33,232 research outputs found
Quantisation of second class systems in the Batalin-Tyutin formalism
We review the Batalin-Tyutin approach of quantising second class systems
which consists in enlarging the phase space to convert such systems into first
class. The quantisation of first class systems, it may be mentioned, is already
well founded. We show how the usual analysis of Batalin-Tyutin may be
generalised, particularly if one is dealing with nonabelian theories. In order
to gain a deeper insight into the formalism we have considered two specific
examples of second class theories-- the massive Maxwell theory (Proca model)
and its nonabelian extension. The first class constraints and the involutive
Hamiltonian are explicitly constructed. The connection of our Hamiltonian
approach with the usual Lagrangian formalism is elucidated. For the Proca model
we reveal the importance of a boundary term which plays a significant role in
establishing an exact identification of the extra fields in the Batalin-Tyutin
approach with the St\"uckelberg scalar. Some comments are also made concerning
the corresponding identification in the nonabelian example.Comment: 26 pages, Latex file, e-mail [email protected] SINP-TNP/94-
Self dual models and mass generation in planar field theory
We analyse in three space-time dimensions, the connection between abelian
self dual vector doublets and their counterparts containing both an explicit
mass and a topological mass. Their correspondence is established in the
lagrangian formalism using an operator approach as well as a path integral
approach. A canonical hamiltonian analysis is presented, which also shows the
equivalence with the lagrangian formalism. The implications of our results for
bosonisation in three dimensions are discussed.Comment: 15 pages,Revtex, No figures; several changes; revised version to
appear in Physical Review
Entropy of the Kerr-Sen Black Hole
We study the entropy of Kerr-Sen black hole of heterotic string theory beyond
semiclassical approximations. Applying the properties of exact differentials
for three variables to the first law thermodynamics we derive the corrections
to the entropy of the black hole. The leading (logarithmic) and non leading
corrections to the area law are obtained.Comment: 8 pages. Corrected references
Spherical collapse with heat flow and without horizon
We present a class of solutions for a heat conducting fluid sphere, which
radiates energy during collapse without the appearance of horizon at the
boundary at any stage of the collapse. A simple model shows that there is no
accumulation of energy due to collapse since it radiates out at the same rate
as it is being generated.Comment: RevTeX, 3 page
Characterization of quantum dynamics using quantum error correction
Characterizing noisy quantum processes is important to quantum computation
and communication (QCC), since quantum systems are generally open. To date, all
methods of characterization of quantum dynamics (CQD), typically implemented by
quantum process tomography, are \textit{off-line}, i.e., QCC and CQD are not
concurrent, as they require distinct state preparations. Here we introduce a
method, "quantum error correction based characterization of dynamics", in which
the initial state is any element from the code space of a quantum error
correcting code that can protect the state from arbitrary errors acting on the
subsystem subjected to the unknown dynamics. The statistics of stabilizer
measurements, with possible unitary pre-processing operations, are used to
characterize the noise, while the observed syndrome can be used to correct the
noisy state. Our method requires at most configurations to
characterize arbitrary noise acting on qubits.Comment: 7 pages, 2 figures; close to the published versio
Turbulence and its effect on protostellar disk formation
We analyse simulations of turbulent, magnetised molecular cloud cores
focussing on the formation of Class 0 stage protostellar discs and the physical
conditions in their surroundings. We show that for a wide range of initial
conditions Keplerian discs are formed in the Class 0 stage already.
Furthermore, we show that the accretion of mass and angular momentum in the
surroundings of protostellar discs occurs in a highly anisotropic manner, by
means of a few narrow accretion channels. The magnetic field structure in the
vicinity of the discs is highly disordered, revealing field reversals up to
distances of 1000 AU. These findings demonstrate that as soon as even mild
turbulent motions are included, the classical disc formation scenario of a
coherently rotating environment and a well-ordered magnetic field breaks down.Comment: Invited contribution to the NIC proceedings 2016 for the John von
Neumann-Institut f\"ur Computing (NIC) Symposium 201
Quantum Tunneling, Blackbody Spectrum and Non-Logarithmic Entropy Correction for Lovelock Black Holes
We show, using the tunneling method, that Lovelock black holes Hawking
radiate with a perfect blackbody spectrum. This is a new result. Within the
semiclassical (WKB) approximation the temperature of the spectrum is given by
the semiclassical Hawking temperature. Beyond the semiclassical approximation
the thermal nature of the spectrum does not change but the temperature
undergoes some higher order corrections. This is true for both black hole
(event) and cosmological horizons. Using the first law of thermodynamics the
black hole entropy is calculated. Specifically the -dimensional static,
chargeless black hole solutions which are spherically symmetric and
asymptotically flat, AdS or dS are considered. The interesting property of
these black holes is that their semiclassical entropy does not obey the
Bekenstein-Hawking area law. It is found that the leading correction to the
semiclassical entropy for these black holes is not logarithmic and next to
leading correction is also not inverse of horizon area. This is in contrast to
the black holes in Einstein gravity. The modified result is due to the presence
of Gauss-Bonnet term in the Lovelock Lagrangian. For the limit where the
coupling constant of the Gauss-Bonnet term vanishes one recovers the known
correctional terms as expected in Einstein gravity. Finally we relate the
coefficient of the leading (non-logarithmic) correction with the trace anomaly
of the stress tensor.Comment: minor modifications, two new references added, LaTeX, JHEP style, 34
pages, no figures, to appear in JHE
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