# fizinfo AT lists.kfki.hu

**Subject:** ELFT HÍRADÓ

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**From**: Sandor Katz <katz AT bodri.elte.hu>**To**: fizinfo AT lists.kfki.hu**Subject**: [Fizinfo] ELTE particle physics seminar - Apr 12 - Unusual Location**Date**: Tue, 9 Apr 2019 12:21:27 +0200 (CEST)

Kedves érdeklődők!

E héten a szokásostól eltérő helyen és időben lesz az elméleti fizika szeminárium.

Üdvözlettel,

Katz Sándor

Date/Time: 12 April, Friday, 14:15

Location: ELTE, TTK, Lagymanyos, 7. floor, room 7.14

Speaker: Slava Rychkov (IHES, Ecole Normale Superieure Paris)

Title: Walking, weakly first-order phase transitions, and complex CFTs

Abstract:

Most people have heard that the 2d Potts model with Q=5 states has a first order phase transition, but not everyone knows that the correlation length at this phase transition is 2500 lattice spacings. We will review "walking RG" behavior in gauge theories and connect it to Type II weak first-order phase transitions in statistical physics. Despite appearing in very different systems (QCD below the conformal window, the Potts model, deconfined criticality) these two phenomena both imply approximate scale invariance in a range of energies and have the same RG interpretation: a flow passing between pairs of fixed point at complex coupling, dubbed "complex CFTs". Observables of the real walking theory are approximately computable by perturbing the complex CFTs. The general mechanism will be illustrated by a specific and computable example: the two-dimensional Q-state Potts model with Q > 4. Based on 1807.11512 and 1808.04380.

**[Fizinfo] ELTE particle physics seminar - Apr 12 - Unusual Location**,*Sandor Katz, 04/09/2019*

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