123206943
Hawking Effect with Generalized Uncertainty Principle and Modified Dispersion Relations in de Sitter-Schwarzschild Black Hole
Although the tunneling approach is well established for black hole’s radiation, much works have been done to support the extension of this approach to more general settings. In This letter the Parikh-Kraus-Wilczek tunneling proposal of black hole’s tunneling radiation has been considered. The de Sitter-Schwarzschild black hole’s thermodynamics has been studied based on both, the generalized uncertainty principle and the modified dispersion relations analysis. It is shown that entropy, temperature and the original Parikh-Kraus-Wilczek calculations of the black hole’s tunneling probability receive new corrections. The results of these two alternative approaches are identical if one uses the suitable expansion coefficients.
118388669
Lovelock-Lifshitz black holes
In this paper, we investigate the existence of Lifshitz solutions in Lovelock gravity, both in vacuum and in the presence of a massive vector field. We show that the Lovelock terms can support the Lifshitz solution provided the constants of the theory are suitably chosen. We obtain an exact black hole solution with Lifshitz asymptotics of any scaling parameter z in both Gauss-Bonnet and in pure 3rd order Lovelock gravity. If matter is added in the form of a massive vector field, we also show that Lifshitz solutions in Lovelock gravity exist; these can be regarded as corrections to Einstein gravity coupled to this form of matter. For this form of matter we numerically obtain a broad range of charged black hole solutions with Lifshitz asymptotics, for either sign of the cosmological constant. We find that these asymptotic Lifshitz solutions are more sensitive to corrections induced by Lovelock gravity than are their asymptotic AdS counterparts. We also consider the thermodynamics of the black hole solutions and show that the temperature of large black holes with curved horizons is proportional to r0z where z is the critical exponent; this relationship holds for black branes of any size. As is the case for asymptotic AdS black holes, we find that an extreme black hole exists only for the case of horizons with negative curvature. We also find that these Lovelock-Lifshitz black holes have no unstable phase, in contrast to the Lovelock-AdS case. We also present a class of rotating Lovelock-Lifshitz black holes with Ricci-flat horizons.
120694400
Instanton effects on extracting the nucleon parton distributions
In considering the nucleon parton distributions at low energy values, the non-perturbative effects will have an important role. It is usual to assume for the related vacuum a structure and attribute it a back ground field. It is very like to the situation which we have for Bohm-Aharnov effect when an electron moved in a region where there is not any magnetic field (vacuum). In this case we can attribute to the related vacuum a back ground field which is in fact the gauge field of electrodynamics force. The fluctuations which exist with respect to the concerned vacuum in QCD can appear as instantons and will effect on then nucleon parton distributions especially at low Bjorken-x values. A comparison between the proton structures when we consider the instanton effect with respect to the usual one, indicates the non-perturbative effect on extracting these functions. Considering this effect will yield a better result for the F 2 p structure function.
119241183
Magnetic branes in third order Lovelock-Born-Infeld gravity
Considering both the nonlinear invariant terms constructed by the electromagnetic field and the Riemann tensor in gravity action, we obtain a new class of (n+1)-dimensional magnetic brane solutions in third order Lovelock-Born-Infeld gravity. This class of solutions yields a spacetime with a longitudinal nonlinear magnetic field generated by a static source. These solutions have no curvature singularity and no horizons but have a conic geometry with a deficit angle {delta}. We find that, as the Born-Infeld parameter decreases, which is a measure of the increase of the nonlinearity of the electromagnetic field, the deficit angle increases. We generalize this class of solutions to the case of spinning magnetic solutions and find that, when one or more rotation parameters are nonzero, the brane has a net electric charge which is proportional to the magnitude of the rotation parameters. Finally, we use the counterterm method in third order Lovelock gravity and compute the conserved quantities of these spacetimes. We found that the conserved quantities do not depend on the Born-Infeld parameter, which is evident from the fact that the effects of the nonlinearity of the electromagnetic fields on the boundary at infinity are wiped away. We also find that the properties ofmore » our solution, such as deficit angle, are independent of Lovelock coefficients.« less
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.
122245327
LOVELOCK GRAVITY AND THE COUNTERTERM METHOD
In this paper we, first, generalize the quasilocal definition of the stress energy tensor of Einstein gravity to the case of Lovelock gravity, by introducing the tensorial form of surface terms that make the action well-defined. In order to compute the conserved quantities of the solutions of Lovelock gravity, We introduce the boundary counterterm that removes the divergences of the action with flat boundary at constant t and r.
116202352
Simplifying the algebra of first class constraints, SO(3) as an example
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.
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.