Graduate Student Seminar Archives

Fall 2019

Title:  A hierarchy of matroid invariants and a new matroid construction
Speaker:  Kevin Long, GWU
Date and Time:  Friday, November 22, 2:00PM-3:00PM
Place: Rome 206

Abstract: Matroids are a combinatorial object generalizing the concept of independence. Examples of matroids are seen in graph theory and linear algebra, where independence describes being acyclic or linearly independent respectively. I will provide an introduction to matroid theory and talk about some matroid invariants, including the Tutte polynomial, a well known invariant that specializes to the chromatic polynomial of a graph. I will also introduce some new results describing a new matroid construction, which behaves nicely with respect to these invariants.

Title: Methods of interpolation between two dual quaternions
Speaker:  Dionne Ibarra
Date and Time:  Friday, September 20, 3:00PM-4:00PM
Place: Rome 771

Abstract:  I will give a brief introduction to quaternions, dual numbers, and dual quaternions, then discuss methods of interpolation. Finally, I will explain how I obtained a succinct exponential notation for dual quaternions. 

Spring 2019

Graduate Student Seminar: Careers in Industry Panel

Speakers: Veronica Bloom (Northrop Grumman)

Michael Coleman (Naval Observatory)

Lara Langdon (United Income)

Jordan Misra (U.S. Census Bureau)

Meta Voelker (Applied Physics Lab, JHU)

Date and Time: Friday, April 19, 1-2PM (Note the earlier time)

Place: Rome Hall (801 22nd Street), Room 206


Abstract: The speakers all work in different areas in industry and have graduate degrees in mathematics and statistics. The panel of speakers will introduce themselves and answer questions from the audience about finding industry positions, what their work entails, and how their graduate experience applies to their careers.

Title: TBA
Speakers: Pavel Avdeev
Date and Time: Friday, April 12, 2-3PM
Place: Rome Hall (801 22nd Street), Room 206
Abstract: TBA

Speakers: Jozef Przytycki, Alexander Shumakovitch, GWU
Date and Time: Friday, March 29, 2-3PM
Place: Rome Hall (801 22nd Street), Room 206
Abstract: Professors  Jozef Przytycki and Alexander Shumakovitch will each give half hour talks about their research interests intended to give graduate students thoughts about for future areas of research.

Title: “Gram determinants motivated by Knot Theory”
Speaker:  Rhea Palak Bakshi, GWU
Date and Time: Friday, March 22nd, 2:00-3:00pm
Place:  Rome 206

Abstract:   In the 1990s, Rodica Simion posed a problem about the Gram determinant of Type B, whose solution, inspired by the work of W. B. R. Lickorish on the Witten – Reshetikhin – Turaev invariant of 3 – manifolds, was presented by Jozef H. Przytycki and his former student Qi Chen. In this talk I will define the Gram determinant of Type A and Type B and present the result proved by Przytycki and Chen. I will then define the Gram determinant of type ‘KB’, and speak about some of our recent work.  

Title:Index sets, decision problems, and classes of (somewhat) computable groups

Speaker: Iva Bilanovic, GWU
Date and Time: Friday, March 1, 2:00-3:00pm
Place: Rome 206
Abstract: We will introduce the elementary notions of computability theory with the intention of discussing a few classical decision problems, particularly those pertaining to group theory. Time allowing, we will discuss some recent results on recursively presented groups and computable groups.

Title:How to get your math paper published

Speaker: Robbie Robinson, GWU
Date and Time: Friday, February 1, 2:00-3:00pm
Place: Rome 206
Abstract: So you have written a paper and want to publish it. I'll describe some ideas about how to choose a venue (e.g., journal, conference proceeding), what to send and to whom, what to expect to happen next (basically, wait, revise, wait, and wait again). I'll discuss such issues as coauthoring vs single authoring, dealing with editors and referees, the ArXiV, page limits, and different types of journals. I'll also discuss how to be a referee. I hope to invite other faculty who may offer a different perspective, as well.

Fall 2018

Title:Khovanov homology and the PS braid conjecture

Speaker: Sujoy Mukherjee - GWU
Date and TimeFriday, November 16, 2:00-3:00pm
Place: Rome 206
Abstract: In 1984, knot theory was revolutionized with the discovery of the Jones polynomial. Fifteen years later, with several questions about it still unanswered, the polynomial was categorified into what is presently known as Khovanov homology (KH). The idea of KH is to associate a bigraded chain complex to a link whose homology is an invariant of the link itself. Additionally, the Euler characteristic of this chain complex, when interpreted appropriately, is the Jones polynomial.

