Forthcoming events in this series


Tue, 11 Mar 2014
15:30
Comlab

"Bayesian networks, information and entropy"

John Baez
(University of California)
Abstract

Nature and the world of human technology are full of
networks. People like to draw diagrams of networks: flow charts,
electrical circuit diagrams, signal flow diagrams, Bayesian networks,
Feynman diagrams and the like. Mathematically-minded people know that
in principle these diagrams fit into a common framework: category
theory. But we are still far from a unified theory of networks.

Tue, 11 Mar 2014
12:00
L6

Intrinsic and extrinsic regulation of epithelial organ growth

Jeremiah Zartman
(University of Notre Dame)
Abstract

The revolution in molecular biology within the last few decades has led to the identification of multiple, diverse inputs into the mechanisms governing the measurement and regulation of organ size. In general, organ size is controlled by both intrinsic, genetic mechanisms as well as extrinsic, physiological factors. Examples of the former include the spatiotemporal regulation of organ size by morphogen gradients, and instances of the latter include the regulation of organ size by endocrine hormones, oxygen availability and nutritional status. However, integrated model platforms, either of in vitro experimental systems amenable to high-resolution imaging or in silico computational models that incorporate both extrinsic and intrinsic mechanisms are lacking. Here, I will discuss collaborative efforts to bridge the gap between traditional assays employed in developmental biology and computational models through quantitative approaches. In particular, we have developed quantitative image analysis techniques for confocal microscopy data to inform computational models – a critical task in efforts to better understand conserved mechanisms of crosstalk between growth regulatory pathways. Currently, these quantitative approaches are being applied to develop integrated models of epithelial growth in the embryonic Drosophila epidermis and the adolescent wing imaginal disc, due to the wealth of previous genetic knowledge for the system. An integrated model of intrinsic and extrinsic growth control is expected to inspire new approaches in tissue engineering and regenerative medicine.

Tue, 04 Mar 2014
15:30
Comlab

"Stochastic Petri nets, chemical reaction networks and Feynman diagrams"

John Baez
(University of California)
Abstract

 Nature and the world of human technology are full of
networks. People like to draw diagrams of networks: flow charts,
electrical circuit diagrams, signal flow diagrams, Bayesian networks,
Feynman diagrams and the like. Mathematically-minded people know that
in principle these diagrams fit into a common framework: category
theory. But we are still far from a unified theory of networks.

Tue, 25 Feb 2014
15:30
Comlab

"Electrical circuits and signal flow diagrams"

John Baez
(University of California)
Abstract

Nature and the world of human technology are full of
networks. People like to draw diagrams of networks: flow charts,
electrical circuit diagrams, signal flow diagrams, Bayesian networks,
Feynman diagrams and the like. Mathematically-minded people know that
in principle these diagrams fit into a common framework: category
theory. But we are still far from a unified theory of networks.

Fri, 21 Feb 2014
14:00
Comlab

"Network theory: an overview"

John Baez
(University of California)
Abstract

Nature and the world of human technology are full of
networks. People like to draw diagrams of networks: flow charts,
electrical circuit diagrams, signal flow diagrams, Bayesian networks,
Feynman diagrams and the like. Mathematically-minded people know that
in principle these diagrams fit into a common framework: category
theory. But we are still far from a unified theory of networks.

Thu, 30 Jan 2014
11:00
L5

Locomotion of microorganisms in complex fluids

Prof Roberto Zenit
(Universidad Nacional Autonoma de Mexico)
Abstract

The fundamental mechanisms of microorganism motility have been extensively studied in the past. Most previous work focused on cell locomotion in simple (Newtonian) fluids.
However, in many cases of biological importance (including mammalian reproduction and bacterial infections), the fluids that surround the organisms are strongly non-Newtonian (so-called complex fluids), either because they have shear-dependent viscosities, or because they display an elastic response. These non-Newtonian effects challenge the most fundamental intuition in fluid mechanics, resulting in our incapacity to predict its implications in biological cell locomotion. In this talk, our on-going experimental investigation to quantify the effect of non-Newtonian behavior on the locomotion and fluid transport of microorganisms will be described. Several types of magnetic micro-robots were designed and built. These devices were actuated to swim or move in a variety of fluids : Newtonian, elastic with constant viscosity (Boger fluids) or inelastic with shear-thinning viscosity. We have found that, depending on the details of locomotion, the swimming performance can either be increased, decreased or remain unaffected by the non Newtonian nature of the liquid. Some key elements to understand the general effect of viscoelasticity and shear-thinning viscosity of the motility of microorganisms will be discussed.

