• Chuying Wang

     Title: What IIB looks IIA string: String Cobordisms via Non-Compact CFTs

Abstract: The Swampland Cobordism Conjecture predicts the domain walls connecting the Landscape. In our paper [2603.00225], we provide a worldsheet QFT (flowing to a critical CFT under RG flow) that connects the worldsheets of IIA and IIB string theories. The non-compact character of these interpolations means that the description of the actual domain walls develop strongly coupled regions described by a linear dilaton background, where the worldsheet description breaks down. Our constructions are heavily inspired by supercritical string theory, but are logically independent from it. We also analyze the fate of IIA/IIB D-branes and NS5 branes as they cross the domain wall between these two theories.

• Elijah Sheridan

Title: Cohomology Formulae and Holes in Effective Cones for D-brane Physics

Abstract: One avenue for progress in string phenomenology is the construction of explicit UV models with realistic IR physics. However, extracting IR predictions from UV models is often mathematically intricate. For example, in compactifications of type II string theory on Calabi–Yau threefolds (CY3s), D-branes make many important contributions to the IR EFT — from axions to the visible sector — in a manner characterized in part by line bundle cohomology. Motivated by D-brane physics, we study the structure of effective line bundles/divisors on CY3s and their global sections. By clarifying and exploiting the relationship between birational geometry and cohomology, we characterize the structure of "holes" in effective cones (non-effective divisor classes inside the effective cone) and illustrate how the number of global sections of effective divisors on CY3s is given by computable piecewise closed-form formulae.

• Felipe Figueroa

     Title: Heavy string states

Abstract: In this talk I will present an approach to construct a large portion of the open bosonic string spectrum using light-cone quantization and study their couplings. More concretely, I will show how to combine transverse oscillators into irreducible SO(25) representations corresponding to single-particle states and present an algorithm that generates all single-particle states level by level. Moreover, I will show a procedure that builds entire Regge trajectories from the knowledge of the states living at the bottom of the trajectory, leading to closed-form expressions for infinitely many excited states at once. This approach uncovers a surprisingly ordered and recursive structure within the open-string spectrum, suggesting that its massive states form an algorithmically constructible network.

• TBA

Title: TBA

Abstract:  TBA