Applying the first law of thermodynamics to the apparent horizon of a FriedmannRobertson-Walker universe and assuming the geometric entropy given by a quarter of the apparent horizon area, we derive the Friedmann equations describing the dynamics of the universe with any spatial curvature. Using entropy formulae for the static spherically symmetric black hole horizons in Gauss-Bonnet gravity an...

We extend a recently developed numerical code to obtain stationary, axisymmetric solutions that describe rotating black hole spacetimes in wide class of modified theories gravity. The utilizes relaxed Newton-Raphson method solve the full nonlinear Einstein's equations on two-dimensional grid with Newton polynomial finite difference scheme. validate this by considering static and holes general r...

Models with a scalar field coupled to the Gauss-Bonnet Lagrangian appear naturally from Kaluza-Klein compactifications of pure higher-dimensional gravity. We study linear, cosmological perturbations in the limits of weak coupling and slow-roll, and derive simple expressions for the main observable sub-horizon quantities: the anisotropic stress factor, the time-dependent gravitational constant, ...

We study the relation between the causality and positivity of energy bounds for Gauss-Bonnet gravity in an AdS7 background. Requiring the group velocity of metastable states to be bounded by the speed of light places a bound on the value of Gauss-Bonnet coupling. To find the positivity of energy constraints we compute the parameters which determine the angular distribution of the energy flux in...

The observed late time accelerated expansion of the universe [1] combined with the problems that arise when trying to rationalize it with the simplest of explanations, such as a cosmological constant [2], have triggered an increased interest in finding alternatives for the nature of dark energy. Scalar fields, widely used in the inflationary paradigm [3], constitute a familiar way of providing ...