Black Hole Evaporation Research Articles

The principle and state-of-art applications of Hawking radiation

Hawking radiation, firstly discovered in 1974 by Stephen Hawking, is a crucial quantum phenomenon, which proves that a black hole has been losing its mass since its formation. In this paper, the method of information retrieval and literature analysis are fully applied to introduce the principle and state-of-art applications of Hawking radiation. Three parameters used to describe the evaporation of black holes are analyzed. Furthermore, the tunnelling effect of entangled pairs near event horizon is described to explain Hawking radiation from a microscopic perspective. Then, the evaporating black holes are observed under wave optical conditions by the Fourier transformation of the spatial correlation function and detected in Laboratory condition by equivalenting entangled pairs to surface wave packets with sum-zero energy. Finally, a prediction is made that the widely used of extra-dimensional theory and high-energy particle technology as well as numerical researches in laboratory conditions will be strongly pushing the observation of Hawking radiation. Overall, these results shed light on further exploring the universe in terms of Hawking radiation.

Page curve and symmetries

Motivated by the quantum process of black hole evaporation and its implications for symmetries, we consider a qubit system with a random dynamics as a toy model of black hole. We compute its symmetry-resolved entropies and discuss its implications. We first consider the case where charges are conserved and compute the symmetry-resolved entropies. We derive a symmetry-resolved analogue of the Page curve. We then consider the case where symmetry is explicitly broken and charges are no longer conserved. It serves as a toy model for global symmetry breaking in black hole evaporation. Despite the simple framework, the symmetry-resolved entropies capture various interesting features during the analogous process of black hole evaporation in our qubit model.

Constraining PBH mass distributions from 21cm brightness temperature results and an analytical mapping between probability distribution of 21cm signal and PBH masses

The evaporation of primordial black hole (PBH) via Hawking radiation influences the evolution of Inter Galactic Medium by heating up the latter and consequently affects the 21cm signal originated from the neutral Hydrogen atoms. In this work, we have considered EDGES observational data of 21cm line corresponding to cosmic dawn era to constrain the mass and the abundance of PBHs. In this context, two different PBH mass distributions namely, power law and lognormal mass distributions are considered to estimate the effects of PBH evaporation on the 21cm brightness temperature T 21. In addition to these two mass distributions, different monochromatic masses are also considered. The impacts of dark matter-baryon interactions on T 21 are also considered in this work along with the influences of PBH evaporation. Furthermore, adopting different monochromatic masses for PBHs, an attempt has been made to formulate a distribution for PBH masses by associating a probability weightage of the T 21 values (at z ∼ 17.2), within the range given by EDGES experiment, with the calculated T 21 values for each of the PBH mass values. The distribution best suited for the present purpose is found to be a combination of an error function and Owen function. Allowed contours in the parameter space of (initial PBH mass-dark matter mass) are obtained.

Electron-target experiment constraints on light dark matter produced in primordial black hole evaporation

Light sub-GeV dark matter (DM) particles in the Milky Way or macroscopic objects such as primordial black holes (PBHs) become attractive DM candidates due to null results of WIMP from direct detection experiments. We explore the possibility in which the present PBHs play as a novel source to produce light boosted DM and confine light PBHs with current and future terrestrial facilities. We study the electron elastic scattering data and obtain the current constraints from Super-Kamiokande and XENON1T on the boosted DM from PBH evaporation. The prospective bounds on the sub-GeV DM-electron scattering cross section and the fraction of DM composed of PBHs $f_{\rm PBH}$ are also imposed for future Xenon experiments.

Evaporating black holes and late-stage loss of soft hair

We present a paradox for evaporating black holes, which is common in most schemes trying to avoid the firewall by decoupling early and late radiation. At the late stage of the black hole evaporation, the decoupling between early and late radiation can not be realized because the black hole has a very small coarse-grained entropy, then we are faced with the firewall again. We call the problem hair-loss paradox as a pun on losing black hole soft hair during the black hole evaporation and the situation that the information paradox has put so much pressure on researchers.

