275 research outputs found
Hawking Radiation and Covariant Anomalies
Generalising the method of Wilczek and collaborators we provide a derivation
of Hawking radiation from charged black holes using only covariant gauge and
gravitational anomalies. The reliability and universality of the anomaly
cancellation approach to Hawking radiation is also discussed.Comment: Minor changes, conforms to published versio
Hawking Radiation, Covariant Boundary Conditions and Vacuum States
The basic characteristics of the covariant chiral current are obtained from a
chiral effective action. These results are used to justify the covariant
boundary condition used in recent approaches
\cite{Isowilczek,Isoumtwilczek,shailesh,shailesh2,Banerjee} of computing the
Hawking flux from chiral gauge and gravitational anomalies. We also discuss a
connection of our results with the conventional calculation of nonchiral
currents and stress tensors in different (Unruh, Hartle-Hawking and Boulware)
states.Comment: 18 pages, no figures, minor changes, to appear in Phys. Rev.
An open--quantum--system formulation of particle decay
We consider an open quantum system which contains unstable states. The time
evolution of the system can be described by an effective non-hermitian
Hamiltonian H_{eff}, in accord with the Wigner--Weisskopf approximation, and an
additional term of the Lindblad form, the socalled dissipator. We show that,
after enlarging the original Hilbert space by states which represent the decay
products of the unstable states, the non-hermitian part of H_{eff} --the
``particle decay''-- can be incorporated into the dissipator of the enlarged
space via a specific Lindblad operator. Thus the new formulation of the time
evolution on the enlarged space has a hermitian Hamiltonian and is probability
conserving. The equivalence of the new formulation with the original one
demonstrates that the time evolution which is governed by a non-hermitian
Hamiltonian and a dissipator of the Lindblad form is nevertheless completely
positive, just as systems with hermitian Hamiltonians.Comment: 8 page
Hawking Radiation via Gravitational Anomalies in Non-spherical Topologies
We study the method of calculating the Hawking radiation via gravitational
anomalies in gravitational backgrounds of constant negative curvature. We apply
the method to topological black holes and also to topological black holes
conformally coupled to a scalar field.Comment: 25 pages, no figures, version to be published in Phys. Rev.
Decoherence of entangled kaons and its connection to entanglement measures
We study the time evolution of the entangled kaon system by considering the
Liouville - von Neumann equation with an additional term which allows for
decoherence. We choose as generators of decoherence the projectors to the
2-particle eigenstates of the Hamiltonian. Then we compare this model with the
data of the CPLEAR experiment and find in this way an upper bound on the
strength of the decoherence. We also relate to an effective
decoherence parameter considered previously in literature. Finally we
discuss our model in the light of different measures of entanglement, i.e. the
von Neumann entropy , the entanglement of formation and the concurrence
, and we relate the decoherence parameter to the loss of
entanglement: .Comment: comments and references added, 18 pages, 1 figur
Anomalies, Horizons and Hawking radiation
Hawking radiation is obtained from the Reissner-Nordstr\"{o}m blackhole with
a global monopole and the Garfinkle-Horowitz-Strominger blackhole falling in
the class of the most general spherically symmetric blackholes
, using only chiral anomaly near the event horizon and
covariant boundary condition at the event horizon. The approach differs from
the anomaly cancellation approach since apart from the covariant boundary
condition, the chiral anomaly near the horizon is the only input to derive the
Hawking flux.Comment: minor corrections made, To appear in Euro. Phys. Letter
Canonical Formalism for a 2n-Dimensional Model with Topological Mass Generation
The four-dimensional model with topological mass generation that was found by
Dvali, Jackiw and Pi has recently been generalized to any even number of
dimensions (2n-dimensions) in a nontrivial manner in which a Stueckelberg-type
mass term is introduced [S. Deguchi and S. Hayakawa, Phys. Rev. D 77, 045003
(2008), arXiv:0711.1446]. The present paper deals with a self-contained model,
called here a modified hybrid model, proposed in this 2n-dimensional
generalization and considers the canonical formalism for this model. For the
sake of convenience, the canonical formalism itself is studied for a model
equivalent to the modified hybrid model by following the recipe for treating
constrained Hamiltonian systems. This formalism is applied to the canonical
quantization of the equivalent model in order to clarify observable and
unobservable particles in the model. The equivalent model (with a gauge-fixing
term) is converted to the modified hybrid model (with a corresponding
gauge-fixing term) in a Becchi-Rouet-Stora-Tyutin (BRST)-invariant manner.
Thereby it is shown that the Chern-Pontryagin density behaves as an observable
massive particle (or field). The topological mass generation is thus verified
at the quantum-theoretical level.Comment: 29 pages, no figures, minor corrections, published versio
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