17.11.2021 (Wednesday)

Boundary criticality of the O(N) model in d = 3 critically revisited

Regular Seminar Maxim Metlitski (MIT)

17:00 KCL
room Online

It is known that the classical O(N) model in dimension d > 3 at its bulk critical point admits three boundary universality classes: the ordinary, the extraordinary and the special. The extraordinary fixed point corresponds to the bulk transition occurring in the presence of an ordered boundary, while the special fixed point corresponds to a boundary phase transition between the ordinary and the extra-ordinary classes. While the ordinary fixed point survives in d = 3, it is less clear what happens to the extraordinary and special fixed points when d = 3 and N is greater or equal to 2. I'll show that formally treating N as a continuous parameter, there exists a finite range 2 < N < N_c where the extra-ordinary universality class survives, albeit in a modified form: the long-range boundary order is lost, instead, the order parameter correlation function decays as a power of log r. I'll discuss recent Monte-Carlo simulations and numerical bootstrap results that confirm the above picture and indicate that the critical value N_c > 3. Based on arXiv:2009.05119, 2111.03613, 2111.03071