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Up Down ANALYSIS SEMINARS
Prof. Aharon	Atzmon	Shifts on
Prof. David	Blecher	Operator Algebras, the C*-algebras they generate, and their Morita Equivalence
Prof. Ching	Chou	Fourier Algebras of Discrete Groups
Prof. Michel	Cowen	Curvature and Congruence of Holomorphic Exponential Curves
Prof. Michel	Cowen	Curvature and Congruence of Holomorphic Exponential Curves, continued
Prof. Zongkai	Li	Jacobi Analysis and Related Topics

Prof. Mohan	Ramachandran	On Existence of Complete Kähler Metrics With Non-negative Sectional Curvature
Prof. Mohan	Ramachandran	On Existence of Complete Kähler Metrics With Non-negative Sectional Curvature
Prof. Alexander	Stokolos	Differentiation of Integrals

Up Down APPLIED MATHEMATICS SEMINARS
Prof. Dermot	Coffey	Strong-Coupling Features Due to Quasiparticle Interactions in Two Dimensional Superconductors
Dr. Edward	Furlani	Mathematical Modeling and Simulation in Industry
Prof. Gerry	Puckett	A computational Model of Liquid drop Generation

Up Down GEOMETRY/TOPOLOGY SEMINARS
		TBA
		TBA Please check this site for further information.
Prof. Olivier	Collin	Representation Varieties for Knots and 3-manifolds and the Non-periodicity of Cyclic Branched Covers of S
Prof. Scott	Crass	Solving the Quintic by Iteration in Three Dimensions
Prof. Scott	Crass	Solving the Sextic by Iteration: A Complex Dynamical Approach
Prof. William	Lawvere	Introductory to Synthetic Differential Geometry, continued
Prof. Thang	Le	The Kontsevich integral and finite type invariants of 3-manifolds.
Prof. Thang	Le	The Kontsevich integral and finite type invariants of 3-manifolds continued.

Prof. William	Menasco	A Construction of Pseudo-Anosov Homeomorphisms - After Penner, continued
Prof. William	Menasco	Embedded surfaces and gauge theory in 3- & 4-manifolds: A survey by P. Kronheimer
Prof. William	Menasco	A Construction of Pseudo-Anosov Hoemomorphisms-After Penner
Prof. William	Menasco	A Construction of Pseudo-Anosov Homeomorphisms-After Penner
Prof. William	Menasco	A Construction of Pseudo-Anosov Homeomorphisms-After Penner, continued
	TBA	Embedded surfaces and gauge theory in 3- & 4-manifolds: A survey by P. Kronheimer
	TBA	Introductory to Synthetic Differential Geometry
	TBA	Introductory to Synthetic Differential Geometry, continued
Dr. Jack	Tabor	Epsilon-Stability of Continuous, Surjective, Lipschitz and Isometric Functions

Prof. Xingru	Zhang	The A-polynomial of a Knot, continued
Prof. Xingru	Zhang	The A-polynomial of a Knot
Prof. Xingru	Zhang	The A-polynomial of a Knot, continued
To be	announced.
To be	announced.	//wings.buffalo.edu/icons/colorbar.gif" alt="colorbar">
	none	Geometry/Topology Seminar Organizational meeting

Up Down GRADUATE STUDENT SEMINARS
Mr. Hyungjik	Chae	About
Ms. Ioana	Sirbu	An Infinite-Dimensional Morse Theory with Applications
Mr. Yingquan	Wu	LII Learning Algorithm On Multi-layered Feedforward Neural Network
Mr. Zhiqiang	Zhang	One Dimensional Dynamics: Periodicity, Chaos and Entropy
Mr. Zenggang	Zhuang	Shift-Register Synthesis And BCH Decoding

Up Down MATHEMATICS COLLOQUIA
Prof. D. M.	Burns	Complex and Symplectic Geometry in the Cotangent Bundle
Prof. Andreas	Dress	Combinatorics of Finite Metric Spaces with Applications to Phylogenetics
Prof. I.	Dynnikov	Plane Sections of Periodic Surfaces in the 3-space Novikov Problem
Prof. Michael	Kapranov	Noncomutative Geometry Based on Commutator Expansions
Prof. Vycheslav	Krushkal	Topological Four-manifolds and Link Homotopy

Dr. William A.	Massey	Strong Approximations for Markovian Service Networks
Prof. William	Massey	TBA
Prof. Joyce	McLaughlin	Natural Frequencies and Mode Shapes: Rich Data Sets
Prof. Stephen H.	Schanuel	Objective Number Theory
Prof. Igor	Shparlinski	On Certain Exponential Sums and the Distribution of Diffie-Hellman Triples
Prof. Peter	Sternberg	Onset of Superconductivity in Decreasing Magnetic Fields

Prof. Jane	Wang	Aerodynamics of Insect Flight
Prof. Jane	Wang	Flapping insect flight generates high mean lift by the interaction of the wings with the shed vorticity. Typical Reynolds numbers of insects are around 5000. The high lift of an insect is not usually explained by conventional quasi-steady aerodynamics. In this study, we compute unsteady viscous flows, governed by the Navier-Stokes equation, about a flapping elliptic, which undergoes various translational and rotational motions.
Prof. Thomas	Wanner	Pattern Formation in Metal Alloys

Up Down Mathematics Colloquia
Prof. Peter	Sternberg	Onset of Superconductivity in Decreasing Magnetic Fields

Up Down SCIENCES ALUMNI ASSOCIATION LECTURES
Prof. Jon	Bell	Biomathematician Looks at Sense of Touch

Up Down SEMINARS
Prof. Stephen H.	Schanuel	What is the Length of a Potato? - an Introduction to Geometric Measure Theory
Prof. Stephen H.	Schanuel	What is the length of a potato? - an introduction to geometric measure theory

Up Down SPECIAL LECTURES
Prof. Lou	Kondic	Pattern Formation in Non-Newtonian Hele-Shaw Flow
Prof. John A.	Pelesko	Nonlinear Stability, Thermoelastic Contact, and the Barber Condition
Dr. Hongyun	Wang	Energy Transduction in ATP Synthase
Prof. Hong	Zhou	Modeling and Computation for Nonisothermal Fiber Processes

Up Down The Myhill Lectures
Prof. Robert V.	Kohn	The Mathematics of Material Microstructure

Up Down (the following was posted on 1998/12/22 at 15:05)

Welcome to the Mathematics Department
Calendar

Happy Holidays

Up Down (the following was posted on 1998/12/10 at 13:56)

Welcome to the Mathematics Department
Calendar

Happy Holidays

Up Down (the following was posted on 1998/12/04 at 15:44)

Welcome to the Mathematics Department
Calendar

Monday, December 7, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zenggang Zhuang, SUNY at Buffalo [TOC]
TITLE: Shift-Register Synthesis And BCH Decoding

Abstract: It is shown that the iterative algorithm introduced by Berlekamp for decoding BCH codes actually provides a general solution to the problem of synthesizing the shortest linear feedback shift register capable of generating a prescribed finite sequence of digits. The shift-register approach leads to a simple proof of the validity of the algorithm as well as providing additional insight into its properties. The equivalence of the decoding problem for BCH codes to a shift-register synthesis problem is demonstrated, and other application for the algorithm are suggested.

Up Down (the following was posted on 1998/12/02 at 09:32)

Welcome to the Mathematics Department
Calendar

Thursday, December 3, 1998 - 4 p.m. - 103 Diefendorf Hall
SEMINAR FOR GRADUATE STUDENTS
SPEAKER: Prof. Stephen H. Schanuel, SUNY at Buffalo [TOC]
TITLE: What is the Length of a Potato? - an Introduction to Geometric Measure Theory

Friday, December 4, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. Scott Crass, SUNY College at Buffalo [TOC]
TITLE: Solving the Quintic by Iteration in Three Dimensions

Abstract. The permutation action of the symmetric group S₅ on C⁵ descends to an action on complex projective 3-space. There are several S₅ -symmetric maps on CP³ with rather interesting geometric and dynamical properties. The talk will describe two such maps as well as how to use one of them to solve the quintic. Finally, there will be an attempt to implement the procedure in real time.

