Speaker
Description
In theories of flavor based on modular invariance, correlations between quark and lepton observables are a natural expectation. These arise from their shared dependence on a common modulus field, from joint experimental constraints, and—in the context of Grand Unified Theories (GUTs) — from possible embedding into common gauge multiplets. Despite this, most bottom-up modular flavor models developed so far have analyzed the quark and lepton sectors independently, making it impossible to explore their potential interconnections.
In this talk, we present a comparative study of joint quark–lepton fits across different classes of modular flavor models, with the aim of uncovering the nontrivial interplay between the two sectors. We focus in particular on how correlations among observables emerge depending on the model's number of free parameters relative to the number of available experimental constraints. When the number of parameters exceeds the number of constraints, correlations may be washed out or hidden by flat directions in parameter space. Conversely, in more predictive scenarios with fewer parameters, correlations can become sharp and testable.
We illustrate these features with concrete examples, highlighting how the modulus $\tau$ can mediate non-obvious links between the quark and lepton flavor patterns.
