Hawking Temperature Research Articles

Higgs phonon: conformal phonon and Hawking temperature in a two-dimensional acoustic black hole model

Higgs phonon: conformal phonon and Hawking temperature in a two-dimensional acoustic black hole model

Separating the superradiant emission from the Hawking radiation from a rotating black hole

Emission of particles created in the background of a rotating black hole can be greatly amplified taking away rotational energy of a black hole. This amplification affects both particles created near the horizon (due to the Hawing effect), and particles created near the potential barrier far from the horizon. Only the latter effect is called the superradiance in the strict sense. We explicitly calculate the superradiant emission for scalar particles and compare it with the total scalar particle emission (Hawking radiation plus superradiance) to clarify some confusion in the literature. We clearly show that these two emissions are not the same. In particular, superradiance persists even for extremal black holes whose Hawking temperature is zero.

Black holes that are too cold to respect cosmic censorship

In this essay, it is proved that there are black holes that are dangerously cold. In particular, by analyzing the emission spectra of highly charged black holes we reveal the fact that near-extremal black holes whose Bekenstein–Hawking temperatures lie in the regime [Formula: see text] may turn into horizonless naked singularities, thus violating the cosmic censorship principle, if they emit a photon with the characteristic thermal energy [Formula: see text] (here [Formula: see text] are, respectively, the proper mass and the electric charge of the electron, the lightest charged particle). We therefore raise here the conjecture that, in the yet unknown quantum theory of gravity, the temperatures of well-behaved black-hole spacetimes are fundamentally bounded from below by the relation [Formula: see text].

On the Global Temperature of the Schwarzschild–de Sitter Spacetime

It is shown that the Schwarzschild–de Sitter spacetime has the universal temperature. This temperature describes the thermal processes of decay of the composite particles and the other processes, which are energetically forbidden in the Minkowski spacetime, but are allowed in the de Sitter and in Schwarzschild–de Sitter backgrounds. In particular, this temperature describes the probability of ionization of the atom in the Schwarzschild–de Sitter, which is observed by the stationary observer at the point where the shift function (velocity) in the Arnowitt–Deser–Misner formalism changes sign. This activation temperature does not depend on the black hole mass and is fully determined by the Hubble parameter, {{T}_{{{text{SdS}}}}} = sqrt 3 H{text{/}}pi . This temperature is twice the Bousso–Hawking temperature {{T}_{{{text{BH}}}}}, which characterizes the limit of degenerate Lorentzian Schwarzschild–de Sitter universe, when the cosmological and black hole horizons are close to each other, {{T}_{{{text{SdS}}}}} = 2{{T}_{{{text{BH}}}}}. The similar doubling of the temperature of Hawking radiation is known in the pure de Sitter spacetime, where the corresponding local temperature describing the ionization of atoms is twice the Gibbons–Hawking temperature, {{T}_{{{text{dS}}}}} = 2{{T}_{{{text{GH}}}}} = H{text{/}}pi . We suggest that the activation temperature {{T}_{{{text{dS}}}}} can be considered as the thermodynamic temperature of the de Sitter state, which determines the local entropy in this state, s = 3H{text{/}}4G.

The Correction of Quantum Tunneling Rate and Entropy of Non-Stationary Spherically Symmetric Black Hole by Lorentz Breaking

With the introduction of CFJ correction term, Chiral correction term, and aether-like correction term, based on Lorentz breaking, WKB approximate, and quantum tunneling radiation theory of black holes, the modified fermion dynamics equation is studied in the general non-stationary spherically symmetric black hole space-time, and the new modified expressions of the fermion tunneling rate, the Hawking temperature, and the Bekenstein–Hawking entropy of the black hole are obtained. This black hole has both thermal and non-thermal radiation. In this article, the influence of Lorentz breaking on the energy levels of Dirac particles was also studied, and the distribution characteristics of Dirac energy levels in the space-time and the maximum value of the crossing of positive and negative energy levels were obtained. The necessary discussion and the explanation of the corresponding results are made.