Accretions of (m, n)-type Pilgrim dark energies with logarithmic and power-law entropy corrections onto (D + 2)-dimensional black hole and wormhole

This work aims to study the accretions of dark energy coupled with dark matter onto a static Schwarzschild black hole of [Formula: see text] dimensions. Besides the accretion of fluids, the effect due to evaporation of black hole of [Formula: see text] dimensions is under consideration. Mass is one of the interesting dynamical properties of a black hole. The changes in masses have been projected in the framework of the Friedmann–Robertson–Walker model of the universe of [Formula: see text] dimensions. The [Formula: see text]-type Pilgrim dark energies with their logarithmic and power-law entropy corrections are considered as the form of dark energy in our study. Further, the scale factor that is considered as [Formula: see text], [Formula: see text] follows the power-law form. The changes in the dynamical mass of the black hole have been calculated with the variation corresponding to redshift [Formula: see text] while dark matter and specified type of dark energy accrete onto [Formula: see text]-dimensional Schwarzschild black hole. It is found that the dynamical mass of the black hole increases in the late-time epoch as a consequence of the prescribed form of dark energy accretion and evaporation of the black hole. Finally, we discuss the accretion phenomena of the above-specified types of dark energies onto [Formula: see text]-dimensional Morris–Thorne wormhole. It has been investigated that the masses of the black hole and the wormhole sensitively vary with the values of the dimensions.

Resolving information loss paradox with Euclidean path integral

The information loss paradox remains unresolved ever since Hawking’s seminal discovery of black hole evaporation. In this paper, we revisit the entanglement entropy via Euclidean path integral (EPI) and allow for the branching of semi-classical histories during the Lorentzian evolution. We posit that there exist two histories that contribute to EPI, where one is information-losing that dominates at early times, while the other is information-preserving that dominates at late times. By so doing, we recover the Page curve and preserve the unitarity, albeit with the Page time shifted significantly towards the late time. One implication is that the entropy bound may thus be violated. We compare our approach with string-based islands and replica wormholes concepts.

The Entangled Informational Universe

From the perspective of quantum gravity research, since the archetypal quantum gravitational object, the black hole, was accidentally found function as a thermodynamic system, it is certainly natural to suggest that the secret of quantum gravity may lie in thermodynamic analysis. Until now, it was not possible to express the gravitational fine-grained entropy of a black hole using the rules of gravity. However, the black holes entropic information formula fills this gap by allowing a semi-classical gravitational approach to express the gravitational fine-grained entropy of black hole. The black holes entropic information formula calculates the entropy of Hawking radiation as the entangled information of the initial considered black hole, this down to the quantum level of the system, the degrees of freedom describing the black hole, and this independently of the Bekenstein-Hawking entropy area law, providing a sufficient microscopic description of how this entropy arises, showing that the process of black holes evaporation is consistent with the unitarity principle. Also, this approach avoids ultraviolet divergences. These perspectives must be understood like the fine-grained entropy formulas discovered by Ryu and Takayanagi. In fact, the black hole entropy turns out to be a special case of the Ryu-Takayanagi conjecture. The Ryu-Takayanagi formula being a general formula for the fine-grained entropy of gravity-coupled quantum systems. That put the accent on the emergence quantum gravity process through the fundamentality of the entangled quantum information.

Correlated signals of first-order phase transitions and primordial black hole evaporation

Fermi balls produced in a cosmological first-order phase transition may collapse to primordial black holes (PBHs) if the fermion dark matter particles that comprise them interact via a sufficiently strong Yukawa force. We show that phase transitions described by a quartic thermal effective potential with vacuum energy, 0.1 ≲ B1/4/MeV ≲ 103, generate PBHs of mass, 10−20 ≲ MPBH/M⊙ ≲ 10−16, and gravitational waves from the phase transition (at THEIA/μAres) can be correlated with an isotropic extragalactic X-ray/γ-ray background from PBH evaporation (at AMEGO-X/e-ASTROGAM).

Hawking evaporation, shadow images, and thermodynamics of black holes through deflection angle

We study the Hawking evaporation process of the exact black hole with nonlinear electrodynamics for positive and negative coupling constant zeta . We provide a new perspective to study the thermodynamics of exact black hole through deflection angle formalism. We also evaluate the shadow images in the presence of deflection images for this black hole. Moreover, we consider the Gibbs energy optical dependence to investigate the Hawking-Page transition. We observe that evaporation rate depends upon zeta and black hole evaporates more quickly for positive zeta as compared to negative zeta . For the case zeta =-1, the black hole’s lifetime become infinite, which makes the black hole a remnant and the third law of black hole thermodynamics holds in this scenario. We show that the thermal variations in the deflection angle can be used to determine the stable and unstable phases of the black hole. Our findings show that large and small phase transitions of black hole occur at a specific value of the deflection angle.

