that primordial black holes are created during the reheating period after inflation. The mass spectrum is expected to be dominated by 10-gram black holes. Nucleosynthesis constraints and the requirement that the earth presently exist do not come close to ruling out such black holes as dark matter candidates. They also evade the demand th…
The mechanism of the generation of dark matter and dark radiation from the evaporation of primordial black holes is very interesting. We consider the case of Kerr black holes to generalize previous results obtained in the Schwarzschild case. For dark matter, the results do not change dramatically and the bounds on warm dark matter apply similarly: in particular, the Kerr case cannot save the scenario of black hole domination for light dark matter. For dark radiation, the expectations for $ΔN_{eff}$ do not change significantly with respect to the Schwarzschild case, but for an enhancement in th…
Kiselev black hole and the ultra-slow evaporating behavior
研究Kiselev黑洞的蒸发行为，发现状态参数w_q降低会延长蒸发寿命，其超慢蒸发机制不同于PFDM和Horndeski黑洞。
If light enough primordial black holes (PBH) account for dark matter, then its density decreases with time as they lose mass via Hawking radiation. We show that this time-dependence of the matter density can be formulated as an equivalent $w(z)$ dark energy model and we study its implications on the expansion history. Using our approach and comparing with the latest cosmological data, including the supernovae type Ia, Baryon Acoustic Oscillations, Cosmic Microwave Background and the Hubble expansion H(z) data, we place observational constraints on the PBH model. We find that it is statisticall…
Primordial black holes (PBHs) from the early Universe have been connected with the nature of dark matter and can significantly affect cosmological history. We show that coincidence dark radiation and density fluctuation gravitational wave signatures associated with evaporation of $\lesssim10^9$ g PBHs can be used to explore and obtain important hints about the formation mechanisms of spinning and non-spinning PBHs spanning orders of magnitude in mass-range, which is challenging to do otherwise.
Primordial black holes (PBHs) in the mass range $10^{17} - 10^{23}~{\rm gm}$ are considered as possible dark matter candidates as they are not subject to big-bang nucleosynthesis constraints and behave like cold dark matter. If PBHs are indeed dark matter, they cannot be treated as isolated objects in asymptotic flat space-time. Furthermore, when compared to stellar-mass black holes, the rate at which the Hawking particles radiate out from PBHs is significantly faster. In this work, we obtain an exact time-dependent solution that models evaporating black holes in the cosmological background. A…
We show that primordial black holes (PBHs) develop non-negligible spins through Hawking emission of the large number of axion-like particles generically present in string theory compactifications. This is because scalars can be emitted in the monopole mode ($l=0$), where no angular momentum is removed from the BH, so a sufficiently large number of scalars can compensate for the spin-down produced by fermion, gauge boson, and graviton emission. The resulting characteristic spin distributions for $10^8$-$10^{12}$ kg PBHs could potentially be measured by future gamma-ray observatories, provided t…
From scalar clouds around evaporating black holes to boson star
研究发现，当黑洞绝热蒸发至质量小于云质量一半时，标量云可能形成自引力的玻色子星，揭示了玻色子星形成的新机制及暗物质探测潜力的增强
Cosmological Bounce Relics: Black Holes, Gravitational Waves, and Dark Matter
本研究提出在反弹宇宙中通过非线性结构形成产生黑洞、引力波和暗物质残余，揭示了其统一的起源机制。
We demonstrate the existence of a generic, efficient and purely gravitational channel producing a significant abundance of dark relics during reheating after the end of inflation. The mechanism is present for any inert scalar with the non-minimal curvature coupling $ξRχ^2$ and the relic production is efficient for natural values $ξ= {\cal O}(1)$. The observed dark matter abundance can be reached for a broad range of relic masses extending from $m \sim 1 {\rm k eV}$ to $m \sim 10^{8} {\rm GeV}$, depending on the scale of inflation and the dark sector couplings. Frustratingly, such relics escape…
Gaussian Planck Relics are Ruled-Out as Dark Matter by LIGO
LIGO引力波背景上限排除了由高斯初始条件形成的普朗克质量残余作为暗物质的可能性，表明非高斯原始涨落是唯一可行的通道。
The interplay of dilatonic effects in dilaton cosmology and stochastic quantum space-time defects within the framework of string/brane cosmologies is examined. The Boltzmann equation describes the physics of thermal dark-matter-relic abundances in the presence of rolling dilatons. These dilatons affect the coupling of stringy matter to D-particle defects, which are generic in string theory. This coupling leads to an additional source term in the Boltzmann equation. The techniques of asymptotic matching and boundary-layer theory, which were recently applied by two of the authors (CMB and SS) to…
The idea that dark matter could be made of stable relics of microscopic black holes is not new. In this article, we revisit this hypothesis, focusing on the creation of black holes by the scattering of trans-Planckian particles in the early Universe. The only new physics required in this approach is an unusually high-energy scale for inflation. We show that dark matter emerges naturally and we study the question of fine-tuning. We finally give some lines of thoughts for a possible detection.
