Generalized Inverse Seesaws

TL;DR

This paper introduces two novel models that generalize the inverse seesaw mechanism using fermion triplet and quintuplet representations, expanding the theoretical landscape for neutrino mass generation.

Contribution

The paper presents two new inverse seesaw models with higher fermionic representations, requiring minimal additional fields and challenging the preference for standard scenarios.

Findings

The fermion triplet model requires no extra multiplets compared to standard inverse seesaw.

The fermion quintuplet model introduces an additional scalar field.

Higher fermionic representations are unlikely to naturally produce small neutrino masses.

Abstract

The seesaw mechanism can be generalized to a Type-III variant and a quintuplet variant. We present two models that provide analogous generalizations of the inverse seesaw mechanism. The first model employs a fermion triplet F ~ (1,3,0) and requires no additional multiplets or parameters relative to the standard inverse seesaw. We argue that, from a bottom-up perspective, there appears to be no particular reason to preference the usual scenario over this variant. The second model employs a fermion quintuplet F ~ (1,5,0) and requires an additional scalar S ~ (1,4,1). We also show that minimal inverse seesaws with even larger fermionic representations are not expected to realize naturally small neutrino masses.