Recent progress in applying lattice QCD to kaon physics

Standard lattice calculations in kaon physics are based on the evaluation of matrix elements of local operators between two single-hadron states or a single-hadron state and the vacuum. Recent progress in lattice QCD has gone beyond these standard observables. I will review the status and prospects of lattice kaon physics with an emphasis on non-leptonic $K\to\pi\pi$ decay and long-distance processes including $K^0$-$\overline{K^0}$ mixing and rare kaon decays.Comment: 23 pages, 13 figures, 3 tables; Plenary talk given at Lattice 201

Algebraic Conformal Field Theories II

Some mathematical questions relating to Coset Conformal Field Theories (CFT) are considered in the framework of Algebraic Quantum Field Theory as developed previously by us. We consider the issue of fixed point resolution in the diagonal coset of type A, and show how to decompose reducible representations into irreducibles. We show the corresponding coset CFT gives rise to a unitary tensor modular category in the sense of Turaev, and therefore may be used to construct 3-manifold invariants. We also show that Kac-Wakimoto Hypothesis (KWH) and Kac-Wakimoto Conjecture (KWC) are equivalent under general conditions which can be checked in examples, a result which seems to be hard to prove by purely representation considerations. Examples are also presented.Comment: 24 pages, AMSte

Algebraic Coset Conformal field theories

All unitary Rational Conformal Field Theories (RCFT) are conjectured to be related to unitary coset Conformal Field Theories, i.e., gauged Wess-Zumino-Witten (WZW) models with compact gauge groups. In this paper we use subfactor theory and ideas of algebraic quantum field theory to approach coset Conformal Field Theories. Two conjectures are formulated and their consequences are discussed. Some results are presented which prove the conjectures in special cases. In particular, one of the results states that a class of representations of coset $W_N$ ($N\geq 3$) algebras with critical parameters are irreducible, and under the natural compositions (Connes' fusion), they generate a finite dimensional fusion ring whose structure constants are completely determined, thus proving a long-standing conjecture about the representations of these algebras.Comment: 49 pages, Improved presentations and added details, to appear in Comm.Math.Phy

A posteriori error estimation and adaptivity in stochastic Galerkin FEM for parametric elliptic PDEs: beyond the affine case

We consider a linear elliptic partial differential equation (PDE) with a generic uniformly bounded parametric coefficient. The solution to this PDE problem is approximated in the framework of stochastic Galerkin finite element methods. We perform a posteriori error analysis of Galerkin approximations and derive a reliable and efficient estimate for the energy error in these approximations. Practical versions of this error estimate are discussed and tested numerically for a model problem with non-affine parametric representation of the coefficient. Furthermore, we use the error reduction indicators derived from spatial and parametric error estimators to guide an adaptive solution algorithm for the given parametric PDE problem. The performance of the adaptive algorithm is tested numerically for model problems with two different non-affine parametric representations of the coefficient.Comment: 32 pages, 4 figures, 6 table