Gravity with spin excludes fermionic strings

TL;DR

This paper demonstrates that in metric-affine gravity, the intrinsic spin of matter prevents fermions from forming string-like configurations, challenging the validity of superstring theory.

Contribution

It reveals a fundamental incompatibility between fermionic strings and the gravitational field equations in metric-affine gravity, disputing superstring theory.

Findings

Fermions cannot form point or string configurations in metric-affine gravity.

The cyclic identity for the curvature tensor forbids fermionic strings.

Superstring theory is incompatible with the gravitational field equations in this framework.

Abstract

The existence of intrinsic spin of matter requires the metric-affine formulation of gravity, in which the affine connection is not constrained to be symmetric and its antisymmetric part (torsion tensor) is a dynamical variable. We show that the cyclic identity for the curvature tensor in the metric-affine formulation forbids fermions represented by Dirac spinors to form point or string configurations. Consequently, fermionic strings contradict the gravitational field equations in the presence of spin. Superstring theory is therefore incorrect.