Transcript Some open questions from this conference/workshop

Some open questions from this
conference/workshop
Q 1 (Balents)
Are quantum effects important for physics of hexagonal
manganites (Eg: YMnO3)?
What is the mechanism of coupling between electric
polarization and spin order?
Q2 (Senthil)
Theory of field-induced transition from heavy fermi liquid
to fermi liquid with polarized local moments?
Application to CeRu2Si2 or URu2Si2?
Is there significant Fermi surface reconstruction at the
metamagnetic transition in these materials?
Q3 (Vishwanath, Balents)
• In amorphous films undergoing a field-tuned
``superconductor-insulator” transition, to what extent can
the vortices be regarded as quantum particles?
Q4 (Je-Geun Park)
• Experiments on a number of heavy fermion critical points
(Fermi liquid to AF metal/spin glass) see non-trivial
exponents for dynamical spin correlations.
Thus far these exponents cluster around 2 values (2/3 and
1/3). Is there any systematics to these exponent values?
Is there any theory?
Q5 (Oshikawa, Fisher, Senthil)
Can non-trivial two dimensional quantum paramagnets be
accessed by weakly coupling together spin-1/2 chains?
Q6 (Y.B. Kim, Senthil)
Can the Oshikawa/Hastings arguments on structure of
paramagnetic states of easy plane/axis magnets be
generalized to SU(2) invariant systems?
(Eg S = 1 on 2d square lattice believed not to have trivial
paramagnetic ground state with SU(2) symmetry: can
this be understood at the same level as generality as
Oshikawa/Hastings?)
Q7 (Senthil)
• Are there any clear demonstrable instances of criticality
in quantum systems where spatial correlations are
mean-field like but time correlations are anamolous?
(analogous to proposal of Si et al for heavy fermion critical
points)
Q8 (Q. Si)
• Is there a microscopic model which can be demonstrated
to have a deconfined Landau-forbidden deconfined
quantum critical point?
Spin systems, bosons on various lattices?
Q9 (Balents, Y.B. Kim, Senthil)
• Can one understand the theoretical problem of Fermi
surface coupled to a gauge field in some controlled
approximation?
(Do better than work from 1990’s)
Fate of monopoles? 2kf correlations? Luttinger theorem?
Q10 (Y.B. Kim, Oshikawa, Fisher, Senthil)
• Does the sigma model formulation for 2d deconfined
quantum critical points have any power for
analytic/numerical calculations?
• Is there a `sigma model’ description of stable two
dimensional algebraic spin liquids in terms of a bosonic
field theory perhaps with topological terms?
Q11 (Kwon Park)
Is there a `solution’ to the sign problem in simulating
Hamiltonians of quantum many particle systems?
How well-defined is the sign problem?
Are there classes of problems that have an `intrinsic’ sign
problem that will not disappear in any useful
reformulation?
Will such systems have properties different from those
without an `intrinsic’ sign problem?
Q12 (Si, Senthil)
• How do we describe the single impurity Kondo effect in a
bosonic decription of the impurity spin?
Q13 (Vishwanath, Si, Senthil)
• Is there really `reduced’ dimensionality for spin
fluctuations at heavy fermion critical points that show
non-fermi liquid behavior?
• Does the reduced dimensionality play any direct role in
giving the non-Fermi liquid physics?
Q14 (Senthil)
• Is gauge theory useful (necessary?) for understanding
high-Tc cuprates?
Is there a viable alternate to implement Mott/valence bond
physics in doped Mott insulators?
Q15 (Balents)
• Is there a quasi-realistic spin/Hubbard model that can be
shown to be in a spin liquid phase?
Q16 (Vishwanath, Fisher, Senthil)
• How correct is it to integrate out fermions in a HertzMillis theory of a metallic quantum phase transition?
(Action in ordered and disordered phases is different; is this
a problem?)
Q17 (Si)
• Is there interesting physics at a quantum first order
transition in a metallic system?
Q18 (Balents, Fisher, Y.B. Kim, Senthil)
Cs2CuCl4
1. Where in q-space are there ``gapless” excitations
associated with power law tails in inelastic neutron
scattering?
2. To what extent is the scattering in these tails polarized in
easy plane?
3. What is the theoretically expected answer for 1d-2d
crossover?
Q19 (Furusaki)
• What is the phase diagram of the 2d Hubbard model at
half-filling on a frustrated lattice?
Eg: Triangular or Kagome lattices
Q20 (Senthil)
• Do there exist non-Fermi liquid states of matter with
Fermi arcs?
• Can we construct an example?