Monday, December 7, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zenggang Zhuang, SUNY at Buffalo [TOC]
TITLE: Shift-Register Synthesis And BCH Decoding

Abstract: It is shown that the iterative algorithm introduced by Berlekamp for decoding BCH codes actually provides a general solution to the problem of synthesizing the shortest linear feedback shift register capable of generating a prescribed finite sequence of digits. The shift-register approach leads to a simple proof of the validity of the algorithm as well as providing additional insight into its properties. The equivalence of the decoding problem for BCH codes to a shift-register synthesis problem is demonstrated, and other application for the algorithm are suggested.

Up Down (the following was posted on 1998/11/25 at 13:21)

Welcome to the Mathematics Department
Calendar

Monday, November 23, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Dr. Hongyun Wang, Dept. of Molecular & Cellular Biology, University of California, Berkeley [TOC]
TITLE: Energy Transduction in ATP Synthase

Abstract: ATP (adenosin triphosphate) is the most important chemical energy source in all living cells, involved in muscle contraction, nerve message transmission and other cell functions. ATP synthase is the universal enzyme that manufactures ATP from ADP and phosphate using the energy derived from a transmembrane protonmotive force. It can also reverse itself and hydrolyze ATP to pump protons against a electrochemical gradient. Recent structural information indicates that ATP synthase carries out both its synthetic and hydrolytic cycles by a rotary mechanism. Thus ATP synthase comprises what must be the world's smallest rotary motor. I will present a model for the mechanics and chemistry of ATP synthase that accounts for its mechanochemical behavior in both the hydrolysis and synthesis directions.

Monday, November 30, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zhiqiang Zhang, SUNY at Buffalo [TOC]
TITLE: One Dimensional Dynamics: Periodicity, Chaos and Entropy

Abstract. In the last two decades, topics in one dimensional dynamics are extensively studied. In this seminar, I will give an introduction to some topics and show some very sharp results in this area. Let f: I - - >I be a continuous map of the interval to itself. Let positive integers be re-ordered as: 3 < 5 < 7 < 9 < ... < 2*3 < 2*5 < 2*7 < 2*9 < ... < ... < 2³ < 2² < 2 < 1. Then we have Sarkovskii's theorem: if f has a periodic orbit of period n and if n < m, then f also has a periodic orbit of period m. The relation between periodicity and chaoticity of f is described in the following theorem: f is chaotic iff f has a periodic point whose period is not a power of 2. The relation between periodicity and the entropy of f is described in Misiurewicz's theorem: The entropy of f ent(f) > 0 iff f has a periodic point whose period is not a power of 2.

Thursday, December 3, 1998 - 4 p.m. - 103 Diefendorf Hall
SEMINAR FOR GRADUATE STUDENTS
SPEAKER: Prof. Stephen H. Schanuel, SUNY at Buffalo [TOC]
TITLE: What is the Length of a Potato? - an Introduction to Geometric Measure Theory

Friday, December 4, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. Scott Crass, SUNY College at Buffalo [TOC]
TITLE: Solving the Quintic by Iteration in Three Dimensions

Abstract. The permutation action of the symmetric group S₅ on C⁵ descends to an action on complex projective 3-space. There are several S₅ -symmetric maps on CP³ with rather interesting geometric and dynamical properties. The talk will describe two such maps as well as how to use one of them to solve the quintic. Finally, there will be an attempt to implement the procedure in real time.

Monday, December 7, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zenggang Zhuang, SUNY at Buffalo [TOC]
TITLE: Shift-Register Synthesis And BCH Decoding

Abstract: It is shown that the iterative algorithm introduced by Berlekamp for decoding BCH codes actually provides a general solution to the problem of synthesizing the shortest linear feedback shift register capable of generating a prescribed finite sequence of digits. The shift-register approach leads to a simple proof of the validity of the algorithm as well as providing additional insight into its properties. The equivalence of the decoding problem for BCH codes to a shift-register synthesis problem is demonstrated, and other application for the algorithm are suggested.

Up Down (the following was posted on 1998/11/23 at 13:30)

Welcome to the Mathematics Department
Calendar

Monday, November 23, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Dr. Hongyun Wang, Dept. of Molecular & Cellular Biology, University of California, Berkeley [TOC]
TITLE: Energy Transduction in ATP Synthase

Abstract: ATP (adenosin triphosphate) is the most important chemical energy source in all living cells, involved in muscle contraction, nerve message transmission and other cell functions. ATP synthase is the universal enzyme that manufactures ATP from ADP and phosphate using the energy derived from a transmembrane protonmotive force. It can also reverse itself and hydrolyze ATP to pump protons against a electrochemical gradient. Recent structural information indicates that ATP synthase carries out both its synthetic and hydrolytic cycles by a rotary mechanism. Thus ATP synthase comprises what must be the world's smallest rotary motor. I will present a model for the mechanics and chemistry of ATP synthase that accounts for its mechanochemical behavior in both the hydrolysis and synthesis directions.

Monday, November 30, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zhiqiang Zhang, SUNY at Buffalo [TOC]
TITLE: One Dimensional Dynamics: Periodicity, Chaos and Entropy

Abstract. In the last two decades, topics in one dimensional dynamics are extensively studied. In this seminar, I will give an introduction to some topics and show some very sharp results in this area. Let f: I - - >I be a continuous map of the interval to itself. Let positive integers be re-ordered as: 3 < 5 < 7 < 9 < ... < 2*3 < 2*5 < 2*7 < 2*9 < ... < ... < 2³ < 2² < 2 < 1. Then we have Sarkovskii's theorem: if f has a periodic orbit of period n and if n < m, then f also has a periodic orbit of period m. The relation between periodicity and chaoticity of f is described in the following theorem: f is chaotic iff f has a periodic point whose period is not a power of 2. The relation between periodicity and the entropy of f is described in Misiurewicz's theorem: The entropy of f ent(f) > 0 iff f has a periodic point whose period is not a power of 2.

Thursday, December 3, 1998 - 4 p.m. - 103 Diefendorf Hall
SEMINAR FOR GRADUATE STUDENTS
SPEAKER: Prof. Stephen H. Schanuel, SUNY at Buffalo [TOC]
TITLE: What is the Length of a Potato? - an Introduction to Geometric Measure Theory

Monday, December 7, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zenggang Zhuang, SUNY at Buffalo [TOC]
TITLE: Shift-Register Synthesis And BCH Decoding

Abstract: It is shown that the iterative algorithm introduced by Berlekamp for decoding BCH codes actually provides a general solution to the problem of synthesizing the shortest linear feedback shift register capable of generating a prescribed finite sequence of digits. The shift-register approach leads to a simple proof of the validity of the algorithm as well as providing additional insight into its properties. The equivalence of the decoding problem for BCH codes to a shift-register synthesis problem is demonstrated, and other application for the algorithm are suggested.

Up Down (the following was posted on 1998/11/17 at 15:57)

Welcome to the Mathematics Department
Calendar

Wednesday, November 18, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. David Blecher, University of Houston [TOC]
TITLE: Operator Algebras, the C*-algebras they generate, and their Morita Equivalence

Thursday, November 19, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. D. M. Burns, University of Michigan, Ann Arbor [TOC]
TITLE: Complex and Symplectic Geometry in the Cotangent Bundle

Friday, November 20, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. William Menasco, SUNY at Buffalo [TOC]
TITLE: A Construction of Pseudo-Anosov Homeomorphisms - After Penner, continued

Monday, November 23, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Dr. Hongyun Wang, Dept. of Molecular & Cellular Biology, University of California, Berkeley [TOC]
TITLE: Energy Transduction in ATP Synthase

Abstract: ATP (adenosin triphosphate) is the most important chemical energy source in all living cells, involved in muscle contraction, nerve message transmission and other cell functions. ATP synthase is the universal enzyme that manufactures ATP from ADP and phosphate using the energy derived from a transmembrane protonmotive force. It can also reverse itself and hydrolyze ATP to pump protons against a electrochemical gradient. Recent structural information indicates that ATP synthase carries out both its synthetic and hydrolytic cycles by a rotary mechanism. Thus ATP synthase comprises what must be the world's smallest rotary motor. I will present a model for the mechanics and chemistry of ATP synthase that accounts for its mechanochemical behavior in both the hydrolysis and synthesis directions.

