{"id":37,"date":"2016-01-06T13:05:39","date_gmt":"2016-01-06T18:05:39","guid":{"rendered":"https:\/\/my.vanderbilt.edu\/pastcolloquia\/?page_id=37"},"modified":"2016-01-06T13:05:39","modified_gmt":"2016-01-06T18:05:39","slug":"colloquia-spring-2000","status":"publish","type":"page","link":"https:\/\/my.vanderbilt.edu\/pastcolloquia\/colloquia-spring-2000\/","title":{"rendered":"Colloquia, Spring 2000"},"content":{"rendered":"<table width=100% cellpadding=5 cellspacing=0 bgcolor=\"#780020\">\n<tr>\n<td width=95%>\n<table width=100% cellpadding=5 cellspacing=0 border=0 bgcolor=black>\n<tr>\n<td width=5%><img SRC=\"http:\/\/www.math.vanderbilt.edu\/images\/mathlogo.gif\" hspace=15 vspace=15\/><\/td>\n<td bgcolor=black width=95%>\n<center><\/p>\n<h1><font face=\"times new roman\"><a HREF=\"http:\/\/www.math.vanderbilt.edu\/\"><font size=4><\/font><font color=gold>Vanderbilt Mathematics<\/font><\/a><\/font><br \/>\n<font size=7><\/font><font color=gold>Colloquia<\/font><br \/>\n<font size=4><\/font><font color=gold>Spring 2000<\/font><\/h1>\n<p><\/center>\n<\/td>\n<\/tr>\n<\/table>\n<\/td>\n<\/tr>\n<\/table>\n<p><font face=\"times new roman\"><\/p>\n<p>\nJuly  27.<br \/>\nEdray Goins, of the<br \/>\n<a href=\"http:\/\/www.math.ias.edu\/\">Institute<br \/>\nfor Advanced Study, School of Mathematics<\/a>.<br \/>\n<b>On the Multiplicative Properties of the Sums of Squares.<\/b><br \/>\nThe product of any two integers which are sums of two<br \/>\nsquares is again the sum of two squares, and, similarly, the product of<br \/>\nany two integers which are sums of four squares is again the sum of<br \/>\nfour squares.  We give some thoughts on where these formulas come<br \/>\nfrom; we also discuss the multiplicative properties of the polynomials<br \/>\n<i>ax<\/i><sup>2<\/sup>+<i>bxy<\/i>+<i>cy<\/i><sup>2<\/sup><br \/>\nby considering the product of three integers<br \/>\nexpressed in such a form.  &#8212;<br \/>\nThis talk will be elementary and accessible to undergraduates.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>May 16. <a href=\"http:\/\/www.wits.ac.za\/science\/number_theory\/dslcvnew.htm\">Doron<br \/>\nLubinsky<\/a>, of the<br \/>\n<a href=\"http:\/\/www.wits.ac.za\/science\/maths\/index.html\">University<br \/>\nof Witwatersrand<\/a>,<br \/>\nJohannesburg, South Africa.<br \/>\n<b>A Pade Look at Continued Fractions: Some old, some new.<\/b><br \/>\nEvery formal power series admits a formal continued fraction<br \/>\nexpansion. This is the function theoretic analogue of the continued<br \/>\nfraction expansion of a positive real number. We discuss why they<br \/>\nare of practical and theoretical interest.<br \/>\n&#8212;    The convergents to the continued fraction are also Pade<br \/>\napproximants, and we examine the convergence of the continued<br \/>\nfraction from a Pade perspective. In particular, we survey old and<br \/>\nnew convergence results, and the status of the Baker-Gammel-Wills<br \/>\nConjecture. Will it be killed by Ramanujan&#8217;s continued fraction?<br \/>\n<!-- 4:10-5:00, Room SC-1431. Refreshments afterward in SC-1425.-->\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>May 12.<br \/>\nQuintang Jiang,<br \/>\nof the<br \/>\n<a HREF=\"http:\/\/www.math.ualberta.ca\/\">University of Alberta<\/a>.<br \/>\n<b>The Design of Multiwavelets with Optimum Time-Frequency<br \/>\nResolution.<\/b><br \/>\nIn this talk first we will discuss the procedure to design<br \/>\northogonal multiwavelets with good time-frequency resolution.