Talks

Although traditional astronomy was associated with visible light, it grew enormously in the twentieth century with the opening up of the electromagnetic and non-electromagnetic spectra. This happened in parallel with the development of quantum mechanics, which was employed by astrophysicists to explain planets, stars, galaxies and the history of the entire universe. Sometimes astrophysics provided a ready application for atomic, nuclear, particle and condensed matter physics; sometimes it provided an inspiration for fresh, basic understanding. This symbiotic relationship continues in the twenty-first century. In this talk, I will briefly recount some of this history and outline three contemporary observational challenges to quantum mechanics: neutron stars with ultra-strong magnetic fields, cosmic rays with individual energies comparable with that of a well-hit cricket ball and the origin of life.

Since Feynman quantum mechanics is associated with path integrals. However, some aspects of quantum mechanics are best explained using higher dimensional structures, such as strings or branes. I will survey deformation quantization and quantization of integrable systems and their connections to topological strings and four dimensional gauge theories. Our characters will be Heisenberg spin chains, many-body systems, gauge instantons, and quantum hydrodynamics of intermediate long waves. 

Astrophysics and cosmology grew, symbiotically, alongside quantum mechanics, over the past hundred years. The developing fields of atomic, nuclear and particle physics found motivation and application to central problems in astrophysics. These included the elucidation of stellar and interstellar spectra, the powering of stars and supernovae, the origin of the chemical elements, the properties of neutron stars and the interpretation of cosmic rays.  This relationship continues and is expressed in some of the most pressing problems today, notably the nature and consequences of dark matter, the provenance of cosmic structure and baryon asymmetry, the properties of magnetars, the acceleration of the highest energy cosmic rays and the origin of life.

Achieving precise control over microbial community composition is critical for applications ranging from bioremediation to human health but remains challenging due to the complexity of microbial interactions and resource variability. This work presents a framework for the bottom-up engineering of microbial communities by leveraging resource dynamics and temporal niches in fluctuating environments.
This approach assembles and maintains microbial "dream teams" - small, defined communities with desired properties—using serial dilution experiments. By treating resource concentrations as dynamic "control knobs," it enables stable coexistence and precise tuning of species abundances. Theoretical models, informed by experimental data from natural and synthetic microcosms, incorporate ecological and metabolic parameters, including species-specific time lags and dilution factors, to identify resource combinations that maximize community stability and diversity.
I will also describe how to engineer a multi-cycle resource strategy to overcome resource limitations and dramatically increase microbial diversity. By systematically varying resource ratios across growth-dilution cycles, this strategy creates additional temporal niches that allow for the coexistence of a larger number of species than traditional methods. Numerical simulations demonstrate that multi-cycle strategies significantly enhance species diversity, approaching the theoretical upper bound of 2^n-1 species coexisting on n resources.

According to general relativity, the remnant of a binary black hole merger is a perturbed Kerr black hole. Perturbed Kerr black holes emit "ringdown" radiation which is well described by a superposition of damped exponentials ("quasinormal modes”), with frequencies and damping times that depend only on the mass and spin of the remnant. The observation of gravitational radiation emitted by black hole mergers might finally provide direct evidence of black holes, just like the 21 cm line identifies interstellar hydrogen. I will review the current status of this "black hole spectroscopy" program. I will focus on: (1) the role of nonlinearities in ringdown modeling, (2) the current observational status of black hole spectroscopy, and (3) future prospects for the observability of modified gravity effects and nonlinear modes.

The correspondence of AGT sets up, in part, a connection between six-dimensional superconformal theories and 2d CFT. We will give a mathematical construction of 2d CFT from 6d SCFT which involves recent progress in our understanding of the holomorphic twist 6d superconformal symmetry. We then turn to the question of enhancement of familiar structures in 2d CFT to 6d including the well-known Segal—Sugawara construction. Finally, I will set up a Dolbeault enhancement of the AGT correspondence which is expected to probe coherent cohomology of the moduli space of instantons.