A few Ricci-flat stacks as phases of exotic GLSM's

Understand

In this letter we follow up recent work of Halverson-Kumar-Morrison on some exotic examples of gauged linear sigma models (GLSM's).

• Specifically, they describe a set of U(1) x Z_2 GLSM's with superpotentials that are quadratic in p fields, rather than linear as is typically the case.
• These theories RG flow to sigma models on branched double covers, where the double cover is realized via a Z_2 gerbe.
• For that gerbe structure, and hence the double cover, the Z_2 factor in the gauge group is essential.