Quantization and Scattering in the IIB SL(2,Z) Covariant Superstring

We rewrite the SL(2,Z) covariant worldsheet action for the IIB string proposed by Townsend in a Polyakov form. In a flat background the formalism yields separate (p,q) sectors. In each one the action is that of the IIB string action with the string slope parameter \alp\pr replaced by its SL(2,Z) analogue \alp_{pq}\pr. SL(2,Z) invariant graviton scattering amplitudes are obtained from those of the fundamental (1,0) string by summing over the different sectors. The tree-level four-graviton amplitude in this formalism differs from a previously conjectured non-perturbative form; both yield the same expansion in order \alpha\pr^3.Comment: 15 pages, LaTeX, additional comment

General covariance of the non-abelian DBI-action

In this paper we study the action for N D0-branes in a curved background. In particular, we focus on the meaning of space-time diffeomorphism invariance. For a single D-brane, diffeomorphism invariance acts in a naive way on the world-volume fields, but for multiple D-branes, the meaning of diffeomorphism invariance is much more obscure. The problem goes beyond the determination of an ordering of the U(N)-valued fields, because one can show that there is no lift of ordinary diffeomorphisms to matrix-valued diffeomorphisms. On the other hand, the action can presumably be constructed from perturbative string theory calculations. Based on the general characteristics of such calculations we determine a set of constraints on the action for N D0-branes, that ensure space-time covariance. These constraints can be solved order by order, but they are insufficient to determine the action completely. All solutions to the constraints obey the axioms of D-geometry. Moreover the action must contain new terms. This exhibits clearly that the answer is more than a suitable ordering of the action of a single D0 brane.Comment: latex, 38 page

Crosscaps in Gepner Models and the Moduli space of T2 Orientifolds

We study T^2 orientifolds and their moduli space in detail. Geometrical insight into the involutive automorphisms of T^2 allows a straightforward derivation of the moduli space of orientifolded T^2s. Using c=3 Gepner models, we compare the explicit worldsheet sigma model of an orientifolded T^2 compactification with the CFT results. In doing so, we derive half-supersymmetry preserving crosscap coefficients for generic unoriented Gepner models using simple current techniques to construct the charges and tensions of Calabi-Yau orientifold planes. For T^2s we are able to identify the O-plane charge directly as the number of fixed points of the involution; this number plays an important role throughout our analysis. At several points we make connections with the mathematical literature on real elliptic curves. We conclude with a preliminary extension of these results to elliptically fibered K3s.Comment: LaTeX, 59 pages, 21 figures (uses axodraw

Two-point function of a d=2d=2 quantum critical metal in the limit kF→∞k_F\rightarrow\infty, Nf→0N_f\rightarrow 0 with NfkFN_fk_F fixed

We show that the fermionic and bosonic spectrum of $d=2$ fermions at finite density coupled to a critical boson can be determined non-perturbatively in the combined limit $k_F\rightarrow {\infty}$, $N_f \rightarrow 0$ with $N_fk_F$ fixed. In this double scaling limit, the boson two-point function is corrected, but only at one-loop. This double scaling limit therefore incorporates the leading effect of Landau damping. The fermion two-point function is determined analytically in real space and numerically in (Euclidean) momentum space. The resulting spectrum is discontinuously connected to the quenched $N_f\rightarrow 0$ result. For $\omega \rightarrow 0$ with $k$ fixed the spectrum exhibits the distinct non-Fermi-liquid behavior previously surmised from the RPA approximation. However, the exact answer obtained here shows that the RPA result does not fully capture the IR of the theory.Comment: 37 pages, 10 figure

Hydrodynamic charge and heat transport on inhomogeneous curved spaces

We develop the theory of hydrodynamic charge and heat transport in strongly interacting quasi-relativistic systems on manifolds with inhomogeneous spatial curvature. In solid-state physics, this is analogous to strain disorder in the underlying lattice. In the hydrodynamic limit, we find that the thermal and electrical conductivities are dominated by viscous effects, and that the thermal conductivity is most sensitive to this disorder. We compare the effects of inhomogeneity in the spatial metric to inhomogeneity in the chemical potential, and discuss the extent to which our hydrodynamic theory is relevant for experimentally realizable condensed matter systems, including suspended graphene at the Dirac point.Comment: 15+8 pages, 4+1 figures; v2: added references, published versio

Pairing induced superconductivity in holography

We study pairing induced superconductivity in large $N$ strongly coupled systems at finite density using holography. In the weakly coupled dual gravitational theory the mechanism is conventional BCS theory. An IR hard wall cut-off is included to ensure that we can controllably address the dynamics of a single confined Fermi surface. We address in detail the interplay between the scalar order parameter field and fermion pairing. Adding an explicitly dynamical scalar operator with the same quantum numbers as the fermion-pair, the theory experiences a BCS/BEC crossover controlled by the relative scaling dimensions. We find the novel result that this BCS/BEC crossover exposes resonances in the canonical expectation value of the scalar operator. This occurs not only when the scaling dimension is degenerate with the Cooper pair, but also with that of higher derivative paired operators. We speculate that a proper definition of the order parameter which takes mixing with these operators into account stays finite nevertheless.Comment: 38 pages; 24 figures; revtex4 v2: Acknowledgements adde

Correlating correlation functions of primordial perturbations

We explore the correlations between correlation functions of the primordial curvature perturbation produced during inflation. We find that for general single field inflation, other than the source terms which depend on the model details, higher order correlation functions are characterized by the power spectrum, its spectral index and running. The correlation between the bispectrum and power spectrum is presented as an explicit example of our systematic approach.Comment: (v1) 8 pages, 1 figure; (v2) references added and typos corrected, to appear in Physical Review

Dynamical Topology Change in M Theory

We study topology change in M theory compactifications on Calabi-Yau three-folds in the presence of G flux (the four form field strength). In particular, we discuss vacuum solutions in strongly coupled heterotic string theory in which the topology change is inevitable within a single spacetime background. For rather generic choices of initial conditions, the field equations drive the Kahler moduli outside the classical moduli space of a Calabi-Yau manifold. Consistency of the solution suggests that degenerate flop curves - just as wrapped M theory fivebranes - carry magnetic charges under the four form field strength.Comment: 21 pages, LaTeX, 2 figures (eps