Parts of the PS braid conjecture state that the order of the torsion subgroups in the KH of a closed braid is less or equal to its braid index. In 2017, with the discovery of links with large even torsion subgroups in their KH, this statement was resolved. At the same time, for the case of odd torsion subgroups, the first infinite families of knots and links with odd torsion subgroups up to \mathbb{Z}_7 were introduced.

In this talk, after providing a short introduction to KH, we will focus on knots and links with larger odd torsion subgroups than \mathbb{Z}_7, like \mathbb{Z}_9, \mathbb{Z}_{27}, and \mathbb{Z}_{25}. Additionally, we will discuss other recent developments in the study of torsion in KH.

Speakers: Valentina Harizanov, Xiaofeng Ren, GWU
Date and Time: Friday, November 2, 2-3PM
Place: Rome Hall (801 22nd Street), Room 206
Abstract: Professors Valentina Harizanov and Xiaofeng Ren will each give half hour talks about their research interests intended to give graduate students thoughts about for future areas of research.

Title:give us an idea of their research interests

Speaker: Lowell Abrams and Joel Lewis - GWU
Date and TimeFriday, October 26, 2:00-3:00pm
Place: Rome 206
Abstract:Professors Abrams and Lewis will each speak for a half hour to give us an idea of their research interests

Title:Utilizing Mathematica, Wolfram|Alpha, and other Wolfram technologies for teaching and research

Speaker: Andrew Dorsett of Wolfram Research about the Mathematica software
Date and TimeFriday, September 28, 2:00-3:00pm
Place: Rome 206
Abstract: I will begin with a technical overview of Mathematica, as well as briefly touching on the creation of Wolfram|Alpha. Next, we can discuss emerging trends in technology and what is currently available (or being developed) to support those trends. Then, to give you a sense of what's possible, I'll discuss how other organizations use these tools for teaching and research.
Spring 2018
Title: Scattering in generalized Hartree equation
Speaker: Anudeep Kumar
Date and TimeMonday, April 30, 2:30-3:30pm
Place: Rome 204
AbstractWe consider the focusing generalized Hartree equation in the mass-supercritical and energy-subcritical setting. The characterization of solutions behavior under the so called mass-energy threshold is known for the NLS case from the works of Holmer and Roudenko (radial) and Duyckaerts, Holmer and Roudenko (nonradial) and generalizations (Guevara and others). The scattering behavior is typically proved following the road map developed by Kenig and Merle in 2006, using the concentration compactness and rigidity properties, which is a standard tool by now in the dispersive problems.
In this work we give an alternative proof of scattering in the Hartree case, following the approach of Dodson and Murphy for the focusing 3d cubic NLS equation, which relies on the scattering criterion of Tao, combined with the radial Sobolev and Morawetz-type estimates.

Title: Mathematical Models for Genome Rearrangements and Whole Genome Duplications
Speaker: Pavel, Avdeev
Date and Time: Monday, April 23, 2:30-3:30pm
Place: Rome 204

Abstract: One of the key computational problems in comparative genomics is the reconstruction of genomes of ancestral species based on genomes of extant species. Since most dramatic changes in genomic architectures are caused by genome rearrangements, this problem is often posed as minimization of the number of genome rearrangements between extant and ancestral genomes.

The basic case of three given genomes is known as the genome median problem. Whole genome duplications (WGDs) represent yet another type of dramatic evolutionary events and inspire the reconstruction of pre-duplicated ancestral genomes, referred to as the genome halving problem.  

We start with a description of genome evolution and most dramatic evolutionary events such genome rearrangements and whole genome duplication. Then. we move to the most common mathematical model of genome rearrangements, called Double-Cut-and-Join (DCJ). We further describe generalizations and applications of the DCJ model. We also consider the
problem of ancestral genome reconstruction and its particular instances such as genome median and halving problems. Finally, we discuss topological and integer linear programming approaches to these problems. 

Title: Analysis and Modeling of Self-organized Systems with Long Range Interaction
Speaker: Chong Wang
Date and Time: Monday, April 16, 2:30-3:30pm
Place: Rome 204
Abstract: Energy-driven pattern formation induced by competing short and long range interaction is common in many biological and physical systems. We report on our work through two models. The sharp interface model is a  nonlocal and non-convex geometric variational problem. The admissible class of the energy functional is a collection of sets where each set is of finite perimeter. The original problem is recast as a variational problem on a Hilbert space through introducing internal variables. We prove the existence of the core-shell assemblies and the existence of the disc assemblies as the stationary points of the energy functional in ternary systems. We also prove the existence of a triple bubble in a quaternary system. The other model is the diffuse interface model concerning minimizers of the Ginzburg-Landau free energy supplemented with long range interaction in inhibitory systems. As model parameters vary, a large number of morphological phases appear as stable stationary states. One open question related to the polarity direction of double-bubble assemblies is answered numerically. More importantly, it is shown that the average size of bubbles in a single-bubble assembly does not depend on the ratio of volume fractions but rather is determined by the long range interaction coefficients and the sum of the minority constituent volumes. In double-bubble assemblies, a two-thirds power law between the number of double bubbles and the long range interaction coefficients in the strong segregation regime is justified both numerically and theoretically.  A range of parameters is identified that yields double-bubble assemblies. These two models can be connected through gamma convergence.

