320 research outputs found
Quantum properties of the Dirac field on BTZ black hole backgrounds
We consider a Dirac field on a -dimensional uncharged BTZ black hole
background. We first find out the Dirac Hamiltonian, and study its
self-adjointness properties. We find that, in analogy to the Kerr-Newman-AdS
Dirac Hamiltonian in dimensions, essential self-adjointness on
of the reduced (radial) Hamiltonian is implemented
only if a suitable relation between the mass of the Dirac field and the
cosmological radius holds true. The very presence of a boundary-like
behaviour of is at the root of this problem. Also, we determine in a
complete way qualitative spectral properties for the non-extremal case, for
which we can infer the absence of quantum bound states for the Dirac field.
Next, we investigate the possibility of a quantum loss of angular momentum for
the -dimensional uncharged BTZ black hole. Unlike the corresponding
stationary four-dimensional solutions, the formal treatment of the level
crossing mechanism is much simpler. We find that, even in the extremal case, no
level crossing takes place. Therefore, no quantum loss of angular momentum via
particle pair production is allowed.Comment: 19 pages; IOP styl
Quantum radiation from superluminal refractive index perturbations
We analyze in detail photon production induced by a superluminal refractive
index perturbation in realistic experimental operating conditions. The
interaction between the refractive index perturbation and the quantum vacuum
fluctuations of the electromagnetic field leads to the production of photon
pairs.Comment: 4 page
Spacetime geometries and light trapping in travelling refractive index perturbations
In the framework of transformation optics, we show that the propagation of a
locally superluminal refractive index perturbation (RIP) in a Kerr medium can
be described, in the eikonal approximation, by means of a stationary metric,
which we prove to be of Gordon type. Under suitable hypotheses on the RIP, we
obtain a stationary but not static metric, which is characterized by an
ergosphere and by a peculiar behaviour of the geodesics, which are studied
numerically, also accounting for material dispersion. Finally, the equation to
be satisfied by an event horizon is also displayed and briefly discussed.Comment: 14 pages, 7 figure
Reply to Comment on: Hawking radiation from ultrashort laser pulse filaments
A comment by R. Schutzhold et al. raises possible concerns and questions
regarding recent measurements of analogue Hawking radiation. We briefly reply
to the opinions expressed in the comment and sustain that the origin of the
radiation may be understood in terms of Hawking emission
Quantum Effects for the Dirac Field in Reissner-Nordstrom-AdS Black Hole Background
The behavior of a charged massive Dirac field on a Reissner-Nordstrom-AdS
black hole background is investigated. The essential self-adjointness of the
Dirac Hamiltonian is studied. Then, an analysis of the discharge problem is
carried out in analogy with the standard Reissner-Nordstrom black hole case.Comment: 18 pages, 5 figures, Iop styl
Emission of correlated photon pairs from superluminal perturbations in dispersive media
We develop a perturbative theory that describes a superluminal refractive
perturbation propagating in a dispersive medium and the subsequent excitation
of the quantum vacuum zero-point fluctuations. We find a process similar to the
anomalous Doppler effect: photons are emitted in correlated pairs and mainly
within a Cerenkov-like cone, one on the forward and the other in backward
directions. The number of photon pairs emitted from the perturbation increases
strongly with the degree of superluminality and under realizable experimental
conditions, it can reach up to ~0.01 photons per pulse. Moreover, it is in
principle possible to engineer the host medium so as to modify the effective
group refractive index. In the presence of "fast light" media, e.g. a with
group index smaller than unity, a further ~10x enhancement may be achieved and
the photon emission spectrum is characterized by two sharp peaks that, in
future experiments would clearly identify the correlated emission of photon
pairs.Comment: 9 pages, 7 figure
Divergences problem in black hole brick-wall model
In this work we review, in the framework of the so-called brick wall model,
the divergence problem arising in the one loop calculations of various
thermodynamical quantities, like entropy, internal energy and heat capacity.
Particularly we find that, if one imposes that entanglement entropy is equal to
the Bekenstein-Hawking one, the model gives problematic results. Then a
proposal of solution to the divergence problem is made following the zeroth law
of black hole mechanics.Comment: 19 pages, reviseted-extended version accepted by Phys. Rev.
Notes on the Third Law of Thermodynamics.I
We analyze some aspects of the third law of thermodynamics. We first review
both the entropic version (N) and the unattainability version (U) and the
relation occurring between them. Then, we heuristically interpret (N) as a
continuity boundary condition for thermodynamics at the boundary T=0 of the
thermodynamic domain. On a rigorous mathematical footing, we discuss the third
law both in Carath\'eodory's approach and in Gibbs' one. Carath\'eodory's
approach is fundamental in order to understand the nature of the surface T=0.
In fact, in this approach, under suitable mathematical conditions, T=0 appears
as a leaf of the foliation of the thermodynamic manifold associated with the
non-singular integrable Pfaffian form . Being a leaf, it cannot
intersect any other leaf const. of the foliation. We show that (N) is
equivalent to the requirement that T=0 is a leaf. In Gibbs' approach, the
peculiar nature of T=0 appears to be less evident because the existence of the
entropy is a postulate; nevertheless, it is still possible to conclude that the
lowest value of the entropy has to belong to the boundary of the convex set
where the function is defined.Comment: 29 pages, 2 figures; RevTex fil
Hawking Radiation Entropy and Horizon Divergences
We review the problem of divergences in one--loop thermodynamical quantities
for matter fields in thermal equilibrium on a black hole background. We discuss
a number of results obtained for various thermodynamical quantities. Then we
discuss the ansatz called ``literal interpretation" of zeroth law of black hole
mechanics and try to explain the diseases of the conical defect procedure in
light of this ansatz. Finally, an analysis of the consequences implied by our
ansatz on the calculation of the partition function is made.Comment: 32 pages, uses Phyzz
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