<br \/>\nNext, we give formulas to compute the time-durations and<br \/>\nthe frequency-bandwidths of scaling functions and multiwavelets.<br \/>\nLater on we discuss the parameterization of symmetric orthogonal<br \/>\nmultifilter banks. Finally, we show some results of image<br \/>\ncompression with the optimal multiwavelets.<br \/>\n<!-- 4:10 pm, room SC-1431.\nRefreshments afterward in SC-1425.-->\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>May 4.<br \/>\n<a href=\"http:\/\/www.math.sci.hiroshima-u.ac.jp\/fa\/\">Shinnosuke<br \/>\nOharu<\/a>, of<br \/>\n<a href=\"http:\/\/www.math.sci.hiroshima-u.ac.jp\/\">Hiroshima University<\/a>.<br \/>\n<b>Continuous and discrete models of phenotype evolution in<br \/>\nthe ecosystem of red tide plankton.<\/b><br \/>\nHeterocapsa circularisquama are vegetative<br \/>\nplankton and form red tides because of active<br \/>\nproliferation in summer. Such red tides cause<br \/>\nmass mortality of bivalves. The coastal ocean is<br \/>\nconsidered complex multi-component fluid in<br \/>\nwhich the ecology of Heterocapsa is supported<br \/>\nby other living things and the physical states<br \/>\ndepending strongly upon seasonal variations of<br \/>\nair-sea interactions, weather, water temperature,<br \/>\nsalinity and water currents. Therefore it is not<br \/>\nstraightforward to elucidate the ecosystem of<br \/>\nHeterocapsa in the ocean from the point of view<br \/>\nof a sole field of biology as well as other separate<br \/>\nfields of natural science.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>April 27.<br \/>\n<a href=\"http:\/\/www.latech.edu\/~schroder\/\">Bernd Schroeder<\/a>, of<br \/>\n<a href=\"http:\/\/www.math.latech.edu\/\">Louisiana<br \/>\nTech University<\/a>.<br \/>\n<b>Using probabilistic formulas to predict the behavior of<br \/>\nsearch algorithms.<\/b><\/p>\n<p>Many problems in mathematics and in applications can be<br \/>\nformulated as constraint satisfaction problems. Among these<br \/>\nproblems are the question if a given ordered set has a fixed point<br \/>\nfree self-map, the question if a graph has a Hamiltonian Cycle,<br \/>\nthe n-queens problem, scheduling problems, etc. In particular,<br \/>\nconstraint satisfaction problems (we will give a general definition)<br \/>\nare NP-complete and thus any known solution procedure<br \/>\npotentially requires exponential effort. &#8212;<br \/>\nThe standard search algorithms that are used to solve such problems<br \/>\nare backtracking and forward checking. In addition to these main<br \/>\nparadigms there are refinements of each algorithm, which may<br \/>\nhave shorter search times. The problem now is that if a constraint<br \/>\nsatisfaction problem is presented, one would like to know in advance<br \/>\nwhich algorithm is the fastest to solve the problem. In this fashion<br \/>\none could automatically choose the &#8220;right&#8221; algorithm and save<br \/>\ncomputation time. &#8212;<br \/>\nThere are many approaches to this idea. The three main approaches<br \/>\nthe speaker is aware of are<\/p>\n<ul>\n<li>Theoretical hierarchies that show one algorithm to be preferable for<br \/>\n  certain types of problems,\n<\/li>\n<li>Heuristic analysis of the search trees that leads to estimates of the<br \/>\n  run time, and\n<\/li>\n<li>Probabilistic analysis of the constraint network, which also leads<br \/>\n  to estimates of the run time.