Research in the QFT group

Quantum field theory (QFT) is the basic physical theory that combines quantum theory with special relativity in order to describe elementary particles. Besides its phenomenological success, QFT still contains many open mathematical problems, and continues to be a driving force for many developments in mathematics.

In our group, we mostly focus on an approach to QFT that is called algebraic QFT (AQFT) or local quantum physics, emphasizing the central role of Einstein locality (causality) in this theory. The mathematical description of a quantum field theory in this framework consists of a net of observable algebras (either C*-algebras in a representation-independent version, or von Neumann algebras for specific representations, for example vacuum representations) that is indexed by the open regions of spacetime and subject to a number of physically motivated axioms, expressing in particular the covariance and locality of the theory.

Some themes of current research with links to articles are:

  • Standard subspaces and associated subfactors (see extended abstracts [CL23, CL25] and [CL25])
  • Relative entropies and other f-divergences on von Neumann algebras [CFLS26]
  • Construction of interacting quantum field theories from so-called Borchers triples with the help of Tomita-Takesaki theory  (see review [L15])
  • Twisted Araki-Woods von Neumann algebras ([CL22])
  • Scattering theory in QFT, in particular in integrable models ([AL17],[BCL21])
  • Structure theory of Borchers triples and non-local examples of QFTs ([LS22])
  • Braided structures in QFT and solutions of the Yang-Baxter equation (unitary braidings) ([LPW19],[CL21])

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Completed projects (selection)

  • Algebraic Quantum Field Theory in the UK
    LMS Research Groups grant (Chris Fewster (York), Robin Hillier (Lancaster), Gandalf Lechner)
  • Operator Algebras and Quantum Physics
    May-June 2019, program at the Simons Center for Geometry and Physics, Stony Brook (Stefan Hollands (Leipzig), Vaughan Jones (Vanderbilt), Gandalf Lechner, Roberto Longo (Rome))
  • Deformations of Quantum Field Theories
    FWF Grant P22929-N16, 2011-14, (Gandalf Lechner, Jakob Yngvason (Vienna))