Thermal Physics seminars

Nicole Yunger Halpern (NIST, QuICS and University of Maryland) examines how to describe nonequilibrium matter in the early universe and particle colliders from the Standard Model. Classical lattice-gauge calculations have limited reach, motivating quantum simulation. Local Gauss-law constraints create an intricate Hilbert-space structure that complicates thermodynamic definitions for systems coupled to reservoirs, both at equilibrium and during nonequilibrium processes. The talk develops definitions of work and heat through strong-coupling thermodynamics, applying them to instantaneous quenches that quantum simulators can implement. A Z2 lattice gauge theory coupled to matter in one spatial and one temporal dimension provides the example: computed work and heat vary with the quench parameter and reveal the expected phase transition. The framework connects gauge constraints, reservoir coupling and experimentally relevant thermodynamic quantities.

Paul S. Weiss (UCLA) explores low-energy interactions and balanced cycling in natural systems as models for efficient synthetic devices and recycling. Because the relevant energies fall below visible-photon energies, tunnelling spectroscopy and imaging are used to probe these processes. Replicating biochemical cycling and low-energy transport could reduce the energy needed for devices and materials recovery. The work seeks missing physical principles, including spin conservation in chiral molecules and polarizability in biological and synthetic systems. This perspective has led to thermal-control advances in scale, speed and magnitude. Atomic-resolution imaging, spectroscopy and functional measurements help build precise structures while revealing heterogeneous nanoscale behaviour. The talk relates these advances to the physical, electronic, mechanical, thermal and chemical connections between materials and their surroundings that determine future nanomaterial measurements and devices.

Chi-Fang (Anthony) Chen presents a general framework for preparing quantum thermal states. It combines algorithms and analysis into a quantum counterpart of Markov chain Monte Carlo and models physical system–bath interactions. The work addresses the unresolved end-to-end preparation problem that limits calculations of thermal equilibrium properties and practical many-body quantum simulation.

Collective behavior of organisms creates environmental micro-niches that buffer them from environmental fluctuations e.g., temperature, humidity, mechanical perturbations, etc., thus coupling organismal physiology, environmental physics, and population ecology. This talk will focus on a combination of biological experiments, theory, and computation to understand how a collective of bees can integrate physical and behavioral cues to attain a non-equilibrium steady state that allows them to resist and respond to environmental fluctuations of forces and flows. We analyze how bee clusters change their shape and connectivity and gain stability by spread-eagling themselves in response to mechanical perturbations. Similarly, we study how bees in a colony respond to environmental thermal perturbations by deploying a fanning strategy at the entrance that they use to create a forced ventilation stream that allows the bees to collectively maintain a constant hive temperature. When combined with quantitative analysis and computations in both systems, we integrate the sensing of the environmental cues (acceleration, temperature, flow) and convert them to behavioral outputs that allow the swarms to achieve a dynamic homeostasis.