Claire de Korte (Max Planck Institute for Mathematics in the Sciences)
Title: Algebraic Constraints on Conformal Correlators
Abstract: Conformal symmetry has long been used as a powerful tool to "bootstrap" conformal correlation functions. The embedding space formalism simplifies this process by linearising the action of the conformal group. This allows us to write conformal correlators as Laurent polynomials in terms of a set of so-called conformal building blocks, whose coefficients are arbitrary functions of conformally invariant cross-ratios. Conformal symmetry puts strong constraints on the kinds of Laurent monomials that can appear in a given conformal correlator. In a recent paper, me and my collaborators studied these constraints from an algebraic perspective, offering concrete tools to determine the minimal set of monomials one must include.
Bio: Claire is a PhD student at the Max Planck Institute for Mathematics in the Sciences. Co-supervised by professors Bernd Sturmfels and Daniel Baumann, she works at the intersection of applied algebraic geometry and theoretical cosmology. Prior to her PhD, she earned a masters degree in Mathematical and Theoretical Physics from the University of Oxford.
Xavier Kervyn (Max Planck Institute for Physics)
Title: Structure and features of high-energy string amplitudes
Abstract: I will briefly review recent progress in understanding the structure of tree-level string amplitudes in the fixed-angle high-energy regime, using resurgence theory and difference equations instead of thimble analysis. The talk is based on arXiv:2604.07444 with Stephan Stieberger.
Bio: Xavier is a second-year PhD student in the string theory and quantum field theory groups at the Max Planck Institute for Physics, working on the structure of string amplitudes and connections to holography. He previously earned a master's degree in theoretical and mathematical physics in Munich, writing a thesis on high-energy string theory and flat space holography, as well as a Master of Advanced Study in Applied Mathematics from the University of Cambridge.
Jeffrey Backus (Princeton University)
Title: Higher-Point Partial Waves and String Theory
Abstract: Given any four-point scattering amplitude, the partial wave expansion resolves its residues into contributions from individual spin-s internal particles, where each coefficient must be non-negative due to unitarity. In this talk, we extend this formalism to all multiplicity and spacetime dimensions for the so-called "half-ladder" Feynman diagrams. We then apply our technology to the familiar "stringy" amplitudes which generalize the amplitudes of open bosonic string theory. In particular, we show for the first time that "Z-theory" --- which corresponds to tr phi^3 amplitudes in the alpha' -> 0 limit --- is inconsistent with unitarity at finite alpha'.
Bio: Jeff is a fourth-year graduate student at Princeton University. He is broadly interested in aspects of scattering amplitudes, with a particular eye towards describing "real-world" processes. His past and current work relates to surfaceology, the S-matrix bootstrap, and cosmology. He received his B.A. in physics and mathematics from Cornell University in 2023.
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