# Revisiting the classifications of 6d SCFTs and LSTs

## TL;DR

This paper constructs previously unknown 6d superconformal field theories and little string theories using the frozen phase of F-theory, expanding the classification of these theories beyond prior methods.

## Contribution

It provides explicit constructions of all missing 6d SCFTs and LSTs via frozen F-theory, proposing a complete classification when combined with existing unfrozen phase results.

## Key findings

- Explicit construction of missing 6d SCFTs and LSTs
- Demonstration of SCFTs not descending from LSTs
- Proposal of a unified classification framework

## Abstract

Gauge-theoretic anomaly cancellation predicts the existence of many 6d SCFTs and little string theories (LSTs) that have not been given a string theory construction so far. In this paper, we provide an explicit construction of all such "missing" 6d SCFTs and LSTs by using the frozen phase of F-theory. We conjecture that the full set of 6d SCFTs and LSTs is obtained by combining the set of theories constructed in this paper with the set of theories that have been constructed in earlier literature using the unfrozen phase of F-theory. Along the way, we demonstrate that there exist SCFTs that do not descend from LSTs via an RG flow.