Note About Non-BPS and BPS Dp-branes in Near Horizon Region of N Dk-Branes

In this paper we will consider the dynamics of BPS and non-BPS Dp-branes in the background of N Dk-branes. Our approach is based on an existence of the new symmetry of D-brane effective actions that naturally emerges in the near horizon region of the stack of N Dk-branes. Since generally this scaling symmetry is explicitly broken in the Lagrangian we will find the equation that determines the time evolution of the generator of this transformations. Then we will argue that in case when the tachyon living on the worldvolume of unstable D-brane reaches the stable minimum the time evolution of this generator can be easily determined. With the help of the knowledge of the time dependence of this charge we will determine the trajectory of the non-BPS D-brane in the near horizon region of N Dk-branes. In case of BPS Dp-brane probe we will aruge that such a broken scaling symmetry exists as well and the existence of the explicit time dependence of the generator of this symmetry can be used in the solving the equation of motion of the probe Dp-brane in the near horizon region of N Dk-branes.Comment: 18 page

Hamiltonian Formalism of General Bimetric Gravity

We perform the Hamiltonian analysis of general bimetric gravity. We determine four first class constraints that are generators of the diagonal diffeomorphism. We further analyze the remaining constraints and we present an evidence that these constraints should be the second class constraints in order to have theory with the Hamiltonian constraint as the first class constraint. We also discuss the case of the non-linear bimetric gravity and argue that it is very difficult to eliminate the ghost mode.Comment: 21 pages, typos correcte

Non-Local Gravity from Hamiltonian Point of View

This short note is devoted to the canonical analysis of the non-local theories of gravity. We find their Hamiltonian and determine the algebra of constraints. We perform this analysis for non-local theories of gravity formulated both in Jordan and Einstein frame. The result of our analysis suggests that Hamiltonian formulation does not bring to clear identification of ghosts presence in non-local gravity.Comment: 14 pages, v1:references adde