416 research outputs found
Emergent Noncommutative gravity from a consistent deformation of gauge theory
Starting from a standard noncommutative gauge theory and using the
Seiberg-Witten map we propose a new version of a noncommutative gravity. We use
consistent deformation theory starting from a free gauge action and gauging a
killing symmetry of the background metric to construct a deformation of the
gauge theory that we can relate with gravity. The result of this consistent
deformation of the gauge theory is nonpolynomial in A_\mu. From here we can
construct a version of noncommutative gravity that is simpler than previous
attempts. Our proposal is consistent and is not plagued with the problems of
other approaches like twist symmetries or gauging other groups.Comment: 18 pages, references added, typos fixed, some concepts clarified.
Paragraph added below Eq. (77). Match published PRD version
Gauge Symmetry and Consistent Spin-Two Theories
We study Lagrangians with the minimal amount of gauge symmetry required to
propagate spin-two particles without ghosts or tachyons. In general, these
Lagrangians also have a scalar mode in their spectrum. We find that, in two
cases, the symmetry can be enhanced to a larger group: the whole group of
diffeomorphisms or a enhancement involving a Weyl symmetry. We consider the
non-linear completions of these theories. The intuitive completions yield the
usual scalar-tensor theories except for the pure spin-two cases, which
correspond to two inequivalent Lagrangians giving rise to Einstein's equations.
A more constructive self-consistent approach yields a background dependent
Lagrangian.Comment: 7 pages, proceedings of IRGAC'06; typo correcte
Lagrangian generators of the Poincare gauge symmetries
We have systematically computed the generators of the symmetries arising in
Poincare gauge theory formulation of gravity, both in 2+1 and 3+1 dimensions.
This was done using a completely Lagrangian approach. The results are expected
to be valid in any dimensions, as seen through lifting the results of the 2+1
dimensional example into the 3+1 dimensional one.Comment: Latex2e, 15 pages, 1 figure; (v2) Appendix containing discussion on
applications of Lagrangian generators adde
Primordial Fluctuations within Teleparallelism
We study the cosmological perturbations for the possible inflation scenario
in the teleparallel equivalence of general relativity specified with
parallelizable topological conditions. By acquiring the identical physical
observables to general relativity under the teleparallel formalism, we perform
a 3+1 decomposition of the vierbein field, which can be interpreted as the time
gauge fixing between coordinate and tangent frames. We also extend our
discussion to the higher-order action, gravity.Comment: 17 pages, no figure, revised version accepted by PR
Strings, Black Holes, and Quantum Information
We find multiple relations between extremal black holes in string theory and
2- and 3-qubit systems in quantum information theory. We show that the entropy
of the axion-dilaton extremal black hole is related to the concurrence of a
2-qubit state, whereas the entropy of the STU black holes, BPS as well as
non-BPS, is related to the 3-tangle of a 3-qubit state. We relate the 3-qubit
states with the string theory states with some number of D-branes. We identify
a set of "large" black holes with the maximally entangled GHZ-class of states
and "small" black holes with separable, bipartite and W states. We sort out the
relation between 3-qubit states, twistors, octonions, and black holes. We give
a simple expression for the entropy and the area of stretched horizon of
"small'' black holes in terms of a norm and 2-tangles of a 3-qubit system.
Finally, we show that the most general expression for the black hole and black
ring entropy in N=8 supergravity/M-theory, which is given by the famous quartic
Cartan E_{7(7)} invariant, can be reduced to Cayley's hyperdeterminant
describing the 3-tangle of a 3-qubit state.Comment: 31 pages, 10 figures. A version to appear in Physical Revie
An Implementation for Dynamic Application Allocation in Shared Sensor Networks
We present a system architecture implementation to perform dynamic application allocation in shared sensor networks, where highly integrated wireless sensor systems are used to support multiple applications. The architecture is based on a central controller that collects the received data from the sensor nodes, dynamically decides which applications must be simultaneously deployed in each node and, accordingly, over-the-air reprograms the sensor nodes. Waspmote devices are used as sensor nodes that communicate with the controller using ZigBee protocol. Experimental results show the viability of the proposal
Laws of Black Hole Mechanics from Holst Action
The formulation of Weak Isolated Horizons (WIH) based on the Isolated Horizon
formulation of black hole horizons is reconsidered. The first part of the paper
deals with the derivation of laws of mechanics of a WIH. While the zeroth law
follows from the WIH boundary conditions, first law depends on the action
chosen. We construct the covariant phase space for a spacetime having an WIH as
inner boundary for the Holst action. This requires the introduction of new
potential functions so that the symplectic structure is foliation independent.
We show that a precise cancellation among various terms leads to the usual
first law for WIH. Subsequently, we show from the same covariant phase space
that for spherical horizons, the topological theory on the inner boundary is a
U(1) Chern-Simons theory.Comment: References added, Minor Corrections 25 pages 1 fi
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