Covariant Closed String Coherent States

TL;DR

This paper constructs covariant coherent states for closed strings, linking classical string loops with quantum states and vertex operators, and discusses conditions for their physical relevance.

Contribution

It provides the first explicit construction of covariant coherent closed string states and relates different descriptions of string states, including classical, lightcone gauge, and covariant forms.

Findings

Covariant coherent states correspond to classical string loops.

Existence of covariant vertex operators requires lightlike compactification.

Projected states without lightlike compactification have a clear classical interpretation.

Abstract

We give the first construction of covariant coherent closed string states, which may be identified with fundamental cosmic strings. We outline the requirements for a string state to describe a cosmic string, and using DDF operators provide an explicit and simple map that relates three different descriptions: classical strings, lightcone gauge quantum states and covariant vertex operators. The naive construction leads to covariant vertex operators whose existence requires a lightlike compactification of spacetime. When the lightlike compactified states in the underlying Hilbert space are projected out the resulting coherent states have a classical interpretation and are in one-to-one correspondence with arbitrary classical closed string loops.