Máté Lencsés
(Wigner Research Centre for Physics, Budapest)

In this seminar, I will present our recent results on the multicritical generalization of the Yang-Lee edge singularity and non-unitary renormalization group flows. As an example, I will show that by perturbing the tricritical Ising model with imaginary magnetic fields one can find a critical Yang-Lee line in the space of couplings. As in the unitary case, the critical line ends at the tricritical point, that we call tricritical Yang-Lee model. The critical line separates between PT symmetric and broken phases, while going around the tricritical point without crossing it, the PT symmetry gets broken non-critically, i.e. without the closure of the gap. Analogously to the unitary multicritical series, we propose massless flows between nonunitary multicritical points and a natural Ginzburg-Landau description.