Semiclassical instability of inner-extremal regular black holes

The construction of black hole spacetimes that are regular (singularity-free) is plagued by the ``mass inflation'' instability, a classical perturbation instability induced by the surface gravity at the inner horizon and characterized by exponentially diverging stress energy there. Recently, a class of ``inner-extremal'' regular black holes was proposed that possesses a vanishing inner horizon surface gravity and therefore avoids mass inflation, while still maintaining a horizon separation and a nonzero outer-horizon surface gravity. However, when semiclassical effects are taken into account, it is found that an inner-horizon instability remains for generic inner-extremal regular black holes formed from collapse. This semiclassical divergence is analyzed from the perspective of both the effective Hawking temperature and the renormalized stress-energy tensor, and its origin and genericity are examined in detail.

Thermodynamic properties of Schwarzschild black hole in non-commutative gauge theory of gravity

In this paper, we use the non-commutative (NC) gauge theory of gravity to investigate the thermodynamic properties of a deformed Schwarzschild Black Hole (SBH). Our results present a new scenario of black hole evaporation. As a first step, we describe the Arnowitt–Deser–Misner (ADM) mass, the Hawking temperature, and the entropy of NC SBH. The non-commutativity removes the divergent behavior of temperature, and the result shows a difference in the pole-equator temperature. These corrections also reveal a new fundamental length at the Planck scale order, Θ∼10−35m. In the last stage of evaporation, the NC correction exposes a remnant entropy S0Θ of the NC SBH with a minimal mass mˆ0, where the non-commutativity prevents the black hole from evaporating more than this minimal mass. Then, the description of the heat capacity and the Helmholtz free energy of the deformed black hole shows the effect of the NC gauge theory on the thermodynamic stability and the phase transitions. Finally, we investigate the influence of the black hole pressure on the stability and the phase transition of SBH in NC space–time. In the final stage of this scenario, the remnant black hole is thermodynamically stable. In this study, we find that the NC parameter plays a role similar to the thermodynamic variable. The results show a second-order phase transition of NC SBH.

Modified Hawking temperature and entropy of Kerr–de Sitter black hole in Lorentz violation theory

In this paper, we discuss the tunneling of scalar particles near the event horizon of stationary and nonstationary Kerr–de Sitter black hole using Lorentz violation theory in curved space time. The modified form of Hamilton–Jacobi equation is derived from the Klein–Gordon equation by applying Lorentz violation theory. The Hawking temperatures derived from stationary and nonstationary Kerr–de Sitter black holes are modified due to Lorentz violation theory. It is noted that the change in Bekenstein–Hawking entropy and modified Hawking temperatures of stationary and nonstationary Kerr–de Sitter black hole not only depends on the black hole parameters but also on ether-like vectors [Formula: see text].

Curved spacetime as a dispersive multiferroic medium for an electromagnetic wave: Polarization and magnetization vectors in the Schwarzschild spacetime

We study one of the interesting properties of the electromagnetic wave propagation in the Schwarzschild background spacetime in the framework of general relativity (GR). The electromagnetic wave equation has been derived from vacuum general relativistic Maxwell’s equations. It is shown that the solutions for the electromagnetic field can be expanded in the spherical harmonic functions and all components of the electromagnetic fields can be expressed in terms of two radial profile functions. These radial profile functions can be expressed in terms of the confluent Heun function. The calculated behavior of the electric and magnetic susceptibilities near the event horizon appears to be similar to the susceptibilities of multiferroic materials near phase transition. The Curie temperature of this phase transition appears to coincide with the Hawking temperature.

Impact of trans-Planckian excitations on black-hole radiation in dipolar condensates

We consider a quasi-one-dimensional dipolar condensate in a steplike analog black hole setup. It is shown that the existence of roton excitations leaves significant imprints onto the Hawking radiation spectrum. The emitted radiation depends on the depth of the roton minimum, and is in general more intense. In addition, we find a novel spontaneous particle creation mechanism with no counterpart in nondipolar condensates. Our results establish that dipolar condensates offer a richer and more versatile environment for the simulation of particle production from the quantum vacuum in the presence of horizon interfaces than contact-interaction condensates.