Hawking radiation of astrophysical black holes is minute and thought to be unobservable. However, different mechanisms could contribute to an anomalously high emission rate: extra dimensions, new "dark" families of bosons or fermions, or a lower fundamental Planck scale. Do black holes flood the Universe with gravitational waves via mass loss? Here, we show that the formation of black hole binaries and the absence of a stochastic background of gravitational waves can limit the emission rate to $|\dot{M}|\lesssim 10^{-15}M_{\odot}/{\rm yr}$, seven orders of magnitude more stringent than bounds …
We discuss modifications of the thermal Dark Matter (DM) relic abundances in stringy cosmologies with D-particle space-time foamy backgrounds. As a result of back-reaction of massive DM on the background space-time, owing to its interaction with D-particle defects in the foam, quantum fluctuations are induced in the space-time metric. We demonstrate that these lead to the presence of extra source terms in the Boltzmann equation used to determine the thermal dark matter relic abundances. The source terms are determined by the specific form of the induced metric deformations; the latter depend o…
We investigate the thermal relics as hot, warm and cold dark matter in $\mathscr{L}=\varepsilon^{2-2β}R^β+{16π}m_{\text{Pl}}^{-2}\mathscr{L}_m$ gravity, where $\varepsilon$ is a constant balancing the dimension of the field equation, and $1<β<(4+\sqrt{6})/5$ for the positivity of energy density and temperature. If light neutrinos serve as hot/warm relics, the entropic number of statistical degrees of freedom $g_{*s}$ at freeze-out and thus the predicted fractional energy density $Ω_ψh^2$ are $β-$dependent, which relaxes the standard mass bound $Σm_ν$. For cold relics, by exactly solve the simp…
We study the impact of a modified expansion rate on the dark matter relic abundance in a class of scalar-tensor theories. The scalar-tensor theories we consider are motivated from string theory constructions, which have conformal as well as disformally coupled matter to the scalar. We investigate the effects of such a conformal coupling to the dark matter relic abundance for a wide range of initial conditions, masses and cross-sections. We find that exploiting all possible initial conditions, the annihilation cross-section required to satisfy the dark matter content can differ from the thermal…
Stochastic gravitational-wave background at 3G detectors as a smoking gun for microscopic dark matter relics
本研究系统探究早期宇宙中形成的微观暗物质遗迹对应的随机引力波背景，发现现有干涉仪仅能勉强探测该信号，而第三代探测器如Einstein Telescope可探测到，强化了其作为发现机器的潜力。
Tachyonic production of dark relics: classical lattice vs. quantum 2PI in Hartree truncation
本研究通过经典格点模拟探究再加热阶段自相互作用标量暗物质的非平衡产生，验证了其与哈特里截断量子2PI方法的定性一致性，确认新型非线性共振的存在及产额主导作用，且二者两点函数终值差异为O(1)量级。
Tachyonic production of dark relics: a non-perturbative quantum study
该研究针对暴胀后再加热期的暗遗迹产生问题，推导并数值求解非最小耦合旁观标量场的重整化量子输运方程，发现快子与参量两种不稳定性，其中两点函数驱动的参量不稳定性主导粒子产生且结果对模型参数高度敏感。
Thermal freeze-out is a prominent example of dark matter (DM) production mechanism in the early Universe that can yield the correct relic density of stable weakly interacting massive particles (WIMPs). At the other end of the mass scale, many popular extensions of the Standard Model predict the existence of ultra-light scalar fields. These can be coupled to matter, preferentially in a universal and shift-symmetry-preserving way. We study the impact of such conformal and disformal couplings on the relic density of WIMPs, without introducing modifications to the thermal history of the Universe. …
Warm Hawking Relics From Primordial Black Hole Domination
本研究探讨原始黑洞霍金辐射产生的暖暗物质遗迹对宇宙结构增长的影响，发现其动量分布更宽、丰度受限，并展望未来观测可区分霍金遗迹与热遗迹。
Dark Matter from Higher Dimensional Primordial Black Holes
本文研究大额外维度中微观原初黑洞产生暗物质的三种途径，发现瞬时蒸发黑洞可在宽量子引力尺度和额外维度数量下解释观测丰度并保持足够冷。
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