TPI Seminars

Past Events and Seminars

TPI Seminars begin again in the fall.

Past Events and Seminars

Patrick H. Diamond

Patrick H. Diamond

University of California, San Diego
Tuesday, May 9, 2017, 3:15 pm
CCIS L1-160

Pattern formation in magnetically confined plasmas: why it matters

This colloquium will discuss the physics of turbulent transport in magnetic confinement devices, such as tokamaks, with special emphasis on scale selection and its consequences. Using analogies with turbulent pipe flow and geophysical fluids, the basic physics of magnetized plasma turbulent transport is developed. Then, the two principle secondary patterns-avalanches and zonal shear flows-are introduced. Scale selection is linked to the natural competition between these two structures. We present the ExB staircase as the natural resolution to the competition, and discuss recent work on the bstaircase and layering dynamics. Throughout , we discuss the implications of the physics for achieving ignition in a magnetically confined plasma.

This talk is the 2017 Hiroomi Umezawa Memorial Lecture.

 Jorge Hirsch, 2016 Umezawa Memorial Colloquium Lecturer

Prof. Jorge E. Hirsch

University of California, San Diego
Friday, October 28, 2016, 3 pm CCIS L1-160

Meissner effect in superconductors: an unrecognized puzzle

Superconductivity, the flow of electric current with zero resistance in certain metals at low temperatures, was discovered in 1911 by Kammerlingh Onnes. It took another 22 years for Meissner and Ochsenfeld to discover the telltale property of superconductors that makes them different from “perfect conductors”: the spontaneous expulsion of magnetic fields from the interior of a metal becoming superconducting. This “Meissner effect” is generally believed to be explained by the conventional BCS-London theory of superconductivity developed in 1957. Instead, I argue that the Meissner effect is an unrecognized anomaly, an observation that cannot possibly be explained within the established paradigm and requires a paradigm shift [1]. I point out that conventional BCS-London theory violates Faraday’s law, Lenz’s law, Newton’s laws and the second law of thermodynamics in its description of both the Meissner effect and the superconductor to normal transition in a magnetic field. I argue that to explain the observed phenomena in a way that respects these fundamental laws requires charge flow in direction perpendicular to the normal-superconductor phase boundary, and requires that the normal state charge carriers have hole-like character. The conventional theory of superconductivity does not possess these physical elements. Instead, the alternative theory of hole superconductivity [2], proposed in 1989 to explain high Tc superconductivity in cuprates and superconductivity in general, does. The empirically observed unexplained correlation between superconductivity and Hall coefficient [3] supports our point of view.

[1] T. S. Kuhn, “The Structure of Scientific Revolutions”, University of Chicago Press, 1962.
[2] References in
[3] I.M. Chapnik, “On the empirical correlation between the superconducting Tc and the Hall coefficient”, Phys. Lett. A 72, 255 (1979). Hosts: R. Sydora and F. Marsiglio

Professor Manu Paranjape

Groupe de physique des particules
Université de Montréal 
Friday, September 16, 2016
11 am, CCIS 4-196

Three Explorations of Gravity in the Lab

We analyze three ideas for the study of gravity in interaction with matter, which give rise to a method of measuring the speed of gravity, a method of gravitationally inducing quantum transitions and the possibility of devising a graviton laser.