207 research outputs found
Entropy bounds for charged and rotating systems
It was shown in a previous work that, for systems in which the entropy is an
extensive function of the energy and volume, the Bekenstein and the holographic
entropy bounds predict new results. In this paper, we go further and derive
improved upper bounds to the entropy of {\it extensive} charged and rotating
systems. Furthermore, it is shown that for charged and rotating systems
(including non-extensive ones), the total energy that appear in both the
Bekenstein entropy bound (BEB) and the causal entropy bound (CEB) can be
replaced by the {\it internal} energy of the system. In addition, we propose
possible corrections to the BEB and the CEB.Comment: 12 pages, revte
Thermal Fluctuations and Black Hole Entropy
In this paper, we consider the effect of thermal fluctuations on the entropy
of both neutral and charged black holes. We emphasize the distinction between
fixed and fluctuating charge systems; using a canonical ensemble to describe
the former and a grand canonical ensemble to study the latter. Our novel
approach is based on the philosophy that the black hole quantum spectrum is an
essential component in any such calculation. For definiteness, we employ a
uniformly spaced area spectrum, which has been advocated by Bekenstein and
others in the literature. The generic results are applied to some specific
models; in particular, various limiting cases of an (arbitrary-dimensional)
AdS-Reissner-Nordstrom black hole. We find that the leading-order quantum
correction to the entropy can consistently be expressed as the logarithm of the
classical quantity. For a small AdS curvature parameter and zero net charge, it
is shown that, independent of the dimension, the logarithmic prefactor is +1/2
when the charge is fixed but +1 when the charge is fluctuating.We also
demonstrate that, in the grand canonical framework, the fluctuations in the
charge are large, , even when .
A further implication of this framework is that an asymptotically flat,
non-extremal black hole can never achieve a state of thermal equilibrium.Comment: 25 pages, Revtex; references added and corrected, and some minor
change
Area spectra of the rotating BTZ black hole from quasinormal modes
Following Bekenstein's suggestion that the horizon area of a black hole
should be quantized, the discrete spectrum of the horizon area has been
investigated in various ways. By considering the quasinormal mode of a black
hole, we obtain the transition frequency of the black hole, analogous to the
case of a hydrogen atom, in the semiclassical limit. According to Bohr's
correspondence principle, this transition frequency at large quantum number is
equal to classical oscillation frequency. For the corresponding classical
system of periodic motion with this oscillation frequency, an action variable
is identified and quantized via Bohr-Sommerfeld quantization, from which the
quantized spectrum of the horizon area is obtained. This method can be applied
for black holes with discrete quasinormal modes. As an example, we apply the
method for the both non-rotating and rotating BTZ black holes and obtain that
the spectrum of the horizon area is equally spaced and independent of the
cosmological constant for both cases
A comment on black hole entropy or does Nature abhor a logarithm?
There has been substantial interest, as of late, in the quantum-corrected
form of the Bekenstein-Hawking black hole entropy. The consensus viewpoint is
that the leading-order correction should be a logarithm of the horizon area;
however, the value of the logarithmic prefactor remains a point of notable
controversy. Very recently, Hod has employed statistical arguments that
constrain this prefactor to be a non-negative integer. In the current paper, we
invoke some independent considerations to argue that the "best guess" for the
prefactor might simply be zero. Significantly, this value complies with the
prior prediction and, moreover, seems suggestive of some fundamental symmetry.Comment: 10 pages and Revtex; (v2) imperative title change and added one
reference; (v3) minor content and style changes throughout; 7 new citations;
(v4) 8 new citations, an addendum and other minor changes; (v5) yet more
references, some points clarified, and a recent criticism is addressed
(addendum 2
Spectrum of rotating black holes and its implications for Hawking radiation
The reduced phase space formalism for quantising black holes has recently
been extended to find the area and angular momentum spectra of four dimensional
Kerr black holes. We extend this further to rotating black holes in all
spacetime dimensions and show that although as in four dimensions the spectrum
is discrete, it is not equispaced in general. As a result, Hawking radiation
spectra from these black holes are continuous, as opposed to the discrete
spectrum predicted for four dimensional black holes.Comment: 11 pages, Revtex4. Minor changes to match version to appear in Class.
