Higher powers in gravitation

Higher Powers in Gravitation

We consider the Friedmann-Robertson-Walker cosmologies of theories of gravity that generalise the Einstein-Hilbert action by replacing the Ricci scalar, R, with some function, f(R). The general asymptotic behaviour of these cosmologies is found, at both early and late times, and the effects of adding higher and lower powers of R to the Einstein-Hilbert action is investigated. The assumption tha...

Higher Derivative Gravitation in Superstrings

A discussion of the number of degrees of freedom, and their dynamical properties, in higher derivative gravitational theories is presented. It is shown that non-vanishing (Cmnpq) 2 terms arise in N=1, D=4 superstring Lagrangians due to one-loop radiative corrections with light field internal lines. 1 Bosonic Gravitation The usual Einstein theory of gravitation involves a symmetric tensor gμν wh...

Nontrivial vacua in higher-derivative gravitation.

A discussion of an extended class of higher-derivative classical theories of gravity is presented. A procedure is given for exhibiting the new propagating degrees of freedom, at the full non-linear level, by transforming the higher-derivative action to a canonical second-order form. For general fourth-order theories, described by actions which are general functions of the scalar curvature, the ...

Higher-derivative Gravitation in Bosonic and Superstring Theories

Abstract. A discussion of the number of degrees of freedom, and their dynamical properties, in higher-derivative gravitational theories is presented. The complete non-linear sigma model for these degrees of freedom is exhibited using the method of auxiliary fields. As a by-product we present a consistent non-linear coupling of a spin-2 tensor to gravitation. It is shown that non-vanishing (Cμνα...

Sums of Squares, Cubes, and Higher Powers