A review of Einstein Cartan Theory to describe superstrings with intrinsic torsion

TL;DR

This paper reviews Einstein Cartan Theory, extending general relativity with torsion, and applies it to describe superstrings with intrinsic torsion in curved backgrounds, including D-branes and NS-NS fields.

Contribution

It provides a comprehensive review of Einstein Cartan Theory and demonstrates its application to superstring models with intrinsic torsion, linking torsion to D-brane actions.

Findings

Derived vacuum equations in Einstein Cartan Theory.

Formulated D-brane actions with torsion in curved backgrounds.

Connected torsion to the antisymmetric NS-NS B-field in superstring theory.

Abstract

This paper reviews the Einstein Cartan theory (ECT), the famous extension of general relativity (GR) in presence of spacetime torsion. The vacuum equations are derived step by step. Vielbein formulation is discussed for determining the field equations in presence of matter. This review would be easily comprehensible for any student familiar with general relativity. Further, ECT is used to describe superstrings with intrinsic torsion, assuming a $D_p$-brane in presence of a curved background of the NS-NS Kalb-Ramond field. D-brane worldvolume is a flat spacetime governed by the Dirac-Born-Infeld (DBI) action. In presence of the dynamical NS-NS $B$-field, the contortion tensor equals the totally antisymmetric torsion. Using this, the form of the $D_p$-brane action in presence of torsion is determined.