Wed, 22 Jan 2014
13:30
L5

"Equivalences"

Emily Cliff
(Oxford University)
Wed, 11 Dec 2013

18:00 - 19:00
L2

A Mathematical Path to a Professional Betting Career - OCCAM Public Lecture

Professor Alistair Fitt
(Oxford Brookes University)
Abstract

Question: Is it a realistic proposition for a mathematician to use his/her skills to make a living from sports betting? The introduction of betting exchanges have fundamentally changed the potential profitability of gambling, and a professional mathematician's arsenal of numerical and theoretical weapons ought to give them a huge natural advantage over most "punters", so what might be realistically possible and what potential risks are involved? This talk will give some idea of the sort of plan that might be required to realise this ambition, and what might be further required to attain the aim of sustainable gambling profitability.

Fri, 19 Apr 2013
09:20

Deformation Week - Day 4

Abstract

A workshop on different aspects of deformation theory in various fields

Thu, 18 Apr 2013
10:00

Deformation Week - Day 3

Abstract

A workshop on different aspects of deformation theory in various fields

Wed, 17 Apr 2013
10:00

Deformation Week - Day 2

Abstract

A workshop on different aspects of deformation theory in various fields

Tue, 16 Apr 2013
11:00

Deformation Week - Day 1

Abstract

A workshop on different aspects of deformation theory in various fields

Thu, 26 Jul 2012
14:00
DH 1st floor SR

Uniqueness of the asymptotic empirical distribution of the aligned letter pairs in an optimal alignment of random sequences

Prof. Henry Matzinger
(Georgia Institute of Technology)
Abstract

We consider two independent random sequences of length n.
We consider optimal alignments according to a scoring function S.
We show that when the scoring function S is chosen at random
then with probability 1, the frequency of the aligned letter pairs
converges to a unique distribution as n goes to infinity. We also show
some concentration of measure phenomena.

Fri, 13 Apr 2012
15:00
DH 1st floor SR

Networks, Communities and the Ground-Truth

Jure Leskovec
(Stanford University)
Abstract

Nodes in complex networks organize into communities of nodes that share a common property, role or function, such as social communities, functionally related proteins, or topically related webpages. Identifying such communities is crucial to the understanding of the structural and functional roles of networks.

Current work on overlapping community detection (often implicitly) assumes that community overlaps are less densely connected than non-overlapping parts of communities. This is unnatural as it means that the more communities nodes share, the less likely it is they are linked. We validate this assumption on a diverse set of large networks and find an increasing relationship between the number of shared communities of a pair of nodes and the probability of them being connected by an edge, which means that parts of the network where communities overlap tend to be more densely connected than the non-overlapping parts of communities.

Existing community detection methods fail to detect communities with such overlaps. We propose a model-based community detection method that builds on bipartite node-community affiliation networks. Our method successfully detects overlapping, non-overlapping and hierarchically nested communities. We accurately identify relevant communities in networks ranging from biological protein-protein interaction networks to social, collaboration and information networks. Our results show that while networks organize into overlapping communities, globally networks also exhibit a nested core-periphery structure, which arises as a consequence of overlapping parts of communities being more densely connected.

Tue, 06 Mar 2012
10:00
SR1

Generalized Kahler structures on moduli space of instantons

Gil Cavalcanti
Abstract

We show how the reduction procedure for generalized Kahler  
structures can be used to recover Hitchin's results about the  
existence of a generalized Kahler structure on the moduli space of  
instantons on bundle over a generalized Kahler manifold. In this setup  
the proof follows closely the proof of the same claim for the Kahler  
case and clarifies some of the stranger considerations from Hitchin's  
proof.

Fri, 24 Feb 2012

14:00 - 15:30
Comlab

Homotopy Type Theory

Kobi Kremnizer
(Oxford)
Abstract

In recent years, surprising connections between type theory and homotopy theory have been discovered. In this talk I will recall the notions of intensional type theories and identity types. I will describe "infinity groupoids", formal algebraic models of topological spaces, and explain how identity types carry the structure of an infinity groupoid. I will finish by discussing categorical semantics of intensional type theories.

