TTbar Group Meeting

Welcome to the $T\overline{T}$ Group website!

The TTbar refers to a large class of deformations of QFTs that were initially studied by Zamolodchikov and Smirnov, Dubovsky et al, and Cavaglia et al for two dimensions, but has in last few years been generalised in various exciting directions. These directions include interesting relations with holography, de Sitter spacetimes and string theory. In our $T\overline{T}$ group meetings we discuss the recent literature, update each other on their research and discuss new ideas, but most of all we just like to deform things. Our meetings are on Wednesdays at 1:30pm.

On this page you will find the schedule for the coming weeks and an archive of past meetings. We also keep a list of topics here:

Topics

1. $T\overline{T}$ and de Sitter: Single / double trace version.
2. Inclusion of matter fields in the bulk, O2 deformations
3. $T\overline{T}$ in AdS2 and quantum mechanics
4. Tensor network interpretation of $T\overline{T}$

### (11-11-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/94529875610?pwd=V0FwSWMwemgzQ1lYWHU4UmpSQWU4Zz09

In this meeting, we will have an informal discussion about using TTbar in cosmological settings. Jorrit will briefly review the results in https://arxiv.org/abs/2006.03054. After that we will discuss some questions/puzzles.

### (28-10-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/94529875610?pwd=V0FwSWMwemgzQ1lYWHU4UmpSQWU4Zz09

In this meeting, we will have an informal discussion about using TTbar in cosmological settings. Eva will discuss some observations on real vs thought-experimental observations and Victor will discuss the implementation of TTbar in de Sitter. After that we will discuss some questions/puzzles.

### (14-10-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/94529875610?pwd=V0FwSWMwemgzQ1lYWHU4UmpSQWU4Zz09

In this meeting, Gábor Sárosi will present his work with Aitor Lewkowycz and Alex Belin, https://arxiv.org/abs/2006.01835

### (16-09-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/94529875610?pwd=V0FwSWMwemgzQ1lYWHU4UmpSQWU4Zz09

In this meeting, Vasu Shyam will present ongoing work with Evan Coleman to implement conformal boundary conditions in AdS3 through TTbar.

### (26-08-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/94529875610?pwd=V0FwSWMwemgzQ1lYWHU4UmpSQWU4Zz09

In this meeting, we will have Ronak Soni talking about https://arxiv.org/abs/2008.02810.

### (12-08-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/8200160864?pwd=UUNObytDR3U4YWdwYTJ1TjJCM1pTQT09

In this meeting, we will have Daniel Brennan from Chicago U. talking about https://arxiv.org/abs/2005.00431.

### (08-07-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/8200160864?pwd=UUNObytDR3U4YWdwYTJ1TjJCM1pTQT09

In this meeting, we will have Jorrit Kruthoff talking about https://arxiv.org/abs/2006.03054.

### (24-06-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/8200160864

In this meeting, we will have Jonah Kudler-Flam from Chicago U. talking about https://arxiv.org/abs/2005.08972.

See the link to the talk on the recordings page.

### Strike for Black Lives (10-06-2020)

This meeting will be replaced by department-wide sessions on Black Lives, discussing racial injustice and brainstorming how we can work against it.

### (27-05-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/8200160864

In this meeting, Evan gave an update on the single trace TTbar program.

Note: Some attendees have requested a move to an every-other-week schedule. The meeting on the 20th has been deferred to the 27th.

### (13-05-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/8200160864

In this meeting, John Cardy gave a talk on the non-relativistic limit of TTbar as an insight into its interpretation as a state-dependent diffeomorphism.

### (29-04-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/8200160864

In this meeting, Gonzalo will discuss Lambda_2 and the kernel.

(In a later meeting Evan will discuss the status of singularity resolution and the addition of a Lambda2-type deformation in the single-trace TTbar program.)

### (22-04-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/8200160864

In this meeting Sungyeon discussed form factor approaches to the computation of entropy in TTbar deformed field theories.