Formation of primordial black holes after Starobinsky inflation

In this paper, we adapted the Appleby–Battye–Starobinsky model of [Formula: see text] gravity towards describing double cosmological inflation and formation of primordial black holes with masses up to [Formula: see text] g in the single-field model. We found that it is possible to get an enhancement of the power spectrum of scalar curvature perturbations to the level beyond the Hawking (black hole evaporation) limit of [Formula: see text] g, so that the primordial black holes resulting from gravitational collapse of those large primordial perturbations can survive in the present universe and form part of cold dark matter. Our results agree with the current measurements of cosmic microwave background radiation within [Formula: see text] but require fine-tuning of the parameters.

Doubly peaked induced stochastic gravitational wave background: testing baryogenesis from primordial black holes

Hawking evaporation of primordial black holes (PBHs) can facilitate the generation of matter-antimatter asymmetry. We focus on ultra-low mass PBHs that briefly dominate the universe and evaporate before the big bang nucleosynthesis. We propose a novel test of this scenario by detecting its characteristic doubly peaked gravitational wave (GW) spectrum in future GW observatories. Here the first order adiabatic perturbation from inflation and from the isocurvature perturbations due to PBH distribution, source tensor perturbations in second-order and lead to two peaks in the induced GW background. These resonant peaks are generated at the beginning of standard radiation domination in the presence of a prior PBH-dominated era. This unique GW spectral shape would provide a smoking gun signal of non-thermal baryogenesis from evaporating PBHs, which is otherwise impossible to test in laboratory experiments due to the very high energy scales involved or the feeble interaction of the dark sector with the visible sector.

A faster growth of perturbations in an early matter dominated epoch: primordial black holes and gravitational waves

ABSTRACT We present a scenario for fast growth of cosmological perturbations; δ(t) ∼ a(t)s, a(t) being the scale factor, with s > 10 for the numerical examples reported in this article. The basic ingredients of the scenario are an early matter dominated era and the dark fermion, which experiences a scalar mediated force during the epoch. Both of these arise in string/supergravity models. The fast growth occurs for sub-horizon density perturbations of the dark fermion. The fast growth has a rich set of phenomenological implications. We outline implications for the formation of primordial black holes and the production of gravitational waves. Primordial black holes in the sublunar mass range (which are ideal dark matter candidates) can be produced. Gravitational waves can be produced in a wide range of frequencies due to second-order scalar perturbations and due to evaporation and merger of primordial black holes.

Probability distribution for black hole evaporation

Nonthermal correction to the emission probability of particles from black holes can be obtained if the backreaction or self-gravitational effects of the emitted particles on the black hole spacetime are taken into consideration. These nonthermally emitted particles conserve the entropy of the black hole---i.e., the entropy of the system of radiated particles after complete evaporation of the black hole matches the initial entropy of the black hole. Using the nonthermal emission probability, we have determined the probability for a black hole of mass $M$ to be completely evaporated by a given number of particles $n$. This is done by first evaluating the number of possible ways in which the black hole can be evaporated by emitting $n$ number of particles, and then the total number of ways in which the black hole can be evaporated. The ratio of these two quantities gives us the desired probability. From the probability distribution, we get a displacement relation between the most probable number of particles exhausting the black hole and the temperature of the initial black hole. This relation resembles Wien's displacement law for blackbody radiation.

Black holes and their horizons in semiclassical and modified theories of gravity

For distant observers, black holes are trapped spacetime domains bounded by apparent horizons. We review properties of the near-horizon geometry emphasizing the consequences of two common implicit assumptions of semiclassical physics. The first is a consequence of the cosmic censorship conjecture, namely, that curvature scalars are finite at apparent horizons. The second is that horizons form in finite asymptotic time (i.e. according to distant observers), a property implicitly assumed in conventional descriptions of black hole formation and evaporation. Taking these as the only requirements within the semiclassical framework, we find that in spherical symmetry only two classes of dynamic solutions are admissible, both describing evaporating black holes and expanding white holes. We review their properties and present the implications. The null energy condition is violated in the vicinity of the outer horizon and satisfied in the vicinity of the inner apparent/anti-trapping horizon. Apparent and anti-trapping horizons are timelike surfaces of intermediately singular behavior, which manifests itself in negative energy density firewalls. These and other properties are also present in axially symmetric solutions. Different generalizations of surface gravity to dynamic spacetimes are discordant and do not match the semiclassical results. We conclude by discussing signatures of these models and implications for the identification of observed ultra-compact objects.

