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Events
Recent Developments in Quantum Field Theory

MPI für Mathematik in den Naturwissenschaften Leipzig

G3 10 (Lecture hall)

conference

20/07/2007 22/07/2007

Recent Developments in Quantum Field Theory

The basic idea of the conference is to bring together a mixture of young and well-established researchers, both working at the forefront of quantum field theory and quantum gravity, to discuss their contributions to the recent developments within their respective fields. The fields to be covered are

String Theory
Loop Quantum Gravity
Quantum Field Theory on Curved Space-Time
Non-Commutative Field Theory/Geometry as well as the different approaches to quantum field theory and quantum gravity using
Topos Theory.

The number of participants is limited not to exceed 35 - 40 internationally well-recognized scientists. We hope that such a small number of invited scientists will allow a lively discussion of the subject of the conference.

We plan to have about 12 talks of 45 - 60 minutes each (three in the morning and two in the afternoon session), which are thought to build the bases of the ensuing discussions. The latter are regarded to build the `core' of the meeting.

Speakers

Sergio Albeverio

Germany

Matthias Blau

Switzerland

Martin Bojowald

USA

Christian Brouder

France

Andreas Döring

United Kingdom

Felix Finster

Germany

Klaus Fredenhagen

Germany

Hanno Gottschalk

Germany

Partha Guha

Germany and India

Stefan Hollands

Germany

Dirk Kreimer

France and USA

Karl-Georg Schlesinger

Austria

Thomas Thiemann

Canada and Germany

Adrian Vajiac

USA

Stefan Waldmann

Germany

Program

13:00 - 14:00	Welcome and Opening
15:00 - 15:45	The renormalization group in perturbative algebraic quantum field theory: (based on joint work with R. Brunetti and M. Dütsch) Following previous work of Hollands and Wald a local version of the renormalization group is developped within the framework of perturbative algebraic quantum field theory. The new formulation admits in particular a detailed analysis of the influence of mass terms.
16:00 - 16:45	Thomas Thiemann (Canada) Loop Quantum Gravity We summarise the current status of Loop Quantum Gravity. We focus on recent advances concerning the quantum dynamics and the classical limit of the theory.
16:45 - 17:15	Coffee Break
17:15 - 18:00	Karl-Georg Schlesinger (Austria) Some steps towards noncommutative mirror symmetry We start by reviewing some small aspects of the recent work of Kapustin and Witten [KW] on S-duality and the Geometric Langlands Program, especially how this leads to the question of an extension of mirror symmetry to noncommutative spaces. Next, we consider the application of one of the steps of [KW] to the gauge theory on the D5-brane worldvolume in Type IIB string theory. We will see that in this case the inclusion of noncommutative deformations is no longer just an option but is necessary in the generic case. We will show that in a special case one can factorize the fields in such a way that one can reduce everything to questions on mirror symmetry on the noncommutative 2-torus. Following the - by now classical - approach of Dijkgraaf to mirror symmetry on elliptic curves, we will see how q-deformations of special functions arise. We will pose the qustion how this is related to field theories on the noncommutative 2-torus.
18:30 - 19:30	Welcome Dinner

