11,215 research outputs found
Classification of Quantum Cellular Automata
There exists an index theory to classify strictly local quantum cellular
automata in one dimension. We consider two classification questions. First, we
study to what extent this index theory can be applied in higher dimensions via
dimensional reduction, finding a classification by the first homology group of
the manifold modulo torsion. Second, in two dimensions, we show that an
extension of this index theory (including torsion) fully classifies quantum
cellular automata, at least in the absence of fermionic degrees of freedom.
This complete classification in one and two dimensions by index theory is not
expected to extend to higher dimensions due to recent evidence of a nontrivial
automaton in three dimensions. Finally, we discuss some group theoretical
aspects of the classification of quantum cellular automata and consider these
automata on higher dimensional real projective spaces.Comment: 53 pages, 15 figures; v2: minor corrections, final version in pres
Comparative Planetary Atmospheres: Models of TrES-1 and HD209458b
We present new self-consistent atmosphere models for transiting planets
TrES-1 and HD209458b. The planets were recently observed with the Spitzer Space
Telescope in bands centered on 4.5 and 8.0 m, for TrES-1, and 24 m,
for HD209458b. We find that standard solar metallicity models fit the
observations for HD209458b. For TrES-1, which has an T_eff ~300 K cooler, we
find that models with a metallicity 3-5 times enhanced over solar abundances
can match the 1 error bar at 4.5 m and 2 at 8.0m.
Models with solar abundances that included energy deposition into the
stratosphere give fluxes that fall within the 2 error bars in both
bands. The best-fit models for both planets assume that reradiation of absorbed
stellar flux occurs over the entire planet. For all models of both planets we
predict planet/star flux ratios in other Spitzer bandpasses.Comment: Accepted to the Astrophysical Journal Letters, May 17, 200
Entanglement of Sections, Examples Looking for a Theory
Quantum information is about the entanglement of states. To this starting
point we add parameters whereby a single state becomes a non-vanishing section
of a bundle. We consider through examples the possible entanglement patterns of
sections.Comment: 15 pages, 0 figure
27/32
We show that when an N=2 SCFT flows to an N=1 SCFT via giving a mass to the
adjoint chiral superfield in a vector multiplet with marginal coupling, the
central charges a and c of the N=2 theory are related to those of the N=1
theory by a universal linear transformation. In the large N limit, this
relationship implies that the central charges obey a_IR/a_UV=c_IR/c_UV=27/32.
This gives a physical explanation to many examples of this number found in the
literature, and also suggests the existence of a flow between some theories not
previously thought to be connected.Comment: 3 pages. v2: references added, minor typos correcte
Born-Infeld Type Extension of (Non-)Critical Gravity
We consider the Born-Infeld type extension of (non-)critical gravity which is
higher curvature gravity on Anti de-Sitter space with specific combinations of
scalar curvature and Ricci tensor. This theory may also be viewed as a natural
extension of three-dimensional Born-Infeld new massive gravity to arbitrary
dimensions. We show that this extension is consistent with holographic
-theorem and scalar graviton modes are absent in this theory. After showing
that ghost modes in the theory can be truncated consistently by appropriate
boundary conditions, we argue that the theory is classically equivalent to
Einstein gravity at the non-linear level. Black hole solutions are discussed in
the view point of the full non-linear classical equivalence between the theory
and Einstein gravity. Holographic entanglement entropy in the theory is also
briefly commented on.Comment: 1+13 pages, improvements in presentation, references added, accepted
to PR
Anti-de Sitter Supersymmetry
We give a pedagogical introduction to certain aspects of supersymmetric field
theories in anti-de Sitter space. Among them are the presence of masslike terms
in massless wave equations, irreducible unitary representations and the
phenomenon of multiplet shortening.Comment: Lectures presented by B. de Wit at the Winter School of Theoretical
Physics, Polanica, Poland, February 1999. 23 pp., LateX file, requires
packages latexsym, amsfonts, cl2emult.cl
Holographic Dual of BCFT
We propose a holographic dual of a conformal field theory defined on a
manifold with boundaries, i.e. boundary conformal field theory (BCFT). Our new
holography, which may be called AdS/BCFT, successfully calculates the boundary
entropy or g-function in two dimensional BCFTs and it agrees with the finite
part of the holographic entanglement entropy. Moreover, we can naturally derive
a holographic g-theorem. We also analyze the holographic dual of an interval at
finite temperature and show that there is a first order phase transition.Comment: 5 pages, 3 figs, a reference added, typos corrected, to be published
in PR
Can the Tajmar effect be explained using a modification of inertia?
The Tajmar effect is an unexplained acceleration observed by accelerometers
and laser gyroscopes close to rotating supercooled rings. The observed ratio
between the gyroscope and ring accelerations was 3+/-1.2x10^-8. Here, a new
model for inertia which has been tested quite successfully on the Pioneer and
flyby anomalies is applied to this problem. The model assumes that the inertia
of the gyroscope is caused by Unruh radiation that appears as the ring and the
fixed stars accelerate relative to it, and that this radiation is subject to a
Hubble-scale Casimir effect. The model predicts that the sudden acceleration of
the nearby ring causes a slight increase in the inertial mass of the gyroscope,
and, to conserve momentum in the reference frame of the spinning Earth, the
gyroscope rotates clockwise with an acceleration ratio of 1.8+/-0.25x10^-8 in
agreement with the observed ratio. However, this model does not explain the
parity violation seen in some of the gyroscope data. To test these ideas the
Tajmar experiment (setup B) could be exactly reproduced in the southern
hemisphere, since the model predicts that the anomalous acceleration should
then be anticlockwise.Comment: 9 pages, 1 figure. Accepted by EPL on the 4th December, 200
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