The holographic dual of the entanglement wedge symplectic form

In this paper, we find the boundary dual of the symplectic form for the bulk fields in any entanglement wedge. The key ingredient is Uhlmann holonomy, which is a notion of parallel transport of purifications of density matrices based on a maximisation of transition probabilities. Using a replica trick, we compute this holonomy for curves of reduced states in boundary subregions of holographic QFTs at large N, subject to changes of operator insertions on the boundary. It is shown that the Berry phase along Uhlmann parallel paths may be written as the integral of an abelian connection whose curvature is the symplectic form of the entanglement wedge. This generalises previous work on holographic Berry curvature

Singular Instantons Made Regular

The singularity present in cosmological instantons of the Hawking-Turok type is resolved by a conformal transformation, where the conformal factor has a linear zero of codimension one. We show that if the underlying regular manifold is taken to have the topology of $RP^4$, and the conformal factor is taken to be a twisted field so that the zero is enforced, then one obtains a one-parameter family of solutions of the classical field equations, where the minimal action solution has the conformal zero located on a minimal volume noncontractible $RP^3$ submanifold. For instantons with two singularities, the corresponding topology is that of a cylinder $S^3\times [0,1]$ with D=4 analogues of `cross-caps' at each of the endpoints.Comment: 23 pages, compressed and RevTex file, including nine postscript figure files. Submitted versio

Surgical strategy to prevent cardiac injury during reoperation in infants

<p>Abstract</p> <p>Introduction</p> <p>Simplified Aortic Cannulation (SAC), wherein the innominate artery is used as the arterial inflow site rather than the ascending aorta, has proved to be a useful technique for arterial cannulation especially for small neonates undergoing complex cardiac operations. Since few technical options are available for re-entry cardiac injuries in small infants, we postulate that this technique may be equally helpful in those situations.</p> <p>Case Presentation</p> <p>We employed SAC in 4 infants undergoing reoperative cardiac surgery (prior Norwood, n = 2; prior arterial switch operation with suprasystemic pulmonary artery pressures after a Le Compte maneuver, n = 1; prior Ebstein's anomaly, n = 1). In all cases the innominate artery was exposed at the level of the supra-sternal notch, and a 3.5 mm expanded polytetrafluoroethylene (ePTFE) graft was anastomosed to the innominate artery (n = 3), and a 10 French cannula inserted into the graft for whole-body perfusion. Right atrial cannulation was obtained by dividing the anterior aspect of the diaphragm at the level of the xiphisternum, gaining easy access to the right atrial-inferior vena cava junction, without separating the sternal edges.</p> <p>Discussion and Evaluation</p> <p>All four infants successfully underwent their operations using SAC. In one case (2^ndstage palliation for hypoplastic left heart syndrome) a cardiac injury occurred upon sternal reentry, but utilizing SAC, this was repaired without consequence.</p> <p>Conclusion</p> <p>Simplified aortic cannulation and direct right atrial cannulation may be obtained without dividing the sternum in complex reoperative infant surgeries, without making additional incisions. This may be life-saving in reoperative cardiac injuries in small infants.</p

Effect of transannular patching on outcome after repair of tetralogy of Fallot.

Among 814 patients undergoing repair of tetralogy of Fallot with pulmonary stenosis between 1967 and May 1986, transannular patching in the current era was a weak risk factor for death early postoperatively (predicted 30-day mortality, 4\% with a transannular patch and 1.4\% without) and is not a risk factor for instantaneous risk of death late postoperatively (predicted 20-year survival including early death, 94\% with a transannular patch and 96.5\% without). Ninety-six percent of surviving patients were in New York Heart Association functional class I at last follow-up, and the slight decline in this percentage as the interval between operation and last follow-up lengthened could have been due to chance alone (p = 0.24) and was no different in patients with a transannular patch. Transannular patching was a risk factor for reoperation for pulmonary regurgitation late postoperatively, but only a 7\% incidence within 20 years is predicted when mild residual stenoses are beyond the patch: the incidence rises to about 20\% with important distal stenoses. Inferences from the study are relevant to the indications for transannular patching and insertion of allograft semilunar valves at the time of repair

Intermediate septal accessory pathways: Electrocardiographic characteristics, electrophysiologic observations and their surgical implications

