KSBA compactification of the moduli space of K3 surfaces with purely non-symplectic automorphism of order four

We describe a compactification by KSBA stable pairs of the five-dimensional moduli space of K3 surfaces with purely non-symplectic automorphism of order four and $U(2)\oplus D_4^{\oplus2}$ lattice polarization. These K3 surfaces can be realized as the minimal resolution of the double cover of $\mathbb{P}^1\times\mathbb{P}^1$ branched along a specific $(4,4)$ curve. We show that, up to a finite group action, this stable pairs compactification is isomorphic to Kirwan's partial desingularization of the GIT quotient $(\mathbb{P}^1)^8//\mathrm{SL}_2$ with the symmetric linearization.Comment: 26 pages, 6 figures. We explain the connection with Alexeev-Thompson work on ADE surfaces. Comments are welcom

Bulk Viscosity in Holographic Lifshitz Hydrodynamics

We compute the bulk viscosity in holographic models dual to theories with Lifshitz scaling and/or hyperscaling violation, using a generalization of the bulk viscosity formula derived in arXiv:1103.1657 from the null focusing equation. We find that only a class of models with massive vector fields are truly Lifshitz scale invariant, and have a vanishing bulk viscosity. For other holographic models with scalars and/or massless vector fields we find a universal formula in terms of the dynamical exponent and the hyperscaling violation exponent.Comment: 24 page

Odd Parity Transport In Non-Abelian Superfluids From Symmetry Locking

We consider relativistic non-Abelian superfluids, where the expectation value of the global symmetry currents relate space and internal indices, thus creating a "locked" phase. Locking a superfluid with SU(2) internal symmetry in 2+1 dimensions breaks parity spontaneously, and introduces parity-odd terms in the constitutive relations. We show that there are qualitatively different extensions of the rest frame locking to non-zero velocities. We construct the resulting superfluid hydrodynamics up to the first derivative order. Using an expansion close to the critical point, we estimate the ratio of the Hall viscosity and the angular momentum density. Our general hydrodynamic results are compatible with the holographic p-wave calculations in arXiv:1311.4882.Comment: 44 pages, updated references, new appendix with discussion about entropy current, conclusions unchanged. Published versio