Heterotic-Heterotic String Duality and Multiple K3 Fibrations

A type IIA string compactified on a Calabi-Yau manifold which admits a K3 fibration is believed to be equivalent to a heterotic string in four dimensions. We study cases where a Calabi-Yau manifold can have more than one such fibration leading to equivalences between perturbatively inequivalent heterotic strings. This allows an analysis of an example in six dimensions due to Duff, Minasian and Witten and enables us to go some way to prove a conjecture by Kachru and Vafa. The interplay between gauge groups which arise perturbatively and nonperturbatively is seen clearly in this example. As an extreme case we discuss a Calabi-Yau manifold which admits an infinite number of K3 fibrations leading to infinite set of equivalent heterotic strings.Comment: 13 pages, LaTe

Kummer surfaces associated with Seiberg-Witten curves

By carrying out a rational transformation on the base curve $\mathbb{CP}^1$ of the Seiberg-Witten curve for $\mathcal{N}=2$ supersymmetric pure $\mathrm{SU}(2)$-gauge theory, we obtain a family of Jacobian elliptic K3 surfaces of Picard rank 17. The isogeny relating the Seiberg-Witten curve for pure $\mathrm{SU}(2)$-gauge theory to the one for $\mathrm{SU}(2)$-gauge theory with $N_f=2$ massless hypermultiplets extends to define a Nikulin involution on each K3 surface in the family. We show that the desingularization of the quotient of the K3 surface by the involution is isomorphic to a Kummer surface of the Jacobian variety of a curve of genus two. We then derive a relation between the Yukawa coupling associated with the elliptic K3 surface and the Yukawa coupling of pure $\mathrm{SU}(2)$-gauge theory.Comment: 26 pages, LaTe

Branes, Calabi-Yau Spaces, and Toroidal Compactification of the N=1 Six-Dimensional E_8 Theory

We consider compactifications of the N=1, d=6, E_8 theory on tori to five, four, and three dimensions and learn about some properties of this theory. As a by-product we derive the SL(2,\IZ) duality of the N=2, d=4, SU(2) theory with N_f=4. Using this theory on a D-brane probe we shed new light on the singularities of F-theory compactifications to eight dimensions. As another application we consider compactifications of F-theory, M-theory and the IIA string on (singular) Calabi-Yau spaces where our theory appears in spacetime. Our viewpoint leads to a new perspective on the nature of the singularities in the moduli space and their spacetime interpretations. In particular, we have a universal understanding of how the singularities in the classical moduli space of Calabi--Yau spaces are modified by worldsheet instantons to singularities in the moduli space of the corresponding conformal field theories.Comment: 40 pages, 2 figures, harvmac with epsf. Minor corrections, references adde

Affine 7-brane Backgrounds and Five-Dimensional ENE_N Theories on S1S^1

Elliptic curves for the 7-brane configurations realizing the affine Lie algebras \wh E_n $(1 \leq n \leq 8)$ and \wh{\wt E}_n $(n=0,1)$ are systematically derived from the cubic equation for a rational elliptic surface. It is then shown that the \wh E_n 7-branes describe the discriminant locus of the elliptic curves for five-dimensional (5D) N=1 $E_n$ theories compactified on a circle. This is in accordance with a recent construction of 5D N=1 $E_n$ theories on the IIB 5-brane web with 7-branes, and indicates the validity of the D3 probe picture for 5D $E_n$ theories on \bR^4 \times S^1. Using the \wh E_n curves we also study the compactification of 5D $E_n$ theories to four dimensions.Comment: 23 pages, Latex, no figures, some statements clarified, typos corrected, references and note adde

Calabi-Yau Spaces and Five Dimensional Field Theories with Exceptional Gauge Symmetry

Five dimensional field theories with exceptional gauge groups are engineered from degenerations of Calabi-Yau threefolds. The structure of the Coulomb branch is analyzed in terms of relative K\"ahler cones. For low number of flavors, the geometric construction leads to new five dimensional fixed points.Comment: Harvmac, 42 pages, 21 Postscript figure

Mordell-Weil Lattice via String Junctions

We analyze the structure of singularities, Mordell-Weil lattices and torsions of a rational elliptic surface using string junctions in the background of 12 7-branes. The classification of the Mordell-Weil lattices due to Oguiso-Shioda is reproduced in terms of the junction lattice. In this analysis an important role played by the global structure of the surface is observed. It is then found that the torsions in the Mordell-Weil group are generated by the fraction of loop junctions which represent the imaginary roots of the loop algebra $\hat E_9$. From the structure of the Mordell-Weil lattice we find 7-brane configurations which support non-BPS junctions carrying conserved Abelian charges.Comment: 35 pages, Latex, 3 figure

Case Report: Fremitus Nystagmus in Superior Canal Dehiscence Syndrome.