\n<\/li>\n<\/ul>\n<p>In this talk we will focus on the probabilistic analysis of the constraint<br \/>\nnetwork and how it can be used to predict search time. The probabilistic<br \/>\nanalysis would also allow us to give an estimate how likely it is that the<br \/>\nproblem has a solution at all. &#8212;<br \/>\nWe will exhibit the ideas behind a probabilistic analysis, the need to<br \/>\ngeneralize these ideas and combine them with heuristic (or other)<br \/>\nanalysis of related problems and some experimental data on randomly<br \/>\nseeded constraint satisfaction problems using different seeding mechanisms.<br \/>\nThe talk connects Mathematics and Computer Science and should be<br \/>\nunderstandable to graduate and advanced undergraduate students in<br \/>\neither field.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>April 21.<br \/>\n<a href=\"http:\/\/www.math.wisc.edu\/~angenent\/\">Sigurd Angenent<\/a>,<br \/>\nof the<br \/>\n<a href=\"http:\/\/www.math.wisc.edu\/\">University of Wisconsin, Madison<\/a>.<br \/>\n<b>Knot types of Closed Geodesics on surfaces via Curve Shortening.<\/b><br \/>\nClosed Geodesics on two dimensional surfaces trace out curves<br \/>\nwhich look like knot projections. One can ask which particular knot<br \/>\nprojections must  occur for a given metric, and it turns out that Curve<br \/>\nShortening (a nonlinear heat equation) allows one to give a partial answer<br \/>\nto this question. In particular one can prove a global version of the<br \/>\nPoincare Birkhoff thoerem for area preserving twistmaps.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>April 13.<br \/>\n<a HREF=\"http:\/\/www.math.ualberta.ca\/People\/Facultypages\/Jia.R.html\">Rong-Qing Jia<\/a>, of<br \/>\n<a HREF=\"http:\/\/www.math.ualberta.ca\/\">University of Alberta<\/a>.<br \/>\n<b>Wavelet Frames Generated by Multiresolution Analysis.<\/b><br \/>\nA multiresolution of the space of square integrable functions consists<br \/>\nof a family of scaled shift-invariant subspaces. The difference of two<br \/>\nconsecutive shift-invariant subspaces is generated by a finite number of<br \/>\nwavelets. Under a very mild condition we show that these wavelets generate<br \/>\nan affine frame for the whole space. Our results are based on a study of<br \/>\ndual wavelet frames with compact support.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>April 11.<br \/>\n<a href=\"http:\/\/www.math.vanderbilt.edu\/faculty\/Arenstorf.html\">Richard<br \/>\nArenstorf<\/a>,<br \/>\nProfessor Emeritus at Vanderbilt University.<br \/>\n<b> A Representation of the Riemann Zeta Function in Terms of<br \/>\nParabolic Cylinder Functions.<\/b>\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>April 7. <a href=\"mailto:kryakin@paco.net\">Yurij Kryakin<\/a>, of <a href=\"http:\/\/www.imem.odessa.ua\/index2.htm\">Odessa State  Polytech<br \/>\nUniversity (I.I. Mechnikov, Institute of Mathematics, Economics and<br \/>\nMechanics)<\/a>, Ukraine, and<br \/>\n<a href=\"http:\/\/www.adm.uni.wroc.pl\/BAZA_A.HTM\">University<br \/>\nof Wroclaw<\/a>, Poland.<br \/>\n<b>Local approximation by polynomials.<\/b><br \/>\nThe remarkable Whitney Theorem states that for each continuous on  [0,1]<br \/>\nfunction  f(x)  there exists an algebraic polynomial of degree at most<br \/>\nn-1   such that the uniform norm of difference  |f(x)&nbsp;&#8211;&nbsp;P(x)|<br \/>\nis dominated by the norm of  nth divided differences with<br \/>\nsome constant  W(n)   for  n=1,2,&#8230;.  &#8212;<br \/>\nSince 1957, a lot of research was done on estimating  the values of<br \/>\nW(n). However, at the moment only  asymptotic behaviors and exact<br \/>\nvalues for  n&lt;3   are known.