Thursday, September 5Mark Levi, Penn State University
1:25pmMathematics through physics
ABSTRACTPhysics often provides mathematics not only with a problem, but sometimes also with the idea of a solution.
Some calculus problems can be solved by a physical argument more quickly and easily than by the "standard"
approach used in college courses. This simplification can be quite striking in some cases.

Quite a few theorems which may seem somewhat mysterious become completely obvious when
interpreted physically (the trick is to find a suitable interpretation). This is the case for some “elementary” theorems
(the Pythagorean Theorem, Pappus' theorems, some trig identities (e.g., cos(x+y)=..., Euler's famous formula
V-E+F=2, and more) and for some less elementary ones (no familiarity with any of these is
assumed): Green's theorem, the Riemann Mapping Theorem, the Gauss-Bonnet
theorem, Noether's theorem on conserved quantities, Poincare integral invariance, and more.

I will describe a miscellaneous sampling of problems according to the audience's preferences.
Thursday, September 12Joel Hass, UC Davis
1:25pmSome applications of geometry to problems in biology
ABSTRACTMany problems arising in biology are geometric, since many biological properties
are reflected in the shapes of biological objects. <br> We will explain recent developments in
the use of conformal mappings and hyperbolic geometry to study several biological problems.<br>
1. The study of cortical surfaces. In particular, the question of how similar are two brains. <br>
2. The classification of proteins. <br>
3. Deducing the evolutionary tree of old-world monkeys from fossilized skulls.
Thursday, September 19Dmitri Burago, Penn State University
1:25pmCounting collisions in hard ball gas models and singular geometry of non-positive curvature
ABSTRACTWe will discuss a solution to a long–standing problem. The problem itself can be explained
to school kids. Basically, one asks if there exists an N that not more than N elastic collisions
can occur between 10 identical balls before they fly away from each other (no gravity, no
external forces). Of course, there is nothing special about 10, it could be any M and then N=N(M).
The solution is also elementary modulo a few well–known facts. The problem was that the tools
and facts lie in an area of math which was thought to be very far from the original problem.
We will not get into any technicalities, so the talk should be easily accessible.
Wednesday, September 25Robert Lang, Alamo, CA
4:00pmFrom flapping birds to space telescopes: the mathematics of origami
ABSTRACTThe last decade of this past century has been witness to a revolution in the development and application of mathematical techniques to origami, the centuries-old Japanese art of paper-folding. The techniques used in mathematical origami design range from the abstruse to the highly approachable. In this talk, I will describe how geometric concepts led to the solution of a broad class of origami folding problems – specifically, the problem of efficiently folding a shape with an arbitrary number and arrangement of flaps, and along the way, enabled origami designs of mind-blowing complexity and realism, some of which you’ll see, too. As often happens in mathematics, theory originally developed for its own sake has led to some surprising practical applications. The algorithms and theorems of origami design have shed light on long-standing mathematical questions and have solved practical engineering problems. I will discuss examples of how origami has enabled safer airbags, Brobdingnagian space telescopes, and more.
Thursday, October 3Diane Henderson, Penn State University
1:25pmThe William Pritchard Fluid Mechanics Laboratory
ABSTRACTPenn State is one of the few Departments of Mathematics that houses a physical laboratory. In this talk
I will describe some of the activities going on in the lab. Then we will walk down to the basement for a tour.
Thursday, October 10Roger Howe, Yale University
1:25pmAbout the numbers 12 and 24
ABSTRACTThe numbers 12 and 24 come up often in contexts that involve symmetry. For example,
a cube has 12 edges, and a dodecahedron has 12 faces. This talk will discuss the extent to which
various appearances of 12 and 24 should be considered "the same". We will argue that
some appearances should definitely be considered
the same, and speculate about others.
Thursday, October 17Vadim Kaloshin, University of Maryland
12:00pmKirkwood gaps and instability for three body problems
ABSTRACTIt is well known that, in the Asteroid Belt, located between the orbits of Mars and Jupiter, the distribution of asteroids has the so-called Kirkwood gaps exactly at mean motion resonances of low order. We study the dynamics of
the Newtonian Sun-Jupiter-Asteroid problem near such resonances. We construct a variety of diffusing orbits which
show a drastic change of the osculating eccentricity of
the asteroid, while the osculating semi-major axis is kept almost constant. We shall also discuss stochastic aspects of dynamics in near mean motion dynamics. This might
be an explanation of presence of Kirkwood gaps.
This is a joint work with J. Fejoz, M. Guardia, and P. Roldan.
Thursday, October 31Krishnaswami Alladi, University of Florida
1:25pmPaul Erdos - one of the most influential mathematicians of our times
ABSTRACTPaul Erdos (1913-1996) was one of the most influential
mathematicians of the twentieth century. This is his 100-th birthday
year. A Hungarian by birth, Erdos had no permanent home. He
traveled around the world constantly, lecturing at hundreds of
universities, and seldom staying at a place for more than a week.
On these trips he collaborated with both mathematicians and students.
Of his research papers that exceed 1500 in number, more than half
are in collaboration. While traveling, he was constantly on the look
out for very young and talented mathematicians with whom he would
collaborate and mold their careers. In a remarkable career that spanned
the entire twentieth century, Erdos made pioneering contributions to
number theory, combinatorics, graph theory, set theory and geometry.
After describing his unusual life and some of his charming idiosyncrasies,
we will discuss some of his most fundamental contributions and ideas in
prime number theory and probabilistic number theory. Both the story of
the elementary proof of the prime number theorem and the creation of
probabilistic number theory are fascinating, and will be described. Finally,
I will also briefly describe how I met him, and how we collaborated.
Thursday, November 7Ken Ono, Emory University
1:25pmAdding and counting
ABSTRACTThis lecture will only be about adding and counting.
There are many difficult problems related to these seemingly simple
tasks. Here we address the problem of finding an exact formula
for p(n), the number of partitions of n, and we explain a comprehensive
theory of congruence properties.
Thursday, November 7Ken Ono, N/A
Thursday, November 14Sarah Koch, University of Michigan
1:25pmMating habits of polynomials
ABSTRACTGiven two suitable complex polynomial maps, one can construct a new dynamical system by mating the polynomials; that is, by "gluing'' the polynomials together in a dynamically meaningful way. In this talk, we focus on quadratic polynomials -- we begin with a brief discussion of parameter space for quadratic polynomials (the Mandelbrot set), we then define the mating of two quadratic polynomials, and finally we explore examples where the mating does exist, and examples where it does not.
Thursday, November 21Don Saari, UC Irvine
1:25pmWe vote, but do we get what we want?
ABSTRACTWe vote to select the choice of a pizza, of a member to a social group, of congress, of rankings of football
teams, of almost everything. But, does the outcome reflect what the voters really wanted? Mathematics
is providing that there is much to worry about. Indeed, by the end of this presentation, some in the audience
will worry about some personal election in which she or he was involved.