Title: Computability-Theoretic Properties of Orders and Complexity of Identifying Algebraic Properties on Computable Magmas
Speaker: Trang Ha
Date and Time: Monday, April 9, 2:30-3:30pm
Place: Rome 204

Abstract : A magma is computable if both its domain and its atomic diagram are computable. We investigate the Turing complexity of orders on computable orderable magmas by studying their algebraic and topological properties. We further discuss the spaces of orders on special self-distributive (and not necessarily associative) magmas that come from knot theory named quandles. We also consider the complexity of the index set of magmas that satisfy certain algebraic properties within the class of computable magmas. 

Title : From the Tutte Polynomial to the G-invariant

Speaker: Kevin Long
Date and Time: Monday, April 2, 2:30-3:30pm
Place: Rome 204
Abstract : Matroids are a combinatorial structure introduced by Hassler Whitney in 1935 as an abstraction of "independence" in linear algebra and graph theory. Since then, matroid theory has expanded to a field in its own right, with connections to geometry, coding theory, and other fields. In this talk, we first give the equivalent definitions of matroids and show how they relate to some familiar families of matroids. We then introduce the Tutte polynomial, a powerful matroid invariant, and the most classical one, which will allow us to delve into more modern work done by Dr. Joseph Bonin on the G-invariant, a strengthening of the Tutte polynomial. 

Note: The Graduate Student Seminar is mandatory for ALL graduate Students. Attendance will be taken.

Title - Multiplying fractions on a T-shirt
Speaker: Rhea Palak Bakshi, GWU
Date and Time: Monday, March 5, 2:30-3:30pm
Place: Rome 204
Abstract - In 1987 Józef Przytycki introduced Skein Modules as a way to extend the knot polynomials of the 1980's to knots and links in arbitrary 3-manifolds. Since their introduction Skein Modules have become central to the theory of 3-manifolds. In 1997, Charles Frohman and Razvan Gelca gave a nice product-to-sum formula for the Kauffman Bracket Skein Algebra of the torus times the interval. We try to discover a similar formula for the multiplication of curves on a thickened T-shirt. 

Title: Meet the Department Chair

Speaker: Frank Baginski 
Date and Time:  Monday, February 26, 2018, 2:30 pm
Place: Rome 204

Fall 2017

Title:  Optimal descriptions of computable groups

Speaker: Iva Bilanovic

Date and Time: Friday, December 1, 3:00-4:00pm

Place: Rome 206

Abstract: We will introduce the infinite dihedral group, D, a finitely generated group whose primitive and imprimitive sets of words are both computable given a computable copy of the group. By the Scott Isomorphism Theorem we can describe D by a sentence, in countable infinitary language, whose computable models are exactly the isomorphic copies of the group. The set of Gödel codes for these computable isomorphic copies of D allows us to check that our description is as simple as possible. 

Title:  Holder's regularity for solutions of a parabolic equation

Speaker: Xinyu Zhang

Date and Time: Friday, November 3, 3:00-4:00pm

Place: Rome 206

Abstract: De Giorgi introduced his method in 1957 to study the regularity of elliptic equations with rough coefficients. In this talk, we will consider, for simplicity, the laplacian-type equation and prove the solutions are Holder. I will firstly introduce the oscillation lemma, then show the lemma implies the Holder's continuity. Then I will fill the gaps between the oscillation lemma and De Giorgi's lemmas

Title:  The I-method and its application.

Speaker: Debdeep Bhattacharya

Date and Time: Friday, October 27 , 3:00-4:00pm

Place: Rome 206

Abstract: Developed by Colliander-Keel- Staffilani-Takaoka-Tao in 2001, the so called "I-method" has been extensively used to prove the global well-posedness of various nonlinear dispersive equations for data with infinite energy, where the classical energy-conservation arguments fail. The method uses a modified energy functional which is "almost conserved" in time, leading to a global existence. Following the work of Farah-Linares-Pastor we shall demonstrate this method for the geralized KdV equation and outline an improvement of available global well-posedness results for the modified Zakharov-Kuznetsov equation in 2D

Title:  An algebraic treatment of congruences in Number Theory.

