# Fall 2014 Seminar

Talks are 12:00 noon on Thursdays in Olin 268, unless otherwise noted.

December 4, 2014. Joint Math/Physics & Astronomy Seminar.

## Diseases, Fame and Merit - Various Outbreaks on Social Networks

### Erik Bollt,
Department of Mathematics, Clarkson University

**Abstract:** Dynamical Systems, Chaos theory and
Complex Systems theory has some useful mathematical tools to
bring to bear on problems that are very familiar to our own
lives. Furthermore, social media has some really relevant
large scaled data that also lends toward a modern discussion
of what happens when people socially contact.

### Fall Schedule

September 11, 2014

## The Living Cell as Viewed by a Physicist

**Abstract:** The cross-disciplinary field of biophysics
is growing rapidly, and new opportunities to study
biophysics are being developed here at Bucknell. But what,
exactly, does a physicist have to offer to the study of
life? I will say a bit about the methods developed and used
by biophysicists, but I will primarily address this
question by leading a tour through the cell from the
perspective of a physicist, highlighting the roles played
electric forces, work and energy, and entropy.

Show/hide abstract.

September 25, 2014

## Evolution and Survival at Inflating Frontiers

### Max Lavrentovich, University of Pennsylvania

**Abstract:** Populations of individuals often migrate
or divide into new territory. Such range expansions occur
in microbial colonies, expanding animal populations, viral
infections, etc. In many cases, the individuals at the
population frontier have to compete for space. The
competition and the shape of the frontier have dramatic
consequences for the evolutionary dynamics of the
population. We study the survival probability of mutations
occurring at inflating frontiers which increase in size over
time. A frontier inflates, for example, when the population
is spreading out radially. We find that inflating frontiers
can enhance mutation survival probability by orders of
magnitude relative to frontiers that stay the same
size. Finally, we consider the fate of a population
undergoing irreversible, deleterious mutations. These
mutations can lead to a loss of the fittest members of the
population. The loss occurs more readily in spatially
distributed populations.

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October 9, 2014

## Fermions & Bosons, Forces & Pressures: Insights into Thermodynamics from Simple Quantum Mechanics

**Abstract:** The fundamental symmetries required for
identical particles in quantum mechanics have thermodynamic
implications. These manifest themselves in things like the
rigidity of solid matter, white dwarf and neutron stars, and
Bose-Einstein condensation. I will use insights from
elementary quantum mechanics to analyze the origin of what
are often referred to as degeneracy pressure and fermion
repulsion.

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October 16, 2014

## Making Cells with Active Microtubule Mixtures

### Jennifer Ross, University of Massachusetts Amherst

**Abstract:** Biology utilizes energy to organize itself
from the nanoscale to the macroscopic scale. We seek to
determine the universal principles of organization from the
molecular scale that give rise to architecture on the
cellular scale. We are specifically interested in
the organization of the microtubule cytoskeleton, a rigid,
yet versatile network in most cell types. Microtubules in
the cell are organized by motor proteins and crosslinkers.
This work applies the ideas of statistical mechanics
and condensed matter physics to the non-equilibrium pattern
formation behind intracellular organization using the
microtubule cytoskeleton as the building blocks. We examine
these processes in a bottom-up manner by adding
increasingly complex protein actors into the system. Our
systematic experiments expose nature’s laws for nanoscale to
micron scale organization and have large impacts on biology
as well as illuminating new frontiers of non-equilibrium
physics. Much of the work I will be sharing was done by
undergraduate researchers.

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October 30, 2014

## Astronomical tests of MoNDian Dark Matter

**Abstract:** MoNDian dark matter (MDM) is a new form of
dark matter that naturally accounts for Milgrom’s scaling,
usually associated with modified Newtonian dynamics (MoND),
and theoretically behaves like cold dark matter (CDM) at
cluster and cosmological scales. The original proposal for
MDM is based on the intriguing relationship between gravity
and thermodynamics, and was, in part, inspired by Verlinde's
work on entropic gravity. In this talk, I will discuss the
theoretical background for MDM and observational tests at
galactic and cluster scales.

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November 13, 2014

## Non-equilibrium Statistical Mechanics: a growing frontier of “pure and applied” theoretical physics

**Abstract:** Founded over a century ago, statistical
mechanics for systems in thermal equilibrium has been so
successful that, nowadays, it forms part of a typical
physics core curriculum. On the other hand, most of
“real life” phenomena occur under
non-equilibrium conditions. Unfortunately, statistical
mechanics for such systems is far from being well
established. The goal of understanding complex collective
behavior from simple microscopic rules (of evolution, say)
remains elusive. As an example of the difficulties we face,
consider predicting the existence of a tree from an
appropriate collection of H,C,O,N,... atoms! Over the last
two decades, an increasing number of condensed matter
theorists are devoting their efforts to this frontier. After
a brief summary of the crucial differences between text-book
equilibrium statistical mechanics and non-equilibrium
statistical mechanics, I will give a bird’s-eye view of some
key issues, ranging from the “fundamental” to (a
small set of) the “applied.” The methods used
also span a wide spectrum, from simple computer simulations
to sophisticated field theoretic techniques. These will be
illustrated in the context of an overview of our work, as
well as a simple model for transport.

Show/hide abstract.

December 4, 2014. Joint Math/Physics & Astronomy Seminar.

## Diseases, Fame and Merit - Various Outbreaks on Social Networks

### Erik Bollt,
Department of Mathematics, Clarkson University

**Abstract:** Dynamical Systems, Chaos theory and
Complex Systems theory has some useful mathematical tools to
bring to bear on problems that are very familiar to our own
lives. Furthermore, social media has some really relevant
large scaled data that also lends toward a modern discussion
of what happens when people socially contact.

Show/hide abstract.