Double Copy and Beta Functions in String Theory

This paper explores a double-copy-like decomposition of internal states in one-loop string amplitudes, extending previous work. It applies this to calculate beta functions for gauge and gravitational couplings in heterotic string theory, finding trivial vanishing results due to supersymmetry but providing a general model-independent framework for analysis.

• •Applies a double-copy-like decomposition to string amplitudes.
• •Calculates beta functions in heterotic string theory.
• •Finds trivial vanishing beta functions due to supersymmetry.
• •Provides a general model-independent framework.