Speaker: Konstantinos Smpokos

Date and Time: Friday, October 6 , 1:00-2:00pm

Place: Rome 206

Abstract: In this talk I will present a research paper that has been published in the Bulletin of the Hellenic mathematical society in December 2016.We will discuss the behavior of certain free abelian subgroups of the multiplicative group of positive rationals and their relationship with the group of units of integers modulo n.The methods we will use are purely algebraic.

Title:  Introduction of three models of price formation

Speaker: Chubo Deng

Date and Time: Friday, September 29 , 1:00-2:00pm

Place: Rome 206

Abstract: Based on the observations of the real world price formation process, I will introduce three models. One is from J.-M. Lasry and P.L.Lions evolution model. I modify their model to get other two which will be applied to the real world situation. I will use real Bitcoin chart to illustrate my idea.

Title:  Basic homological algebra and its application in knot theory.

Speaker: Xiao Wang, GWU

Date and Time: Friday, September 15, 1:00-2:00pm

Place: Rome 206

Abstract: I will first introduce projective resolution, Tor functor, and the Fundamental lemma of homological algebra.  Then we will see some applications of these basic homological algebra to Khovanov homology, which is a powerful link invariant that categorifies the Jones polynomial.

Title: Stable singularity formations in the nonlinear dispersive equations.

Speaker: Kai Yang, GWU

Date and Time: Friday September 22, 1pm-2pm

Place: Rome 206

Abstract: We will consider a couple of basic models used in dispersive (wave-type) differential equations and will address the question of formation of singularities (i.e., solutions that break down in finite time). These solutions are typically referred to blow-up solutions, since they tend to concentrate on some set (e.g. at a point) with amplitude or speed growing unboundedly. We study the case called the L2-critical case, which means that the solutions and the equations preserve the L2-norm, often referred as mass. We introduce the dynamic rescaling method to simulate the rate of blow-up solutions for the L2-critical nonlinear Schrodinger equation (NLS) as well as for the L2-critical generalized Hartree equation (gHartree). We study the solutions initiated from the radial data and consider dimensions from d=4 to d=12 for the NLS equation and from d=3 to d=7 for the gHartree equation. It turns out that the stable singularities have the blowup rate which can be expressed as (T-t)^{-0.5}, with a logarithmic corrections from analyzing the rescaled equations. We also provide a numerically-assisted proof of the spectral property for the NLS equation from d=4 to d=12, which confirms our direct computational results. In the gHartree case, we can only show the spectral property in the 3d radial case, as the spectral property of the nonlocal (convolution) nonlinearity is influenced significantly, and is harder to obtain both analytically and numerically.

Spring 2017







Title:  Long time behavior of solutions to the generalized Hartree equation

Speaker: Anudeep Kumar

Date and Time: Friday, April 28, 3:00-4:00pm

Place: Rome 352

Abstract: We study the long time behavior of solutions in the nonlinear dispersive equations, in particular, the generalized Hartree-type equation, where the potential is of nonlocal type and is expressed as a convolution. The behavior of solutions has been studied quite extensively for some basic model equations such as nonlinear wave equation and nonlinear Schr ̈odinger equation and various regimes were exhibited such as finite time existing solutions (or so called blow-up in finite time), or solutions existing globally in time: solitary waves or scattering (approaching linear solutions as → ±∞). In this talk we present small data theory, dichotomy for scattering versus blow-up, and criteria for solutions that blow-up in finite time with an emphasis on the method of concentration - compactness. 

Title: Pattern formation – on the modeling of multi-constituent inhibitory systems

Speaker: Chong Wang

Date and Time: TBA

Place: TBA

Abstract: Skin pigmentation, animal coats and block copolymers, which can be considered as multi-constituent inhibitory systems, are all around us. Theoretical analysis and numerical simulation of multi-constituent inhibitory systems will be provided here. An inhibitory system is studied as a nonlocal geometric variational problem. The free energy of the system is the sum of two terms: the total size of the interfaces separating the constituents, and a longer ranging interaction energy that inhibits micro-domains from unlimited growth. We establish that in different parameter ranges there are corresponding assemblies of certain patterns that exist as the stationary sets of the free energy functional. Numerically, a diffusive interface model is proposed and many self-assembly processes, which form various patterns, are vividly showed here. Different numerical schemes are compared and a new technique is introduced to be consistent with the Euler-Lagrange equation in the sharp interface model.

