(13.11.) Modular Invariant Potentials in String Theory
Gonzalo Fernandez Casas (Instituto de Fisica Teorica - IFT UAM/CSIC)
13.11.2025 at 16:15
In this talk, I will discuss two projects highlighting how towers of light states and modular symmetries shape physics in quantum gravity, cosmology, and string theory. In inflation, trans-Planckian field motion lowers the cutoff to the species scale, motivating a modular-invariant inflaton potential that depends only on this scale. For a modulus, this yields a Starobinsky-like plateau in which the number of e-folds tracks the number of species, suggesting that the tower of states actively drives inflation. In string compactifications, the same field-dependent species scale generates positive one-loop potentials in no-scale vacua, producing Minkowski “desert points,” de Sitter-like plateaus, and eventual runaway behavior consistent with Swampland expectations. An explicit Z2×Z2 orientifold example shows how modular invariance can help control the physics and cancel the cosmological constant. Together, these results point to a unified role for dualities and species-scale physics in moduli stabilization and early-universe dynamics.
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