We examine the quantum theory of the spontaneous breaking of lattice rotation symmetry in dwave superconductors on the square lattice. This is described by a field theory of an Ising nematic order parameter coupled to the gapless fermionic quasiparticles. We determine the structure of the renormalization group to all orders in a 1/N f expansion, where N f is the number of fermion spin components. Asymptotically exact results are obtained for the quantum critical theory in which, as in the large N f theory, the nematic order has a large anomalous dimension, and the fermion spectral functions are highly anisotropic.

The consumption of a food typically leads to a decrease in its subsequent intake through habituation--a decrease in one's responsiveness to the food and motivation to obtain it. We demonstrated that habituation to a food item can occur even when its consumption is merely imagined. Five experiments showed that people who repeatedly imagined eating a food (such as cheese) many times subsequently consumed less of the imagined food than did people who repeatedly imagined eating that food fewer times, imagined eating a different food (such as candy), or did not imagine eating a food. They did so because they desired to eat it less, not because they considered it less palatable. These results suggest that mental representation alone can engender habituation to a stimulus.

Recently there have been several proposals of materials predicted to be nodal ring semi-metals, where zero energy excitations are characterized by a nodal ring in the momentum space. This class of materials falls between the Dirac-like semi-metals and the more conventional Fermi-surface systems. As a step towards understanding this unconventional system, we explore the effects of the long-range Coulomb interaction. Due to the vanishing density of states at the Fermi level, Coulomb interaction is only partially screened and remains long-ranged. Through renormalization group and large-N f computations, we have identified a non-trivial interacting fixed point. The screened Coulomb interaction at the interacting fixed point is an irrelevant perturbation, allowing controlled perturbative evaluations of physical properties of quasiparticles. We discuss unique experimental consequences of such quasiparticles: acoustic wave propagation, anisotropic DC conductivity, and renormalized phonon dispersion as well as energy dependence of quasiparticle lifetime.

We present a projective symmetry group (PSG) analysis of the spinless excitations of Z 2 spin liquids on the kagome lattice. In the simplest case, vortices carrying Z 2 magnetic flux ('visons') are shown to transform under the 48 element group GL(2, Z 3 ). Alternative exchange couplings can also lead to a second case with visons transforming under 288 element group GL(2, Z 3 ) × D 3 . We study the quantum phase transition in which visons condense into confining states with valence bond solid order. The critical field theories and confining states are classified using the vison PSGs.

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