Anyonic defect branes and conformal blocks in twisted equivariant differential (TED) K-theory

Hisham Sati, Urs Schreiber

Research output: Contribution to journalArticlepeer-review


We demonstrate that twisted equivariant differential K-theory of transverse complex curves accommodates exotic charges of the form expected of codimension =2 defect branes, such as of D7-branes in IIB/F-theory on -type orbifold singularities, but also of their dual 3-brane defects of class-S theories on M5-branes. These branes have been argued, within F-theory and the AGT correspondence, to carry special SL(2)-monodromy charges not seen for other branes, at least partially reflected in conformal blocks of the 2-WZW model over their transverse punctured complex curve. Indeed, it has been argued that all "exotic"branes of string theory are defect branes carrying such U-duality monodromy charges - but none of these had previously been identified in the expected brane charge quantization law given by K-theory. Here we observe that it is the subtle (and previously somewhat neglected) twisting of equivariant K-theory by flat complex line bundles appearing inside orbi-singularities ("inner local systems") that makes the secondary Chern character on a punctured plane inside an -type singularity evaluate to the twisted holomorphic de Rham cohomology which Feigin, Schechtman and Varchenko showed realizes 2k-conformal blocks, here in degree 1 - in fact it gives the direct sum of these over all admissible fractional levels k = -2 + κ/r. The remaining higher-degree 2k-conformal blocks appear similarly if we assume our previously discussed "Hypothesis H"about brane charge quantization in M-theory. Since conformal blocks - and hence these twisted equivariant secondary Chern characters - solve the Knizhnik-Zamolodchikov equation and thus constitute representations of the braid group of motions of defect branes inside their transverse space, this provides a concrete first-principles realization of anyon statistics of - and hence of topological quantum computation on - defect branes in string/M-theory.

Original languageEnglish (US)
Article number2350009
JournalReviews in Mathematical Physics
Issue number6
StatePublished - Jul 1 2023


  • K-theory
  • String theory
  • algebraic topology
  • branes
  • conformal field theory

ASJC Scopus subject areas

  • Statistical and Nonlinear Physics
  • Mathematical Physics


Dive into the research topics of 'Anyonic defect branes and conformal blocks in twisted equivariant differential (TED) K-theory'. Together they form a unique fingerprint.

Cite this