分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： We applied the transformation optics to mimic a black hole of Schwarzschild form. Similar properties of photon sphere were also found numerically for the metamaterial black hole. Several reduced versions of the black hole systems were proposed for easier implementations.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： We investigate the Hamiltonian formulation of f(T) gravity and find that there are five degrees of freedom. The six first class constraints corresponding to the local Lorentz transformation in Teleparallel gravity become second class constraints in f(T) gravity, which leads to the appearance of three extra degrees offreedom and the violation of the local Lorentz invariance in f(T) gravity. In general, there are D-1 extra degrees of freedom for f(T) gravity in D dimensions, and this implies that the extra degrees of freedom correspond to one massive vector field or one massless vector field with one scalar field.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： We prove that, in general the first law of black hole thermodynamnics, delta Q = T delta S, is violated in f(T) gravity. As a result, it is possible that there exists entropy production, which implies that the black hole thermodynamics can be in non-equilibrium even in the static spacetime. This feature is very different from that of f(R) or that of other higher derivative gravity theories. We find that the violation of first law results from the lack of local Lorentz invariance in f(T) gravity. By investigating two examples, we note that f ''(0) should be negative in order to avoid the naked singularities and superluminal motion of light. When f ''(T) is small, the entropy of black holes in f(T) gravity is approximatively equal to (f'(T))/(4)A
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