AbstractIntermediate septal accessory pathways are located in close proximity to the atrioventricular (AV) node and His bundle, have unique features that distinguish them from typical anterior and posterior accessory pathways and have been associated with a high risk for unsuccessful pathway division and the production of complete AV block after surgery. Between July 1986 and May 1990, 4 of 70 patients (3 men and 1 woman; mean age 33 ± 13 years) undergoing surgery for accessory pathway division were found to have an intermediate septal accessory pathway. The presenting arrhythmia was atrial fibrillation with rapid anterograde conduction over the accessory pathway in two patients and recurrent orthodromic reciprocating tachycardia in two patients.In all patients, the delta wave on the electrocardiogram (ECG) was inversed in lead V1, but two patterns of delta wave configuration were observed. In three patients (type 1 intermediate septal accessory pathway), the delta wave was upright in lead II, inverted in lead III and isoelectric in lead aVF; the transition from a negative to an upright delta wave occurred in lead V2. The fourth patient exhibited a different delta wave pattern (type 2 intermediate septal accessory pathway). The delta wave was upright in each of leads II, III and aVF; the transition from a negative to an upright delta wave occurred at lead V3.Intraoperative electrophysiologic study localized the atrial insertion of type 1 pathways to the midpoint of Koch's triangle close to the AV node. In the one patient with a type 1 pathway in which both anterograde and retrograde accessory pathway conduction was present, preoperative catheter mapping demonstrated that earliest retrograde atrial activation occurred near the foramen ovale. Intraoperative mapping during anterograde conduction over the type 1 pathway demonstrated earliest epicardial ventricular activation to occur simultaneously at the crux and the base of the aorta. The atrial insertion of the type 2 intermediate septal accessory pathway was localized to the apex of Koch's triangle in close proximity to the bundle of His. Preoperative catheter mapping revealed that earliest retrograde atrial activation occurred on the His bundle electrogram. Intraoperative mapping during anterograde conduction over the type 2 pathway demonstrated that earliest epicardial ventricular activation occurred anteriorly at the base of the aorta.Intraoperative ablation of the intermediate septal accessory pathway was accomplished by cooling the endocardium at the site of pathway insertion on the atrial side of the tricuspid anulus with a 5 mm cryoprobe. Patients with a type 1 intermediate septal accessory pathway had preservation of AV conduction, but the patient with the type 2 pathway did not and required permanent pacing. At late follow-up study, no patient has had return of intermediate septal accessory pathway conduction. Distinguishing an intermediate septal accessory pathway close to the AV node (type 1) from one close to the His bundle (type 2) is useful to predict both surgical success and success without the production of permanent complete AV block

Design and Testing of a Feed-Forward Control System for Deployable Vortex Generators Dependent on Angle of Attack

A vortex generator (VG hereafter) is a common feature of an aircraft wing that disturbs the flow on the leading edge of the wing, thus energizing the boundary layer and reducing flow separation. For an aircraft experiencing flow separation, VGs can increase the lift-to-drag ratio of the wing and prevent stall; however, if flow separation isn’t an issue, the unnecessary frontal area of the VGs has the potential to produce parasitic drag. This study seeks to determine whether the use of a deployment system can improve the performance of VG’s by raising or lowering them depending on the angle of attack of the wing. Using wind tunnel testing, a feed-forward control deployment system was developed which improved the lift to drag ratio for some angles of attack, and it was determined that further development could potentially produce a system with significant improvements in aircraft efficiency

Homogeneous Modes of Cosmological Instantons

We discuss the O(4) invariant perturbation modes of cosmological instantons. These modes are spatially homogeneous in Lorentzian spacetime and thus not relevant to density perturbations. But their properties are important in establishing the meaning of the Euclidean path integral. If negative modes are present, the Euclidean path integral is not well defined, but may nevertheless be useful in an approximate description of the decay of an unstable state. When gravitational dynamics is included, counting negative modes requires a careful treatment of the conformal factor problem. We demonstrate that for an appropriate choice of coordinate on phase space, the second order Euclidean action is bounded below for normalized perturbations and has a finite number of negative modes. We prove that there is a negative mode for many gravitational instantons of the Hawking-Moss or Coleman-De Luccia type, and discuss the associated spectral flow. We also investigate Hawking-Turok constrained instantons, which occur in a generic inflationary model. Implementing the regularization and constraint proposed by Kirklin, Turok and Wiseman, we find that those instantons leading to substantial inflation do not possess negative modes. Using an alternate regularization and constraint motivated by reduction from five dimensions, we find a negative mode is present. These investigations shed new light on the suitability of Euclidean quantum gravity as a potential description of our universe.Comment: 16 pages, compressed and RevTex file, including one postscript figure fil

From Big Crunch to Big Bang

We consider conditions under which a universe contracting towards a big crunch can make a transition to an expanding big bang universe. A promising example is 11-dimensional M-theory in which the eleventh dimension collapses, bounces, and re-expands. At the bounce, the model can reduce to a weakly coupled heterotic string theory and, we conjecture, it may be possible to follow the transition from contraction to expansion. The possibility opens the door to new classes of cosmological models. For example, we discuss how it suggests a major simplification and modification of the recently proposed ekpyrotic scenario.Comment: 16 pages, compressed and RevTex file, including three postscript figure files. Minor changes, version to appear in Physical Review

Why Does Inflation Start at the Top of the Hill?

We show why the universe started in an unstable de Sitter state. The quantum origin of our universe implies one must take a `top down' approach to the problem of initial conditions in cosmology, in which the histories that contribute to the path integral, depend on the observable being measured. Using the no boundary proposal to specify the class of histories, we study the quantum cosmological origin of an inflationary universe in theories like trace anomaly driven inflation in which the effective potential has a local maximum. We find that an expanding universe is most likely to emerge in an unstable de Sitter state, by semiclassical tunneling via a Hawking-Moss instanton. Since the top down view is forced upon us by the quantum nature of the universe, we argue that the approach developed here should still apply when the framework of quantum cosmology will be based on M-Theory.Comment: 21 pages, 1 figur