Replica wormholes and holographic entanglement negativity

Recent work has shown how to understand the Page curve of an evaporating black hole from replica wormholes. However, more detailed information about the structure of its quantum state is needed to fully understand the dynamics of black hole evaporation. Here we study entanglement negativity, an important measure of quantum entanglement in mixed states, in a couple of toy models of evaporating black holes. We find four phases dominated by different types of geometries: the disconnected, cyclically connected, anti-cyclically connected, and pairwise connected geometries. The last of these geometries are new replica wormholes that break the replica symmetry spontaneously. We also analyze the transitions between these four phases by summing more generic replica geometries using a Schwinger-Dyson equation. In particular, we find enhanced corrections to various negativity measures near the transition between the cyclic and pairwise phase.

The Page curve for reflected entropy

We study the reflected entropy SR in the West Coast Model, a toy model of black hole evaporation consisting of JT gravity coupled to end-of-the-world branes. We demonstrate the validity of the holographic duality relating it to the entanglement wedge cross section away from phase transitions. Further, we analyze the important non-perturbative effects that smooth out the discontinuity in the SR phase transition. By performing the gravitational path integral, we obtain the reflected entanglement spectrum analytically. The spectrum takes a simple form consisting of superselection sectors, which we interpret as a direct sum of geometries, a disconnected one and a connected one involving a closed universe. We find that area fluctuations of O ( sqrt{G_N} ) spread out the SR phase transition in the canonical ensemble, analogous to the entanglement entropy phase transition. We also consider a Renyi generalization of the reflected entropy and show that the location of the phase transition varies as a function of the Renyi parameter.

Quantum chaos and unitary black hole evaporation

The formation and evaporation of small AdS black holes in a theory with a holographic dual is governed by the usual rules of quantum mechanics. The eigenstate thermalization hypothesis explains the validity of semiclassical gravity for local bulk observables and can be used to quantify the magnitude of quantum corrections to the semi-classical approximation. The holographic dual produces a basis of black hole states with finite energy width, and observables that are smooth functions on the classical phase space will self-average over a large number of energy eigenstates, exponential in the Bekenstein-Hawking entropy S, leading to results that are consistent with semiclassical gravity up to small corrections of order e−S/2. As expected, the semiclassical description breaks down for transition amplitudes that reflect the unitary evolution of the holographic theory.

Semiclassical gravitational collapse of a radially symmetric massless scalar quantum field

We present a method to study the semiclassical gravitational collapse of a radially symmetric scalar quantum field in a coherent initial state. The formalism utilizes a Fock space basis in the initial metric, is unitary and time reversal invariant up to numerical precision. It maintains exact compatibility of the metric with the expectation values of the energy momentum tensor in the scalar field coherent state throughout the entire time evolution. We find a simple criterion for the smallness of discretization effects, which is violated when a horizon forms. As a first example, we study the collapse of a specific state in the angular momentum $l=0$ approximation. Outside the simulated volume it produces a Schwarzschild metric with $r_s \sim 3.5 \ell_p$. We see behaviour that is compatible with the onset of horizon formation both in the semiclassical and corresponding classical cases in a regime where we see no evidence for large discretization artefacts. In our example setting, we see that quantum effects accelerate the possible horizon formation and move it radially outward. We find that this effect is robust against variations of the radial resolution, the time step, the volume, the initial position and shape of the inmoving state, the vacuum subtraction, the discretization of the time evolution operator and the integration scheme of the metric. We briefly discuss potential improvements of the method and the possibility of applying it to black hole evaporation. We also briefly touch on the extension of our formalism to higher angular momenta, but leave the details and numerics for a forthcoming publication.

Primordial black holes as dark matter candidates

We review the formation and evaporation of primordial black holes (PBHs) and their possible contribution to dark matter. Various constraints suggest they could only provide most of it in the mass windows 10^{17}\;1017 – 10^{23}\;1023g or 1010 – 10^2\;M_{\odot}102M⊙, with the last possibility perhaps being suggested by the LIGO/Virgo observations. However, PBHs could have important consequences even if they have a low cosmological density. Sufficiently large ones might generate cosmic structures and provide seeds for the supermassive black holes in galactic nuclei. Planck-mass relics of PBH evaporations or stupendously large black holes bigger than 10^{12}\;M_{\odot}1012M⊙ could also be an interesting dark component.