16 research outputs found
Spherically symmetric solutions in Covariant Horava-Lifshitz Gravity
We study the most general case of spherically symmetric vacuum solutions in
the framework of the Covariant Horava Lifshitz Gravity, for an action that
includes all possible higher order terms in curvature which are compatible with
power-counting normalizability requirement. We find that solutions can be
separated into two main classes: (i) solutions with nonzero radial shift
function, and (ii) solutions with zero radial shift function. In the case (ii),
spherically symmetric solutions are consistent with observations if we adopt
the view of Horava and Melby-Tomson, according to which the auxiliary field A
can be considered as a part of an effective general relativistic metric, which
is valid only in the IR limit. On the other hand, in the case (i), consistency
with observations implies that the field A should be independent of the
spacetime geometry, as the Newtonian potential arises from the nonzero radial
shift function. Also, our aim in this paper is to discuss and compare these two
alternative but different assumptions for the auxiliary field A.Comment: 29 pages, comments and figure adde
Black hole solutions in Horava-Lifshitz Gravity with cubic terms
We study four dimensional non-projectable Horava-Lifshitz type gravity, in
the case of an action with terms, cubic in curvature. For special choices of
the free parameters of the model, we obtain two new analytic black hole
solutions which exhibit the standard Schwarzschild asymptotic behavior in the
large distance limit. The effect of cubic terms in the short range behavior of
the black hole solutions is discussed.Comment: 25 pages, 3 figures, accepted in Phys. Rev.
Black Hole Solutions in 5D Horava-Lifshitz Gravity
We study the full spectrum of spherically symmetric solutions in the five
dimensional non-projectable Horava-Lifshitz type gravity theories. For
appropriate ranges of the coupling parameters, we have found several classes of
solutions which are characterized by an AdS_5, dS_5 or flat large distance
asymptotic behaviour, plus the standard 1/r^2 tail of the usual
five-dimensional Schwarzschild black holes. In addition we have found solutions
with an unconventional short or large distance behaviour, and for a special
range of the coupling parameters solutions which coincide with black hole
solutions of conventional relativistic five-dimensional Gauss-Bonnet gravity.Comment: 31 pages, 6 figures, references adde
Fermionic Vacuum Energy from a Nielsen-Olesen Vortex
We calculate the vacuum energy of a spinor field in the background of a
Nielsen-Olesen vortex. We use the method of representing the vacuum energy in
terms of the Jost function on the imaginary momentum axis. Renormalization is
carried out using the heat kernel expansion and zeta functional regularization.
With this method well convergent sums and integrals emerge which allow for an
efficient numerical calculation of the vacuum energy in the given case where
the background is not known analytically but only numerically. The vacuum
energy is calculated for several choices of the parameters and it turns out to
give small corrections to the classical energy.Comment: 22 pages, 6 figure
On the Vacuum energy of a Color Magnetic Vortex
We calculate the one loop gluon vacuum energy in the background of a color
magnetic vortex for SU(2) and SU(3). We use zeta functional regularization to
obtain analytic expressions suitable for numerical treatment. The momentum
integration is turned to the imaginary axis and fast converging sums/integrals
are obtained. We investigate numerically a number of profiles of the
background. In each case the vacuum energy turns out to be positive increasing
in this way the complete energy and making the vortex configuration less
stable. In this problem bound states (tachyonic modes) are present for all
investigated profiles making them intrinsically unstable.Comment: 28 pages, 4 figure