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 $$and the covariant chiral energy-momentum tensor$$ 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 $\lambda$ of the decoherence. We also relate $\lambda$ to an effective decoherence parameter $\zeta$ considered previously in literature. Finally we discuss our model in the light of different measures of entanglement, i.e. the von Neumann entropy $S$, the entanglement of formation $E$ and the concurrence $C$, and we relate the decoherence parameter $\zeta$ to the loss of entanglement: $1 - E$.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 $(\sqrt{-g}\neq1)$, 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