7428020
The reduced phase space of an open string in the background B-field
The problem of an open string in background B-field is discussed. Using the discretized model in details we show that the system is influenced by an infinite number of second class constraints. We interpret the allowed Fourier modes as the coordinates of the reduced phase space. This enables us to compute the Dirac brackets more easily. We prove that the coordinates of the string are non-commutative at the boundaries. We argue that in order to find the Dirac bracket or commutator algebra of the physical variables, one should not expand the fields in terms of the solutions of the equations of motion. Instead, one should impose a set of constraints in suitable coordinates.
11749680
The Decay of singlet scalar dark matter to unparticle and photon
We consider the unparticle physics introduced by Georgi and show that if the standard model is extended to include a singlet scalar as a dark matter candidate, there is a channel which leads to its decay to photon and unparticle. We calculate the decay rate for this new channel and find a lower bound on unparticle physics scale by demanding the stability of this candidate of the dark matter.
1539587
Noncommutative Geometry and Classical Orbits of Particles in a Central Force Potential
We investigate the effect of the noncommutative geometry on the classical orbits of particles in a central force potential The relation is implemented through the modified commutation relations [xi,xj] = iθij. Comparison with observations places severe constraints on the value of the noncommutativity parameter.
20060893
Thermodynamics of rotating solutions in Gauss-Bonnet-Maxwell gravity and the counterterm method
By a suitable transformation, we present the (n+1)-dimensional charged rotating solutions of Gauss-Bonnet gravity with a complete set of allowed rotation parameters which are real in the whole spacetime. We show that these charged rotating solutions present black hole solutions with two inner and outer event horizons, extreme black holes, or naked singularities provided the parameters of the solutions are chosen suitable. Using the surface terms that make the action well defined for Gauss-Bonnet gravity and the counterterm method for eliminating the divergences in action, we compute finite action of the solutions. We compute the conserved and thermodynamical quantities through the use of free energy and the counterterm method, and find that the two methods give the same results. We also find that these quantities satisfy the first law of thermodynamics. Finally, we perform a stability analysis by computing the heat capacity and the determinant of Hessian matrix of mass with respect to its thermodynamic variables in both the canonical and the grand-canonical ensembles, and show that the system is thermally stable. This is commensurate with the fact that there is no Hawking-Page phase transition for black objects with zero curvature horizon.
119235903
Charged Lifshitz Black Holes
We investigate modifications of the Lifshitz black hole solutions due to the presence of Maxwell charge in higher dimensions for arbitrary $z$ and any topology. We find that the behaviour of large black holes is insensitive to the topology of the solutions, whereas for small black holes significant differences emerge. We generalize a relation previously obtained for neutral Lifshitz black branes, and study more generally the thermodynamic relationship between energy, entropy, and chemical potential. We also consider the effect of Maxwell charge on the effective potential between objects in the dual theory.
118662709
TOPOLOGICAL BLACK HOLES OF (n+1)-DIMENSIONAL EINSTEIN YANG MILLS GRAVITY
We present the topological solutions of Einstein gravity in the presence of a non-Abelian Yang–Mills field. In (n+1) dimensions, we consider the SO(n(n-1)/2-1, 1) semisimple group as the Yang–Mills gauge group, and introduce the black hole solutions with hyperbolic horizon. We argue that the four-dimensional solution is exactly the same as the four-dimensional solution of Einstein–Maxwell gravity, while the higher-dimensional solutions are new. We investigate the properties of the higher-dimensional solutions and find that these solutions in five dimensions have the same properties as the topological five-dimensional solution of Einstein–Maxwell (EM) theory although the metric function in five dimensions is different. But in six and higher dimensions, the topological solutions of EYM and EM gravities with non-negative mass have different properties. First, the singularity of EYM solution does not present a naked singularity and is spacelike, while the singularity of topological Reissner–Nordstrom solution is timelike. Second, there are no extreme six or higher-dimensional black holes in EYM gravity with non-negative mass, while these kinds of solutions exist in EM gravity. Furthermore, EYM theory has no static asymptotically de Sitter solution with non-negative mass, while EM gravity has.
120170973
Tunneling black hole radiation, generalized uncertainty principle and de Sitter–Schwarzschild black hole
Abstract The Parikh–Wilczek tunneling proposal of black hole radiation is considered in de Sitter–Schwarzschild space–time. The semi-classical black hole tunneling radiation is calculated under a minimal length uncertainty analysis. It is shown that the original calculation of Parikh–Wilczek receives a new correction.