KEK 素粒子原子核研究所・理論セミナー(Prof. Yu-tin Huang)
In this talk I will introduce new constraints on couplings of operators in effective field theory derived from Unitarity and Lorentz invariance in the UV. These constraints come in the form of positive geometries in the space of couplings. The origin of this positivity originates from the remarkable positive properties of Gegenbauer polynomials, which are the basis polynomials dictated by Lorentz invariance. Unitarity then dictates that the discontinuity of the S-matrix has a positive expansion on these polynomials. This double positivity give rises to the mathematical object that we named the “EFThedron”, for which all consistent QFT must reside in. Adding that the underlying theory has a worldsheet description, allows us to begin to carve out the string landscape in an on-shell fashion.