Monday, November 30, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zhiqiang Zhang, SUNY at Buffalo [TOC]
TITLE: One Dimensional Dynamics: Periodicity, Chaos and Entropy

Abstract. In the last two decades, topics in one dimensional dynamics are extensively studied. In this seminar, I will give an introduction to some topics and show some very sharp results in this area. Let f: I - - >I be a continuous map of the interval to itself. Let positive integers be re-ordered as: 3 < 5 < 7 < 9 < ... < 2*3 < 2*5 < 2*7 < 2*9 < ... < ... < 2³ < 2² < 2 < 1. Then we have Sarkovskii's theorem: if f has a periodic orbit of period n and if n < m, then f also has a periodic orbit of period m. The relation between periodicity and chaoticity of f is described in the following theorem: f is chaotic iff f has a periodic point whose period is not a power of 2. The relation between periodicity and the entropy of f is described in Misiurewicz's theorem: The entropy of f ent(f) > 0 iff f has a periodic point whose period is not a power of 2.

Thursday, December 3, 1998 - 4 p.m. - 103 Diefendorf Hall
SEMINAR FOR GRADUATE STUDENTS
SPEAKER: Prof. Stephen H. Schanuel, SUNY at Buffalo [TOC]
TITLE: What is the length of a potato? - an introduction to geometric measure theory

Up Down (the following was posted on 1998/11/16 at 15:20)

Welcome to the Mathematics Department
Calendar

Monday, November 16, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Lou Kondic, Duke University [TOC]
TITLE: Pattern Formation in Non-Newtonian Hele-Shaw Flow

Abstract. We explore the morphology of patterns due to the Saffman-Taylor instability in Hele-Shaw cells and find that it can be dramatically altered by the non-Newtonian response of complex fluids such as liquid crystals and polymer solutions. The dense-branching morphology of Newtonian liquids may be replaced by dendritic fingers with stable tips and sidebranches.
Starting from a very general viscoelastic fluid model, we find a distinguished limit where shear thinning effect is dominant. A Darcy's law leads to the nonlinear boundary value problem for the pressure in the fluid. Full numerical simulations show that shear thinning alone modifies considerably the pattern formation and can produce fingers whose tip-splitting is suppressed, in agreement with experimental results. These fingers grow in an oscillating fashion, shedding "side-branches"' from their tips, closely resembling solidification patterns.

Wednesday, November 18, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. David Blecher, University of Houston [TOC]
TITLE: Operator Algebras, the C*-algebras they generate, and their Morita Equivalence

Thursday, November 19, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. D. M. Burns, University of Michigan, Ann Arbor [TOC]
TITLE: Complex and Symplectic Geometry in the Cotangent Bundle

Friday, November 20, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. William Menasco, SUNY at Buffalo [TOC]
TITLE: A Construction of Pseudo-Anosov Homeomorphisms - After Penner, continued

Monday, November 23, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Dr. Hongyun Wang, University of California, Berkeley [TOC]
TITLE: Energy Transduction in ATP Synthase

Abstract: ATP (adenosin triphosphate) is the most important chemical energy source in all living cells, involved in muscle contraction, nerve message transmission and other cell functions. ATP synthase is the universal enzyme that manufactures ATP from ADP and phosphate using the energy derived from a transmembrane protonmotive force. It can also reverse itself and hydrolyze ATP to pump protons against a electrochemical gradient. Recent structural information indicates that ATP synthase carries out both its synthetic and hydrolytic cycles by a rotary mechanism. Thus ATP synthase comprises what must be the world's smallest rotary motor. I will present a model for the mechanics and chemistry of ATP synthase that accounts for its mechanochemical behavior in both the hydrolysis and synthesis directions.

Monday, November 30, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zhiqiang Zhang, SUNY at Buffalo [TOC]
TITLE: One Dimensional Dynamics: Periodicity, Chaos and Entropy

Abstract. In the last two decades, topics in one dimensional dynamics are extensively studied. In this seminar, I will give an introduction to some topics and show some very sharp results in this area. Let f: I - - >I be a continuous map of the interval to itself. Let positive integers be re-ordered as: 3 < 5 < 7 < 9 < ... < 2*3 < 2*5 < 2*7 < 2*9 < ... < ... < 2³ < 2² < 2 < 1. Then we have Sarkovskii's theorem: if f has a periodic orbit of period n and if n < m, then f also has a periodic orbit of period m. The relation between periodicity and chaoticity of f is described in the following theorem: f is chaotic iff f has a periodic point whose period is not a power of 2. The relation between periodicity and the entropy of f is described in Misiurewicz's theorem: The entropy of f ent(f) > 0 iff f has a periodic point whose period is not a power of 2.

Up Down (the following was posted on 1998/11/10 at 11:47)

Welcome to the Mathematics Department
Calendar

Wednesday, November 11, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Zongkai Li, Capital Normal University, Beijing - Visiting SUNY/Buffalo [TOC]
TITLE: Jacobi Analysis and Related Topics

Thursday, November 12, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. Thomas Wanner, University of Maryland/Baltimore County [TOC]
TITLE: Pattern Formation in Metal Alloys

Abstract. Pattern formation phenomena have drawn considerable interest in the last few years. Many mathematical and physical investigations focus on understanding how complex patterns are created and which mechanisms cause their persistence. In this talk I will address one particular phenomenon which can be observed during the solidification process of metal alloys, called spinodal decomposition. Recent mathematical results will be presented for the Cahn-Hilliard equation, a partial differential equation modeling phase separation in metal alloys. These results describe the characteristics of generated patterns, as well as the surprising mechanism underlying their formation.

Friday, November 13, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. Olivier Collin, University of British Columbia [TOC]
TITLE: Representation Varieties for Knots and 3-manifolds and the Non-periodicity of Cyclic Branched Covers of S³ Along Knots

Monday, November 16, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Lou Kondic, Duke University [TOC]
TITLE: Pattern Formation in Non-Newtonian Hele-Shaw Flow

Abstract. We explore the morphology of patterns due to the Saffman-Taylor instability in Hele-Shaw cells and find that it can be dramatically altered by the non-Newtonian response of complex fluids such as liquid crystals and polymer solutions. The dense-branching morphology of Newtonian liquids may be replaced by dendritic fingers with stable tips and sidebranches.
Starting from a very general viscoelastic fluid model, we find a distinguished limit where shear thinning effect is dominant. A Darcy's law leads to the nonlinear boundary value problem for the pressure in the fluid. Full numerical simulations show that shear thinning alone modifies considerably the pattern formation and can produce fingers whose tip-splitting is suppressed, in agreement with experimental results. These fingers grow in an oscillating fashion, shedding "side-branches"' from their tips, closely resembling solidification patterns.

Wednesday, November 18, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. David Blecher, University of Houston [TOC]
TITLE: Operator Algebras, the C*-algebras they generate, and their Morita Equivalence

Thursday, November 19, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. D. M. Burns, University of Michigan, Ann Arbor [TOC]
TITLE: Complex and Symplectic Geometry in the Cotangent Bundle

Friday, November 20, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. William Menasco, SUNY at Buffalo [TOC]
TITLE: A Construction of Pseudo-Anosov Homeomorphisms - After Penner, continued

Monday, November 30, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zhiqiang Zhang, SUNY at Buffalo [TOC]
TITLE: One Dimensional Dynamics: Periodicity, Chaos and Entropy

Abstract. In the last two decades, topics in one dimensional dynamics are extensively studied. In this seminar, I will give an introduction to some topics and show some very sharp results in this area. Let f: I - - >I be a continuous map of the interval to itself. Let positive integers be re-ordered as: 3 < 5 < 7 < 9 < ... < 2*3 < 2*5 < 2*7 < 2*9 < ... < ... < 2³ < 2² < 2 < 1. Then we have Sarkovskii's theorem: if f has a periodic orbit of period n and if n < m, then f also has a periodic orbit of period m. The relation between periodicity and chaoticity of f is described in the following theorem: f is chaotic iff f has a periodic point whose period is not a power of 2. The relation between periodicity and the entropy of f is described in Misiurewicz's theorem: The entropy of f ent(f) > 0 iff f has a periodic point whose period is not a power of 2.

Up Down (the following was posted on 1998/11/06 at 15:34)

Welcome to the Mathematics Department
Calendar

Wednesday, November 11, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Zongkai Li, Capital Normal University, Beijing - Visiting SUNY/Buffalo [TOC]
TITLE: Jacobi Analysis and Related Topics

Thursday, November 12, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. Thomas Wanner, University of Maryland/Baltimore County [TOC]
TITLE: Pattern Formation in Metal Alloys

Abstract. Pattern formation phenomena have drawn considerable interest in the last few years. Many mathematical and physical investigations focus on understanding how complex patterns are created and which mechanisms cause their persistence. In this talk I will address one particular phenomenon which can be observed during the solidification process of metal alloys, called spinodal decomposition. Recent mathematical results will be presented for the Cahn-Hilliard equation, a partial differential equation modeling phase separation in metal alloys. These results describe the characteristics of generated patterns, as well as the surprising mechanism underlying their formation.

