Geometry and dynamics of the brane-world

TL;DR

This paper reviews the geometry and dynamics of brane-world models derived from string theory, highlighting how extra dimensions influence gravity, cosmology, and astrophysical phenomena through local and nonlocal effects.

Contribution

It provides a comprehensive review of classical geometry and dynamics in brane-world models, emphasizing the impact of 5-D effects on gravity, cosmology, and black hole physics.

Findings

Local high-energy effects alter inflation dynamics.

Nonlocal effects modify cosmological perturbations.

Brane-world models predict new gravitational phenomena.

Abstract

Recent developments in string theory have led to 5-dimensional warped spacetime models in which standard-model fields are confined to a 3-brane (the observed universe), while gravity can propagate in the fifth dimension. Gravity is localized near the brane at low energies, even if the extra dimension is noncompact. A review is given of the classical geometry and dynamics of these brane-world models. The field equations on the brane modify the general relativity equations in two ways: local 5-D effects are imprinted on the brane as a result of its embedding, and are significant at high energies; nonlocal effects arise from the 5-D Weyl tensor. The Weyl tensor transmits tidal (Coulomb), gravitomagnetic and gravitational wave effects to the brane from the 5-D nonlocal gravitational field. Local high-energy effects modify the dynamics of inflation, and increase the amplitude of scalar and tensor perturbations generated by inflation. Nonlocal effects introduce new features in cosmological perturbations. They induce a non-adiabatic mode in scalar perturbations and massive modes in vector and tensor perturbations, and they can support vector perturbations even in the absence of matter vorticity. In astrophysics, local and nonlocal effects introduce fundamental changes to gravitational collapse and black hole solutions.