Author

# Daniel J. Loranz

Bio: Daniel J. Loranz is an academic researcher from Montana State University. The author has contributed to research in topics: Event horizon & Charged black hole. The author has an hindex of 3, co-authored 3 publications receiving 128 citations.

##### Papers

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TL;DR: The stress-energy tensor of a free quantized scalar field is calculated in the extreme Reissner-Nordstrom black hole spacetime in the zero-temperature vacuum state and appears to be regular on the event horizon, contrary to the suggestion provided by two-dimensional calculations.

Abstract: The stress-energy tensor of a free quantized scalar field is calculated in the extreme Reissner-Nordstr\"om black hole spacetime in the zero-temperature vacuum state. The stress-energy appears to be regular on the event horizon, contrary to the suggestion provided by two-dimensional calculations. An analytic calculation on the event horizon for a thermal state shows that if the temperature is nonzero then the stress-energy diverges strongly there.

86 citations

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TL;DR: It is found that for every static two-dimensional black hole the stress-energy diverges strongly on the event horizon unless the field is in a state at the natural black hole temperature, which is defined by the surface gravity of theevent horizon.

Abstract: The expectation value of the stress-energy tensor $\langleT_{\mu
u}\rangle$ of a free conformally invariant scalar field is computed in a general static two-dimensional black hole spacetime when the field is in either a zero temperature vacuum state or a thermal state at a nonzero temperature. It is found that for every static two-dimensional black hole the stress-energy diverges strongly on the event horizon unless the field is in a state at the natural black hole temperature which is defined by the surface gravity of the event horizon. This implies that both extreme and nonextreme two-dimensional black holes can only be in equilibrium with radiation at the natural black hole temperature.

36 citations

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TL;DR: In this paper, the stress energy tensor of a quantized scalar field is computed in the reduced two-dimensional charged dilatonic black hole spacetime of Garfinkle, Horowitz, and Strominger.

Abstract: The stress-energy tensor of a quantized scalar field is computed in the reduced two-dimensional charged dilatonic black hole spacetime of Garfinkle, Horowitz, and Strominger. In order for the stress-energy of quantized fields to be regular on the event horizon in both the extreme string metric and the conformally associated physical metric, it is necessary to assign a nonzero temperature, T = (8 pi e^{phi_0} M)^{-1}, to the extreme string metric, contrary to the expectation that this horizonless spacetime would have a natural temperature of zero.

9 citations

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TL;DR: In this article, the semi-classical methods for computing the conditions for Hawking radiation as tunneling are revisited and applied also to rotating black hole solutions as well as to the extremal cases.

Abstract: The issue concerning semi-classical methods recently developed in deriving the conditions for Hawking radiation as tunneling, is revisited and applied also to rotating black hole solutions as well as to the extremal cases. It is noticed how the tunneling method fixes the temperature of extremal black hole to be zero, unlike the euclidean regularity method that allows an arbitrary compactification period. A comparison with other approaches is presented.

453 citations

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TL;DR: In this paper, the semi-classical methods for computing the conditions for Hawking radiation as tunneling are revisited and applied also to rotating black hole solutions as well as to the extremal cases.

Abstract: The issue concerning semi-classical methods recently developed in deriving the conditions for Hawking radiation as tunneling, is revisited and applied also to rotating black hole solutions as well as to the extremal cases. It is noticed how the tunneling method fixes the temperature of extremal black hole to be zero, unlike the Euclidean regularity method that allows an arbitrary compactification period. A comparison with other approaches is presented.

398 citations

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TL;DR: A fluctuation-dissipation relation between the fluctuations in the radiation and the dissipative dynamics of metric fluctuations is derived and a general expression for the noise kernel of a quantum field defined at two distinct points in an arbitrary curved spacetime is obtained.

Abstract: Whereas semiclassical gravity is based on the semiclassical Einstein equation with sources given by the expectation value of the stress-energy tensor of quantum fields, stochastic semiclassical gravity is based on the Einstein-Langevin equation, which has in addition sources due to the noise kernel. The noise kernel is the vacuum expectation value of the (operatorvalued) stress-energy bi-tensor which describes the fluctuations of quantum matter fields in curved spacetimes. In the first part, we describe the fundamentals of this new theory via two approaches: the axiomatic and the functional. The axiomatic approach is useful to see the structure of the theory from the framework of semiclassical gravity, showing the link from the mean value of the stress-energy tensor to their correlation functions. The functional approach uses the Feynman-Vernon influence functional and the Schwinger-Keldysh closed-time-path effective action methods which are convenient for computations. It also brings out the open systems concepts and the statistical and stochastic contents of the theory such as dissipation, fluctuations, noise, and decoherence. We then focus on the properties of the stress-energy bi-tensor. We obtain a general expression for the noise kernel of a quantum field defined at two distinct points in an arbitrary curved spacetime as products of covariant derivatives of the quantum field's Green function. In the second part, we describe three applications of stochastic gravity theory. First, we consider metric perturbations in a Minkowski spacetime. We offer an analytical solution of the Einstein-Langevin equation and compute the two-point correlation functions for the linearized Einstein tensor and for the metric perturbations. Second, we discuss structure formation from the stochastic gravity viewpoint, which can go beyond the standard treatment by incorporating the full quantum effect of the inflaton fluctuations. Third, we discuss the backreaction of Hawking radiation in the gravitational background of a quasi-static black hole (enclosed in a box). We derive a fluctuation-dissipation relation between the fluctuations in the radiation and the dissipative dynamics of metric fluctuations.

212 citations

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TL;DR: In this paper, the statistical mechanics of quantum systems in the presence of a Killing horizon are described and compared to statistical-mechanical and 1-loop contributions to black-hole entropy.

Abstract: In this review we describe the statistical mechanics of quantum systems in the presence of a Killing horizon and compare statistical-mechanical and 1-loop contributions to black-hole entropy. The study of these questions was motivated by attempts to explain the entropy of black holes as a statistical-mechanical entropy of quantum fields propagating near the black-hole horizon. We provide an introduction to this field of research and review its results. In particular, we discuss the relation between the statistical-mechanical entropy of quantum fields and the Bekenstein-Hawking entropy in the standard scheme with renormalization of gravitational coupling constants and in the theories of induced gravity.

96 citations

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TL;DR: In this article, the authors revisited the study of (A)dS black holes in Lovelock theories and presented a new tool that allows to attack this problem in full generality.

Abstract: We revisit the study of (A)dS black holes in Lovelock theories. We present a new tool that allows to attack this problem in full generality. In analyzing maximally symmetric Lovelock black holes with non-planar horizon topologies, many distinctive and interesting features are observed. Among them, the existence of maximally symmetric vacua does not support black holes in vast regions of the space of gravitational couplings, multi-horizon black holes and branches of solutions that suggest the existence of a rich diagram of phase transitions. The appearance of naked singularities seems unavoidable in some cases, raising the question about the fate of the cosmic censorship conjecture in these theories. There is a preferred branch of solutions for planar black holes, as well as for non-planar black holes with high enough mass or temperature. Our study clarifies the role of all branches of solutions, including asymptotically dS black holes, and whether they should be considered when studying these theories in the context of AdS/CFT.

95 citations