Friday, November 13, 1998 - 4 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. Olivier Collin, University of British Columbia [TOC]
TITLE: Representation Varieties for Knots and 3-manifolds and the Non-periodicity of Cyclic Branched Covers of S³ Along Knots

Monday, November 16, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Lou Kondic, Duke University [TOC]
TITLE: Pattern Formation in Non-Newtonian Hele-Shaw Flow

Abstract. We explore the morphology of patterns due to the Saffman-Taylor instability in Hele-Shaw cells and find that it can be dramatically altered by the non-Newtonian response of complex fluids such as liquid crystals and polymer solutions. The dense-branching morphology of Newtonian liquids may be replaced by dendritic fingers with stable tips and sidebranches.
Starting from a very general viscoelastic fluid model, we find a distinguished limit where shear thinning effect is dominant. A Darcy's law leads to the nonlinear boundary value problem for the pressure in the fluid. Full numerical simulations show that shear thinning alone modifies considerably the pattern formation and can produce fingers whose tip-splitting is suppressed, in agreement with experimental results. These fingers grow in an oscillating fashion, shedding "side-branches"' from their tips, closely resembling solidification patterns.

Wednesday, November 18, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. David Blecher, University of Houston [TOC]
TITLE: Operator Algebras, the C*-algebras they generate, and their Morita Equivalence

Thursday, November 19, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. D. M. Burns, University of Michigan, Ann Arbor [TOC]
TITLE: Complex and Symplectic Geometry in the Cotangent Bundle

Monday, November 30, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zhiqiang Zhang, SUNY at Buffalo [TOC]
TITLE: One Dimensional Dynamics: Periodicity, Chaos and Entropy

Abstract. In the last two decades, topics in one dimensional dynamics are extensively studied. In this seminar, I will give an introduction to some topics and show some very sharp results in this area. Let f: I - - >I be a continuous map of the interval to itself. Let positive integers be re-ordered as: 3 < 5 < 7 < 9 < ... < 2*3 < 2*5 < 2*7 < 2*9 < ... < ... < 2³ < 2² < 2 < 1. Then we have Sarkovskii's theorem: if f has a periodic orbit of period n and if n < m, then f also has a periodic orbit of period m. The relation between periodicity and chaoticity of f is described in the following theorem: f is chaotic iff f has a periodic point whose period is not a power of 2. The relation between periodicity and the entropy of f is described in Misiurewicz's theorem: The entropy of f ent(f) > 0 iff f has a periodic point whose period is not a power of 2.

Up Down (the following was posted on 1998/11/03 at 14:42)

Welcome to the Mathematics Department
Calendar

Tuesday, November 3, 1998 - 4 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. William Menasco, SUNY at Buffalo [TOC]
TITLE: A Construction of Pseudo-Anosov Homeomorphisms-After Penner, continued

Wednesday, November 4, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Michel Cowen, SUNY at Buffalo [TOC]
TITLE: Curvature and Congruence of Holomorphic Exponential Curves, continued

Thursday, November 5, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Dr. William A. Massey, Lucent Technologies [TOC]
TITLE: Strong Approximations for Markovian Service Networks

Abstract. Inspired by service systems like telephone call centers, we develop limit theorems for a large class nonstationary Markov processes that we call stochastic service network models. The asymptotic limiting regime that we explore for these networks has a natural interpretation of scaling up the number of servers in response to a similar scaling up of the arrival rate for the customers.
We employ the theory of strong approximations to obtain functional strong laws of large numbers and functional central limit theorems for these networks. This gives us a tractable set of network fluid and diffusion approximations. The diffusion limits are obtained by using a new notion of non-smooth differentiation.
This is joint work with Marty Reiman of Bell Labs and Avi Mandelbaum of Technion.

Friday, November 6, 1998 - 3:15 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. John A. Pelesko, California Institute of Technology [TOC]
TITLE: Nonlinear Stability, Thermoelastic Contact, and the Barber Condition

Abstract. Thermoelastic contact problems arise in areas as diverse as the study of automotive disk brakes, the production of metals, and the analysis of heat exchangers. In 1978, it was pointed out by J.R. Barber that the solution of such problems posed certain difficulties. In particular, the assumption of perfect insulation during a separated phase and perfect thermal contact during contact led to models with solutions which were unacceptable on physical grounds. Rejecting such solutions, Barber conjectured that these models failed to capture relevant physics and introduced a pressure dependent thermal boundary condition, which has since become known as the Barber condition. Since that time, various authors have explored the Barber condition and its implications for thermal contact problems. While such analyses have been extended to multiple materials, various geometries, and to numerical simulations, all theoretical work to date has relied upon linear stability theory. While this provides useful information about the existence of steady-states and their stability to infinitesimal perturbations, it fails to provide information about dynamics, history dependence, and nonlinear effects.
In this talk, we show how singular perturbation techniques may be used to investigate thermal contact problems. In particular, we consider two one-dimensional thermoelastic rod models. In the first, we introduce a modified Dirichlet boundary condition to simulate the effects of thermal contact on heat transfer. We show that this system undergoes a bifurcation from a single linearly stable steady-state solution to multiple steady-state solutions. We use multiple scale or two-timing methods to investigate the nonlinear behavior near the bifurcation point. In the second system studied, we replace the Dirichlet condition with the more physically realistic boundary condition introduced by Barber. Here the application of multiple scale methods becomes analytically intractable and we turn to matched asymptotics. Again, we investigate the behavior of the system near a bifurcation point,thereby obtaining information about dynamics, history dependence, and nonlinear effects.

Wednesday, November 11, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Zongkai Li, Capital Normal University, Beijing - Visiting SUNY/Buffalo [TOC]
TITLE: Jacobi Analysis and Related Topics

Thursday, November 12, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. Thomas Wanner, University of Maryland/Baltimore County [TOC]
TITLE: Pattern Formation in Metal Alloys

Abstract. Pattern formation phenomena have drawn considerable interest in the last few years. Many mathematical and physical investigations focus on understanding how complex patterns are created and which mechanisms cause their persistence. In this talk I will address one particular phenomenon which can be observed during the solidification process of metal alloys, called spinodal decomposition. Recent mathematical results will be presented for the Cahn-Hilliard equation, a partial differential equation modeling phase separation in metal alloys. These results describe the characteristics of generated patterns, as well as the surprising mechanism underlying their formation.

Friday, November 13, 1998 - 4 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. Olivier Collin, University of British Columbia [TOC]
TITLE: Representation Varieties for Knots and 3-manifolds and the Non-periodicity of Cyclic Branched Covers of S³ Along Knots

Monday, November 16, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Lou Kondic, Duke University [TOC]
TITLE: Pattern Formation in Non-Newtonian Hele-Shaw Flow

Abstract. We explore the morphology of patterns due to the Saffman-Taylor instability in Hele-Shaw cells and find that it can be dramatically altered by the non-Newtonian response of complex fluids such as liquid crystals and polymer solutions. The dense-branching morphology of Newtonian liquids may be replaced by dendritic fingers with stable tips and sidebranches.
Starting from a very general viscoelastic fluid model, we find a distinguished limit where shear thinning effect is dominant. A Darcy's law leads to the nonlinear boundary value problem for the pressure in the fluid. Full numerical simulations show that shear thinning alone modifies considerably the pattern formation and can produce fingers whose tip-splitting is suppressed, in agreement with experimental results. These fingers grow in an oscillating fashion, shedding "side-branches"' from their tips, closely resembling solidification patterns.