Superior canal dehiscence syndrome (SCDS) is a structural bony defect of the roof of the superior semi-circular canal into the middle cranial fossa and is responsible for the creation of a third window, which alters the dynamics of the inner ear. During humming, vibratory waves entering the vestibulum and cochlea are re-routed through the dehiscence, leading to stimulation of the otolithic and ampullary vestibular organs. This is responsible for the torsional-vertical nystagmus known as "fremitus nystagmus". In this case report, we video-document a rare case of fremitus nystagmus and its resolution after plugging of the superior semi-circular canal

Quantifying the influence of magnetic vestibular stimulation on spatial tasks

Strong magnetic fields induce dizziness, vertigo, and nystagmus due to Lorentz forces acting on the cupula in the semi-circular canals (Roberts et al. 2012). Studies using passive motion, galvanic or caloric vestibular stimulation have shown that vestibular information can interfere with cognitive tasks with spatial components (e.g., Falconer & Mast, 2012). In this study, we were interested if magnetic vestibular stimulation (MVS) in a 7 Tesla MRI scanner influences performance in cognitive tasks with spatial components. 30 participants solved a mental rotation task in a 7T MR scanner with an egocentric and an allocentric strategy. The findings of previous studies suggest that only the egocentric strategy should be affected by altered vestibular information. The allocentric strategy served as a control condition. The strength of MVS was manipulated within participants by letting them solve the task inside the bore with two different head positions, resulting in a stronger and a weaker stimulation condition (Wyssen et al., in press). Response time analyses showed that overall participants responded slower under stronger stimulation than under weaker stimulation. This effect of magnetic vestibular stimulation on response times was only present in the egocentric mental rotation task but not when participants used the allocentric strategy. However, participants showed inter-individual differences, and the strength of the individual effect could not be linked to the individual stimulation strength quantified by nystagmus. The findings of our study suggest that MVS could influence cognitive tasks with spatial components in MRI scanners. The effect of magnetic vestibular stimulation should be considered in fMRI studies using ultra-high magnetic fields using spatial tasks, as it could be a possible confounder. In the future magnet ic vestibular stimulation could serve as a tool to investigate the interrelation of vestibular information and spatial cognition. References: (1) Roberts, D. C., Marcelli, V., Gillen, J. S., Carey, J. P., Della Santina, C. C., & Zee, D. S. (2011). MRI magnetic field stimulates rotational sensors of the brain. Curr. Biol., 21(19), 1635-1640. (2) Falconer C. J., Mast F.W. (2012). Balancing the mind: vestibular induced facilitation of egocentric mental transformations. Exp. Psychol., 59(6):332-9. (3) Wyssen, G., Morrison, M., Korda, A., Wimmer, W., Otero-Millan, J., Ertl, M., Szukics, A.A., Wyss, T., Wagner, F., Caversaccio, M.D., Mantokoudis, G., Mast, F.W. (in press). Measuring the Influence of Magnetic Vestibular Stimulation on Nystagmus, Self-Motion Perception, and Cognitive Performance in a 7T MRT. J. Vis. Exp., e64022

Toric bases for 6D F-theory models

We find all smooth toric bases that support elliptically fibered Calabi-Yau threefolds, using the intersection structure of the irreducible effective divisors on the base. These bases can be used for F-theory constructions of six-dimensional quantum supergravity theories. There are 61,539 distinct possible toric bases. The associated 6D supergravity theories have a number of tensor multiplets ranging from 0 to 193. For each base an explicit Weierstrass parameterization can be determined in terms of the toric data. The toric counting of parameters matches with the gravitational anomaly constraint on massless fields. For bases associated with theories having a large number of tensor multiplets, there is a large non-Higgsable gauge group containing multiple irreducible gauge group factors, particularly those having algebras e_8, f_4 and (g_2 + su(2)) with minimal (non-Higgsable) matter.Comment: 39 pages, 13 figures, one appendix; ancillary data file contains list of 61,539 bases; v2: minor correctio

Impact of Opioid-Free Anesthesia on Postoperative Nausea & Vomiting: A Scoping Review

Purpose The purpose of this DNP Scoping Review is to compare the current literature regarding the incidence of postoperative nausea and vomiting (PONV) in adult patients who underwent general anesthesia when opioids are used intraoperatively versus a multimodal non-opioid-based intraoperative general anesthetic plan Specific Aims: Incidence of postoperative nausea & vomiting Postoperative rescue antiemetic administration Length of stay in postoperative anesthesia care unit (PACU) Incidence of intraoperative adverse event