156,070 research outputs found
A-branes and Noncommutative Geometry
We argue that for a certain class of symplectic manifolds the category of
A-branes (which includes the Fukaya category as a full subcategory) is
equivalent to a noncommutative deformation of the category of B-branes (which
is equivalent to the derived category of coherent sheaves) on the same
manifold. This equivalence is different from Mirror Symmetry and arises from
the Seiberg-Witten transform which relates gauge theories on commutative and
noncommutative spaces. More generally, we argue that for certain generalized
complex manifolds the category of generalized complex branes is equivalent to a
noncommutative deformation of the derived category of coherent sheaves on the
same manifold. We perform a simple test of our proposal in the case when the
manifold in question is a symplectic torus.Comment: 15 pages, late
Generalized Paxos Made Byzantine (and Less Complex)
One of the most recent members of the Paxos family of protocols is
Generalized Paxos. This variant of Paxos has the characteristic that it departs
from the original specification of consensus, allowing for a weaker safety
condition where different processes can have a different views on a sequence
being agreed upon. However, much like the original Paxos counterpart,
Generalized Paxos does not have a simple implementation. Furthermore, with the
recent practical adoption of Byzantine fault tolerant protocols, it is timely
and important to understand how Generalized Paxos can be implemented in the
Byzantine model. In this paper, we make two main contributions. First, we
provide a description of Generalized Paxos that is easier to understand, based
on a simpler specification and the pseudocode for a solution that can be
readily implemented. Second, we extend the protocol to the Byzantine fault
model
Environmental protection and the generalized system of preferences : a legal and appropriate linkage?
This article will question the legality of measures of environmental ‘conditionality’ in the Generalized System of Preferences [GSP] of the European Community [EC]. The GSP is a GATT/WTO authorized scheme which permits developed nations to grant non-reciprocal tariff preferences in favour of developing countries. The objectives of the GSP are primarily development-oriented in that it aims to increase the export earnings of developing countries, promote their industrialization and accelerate rates of economic growth. A recent case taken in the WTO examined the legal contours of the grant of tariff preferences and it is in the light of this that this article will examine the so-called ‘special incentive arrangements’ of the reformed EC GSP which offers additional tariff preferences to developing countries on the ‘condition’ that they adhere to specified standards of environmental protection
The Legendre Transform in Non-additive Thermodynamics and Complexity
We present an argument which purports to show that the use of the standard
Legendre transform in non-additive Statistical Mechanics is not appropriate.
For concreteness, we use as paradigm, the case of systems which are
conjecturally described by the (non-additive) Tsallis entropy. We point out the
form of the modified Legendre transform that should be used, instead, in the
non-additive thermodynamics induced by the Tsallis entropy. We comment on more
general implications of this proposal for the thermodynamics of "complex
systems".Comment: 23 pages. LaTeX2e. No figure
Quantum Extremal Surfaces: Holographic Entanglement Entropy beyond the Classical Regime
We propose that holographic entanglement entropy can be calculated at
arbitrary orders in the bulk Planck constant using the concept of a "quantum
extremal surface": a surface which extremizes the generalized entropy, i.e. the
sum of area and bulk entanglement entropy. At leading order in bulk quantum
corrections, our proposal agrees with the formula of Faulkner, Lewkowycz, and
Maldacena, which was derived only at this order; beyond leading order
corrections, the two conjectures diverge. Quantum extremal surfaces lie outside
the causal domain of influence of the boundary region as well as its
complement, and in some spacetimes there are barriers preventing them from
entering certain regions. We comment on the implications for bulk
reconstruction.Comment: 28 pages, 6 figures. Version 3: typos fixed, minor changes to
reference
Multi-Trace Operators and the Generalized AdS/CFT Prescription
We show that multi-trace interactions can be consistently incorporated into
an extended AdS/CFT prescription involving the inclusion of generalized
boundary conditions and a modified Legendre transform prescription. We find new
and consistent results by considering a self-contained formulation which
relates the quantization of the bulk theory to the AdS/CFT correspondence and
the perturbation at the boundary by double-trace interactions. We show that
there exist particular double-trace perturbations for which irregular modes are
allowed to propagate as well as the regular ones. We perform a detailed
analysis of many different possible situations, for both minimally and
non-minimally coupled cases. In all situations, we make use of a new constraint
which is found by requiring consistence. In the particular non-minimally
coupled case, the natural extension of the Gibbons-Hawking surface term is
generated.Comment: 27 pages, LaTeX, v.2:minor changes, v.3:comments added, v.4:several
new results, discussions, references and a section of Conclusions added.
Previous results unchanged, v.5: minor changes. Final version to be published
in Phys.Rev.
On the Existence of the Logarithmic Correction Term in Black Hole Entropy-Area Relation
In this paper we consider a model universe with large extra dimensions to
obtain a modified black hole entropy-area relation. We use the generalized
uncertainty principle to find a relation between the number of spacetime
dimensions and the presence or vanishing of logarithmic prefactor in the black
hole entropy-area relation. Our calculations are restricted to the
microcanonical ensembles and we show that in the modified entropy-area
relation, the microcanonical logarithmic prefactor appears only when spacetime
has an even number of dimensions.Comment: 9 Pages, No Figure
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