Chiral Ring Generating Functions & Branches of Moduli Space

34 pages, 7 figures34 pages, 7 figures34 pages, 7 figuresWe consider the worldvolume theory of N D3-branes transverse to various non-compact Calabi-Yau spaces, and describe subtleties in the counting of chiral primary operators in such theories due to the presence of multiple branches of moduli space. Extra branches, beyond those directly related to the transverse geometry, result in additional terms in the generating functions for single- and multi-trace operators. Ideals in the N=1 chiral ring correspond to various branches and, in the large N limit, the operator counting reveals a product of Fock spaces, including the Fock space of bosons on the space transverse to the branes

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We show that when an N=2 SCFT flows to an N=1 SCFT via giving a mass to the adjoint chiral superfield in a vector multiplet with marginal coupling, the central charges a and c of the N=2 theory are related to those of the N=1 theory by a universal linear transformation. In the large N limit, this relationship implies that the central charges obey a_IR/a_UV=c_IR/c_UV=27/32. This gives a physical explanation to many examples of this number found in the literature, and also suggests the existence of a flow between some theories not previously thought to be connected.Comment: 3 pages. v2: references added, minor typos correcte

Torsion and Supersymmetry Breaking

We identify the auxiliary fields in the hypermultiplets of type IIB string theory compactified on a Calabi-Yau manifold, using a combination of worldsheet and supergravity techniques. The SUSY-breaking squark and gaugino masses in type IIB models depend on these auxiliary fields, which parametrize deformations away from a pure Calabi-Yau compactification to one with NS-NS 3-form flux and SU(3) x SU(3) structure. Worldsheet arguments show that such compactifications are generically globally nongeometric. Our results, combined with earlier results for type IIA compactifications, imply that these deformations are the mirrors of NS-NS 3-form flux, in accord with work from the supergravity point of view. Using the worldsheet current algebra, we explain why mirror symmetry may continue to hold in the presence of fluxes breaking the symmetries (e.g., (2,2) SUSY) on which mirror symmetry is typically taken to depend. Finally, we give evidence that nonperturbative worldsheet effects (such as worldsheet instantons) provide important corrections to the supergravity picture in the presence of auxiliary fields for Kahler moduli.Comment: 43 pages, harvmac. v2: typos corrected, minor revision

Posteroanterior Cervical Transcutaneous Spinal Cord Stimulation: Interactions with Cortical and Peripheral Nerve Stimulation

Transcutaneous spinal cord stimulation (TSCS) has demonstrated potential to beneficially modulate spinal cord motor and autonomic circuitry. We are interested in pairing cervical TSCS with other forms of nervous system stimulation to enhance synaptic plasticity in circuits serving hand function. We use a novel configuration for cervical TSCS in which the anode is placed anteriorly over ~C4–C5 and the cathode posteriorly over ~T2–T4. We measured the effects of single pulses of TSCS paired with single pulses of motor cortex or median nerve stimulation timed to arrive at the cervical spinal cord at varying intervals. In 13 participants with and 15 participants without chronic cervical spinal cord injury, we observed that subthreshold TSCS facilitates hand muscle responses to motor cortex stimulation, with a tendency toward greater facilitation when TSCS is timed to arrive at cervical synapses simultaneously or up to 10 milliseconds after cortical stimulus arrival. Single pulses of subthreshold TSCS had no effect on the amplitudes of median H-reflex responses or F-wave responses. These findings support a model in which TSCS paired with appropriately timed cortical stimulation has the potential to facilitate convergent transmission between descending motor circuits, segmental afferents, and spinal motor neurons serving the hand. Studies with larger numbers of participants and repetitively paired cortical and spinal stimulation are needed

Backreacted T-folds and non-geometric regions in configuration space

We provide the backreaction of the T-fold doubly T-dual to a background with NSNS three-form flux on a three-torus. We extend the backreacted T-fold to include cases with a flux localized in one out of three directions. We analyze the resulting monodromy domain walls and vortices. In these backgrounds, we give an analysis of the action of T-duality on observables like charges and Wilson surfaces. We analyze arguments for the existence of regions in the configuration space of second quantized string theory that cannot be reduced to geometry. Finally, by allowing for space-dependent moduli, we find a supergravity solution which is a T-fold with hyperbolic monodromies.Comment: 25 pages, 4 figures; v2: minor changes, reference adde

D-Terms from Generalized NS-NS Fluxes in Type II

Orientifolds of type II string theory admit a certain set of generalized NS-NS fluxes, including not only the three-form field strength H, but also metric and non-geometric fluxes, which are related to H by T-duality. We describe in general how these fluxes appear as parameters of an effective N=1 supergravity theory in four dimensions, and in particular how certain generalized NS-NS fluxes can act as charges for R-R axions, leading to D-term contributions to the effective scalar potential. We illustrate these phenomena in type IIB with the example of a certain orientifold of T^6/Z_4.Comment: 31+1 pages, uses utarticle.cls; v2: references adde

T-duality in the weakly curved background

We consider the closed string propagating in the weakly curved background which consists of constant metric and Kalb-Ramond field with infinitesimally small coordinate dependent part. We propose the procedure for constructing the T-dual theory, performing T-duality transformations along coordinates on which the Kalb-Ramond field depends. The obtained theory is defined in the non-geometric double space, described by the Lagrange multiplier $y_\mu$ and its $T$-dual $\tilde{y}_\mu$. We apply the proposed T-duality procedure to the T-dual theory and obtain the initial one. We discuss the standard relations between T-dual theories that the equations of motion and momenta modes of one theory are the Bianchi identities and the winding modes of the other

Heterotic compactifications on SU(2)-structure backgrounds

In this paper we study the reduction of heterotic string theory on SU(2)-structure backgrounds. We compute the bosonic low-energy gauged N=2 supergravity specified by the Killing vectors corresponding to the gauged isometries. We check that the obtained Lagrangian is consistent with the one of N=2 local supersymmetry. We also determine the Killing prepotentials.Comment: reference added, corrected typos and some factor