Large and infinite extra dimensions

TL;DR

This paper surveys large and infinite extra dimensions in a brane-world setting. It examines how ordinary matter can be localized on a 3+1 dimensional brane and how gravity propagates in the bulk via KK towers or warp factors. It covers the ADD scenario with large extra dimensions, including collider signals from light KK gravitons, bulk sterile neutrinos, gauge coupling unification, and proton stability, as well as non-factorizable warped geometries (RS1/RS2) and holographic interpretations. It also discusses infinite extra dimensions, gravity localization, brane cosmology, Lorentz-violation prospects, and speculative ideas about brane-Universe creation, highlighting both phenomenological signatures and open theoretical challenges.

Abstract

The emphasis in the developmet of theories with more than three spatial dimensions has recently shifted towards ``brane world'' picture, which assumes that ordinary matter (with possible exceptions of gravitons and other, hypothetic, particles which interact very weakly with matter) is trapped to a three-dimensional submanifold --- brane --- embedded in fundamental multi-dimensional space. In the brane world scenario, extra dimensions may be large, and even infinite; they may have effects, directly observable in current or fothcoming experiments. On the basis of simple field-theoretic models, various ideas in this direction are exposed at a non-expert level.

Figures (10)

• Figure 1:
• Figure 2: Domain wall solution.
• Figure 3: Spectrum of four-dimensional masses of fermions in domain wall background. The gap between zero mode (with $m=0$) and non-zero modes is of order $hv$. Continuum starts at $m=m_5 \equiv hv$.
• Figure 4: Charge $q$, displaced from the brane, is connected to the brane by a flux tube.
• Figure 5: Emission of a graviton into extra dimensions (or, equivalently, creation of a KK graviton) in the process $e^+ e^- \to \gamma + \hbox{graviton}$. Electron, positron and photon propagate along the brane, the graviton escapes into the bulk.