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Texas A&M University

Events for 04/10/2020 from all calendars

Several Complex Variables Seminar

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Time: 10:20AM - 11:10AM

Location: Zoom

Speaker: Tanuj Gupta, Texas A&M University

Title: Student reading seminar on reproducing kernels

Abstract: More properties of reproducing kernels

Meeting ID: 930 289 270

Mathematical Physics and Harmonic Analysis Seminar

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Time: 1:50PM - 2:50PM

Location: BLOC 628

Speaker: Braxton Osting, University of Utah


Mathematical Physics and Harmonic Analysis Seminar

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Time: 1:50PM - 2:50PM

Location: Zoom seminar

Speaker: Gregory Berkolaiko, Texas A&M University

Title: Zoom Seminar: Global extrema of dispersion relation of tight-binding models

Abstract: Tight-binding approximation is frequently used in physics to analyze wave propagation through periodic medium. Its Floquet–Bloch transform is a compact graph with a parameter-dependent operator defined on it. The graph of the eigenvalues as functions of parameters is called the dispersion relation. Extrema (minima and maxima) of the n-th eigenvalue give rise to band edges: endpoints of intervals supporting continuous spectrum and therefore allowing wave propagation. Locating the extrema can be difficult in general; there are examples where extrema occur away from the set of parameters with special symmetry. In this talk we will show that a large family of tight-binding models have a curious property: there is a local condition akin to the second derivative test that detects if a critical point is a global (sic!) extremum. Under some additional assumptions (time-reversal and dimension 3 or less), we show that any local extremum of a given sheet of the dispersion relation is in fact the global extremum. Based on a joint project with Yaiza Canzani, Graham Cox, Jeremy Marzuola.

Banach and Metric Space Geometry Seminar

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Time: 3:00PM - 4:00PM

Location: BLOC220

Speaker: Yury Makarychev, Toyota Technological Institute at Chicago and Univ. of Chicago

Title: canceled due to the COVID-19 pandemic