arXiv subjects

Zheng Zhao

Publications and source records attributed to Zheng Zhao.

101 records · Page 6Linked to original sources

arXiv2010

Discussion on Event Horizon and Quantum Ergosphere of Evaporating Black Holes in a Tunnelling Framework

In this paper, with the Parikh-Wilczek tunnelling framework the positions of the event horizon of the Vaidya black hole and the Vaidya-Bonner black hole are calculated respectively. We find that the event horizon and the apparent horizon of these two black holes correspond respectively to the two turning points of the Hawking radiation tunnelling barrier. That is, the quantum ergosphere coincides with the tunnelling barrier. Our calculation also implies that the Hawking radiation comes from the apparent horizon.

hep-th↗

arXiv2010

Tortoise coordinate and Hawking effect in the Kinnersley spacetime

Hawking effect from the Kinnersley spacetime is investigated using the improved Damour-Ruffini method with a new coordinate transformation. Hawking temperature of the horizons can be obtained point by point. It is found that Hawking temperatures of different points on the horizons are different. Especially, Hawking temperature of Rindler horizon is investigated. The touch between a Kinnersley black hole and its Rindler horizon is considered, and it shows that the phenomenon is related to the third law of thermodynamics.

gr-qc↗

arXiv2010

A note on the Hawking radiation calculated by the quasi-classical tunneling method

Since Parikh and Wilczek's tunneling method was proposed, there have been many generalizations, such as its application to massive charged particles' tunneling and other spacetimes. Moreover, a variant tunneling method was also recently proposed by Angheben et al that it was independent of coordinates. However, there are some subtleties in the calculation of Hawking radiation, and particularly is the so-called factor of 2 problem during calculating the Hawking temperature. The most popular opinion on this problem is that it is just a problem of the choice of coordinates. However, following other treatments we show that we can also consider this problem as a problem that we do not consider the contribution from P(absorption). Moreover, we also give some subtleties in the balance method and some comparisons with other treatments. In addition, as Parikh and Wilczek's original works have showed that if one takes the tunneling particles' back-reaction into account, the Hawking radiation would be modified, and this modification is underlying consistent with the unitary theory, we further find that this modification is also underlying correlated with the laws of black hole thermodynamics. Furthermore, we show that this tunneling method may be valid just when the tunneling process is reversible.

gr-qc↗

arXiv2009

Some properties of accelerating observers in the Schwarzschild space

It is well known that observers will be accelerated when they approach the planets. Thus, discussing the properties of accelerating observers in the Schwarzschild space is of sense. For the sake of simplicity, we can construct these observers' world lines by comparing with the observers in the Hawking effect and Unruh effect, whose world lines are both hyperbolic curves in the appropriate coordinates. We do it after defining a certain special null hypersurface in the Kruskal coordinates. Our result shows that these accelerating observers defined in our paper can also detect the radiation with the analogy of the Unruh effect, though locally. Furthermore, we conjecture that, for any null hypersurface in any spacetime, the corresponding observers who can at least locally detect the radiation from it can be found.

gr-qc↗

arXiv2006

Massive uncharged and charged particles' tunneling from the Horowitz-Strominger Dilaton black hole

Originally, Parikh and Wilczek's work is only suitable for the massless particles' tunneling. But their work has been further extended to the cases of massive uncharged and charged particles' tunneling recently. In this paper, as a particular black hole solution, we apply this extended method to reconsider the tunneling effect of the H.S Dilaton black hole. We investigate the behavior of both massive uncharged and charged particles, and respectively calculate the emission rate at the event horizon. Our result shows that their emission rates are also consistent with the unitary theory. Moreover, comparing with the case of massless particles' tunneling, we find that this conclusion is independent of the kind of particles. And it is probably caused by the underlying relationship between this method and the laws of black hole thermodynamics.

gr-qc↗

arXiv2006

Massive particles' Hawking radiation via tunneling from the G.H Dilaton black hole

In the past, Hawking radiation was viewed as a tunneling process and the barrier was just created by the outgoing particle itself. In this paper, Parikh's recent work is extended to the case of massive particles' tunneling. We investigate the behavior of the tunneling massive particles from a particular black hole solution-G.H Dilaton black hole which is obtained from the string theory, and calculate the emission rate at which massive particles tunnel across the event horizon. We obtain that the result is also consistent with an underlying unitary theory. Furthermore, the result takes the same functional form as that of massless particles.

gr-qc↗

arXiv2006

Tunnelling Effect and Hawking Radiation from a Vaidya Black Hole

In this paper, we extend Parikh' work to the non-stationary black hole. As an example of the non-stationary black hole, we study the tunnelling effect and Hawking radiation from a Vaidya black hole whose Bondi mass is identical to its mass parameter. We view Hawking radiation as a tunnelling process across the event horizon and calculate the tunnelling probability. We find that the result is different from Parikh's work because $\frac{dr_{H}}{dv}$ is the function of Bondi mass m(v).

gr-qc↗

arXiv2006

The relation between Hawking radiation via tunnelling and the laws of black hole thermodynamics

In Parikh and Wilczek's original works, the laws of black hole thermodynamics are not referred and it seems that there is no relation between Hawking radiation via tunnelling and the laws of black hole thermodynamics in their works. However, taking examples for the R-N black hole and the Kerr black hole, we find that they are correlated and even consistent if the tunnelling process is a reversible process.

gr-qc↗

arXiv2006

Information Loss in Black Hole Evaporation

Parikh-Wilczek tunnelling framework is investigated again. We argue that Parikh-Wilczek's treatment, which satisfies the first law of black hole thermodynamics and consists with an underlying unitary theory, is only suitable for a reversible process. Because of the negative heat capacity, an evaporating black hole is a highly unstable system. That is, the factual emission process is irreversible, the unitary theory will not be satisfied and the information loss is possible.

hep-th↗

arXiv2005

Charged particles' tunnelling from the Kerr-Newman black hole

In this letter, Parikh-Wilczek tunnelling framework, which treats Hawking radiation as a tunnelling process, is extended, and the emission rate of a charged particle tunnelling from the Kerr-Newman black hole is calculated. The emission spectrum takes the same functional form as that of uncharged particles and consists with an underlying unitary theory but deviates from the pure thermal spectrum. Moreover, our calculation indicates that the emission process is treated as a reversible process in the Parikh-Wilczek tunnelling framework, and the information conservation is a natural result of the first law of black hole thermodynamics.

gr-qc↗

arXiv2004

Could the Gravitons Have Rest Masses?

If the cosmological constant $Λ$ can not be neglected, we will show in this short report, that graviton should have a rest mass $m_g=\sqrt{2Λ}=\sqrt{2Λ}\hbar c^{-1}$ different from zero.

gr-qc↗