Title:   Topology and Computability of Order Relations on Some Algebraic Structures
Speaker:  Trang Ha, GWU
Date and Time: Friday, April 7, 3:00-4:00pm
Place: Rome 352

Abstract: We discuss order relations on computable magmas, which are computable algebraic structures with binary operations that are not necessarily associative or commutative. The space of orders on a magma consists of all possible orders (of a certain kind) on the structure. We investigate Turing complexity and topological properties of the spaces of orders on a computable magma. We also consider orderings on interesting examples of magmas that rises from algebra and knot theory such as quandles and racks.

TitlePriority Argument Constructions for Graphs and Trees
Speaker:Hakim Walker, GWU
Date and Time: Friday March 31, 3:00-4:00
Place: Rome 352

Abstract:  In computable model theory, we study the algorithmic content and properties of classical mathematical structures, such as groups, vector spaces, linear orders, etc. In particular, one area that we examine is the computational complexity of additional relations on the structures, as well as isomorphisms between structures. It is usually the case that while a structure itself is computable, additional relations on the structure are not computable. Also, we often have two computable structures that are isomorphic to each other but have no computable isomorphism between them. One of the most common ways to demonstrate these non-computable properties is to use a priority argument, which is a generalization of Cantor's diagonal argument.

In this talk, we will demonstrate both priority and non-priority arguments on a type of directed graph called a (2,1):1 structure, which consists of a countable set A together with a function f: A --> A such that every element has exactly one or exactly two pre-images under f. Both types of argument will allow us to build structures with various non-computable properties, but we will see that priority arguments are much more powerful and are often necessary to build more interesting examples and generalize results. 

TitleNumerical Investigations of Pattern Formation in Binary Systems with Inhibitory Long-range Interaction
Speaker:Jiajun Lu
Date and Time: Friday March 24, 3:00-4:00
Place: Rome 352

Abstract:  I investigate pattern formation in a two-phase system on a two-dimensional manifold by numerically computing the minimizers of a Cahn-Hilliard-like model for micro-phase separation of diblock copolymers. The total energy of the system includes a short-range term - a Landau free energy and a long-range term - the Otha-Kawasaki functional. The shortrange term favors large domains with minimum perimeter and the long-range inhibitory term favors small domains. The balance of these terms leads to minimizers with a variety of patterns, including single droplets, droplet assemblies, stripes, wriggled stripes and combinations thereof. I compare the results of our numerical simulations with known analytical results and discuss the stability of the computed solutions and the role of key parameters in pattern formation. I focus on the triaxial ellipsoid for demonstration purposes, but our methods are general and can be applied to higher genus surfaces and surfaces with boundaries.

Title: Comparative Genomics Meets Genome Assembly: from Ancestral Reconstruction to Genome Scaffolding
Speaker:Sergey Aganezov
Date and Time: Friday March 3, 3:00-4:00
Place: Rome 352


Abstract: We present our research that revolves around mathematical modeling and algorithms development in the area of computational biology, and more precisely, genome assembly as well as ancestral genome reconstruction and comparative genome rearrangement analysis. We start by demonstrating our results in the comparative genomics area by describing our work on the median problem of three genomes under the DCJ metric, as well as a more general problem of ancestral genome reconstruction of multiple input genomes. We then move to the problem of in silico genome scaffolding, where we present a novel method for for finishing incomplete genome assemblies and demonstrate the benefits of combining both areas of genome assembly and ancestral genome reconstruction. Lastly we present results of our work on the problem of comparing and merging of multiple scaffold assemblies of the same organisms.

Fall 2016


Title:  A tale of two theorems
Speaker: Professor Ted Turner
Date and Time: Friday September 93:00-4:00
Place: Philips 736  

Abstract: See attachment to email announcement 

Title:  Homological properties of algebraic structures arising from knot theory
SpeakerSujoy Mukherjee
Date and Time: Friday September 303:00-4:00
Place: Philips 736  

Abstract:  I will start with a brief introduction to knot theory. Following this I will discuss some well known knot invariants. Then I will show how to extract algebraic structures from Reidemeister moves. In particular, the third Reidemeister move leads to the notion of a shelf. After introducing the homology theories used to study these algebraic structures, I will discuss homological properties of associative shelves.

Title: Torsion in rack and quandle homology and its applications to Knot Theory  
Speaker Seung Yeop Yang
Date and Time: Friday October 73:00-4:00
Place: Philips 736  

Abstract: Rack homology theory was introduced between 1990 and 1995 by Fenn, Rourke, and Sanderson, and in 1999, Carter, Jelsovsky, Kamada, Langford, and Saito modified it to quandle homology theory in order to obtain knot invariants for classical knots and knotted surfaces in a state-sum form called cocycle knot invariants. In 1993, Fenn, Rourke, and Sanderson introduced rack spaces to define rack homotopy invariants and a modification to quandle spaces and quandle homotopy invariants of classical links was introduced by Nosaka in 2011.