09:00 - 09:45	Christian Brouder (France) The structure of Green functions in quantum field theory with a non-Gaussian measure In quantum field theory with a non-Gaussian measure, the Green functions are described by Feynman diagrams that are built, not only from a single two-legged free propagator g(x,y), but from n-legged free propagators, where n is any natural number. This increases considerably the combinatorial difficulty of the theory. Moreover, in the application of non-Gaussian QFT to many-body physics, all n-legged free propagators with n different from 2 are solutions of the free Schroedinger equation. Therefore, we are not allowed to use the inverse of g(x,y) to amputate Green functions because this would kill non-Gaussian contributions to the Green function. As a consequence, computational methods based on the Legendre transformation are not available. For these reasons, the structure of non-Gaussian Green functions were poorly investigated despite their importance for the calculation of strongly-correlated systems. In this talk, the Hopf algebraic methods developed by Fauser, Frabetti, Oeckl and Mestre will be used to solve this problem.
10:00 - 10:45	Matthias Blau (Switzerland) Plane Wave Geometry and Quantum Physics As an embryonic example of the interplay between geometry and quantum physics in string theory (an example that requires neither knowledge nor appreciation of string theory but also does not do justice to the depth and richness of these ideas in the string theory context), we consider the interplay between geometric properties of plane wave space-time metrics on the one hand and corresponding statements about quantum (gauge) theories on the other.
10:45 - 11:15	Coffee Break
11:15 - 12:00	Felix Finster (Germany) Fermion systems in discrete space-time and their continuum limit The principle of the fermionic projector provides a new model of space-time together with the mathematical framework for the formulation of physical equations. After a general introduction to the mathematical setting of fermion systems in discrete space-time, we discuss the underlying physical principles. We set up a variational principle which is symmetric under permutations of the space-time points. We describe a mechanism of spontaneous breaking of this permutation symmetry which leads to relations between the space-time points, in particular to the generation of a so-called discrete causal structure. The connection to the space-time continuum is outlined, and obtained results for the effective continuum theory are given.
12:30 - 13:30	Lunch
15:00 - 15:45	Sergio Albeverio (Germany) TBA
16:00 - 16:45	Hanno Gottschalk (Germany) AdS/CFT correspondence: lessons from constructive field theory Following ideas of Dütsch and Rehren, we give a proof of the equivalence of the two prescriptions of the conformal boundary field in AdS/CFT ("duality"). We use rigorous Euclidean path integrals to define functional delta functions of boundary values and restrictions to the conformal boundary. Both, in the interacting and non-interacting case, divergences arise that have not been observed so far. These divergences can, however, be removed without doing damage to reflection positivity and symmetry. Interactions with IR cut-off are taken into account in D=2 dimensional Euclidean AdS. We comment on some intriguing novel features of the IR-problem which comes from the fact that boundary sources in AdS/CFT lead to shifts in the bulk interaction that create an infinite amount of energy. This talk is based on joint work with Horst Thaler, math-ph/0611006.
16:45 - 17:15	Coffee Break
17:15 - 18:00	Partha Guha (Germany) Witten's formula, cohomological pairings for flat connections and applications of multiple zeta functions We use Witten's volume formula to calculate the cohomological pairings of the moduli space of flat $SU(3)$ connections. The cohomological pairings of moduli space of flat $SU(2)$ connections is known from the work of Thaddeus-Witten-Donaldson, but for higher holonomy groups these pairings are largely unknown. We make some progress on these problems, and show that the pairings can be expressed in terms of multiple zeta functions.
18:15 - 19:00	Adrian Vajiac (USA) Equivariant Localization Techniques in Topological Quantum Field Theories We present how TQFTs of cohomological type can be described in the context of equivariant cohomology. In this setup, we show how appropriate equivariant localization formulas can be applied to the correlation functions of these theories, yielding to a simpler description of the path integrals involved. In particular, for the topological Yang-Mills theory in four dimensions, we derive (at least formally) Witten's conjecture relating Donaldson and Seiberg-Witten invariants. We conclude by presenting several ideas on how to replace the formal aspects of these techniques with rigorous arguments.

