As an application of Gradient Expansion (long-wavelength) approximation , we studied the inhomogeneous universe including the gravitational wave(GW). For a plane-symmetric cosmological model, we could implement the 2nd order expansion and analyze the purely non-linear perturbation of GW. The result indicates that the non-linear eect plays an important role in anisotropic stage of the universe. ...

We consider the classical fluctuations of the gravitational constant generated by bubbles in the inflationary universe. For extended inflation, we demonstrate numerically how and how large fluctuations are produced during bubbleexpansion. The amplitude of the fluctuations depends on the Brans-Dicke parameter ω: if ω is of the order of unity, the amplitude becomes of the order of unity within on...

Composite fluxbrane and S -brane solutions for a wide class of intersection rules are considered. These solutions are defined on a product manifold R∗×M1×. . .×Mn which contains n Ricci-flat spaces M1, . . . , Mn with 1-dimensional factor spaces R∗ and M1 . They are determined up to a set of functions obeying non-linear differential equations equivalent to Toda-type equations with certain bound...

Einstein gravity coupled to a massive skew symmetric field Fμνλ leads to an acceleration law that modifies the Newtonian law of attraction between particles. We use a framework of non-perturbative renormalization group equations as well as observational input to characterize special renormalization group trajectories to allow for the running of the effective gravitational coupling G and the cou...

A covariant scalar-tensor-vector gravity theory is developed which allows the gravitational constant G, a vector field coupling ω and the vector field mass μ to vary with space and time. The equations of motion for a test particle lead to a modified gravitational acceleration law that can fit galaxy rotation curves and cluster data without non-baryonic dark matter. The theory is consistent with...

We study the possible singularities of isotropic cosmological models that have a varying speed of light as well as a varying gravitational constant. The field equations typically reduce to two dimensional systems which are then analyzed both by dynamical systems techniques in phase space and by applying the method of asymptotic splittings. In the general case we find initially expanding closed ...

The temperature correction to the Einstein action is considered which does not depend on the Planck energy physics. The leading correction may be interpreted in terms of the temperature dependent effective gravitational and cosmological constants. The correction to the gravitational constant appears to be valid for all temperatures T ≪ EPlanck. It is universal since it is determined only by the...

In typical refrigerant compressors, peak cylind er pressures under liquid slugging conditions are as high as 10 times the peak pressures during the normal operation. In this paper we model this phenomenon by considering the compression process with a separated gas and liquid media in the cylinder. Two cases of this model for various liquid fractions are simulat ed. Even though time histories co...

A covariant scalar-tensor-vector gravity theory is developed which allows the gravitational constant G, a vector field coupling ω and the vector field mass μ to vary with space and time. The equations of motion for a test particle lead to a modified gravitational acceleration law that can fit galaxy rotation curves and cluster data without non-baryonic dark matter. The theory is consistent with...

Recently observational data indicates that the discrepancy arises at late time, when the age of the universe is some billions years. In this context the Friedmann-RobertsonWalker model is a unique correspondence between the expansion rate and the distance scale. Although general theory of relativity (GTR) is the most suitable theory for describing universe as a whole, but still there are some p...