The talk will take place in Lecture Theatre B, at the Department of Computer Science.

Fri, 17 Feb 2012

10:30 - 12:00
Comlab

Algebraic theories and locally presentable categories

Kobi Kremnizer
(Oxford)
Abstract

Algebraic theories, locally presentable categories and their application to type theories. The seminar will take place in Lecture Theatre A of the Department of Computer Science.

Fri, 03 Feb 2012

10:30 - 12:00
Comlab

Contextuality and Non-Locality: a geometric perspective

Samson Abramsky
(Oxford)
Abstract

The seminar will take place in Lecture Theatre A, Department of Computer Science.

-------------------

Contextuality and non-locality are features of quantum mechanics which stand in sharp contrast to the realistic picture underlying classical physics. We shall describe a unified geometric perspective on these notions in terms of *obstructions to the existence of global sections*. This allows general results and structural notions to be uncovered, with quantum mechanics appearing as a special case. The natural language to use here is that of sheaves and presheaves; and cohomological obstructions can be defined which witness contextuality in a number of salient examples.

This is joint work with Adam Brandenburger
 http://iopscience.iop.org/1367-2630/13/11/113036/
 http://arxiv.org/abs/1102.0264

and Shane Mansfield and Rui Soares Barbosa
 http://arxiv.org/abs/1111.3620

Fri, 27 Jan 2012

11:00 - 12:00
Comlab

Topological quantum field theories (TQFTs) and the cobordism hypothesis

André Henriques
(Utrecht)
Abstract

Introductory talk on topological quantum field theories (TQFTs) and the cobordism hypothesis, focusing on the conceptual issues involved.

The lecture will take place this Friday at 11am in Lecture Theatre A of the Department of Computer Science

Fri, 20 Jan 2012

10:30 - 12:00
Comlab

Selling category theory to the masses: a tale of food, spiders and Google

Bob Coecke
(Oxford)
Abstract

We will demonstrate the following. Category theory, usually conceived as some very abstract form of metamathematics, is present everywhere around us. Explicitly, we show how it provides a kindergarten version of quantum theory, an how it will help Google to understand sentences rather than words.

Some references are:

-[light] BC (2010) "Quantum picturalism". Contemporary Physics 51, 59-83. arXiv:0908.1787 
-[a bit heavier] BC and Ross Duncan (2011) "Interacting quantum observables: categorical algebra and diagrammatics". New Journal of Physics 13, 043016. arXiv:0906.4725
-[light] New Scientist (8 December 2010) "Quantum links let computers understand language". www.cs.ox.ac.uk/people/bob.coecke/NewScientist.pdf
-[a bit heavier] BC, Mehrnoosh Sadrzadeh and Stephen Clark (2011) "Mathematical foundations for a compositional distributional model of meaning". Linguistic Analysis - Lambek Festschrift. arXiv:1003.439

Thu, 21 Jul 2011 00:00 -
Fri, 22 Jul 2011 18:00
L2

Twistors, Geometry and Physics in honour of Sir Roger Penrose

Abstract

This meeting will mark the 80th birthday of Sir Roger Penrose. Twistor theory is one of his most remarkable discoveries and continues to have applications across pure mathematics and mathematical physics. This meeting will focus on some recent developments with speakers both on geometry and physics.

Speakers:

  • Nima Arkani-Hamed (IAS, Princeton): Scattering without space-time
  • Mike Eastwood (ANU): CR geometry and conformal foliations
  • Nigel Hitchin (Oxford): Twistors and Octonions
  • Andrew Hodges (Oxford): Polytopes and amplitudes
  • Claude LeBrun (SUNY Stony Brook): On Hermitian, Einstein 4-Manifolds
  • David Skinner (Perimeter Institute): Scattering amplitudes from holomorphic linking in twistor space
  • Paul Tod (Oxford): Conformal cyclic cosmology

Registration will start at 1.30pm on the 21st with the first lecture at 2.15pm. The meeting will finish by 4.30pm on the 22nd. See the programme for more details.

There will be a reception at 6.30pm on the 21st July (Wadham College) followed by dinner at 7.15 in Wadham College.