Wednesday, November 18, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. David Blecher, University of Houston [TOC]
TITLE: Operator Algebras, the C*-algebras they generate, and their Morita Equivalence

Monday, November 30, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zhiqiang Zhang, SUNY at Buffalo [TOC]
TITLE: One Dimensional Dynamics: Periodicity, Chaos and Entropy

Abstract. In the last two decades, topics in one dimensional dynamics are extensively studied. In this seminar, I will give an introduction to some topics and show some very sharp results in this area. Let f: I - - >I be a continuous map of the interval to itself. Let positive integers be re-ordered as: 3 < 5 < 7 < 9 < ... < 2*3 < 2*5 < 2*7 < 2*9 < ... < ... < 2³ < 2² < 2 < 1. Then we have Sarkovskii's theorem: if f has a periodic orbit of period n and if n < m, then f also has a periodic orbit of period m. The relation between periodicity and chaoticity of f is described in the following theorem: f is chaotic iff f has a periodic point whose period is not a power of 2. The relation between periodicity and the entropy of f is described in Misiurewicz's theorem: The entropy of f ent(f) > 0 iff f has a periodic point whose period is not a power of 2.

Up Down (the following was posted on 1998/11/02 at 15:05)

Welcome to the Mathematics Department
Calendar

Monday, November 2, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Hong Zhou, University of North Carolina, Chapel Hill [TOC]
TITLE: Modeling and Computation for Nonisothermal Fiber Processes

Abstract. Nonisothermal fiber processes have many applications, including liquid crystalline polymers and optical glass fibers. In particular, many ultra-strength textile fibers, e.g. Vectran and Kelvar, achieve their distinguished commercial properties (such as high tensile modulus) as a result of the interaction between anisotropic molecular-scale structure of the melt, macroscopic hydrodynamics of spinning flows, and nonisothermal effects.
Fiber spinning is one of the important techniques utilizing the flow-induced molecular orientation of liquid crystalline polymers (LCPs). We apply a fiber spinning model for lyotropic and thermotropic liquid crystalline polymers that couples hydrodynamics, anisotropic rod-like microstructural dynamics, free surface effects, and thermodynamics. Exploiting slender aspect ratio, we extract 1-D systems of nonlinear PDEs for ``longwave interactions'' of hydro/thermo/orientation. Fiber spinning steady states (BVP) and their stability are computed in realistic physical regimes, predicting spun fiber properties and process sensitivity. Trends in spinline performance due to material variations are very different in isothermal vs nonisothermal simulations. This result raises caution against application of isothermal models for real spinlines, and emphasizes the critical role of thermodynamics in spinning processes.

Tuesday, November 3, 1998 - 4 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. William Menasco, SUNY at Buffalo [TOC]
TITLE: A Construction of Pseudo-Anosov Homeomorphisms-After Penner, continued

Wednesday, November 4, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Michel Cowen, SUNY at Buffalo [TOC]
TITLE: Curvature and Congruence of Holomorphic Exponential Curves, continued

Thursday, November 5, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Dr. William A. Massey, Lucent Technologies [TOC]
TITLE: Strong Approximations for Markovian Service Networks

Abstract. Inspired by service systems like telephone call centers, we develop limit theorems for a large class nonstationary Markov processes that we call stochastic service network models. The asymptotic limiting regime that we explore for these networks has a natural interpretation of scaling up the number of servers in response to a similar scaling up of the arrival rate for the customers.
We employ the theory of strong approximations to obtain functional strong laws of large numbers and functional central limit theorems for these networks. This gives us a tractable set of network fluid and diffusion approximations. The diffusion limits are obtained by using a new notion of non-smooth differentiation.
This is joint work with Marty Reiman of Bell Labs and Avi Mandelbaum of Technion.

Friday, November 6, 1998 - 3:15 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. John A. Pelesko, California Institute of Technology [TOC]
TITLE: Nonlinear Stability, Thermoelastic Contact, and the Barber Condition

Abstract. Thermoelastic contact problems arise in areas as diverse as the study of automotive disk brakes, the production of metals, and the analysis of heat exchangers. In 1978, it was pointed out by J.R. Barber that the solution of such problems posed certain difficulties. In particular, the assumption of perfect insulation during a separated phase and perfect thermal contact during contact led to models with solutions which were unacceptable on physical grounds. Rejecting such solutions, Barber conjectured that these models failed to capture relevant physics and introduced a pressure dependent thermal boundary condition, which has since become known as the Barber condition. Since that time, various authors have explored the Barber condition and its implications for thermal contact problems. While such analyses have been extended to multiple materials, various geometries, and to numerical simulations, all theoretical work to date has relied upon linear stability theory. While this provides useful information about the existence of steady-states and their stability to infinitesimal perturbations, it fails to provide information about dynamics, history dependence, and nonlinear effects.
In this talk, we show how singular perturbation techniques may be used to investigate thermal contact problems. In particular, we consider two one-dimensional thermoelastic rod models. In the first, we introduce a modified Dirichlet boundary condition to simulate the effects of thermal contact on heat transfer. We show that this system undergoes a bifurcation from a single linearly stable steady-state solution to multiple steady-state solutions. We use multiple scale or two-timing methods to investigate the nonlinear behavior near the bifurcation point. In the second system studied, we replace the Dirichlet condition with the more physically realistic boundary condition introduced by Barber. Here the application of multiple scale methods becomes analytically intractable and we turn to matched asymptotics. Again, we investigate the behavior of the system near a bifurcation point,thereby obtaining information about dynamics, history dependence, and nonlinear effects.

Wednesday, November 11, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Zongkai Li, Capital Normal University, Beijing - Visiting SUNY/Buffalo [TOC]
TITLE: Jacobi Analysis and Related Topics

Thursday, November 12, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. Thomas Wanner, University of Maryland/Baltimore County [TOC]
TITLE: Pattern Formation in Metal Alloys

Abstract. Pattern formation phenomena have drawn considerable interest in the last few years. Many mathematical and physical investigations focus on understanding how complex patterns are created and which mechanisms cause their persistence. In this talk I will address one particular phenomenon which can be observed during the solidification process of metal alloys, called spinodal decomposition. Recent mathematical results will be presented for the Cahn-Hilliard equation, a partial differential equation modeling phase separation in metal alloys. These results describe the characteristics of generated patterns, as well as the surprising mechanism underlying their formation.

Monday, November 13, 1998 - 4 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. Olivier Collin, University of British Columbia [TOC]
TITLE: Representation Varieties for Knots and 3-manifolds and the Non-periodicity of Cyclic Branched Covers of S³ Along Knots

Monday, November 16, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Lou Kondic, Duke University [TOC]
TITLE: Pattern Formation in Non-Newtonian Hele-Shaw Flow

Abstract. We explore the morphology of patterns due to the Saffman-Taylor instability in Hele-Shaw cells and find that it can be dramatically altered by the non-Newtonian response of complex fluids such as liquid crystals and polymer solutions. The dense-branching morphology of Newtonian liquids may be replaced by dendritic fingers with stable tips and sidebranches.
Starting from a very general viscoelastic fluid model, we find a distinguished limit where shear thinning effect is dominant. A Darcy's law leads to the nonlinear boundary value problem for the pressure in the fluid. Full numerical simulations show that shear thinning alone modifies considerably the pattern formation and can produce fingers whose tip-splitting is suppressed, in agreement with experimental results. These fingers grow in an oscillating fashion, shedding "side-branches"' from their tips, closely resembling solidification patterns.

Monday, November 30, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zhiqiang Zhang, SUNY at Buffalo [TOC]
TITLE: One Dimensional Dynamics: Periodicity, Chaos and Entropy

Abstract. In the last two decades, topics in one dimensional dynamics are extensively studied. In this seminar, I will give an introduction to some topics and show some very sharp results in this area. Let f: I - - >I be a continuous map of the interval to itself. Let positive integers be re-ordered as: 3 < 5 < 7 < 9 < ... < 2*3 < 2*5 < 2*7 < 2*9 < ... < ... < 2³ < 2² < 2 < 1. Then we have Sarkovskii's theorem: if f has a periodic orbit of period n and if n < m, then f also has a periodic orbit of period m. The relation between periodicity and chaoticity of f is described in the following theorem: f is chaotic iff f has a periodic point whose period is not a power of 2. The relation between periodicity and the entropy of f is described in Misiurewicz's theorem: The entropy of f ent(f) > 0 iff f has a periodic point whose period is not a power of 2.

Up Down (the following was posted on 1998/10/29 at 10:49)

Welcome to the Mathematics Department
Calendar

Thursday, October 29, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. Joyce McLaughlin, Rensselaer Polytechnic Institute [TOC]
TITLE: Natural Frequencies and Mode Shapes: Rich Data Sets

Abstract. Excite an object at a natural frequency. Make selected measurements of the response. This lecture describes how we analyze this data to find properties of the vibrating system.

