My research consists of two main directions, both closely related to duality in quantum field theory and string theory.

One is the study of strongly coupled systems by means of gauge/gravity duality. As part of my thesis, I have been studying decay of glueballs in the Witten-Sakai-Sugimoto model, a holographic top-down model based on type IIA string theory. A main result is the calculation of decay patterns favouring the identification of the f_0(1710) resonance as a scalar glueball. My latest article on the subject has dealt with decay and production of pseudoscalar glueballs. Apart from pursuing that line of research, I have also started working on applying gauge/gravity duality to problems of condensed matter physics, in particular topological phases.

My second area of research is the study of mathematical aspects of supersymmetric gauge theories on nontrivial background geometries. In particular, I am interested in the properties of partition functions and (superconformal) indices. I have been studying modular properties of these objects and have recently published an article on the connection between SL(3,Z) transformations and the supersymmetric Casimir energy for theories on Hopf surfaces. I am also actively involved in a project uncovering relations between identities for elliptic hypergeometric functions and dualitities for quiver gauge theories. Furthermore, I am interested in the relationship between theories in various dimensions, including 4d-3d reductions, compactifications of six-dimensional theories and orientifold geometries.

Selection of relevant publications (ordered by date):

  • F. Brünner, D. Regalado and V. P. Spiridonov, “Supersymmetric Casimir Energy and SL(3,Z) Transformations,” arXiv:1611.03831
  • F. Brünner and A. Rebhan, “Holographic QCD predictions for production and decay of pseudoscalar glueballs,” arXiv:1610.10034
  • F. Brünner and V. P. Spiridonov, “A duality web of linear quivers,” Phys.Lett. B761 (2016) 261-264
  • F. Brünner and A. Rebhan, “Constraints on the eta-eta' decay rate of a scalar glueball from gauge/gravity duality,” Phys. Rev. D 92 (2015) no.12, 121902
  • F. Brünner and A. Rebhan, “Nonchiral enhancement of scalar glueball decay in the Witten-Sakai- Sugimoto model,” Phys. Rev. Lett. 115 (2015) no.13, 131601
  • F. Brünner, D. Parganlija and A. Rebhan, “Glueball Decay Rates in the Witten-Sakai-Sugimoto Model,” Phys. Rev. D 91 (2015) no.10, 106002