Pavlos Pasipoularides

Schwinger-Dyson approach for a Lifshitz-type Yukawa model

We consider a

Black hole solutions in 5D Horava-Lifshitz gravity

3+1

Graviton localization and Newton's law for brane models with a nonminimally coupled bulk scalar field

dimensional field theory at a Lifshitz point for a dynamical critical exponent

Spherically symmetric solutions in Covariant Horava-Lifshitz Gravity

z=3

Black hole solutions in Horava-Lifshitz Gravity with cubic terms

, with a scalar and a fermion field coupled via a Yukawa interaction. Using the nonperturbative Schwinger-Dyson approach we calculate quantum corrections to the effective action. We demonstrate that a first order derivative kinetic term as well as a mass term for the fermion arise dynamically. This signals the restoration of Lorentz symmetry in the IR regime of the single fermion model, although for theories with more than one fermionic species such a conclusion will require fine-tuning of couplings. The limitations of the model and our approach are discussed.

Second Randall-Sundrum brane world scenario with a nonminimally coupled bulk scalar field

We study the full spectrum of spherically symmetric solutions in the five-dimensional nonprojectable 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{sub 5}, dS{sub 5}, or flat large distance asymptotic behavior, plus the standard 1/r{sup 2} tail of the usual five-dimensional Schwarzschild black holes. In addition we have found solutions with an unconventional short or large distance behavior, and, for a special range of the coupling parameters, solutions which coincide with black hole solutions of conventional relativistic five-dimensional Gauss-Bonnet gravity.

Gauss-bonnet gravity, brane world models, and nonminimal coupling

Brane world models with a nonminimally coupled bulk scalar field have been studied recently. In this paper we consider metric fluctuations around an arbitrary gravity-scalar background solution, and we show that the corresponding spectrum includes a localized zero mode which strongly depends on the profile of the background scalar field. For a special class of solutions, with a warp factor of the RS form, we solve the linearized Einstein equations, for a pointlike mass source on the brane, by using the brane bending formalism. We see that general relativity on the brane is recovered only if we impose restrictions on the parameter space of the models under consideration.

Asymmetrically warped brane models, bulk photons and Lorentz invariance

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 [P. Horava and C. M. Melby-Thompson, Phys. Rev. D 82, 064027 (2010).], 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.

Neutrino oscillations in a stochastic model for space-time foam

We study four-dimensional nonprojectable 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.

Fermion-induced effective action in the presence of a static inhomogeneous magnetic field

In our previous work of [K. Farakos and P. Pasipoularides, Phys. Lett. B 621, 224 (2005).] we studied the stability of the RS2 model with a nonminimally coupled bulk scalar field