ICTP High Energy, Cosmology and Astroparticle Physics

Scattering amplitudes constrain effective field theories from the bottom up through general consistency requirements, including unitarity and causality. Existing bounds mainly use four-point amplitudes. This talk explains how amplitudes with more external points supply additional constraints beyond the four-point analysis, and demonstrates the method through an application to Large-Nc quantum chromodynamics.

Explaining the cosmic matter–antimatter asymmetry requires baryogenesis before Big Bang nucleosynthesis. A precise treatment must evolve baryon and lepton flavour charges while including the relevant Standard Model Yukawa interactions and electroweak and QCD sphaleron processes. This talk introduces a full-flavour-covariant formalism and a new formalism covariant under quark flavour transformations. Applications include SO(10) leptogenesis and cloistered baryogenesis. The work also produces BOLEH, a public general-purpose code for BaryOn and Lepton charge Evolution in the Hot big bang.

Davide Germani discusses how established field-theory techniques help interpret precise ATLAS and CMS measurements of heavy-quark systems. The first case concerns top–antitop states near their production threshold, drawing on recent calculations by Paolo Nason and collaborators. Topics include threshold resummation, nonperturbative QCD corrections, and the way the top quark’s short lifetime controls the formation and decay of quasi-bound states at collider energies. The second case examines whether X(3872) is a compact exotic hadron or a weakly bound neutral D-meson molecule. A comparison of the conventional Flatté parametrization with an effective field theory containing a reversed-sign kinetic term clarifies the physical meaning of that term and its relationship to a negative effective range. The seminar shows how adapting established methods can address new anomalies and structures in hadron spectroscopy.