<br \/>\nRecent  progress in estimating of  W(n)  is connected with the<br \/>\nspecial methods of approximations (&#8220;approximation on the average&#8221;).<br \/>\nThe current status of the problem, open questions and the applications in<br \/>\nApproximation Theory, will be discussed.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>April 6.<br \/>\n<a HREF=\"http:\/\/www.math.uiowa.edu\/~jorgen\/\">Palle Jorgensen<\/a>, of<br \/>\n<a HREF=\"http:\/\/www.math.uiowa.edu\/\">University of Iowa<\/a>.<br \/>\n<b>Construction of new wavelet filters, and their classification.<\/b><br \/>\nIt is well known that wavelet filters satisfy a set of algebraic axioms, but<br \/>\nthere aren&#8217;t so far systematic ways of constructing examples that are dictated<br \/>\nby applications.  Also when examples are constructed, it is often not clear<br \/>\nwhether they are minimal. If they are given by a system of numbers, are there<br \/>\nredundancies, and can a given example be further decomposed in elementary<br \/>\n&#8220;building blocks&#8221;. We first describe all the wavelet filters as a certain<br \/>\ninfinite-dimensional unitary group, and we describe how that is effective in<br \/>\nconstructing new examples, for example getting high-pass filters consistent<br \/>\nwith a given low pass filter. We also provide a harmonic analysis which<br \/>\nresolves the question of equivalence, and elementary building blocks,<br \/>\nmaking precise the notion of irreducible cases. The theory will apply also<br \/>\nto scaling in several dimensions.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>March 30.<br \/>\nSongmu Zheng, of the<br \/>\n<a href=\"http:\/\/www.math.umn.edu\/\">University of Minnesota<\/a>.<br \/>\n<b>Maximal Attractors for Some Nonlinear PDEs.<\/b><\/p>\n<p>In this talk I will report some recent progress in the study of the dynamics<br \/>\nfor some nonlinear partial differential equations, including the coupled<br \/>\nCahn-Hilliard equations, the phase-field equations of Penrose-Fife type arising<br \/>\nfrom the study of phase transitions, and also the system of nonlinear PDEs<br \/>\ndescribing the motion of a one-dimensional viscous and heat-conductive ideal<br \/>\ngas.  These problems have the following new features regarding their dynamics:<\/p>\n<ol>\n<li>The metric spaces we work with are incomplete, as can be seen from<br \/>\nthe constraint <font face=symbol>q<\/font>&gt;0 with  <font face=symbol>q<\/font> being the absolute temperature, or<br \/>\n<i>u<\/i>&nbsp;&gt;&nbsp;0 with <i>u<\/i> being the specific volume.\n<\/li>\n<li>There are some conservation laws for these problems, i.e., conservation<br \/>\nof mass, conservation of energy, etc. It turns out that there is no global<br \/>\ncompact attractor for each of these problems when the initial data vary in the<br \/>\n<i>whole space<\/i>, and we have to restrict ourselves to subspaces characterized<br \/>\nby a sequence of parameters.  Of course, the immediate question is how to<br \/>\ndefine these subspaces for these coupled systems of quasilinear PDEs.\n<\/li>\n<li>It is well-known that in order to prove existence of a maximal compact<br \/>\nattractor, one of the major steps is to prove existence of an absorbing set or<br \/>\nan absorbing ball whose size should be <i>independent of the initial data<\/i>.<br \/>\nTo do so, one usually tries to derive the following type of differential<br \/>\ninequality:<br \/>\n<center><br \/>\n<i>dE<\/i>\/<i>dt<\/i>&nbsp;+&nbsp;<i>C<sub>1<\/sub>E(t)<\/i>&nbsp;<font face=symbol>&#163;<\/font>&nbsp;<i>C<\/i><sub>2<\/sub>,<br \/>\n<\/center><br \/>\nwith <i>E<\/i> being a certain Sobolev norm of the solution, and with<br \/>\n<i>C<\/i><sub>1<\/sub>, <i>C<\/i><sub>2<\/sub><br \/>\nbeing two positive constants <i>independent of the initial data<\/i>.  