All Seminars

Title: Quantitative genetics of muscle mass loss - sarcopenia, the new epidemic in developed countries - there is no solution without mathematics
Chapter Talk: SIAM
Speaker: Gregory Livshits of Human Population Biology Research Unit, Sackler Faculty of Medicine, Tel Aviv University, Israel and Department of Twin Research and Genetic Epidemiology Division of Genetics and Molecular Medicine Ki
Contact: Raya Horesh, rshindm@emory.edu
Date: 2009-02-20 at 3:00PM
Venue: MSC W303
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Abstract:
Lean body mass (LBM) is one of the three major components of body composition, which includes also body fat (FBM) and bone mass (BBM). As the other two components it is highly important for normal physiology and metabolism, and deviations from normal values are often associated with various pathological conditions. Of these the major one is probably sarcopenia ? the age related loss of muscle mass. However, while for each of FBM and BBM, many dozens of publications concerning candidate genes, whole genome linkage and association studies were published during the last two decades, there are virtually no publications on LBM in this respect. Huge effort is now invested in creation of a large international consortium which will tackle this problem. The main aim of this talk will be twofold. One, it will be focused on the results of our genetic epidemiological study of LBM and sarcopenia in a normal human population. We present estimates of the putative genetic factors contribution and results of the whole genome linkage and association analyses. The second aim is to attract the mathematicians? attention to a number of difficult problems in which modern biology became engaged with unprecedented development of biotechnology and bioinformatics. This includes such ?classical? problems, inherited from whole genome linkage studies, as multiple testing adjustments and multiple signal combination, and relatively new problems as e.g. multiple low effect signals and their interactions and several others.
Title: Random Subgraphs of a Given Graph
Colloquium: N16
Speaker: Paul Horn of The University of California, San Diego
Contact: Dwight Duffus, dwight@mathcs.emory.edu
Date: 2009-02-19 at 3:00PM
Venue: MSC W303
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Abstract:
Data from real-world graphs often contains incomplete information, so we only observe subgraphs of these graphs. It is therefore desirable to understand how a typical subgraph relates to the underlying host graph. We consider several interrelated problems involving both random trees in host graphs and random subgraphs obtained by taking edges of the host graph independently with probability p. In the second case, we study the emergence of the giant component. We also use the spectral gap to understand discrepancy and expansion properties of a random subgraph. The Erdos-Renyi random graph is the special case of this where the host graph is the complete graph Kn. Additional applications include taking a contact graph as the host graph, and viewing random subgraphs as outbreaks of a disease.
Title: Counting points and doing integrals on Feynman diagrams
N16 Colloquium: Number theory
Speaker: Patrick Brosnan of University of British Columbia
Contact: Skip Garibaldi, skip@mathcs.emory.edu
Date: 2009-02-19 at 4:00PM
Venue: MSC W303
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Abstract:
Let $G$ be a finite connected graph with $E$ edges. The Kirchhoff polynomial of $P(G)$ is a certain homogeneous polynomial in $E$ variables whose degree is the first Betti number of the graph. These polynomials appeared classically in the study of electrical circuits (e.g., Kirchhoff's laws). They also appear in the evaluation of Feynman integrals. Motivated by computer calculations of D.~Kreimer and D.J.~Broadhurst associating multiple zeta values to certain Feynman integrals, Kontsevich conjectured that the number of zeros of $P(G)$ over a field with $q$ elements is a polynomial function of $q$. P.~Belkale and I disproved this conjecture by relating the schemes $V(P(G))$ to the representation spaces of certain combinatorial objects called matroids. I will discuss this work and subsequent work on the number-theoretical properties of Feynman amplitudes.
Title: Galois Theory and Patching
Colloquium: N/A
Speaker: David Harbater of University of Pennsylvania
Contact: R. Parimala, parimala@mathcs.emory.edu
Date: 2009-02-17 at 4:00PM
Venue: W306
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Title: The profile of bubbling solutions of a class of fourth order geometric equations on 4-manifolds
Seminar: Analysis and Differential Geometry
Speaker: Professor Lei Zhang of Univ. of Alabama at Birmingham
Contact: Vladimir Oliker, oliker@mathcs.emory.edu
Date: 2009-02-17 at 4:00PM
Venue: MSC W301
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Abstract:
Abstract. We study a class of fourth order geometric equations defined on a 4-dimensional compact Riemannian manifold which includes the Q-curvature equation. We obtain sharp estimates on the difference near the blow-up points between a bubbling sequence of solutions and the standard bubble.