In analogy to the well-known result in reduced group homology of finite groups that the order of a group annihilates its homology, we prove that the torsion subgroup of rack and quandle homology of a finite quasigroup quandle is annihilated by its order. It was an open conjecture for over 5 years. We also introduce an $m$-almost quasigroup quandle as a generalization of a quasigroup quandle and study annihilation of torsion in its rack and quandle homology groups. Moreover, as a generalization of rack and quandle spaces, we define the Cayley-type graph and CW complex of a distributive structure and study their properties. Moreover, for a connected quandle we introduce the shadow homotopy invariant of a classical link.

Title:  Computable Free Groups and Their Bases
SpeakerIva Bilanovic
Date and Time: Friday October 143:00-4:00
Place: Philips 736  

Abstract: In this talk we will consider the computability theoretic complexity of finding a basis for a computable free group of infinite rank. We will use basic properties of free groups to build a computable sequence of computable infinitary π2 formulas expressing the property of membership in a basis. The relativized limit lemma and these formulas will lead us to a π2 basis. 

Title:Global regularity of Patlak-Keller-Segel equations that model chemotaxis
SpeakerXinyu Zhang
Date and Time: Friday October 283:00-4:00
Place: Philips 736  

Abstract:  Chemotaxis is the means by which small organisms such as bacteria and somatic cells direct their movements towards or against the gradient of some chemical concentration. We will talk about the Patlak-Keller-Segel (PKS) equations in 2D that describe chemotaxis. We will also show that solutions with different mass sizes for PKS equations exhibit different behaviors.

Title:   Local and global existence of solution to Nonlinear Schrodinger's equation with mass-critical nonlinearity
Speaker: Debdeep Bhattacharya
Date and Time: Friday November 113:00-4:00
Place: Philips 736  

Abstract: We shall consider the nonlinear Schrodinger's equation with the power of nonlinearity being 1+4/n, where n is the dimension of the spacial variable. Using Strichartz's estimate and Banach's contraction mapping principle we shall prove the existence and uniqueness of the solution for finite time. Additionally, the solution exists for any time if we assume that the initial data has sufficiently small mass.

Title:  Global well-posedness for the critical 2D dissipative quasi-geostrophic equation. 
Speaker: Chubo Deng
Date and Time: Friday December 23:00-4:00
Place: Philips 736  

Abstract:  I will give an elementary proof of the global well-posedness for the critical 2D dissipative quasi-geostrophic equation. The argument is based on a non-local maximum principle involving appropriate moduli of continuity. 


Spring 2016

Title:  The Convenient Untruths of Economics and Finance

SpeakerHarbir Lamba, Department of Mathematical Sciences, George Mason University

Date and Time: Tuesday, April 26, 2:00-3:00pm

Place: Bell 105

Abstract: Modern economics and finance are based upon some highly

implausible (but extremely convenient) assumptions about how humans and institutions behave. For example, assuming that people can be modelled as if they are perfectly rational at all times, have no memory, and act independently of each other greatly simplifies the mathematics required!

I will talk about the (often amusing) history of these ideas and their (sometimes disastrous) consequences.  Then I will describe my own research which aims to mathematically describe what happens when these assumptions are weakened and replaced with more realistic ones via agent-based models.

Title:  Patten formation - solutions of some nonlocal variational problems

Speaker: Chong Wang

Date and Time: Friday, April 22, 1:00-2:00pm

Place: Government 101

Abstract: Skin pigmentation, animal coats and block copolymers, which can be considered as multi-constituent inhibitory systems, are all around us. An inhibitory system is studied as a nonlocal geometric variational problem. The free energy of the system is the sum of two terms: the total size of the interfaces separating the constituents, and a longer ranging interaction energy that inhibits micro-domains from unlimited growth. We will talk about the existence of a stationary core-shell assembly, and also a double bubble solution as a new phase of a ternary inhibitory system. If time allows, we can also discuss the local minimum solutions of the original problems before Gamma Convergence.

Title:  Minimal Surfaces and De Giorgi's Conjecture

Speaker: Yeyao Hu
Date and Time: Thursday, April 21, 3:00-4:00pm

Place: Corcoran 101

Abstract:  Attached in email announcement 4-15-2016

Title:  Mathematical models and algorithms for genome rearrangements and genome assembly

Speaker: Sergey Aganezov
Date and Time: Thursday, April 143:00-4:00pm

Place: Corcoran 101  

Abstract: My research revolves around mathematical modeling and algorithms development in the area of computational biology, and more precisely, genome assembly as well as ancestral genome reconstruction and comparative genome rearrangement analysis. The objective is to incorporate existing and develop new graph theoretical and combinatorial methods to tackle the problem of in silico finishing existing incomplete genome assemblies. We will cover the following topics: mathematical models of genomes rearrangements, various genome rearrangement distances (metrics) and their computational complexity, whole genome assembly, de novo / reference genome assembly, phylogenetic analysis of multiple genomes and quality improvement of existing genome assemblies by utilizing genome rearrangement analysis.

