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.
120841424
EVALUATION OF THE GRAVITON TWO-POINT FUNCTION IN DE SITTER SPACE
After a brief review of the linearized gravity in de Sitter (dS) four-dimensional space and ambient flat five-dimensional notations, the linearized field equation is written in terms of the Casimir operators of dS group. It is shown that the field equation is gauge invariant under some special gauge transformations. Because of this gauge freedom, a gauge-fixing parameter c is inserted in the field equation. It is shown that the solution to the field equation can be written as the multiplication of a generalized symmetric rank-2 polarization tensor and a massless minimally coupled scalar field in ambient space notations. The graviton two-point function has been thoroughly calculated, which is dS-invariant and free of any divergences. This two-point function has been expressed in terms of the intrinsic dS coordinates, from its ambient space counterpart, which is clearly dS-invariant and free of any divergences again.
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.
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.
118643347
Thermodynamics of Rotating Lovelock-Lifshitz Black Branes
We investigate the thermodynamics of rotating Lovelock-Lifshitz black branes. We calculate the conserved and thermodynamic quantities of the solutions and obtain a relation between temperature, angular velocity, energy density, entropy density and angular momentum density. We, also, obtain a Smarr-type formula for the energy density as a function of entropy and angular momentum densities, and show that the thermodynamic quantities calculated in this paper satisfy the first law of thermodynamics. Finally, we investigate the stability of black brane solutions in both canonical and grand-canonical ensemble. We find that the solutions are thermally stable for the solutions with $z\leq n-1$, while they can be unstable for $z>n-1$.
119231146
Asymptotically Flat Radiating Solutions in Third Order Lovelock Gravity
In this paper, we present an exact spherically symmetric solution of third order Lovelock gravity in n dimensions which describes the gravitational collapse of a null dust fluid. This solution is asymptotically (anti-)de Sitter or flat depending on the choice of the cosmological constant. Using the asymptotically flat solution for n{>=}7 with a power-law form of the mass as a function of the null coordinate, we present a model for a gravitational collapse in which a null dust fluid radially injects into an initially flat and empty region. It is found that a naked singularity is inevitably formed whose strength is different for the n=7 and n{>=}8 cases. In the n=7 case, the limiting focusing condition for the strength of curvature singularity is satisfied. But for n{>=}8, the strength of curvature singularity depends on the rate of increase of mass of the spacetime. These considerations show that the third order Lovelock term weakens the strength of the curvature singularity.
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.
116202352
Simplifying the algebra of first class constraints, SO(3) as an example
118016384
Constraint structure and Hamiltonian treatment of Nappi-Witten model
We investigate the Hamiltonian analysis of Nappi-Witten model (WZW action based on non semi simple gauge group) and find a time dependent non-commutativity by canonical quantization. Our procedure is based on constraint analysis of the model in two parts. A first class analysis is used for gauge fixing the original model following by a second class analysis in which the boundary condition are treated as Dirac constraints. We find the reduced phase space by imposing our second class constraints on the variables in an extended Fourier space.