Comments on Holographic Entanglement Entropy in TT Deformed CFTs
Chitraang Murdia, Yasunori Nomura, Pratik Rath, Nico Salzetta
TL;DR
The paper demonstrates that the RT formula remains valid for TT-deformed CFTs whenever the holographic duality is encoded by a GKPW-like dictionary, including cases with a finite bulk cutoff. By combining a field-theoretic replica-trick calculation of entanglement entropy for TT deformations with a bulk LM-based holographic analysis, it shows that the bare entanglement entropy satisfies RT, while holographic counterterms contribute only as localized surface terms to the renormalized entropy. A concrete cutoff-AdS calculation reproduces the same entanglement result, establishing a consistent bridge between the field theory regulator provided by the TT deformation and the bulk cutoff. The work strengthens the view that entanglement-geometry dualities extend beyond AdS/CFT to general spacetimes and informs holography in flat space and cosmological contexts through the TT framework.
Abstract
The Ryu-Takayanagi (RT) formula has been a key ingredient in our understanding of holography. Recent work on TT deformations has also boosted our understanding of holography away from the conformal boundary of AdS. In this short note, we aim to refine some recent work demonstrating the success of the RT formula in TT deformed theories. We emphasize general arguments that justify the use of the RT formula in general holographic theories that obey a GKPW-like dictionary. In doing so, we clarify subtleties related to holographic counterterms and discuss the implications for holography in general spacetimes.