M&m's

TL;DR

This paper explores a new class of string theories in 6 to 8 dimensions, called a/b,m,f theories, which are decoupled from gravity and relate to M-theory and F-theory, offering insights into their structure and phase behavior.

Contribution

It introduces a novel framework of string and membrane theories in 6-8 dimensions that parallels known theories in higher dimensions, clarifying aspects of F-theory and M-theory.

Findings

Identification of a/b,m,f theories with coupling constants but no gravity.

Parallel structure between these theories and known string theories in higher dimensions.

Implications for the phase structure of M theory.

Abstract

We consider M theory 5-branes with compact transverse dimensions. In certain limits the theory on the 5-brane decouples and defines ``little string theories'' in 5+1 dimensions. We show that the familiar structure of IIA/IIB,M,F- theory in 10,11,12 dimensions respectively has a perfect parallel in a theory of strings and membranes in 6,7,8 dimensions. We call these theories $a/b,m,f$ theories. They have a coupling constant but no gravity. This construction clarifies some mysteries in F-theory and leads to several speculations about the phase structure of M theory.