Triangle Seminars

Abstract:
We will review the beginning of experimental and theoretical studies of moire systems and their evolution up to present. This type of systems represent a new way of “growing” materials, and has tremendous potential both for fundamental physics as well as for applications. Two dimensional periodic crystals, whose separation between atoms is of order angstroms, can be twisted controllably with respect to each other such that they form new “periodicities”, called moire periodicities. In the new “unit cell” we find thousands of atoms of the original crystal. These atoms behave in ways that are incredibly counterintuitive. We show how the controlled twisting of graphene and MoTe2 layers has led to a slew of states of matter not possible in bulk conventional materials. We will show how the collective behavior of thousands of p orbitals in a moire unit cell of graphene can create single Heavy fermion at moire scale, and how the interaction between such fermions can lead to a perfect quantum simulator of an Anderson model. We will then present a catalogue of possible twistable materials and show how a huge variety of strongly interacting models can be realized in twisted homo and hetero twisted bilayers and multilayers of these materials.

Abstract:
Yang-Mills theory in AdS_4 with Dirichlet boundary conditions is expected to undergo a transition as the AdS radius varies, since the boundary data is incompatible with confinement in flat space. We apply the conformal bootstrap to four-point functions of non-Abelian conserved currents in 3d to place bounds on proposed mechanisms for the transition. We rule out the scenario in which the boundary current decouples by bounding the current central charge. We obtain bounds on the dimension of the lightest scalar operators, which disfavour a bulk-Higgs mechanism and instead support a transition triggered by a scalar singlet becoming marginal. Based on 2512.00150.

Abstract:
Recently, non-Lorentzian, i. e., nonrelativistic (Galilean) and ultrarelativistic (Carrollian), limits have attracted attention as decoupling limits of string and M-theory. In this talk, we argue that Galilean and Carrollian limits are, against common belief, closely related, and can be dealt with in a unifying manner. This allows one to show that properties of Galilean symmetries can be extended to Carrollian symmetries, as we will illustrate by focusing on particle toy models. In particular, we will show that there exist Carrollian counterparts of the facts that the Galilei algebra can be centrally extended to the Bargmann algebra, and that there exists a corresponding particle action. We will interpret our results in the context of decoupling limits of string theory and its timelike T-duals à la Hull.