If such a<br \/>\ndifferential inequality is available, then existence of an absorbing ball<br \/>\nimmediately follows.  However, since all these three systems are quasilinear,<br \/>\nit does not seem feasible to derive such a type of differential inequality.\n<\/li>\n<\/ol>\n<p>In this talk I will present a new approach to deal with the above<br \/>\ndifficulties. Then we will focus our attention to the coupled<br \/>\nCahn-Hilliard equations and show that for any given constants <font face=symbol>b<\/font><sub>1<\/sub>&nbsp;&gt;&nbsp;0,<br \/>\n<font face=symbol>b<\/font><sub>2<\/sub>, a<br \/>\nsequence of closed subspaces<br \/>\n<b><i>U<\/i><\/b>(<font face=symbol>b<\/font><sub>1<\/sub>,<font face=symbol>b<\/font><sub>2<\/sub>) is found, and the existence of a compact<br \/>\nmaximal attractor in <b><i>U<\/i><\/b>(<font face=symbol>b<\/font><sub>1<\/sub>,<font face=symbol>b<\/font><sub>2<\/sub>) is proved.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>March 28.<br \/>\n<a href=\"http:\/\/www.lafayette.edu\/~smithder\">Derek Smith<\/a>,<br \/>\nof<br \/>\n<a href=\"http:\/\/www.lafayette.edu\/~math\/mathhome.html\">Lafayette College<\/a>.<br \/>\n<b>Factorization in the Composition Algebras.<\/b><br \/>\nThis broadly-accessible talk will present some arithmetical and geometrical<br \/>\nresults concerning the composition algebras, including new results based on a<br \/>\nnonassociative factorization algorithm appropriate for computations involving<br \/>\nthe integral octonions.  After introducing the composition algebras and some of<br \/>\ntheir geometrical properties, I will focus on the problem of understanding and<br \/>\ndescribing the factorizations of elements within certain rings of integers in<br \/>\nthese algebras.  In particular, if <i><b>O<\/b><\/i> is a maximal set of integers<br \/>\nin<br \/>\na composition algebra and<br \/>\n<font face=symbol>r<\/font>&nbsp;<font face=symbol>&#206;<\/font>&nbsp;<i><b>O<\/b><\/i><br \/>\nhas norm [<font face=symbol>r<\/font>] = m.n, I<br \/>\nwill present an algorithm that leads to a precise geometrical description of<br \/>\nthe set of all factorizations of<br \/>\n<font face=symbol>r<\/font><br \/>\nas <font face=symbol>r<\/font>&nbsp;=&nbsp;<font face=symbol>ab<\/font>, where<br \/>\n[<font face=symbol>a<\/font>]&nbsp;=&nbsp;m and<br \/>\n[<font face=symbol>b<\/font>]&nbsp;=&nbsp;n.<br \/>\n(Part of this work is joint with J. H.<br \/>\nConway.)\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>March 22.<br \/>\nLaci Lovasz, of<br \/>\n<a href=\"http:\/\/www.research.microsoft.com\/\">Microsoft Research<\/a>.<br \/>\n<b>Critical graphs and facets of the<br \/>\nstable set polytope.<\/b><br \/>\nA graph is called <i>alpha-critical<\/i><br \/>\nif deleting any edge<br \/>\nincreases the number of independent nodes. Such graphs<br \/>\nhave a very nice and tight structure, which was studied<br \/>\nin detail in the 70&#8217;s. Another important notion is the stable<br \/>\nset polytope, the convex hull of incidence vectors of<br \/>\nindependent sets of nodes. &#8212;<br \/>\nThe starting point of this talk is the fact that<br \/>\nalpha-critical graphs give rise to facets of the stable set<br \/>\npolytope, and that several of their basic properties<br \/>\ncan be generalized to facets. In particular, a known<br \/>\nclassification of alpha-critical graphs with fixed &#8220;defect&#8221;<br \/>\nleads to a classification of facets with fixed<br \/>\n&#8220;integrality gap.