Speaker: Vazha Loladze
Title: Dynamics of the Fermion-Rotor System
Room: 3024
Host: Markus Luty
Abstract: In this talk, I will examine the dynamics of the fermion–rotor system, originally introduced by Polchinski as a toy model for monopole–fermion scattering. Despite its simplicity, the system is surprisingly subtle, with ingoing and outgoing fermion fields carrying different quantum numbers. I will show that the rotor acts as a twist operator in the low-energy theory, changing the quantum numbers of excitations that have previously passed through the origin to ensure scattering consistent with all symmetries, thereby resolving the long-standing Unitarity puzzle. I will then discuss generalizations of this setup with multiple rotors and unequal charges, and demonstrate how the system can be viewed as a UV-completion of boundary states for chiral theories, establishing a connection to the resolution of the puzzle using boundary conformal field theory.
User:
High-Energy Seminars
Time:
4:00pm - 5:00pm
Location:
PHY 285
Send Reminder:
Yes - 20251126
Description:
Speaker: Jens Osterhoff (LBL)
Title: Wakefield Accelerator Colliders for Particle Physics
Room: 285
Host: Matthew Citron
Abstract: Since its inception, the field of advanced accelerator research has regarded future particle-physics colliders as the ultimate application of >1 GV/m accelerator technology. Over the last decades, great experimental and theoretical progress [1,2,3] has enabled and motivated new concepts for potential future colliders based on wakefield accelerators (WFAs), both for Higgs factories and at the energy frontier. The most recent P5 Report [4] calls for “vigorous R&D toward a cost-effective 10 TeV pCM collider based on proton, muon, or possible wakefield technologies.” Specifically, the P5 Report requests “the delivery of an end-to-end design concept, including cost scales, with self-consistent parameters throughout” for a WFA machine. This presentation will outline the plan to produce such a design, and the opportunities and challenges for wakefield-based colliders, both as standalone machines and as a future technology upgrade option. WFA colliders at the energy frontier will likely operate in a new regime characterized by beam-beam interactions with large quantum beamstrahlung effects. Preliminary studies of the physics case in this regime at 10 TeV will be presented.
[1] C. A. Lindstrøm et al. “Beam-driven plasma-wakefield acceleration”, arXiv:2504.05558 (2025)
[2] E. Esarey et al. “Physics of laser-driven plasma-based electron accelerators”, Rev. Mod. Phys. 81, 1229 (2009)
[3] C. Jing “Dielectric Wakefield Accelerators”, Rev. Accel. Sci. Tech, 9, 127 (2016)
[4] P5 Report www.usparticlephysics.org/2023-p5-report/
User:
High-Energy Seminars
Time:
1:30pm - 3:00pm
Description:
Speaker:Henry Lin (Princeton/Stanford)
Title: Bootstrapping Euclidean Two-point Correlators
Room: 3024
Host: Mukund Rangamani
Abstract: Coordinates: PDSB 3024 at 13:30 on Dec 8
Abstract: We develop a bootstrap approach to Euclidean two-point correlators, in the thermal or ground state of quantum mechanical systems. We formulate the problem of bounding the two-point correlator as a semidefinite programming problem, subject to the constraints of reflection positivity, the Heisenberg equations of motion, and the Kubo-Martin-Schwinger condition or ground-state positivity. In the dual formulation, the Heisenberg equations of motion become "inequalities of motion" on the Lagrange multipliers that enforce the constraints. This enables us to derive rigorous bounds on continuous-time two-point correlators using a finite-dimensional semidefinite or polynomial matrix program. We illustrate this method by bootstrapping the two-point correlators of the ungauged one-matrix quantum mechanics, from which we extract the spectrum and matrix elements of the low-lying adjoint states. Along the way, we provide a new derivation of the energy-entropy balance inequality and establish a connection between the high-temperature two-point correlator bootstrap and the matrix integral bootstrap.
