Organized by: Joel L. Lebowitz
Speaker: T. Shinbrot, Rutgers University
Time/Place:
3/4/04, 11:30am, Hill 705
Title: "Dry Granular Flows Can
generate Surface Features Resembling Those Seen in Martian Gullies"
Abstract: Over the last decade or
more, contradictory evidence of Martian climate - indicating that
surface temperatures seldom if ever approach the melting point of
water at midlatitudes - and geomorphic features - consistent with
liquid flows at these same latitudes - have proven difficult to
reconcile. In this talk I discuss evidence that several features of
liquid-erosional flows can be produced by dry granular materials when
individual particle settling is slower than characteristic debris flow
speeds. Since the gravitational acceleration on Mars is about 1/3
that on Earth, and since particle settling speeds scale with gravity,
I propose that some (though perhaps not all) Martian geomorphological
features attributed to liquid flows may in fact be associated with dry
granular flows in the presence of reduced gravity.
Speaker:P. Kleban, University of Maine
Time/Place: 3/11/04,
11:30am, Hill 705
Title: "Thermodynamics of the Farey Fraction Spin Chain"
Abstract: We examine number of
closely-related one-dimensional statistical models based on the Farey
fractions. These models are rigorously known to exhibit a (barely)
second-order phase transition at non-zero temperature, even though the
magnetization jumps from its fully saturated value to zero at the
critical point. We give the explicit asymptotic form of the free
energy. In a physical interpretation, the transition is due to
long-range many-body forces. It is natural to introduce a magnetic
field. The resulting phase diagram is determined by rigorous methods
and renormalization group. The results are verified via a connection
to dynamical systems, using a cluster approximation. We also show how
the Lewis three-term equation (from number theory) may be used to
calculate certain correlation functions in terms of the free energy.
Speaker: V. Shtelen, Rutgers University
Time/Place: 3/11/04,
1:30pm, Hill 705
Title: "Nonlocal Transformations of Kolmogorov Equations into the Backward Heat Equation"
Abstract: The talk is a review of
the results obtained by the speaker in collaboration with George
Bluman, and published in the Journal of Mathematical Analysis and
Applications, 291, (2004), 419-437. We extend and solve the classical
Kolmogorov problem of finding general classes of Kolmogorov equations
that can be transformed to the backward heat equation. These new
classes include Kolmogorov equations with time-independent and
time-dependent coe cients. Our main idea is to include nonlocal
transformations. We describe a stepby- step algorithm for determining
such transformations. We also show how all previously known results
arise as particular cases in this wider framework.
SPRING BREAK - NO SEMINAR THIS WEEK
Speaker: H. Spohn, TU Muenchen
Time/Place: 3/25/04,
11:30am, Hill 705
Title: "The Phonon Boltzmann
Equation for Weakly Disordered Harmonic Crystals"
Abstract: We report on joint work
with L. Lukkarinen, which has the goal to derive the Boltzmann
equation for energy transport in harmonic crystals with random
masses. The natural object turns out to be a suitably defined Wigner
function. Its kinetic limit is proved by the graphical expansion
method of Erdoes and Yau.
Speaker: N. Rajewsky, New York University
Time/Place: 3/25/04,
1:30pm, Hill 705
Title: "Computational Prediction of microRNA Targets"
Abstract: A very recent discovery
is the abundance of hundreds of small RNA encoding genes (microRNAs)
in the genomes of multicellular organisms such as human, mouse, fly,
worm which are thought to mediate translational regulation of other
genes by binding to partially complementary sites in mRNAs. Here I
present an algorithm which is designed to identify targets of this new
and large class of regulatory genes. I also discuss experimental
validation.