String Theory seminars

Consistency requirements on scattering amplitudes can constrain quantum gravity without a perturbative expansion. This talk applies analyticity, crossing and unitarity to maximally supersymmetric gravitational theories in ten and eleven dimensions. It extends bounds from the leading correction to higher-order effective couplings, comparing the allowed regions with string-theory and M-theory predictions. A nearby kink in eleven dimensions suggests a possible route toward characterizing the M-theory scattering matrix through consistency alone.

Some protected operators exist only at particular gauge-group ranks, a phenomenon connected conjecturally to black-hole microstates. This talk studies such fortuitous operators in ABJM theory at large Chern–Simons level. Harmonic representatives make the operators explicit, while analytic continuation of the two-loop Hamiltonian tracks them from finite rank toward the large-rank limit. Selected operator-product coefficients complement the trajectory analysis.

A proposed localization framework computes perturbative contributions directly in M-theory backgrounds containing M2 branes. Fixed-point information determines the supersymmetric action, while an equivariant complex describes fluctuations. The method produces Airy-function partition functions consistent with known ABJM calculations and extends to deformation regimes without independent field-theory answers. It also yields new one-loop terms in twisted indices associated with rotating, magnetically charged anti-de Sitter black holes.

Benjamin Safdi studies the axion mass constraints obtained when grand unification and string theory are considered together with the QCD axion. Unitarity reasoning and explicit string compactifications, including examples from the Kreuzer–Skarke type-IIB ensemble, favor masses between 10^-11 and 10^-8 electronvolts. The talk explains how these theoretical frameworks combine to restrict a candidate extension of the Standard Model.