Friday, October 30, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. William Menasco, SUNY at Buffalo [TOC]
TITLE: A Construction of Pseudo-Anosov Homeomorphisms-After Penner

Monday, November 2, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Hong Zhou, University of North Carolina, Chapel Hill [TOC]
TITLE: Modeling and Computation for Nonisothermal Fiber Processes

Abstract. Nonisothermal fiber processes have many applications, including liquid crystalline polymers and optical glass fibers. In particular, many ultra-strength textile fibers, e.g. Vectran and Kelvar, achieve their distinguished commercial properties (such as high tensile modulus) as a result of the interaction between anisotropic molecular-scale structure of the melt, macroscopic hydrodynamics of spinning flows, and nonisothermal effects.
Fiber spinning is one of the important techniques utilizing the flow-induced molecular orientation of liquid crystalline polymers (LCPs). We apply a fiber spinning model for lyotropic and thermotropic liquid crystalline polymers that couples hydrodynamics, anisotropic rod-like microstructural dynamics, free surface effects, and thermodynamics. Exploiting slender aspect ratio, we extract 1-D systems of nonlinear PDEs for ``longwave interactions'' of hydro/thermo/orientation. Fiber spinning steady states (BVP) and their stability are computed in realistic physical regimes, predicting spun fiber properties and process sensitivity. Trends in spinline performance due to material variations are very different in isothermal vs nonisothermal simulations. This result raises caution against application of isothermal models for real spinlines, and emphasizes the critical role of thermodynamics in spinning processes.

Wednesday, November 4, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Michel Cowen, SUNY at Buffalo [TOC]
TITLE: Curvature and Congruence of Holomorphic Exponential Curves, continued

Thursday, November 5, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Dr. William A. Massey, Lucent Technologies [TOC]
TITLE: Strong Approximations for Markovian Service Networks

Abstract. Inspired by service systems like telephone call centers, we develop limit theorems for a large class nonstationary Markov processes that we call stochastic service network models. The asymptotic limiting regime that we explore for these networks has a natural interpretation of scaling up the number of servers in response to a similar scaling up of the arrival rate for the customers.
We employ the theory of strong approximations to obtain functional strong laws of large numbers and functional central limit theorems for these networks. This gives us a tractable set of network fluid and diffusion approximations. The diffusion limits are obtained by using a new notion of non-smooth differentiation.
This is joint work with Marty Reiman of Bell Labs and Avi Mandelbaum of Technion.

Friday, November 6, 1998 - 3:15 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. John A. Pelesko, California Institute of Technology [TOC]
TITLE: Nonlinear Stability, Thermoelastic Contact, and the Barber Condition

Abstract. Thermoelastic contact problems arise in areas as diverse as the study of automotive disk brakes, the production of metals, and the analysis of heat exchangers. In 1978, it was pointed out by J.R. Barber that the solution of such problems posed certain difficulties. In particular, the assumption of perfect insulation during a separated phase and perfect thermal contact during contact led to models with solutions which were unacceptable on physical grounds. Rejecting such solutions, Barber conjectured that these models failed to capture relevant physics and introduced a pressure dependent thermal boundary condition, which has since become known as the Barber condition. Since that time, various authors have explored the Barber condition and its implications for thermal contact problems. While such analyses have been extended to multiple materials, various geometries, and to numerical simulations, all theoretical work to date has relied upon linear stability theory. While this provides useful information about the existence of steady-states and their stability to infinitesimal perturbations, it fails to provide information about dynamics, history dependence, and nonlinear effects.
In this talk, we show how singular perturbation techniques may be used to investigate thermal contact problems. In particular, we consider two one-dimensional thermoelastic rod models. In the first, we introduce a modified Dirichlet boundary condition to simulate the effects of thermal contact on heat transfer. We show that this system undergoes a bifurcation from a single linearly stable steady-state solution to multiple steady-state solutions. We use multiple scale or two-timing methods to investigate the nonlinear behavior near the bifurcation point. In the second system studied, we replace the Dirichlet condition with the more physically realistic boundary condition introduced by Barber. Here the application of multiple scale methods becomes analytically intractable and we turn to matched asymptotics. Again, we investigate the behavior of the system near a bifurcation point,thereby obtaining information about dynamics, history dependence, and nonlinear effects.

Wednesday, November 11, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Zongkai Li, Capital Normal University, Beijing - Visiting SUNY/Buffalo [TOC]
TITLE: Jacobi Analysis and Related Topics

Thursday, November 12, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. Thomas Wanner, University of Maryland/Baltimore County [TOC]
TITLE: Pattern Formation in Metal Alloys

Abstract. Pattern formation phenomena have drawn considerable interest in the last few years. Many mathematical and physical investigations focus on understanding how complex patterns are created and which mechanisms cause their persistence. In this talk I will address one particular phenomenon which can be observed during the solidification process of metal alloys, called spinodal decomposition. Recent mathematical results will be presented for the Cahn-Hilliard equation, a partial differential equation modeling phase separation in metal alloys. These results describe the characteristics of generated patterns, as well as the surprising mechanism underlying their formation.

Monday, November 16, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Lou Kondic, Duke University [TOC]
TITLE: Pattern Formation in Non-Newtonian Hele-Shaw Flow

Abstract. We explore the morphology of patterns due to the Saffman-Taylor instability in Hele-Shaw cells and find that it can be dramatically altered by the non-Newtonian response of complex fluids such as liquid crystals and polymer solutions. The dense-branching morphology of Newtonian liquids may be replaced by dendritic fingers with stable tips and sidebranches.
Starting from a very general viscoelastic fluid model, we find a distinguished limit where shear thinning effect is dominant. A Darcy's law leads to the nonlinear boundary value problem for the pressure in the fluid. Full numerical simulations show that shear thinning alone modifies considerably the pattern formation and can produce fingers whose tip-splitting is suppressed, in agreement with experimental results. These fingers grow in an oscillating fashion, shedding "side-branches"' from their tips, closely resembling solidification patterns.

Monday, November 30, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zhiqiang Zhang, SUNY at Buffalo [TOC]
TITLE: One Dimensional Dynamics: Periodicity, Chaos and Entropy

Up Down (the following was posted on 1998/10/28 at 10:05)

Welcome to the Mathematics Department
Calendar

Wednesday, October 28, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Michel Cowen, SUNY at Buffalo [TOC]
TITLE: Curvature and Congruence of Holomorphic Exponential Curves

Thursday, October 29, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. Joyce McLaughlin, Rensselaer Polytechnic Institute [TOC]
TITLE: Natural Frequencies and Mode Shapes: Rich Data Sets

Abstract. Excite an object at a natural frequency. Make selected measurements of the response. This lecture describes how we analyze this data to find properties of the vibrating system.

Friday, October 30, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. William Menasco, SUNY at Buffalo [TOC]
TITLE: A Construction of Pseudo-Anosov Homeomorphisms-After Penner

Monday, November 2, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Hong Zhou, University of North Carolina, Chapel Hill [TOC]
TITLE: Modeling and Computation for Nonisothermal Fiber Processes

Abstract. Nonisothermal fiber processes have many applications, including liquid crystalline polymers and optical glass fibers. In particular, many ultra-strength textile fibers, e.g. Vectran and Kelvar, achieve their distinguished commercial properties (such as high tensile modulus) as a result of the interaction between anisotropic molecular-scale structure of the melt, macroscopic hydrodynamics of spinning flows, and nonisothermal effects.
Fiber spinning is one of the important techniques utilizing the flow-induced molecular orientation of liquid crystalline polymers (LCPs). We apply a fiber spinning model for lyotropic and thermotropic liquid crystalline polymers that couples hydrodynamics, anisotropic rod-like microstructural dynamics, free surface effects, and thermodynamics. Exploiting slender aspect ratio, we extract 1-D systems of nonlinear PDEs for ``longwave interactions'' of hydro/thermo/orientation. Fiber spinning steady states (BVP) and their stability are computed in realistic physical regimes, predicting spun fiber properties and process sensitivity. Trends in spinline performance due to material variations are very different in isothermal vs nonisothermal simulations. This result raises caution against application of isothermal models for real spinlines, and emphasizes the critical role of thermodynamics in spinning processes.

