Forthcoming Seminars

Tue, 09/02/2010
14:00 		Tom Coates (Imperial College London) Algebraic and Symplectic Geometry Seminar Add to calendar SR1
(HoRSe seminar) Gromov-Witten Invariants and Modular Forms I
I will show that generating functions for certain non-compact Calabi-Yau 3-folds are modular forms. This is joint work with Hiroshi Iritani.
Tue, 09/02/2010
14:30 		David Conlon (Cambridge) Combinatorial Theory Seminar Add to calendar L3
Combinatorial theorems in random sets
The famous theorem of Szemerédi says that for any natural number $ k $ and any $ a>0 $ there exists $ n $ such that if $ N\ge n $ then any subset $ A $ of the set $ [N] =\{1, 2,\ldots , N\} $ of size $ |A| \ge a N $ contains an arithmetic progression of length $ k $. We consider the question of when such a theorem holds in a random set. More precisely, we say that a set $ X $ is $ (a, k) $-Szemerédi if every subset $ Y $ of $ X $ that contains at least $ a|X| $ elements contains an arithmetic progression of length $ k $. Let $ [N]_p $ be the random set formed by taking each element of $ [N] $ independently with probability $ p $. We prove that there is a threshold at about $ p = N^{-1/(k-1)} $ where the probability that $ [N]_p $ is $ (a, k) $-Szemerédi changes from being almost surely 0 to almost surely 1. There are many other similar problems within combinatorics. For example, Turán’s theorem and Ramsey’s theorem may be relativised, but until now the precise probability thresholds were not known. Our method seems to apply to all such questions, in each case giving the correct threshold. This is joint work with Tim Gowers.
Tue, 09/02/2010
15:45 		Tom Coates (Imperial College London) Algebraic and Symplectic Geometry Seminar Add to calendar L3
(HoRSe seminar) Gromov-Witten Invariants and Modular Forms II
I will show that generating functions for certain non-compact Calabi-Yau 3-folds are modular forms. This is joint work with Hiroshi Iritani.
Tue, 09/02/2010
16:00 		Jessica Banks (Oxford) Junior Geometric Group Theory Seminar Add to calendar SR1
The Alexander Polynomial
The Alexander polynomial of a link was the first link polynomial. We give some ways of defining this much-studied invariant, and derive some of its properties.
Tue, 09/02/2010
17:00 		Jaroslav Zemanek (Polish Academy of Sciences) Functional Analysis Seminar Add to calendar L3
ERGODIC THEORY FOR HOLOMORPHIC MAPPINGS
Wed, 10/02/2010
11:30 		Algebra Kinderseminar Add to calendar
NO SEMINAR
Thu, 11/02/2010
12:00 		Hwasung Mars Lee (Oxford) Junior Geometry and Topology Seminar Add to calendar SR1
An overview of the SYZ conjecture and calibrated geometry
We will present a physical motivation of the SYZ conjecture and try to understand the conjecture via calibrated geometry. We will define calibrated submanifolds, and also give sketch proofs of some properties of the moduli space of special Lagrangian submanifolds. The talk will be elementary and accessible to a broad audience.
Thu, 11/02/2010
14:00 		Dr. Melina Freitag (University of Bath) Computational Mathematics and Applications Add to calendar Rutherford Appleton Laboratory, nr Didcot
Resolution of sharp fronts in the presence of model error in variational data assimilation
We show that data assimilation using four-dimensional variation (4DVar) can be interpreted as a form of Tikhonov regularisation, a familiar method for solving ill-posed inverse problems. It is known from image restoration problems that $ L_1 $-norm penalty regularisation recovers sharp edges in the image better than the $ L_2 $-norm penalty regularisation. We apply this idea to 4DVar for problems where shocks are present and give some examples where the $ L_1 $-norm penalty approach performs much better than the standard $ L_2 $-norm regularisation in 4DVar.
Thu, 11/02/2010
14:30 		Mary Schaps (Bar Ilan, Israel) Representation Theory Seminar Add to calendar L3
Generating the crystal graph for cyclotomic Hecke algebras
Thu, 11/02/2010
16:00 		Tamas Hausel (Oxford) Seminar Add to calendar SR1
Mirror Symmetry, Langlands duality and the Hitchin System
tba
Thu, 11/02/2010
16:30 		Peter Howell (OCIAM) Differential Equations and Applications Seminar Add to calendar DH 1st floor SR
Spinning viscous sheets, or pizza, pancakes and doughnuts
We study the axisymmetric stretching of a thin sheet of viscous fluid driven by a centrifugal body force. Time-dependent simulations show that the sheet radius tends to infinity in finite time. As the critical time is approached, the sheet becomes partitioned into a very thin central region and a relatively thick rim. A net momentum and mass balance in the rim leads to a prediction for the sheet radius near the singularity that agrees with the numerical simulations. By asymptotically matching the dynamics of the sheet with the rim, we find that the thickness in the central region is described by a similarity solution of the second kind. For non-zero surface tension, we find that the similarity exponent depends on the rotational Bond number B, and increases to infinity at a critical value B=1/4. For B>1/4, surface tension defeats the centrifugal force, causing the sheet to retract rather than stretch, with the limiting behaviour described by a similarity solution of the first kind.
