Narrow Results

Hawking evaporation of Dirac particles and scalar fields in a Vaidya-type black hole is investigated by the method of generalized tortoise coordinate transformation. It is shown that Hawking radiation of Dirac particles does not exist for P₁, Q₂ components but for P₂, Q₁ components in any Vaidya-type black holes. Both the location and the temperature of the event horizon change with time. The thermal radiation spectrum of Dirac particles is the same as that of Klein–Gordon particles. We demonstrate that there is no new quantum ergosphere effect in the thermal radiation of Dirac particles in any spherically symmetry black holes.

In this paper, within the framework of open-system dynamics, we investigate the thermalization phenomena of Unruh effect and de Sitter spacetime. It is shown that the Unruh effect, thermal effect of de Sitter spacetime and Hawking effect are similar in nature.

By introducing a new Tortiose coordinate and using the notion of local equilibrium, we have studied the Hawking effect and the entropy of an arbitrarily accelerating Kerr black hole, a nonstationary black hole. The Bekenstein–Hawking entropy has been obtained by taking the same geometric cutoff relationship in the thin film model as that in the static case. Consequently, the results in the new Tortiose coordinate reveal the following two facts. First, it is correct in the opinion that the black hole entropy is determined by the horizon of a black hole, whether it is stationary or nonstationary. Second, the entropy of the nonstationary black hole shows some common essential natures with that of a static one.

What happens when Alice falls into a black hole? In spite of recent challenges by Almheiri et al. — the so-called "firewall" hypothesis —, the consensus on this question tends to remain "nothing special." Here I show that, besides the standard Hawking outgoing modes, Alice records at horizon-crossing a quasi-thermal spectrum of ingoing modes, whose temperature and intensity diverges as her Killing energy E goes to zero. I suggest that this effect can be thought of in terms a horizon-infinity duality, which relates the perception of near-horizon and asymptotic geodesic observers — the two faces of Hawking radiation.

We consider a microscopic model of a stretched horizon of the Reissner–Nordström black hole. In our model, the stretched horizon consists of discrete constituents. Using our model we obtain an explicit, analytic expression for the partition function of the hole. Our partition function implies, among other things, the Hawking effect, and provides it with a microscopic explanation as a phase transition taking place at the stretched horizon. The partition function also implies the Bekenstein–Hawking entropy law. The model and its consequences are similar to those obtained previously for the Schwarzschild black hole.

That event horizons generate quantum correlations via the Hawking effect is well known. We argue, however, that the creation of entanglement can be modulated, as desired, by appropriately illuminating the horizon. We adapt techniques from quantum information theory to quantify the entanglement produced during the Hawking process and show that, while ambient thermal noise (e.g. cosmic microwave background radiation) degrades it, the use of squeezed inputs can boost the nonseparability between the interior and exterior regions in a controlled manner. We further apply our ideas to analog event horizons concocted in the laboratory and insist that the ability to tune the generation of entanglement offers a promising route towards detecting quantum signatures of the elusive Hawking effect.

Hawking showed that a black hole formed by collapse will emit radiation and eventually disappear. We address the challenge to define an objective notion of physical entropy which increases throughout this process in a way consistent with unitarity. We have suggested that (instead of coarse-grained entropy) physical entropy is matter–gravity entanglement entropy and that this may offer an explanation of entropy increase both for the black hole collapse and evaporation system and also for other closed unitarily evolving systems. For this to work, the matter–gravity entanglement entropy of the late-time state of black hole evaporation would have to be larger than the entropy of the freshly formed black hole. We argue that this may possibly be the case due to (usually neglected) photon–graviton interactions.

We point out a problem of invariance in the usual “tunneling” method (Angheben et al., and following variants) frequently used to calculate the Hawking radiation in the semi-classical approximation. Indeed this naive “ΔW-only” method, which is good for flat space-time in Cartesian coordinates, does not work automatically in curvilinear coordinates since it is not coordinate invariant. Instead, using an invariant procedure analog to the one used by Popov for pair creation in constant electric field, we show that such creation-probability is zero due to a contribution of the time factor present in the complete action.