Wednesday, November 4, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Michel Cowen, SUNY at Buffalo [TOC]
TITLE: Curvature and Congruence of Holomorphic Exponential Curves, continued

Thursday, November 5, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Dr. William A. Massey, Lucent Technologies [TOC]
TITLE: Strong Approximations for Markovian Service Networks

Abstract: Inspired by service systems like telephone call centers, we develop limit theorems for a large class nonstationary Markov processes that we call stochastic service network models. The asymptotic limiting regime that we explore for these networks has a natural interpretation of scaling up the number of servers in response to a similar scaling up of the arrival rate for the customers.
We employ the theory of strong approximations to obtain functional strong laws of large numbers and functional central limit theorems for these networks. This gives us a tractable set of network fluid and diffusion approximations. The diffusion limits are obtained by using a new notion of non-smooth differentiation.
This is joint work with Marty Reiman of Bell Labs and Avi Mandelbaum of Technion.

Friday, November 6, 1998 - 3:15 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. John A. Pelesko, California Institute of Technology [TOC]
TITLE: Nonlinear Stability, Thermoelastic Contact, and the Barber Condition

Thermoelastic contact problems arise in areas as diverse as the study of automotive disk brakes, the production of metals, and the analysis of heat exchangers. In 1978, it was pointed out by J.R. Barber that the solution of such problems posed certain difficulties. In particular, the assumption of perfect insulation during a separated phase and perfect thermal contact during contact led to models with solutions which were unacceptable on physical grounds. Rejecting such solutions, Barber conjectured that these models failed to capture relevant physics and introduced a pressure dependent thermal boundary condition, which has since become known as the Barber condition. Since that time, various authors have explored the Barber condition and its implications for thermal contact problems. While such analyses have been extended to multiple materials, various geometries, and to numerical simulations, all theoretical work to date has relied upon linear stability theory. While this provides useful information about the existence of steady-states and their stability to infinitesimal perturbations, it fails to provide information about dynamics, history dependence, and nonlinear effects.
In this talk, we show how singular perturbation techniques may be used to investigate thermal contact problems. In particular, we consider two one-dimensional thermoelastic rod models. In the first, we introduce a modified Dirichlet boundary condition to simulate the effects of thermal contact on heat transfer. We show that this system undergoes a bifurcation from a single linearly stable steady-state solution to multiple steady-state solutions. We use multiple scale or two-timing methods to investigate the nonlinear behavior near the bifurcation point. In the second system studied, we replace the Dirichlet condition with the more physically realistic boundary condition introduced by Barber. Here the application of multiple scale methods becomes analytically intractable and we turn to matched asymptotics. Again, we investigate the behavior of the system near a bifurcation point,thereby obtaining information about dynamics, history dependence, and nonlinear effects.

Thursday, November 12, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. Thomas Wanner, University of Maryland/Baltimore County [TOC]
TITLE: Pattern Formation in Metal Alloys

Monday, November 16, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Lou Kondic, Duke University [TOC]
TITLE: Pattern Formation in Non-Newtonian Hele-Shaw Flow

Abstract. We explore the morphology of patterns due to the Saffman-Taylor instability in Hele-Shaw cells and find that it can be dramatically altered by the non-Newtonian response of complex fluids such as liquid crystals and polymer solutions. The dense-branching morphology of Newtonian liquids may be replaced by dendritic fingers with stable tips and sidebranches.
Starting from a very general viscoelastic fluid model, we find a distinguished limit where shear thinning effect is dominant. A Darcy's law leads to the nonlinear boundary value problem for the pressure in the fluid. Full numerical simulations show that shear thinning alone modifies considerably the pattern formation and can produce fingers whose tip-splitting is suppressed, in agreement with experimental results. These fingers grow in an oscillating fashion, shedding "side-branches"' from their tips, closely resembling solidification patterns.

Monday, November 30, 1998 - 4 p.m. - 103 Diefendorf Hall
GRADUATE STUDENT SEMINAR
SPEAKER: Mr. Zhiqiang Zhang, SUNY at Buffalo [TOC]
TITLE: One Dimensional Dynamics: Periodicity, Chaos and Entropy

Up Down (the following was posted on 1998/10/26 at 11:23)

Welcome to the Mathematics Department
Calendar

Wednesday, October 28, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Michel Cowen, SUNY at Buffalo [TOC]
TITLE: Curvature and Congruence of Holomorphic Exponential Curves

Thursday, October 29, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. Joyce McLaughlin, Rensselaer Polytechnic Institute [TOC]
TITLE: Natural Frequencies and Mode Shapes: Rich Data Sets
Abstract. Excite an object at a natural frequency. Make selected measurements of the response. This lecture describes how we analyze this data to find properties of the vibrating system.

Friday, October 30, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. William Menasco, SUNY at Buffalo [TOC]
TITLE: A Construction of Pseudo-Anosov Homeomorphisms-After Penner

Monday, November 2, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Hong Zhou, University of North Carolina, Chapel Hill [TOC]
TITLE: Modeling and Computation for Nonisothermal Fiber Processes

Abstract. Nonisothermal fiber processes have many applications, including liquid crystalline polymers and optical glass fibers. In particular, many ultra-strength textile fibers, e.g. Vectran and Kelvar, achieve their distinguished commercial properties (such as high tensile modulus) as a result of the interaction between anisotropic molecular-scale structure of the melt, macroscopic hydrodynamics of spinning flows, and nonisothermal effects.
Fiber spinning is one of the important techniques utilizing the flow-induced molecular orientation of liquid crystalline polymers (LCPs). We apply a fiber spinning model for lyotropic and thermotropic liquid crystalline polymers that couples hydrodynamics, anisotropic rod-like microstructural dynamics, free surface effects, and thermodynamics. Exploiting slender aspect ratio, we extract 1-D systems of nonlinear PDEs for ``longwave interactions'' of hydro/thermo/orientation. Fiber spinning steady states (BVP) and their stability are computed in realistic physical regimes, predicting spun fiber properties and process sensitivity. Trends in spinline performance due to material variations are very different in isothermal vs nonisothermal simulations. This result raises caution against application of isothermal models for real spinlines, and emphasizes the critical role of thermodynamics in spinning processes.

Wednesday, November 4, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Michel Cowen, SUNY at Buffalo [TOC]
TITLE: Curvature and Congruence of Holomorphic Exponential Curves, continued

Thursday, November 5, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Dr. William A. Massey, Lucent Technologies [TOC]
TITLE: Strong Approximations for Markovian Service Networks

Abstract: Inspired by service systems like telephone call centers, we develop limit theorems for a large class nonstationary Markov processes that we call stochastic service network models. The asymptotic limiting regime that we explore for these networks has a natural interpretation of scaling up the number of servers in response to a similar scaling up of the arrival rate for the customers.
We employ the theory of strong approximations to obtain functional strong laws of large numbers and functional central limit theorems for these networks. This gives us a tractable set of network fluid and diffusion approximations. The diffusion limits are obtained by using a new notion of non-smooth differentiation.
This is joint work with Marty Reiman of Bell Labs and Avi Mandelbaum of Technion.

Friday, November 6, 1998 - 3:15 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. John A. Pelesko, California Institute of Technology [TOC]
TITLE: Nonlinear Stability, Thermoelastic Contact, and the Barber Condition

Thermoelastic contact problems arise in areas as diverse as the study of automotive disk brakes, the production of metals, and the analysis of heat exchangers. In 1978, it was pointed out by J.R. Barber that the solution of such problems posed certain difficulties. In particular, the assumption of perfect insulation during a separated phase and perfect thermal contact during contact led to models with solutions which were unacceptable on physical grounds. Rejecting such solutions, Barber conjectured that these models failed to capture relevant physics and introduced a pressure dependent thermal boundary condition, which has since become known as the Barber condition. Since that time, various authors have explored the Barber condition and its implications for thermal contact problems. While such analyses have been extended to multiple materials, various geometries, and to numerical simulations, all theoretical work to date has relied upon linear stability theory. While this provides useful information about the existence of steady-states and their stability to infinitesimal perturbations, it fails to provide information about dynamics, history dependence, and nonlinear effects.
In this talk, we show how singular perturbation techniques may be used to investigate thermal contact problems. In particular, we consider two one-dimensional thermoelastic rod models. In the first, we introduce a modified Dirichlet boundary condition to simulate the effects of thermal contact on heat transfer. We show that this system undergoes a bifurcation from a single linearly stable steady-state solution to multiple steady-state solutions. We use multiple scale or two-timing methods to investigate the nonlinear behavior near the bifurcation point. In the second system studied, we replace the Dirichlet condition with the more physically realistic boundary condition introduced by Barber. Here the application of multiple scale methods becomes analytically intractable and we turn to matched asymptotics. Again, we investigate the behavior of the system near a bifurcation point,thereby obtaining information about dynamics, history dependence, and nonlinear effects.

