On short interval expansion of Rényi entropy

Andrzej Białas, Wieslaw Czyz

Bin Chen, Jun-Bao Wu, Jia-ju Zhang

We investigate the short interval expansion of the Rényi entropy for two-dimensional conformal field theory (CFT) on a torus. We require the length of the interval ℓ to be small with respect to the spatial and temporal sizes of the torus. The operator product expansion of the twist operators allows us to compute the short interval expansion of the Rényi entropy at any temperature. In particular, we pay special attention to the large c CFTs dual to the AdS3 gravity and its cousins. At both low and high temperature limits, we read the Rényi entropies to order ℓ6, and find good agreements with holographic results. Moreover, the expansion allows us to read 1/c contribution, which is hard to get by expanding the thermal density matrix. We generalize the study to the case with the chemical potential as well.

Christian Cachin

Iwo Białynicki‐Birula

Diptarka Das, Shouvik Datta, Sridip Pal

The Monster CFT plays an important role in moonshine and is also conjectured to be the holographic dual to pure gravity in AdS3. We investigate the entanglement and Rényi entropies of this theory along with other extremal CFTs. The Rényi entropies of a single interval on the torus are evaluated using the short interval expansion. Each order in the expansion contains closed form expressions in the modular parameter. The leading terms in the q-series are shown to precisely agree with the universal corrections to Rényi entropies at low temperatures. Furthermore, these results are shown to match with bulk computations of Rényi entropy using the one-loop partition function on handlebodies. We also explore some features of Rényi entropies of two intervals on the plane.

Yun Cheng, Yuan Li