Black String Solutions in Rainbow Gravity

In this paper, we studied black string solutions under the consideration of rainbow gravity. We analytically obtained the solution for four-dimensional black strings in terms of the functions f(E/Ep) and g(E/Ep) that sets the energy scale where the rainbow gravity becomes relevant. We also obtained the Hawking temperature for the black string, from which we can see that the rainbow functions play the role of increasing or decreasing the Hawking temperature for a given horizon radius depending on the choice of such rainbow functions. We computed the entropy, specific heat and free energy for the black string. The entropy and specific heat exhibit a rainbow dependence, whereas the free energy is not modified by the rainbow functions. Finally, we studied the effects of rainbow gravity in the orbits of massive and massless particles around a black string. We could verify that neither massive nor massless particles exhibit stable orbits around a black string in the scenario of rainbow gravity for any configuration of rainbow functions.

Generalized uncertainty principle impact on nonextensive black hole thermodynamics

The effect of the generalized uncertainty principle (GUP) on nonextensive thermodynamics applied to black holes, as well as the sparsity of the radiation at different temperatures associated with each nonextensive entropy, is investigated. We examine the Rényi, Tsallis–Cirto, Kaniadakis, Sharma Mittal, and Barrow entropies, temperatures, and heat capacities and show that, in each case, due to GUP corrections, the temperature and entropy have finite values, implying that the final state of the black hole is a remnant at the end of the evaporation process and that the sparsity of the radiation for massless bosons at each temperature depends on the mass of the black hole. We also find that GUP reduces the value of the sparsity profile for each case as compared to the sparsity parameter at Hawking temperature, which is always constant throughout the evaporation.

Massive vector particle tunneling from Kerr-Newman-de Sitter black hole under generalized uncertainty principle

The quantum tunneling of charged massive vector boson particles across the event horizon of Kerr-Newman-de Sitter black hole is investigated under the influence of quantum gravity effects. The modified Hawking temperatures and heat capacities across the event horizon of KNdS black hole are derived in 3-dimensional and 4-dimensional frame dragging coordinates. It is found that due to quantum gravity effects the modified Hawking temperatures and heat capacities depend on the mass and angular momentum of the emitted vector boson particles. For 3-dimensional KNdS black hole, the modified Hawking temperature is lower than the original Hawking temperature but the modified heat capacity is higher than the original heat capacity due to quantum gravity effects. In the case of 4-dimensional KNdS black hole, the modified Hawking temperature and heat capacity are lower or greater than the original Hawking temperature and heat capacity depending upon the choices of black hole parameters due to quantum gravity effects. We also discuss the remnant and graphical analysis of the modified Hawking temperatures and heat capacities.

Quantum simulation of Hawking radiation and curved spacetime with a superconducting on-chip black hole

Hawking radiation is one of the quantum features of a black hole that can be understood as a quantum tunneling across the event horizon of the black hole, but it is quite difficult to directly observe the Hawking radiation of an astrophysical black hole. Here, we report a fermionic lattice-model-type realization of an analogue black hole by using a chain of 10 superconducting transmon qubits with interactions mediated by 9 transmon-type tunable couplers. The quantum walks of quasi-particle in the curved spacetime reflect the gravitational effect near the black hole, resulting in the behaviour of stimulated Hawking radiation, which is verified by the state tomography measurement of all 7 qubits outside the horizon. In addition, the dynamics of entanglement in the curved spacetime is directly measured. Our results would stimulate more interests to explore the related features of black holes using the programmable superconducting processor with tunable couplers.

