Speaker: Markus Luty
Title: 2D U(1) Chiral Gauge Theory on a Laptop
Room: 3024
Host:
Abstract: This talk will present a method to compute the spectrum of an arbitrary 2D chiral U(1) gauge theory coupled to fermions on a computer using Hamiltonian truncation. The gauge and 't Hooft anomalies and the theta dependence are reproduced by the Hamiltonian used in the numerical computation. A validation of the method is presented for massless 2D QED (the Schwinger model), obtained on a laptop computer using Mathematica. The application of the method to the chiral "543" model is in progress, and is expected to give accurate numerical predictions for the low-lying spectrum of this model using similarly modest computational resources. The generalization to non-Abelian gauge theories and higher dimensions will be discussed.
User:
High-Energy Seminars
Time:
1:30pm - 3:00pm
Description:
Speaker: Ken Van Tilburg (Stanford)
Title: Your Noise is My Signal: Fundamental Physics with Intensity Interferometry
Room: 3024
Host: Hsin-Chia Cheng
Abstract: The inherent noise in the intensity of light from astrophysical sources imprints correlations in photon arrival times, forming the very signal of intensity interferometry. Recent technological advances are reviving intensity interferometers as capable tools for high-precision astronomical measurements. I will propose a technique called the "expanding ejecta method" (EEM) to determine angular diameter distances to supernovae based purely on geometry, augmenting the calibration of the cosmic distance ladder or even enabling a direct inference of the cosmic expansion rate. I will also introduce a new variant of intensity interferometry --- "extended-path intensity correlation". EPIC enables ground-based differential astrometry at microarcsecond-level precision in a field of view as large as several arcseconds on sources of high surface brightness. The scientific applications of EPIC include measuring the astrometric lensing noise induced by the structure of dark matter on sub-parsec length scales (corresponding to halos with sub-stellar masses), an observable that is exquisitely sensitive to the microphysics of dark matter.
User:
High-Energy Seminars
Time:
1:30pm - 3:00pm
Description:
Speaker: Eric Swanson (U. Pitt.)
Title: Predictiveness as Discovery
Room: 3024
Host: John Terning
Abstract: Traditional methods of fitting data involves hypothesis testing, with "discovery" declared if the null hypothesis is rejected. This approach often assumes that the data is generated by the model, under-estimates systematic errors, and leads to overfitting. Common methods for overcoming the last issue, such as LASSO, AIC, and BIC do not perform well. In addition, the entire methodology relies on the dubious prospect of finding the global minimum of a complex multidimensional objective function. I propose to address these issues by reframing discovery as "predictiveness" -- namely does a postulated effect (eg, a new particle) assist in predicting new measurements. The method obviates many of the traditional problems and leads to more robust results. The implementation of the scheme and applications to simple problems will be presented.