&#8221; &#8212;<br \/>\nThe talk will survey the theory of alpha-critical graphs,<br \/>\nand then the new results on facets, which are joint work<br \/>\nwith L&aacute;szl&oacute; Liptak.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>March 16.<br \/>\n<a href=\"http:\/\/www.math.ohiou.edu\/math\/faculty\/gulisashvili.html\">Archil<br \/>\nGulisashvili<\/a>, of <a href=\"http:\/\/www.math.ohiou.edu\/math\/\">Ohio University<\/a>.<br \/>\n<b>On the heat equation with a time-dependent potential.<\/b><br \/>\nThe initial value problem for the heat equation with a<br \/>\ntime dependent potential describes the time-evolution of<br \/>\nsome quantity, diffusing in <b>R<\/b><sup><i>n<\/i><\/sup> in the presence of<br \/>\ntime-dependent sources and sinks.  We will discuss the<br \/>\nweak solvability problem for the heat equation with a<br \/>\npotential, the smoothing properties of the weak propagator,<br \/>\nand the integral representation formulas for the solutions,<br \/>\nincluding the celebrated Feynman-Kac formula.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>March 15.<\/p>\n<p><a HREF=\"http:\/\/www.uni-giessen.de\/www-Numerische-Mathematik\/davydov\/index_e.html\">Oleg Davydov<\/a>,<br \/>\nof the<br \/>\n<a HREF=\"http:\/\/www.uni-giessen.de\/www-Mathematik\/index_en.html\">University of Giessen, Germany<\/a>.<br \/>\n<b>Smooth Piecewise Polynomial<br \/>\nMultiresolution Analysis on Irregular Triangulations.<\/b><\/p>\n<p>Both hierarchical bases and wavelets  have as a prerequisite<br \/>\na multiresolution analysis on the underlying nested sequence of<br \/>\ntriangulations.   The spaces of<br \/>\npiecewise polynomials are a natural tool for the construction of the<br \/>\nmultiresolution analysis. In particular, if the bases are only required<br \/>\nto be continuous,  usual finite-element spaces can be used.<br \/>\nIn contrast to this,  smooth conforming finite elements, such as Argyris<br \/>\nelement, are not suitable due to the fact that the corresponding spaces of<br \/>\npiecewise polynomials are not nested.<\/p>\n<p>&nbsp;&nbsp;&nbsp;&#8212;&nbsp;&nbsp;&nbsp;<\/p>\n<p>The idea to make use of<br \/>\nthe basis of the full  space of <i>C<\/i><sup>1<\/sup>-splines<br \/>\n<i>S<sub>d<\/sub><\/i><sup>1<\/sup>(<font face=symbol>D<\/font>) instead is<br \/>\ndue to Dahmen, Oswald &amp; Shi (1994). However, the Morgan-Scott basis<br \/>\nfor <i>S<sub>d<\/sub><\/i><sup>1<\/sup>(<font face=symbol>D<\/font>)<br \/>\nused in their work appears to be instable<br \/>\nif the triangulations have so-called near-degenerate edges and<br \/>\nnear-singular vertices. Therefore, the triangulation has to be refined<br \/>\nin such a way (e.g., uniformly) that these geometrical configurations do not<br \/>\nappear.<\/p>\n<p>&nbsp;&nbsp;&nbsp;&#8212;&nbsp;&nbsp;&nbsp;<\/p>\n<p>We discuss a recent construction (joint work with L.&nbsp;L.&nbsp;Schumaker)<br \/>\nof a stable local basis for <i>C<\/i><sup>1<\/sup> and, more general,<br \/>\n<i>C<sup>r<\/sup><\/i>-splines, <i>r<\/i><font face=symbol>&#179;<\/font>1,<br \/>\nwhich can be used to build stable multiresolution<br \/>\nanalyses on arbitrary nested sequences of triangulations, with the only<br \/>\nrestriction that the smallest angle of the triangles is controlled.<br \/>\nIn particular, this construction applies to adaptively refined<br \/>\ntriangulations.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>February 17.