Fluids Mechanics and Waves Seminar - Fall 2026
Seminars are held Mondays from 2:30 - 3:30 PM in CULM 611 and/or Zoom, unless otherwise noted.
For questions about the seminar schedule, please contact Daniel Massatt.
Zoom Link for talks: https://njit-edu.zoom.us/j/98002491251?pwd=4fEEaL2zNmxbvCEfgpQfbCZrueabVx.1
Passcode for the Zoom link will be included in announcements.
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September 14
Peter Nekrasov, Courant and Flatiron Institute
Integral equations for flexural-gravity wave scattering with applications to ice shelf rumples and rolls
Flexural waves are involved in a number of important phenomena, including the ocean-driven bending and flexing of floating ice sheets. The interaction of these waves with complex features such as rolls and rifts remains poorly understood despite being a potential precursor to ice shelf collapse. In the first part of this talk, we simulate the propagation of Lamb waves in Arctic ice shelves with periodic surface rolls. We find that ice shelves with surface rolls are able to reflect incident wave energy from the ocean, which may help to explain their long-term stability. To study this phenomenon more closely, we turn to a bulk-surface model for flexural-gravity waves and develop numerical tools for ice sheets with variable thickness or openings in the ice cover. We demonstrate how this general class of problems can be reduced to second kind integral equations supported on a compact region of the surface. This approach has a number of analytical and numerical advantages, and the accuracy and scalability of these methods are demonstrated through a variety of examples with extensions to ice floes and ice rumples.
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September 28
Curtiss Lyman, Columbia University
Band Spectrum Singularities and the Hunt for Weyl Points
We develop a systematic framework to study the dispersion surfaces of Schrödinger operators $H=−\Delta+V$, where the potential $V \in C^\infty(\mathbb{R}^n,\mathbb{R})$ is both periodic with respect to a lattice $\Lambda \subset \mathbb{R}^n$ and respects its symmetries, and then use this framework to find Weyl points - long sought features in the band spectra of periodic operators. The framework consists of a series of results that can be used to analyze the operator $H$ where the lattice $\Lambda$ is arbitrary, which we prove using techniques from Floquet-Bloch theory and representation theory. As an application of this framework, we describe the generic structure of some singularities in the band spectrum of Schrödinger operators invariant under various three-dimensional cubic lattices, in the process proving a conjecture of [Haimo Guo, Meirong Zhang, and Yi Zhu. “Three-Fold Weyl Points for the Schrödinger Operator with Periodic Potentials”]. Lastly, using the band structure of Schrödinger operators invariant under the body-centered cubic lattice, we then introduce an equivariant magnetic field to produce the desired Weyl points.
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October 12
Zhengqian Cheng, Columbia University
Variational Discrete Action Theory for Many-body Ground-states and the One-body reduced Density Matrix Functional
Efficient and robust algorithms for the many-body electron problem are fundamental to understanding molecules and materials. Standard methods such as density functional theory (DFT) provide an efficient solution but fail to capture strongly correlated effects. One common strategy to address this limitation is to combine DFT with a local correlated model, such as the multi-orbital Hubbard model. In this talk, I will introduce the Variational Discrete Action Theory as a method for solving the multi-orbital Hubbard model. VDAT is built on a many-body ansatz controlled by an integer \mathcal{N} with an evaluation technique based on the integer time Green's function. We demonstrate that VDAT, in the limit d=\infty, recovers the Gutzwiller approximation at \mathcal{N}=2 and the numerically exact solution given by the dynamical mean-field theory as \mathcal{N}\rightarrow\infty . Moreover, we find that VDAT converges to the exact solution exponentially in \mathcal{N}. This exponential rate is connected to a broader conjecture: a variational generalization of the \mathcal{N}-step Trotter-Suzuki decomposition of the imaginary-time projector e^{-\beta\hat{H}} , applied in a trial ansatz |\Psi_{0}\rangle, approaches the ground state exponentially fast with \mathcal{N}, in contrast to the polynomial convergence of the standard decomposition. In the second part of the talk, I will discuss the construction of a one-body reduced density matrix functional for the Mott transition, obtained from VDAT at \mathcal{N}=3 via the constrained search.
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December 07
Ryan Creedon, Brown University
Title forthcoming
Abstract Forthcoming
Homepage: https://ryanpcreedon.com/
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Updated: October 5, 2026