This space for questions, ideas and workshop topics

Program Overview

Setting the tone and asking the big questions.

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1. Universal terms in the entanglement entropy

  • "Short and long range" or "local and non-local" entanglement
  • What assumptions underlie these classifications? Violation of assumptions in Haah's cubic code?
  • Origin of universal terms in even vs. odd dimensions (CFTs)
  • Derivation of a-theorem in 3+1-D using strong subadditivity? Derivation of F-theorem in 2+1-D using QFT? higher dimensional analogues?
  • Gapless strongly interacting phases: analytical calculation of EE for spinon Fermi surface in two or three dimensions?
  • Universal topological data from ground state wavefunction for SPT (symmetry protected topological) phases? For 3+1-d topological phases with non trivial three loop braiding?

2. Decoding the wavefunction to obtain information not naively contained in the wavefunction

  • Entanglement Hamiltonian for the ground state of Lorentz invariant systems encode the original Hamiltonian.
  • Are there non-trivial examples without Lorentz invariance where we can deduce the Hamiltonian from the ground state wavefunction?
  • Eigenstate Thermalization (Ergodic systems) => Entanglement Hamiltonian for finite energy density states =~ the original Hamiltonian.

3. Quantum dynamics and entanglement

  • Origin of the linear in time entanglement growth after a global quench?
  • Ergodic vs. non-ergodic behavior (logarithmic in time growth in many body localization).
  • Equivalence between thermal and entanglement entropies at finite energy density in ergodic phases.
  • Signatures of quantum chaos? Relation to Lieb-Robinson bounds?

4. Calculational tools

  • "EE not a well defined quantity in QFT" (anonymous). How to make progress with analytical continuation related issues for Renyi Entropies e.g. two interval entropy in 1+1-D CFTs?
  • prospects and target systems where current methods can be applied?
  • novel techniques and algorithmic development.
  • relationship between the sign problem in quantum Monte Carlo and measuring entanglement entropy?
  • Can the von Neumann entanglement entropy be measured in Monte Carlo?

5. Measuring entanglement

  • Cancel your flights, do not miss next Tuesday's experimental talk by Rajibul Islam on measuring the 2nd Reyni entropy in ultra cold atoms.
  • Basic issue with von Neumann EE: it's a "state-dependent" operator. Can one measure state dependent operators of any kind in a experiment (modulo Renyi entropies which become state independent after taking n copies of the system)?

6. Holographic entanglement

  • First week focus with an introductory talk by Mukund Rangamani on Thursday at 11:00 AM.


Questions from the Discussion on c, a, and F-theorems

Led by John Cardy, Friday, April 4, 2015

1) What is the c-theorem in 2d? What are the different proofs?
2) What are its applications to condensed matter/QFT?
3) Which of these arguments extend to other even/odd d? (Can we make a table?)
4) What is the status of the a-theorem in d=4?
5) What are its potential applications?
6) What is the status of the F-theorem in 3d?
7) What are its potential applications?
8) Is there a higher-dimensional version of the boundary g-theorem?
9) Why does it seem so hard to prove monotonicity theorems given the universal nature of the RG?



Questions from the Discussion "What is a Phase"

Led by Frank Verstraete and David Perez-Garcia
  • Given two phases which have the same qualitative properties (e.g. exactly the same set of quasiparticles), can they be separated by a continuous phase transition?