Talks

GW250114, with a signal-to-noise ratio of ∼80, enables the most precise single-event tests of strong-field gravity to date: setting the tightest constraints on deviations from general relativity, delivering the cleanest ringdown measurement yet, and placing stringent bounds on compact object structure. The one thing it withholds is Love: no tidal deformability is detected, with a 90% upper limit of $\tilde{\Lambda} < 34.8$, fully consistent with the Kerr prediction of vanishing tidal deformability.

From a first principles QFT perspective, the problem of thermalization in heavy-ion collisions may appear to be intractable. However, at very high energies, a semi-classical "shockwave" description of ultrarelativistic nuclei (and their scattering) emerges, described by the Color Glass Condensate (CGC) EFT. We first discuss how such shockwaves form in QCD, and how they decay, and the rich insights provided by examining this process in the language of broken global symmetries. We then discuss multi-particle production in collisions of the shockwave coherent states. The radiated glue initially forms a far-from-equilibrium Glasma, which can be understood as a generalized Susskind-Glogower squeezed state. The subsequent evolution of the Glasma after it decoheres is characterized by turbulent IR and UV flows with universal features in common with ultracold atomic gases. We discuss some of the unresolved open questions in this description of thermalization in heavy-ion collisions. 

As particle physicists we usually think about small fluctuations of fields, but the phenomenology of our theories can depend crucially on the global structure of the symmetries and the topology of field space. First I'll discuss an ambiguity in the Standard Model gauge group, whose different versions make different model-independent predictions for the existence of fractionally charged particles. Such signatures at the LHC merit further attention from experimentalists and phenomenologists, as these particles can both reveal the structure of the SM, and falsify theories of unification. Then I'll turn to axion theories and, as an example, the DFSZ model, where careful examination of global properties of the scalars and the gauge group can affect the structure of axion strings, and resolve the cosmological domain wall problem.

Current pulsar timing array (PTA) analyses do not take full advantage of pulsar distance information, thereby missing out on improved angular resolution and on a potential factor-of-two gain in detection sensitivity for individual gravitational-wave (GW) sources. In this work, we investigate the impact of precise pulsar distance measurements on angular resolution as an extension to previous work measuring the angular resolution of a dense, isotropic PTA [Jow et al., 2025]. We present a coherent map-making technique that utilizes precise pulsar distance measurements to reach the diffraction-limited resolution of an individual source: δθdiff ∼ (1/SNR)(λGW/r) ≈ 2 arcmin, where the SNR refers to the detection strength of the source. With this level of angular resolution, identifying an EM counterpart may become feasible, enabling multi-messenger follow-up. We show that for SNR = 10, which may be the current sensitivity level using a coherent analysis, the diffraction limit is reached with roughly 9 pulsars. Moreover, angular resolution scales sharply with the number of known pulsar distances as ∼ (1/SNR)Ndist/2 . Thus, each additional pulsar with high signal-to-noise timing and precise distance measurement can improve PTA resolution by an order of magnitude. The distance to the best-timed millisecond pulsar (PSR J0437−4715) is already constrained to subparsec levels. We argue, therefore, that a coherent analysis of PTA data, fully incorporating pulsar distance information, is timely.