09:00 - 09:45	Stefan Waldmann (Germany) Deformation Quantization of Surjective Submersions In this talk I will discuss a definition of what a deformation quantization of a surjective submersion should be. Using a purely cohomological approach yields existence and classification up to a natural notion of equivalence. The main application is the deformation quantization of principal fiber bundles which I will discuss in some detail. In particular, they can still be used to associate vector bundles, now in the deformed framework.
10:00 - 10:45	Martin Bojowald (USA) Canonical Quantum Gravity and Effective Theory Effective actions provide a powerful way to understand low-energy, semiclassical or other regimes of quantum field theories. Although canonical quantum gravity theories, such as loop quantum gravity, are not directly accessible to the usual techniques of computing effective actions, equivalent methods to derive an effective Hamiltonian and effective equations have recently been developed. This provides means to study the semiclassical limit of loop quantum gravity, demonstrating the correct approach to classical behavior and including quantum correction terms. Salient features of loop quantum gravity, its effective equations and applications in cosmological regimes will be discussed.
10:45 - 11:15	Coffee Break
11:15 - 12:00	Dirk Kreimer (France) Renormalization for a non-renormalizable theory: remarks on gravity We compare the structure of the Dyson Schwinger equations (DSE) for three different situations: the case of a renormalizable field theory, a generic non-renormalizable theory and pure gravity. We use the Hochschild cohomology of the underlying Hopf algebra to formulate the relevant DSEs. Remarkably, it turns out that gravity is much better behaved than a generic non-renormalizable theory with respect to its Hochschild cohomology and discuss some consequences.
12:30 - 13:30	Lunch
15:00 - 15:45	Stefan Hollands (Germany) Background independence in field theory We review what it means for a field theory to be background-independent, and then analyze how this property may be formulated at the quantum level. We discuss how background independence at the classical level may be broken at the quantum level, and we mention some implications for quantum gravity.
16:00 - 16:45	Andreas Döring (United Kingdom) Physical systems as Topoi In this talk, I will report on recent work with Chris Isham. The basic idea is that a physical system can be represented by structures within a suitable topos associated with the system. The choice of the topos depends on the type of the system (classical, quantum or even some new kind). Within the topos, there is a state object and a quantity value object, and physical quantitites are suitable morphisms between them. Propositions about physical quantities are represented by subobjects of the state object, which form a Heyting algebra. A tentative set of rules for formulating physical theories within a topos that does not fundamentally depend on the continuum (in the form of the real or complex numbers) is presented.
16:45 - 17:15	Coffee Break
17:15 - 18:00	Closing Discussion
18:30 - 19:30	Farewell Dinner

Participants

Sergio Albeverio

Germany

Dorothea Bahns

Germany

Matthias Blau

Switzerland

Martin Bojowald

USA

Christian Brouder

France

Johannes Brunnemann

Germany

Christoph Dehne

Germany

Andreas Döring

United Kingdom

Michael Dütsch

Germany

Bertfried Fauser

Germany

Felix Finster

Germany

Christian Fleischhack

Germany

Klaus Fredenhagen

Germany

Domenico Giulini

Germany

Hanno Gottschalk

Germany

Partha Guha

Germany

Allen C. Hirshfeld

Germany

Stefan Hollands

Germany

Reinhard Illge

Germany

Dirk Kreimer

France

Gandalf Lechner

Germany

Manfred Liebmann

Germany

Kishore Marathe

USA

Gregory Naber

USA

Mario Paschke

Germany

Denis Perrot

France

Hartmann Römer

Germany

Gerd Rudolph

Germany

Dirk Saller

Germany

Karl-Georg Schlesinger

Austria

Martin Schlichenmaier

Luxembourg

Oliver Schlotterer

Germany

Alexander Schmidt

Germany

Urs Schreiber

Germany

Bert Schroer

Brazil

Harold Steinacker

Austria

Frank Steiner

Germany

Michael Stiller

Germany

Thomas Thiemann

Canada

Jürgen Tolksdorf

Germany

Armin Uhlmann

Germany

Adrian Vajiac

USA

Walter van Suijlekom

Netherlands

Rainer Verch

Germany

Hartmut Wachter

Germany

Stefan Waldmann

Germany

Scientific Organizers

Bertfried Fauser

Max-Planck-Institut für Mathematik in den Naturwissenschaften

Jürgen Tolksdorf

Max-Planck-Institut für Mathematik in den Naturwissenschaften

Eberhard Zeidler

Max-Planck-Institut für Mathematik in den Naturwissenschaften

Administrative Contact

Regine Lübke

Max-Planck-Institut für Mathematik in den Naturwissenschaften Contact via Mail