Abstract
We consider unitary CFTs with continuous global symmetries in d > 2. We consider a state created by the lightest operator of large charge Q ≫ 1 and analyze the correlator of two light charged operators in this state. We assume that the correlator admits a well-defined large Q expansion and, relatedly, that the macroscopic (thermodynamic) limit of the correlator exists. We find that the crossing equations admit a consistent truncation, where only a finite number N of Regge trajectories contribute to the correlator at leading nontrivial order. We classify all such truncated solutions to the crossing. For one Regge trajectory N = 1, the solution is unique and given by the effective field theory of a Goldstone mode. For two or more Regge trajectories N ≥ 2, the solutions are encoded in roots of a certain degree N polynomial. Some of the solutions admit a simple weakly coupled EFT description, whereas others do not. In the weakly coupled case, each Regge trajectory corresponds to a field in the effective Lagrangian.
Highlights
In this paper we consider CFTs in d > 2 with continuous global symmetries
We find that the crossing equations admit a consistent truncation, where only a finite number N of Regge trajectories contribute to the correlator at leading nontrivial order
We studied the four-point function of charged operators (3.1). It describes a correlation function of two light charged operators O−qOq in a nontrivial state created by a heavy operator with large charge Q 1 and scaling dimension ∆(Q) 1
Summary
In this paper we consider CFTs in d > 2 with continuous global symmetries. The spectrum of these CFTs contains operators charged under these symmetries. The essential simplification of the large Q limit is that in a certain domain in the space of cross ratios, the dominant contributions to the four-point function in the heavylight fusion channels come from a set of operators whose dimensions above that of the lightest large charge operator are of order 1 in the Q scaling These are the operators that are characterized by the effective field theory. This is a combined limit in which the scaling dimension of the external operator is taken to infinity as we tune cross ratios appropriately The existence of such limits, which result in flat space correlators in a nontrivial background, seems to be a generic feature of any CFT.
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