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February 26, 2008
Dr. Yohannes Shiferaw
Department of Physics, CSUN
Title: Stochastic calcium signaling in cardiac cells.
Abstract: Calcium ions play an important role in regulating various cellular processes. In a variety of cell types, calcium signaling occurs within spatially localized clusters where ion channels interact. The small number of channels involved ensures that the signaling process is stochastic. The aggregate response of several thousand of these localized clusters determines the cell?s behavior. In this talk I describe our recent theoretical work to understand how electrical signals on the cell membrane couples to intracellular calcium activity via a large ensemble of localized signaling units. Applying tools from the theory of stochastic processes we show, for the first time, how experimentally measured trigger-response relationships in cardiac cells arise.
February 6, 2008
Dr. David Klein
Department of Mathematics, CSUN
Title: Toward a Statistical Mechanical Test of General Relativity.
Abstract: Curvature in relativistic spacetimes corresponds to tidal forces in Newtonian mechanics, but curvature effects yield more precise information about physical phenomena. They give relativistic corrections to classical physics. In particular, classical Newtonian physics and general relativity should predict different statistical mechanical/thermodynamical behaviors of a gas in orbit around a central mass, subject to gravitational tidal forces in the Newtonian case, and effects of curvature of spacetime in the relativistic case, but otherwise ideal. This talk, based on recently published work by Peter Collas of the CSUN Physics Department and myself, will outline the mathematical structures needed for such a comparison. A complete relativistic theory of statistical mechanics does not currently exist, but physical arguments lead us to a plausible "candidate" for the general relativistic Helmholtz free energy for a gas in circular orbit in Schwarzschild spacetime. Our formula (expressed in Fermi coordinates) may be compared to the Newtonian Helmholtz Free energy of the gas, and to a special relativistic formula for the free energy derived by Wolfgang Pauli in the 1950s. Two theorems will be presented which show rigorously that the Newtonian and the special relativistic limits of our formula lead to these expected results, thus bolstering the credibility of our proposed formula. There remain significant barriers to a satisfactory merger of classical statistical mechanics and general relativity. Indeed, the blending of these two classical theories has many of the features of a shot-gun marriage. Some of these barriers will be described. Nevertheless, we think that this prototype example can serve as a starting point for a more general theory, and further work along these lines might lead to a new experimental test of general relativity.