Do all 5d SCFTs descend from 6d SCFTs?

TL;DR

This paper challenges the idea that all 5d SCFTs originate from 6d SCFTs by showing counterexamples and proposing a revised conjecture involving BPS strings, with implications for classifying 5d theories.

Contribution

It introduces counterexamples to the existing conjecture and proposes a new framework involving BPS strings to derive all 5d SCFTs from 6d SCFTs.

Findings

Counterexamples to the original conjecture.

Inclusion of BPS strings allows deriving all 5d SCFTs from 6d SCFTs.

A procedure to integrate out BPS strings in geometric descriptions.

Abstract

We present examples of 5d SCFTs that serve as counter-examples to a recently actively studied conjecture according to which it should be possible to obtain all 5d SCFTs by integrating out BPS particles from 6d SCFTs compactified on a circle. We further observe that it is possible to obtain these 5d SCFTs from 6d SCFTs if one allows integrating out BPS strings as well. Based on this observation, we propose a revised version of the conjecture according to which it should be possible to obtain all 5d SCFTs by integrating out both BPS particles and BPS strings from 6d SCFTs compactified on a circle. We describe a general procedure to integrate out BPS strings from a 5d theory once a geometric description of the 5d theory is given. We also discuss the consequences of the revised conjecture for the classification program of 5d SCFTs.