<br \/>\nQiyu Sun, of the<br \/>\n<a HREF=\"http:\/\/www.math.nus.edu.sg\/\">National University of Singapore<\/a>.<br \/>\n<b>Finitely Generated Shift-Invariant Spaces.<\/b><br \/>\nFor any vector-valued compactly supported function<br \/>\n<font face=symbol>F<\/font>&nbsp;=&nbsp;(<font face=symbol>f<\/font><sub>1<\/sub>,&#8230;<br \/>\n<font face=symbol>f<\/font><sub><i>r<\/i><\/sub>)<sup><i>T<\/i><\/sup>,<br \/>\ndefine the corresponding semi-convolution<br \/>\n<font face=symbol>F<\/font><sub>*<\/sub><font face=symbol>&#162;<\/font> on<br \/>\n(<i>l<\/i>)<sup><i>r<\/i><\/sup> by<br \/>\n<center><img SRC=\"00_02_17.gif\" ALT=\"[insert equation here]\"\/><\/center><br \/>\nLet <i>V<sub>p<\/sub><\/i>(<font face=symbol>F<\/font>),<br \/>\n1&nbsp;<u>&lt;<\/u>&nbsp;<i>p<\/i>&nbsp;<u>&lt;<\/u>&nbsp;<font face=symbol>&#165;<\/font>, and<br \/>\n<i>V<\/i>(<font face=symbol>F<\/font>) be the images of<br \/>\nthe semi-convolution operator<br \/>\n<font face=symbol>F<\/font><sub>*<\/sub><font face=symbol>&#162;<\/font><br \/>\nrestricted to<br \/>\n(<i>l<sup>p<\/sup><\/i>)<sup><i>r<\/i><\/sup><br \/>\nand<br \/>\n(<i>l<\/i>)<sup><i>r<\/i><\/sup> respectively.<br \/>\nIn this talk, we shall discuss the annihilator<br \/>\nof the kernel of the semi-convolution operator<br \/>\n<font face=symbol>F<\/font><sub>*<\/sub><font face=symbol>&#162;<\/font>, and the recovery of functions in<br \/>\n<i>V<sub>p<\/sub><\/i>(<font face=symbol>F<\/font>) and<br \/>\n<i>V<\/i>(<font face=symbol>F<\/font>) under<br \/>\nsome linear independent, stable or frame conditions on<br \/>\n<font face=symbol>F<\/font>.  For simplicity, we restrict<br \/>\nourselves to one dimensional case, all results presented<br \/>\nin the talk can be generalized to higher dimensions.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>January 27.<br \/>\n<a href=\"http:\/\/www.math.nwu.edu\/faculty\/homepages\/emmanuele.dibenedetto.html\">Emmanuele<br \/>\nDiBenedetto<\/a>, of<br \/>\n<a href=\"http:\/\/www.math.nwu.edu\">Northwestern University<\/a>.<br \/>\n<b>On the local behavior of solutions of some<br \/>\ndegenerate\/singular parabolic equations.<\/b><br \/>\nModels of flow of multiple immiscible fluids in a<br \/>\nporous matrix and\/or phenomena of multiple transitions of<br \/>\nphase, result into quasi-linear parabolic equations, with<br \/>\nmeasurable coefficients and exhibiting multiple<br \/>\nsingularities and\/or degeneracies. &#8212;<br \/>\nI will discuss the problem of the continuity of the<br \/>\ntransition parameters, for example saturation in the<br \/>\nflow of immiscible fluids or temperature in isothermal<br \/>\nphase transitions. &#8212;<br \/>\nWe review and summarize the main points of the<br \/>\ntheory and will present some recent results in this<br \/>\ndirection, pointing to the new mathematical tools<br \/>\ngenerated by these investigations.\n<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>January 17.<br \/>\n<a href=\"http:\/\/www.math.vanderbilt.edu\/~pjipsen\/\">Peter Jipsen<\/a>, of<br \/>\n<a href=\"http:\/\/www.mth.uct.ac.za\/\">University<br \/>\nof Cape Town<\/a> and Vanderbilt University.<br \/>\n<b>Computer assisted research in universal algebra and logic.