**February 26, 2008**

16:00-17:00, JR245

**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**

14:00-15:00, JR215

**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.