Title:  Yang-Baxter Operators and Knot Theory

Speaker: Xiao Wang
Date and Time: Thursday, April 7, 3:00-4:00pm

Place: Corcoran 101

Abstract:  Yang-Baxter Equation appears in several areas of physics( e.g.Statistical Mechanics, Quantum Theories).  It also gives applications to Knot Theory. I will introduce the Yang-Baxter Equation and its solutions.  Then I will show how to get link invariant from Yang-Baxter operators.  Finally, we define a homology theory for Yang-Baxter operators and have some discussion about it.

Title:  In pursuit of canonical structures on cellularly embedded graphs

Speaker: Jason Suagee
Date and Time: Thursday, March 24th, 3:00-4:00pm

Place: Corcoran 101

Abstract: In the mid 2000's Stephan Felsner (from TU Berlin) developed methods, given a planar embedded graph G, of associating a distributive lattice structure to the set of directed edge structures on G. This is now referred to as the theory of alpha-orientations, and can be used to derive canonical structures for any given planar embedded graph, in particular, canonical spanning trees and 2k factors. The theory has also been extended by several authors, who produce methods of bijectively constructing planar triangulations and several other families of planar maps, which are important for instance for 2D-Quantum Gravity simulations.

In this talk I will summarize Felsner's theory, and explain a recent generalization of his methods to the case of higher genus cellularly embedded graphs. I will also present a potential application to physics (in Quantum String Theory), which occurs though applying combinatorial methods to the theory of moduli spaces of complex curves, which are used to parameterize the functional integrals that govern the dynamics in string theory.

Note: The Graduate Student Seminar is mandatory for ALL graduate Students! Attendance will be taken.

TitleNumerical Minimizer of a Free Energy in Binary System

Speaker: Jiajun Lu Date and Time: Thursday, March 10, 3:00-4:00pm

Place: Corcoran 101

Abstract: Attached to Colloquium/Seminar weekly announcements

Note: The Graduate Student Seminar is mandatory for ALL graduate Students! Attendance will be taken.


SpeakerAnudeep Kumar

Date and Time: Thursday, March 3rd, 3:00-4:00pm

Place: Corcoran 101

Abstract: We study the long time behavior of solutions in the nonlinear dispersive equations, in particular, the generalized Hartree-type equation, where the potential is of nonlocal type and is expressed as a convolution. The behavior of solutions has been studied quite extensively for some basic model equations such as nonlinear wave equation and nonlinear Schr ̈odinger equation and various regimes were exhibited such as finite time existing solutions (or so called blow-up in finite time), or solutions existing globally in time: solitary waves or scattering (approaching linear solutions as t → ±∞). In this talk we present small data theory, dichotomy for scattering versus blow-up, and criteria for solutions that blow-up in finite time with an emphasis on  the method of concentration - compactness.

Note: The Graduate Student Seminar is mandatory for ALL graduate Students! Attendance will be taken.

Title: Finding the maximum genus of a graph – Topic in Topological graph theory

Speaker: Lara El-Sherif

Date and Time: Thursday, February 25th, 3:00-4:00pm

Place: Corcoran 101

Abstract: For any graph G and an orientable surface Sg (a surface of genus g), whether G can be cellularly embedded in Sg creates an interesting problem for many topological graph theorists. The “genus range” of a graph G, denoted GR(G) is defined to be the set of numbers g such that the graph G can be cellularly embedded in surface Sg. We call the minimum number g in the genus range, the “minimum genus” of G and the largest number in the range, the “maximum genus” respectively. Whereas the study of minimum genus dates back into the 19th century, interest in maximum genus began in the 1970’s. The main contributors to the theory behind finding the maximum genus of a graph are Xuong and Nebesky, among others. In this talk we will introduce the methods used by both Xuong and Nebesky in solving the maximum genus problem. We will also talk about the polynomial time algorithms available for finding a maximum genus embedding of a graph and the problems that lie in those algorithms.

Note: The Graduate Student Seminar is mandatory for ALL graduate Students! Attendance will be taken.

