Anisotropic tensor calculus

Anisotropic scalar-tensor cosmologies.

We examine homogeneous but anisotropic cosmologies in scalar-tensor gravity theories, including Brans-Dicke gravity. We present a method for deriving solutions for any isotropic perfect fluid with a barotropic equation of state (p ∝ ρ) in a spatially flat (Bianchi type I) cosmology. These models approach an isotropic, general relativistic solution as the expansion becomes dominated by the barot...

Introduction to Tensor Calculus

Preface These are general notes on tensor calculus originated from a collection of personal notes which I prepared some time ago for my own use and reference when I was studying the subject. I decided to put them in the public domain hoping they may be beneficial to some students in their effort to learn this subject. Most of these notes were prepared in the form of bullet points like tutorials...

Anisotropic fractional diffusion tensor imaging.

Traditional diffusion tensor imaging (DTI) maps brain structure by fitting a diffusion model to the magnitude of the electrical signal acquired in magnetic resonance imaging (MRI). Fractional DTI employs anomalous diffusion models to obtain a better fit to real MRI data, which can exhibit anomalous diffusion in both time and space. In this paper, we describe the challenge of developing and empl...

A Primer on Tensor Calculus

A Weyl-covariant tensor calculus

On a (pseudo-) Riemannian manifold of dimension n > 3, the space of tensors which transform covariantly under Weyl rescalings of the metric is built. This construction is related to a Weyl-covariant operator D whose commutator [D,D] gives the conformally invariant Weyl tensor plus the Cotton tensor. So-called generalized connections and their transformation laws under diffeomorphisms and Weyl r...