Non-Perturbative Topological Strings And Conformal Blocks

We give a non-perturbative completion of a class of closed topological string theories in terms of building blocks of dual open strings. In the specific case where the open string is given by a matrix model these blocks correspond to a choice of integration contour. We then apply this definition to the AGT setup where the dual matrix model has logarithmic potential and is conjecturally equivalent to Liouville conformal field theory. By studying the natural contours of these matrix integrals and their monodromy properties, we propose a precise map between topological string blocks and Liouville conformal blocks. Remarkably, this description makes use of the light-cone diagrams of closed string field theory, where the critical points of the matrix potential correspond to string interaction points.Comment: 36 page

The gravitational dynamics of warped throats

We investigate the time evolution due to gravitational dynamics of a particular spacetime commonly used in brane-cosmology and string compactifications, namely the Klebanov-Strassler geometry, which is achieved by adding a perturbation to the momentum of the static solution. We observe the effects this has on the spacetime and look for evidence of black hole formation or collapsing cycles which could lead to singular geometry. The cycles are seen to commonly re-expand after reaching a minimum value, showing the stability of the solution against perturbations which would change its size. However black holes are observed to form for certain perturbations, which could impede common uses of the throat's stable tip

Suspected hyponatremia-induced Brugada phenocopy

Koomatie Ramsaroop,1 Rajeev Seecheran,1 Valmiki Seecheran,1 Sangeeta Persad,1 Stanley Giddings,2 Boris Mohammed,1 Naveen Anand Seecheran2 1Department of Medicine, North Central Regional Health Authority, Mt Hope, Trinidad and Tobago; 2Department of Clinical Medical Sciences, The University of the West Indies, St Augustine, Trinidad and Tobago Abstract: Brugada syndrome is a genetic condition that predisposes to an increased risk of ventricular fibrillation and sudden cardiac death in a structurally normal heart. The Brugada type 1 electrocardiogram (ECG) pattern may occur independently of the actual syndrome, and this clinical phenomenon is often referred to as Brugada phenocopy. There are several other factors which have been known to induce this electrocardiographic pattern, and currently, there is a paucity of literature with respect to the pattern that is observed in patients with electrolyte disturbances, specifically hyponatremia. This case report highlights a suspected hyponatremia-induced Brugada type 1 ECG pattern, which subsequently normalized following resolution of the electrolyte derangement. Keywords: Brugada syndrome, Brugada phenocopy, Brugada type pattern, hyponatremi

Hindcasts of potential harmful algal bloom transport pathways on the Pacific Northwest coast

Harmful algal blooms (HABs) pose a significant threat to human and marine organism health, and negatively impact coastal economies around the world. An improved understanding of HAB formation and transport is required to improve forecasting skill. A realistic numerical simulation of the US Pacific Northwest region is used to investigate transport pathways from known HAB formation hot spots, specifically for Pseudo-nitzschia (Pn), to the coast. We show that transport pathways are seasonal, with transport to the Washington (WA) coast from a northern source (the Juan de Fuca Eddy) during the summer/fall upwelling season and from a southern source (Heceta Bank) during the winter/early spring due to the predominant wind-driven currents. Interannual variability in transport from the northern source is related to the degree of wind intermittency with more transport during years with more frequent relaxation/downwelling events. The Columbia River plume acts to mitigate transport to the coast as the plume front blocks onshore transport. The plume's influence on alongshore transport is variable although critical in aiding transport from the southern source to the WA coast via plume entrainment. Overall transport from our simulations captures most observed Pn HAB beach events from 2004 to 2007 (characterized by Pseudo-nitzschia cell abundance); however, numerous false positives occur. We show that incorporating phytoplankton biomass results from a coupled biogeochemical model reduces the number of false positives significantly and thus improves our Pn HAB predictions. Key Points Potential PNW HAB transport is seasonal, consistent with regional currents Transport is blocked by the Columbia River plume unless entrainment occurs A coupled hydrodynamic-biological model can predict PNW Pn HAB transport paths © 2014. American Geophysical Union. All Rights Reserved