Using the Kubo formula approach, we study the effect of electron interaction on thermal transport in the vicinity of a metal-insulator transition, with a granular metal as our model. For small values of dimensionless intergrain tunneling conductance, $gll1,$ we find that the thermal conductivity surprisingly shows a phonon-like algebraic decrease, $kappa(T)sim g^{2}T^{3}/E_{c}^{2}$ even though the electrical conductivity obeys an Arrhenius law, $sigma(T)sim ge^{-E_{c}/T};$ therefore the Wiedemann-Franz (WF) law is seriously violated. This violation arises from non-magnetic bosonic excitations of low energy that transport heat but not charge. Implications for experiment are discussed

In this talk we will look at properties of gluonic flux tubes which are believed to be responsible for confining quarks in QCD, through simulations in lattice gauge theory. We will try to identify the length scale and type of string theory which describes the observed flux tube properties best.