Considering the large-$q$ expansion of the Sachdev-Ye-Kitaev (SYK) model in the two-stage limit, we compute the Lanczos coefficients, Krylov complexity, and the higher Krylov cumulants in subleading order, along with the $t/q$ effects. The Krylov complexity naturally describes the"size"of the distribution, while the higher cumulants encode richer information. We further consider the double-scaled limit of SYK$_q$ at infinite temperature, where $q \sim \sqrt{N}$. In such a limit, we find that the scrambling time shrinks to zero, and the Lanczos coefficients diverge. The growth of Krylov complexity appears to be"hyperfast", which is previously conjectured to be associated with scrambling in de Sitter space.

Krylov complexity in large-$q$ and double-scaled SYK model

Timelike entanglement entropy

https://link.springer.com/content/pdf/10.1007/JHEP09(2022)078.pdf

Convexity of charged operators in CFTs with multiple Abelian symmetries

The pseudo entropy is a promising recent generalization of the entanglement entropy to the situations in which both the initial and final state are involved, with the density matrix promoted to the transition matrix. However, in contrast to the non-Hermiticity of the generic transition matrix, the holographic pseudo entropy formulated via the Euclidean AdS/CFT turns out to be always real-valued, which potentially conceals the crucial natures of this novel quantity. In this note, we make the first attempt to formulate a real-time prescription for computations to incorporate naturally the pseudo entropy, as a generally complex-valued entanglement measure, into the AdS/CFT context. It is then conjectured that the holographic pseudo entropy is dual to the extremal codimension-2 area surface in the generally time-dependent Lorentzian asymptotically AdS spacetime, but may also receive imaginary contribution from the regularized extrinsic curvature term of the area surface, which is not included in the covariant holographic entanglement entropy. In this real-time prescription, the holographic pseudo entropy can be considered as a generalization of the covariant holographic entanglement entropy, as well.

Complex-valued Holographic Pseudo Entropy via Real-time AdS/CFT Correspondence

Self-binding energies in AdS

https://link.springer.com/content/pdf/10.1007/JHEP08(2022)051.pdf

Going beyond ER=EPR in the SYK model

We study instability of the lowest dimension operator (i.e., the imaginary part of its operator dimension) in the rank-Q traceless symmetric representation of the O(N) Wilson-Fisher fixed point in D = 4 + . We find a new semi-classical bounce solution, which gives an imaginary part to the operator dimension of order O ( −1/2 exp [ − 3 F ( Q) ]) in the double-scaling limit where Q ≤ N+8 6 √ 3 is fixed. The form of F ( Q), normalised as F (0) = 1, is also computed. This non-perturbative correction continues to give the leading effect even when Q is finite, indicating the instability of operators for any values of Q. We also observe a phase transition at Q = N+8 6 √ 3 associated with the condensation of bounces, similar to the Gross-Witten-Wadia transition. ∗max.washton@gmail.com 1 ar X iv :2 20 3. 08 84 3v 1 [ he pth ] 1 6 M ar 2 02 2

Stability Analysis of a Non-Unitary CFT

A counterexample to the CFT convexity conjecture

We measured the cross section and the proton analyzing power Ay for p– 3He elastic scattering at the angles θ = 26.9◦–170.1◦ in the center of mass system with a 65 MeV polarized proton beam. We compared the data with the rigorous numerical calculations based on the various nucleon–nucleon potentials. For the cross section, clear discrepancy is seen at the angles where the cross section takes minimum. For the proton analyzing power Ay , the calculations have moderate agreements with the data. In this proceedings, we show only the experimental results. Copyright S. Nakai et al. This work is licensed under the Creative Commons Attribution 4.0 International License. Published by the SciPost Foundation. Received 01-11-2019 Accepted 20-01-2020 Published 25-02-2020 Check for updates doi:10.21468/SciPostPhysProc.3.019

/pdf/measurement-for-p-3he-elastic-scattering-with-a-65-mev-2i45y7qbbo.pdf

Masataka Watanabe

Papers

Going beyond ER=EPR in the SYK model

Stability Analysis of a Non-Unitary CFT

A counterexample to the CFT convexity conjecture

Measurement for p–3He elastic scattering with a 65 MeV polarized proton beam

Information metric on the boundary