Title: Arithmetic of del Pezzo surfaces of degree 1
Colloquium: N16
Speaker: Tony Varilly of The University of California, Berkeley
Contact: Dwight Duffus, dwight@mathcs.emory.edu
Date: 2009-02-13 at 4:00PM
Venue: W306
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Abstract:
I will discuss some of the driving questions in the area of Rational points on algebraic varieties (these can be thought of as solutions over fields of number-theoretic interest to systems of homogeneous polynomial equations). I will focus on the case of smooth rational surfaces, and discuss some results concerning the arithmetic of del Pezzo surfaces of degree 1. I will also explain how these results complete a qualitative picture of basic arithmetic phenomena among smooth rational surfaces. Along the way I will go over concepts like weak approximation and the computation of Brauer-Manin obstructions; I will not assume previous knowledge of them.
Title: Negative Correlation Inequalities
Colloquium: N16
Speaker: Mike Neiman of Rutgers University
Contact: Dwight Duffus, dwight@mathcs.emory.edu
Date: 2009-02-11 at 3:00PM
Venue: MSC W303
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Abstract:
Correlation inequalities are statements about how events in a probability space positively or negatively reinforce each other. After briefly discussing the better-understood theory of positive correlation, I will talk about some negative correlation inequalities and their relationship to celebrated conjectures of J. Mason about log-concavity properties of certain sequences arising from combinatorial objects. Along the way, I'll mention several interesting open problems.
Title: Number Theory and a Lower Bound for Closed Geodesics, Part 2
Seminar: Topology
Speaker: Sean Thomas of
Contact: Emily Hamilton, emh@mathcs.emory.edu
Date: 2009-02-10 at 3:00PM
Venue: MSC E406
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Abstract:
Lehmer's conjecture (1933) states that the Mahler measure of an algebraic number that is not a root of unity is bounded away from 1. The aim of the seminar is to show the conjecture would imply there is a positive lower bound for closed geodesics in compact arithmetic hyperbolic 3-manifolds of finite volume. In the first lecture, I will introduce the necessary background material on arithmetic hyperbolic 3-manifolds. Then, in the second lecture, I will show how Lehmer's conjecture would imply the existence of the aforementioned positive lower bound. Also, I will prove the existence of a positive lower bound for closed geodesics in non-compact arithmetic hyperbolic 3-manifolds of finite volume to fully address the topic.
Title: Number Theory and a Lower Bound for Closed Geodesics
Seminar: Topology
Speaker: Sean Thomas of Emory University
Contact: Sean Thomas, sean.thomas@emory.edu
Date: 2009-02-03 at 3:00PM
Venue: MSC E406
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Abstract:
Lehmer's conjecture (1933) states that the Mahler measure of an algebraic number that is not a root of unity is bounded away from 1. The aim of the seminar is to show the conjecture would imply there is a positive lower bound for closed geodesics in compact arithmetic hyperbolic 3-manifolds of finite volume. In the first lecture, I will introduce the necessary background material on arithmetic hyperbolic 3-manifolds. Then, in the second lecture, I will show how Lehmer's conjecture would imply the existence of the aforementioned positive lower bound. Also, I will prove the existence of a positive lower bound for closed geodesics in non-compact arithmetic hyperbolic 3-manifolds of finite volume to fully address the topic.
Title: Quasiconformal mappings and some extremal problems
Seminar: Analysis and Differential Geometry
Speaker: Professor Zemin Zhou of Renmin University of China
Contact: Shanshuang Yang, syang@mathcs.emory.edu
Date: 2009-02-03 at 4:00PM
Venue: MSC W301
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Abstract:
In this talk we will present some progress on several extremal problems related to quasiconformal mappings and Beltrami coefficients on the unit disk.