Thu, 11/02/2010
17:00 		Alexandre Borovik (Manchester) Logic Seminar Add to calendar L3
Pseudofinite groups and groups of finite Morley rank
The talks will discuss relations between two major conjectures in the theory of groups of finite Morley rank, a modern chapter of model theoretic algebra. One conjecture, the famous the Cherlin-Zilber Algebraicity Conjecture formulated in 1970-s states that infinite simple groups of finite Morley rank are isomorphic to simple algebraic groups over algebraically closed fields. The other conjecture, due to Hrushovski and more recent, states that a generic automorphism of a simple group of finite Morley rank has pseudofinite group of fixed points. Hrushovski showed that the Cherlin-Zilber Conjecture implies his conjecture. Proving Hrushovski's Conjecture and reversing the implication would provide a new efficient approach to proof of Cherlin-Zilber Conjecture. Meanwhile, the machinery that is already available for the work at pseudofinite/finite Morley rank interface already yields an interesting result: an alternative proof of the Larsen-Pink Theorem (the latter says, roughly speaking, that "large" finite simple groups of matrices are Chevalley groups over finite fields).
Fri, 12/02/2010
10:00 		Dr Raj Mani (University of Southampton) Industrial and Interdisciplinary Workshops Add to calendar DH 1st floor SR
Why wound healers need models
The significance of the effects of non-healing wounds has been the topic of many research papers and lectures during the last 25 years. Efforts have been made to understand the effects of long-standing venous hypertension, diabetes, the prevalence of wounds in such conditions with as well as the difficulties faced in managing such wounds with some success. Successful efforts to define standard care regimes have also been made. However, attempts to introduce innovative therapy have been much less successful. Is this merely because we have not understood the intricacies of the problem? And would system based modelling be an untried technique? Venous ulcers are the majority of lower extremity wounds, and a clinical challenge. A previously developed model of venous ulcers permits some understanding of why compression bandaging is successful but fails to accommodate complications such as exudate and infection. Could this experimental model be improved by system based modelling? Chronic wounds need to be modelled however the needs for such models should be examined in order that the outcome permits advances in our thinking as well in clinical management.
Fri, 12/02/2010
11:30 		Various (Oxford) Industrial and Interdisciplinary Workshops Add to calendar OCCAM Common Room (RI2.28)
OCCAM group meeting
Fri, 12/02/2010
12:00 		Mat Bullimore (Oxford) Twistor Workshop Add to calendar Gibson 1st Floor SR
Local space-time physics from the grassmannian
Based on hep-th/0912.3249 by Arkani-Hamed et. al..
Fri, 12/02/2010
14:15 		Alexander Scheid Nomura Seminar Add to calendar L1
Order book resilience, price manipulation, and Fredholm integral equations
The viability of a market impact model is usually considered to be equivalent to the absence of price manipulation strategies in the sense of Huberman & Stanzl (2004). By analyzing a model with linear instantaneous, transient, and permanent impact components, we discover a new class of irregularities, which we call transaction-triggered price manipulation strategies. Transaction-triggered price manipulation is closely related to the non-existence of measure-valued solutions to a Fredholm integral equation of the first kind. We prove that price impact must decay as a convex decreasing function of time to exclude these market irregularities along with standard price manipulation. We also prove some qualitative properties of optimal strategies and provide explicit expressions for the optimal strategy in several special cases of interest. Joint work with Aurélien Alfonsi, Jim Gatheral, and Alla Slynko.
Fri, 12/02/2010
14:30 		Dr Poul Christoffersen (Cambridge SPRI) Mathematical Geoscience Seminar Add to calendar DH 3rd floor SR
Observing and modelling processes at the base of the Antarctic Ice Sheet
TBA
Mon, 15/02/2010
12:00 		Sergio Benvenuti (Imperial College) String Theory Seminar Add to calendar L3
N=2 Superconformal Theories and M5 branes
In 2009 there was progress in understanding and classifying the set of four dimensional field theories with N=2 SUSY. These models arise as M5 branes wrapped over a Riemann surface. We review this construction and describe a five dimensional point of view, using (p,q)-webs of 5-branes in Type IIB string theory. This point of view makes many properties of the theories explicit. We will also touch on the AGT correspondence, that associates a 2-dimensional CFT, similar to the Liouville CFT, to the protected sector of four dimensional N=2 models.

For any corrections/updates to these listings, please contact seminars [-at-] maths [dot] ox [dot] ac [dot] uk.

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