11am - 12pm: Running EFT-hedron with null constraints at loop level

Implications of general properties of quantum field theory, such as causality, unitarity, and locality include constraints on the couplings of the effective field theory (EFT) coefficients. These constraints follow from the connections between the infrared (IR) and ultraviolet (UV) theory imposed by dispersion relations for four-particle amplitudes which formally allow one to express EFT couplings through the moments of positive-definite functions forming the EFT-hedron geometry. Previous studies of these positivity bounds were mainly focused on the weakly coupled EFTs, limiting the analysis to tree-level amplitudes of the IR theory. In this work, I will show how to extend the scope of positivity bounds including one-loop amplitudes, which is essential especially for the loops of massless particles. The results demonstrate that while for small coupling constants, the one-loop bounds are in good agreement with the tree-level results, the allowed EFT parameter ranges can be significantly modified if a weak coupling assumption is not additionally imposed. I will discuss the difficulties of obtaining the constraints in forward limit in four dimensions related to the infrared singularities and show how to overcome these problems by constructing finite combinations of null constraints.