Mining the quantum vacuum: quantum tunnelling and particle creation

Particle production from the vacuum is a remarkable aspect of particle physics. Prime examples are the Schwinger process of particle production in strong electric fields and the Hawking process of particle production from black holes. These processes can be viewed as quantum tunnelling of particles from the vacuum. The tunnelling approach, and the closely related instanton or complex path approaches, are reviewed here with emphasis on paths in the complex coordinate plane. The method is applied to particle production from a black hole in a magnetic field, where ultra-high energy charged particles are produced.

On the Resilience of Black Hole Evaporation: Gravitational Tunneling through Universal Horizons

Using a quantum tunneling derivation, we show the resilience of Hawking radiation in Lorentz violating gravity. In particular, we show that the standard derivation of the Hawking effect in relativistic quantum field theory can be extended to Lorentz breaking situations thanks to the presence of universal horizons (causal boundaries for infinite speed signals) inside black hole solutions. Correcting previous studies, we find that such boundaries are characterized by a universal temperature governed by their surface gravity. We also show that within the tunneling framework, given the pole structure and the tunneling path, only a vacuum state set in the preferred frame provides a consistent picture. Our results strongly suggest that the robustness of black hole thermodynamics is ultimately linked to the consistency of quantum field theories across causal boundaries.

Hawking Radiation and Lifetime of Primordial Black Holes in Braneworld

The paper explores the thermodynamic properties of primordial black holes (PBHs) in the braneworld. Specifically, the researchers examined Hawking radiation and the lifetime of PBHs. Through their analysis, an exact analytical expression for the Bekenstein–Hawking entropy, temperature, and heat capacity was derived. Their findings suggest that the lifetime of PBHs in the early universe is reduced by at least one order of magnitude, ultimately leading to their evaporation. This could explain why we have not observed the final rapid evaporation of PBHs in the recent epoch of the universe.

Hawking radiation and stability of the canonical acoustic black holes

In this paper we determine the Hawking temperature and entropy of a modified canonical acoustic black hole. In our results we obtain an entropy-area relation that has a logarithmic correction term in leading order. We also analyze the stability condition of the noncommutative canonical acoustic black hole and also with quantum corrections implemented by the generalized Heisenberg uncertainty principle.

Conformal renormalization of scalar-tensor theories

We study a conformally coupled scalar-tensor theory with a quartic potential possessing local conformal symmetry up to a boundary term. We show that requiring the restoration of the full local conformal symmetry fixes the counterterms that render the on-shell action finite. The building block of the resulting action is a conformally covariant tensor which is constructed out of the metric and the scalar field and it has the same conformal weight as the Weyl tensor. This allows us to obtain the counterterms for the scalar-tensor sector in a closed form. The finiteness of the conformally complete version of the action is suggestive on the validity of the conformal renormalization prescription. We extend this theory by adding the conformal gravity action and also the Einstein-AdS action written in MacDowell-Mansouri form. Even though the latter breaks the conformal symmetry, we find that the action is still renormalized provided a suitable falloff of the scalar field when considering asymptotically locally anti-de Sitter solutions. Black hole solutions in these theories are studied, for which the Hawking temperature and the partition function to first order in the saddle-point approximation are calculated, providing a concrete example of this renormalization scheme.

Hawking temperature as the total Gauss–Bonnet invariant of the region outside a black hole

We provide two novel ways to compute the surface gravity (kappa ) and the Hawking temperature (T_{H}) of a stationary black hole: in the first method T_{H} is given as the three-volume integral of the Gauss–Bonnet invariant (or the Kretschmann scalar for Ricci-flat metrics) in the total region outside the event horizon; in the second method it is given as the surface integral of the Riemann tensor contracted with the covariant derivative of a Killing vector on the event horizon. To arrive at these new formulas for the black hole temperature (and the related surface gravity), we first construct a new differential geometric identity using the Bianchi identity and an antisymmetric rank-2 tensor, valid for spacetimes with at least one Killing vector field. The Gauss–Bonnet tensor and the Gauss–Bonnet scalar play a particular role in this geometric identity. We calculate the surface gravity and the Hawking temperature of the Kerr and the extremal Reissner–Nordström holes as examples.