A. Yu. Petrov

f(R)-Brane

We investigate the existence of brane solutions in braneworld scenarios described by real scalar field in the presence of modified f(R) gravity with a single extra dimension. In the case of constant curvature, we obtain first-order differential equations which solve the equations of motion and ease the search for explicit analytical solutions. Several examples of current interest are investigated to illustrate the results of the present work.

Aetherlike Lorentz-breaking actions

We show that CPT-even aetherlike Lorentz-breaking actions, for the scalar and electromagnetic fields, are generated via their appropriate Lorentz-breaking coupling to spinor fields, in three, four, and five space-time dimensions. Besides, we also show that aetherlike terms for the spinor field can be generated as a consequence of the same couplings. We discuss the dispersion relations in the theories with aetherlike Lorentz-breaking terms and find the tree-level effective (Breit) potential for fermion scattering and the one-loop effective potential corresponding to the action of the scalar field.

Braneworld solutions for F(R) models with non-constant curvature

Abstract This work deals with braneworld scenarios with generalized gravity. We investigate models where the potential of the scalar field is polynomial or nonpolynomial. We obtain exact and approximated solutions for the scalar field, warp factor and energy density, in the complex scenario with no restriction on the scalar curvature. In particular, we describe the case where the brane may split, engendering internal structure, with the splitting caused by the same parameter that controls deviation from standard gravity.

Perturbative aspects and conformal solutions of F(R) gravity

Abstract We investigate perturbative aspects of gravity with a general F ( R ) Lagrangian, as well as nonperturbative dilatonic solutions. For the first part, we are interested in stability and the definition of asymptotic charges. The main result of this study is that, while generic F ( R ) theories are stable under metric perturbations, they are expected to show instabilities against curvature perturbations when the Lagrangian includes 1 / R terms. For the second part, one is interested on exact solutions, and we explicitly construct kink-like solutions of the Liouville type for the dilaton field for F ( R ) having the form R + γ R n , in two and in four dimensions.

Lorentz violation in the linearized gravity

Abstract We study some physical consequences of the introduction of a Lorentz-violating modification term in the linearized gravity, which leads to modified dispersion relations for gravitational waves in the vacuum. We discuss two possible mechanisms for the induction of such a term in the Lagrangian. First, it is generated at the quantum level by a Lorentz-breaking coupling of the gravity field to a spinor field. Second, it appears as consequence of a particular modification of the Poisson algebra of the canonical variables, in the spirit of the so-called “noncommutative fields approach”.

Four-dimensional aether-like Lorentz-breaking QED revisited and problem of ambiguities

In this paper, we consider the perturbative generation of the CPT-even aether-like Lorentz-breaking term in the extended Lorentz-breaking QED within different approaches and discuss its ambiguities.

Induction of the four-dimensional Lorentz-breaking non-Abelian Chern-Simons action

A four-dimensional Lorentz-breaking non-Abelian Chern-Simons-like action is generated as a one-loop perturbative correction via an appropriate Lorentz-breaking coupling of the non-Abelian gauge field to a spinor field. This term is shown to be regularization dependent, but nevertheless it can be found unambiguously in different regularization schemes at zero and at finite temperature.

Three-dimensional nonanticommutative superspace

We propose two alternative formulations for a three-dimensional nonanticommutative superspace in which some of the fermionic coordinates obey Clifford anticommutation relations. For this superspace, we construct the supersymmetry generators satisfying standard anticommutation relations and the corresponding supercovariant derivatives. We formulate a scalar superfield theory in such a superspace and calculate its propagator. We also suggest a prescription for the introduction of interactions in such theories.

On the higher-derivative supersymmetric gauge theory

We study the one-loop low-energy effective action for the higher-derivative superfield gauge theory coupled to chiral matter.

Gödel solution in modified gravity

We consider the modified gravity whose action represents itself as a sum of the usual Einstein-Hilbert action and the gravitational Chern-Simons term and show that the Godel metric solves the modified equations of motion, thus proving that the closed timelike curves whose presence is characteristic for the Godel solution are not forbidden in the case of the Chern-Simons modified gravity as well.