Seminars and Colloquia by Series

Series: Other Talks
Wednesday, September 30, 2009 - 13:00 , Location: Skiles 255 , Matt Baker , School of Mathematics, Georgia Tech , Organizer: John Etnyre
After a few remarks to tie up some loose ends from last week's talk on locally ringed spaces, I will discuss exact sequences of sheaves and give some natural examples coming from real, complex, and algebraic geometry. In the context of these examples, we'll see that a surjective map of sheaves (meaning a morphism of sheaves which is surjective on the level of stalks) need not be surjective on global sections. This observation will be used to motivate the need for "sheaf cohomology" (which will be discussed in detail in subsequent talks).
Series: Other Talks
Wednesday, September 23, 2009 - 13:00 , Location: Skiles 269 , Matt Baker , School of Mathematics, Georgia Tech , Organizer: John Etnyre
I will discuss how various geometric categories (e.g. smooth manifolds, complex manifolds) can be be described in terms of locally ringed spaces. (A locally ringed space is a topological spaces endowed with a sheaf of rings whose stalks are local rings.) As an application of the notion of locally ringed space, I'll define what a scheme is.
Series: Other Talks
Tuesday, September 22, 2009 - 11:00 , Location: ISyE Executive Classroom, Main Building , Michael J. Todd , School of Operations Research and Information Engineering, Cornell University , Organizer:
We discuss the convergence properties of first-order methods for two problems that arise in computational geometry and statistics: the minimum-volume enclosing ellipsoid problem and the minimum-area enclosing ellipsoidal cylinder problem for a set of m points in R^n. The algorithms are old but the analysis is new, and the methods are remarkably effective at solving large-scale problems to high accuracy.
Series: Other Talks
Wednesday, September 16, 2009 - 13:00 , Location: Skiles 255 , John Etnyre , Ga Tech , Organizer: John Etnyre
In these talks we will introduced the basic definitions and examples of presheaves, sheaves and sheaf spaces. We will also explore various constructions and properties of these objects.
Series: Other Talks
Monday, September 14, 2009 - 15:00 , Location: Student Services Building, Auditorium 117 , Richard Tapia , Rice University , Organizer: Robin Thomas
In this talk Professor Tapia identifies elementary mathematical frameworks for the study of popular drag racing beliefs. In this manner some myths are validated while others are destroyed. Tapia will explain why dragster acceleration is greater than the acceleration due to gravity, an age old inconsistency. His "Fundamental Theorem of Drag Racing" will be presented. The first part of the talk will be a historical account of the development of drag racing and will include several lively videos.
Series: Other Talks
Wednesday, September 9, 2009 - 13:00 , Location: Skiles 269 , John Etnyre , Ga Tech , Organizer: John Etnyre
In these talks we will introduced the basic definitions and examples of presheaves, sheaves and sheaf spaces. We will also explore various constructions and properties of these objects.
Series: Other Talks
Wednesday, September 2, 2009 - 13:00 , Location: Skiles 255 , John Etnyre , Ga Tech , Organizer: John Etnyre
In these talks we will introduced the basic definitions and examples of presheaves, sheaves and sheaf spaces. We will also explore various constructions and properties of these objects.
Series: Other Talks
Wednesday, July 1, 2009 - 12:00 , Location: Skiles 255 , Pablo Laguna , School of Physics, Georgia Tech , Organizer:
This will be an informal seminar with a discussion on some mathematical problems in relativistic astrophysics, and discuss plans for future joint seminars between the Schools of Mathematics and Physics.
Series: Other Talks
Monday, April 13, 2009 - 16:30 , Location: Skiles 269 , Jozsef Solymosi , Math, UBC , Organizer: Prasad Tetali
An old conjecture of Erdos and Szemeredi states that if A is a finite set of integers then the sum-set or the product-set should be large. The sum-set of A is A + A={a+b | a,b \in A\}, and the product set is defined in a similar way, A*A={ab | a,b \in A}. Erdos and Szemeredi conjectured that the sum-set or the product set is almost quadratic in |A|, i.e. max(|A+A|,|A*A|)> c|A|^{2-\epsilon}. In this talk we review some recent developments and problems related to the conjecture.
Series: Other Talks
Wednesday, March 25, 2009 - 15:00 , Location: Howey Physics Lecture Room 5 , Roger Penrose , Mathematical Institute, University of Oxford , Organizer: Stavros Garoufalidis
Twistor theory is now over 45 years old. In December 1963, I proposed the initial ideas of this scheme, based on complex-number geometry, which presents an alternative perspective to that of standard 4-dimensional space-time, for the basic arena in which (quantum) physics takes place. Over the succeeding years, there were numerous intriguing developments. But many of these were primarily mathematical, and there was little interest expressed by the physics community. Things changed rather dramatically, in December 2003, when E. Witten produced a 99-page article initiating the subject of “twistor-string theory” this providing a novel approach to high-energy scattering processes. In this talk, I shall provide an account of the original geometrical and physical ideas, and also outline various recent developments, some of which may help our understandings of the seeming paradoxes of quantum mechanics.

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