Title:  Behavior of solutions in the Nonlinear Klein-Gordon Equation

Speaker: Kai Yang

Date and Time: Friday, February 12th1:00-2:00pm

Place: Corcoran 101 Abstract:

Note: The Graduate Student Seminar is mandatory for ALL graduate Students! Attendance will be taken.  Also, please take note of the new day/old, Friday. 

Title:  How Complicated are Orderings on Computable Structures?

Speaker: Trang Ha Date and Time: Thursday, January 28th, 3:00-4:00pm

Place: Corcoran 101 Abstract:  A structure A is computable if it has the set of natural numbers N as its domain and all functions and relations on A are computable. We will examine some algebraic structures in this effective setting. Our main focus will be the complexities of orderings on these structures.

Note: The Graduate Student Seminar is mandatory for ALL graduate Students! Attendance will be taken.  Also, please take note of the new day, Thursday.

Title: Can Computers Do Anything?

Speaker: Leah Marshall
Date and Time: Thursday, January 21st3:00-4:00pm
Place: Corcoran 101
Abstract: [Spoiler Alert: the answer is... no.] In this talk I will give an overview of computability theory.  I will discuss the basic concepts and ideas of the field, the types of things we study, and give some fun examples of "computable" and "noncomputable" objects.  This talk should be accessible to all math graduate students.
Note: The Graduate Student Seminar is mandatory for ALL graduate students! 

Fall 2015

Title:  GTA Meeting


Speaker: Hakim Walker, George Washington University
Date and Time: Friday, November 20th1:00-2:00pm

Place: Monroe 267

Note: The Graduate Student Seminar is mandatory for ALL graduate **TAs**! Attendance will be taken.

Title: Stability analysis in a trend depending price formation model

Speaker: Chubo Deng
Date and Time: Friday, October 23rd1:00-2:00pm
Place: Government 101
Abstract: The model was first introduced by J-M Lasry and P.L. Lions., which describes the evolution of prices in a market. We discuss the eigenvalues and eigenfunctions for a one dimensional parabolic evolution equation with Neumann boundary condition. 
Note: The Graduate Student Seminar is mandatory for ALL graduate students! 

Title: Interior and Boundary Spikes for Two-dimensional GM system

Speaker: Yeyao Hu
Date and Time: Friday, October 9th1:00-2:00pm
Place: Government 101
Abstract: We prove the existence of an assembly of interior and boundary spikes as a solution of two-dimensional Gierer-Meinhardt system. Moreover, we also discover that the locations of the spikes are determined by the curvature of the domain boundary together with the Green’s function of the domain. A reflection operator of −∆ is introduced which also plays a very important in Ren and Shoup’s recent and upcoming papers.

Note: The Graduate Student Seminar is mandatory for ALL graduate students! 

Title: Introduction to Mathematica for Undergraduate and Graduate Students

Speaker: Robbie Robinson, George Washington University
Date and Time: Friday, September 25th1:00-2:00pm

Place: Government 101

Note: The Graduate Student Seminar is mandatory for ALL graduate students!  Attendance will be taken.

Title: A generalization of alpha-orientations to higher genus surfaces
Speaker: Jason Suagee, George Washington University
Date and Time: Friday, September 18th1:00-2:00pm

Place: Government 101

Abstract: Given a graph G=(V,E), and a given function alpha:V --> N, an alpha-orientation is an orientation of the edges such that the out-degree of each vertex v corresponds with alpha(v). S. Felsner (TU-Berlin) in 2006 proved that the set of alpha-orientation on an embedded planar graph (a planar map) carries the structure of a distributive lattice, with unique maximal and minimal elements. He uses this result, for example, to construct canonical spanning trees on rooted planar maps as well as several other canonical structures on planar maps.

We obtain a generalization of Felsner's result to higher genus orientable surfaces with possible application to bijective methods in map enumeration and construction. Additionally, by applying this result to pairs of Cayley maps (strongly symmetric embeddings of Cayley graphs) we obtain potential applications to the study of finite group extensions.

Note: The Graduate Student Seminar is mandatory for ALL graduate students!  Attendance will be taken.


Title: Computability-Theoretic Properties of (2,1):1 Structures
Speaker: Hakim Walker
Date and Time: Friday, September 11th1:00-2:00pm

Abstract: A (2,1):1 structure consists of a countable set A (usually the natural numbers) and a function f which maps, to each element of A, either exactly one element of A or exactly two elements of A. Similar structures have been studied recently by Harizanov, Cenzer, Remmel, and Marshall, particularly the complexity of isomorphisms between such structures. We will begin this talk with a brief overview of computability theory, then discuss some preliminary results, and conclude with an application to the Collatz conjecture.
Note: The Graduate Student Seminar is mandatory for ALL graduate students!