<\/b><br \/>\nIn this talk I will present some of the tools that I have used<br \/>\nin my research and discuss some of the results that have been proved using<br \/>\nthem. In the first part I will consider general purpose tools that are<br \/>\ncurrently available for mathematical research, such as<br \/>\nautomated\/interactive theorem provers and computer algebra packages. After<br \/>\na few examples illustrating their use in recent research topics, I will<br \/>\nexamine some special purpose algorithms and approaches in universal<br \/>\nalgebra and logic that I have used over the past decade (e.g. searching<br \/>\nfor finite algebras, completing partial algebras and sandwich structures,<br \/>\nsearching for winning strategies in logical games, calculating free<br \/>\nalgebras in finitely generated varieties).  If time permits, I will<br \/>\ndemonstrate a few programs that I have written.<\/p>\n<p>&nbsp;&nbsp;&nbsp;<\/p>\n<p>January 12.<br \/>\n<a href=\"http:\/\/www.math.umn.edu\/~edelman\/\">Paul Edelman<\/a>, of the<br \/>\n<a href=\"http:\/\/www.math.umn.edu\">School of Mathematics, University of Minnesota<\/a>.<br \/>\n<b>The Poset of Cellular Strings of a Polytope.<\/b><br \/>\nLet <i>P<\/i> be a polytope and <i>l<\/i> a linear functional that takes on distinct<br \/>\nvalues on the vertices of <i>P<\/i>.   A monotone path in <i>P<\/i> (with respect to <i>l<\/i>)<br \/>\nis a sequence of vertices such that<\/p>\n<ol>\n<li>Consecutive vertices lie on an edge of <i>P<\/i>,\n<\/li>\n<li>The  first and last vertex in the sequence are minimal and maximal with<br \/>\nrespect  to <i>l<\/i>, respectively,  and\n<\/li>\n<li>The sequence is increasing with respect to <i>l<\/i>.\n<\/li>\n<\/ol>\n<p>Monotone paths arise in many contexts in combinatorial geometry.<br \/>\n&#8212;<br \/>\nIn studying the structure of monotone paths one is led to consider a<br \/>\nmore general  poset, the poset of cellular strings of <i>P<\/i>, in which<br \/>\nthe monotone paths are the minimal elements. This poset was introduced<br \/>\nby Baues in his study of loop spaces, and later studied by Billera,<br \/>\nKapranov, and Sturmfels. I will discuss a number of structural<br \/>\nproperties of this poset, including its homotopy-type and the<br \/>\nconnectivity of a graph on the monotone paths derived from the poset.<\/p>\n<\/p>\n<p><\/font><\/p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Vanderbilt Mathematics Colloquia Spring 2000 July 27. Edray Goins, of the Institute for Advanced Study, School of Mathematics. On the Multiplicative Properties of the Sums of Squares. The product of any two integers which are sums of two squares is again the sum of two squares, and, similarly, the product of any two integers which&#8230;<\/p>\n","protected":false},"author":637,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"tags":[],"class_list":["post-37","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/my.vanderbilt.edu\/pastcolloquia\/wp-json\/wp\/v2\/pages\/37","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/my.vanderbilt.edu\/pastcolloquia\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/my.vanderbilt.edu\/pastcolloquia\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/my.vanderbilt.edu\/pastcolloquia\/wp-json\/wp\/v2\/users\/637"}],"replies":[{"embeddable":true,"href":"https:\/\/my.vanderbilt.edu\/pastcolloquia\/wp-json\/wp\/v2\/comments?post=37"}],"version-history":[{"count":1,"href":"https:\/\/my.vanderbilt.edu\/pastcolloquia\/wp-json\/wp\/v2\/pages\/37\/revisions"}],"predecessor-version":[{"id":38,"href":"https:\/\/my.vanderbilt.edu\/pastcolloquia\/wp-json\/wp\/v2\/pages\/37\/revisions\/38"}],"wp:attachment":[{"href":"https:\/\/my.vanderbilt.edu\/pastcolloquia\/wp-json\/wp\/v2\/media?parent=37"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/my.vanderbilt.edu\/pastcolloquia\/wp-json\/wp\/v2\/tags?post=37"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}