### (15-04-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/8200160864

In this meeting we will continue discussing various approaches to the computation of entropy in TTbar deformed field theories. Refs: https://arxiv.org/abs/0706.3384
, https://dynalist.io/d/z9hWPDS9Ux5CQz9NIhSDILk2

### (08-04-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/8200160864

In this meeting we will discuss various approaches to the computation of entropy in TTbar deformed field theories. Refs: https://dynalist.io/d/i0O-YmcybkH7GtEW6ZvCyIly

### (25-03-2020)

We have gone virtual through Zoom via the link: https://stanford.zoom.us/j/764874146

In this meeting Louise will discuss "Large N analysis of TTbar-deformation and unavoidable negative-norm states” by Haruna, Ishii, Kawai,Sakai and Yoshida,

ArXiv:2002.01414

### (04-03-2020)

In this meeting, Jorrit will discuss exact wavefunctionals in dilaton gravities and their relation to dilaton gravities at finite-cutoff. Refs: https://arxiv.org/abs/gr-qc/9309018 https://journals-aps-org.stanford.idm.oclc.org/prl/abstract/10.1103/PhysRevLett.54.959

### (12-02-2020)

In this meeting, Louise will discuss the following paper on the large N analysis of TTbar deformation: https://arxiv.org/abs/2002.01414.

### (05-02-2020)

Onkar discussed ongoing work on the flow of eigenstates in TTbar deformation. Then, Sungyeon discussed the following paper on the relationship between TsT transformations and TTbar deformations: https://arxiv.org/pdf/1911.12359.pdf

### (29-01-2020)

This meeting was a catch-up meeting for progress during the break.

### (22-01-2020)

Edward told us about the curved space kernel. Ref: https://arxiv.org/pdf/1912.09179.pdf

No meetings

### (20-11-2019)

Zhenbin will continue with entanglement islands, this time in bulk dS and explain some non-perturbative calculations of Renyi entropy in dS2 gravity. Then we will collectively discuss the
dual formulation using T Tbar +… deformations. In particular, we can formulate the 2d version of the bulk de Sitter theory, obtained by going all the way in with T Tbar and then out with T Tbar + Lambda_1 deformation of the seed theory. The seed could be the SYK dual of a (n)AdS theory and black holes therein. This deformation leads to bulk dS (or some (n)dS involving a varying scalar), at the level of the energy levels. One aspect is the role of the disorder average: we'll explore the possibility of formulating it by refraining from disorder averaging until we join the two sectors of dS2/dS1, then integrating over the common couplings of the joined system which we must do anyway in our fluctuating cosmological theory, and checking if that single integration can play the role of the disorder average in terms of giving a tractable large N expansion.

### (13-11-2019)

Zhenbin Yang will describe entanglement islands and we will discuss how this might arise our various T Tbar deformed theories. Refs: https://arxiv.org/abs/1905.08255; https://arxiv.org/abs/1905.08762; https://arxiv.org/abs/1910.11077; https://arxiv.org/abs/1903.11115; https://arxiv.org/abs/1908.10996; https://arxiv.org/abs/1707.02325; https://arxiv.org/abs/1904.01911.

### (06-11-2019)

We discussed the paper "TTbar deformed CFT as a non-critical string" by Nele Callebaut, Jorrit Kruthoff and Herman Verlinde.

### (30-10-2019)

We will continue the discussion on operators in TTbar deformed theories from last week. In time permits, we will discuss applications of similar techniques in the context of entanglement calculations.

### (23-10-2019)

In this meeting, Sungyeon Yang will discuss dressed correlation functions in TT-deformed theories. After going through some results obtained from perturbation theory, a nonperturbative approach presented in Cardy's recent work will be introduced. Application of the method to correlators of the stress-energy tensor will be discussed afterwards. Ref: TTbar deformations of correlation functions

### (16-10-2019)

Jorrit Kruthoff presented some recent progress in understanding the analogue of the TTbar deformation in 1d and its generalisations. In particular, he discussed the connection to JT gravity at finite cutoff, boundary conditions in AdS_2 and the SYK model.

Ref: TTbar in AdS_2 and Quantum Mechanics and work in progress.

### (09-10-2019)

Evan told us about the single trace version of the TTbar deformation put forward by Kutasov et al.

### (02-10-2019)

Eva Silverstein described a new paper with Aitor Lewkowycz, Junyu Liu (a.k.a. "L"), and Gonzalo Torroba on subregion dualities and entropy. The entropy calculations localize at the endpoints, enabling precise calculations on both sides of the duality which match. In appropriate cases like (A)dS/dS and AdS/Poincare, causal evolution holds and a new commutator structure of the algebras associated to subregions was described. Redundant encoding of bulk points (QEC) persists in TTbar+… deformed theories. Ref: TTbar and EE, with implications for subregion encodings.

Ronak Soni gave an update on The Kernel in progress with Edward Mazenc and Vasu Shyam.

page revision: 103, last edited: 10 Nov 2020 21:40