Tuesday, November 17, 1998 - 4 p.m. - 103 Diefendorf Hall
SPECIAL LECTURE
SPEAKER: Prof. Lou Kondic, Duke University [TOC]
TITLE: Pattern Formation in Non-Newtonian Hele-Shaw Flow

Abstract. We explore the morphology of patterns due to the Saffman-Taylor instability in Hele-Shaw cells and find that it can be dramatically altered by the non-Newtonian response of complex fluids such as liquid crystals and polymer solutions. The dense-branching morphology of Newtonian liquids may be replaced by dendritic fingers with stable tips and sidebranches.
Starting from a very general viscoelastic fluid model, we find a distinguished limit where shear thinning effect is dominant. A Darcy's law leads to the nonlinear boundary value problem for the pressure in the fluid. Full numerical simulations show that shear thinning alone modifies considerably the pattern formation and can produce fingers whose tip-splitting is suppressed, in agreement with experimental results. These fingers grow in an oscillating fashion, shedding ``side-branches'' from their tips, closely resembling solidification patterns.

Up Down (the following was posted on 1998/10/21 at 14:34)

Welcome to the Mathematics Department
Calendar

Wednesday, October 21, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Ching Chou, SUNY at Buffalo [TOC]
TITLE: Fourier Algebras of Discrete Groups

Wednesday, October 28, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Michel Cowen, SUNY at Buffalo [TOC]
TITLE: Curvature and Congruence of Holomorphic Exponential Curves

Thursday, October 29, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Prof. Joyce McLaughlin, Rensselaer Polytechnic Institute [TOC]
TITLE: TBA

Friday, October 30, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: Prof. William Menasco, SUNY at Buffalo [TOC]
TITLE: A Construction of Pseudo-Anosov Hoemomorphisms-After Penner

Wednesday, November 4, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Michel Cowen, SUNY at Buffalo [TOC]
TITLE: Curvature and Congruence of Holomorphic Exponential Curves, continued

Thursday, November 5, 1998 - 4 p.m. - 103 Diefendorf Hall
MATHEMATICS COLLOQUIUM
SPEAKER: Dr. William A. Massey, Lucent Technologies [TOC]
TITLE: Strong Approximations for Markovian Service Networks

Abstract: Inspired by service systems like telephone call centers, we develop limit theorems for a large class nonstationary Markov processes that we call stochastic service network models. The asymptotic limiting regime that we explore for these networks has a natural interpretation of scaling up the number of servers in response to a similar scaling up of the arrival rate for the customers.
We employ the theory of strong approximations to obtain functional strong laws of large numbers and functional central limit theorems for these networks. This gives us a tractable set of network fluid and diffusion approximations. The diffusion limits are obtained by using a new notion of non-smooth differentiation.
This is joint work with Marty Reiman of Bell Labs and Avi Mandelbaum of Technion.

Up Down (the following was posted on 1998/10/20 at 13:02)

Welcome to the Mathematics Department
Calendar

Wednesday, October 21, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Ching Chou, SUNY at Buffalo [TOC]
TITLE: Fourier Algebras of Discrete Groups

Friday, October 23, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: To be announced. [TOC]

Wednesday, October 28, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Michel Cowen, SUNY at Buffalo [TOC]
TITLE: Curvature and Congruence of Holomorphic Exponential Curves

Friday, October 30, 1998 - 3:30 p.m. - 103 Diefendorf Hall
GEOMETRY/TOPOLOGY SEMINAR
SPEAKER: To be announced. [TOC]

Wednesday, November 4, 1998 - 4 p.m. - 103 Diefendorf Hall
ANALYSIS SEMINAR
SPEAKER: Prof. Michel Cowen, SUNY at Buffalo [TOC]
TITLE: Curvature and Congruence of Holomorphic Exponential Curves, continued

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Up Down (the following was posted on 1998/10/19 at 10:40)

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Welcome to the Mathematics Department
Calendar

Wednesday, October 21, 1998 - 4 p.m. - 103 Diefendorf Hall

ANALYSIS SEMINAR

SPEAKER: Prof. Ching Chou, SUNY at Buffalo [TOC]
TITLE: Fourier Algebras of Discrete Groups

Friday, October 23, 1998 - 3:30 p.m. - 103 Diefendorf Hall

GEOMETRY/TOPOLOGY SEMINAR

SPEAKER: To be announced. [TOC]

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Up Down (the following was posted on 1998/10/14 at 16:05)

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Welcome to the Mathematics Department
Calendar

Wednesday, October 14, 1998 - 4 p.m. - 103 Diefendorf Hall

ANALYSIS SEMINAR

SPEAKER: Prof. Mohan Ramachandran, SUNY at Buffalo [TOC]
TITLE: On Existence of Complete Kähler Metrics With Non-negative Sectional Curvature

Thursday, October 15, 1998 - 4 p.m. - 103 Diefendorf Hall

GEOMETRY/TOPOLOGY SEMINAR

SPEAKER: Prof. Thang Le, SUNY at Buffalo [TOC]
TITLE: The Kontsevich integral and finite type invariants of 3-manifolds continued.

Time Change

Friday, October 16, 1998 - 4:15 p.m. - 103 Diefendorf Hall

MATHEMATICS COLLOQUIUM

SPEAKER: Prof. Andreas Dress, CUNY [TOC]
TITLE: Combinatorics of Finite Metric Spaces with Applications to Phylogenetics

Abstract. Comparative phylogenetic analysis generally reveals a large array of similarities and dissimilarities between the various species under consideration. To derive phylogenetic branching patterns from that array (so that e.g. the kinship relation between horse, cow and whale could be elucidated), a rather "brutal", yet amazingly successful procedure has been to rally all the observed similarities and dissimilarities, for any two species, in just one number -- then called the (dis)similarity index of those two species. The resulting structure then is a finite metric space, and the associated task is to detect the branching pattern in question from analyzing this space.

While statistician have designed many useful procedures for analyzing such spaces, most of these methods (e.g. principal component analysis) perceive Euclidean n-space as the "standard of truth" and are designed to construct "good", if not (somehow) optimal embeddings of the given space into Euclidean space. Clearly, this is inadequate if phylogenetic branching patterns (and migration or diffusion in some large state space) are considered to be the cause for the observed dissimilarity patterns.

Wednesday, October 21, 1998 - 4 p.m. - 103 Diefendorf Hall

ANALYSIS SEMINAR

SPEAKER: Prof. Ching Chou, SUNY at Buffalo [TOC]
TITLE: Fourier Algebras of Discrete Groups

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Up Down (the following was posted on 1998/10/13 at 16:07)

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Welcome to the Mathematics Department
Calendar

Wednesday, October 14, 1998 - 4 p.m. - 103 Diefendorf Hall

ANALYSIS SEMINAR

SPEAKER: Prof. Mohan Ramachandran, SUNY at Buffalo [TOC]
TITLE: On Existence of Complete Kähler Metrics With Non-negative Sectional Curvature

Thursday, October 15, 1998 - 4 p.m. - 103 Diefendorf Hall

GEOMETRY/TOPOLOGY SEMINAR

SPEAKER: Prof. Thang Le, SUNY at Buffalo [TOC]
TITLE: The Kontsevich integral and finite type invariants of 3-manifolds continued.

Time Change

Friday, October 16, 1998 - 4:15 p.m. - 103 Diefendorf Hall

MATHEMATICS COLLOQUIUM

SPEAKER: Prof. Andreas Dress, CUNY [TOC]
TITLE: Combinatorics of Finite Metric Spaces with Applications to Phylogenetics

Abstract. Comparative phylogenetic analysis generally reveals a large array of similarities and dissimilarities between the various species under consideration. To derive phylogenetic branching patterns from that array (so that e.g. the kinship relation between horse, cow and whale could be elucidated), a rather "brutal", yet amazingly successful procedure has been to rally all the observed similarities and dissimilarities, for any two species, in just one number -- then called the (dis)similarity index of those two species. The resulting structure then