171 research outputs found
Deterministic Entanglement of Assistance and Monogamy Constraints
Certain quantum information tasks require entanglement of assistance, namely
a reduction of a tripartite entangled state to a bipartite entangled state via
local measurements. We establish that 'concurrence of assistance' (CoA)
identifies capabilities and limitations to producing pure bipartite entangled
states from pure tripartite entangled states and prove that CoA is an
entanglement monotone for -dimensional pure states.
Moreover, if the CoA for the pure tripartite state is at least as large as the
concurrence of the desired pure bipartite state, then the former may be
transformed to the latter via local operations and classical communication, and
we calculate the maximum probability for this transformation when this
condition is not met.Comment: 5 pages, no figure
Building blocks of a black hole
What is the nature of the energy spectrum of a black hole ? The algebraic
approach to black hole quantization requires the horizon area eigenvalues to be
equally spaced. As stressed long ago by by Mukhanov, such eigenvalues must be
exponentially degenerate with respect to the area quantum number if one is to
understand black hole entropy as reflecting degeneracy of the observable
states. Here we construct the black hole states by means of a pair of "creation
operators" subject to a particular simple algebra, a slight generalization of
that for the harmonic oscillator. We then prove rigorously that the n-th area
eigenvalue is exactly 2 raised to the n-fold degenerate. Thus black hole
entropy qua logarithm of the number of states for fixed horizon area comes out
proportional to that area.Comment: PhysRevTeX, 14 page
Algebraic approach to quantum black holes: logarithmic corrections to black hole entropy
The algebraic approach to black hole quantization requires the horizon area
eigenvalues to be equally spaced. As shown previously, for a neutral
non-rotating black hole, such eigenvalues must be -fold degenerate if
one constructs the black hole stationary states by means of a pair of creation
operators subject to a specific algebra. We show that the algebra of these two
building blocks exhibits symmetry, where the area
operator generates the U(1) symmetry. The three generators of the SU(2)
symmetry represent a {\it global} quantum number (hyperspin) of the black hole,
and we show that this hyperspin must be zero. As a result, the degeneracy of
the -th area eigenvalue is reduced to for large , and
therefore, the logarithmic correction term should be added to the
Bekenstein-Hawking entropy. We also provide a heuristic approach explaining
this result, and an evidence for the existence of {\it two} building blocks.Comment: 15 pages, Revtex, to appear in Phys. Rev.
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
Black hole area quantization
It has been argued by several authors that the quantum mechanical spectrum of
black hole horizon area must be discrete. This has been confirmed in different
formalisms, using different approaches. Here we concentrate on two approaches,
the one involving quantization on a reduced phase space of collective
coordinates of a Black Hole and the algebraic approach of Bekenstein. We show
that for non-rotating, neutral black holes in any spacetime dimension, the
approaches are equivalent. We introduce a primary set of operators sufficient
for expressing the dynamical variables of both, thus mapping the observables in
the two formalisms onto each other. The mapping predicts a Planck size remnant
for the black hole.Comment: 7 pages, uses MPLA style file (included). Revised version with
changes in notation for clarity and consistency. To appear in MPL
Processing of the papain precursor. Purification of the zymogen and characterization of its mechanism of processing.
The precursor of the cysteine protease papain has been expressed and secreted as propapain from insect cells infected with a recombinant baculovirus expressing a synthetic gene coding for prepropapain. This 39-kDa secreted propapain zymogen molecule is glycosylated and can be processed in vitro into an enzymatically active authentic papain molecule of 24.5 kDa (Vernet, T., Tessier, D.C., Richardson, C., Laliberte, F., Khouri, H. E., Bell, A. W., Storer, A. C., and Thomas, D. Y. (1990) J. Biol. Chem. 265, 16661-16666). Recombinant propapain was stabilized with Hg2+ and purified to homogeneity using affinity chromatography, gel filtration, and ion-exchange chromatographic procedures. The maximum rate of processing in vitro was achieved at approximately pH 4.0, at a temperature of 65 degrees C and under reducing conditions. Precursor processing is inhibited by a variety of reversible and irreversible cysteine protease inhibitors but not by specific inhibitors of serine, metallo or acid proteases. Replacement by site-directed mutagenesis of the active site cysteine with a serine at position 25 also prevents processing. The inhibitor 125I-N-(2S,3S)-3-trans-hydroxycarbonyloxiran-2-carbonyl-L-tyrosine benzyl ester covalently labeled the wild type papain precursor, but not the C25S mutant, indicating that the active site is accessible to the inhibitor and is in a native conformation within the precursor. Based on biochemical and kinetic analyses of the activation and processing of propapain we have shown that the papain precursor is capable of autoproteolytic cleavage (intramolecular). Once free papain is released processing can then occur in trans (intermolecular)
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
Hawking Radiation as Tunneling through the Quantum Horizon
Planck-scale corrections to the black-hole radiation spectrum in the
Parikh-Wilczek tunneling framework are calculated. The corrective terms arise
from modifications in the expression of the surface gravity in terms of the
mass-energy of the black hole-emitted particle system. The form of the new
spectrum is discussed together with the possible consequences for the fate of
black holes in the late stages of evaporation.Comment: 13 pages; the contents of this paper overlap somewhat with the
earlier submissions hep-th/0504188 and gr-qc/0505015; (v2) references added
and various cosmetic (but no physics) changes, to appear in JHE
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