Morning Session: Application Challenges

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Talks

  • Chair: Birgitta Whaley
  • Speakers
    • Synge Todo
      • QMC challenges
        • Criticality with large correction to scaling
        • Supersolid: coexistence of diagonal or off-diagonal order (done on lattice)
        • Deconfined criticality
        • Long-range interacting systems
        • Strongly anisotropic systems
        • Bond-alternating spin chains (need good order parameter)
      • Go beyond memory barrier
      • Can one detect berry phases with QMC?
    • Tomotoshi Nishino
      • Classical lattice models
        • Low temperatures
        • Non-Hermitian problems (TMRG): violation of variational principle
          • Examples of such problems?
            • TM of vertex models are non-symmetric
        • Constraint models: constraints increase number of states kept
    • Didier Poilblanc
      • Generalized QDM for frustrated magnets
      • Only for Abelian particles
      • How does this expansion compare to CORE?
        • CORE is not exact
        • CORE breaks translational symmetry
      • How does one parallelize ED on distributed memory?
        •  ??? -> Andreas Laeuchli
    • Anatoly Kuklov
      • Free-space supersolidity
      • Ideal supersolid or relation to defects?
      • Shear-module
      • How to make people take ab-initio simulations be taken seriously?
      • Quantum mechanics of superfluid living on dynamical extended defects network: quantum metallurgy
      • Role of He3 in superfluid and mechanical properties of solid He4
      • Flow problems?
    • Valentin Murg
    • Guifre Vidal
      • Understand entanglement scaling
    • Bela Bauer
    • Adrien Feiguin
      • I/O constraints
      • Use of symmetries
      • DMRG in momentum space
    • Matthias Troyer
      • Band gap problem of silicon
        • Gap is completely wrong in LDA
        • GW approximation
      • What takes a cluster for the Hubbard model may take petaflop for material
    • Ian McCulloch
      • 1d challenges: parallelization
      • Current limitation: 10000 states (with good symmetries)
      • One million: maybe easier without quantum numbers
      • Most pure 1d problems are understood, except time evolution
      • Master equation evolution? Dissipation?
      • t-J on wide ladder - revisit with petascale?
        • Non-striped states out there?
        • Enforce stripelessness with translational invariance
        • Stripe in correlations
      • Update tensor sequentially? Independently?
      • DMRG to QFT?
        • QED in 2+1?
        • String is 1d object
      • Quantum Chemistry
        • Symmetry aspects: total spin excitations
      • Nanotubes
      • Nuclear shell models
        • Big local dimension
        • Complicated Hamiltonian

Discussion

  • Which methods can scale to petaflop machines?
    • DMFT can (with disorder)
    • Loop algorithm can
    • DiagMC could
    • Worm for helium: much harder
    • Lanczos can
      • For QDM etc.: keep matrix in memory
    • DMRG: similar to Lanczos, more sceptical
      • Latency problems
      • I/O problems
      • Forget storing matrices on disk (2 GB/core)
      • Shared memory is easier: now about 64 cores, will not get beyond that
      • Heisenberg spin chain on a terascale machine?