Research Areas:

Nonlinear Conservation
Laws:
The idea that certain quantities in systems are conserved is a
fundamental idea in science and are an avenue for writing down
equations describing how these systems evolve. The system of
Euler questions, modeling nonlinear gas dynamics, is one of these
systems. One particular consequence of these equations is
that
waves of different density and pressure propagate at different
velocities. These different velocities cause the solution to
“fold” on it self in finite time producing a discontinuous solution in
finite time (even from smooth initial conditions.) Much work
in
the field of Nonlinear conservation laws is done trying to analyze the
dynamics of these discontinuities (shock waves) and elementary waves,
including these moving discontinuities, interact.

Time Series Analysis:
When we
observe phenomena only a subset of the underlying quantities that
govern the system may be visible. With this limited
knowledge,
can we reconstruct some of the overall (hidden) dynamics of a
system? This is one of the goals of Time Series
Analysis.
Characteristics such as dimension and Lyapunov exponent are estimated,
as well as looking for the “best” reconstruction the systems’
attractor. While difficult to justify, this analysis may
suggest
whether or not a system exhibits chaos.

Factorization Theory in
Monoids:
We are familiar that each natural number can be uniquely factored into
products of prime numbers. It turns out that that natural
numbers
are a Monoid, a set of elements with an associative binary operation
(multiplication) that has an identity element, 1. We can
consider
other Monoids generated by the natural numbers such as the McNugget
monoid, the set of numbers generated by adding any combinations of 6, 9
and 20’s. In this monoid, where the binary operation is plus,
elements may no longer have unique factorizations into irreducible
elements. (In contrast to factorization into the
primes)
Various questions can be studied about factorization properties of
elements in these (numerical) monoids.

Publications:

Rebecca Conaway, Felix Gotti, Jesse Horton, Christopher O'Neill,
Roberto Pelayo, Mesa Pracht, Brian Wissman, "Minimal presentations of
shifted numerical monoids", International
Journal of Algebra and Computation, 28 53 (2018)

Katherine F. Benson, Daniela
Ferrero, Mary Flagg, Veronika
Furst, Leslie Hogben, Violeta Vasilevskak, Brian Wissman, "Zero forcing
and power domination for graph products", Australasian
Journal of Combinatorics, Volume 70(2) (2018), Pg 221-235

B. D. Wissman, L. C. McKay-Jones, and P.-M. Binder, "Entropy rate
estimates from mutual information", Physical Review E 84 (2011): 046204

P.-M Binder and B.D. Wissman, "Geometry of Repeated Measurements in
Chaotic Systems". CHAOS 20, 013106 (2010).

B.D. Wissman, “Global solutions to the ultra-relativistic Euler
equations”. Comm. in Math. Phys., 306(3) (2011), 831-851.