S. Randjbar-Daemi

Spontaneous compactification in six-dimensional Einstein-Maxwell theory

A discrete set of solutions to the classical Einstein-Maxwell equations in six-dimensional space-time is considered. These solutions have the form of a product of four-dimensional constant curvature space-time with a 2-sphere. The Maxwell field has support on the 2-sphere where it represents a monopole of magnetic charge, n = ±1, ±2, …. The spectrum of massless and massive states is obtained for the special case of flat 4-space, and the solution is shown to be classically stable. The limiting case where the radius of the 2-sphere becomes small is considered and a dimensionally reduced effective lagrangian for the long range modes is derived. This turns out to be an SU(2) × U(1) gauge theory with chiral couplings.

An Anomaly Free Model in Six-Dimensions

Abstract We show that a gauged supergravity theory based on E 6 × E 7 × U(1) is free of gauge and gravitational anomalies in six dimensions. It compactifies to (Minkowski) 4 × S 2 by the standard monopole mechanism. With a monopole of strength n in E 6 , the resulting four-dimensional theory exhibits chiral SO(10) × U(1) with 2| n | families (and no antifamilies). Supersymmetry is broken.

Origin of spontaneous symmetry breaking in theories with large extra dimensions

We suggest that the electroweak Higgs particles can be identified with extra-dimensional components of the gauge fields, which after compactification on a certain topologically non-trivial background become tachyonic and condense. If the tachyonic mass is a tree level effect, the natural scale of the gauge symmetry breaking is set by the inverse radius of the internal space, which, in case of the electroweak symmetry, must be around

Fermion zero-modes on brane-worlds

\sim 1/

Chiral fermions on the lattice

TeV. We discuss the possibility of a vanishing tree level mass for the Higgs. In such a scenario the tachyonic mass can be induced by quantum loops and can be naturally smaller than the compactification scale. We give an example in which this possibility can be realized. Starting from an Einstein--Yang--Mills theory coupled to fermions in 10-dimensions, we are able to reproduce the spectrum of the Standard Model like chiral fermions and Higgs type scalars in 4-dimensions upon compactifying on

Locally supersymmetric σ-model with Wess-Zumino term in two dimensions and critical dimensions for strings

{\mathbb{C}}P^1\times {\mathbb{C}}P^2

Instability of Higher Dimensional {Yang-Mills} Systems

. The existence of a monopole solution on

4d-flat compactifications with brane vorticities

{\mathbb{C}}P^1

On the overlap formulation of chiral gauge theory

and a self dual U(1) instanton on

Instanton Induced Compactification and Fermion Chirality

{\mathbb{C}}P^2