Quant. Gra
Universal canonical entropy for gravitating systems
The thermodynamics of general relativistic systems with boundary, obeying a
Hamiltonian constraint in the bulk, is argued to be determined solely by the
boundary quantum dynamics, and hence by the area spectrum. Assuming, for large
area of the boundary, (a) an area spectrum as determined by Non-perturbative
Canonical Quantum General Relativity (NCQGR), (b) an energy spectrum that bears
a power law relation to the area spectrum, (c) an area law for the leading
order microcanonicai entropy, leading thermal fluctuation corrections to the
canonical entropy are shown to be logarithmic in area with a universal
coefficient. Since the microcanonical entropy also has univeral logarithmic
corrections to the area law (from quantum spacetime fluctuations, as found
earlier) the canonical entropy then has a universal form including logarithmic
corrections to the area law. This form is shown to be independent of the index
appearing in assumption (b). The index, however, is crucial in ascertaining the
domain of validity of our approach based on thermal equilibrium.Comment: 6 pages revtex, one eps figure; based on talk delivered at the
International Conference on Gravitation and Cosmology held at Kochi, India
during 5-9 January, 200
The resource theory of quantum reference frames: manipulations and monotones
Every restriction on quantum operations defines a resource theory,
determining how quantum states that cannot be prepared under the restriction
may be manipulated and used to circumvent the restriction. A superselection
rule is a restriction that arises through the lack of a classical reference
frame and the states that circumvent it (the resource) are quantum reference
frames. We consider the resource theories that arise from three types of
superselection rule, associated respectively with lacking: (i) a phase
reference, (ii) a frame for chirality, and (iii) a frame for spatial
orientation. Focussing on pure unipartite quantum states (and in some cases
restricting our attention even further to subsets of these), we explore
single-copy and asymptotic manipulations. In particular, we identify the
necessary and sufficient conditions for a deterministic transformation between
two resource states to be possible and, when these conditions are not met, the
maximum probability with which the transformation can be achieved. We also
determine when a particular transformation can be achieved reversibly in the
limit of arbitrarily many copies and find the maximum rate of conversion. A
comparison of the three resource theories demonstrates that the extent to which
resources can be interconverted decreases as the strength of the restriction
increases. Along the way, we introduce several measures of frameness and prove
that these are monotonically nonincreasing under various classes of operations
that are permitted by the superselection rule.Comment: 37 pages, 4 figures, Published Versio
Ab initio coupled-cluster and configuration interaction calculations for 16-O using V_UCOM
Using the ground-state energy of 16-O obtained with the realistic V_UCOM
interaction as a test case, we present a comprehensive comparison of different
configuration interaction (CI) and coupled-cluster (CC) methods, analyzing the
intrinsic advantages and limitations of each of the approaches. In particular,
we use the importance-truncated (IT) CI and no-core shell model (NCSM) schemes
with up to 4-particle-4-hole (4p4h) excitations as well as the size extensive
CC methods with a complete treatment of one- and two-body clusters (CCSD) and a
non-iterative treatment of connected three-body clusters via the completely
renormalized correction to the CCSD energy defining the CR-CC(2,3) approach. We
discuss the impact of the center-of-mass contaminations, the choice of the
single-particle basis, and size-extensivity on the resulting energies. When the
IT-CI and IT-NCSM methods include the 4p4h excitations and when the CC
calculations include the 1p1h, 2p2h, and 3p3h clusters, as in the CR-CC(2,3)
approach, we observe an excellent agreement among the different methodologies.
This shows that despite their individual limitations, the IT-CI, IT-NCSM, and
CC methods can provide precise and consistent ab initio nuclear structure
predictions. Furthermore, the IT-CI, IT-NCSM, and CC ground-state energy values
obtained with 16-O are in good agreement with the experimental value, proving
that the V_UCOM two-body interaction allows for a realistic description of
binding energies for heavier nuclei and that all of the methods used in this
study account for most of the relevant particle correlation effects.Comment: 20 pages, 4 figures, 1 table (v2: extended version in response to
referees' comments
- …