On the No-ghost Theorem in String Theory

TL;DR

This paper presents a straightforward proof of the no-ghost theorem in critical bosonic string theory utilizing a similarity transformation, simplifying previous approaches.

Contribution

It introduces a novel, simplified proof method for the no-ghost theorem in string theory using a similarity transformation.

Findings

Proof of the no-ghost theorem using similarity transformation

Simplification of previous proof techniques

Clarification of the theorem's conditions

Abstract

We give a simple proof of the no-ghost theorem in the critical bosonic string theory by using a similarity transformation.