Events
Condensed Matter Seminar
Altered Ground States via van der Waals Cavities
Dr. (candidate) Itai Keren
Columbia University
Mon, 15 Dec 2025, 11:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: Recent advances show that embedding solids within electromagnetic cavities can modify the ground state even in the absence of illumination. Hyperbolic van der Waals (vdW) materials, which provide dielectric environments with strongly enhanced photonic density of states, have recently emerged as a candidate platform for realizing such cavity effects in heterostructures. In this talk, I will present the first experimental realization of a cavity-coupled superconducting ground state, spatially resolved by magnetic force microscopy. This implemantation, utilizes a vdW material (hBN) as the cavity. Molecular resonances in the superconductor hybridize with the hyperbolic cavity modes to produce an altered ground state, which is probed by magnetic force microscopy. I will also discuss how new cavity architectures could offer previously inaccessible control over the interaction between the cavity and the target material. Together, these approaches outline a pathway toward tailoring cavity-coupled ground states.
Physics Colloquium
QCD at high energy: perturbative, non perturbative and maybe perturbative
Prof. Alexander Kovner
University of Connecticut (UCONN)
Tue, 16 Dec 2025, 16:00
Ilse Katz Institute for Nanoscale Science & Technology (51), room 015
Abstract: I will review the basic physics of strong interactions relevant to high energy scattering. I will concentrate on quantum evolution in QCD which predicts behavior of scattering cross section with increasing momentum transfer and energy, and will discus the qualitative differences between the two. Ideas about qualitatively new behavior at very high energies the so called perturbative saturation, or Color Glass Condensate will be introduced.
Biological and soft-matter physics
Linear quality analysis and optimization of stochastic thermostats for Langevin equations
Prof. Niels Grønbech-Jensen
Dept. of Mechanical and Aerospace Engineering and Dept. of Mathematics, University of California at Davis
Thu, 18 Dec 2025, 12:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: A basic struggle in simulations of statistical and dynamical systems is how to appropriately balance simulation accuracy for small time steps with simulation efficiency for large ones. Thus, understanding the influence of discrete time on the behavior of equations of motion is crucial for the understanding and optimization of physical system simulations. We argue that, in computational statistical mechanics, 1) it is not necessary to obtain accurate trajectories in order to generate accurate statistics, and 2) a numerical method should first and foremost be analyzed by its configurational properties since momentum is an unnecessary quantity for discrete-time sampling of the phase-space [1,2]. Building on a recent derivation of the complete set of optimal stochastic Verlet-type integrators [3], we here provide a linear framework for analyzing the quality of the large number of stochastic methods that have been proposed over the past five decades [4]. With some redundancy of logic we conclude that the previously identified complete set of integrators, of which the first was published in 2013 [5], is the only set that allows for large time-step simulations, while preserving statistical accuracy in the most basic measures of diffusion, drift, and sampling (Boltzmann) distribution, even if the simulated trajectories suffer from time-step errors. The methods are remarkably simple and are implemented into existing codes, such as the Molecular Dynamics suite, LAMMPS [6].
[1] Grønbech-Jensen, Molecular Physics 118, e1662506 (2020)
[2] Grønbech-Jensen, Journal of Statistical Physics 191, 137 (2024)
[3] Finkelstein et al., Journal of Chemical Physics 153, 134101 (2020)
[4] Grønbech-Jensen, arXiv:2505.04100, to appear in Journal of Statistical Physics (2025)
[5] Grønbech-Jensen and Farago, Molecular Physics 111, 983 (2013)
[6] https://docs.lammps.org/latest/fix_gjf.html
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