Seminar on Conformal Field Theory

Date: July 7, 2017

Place:  Department Mathematik, Erlangen


  • Christoph Keller (ETH Zürich)
  • Gregor Schaumann (Universität Wien)
  • Olaf Schnürer (Universität Bonn)


Opens external link in new windowPeter FiebigOpens external link in new windowNils Scheithauer, Opens external link in new windowKatrin Wendland



  • 14:00 - 15:00: Topological Orbifolds (Gregor Schaumann, Universität Wien)
  • 15:15 - 16:15: VOAs with sparse light spectrum (Christoph Keller, ETH Zürich)
  • 16:15 - 17:00 : Coffee break
  • 17:00 - 18:00 : Geometric applications of conservative descent for semi-orthogonal decompositions (Olaf Schnürer, Universität Bonn)


  • VOAs with sparse light spectrum (Christoph Keller)

    • Physicists are interested in (holomorphic) Vertex Operator Algebras with a sparse light spectrum, that is theories where the dimension of V_h is small for small h. I will discuss some types of constructions of such theories, namely permutation orbifolds and lattice theories. I will also discuss the notion of extremal VOAs and the motivation from physics for searching for such theories.

  • Topological Orbifolds (Gregor Schaumann)

    • We present a systematic approach to orbifolds in n-dimensional topological field theory (TFT) developed in joint work with Ingo Runkel and Nils Carqueville. The orbifold procedure is a way to use certain defects in a quantum field theory, that are regarded as a symmetry of the QFT, to produce a new QFT, regarded as fixed point theory.

      In this talk we mainly focus on topological defects in TFTs, but the method generalizes to other types of functorial field theories. The structure of the relevant orbifold defects is modelled on the Pachner moves in n-dimensions. We consider examples of orbifolds in 2d and 3d TFTs and we maybe find time to discuss a dynamical approach to orbifold data using ideas from renormalization.

  • Geometric applications of conservative descent for semi-orthogonal decompositions (Olaf Schnürer)

    • Motivated by the local flavor of several well-known semi-orthogonal decompositions in algebraic geometry we introduce a technique called "conservative descent” in order to establish such decompositions locally. The decompositions we have in mind are those for projective bundles, blow-ups and root constructions. Our technique simplifies the proof of these decompositions and establishes them in greater generality. We also discuss semi-orthogonal decompositions for Brauer-Severi varieties. This is joint work with Daniel Bergh (Copenhagen).



The seminar will take place in room 04.363. Click Opens external link in new windowhere for how to find us.


We reserved a contingent of hotel rooms. If you want to stay overnight please contact Mrs. Helle (Opens window for sending


After the seminar there will be a joint dinner. Please send an email to Mrs. Helle  (Opens window for sending if you wish to attend the dinner.

Further questions:

If you have any questions please contact the organisers or Mrs. Helle (Opens window for sending