Effective Theory of Braid Excitations of Quantum Geometry in terms of Feynman Diagrams

We study interactions amongst topologically conserved excitations of quantum theories of gravity, in particular the braid excitations of four-valent spin networks. These have been shown previously to propagate and interact under evolution rules of spin foam models. We show that the dynamics of these braid excitations can be described by an effective theory based on Feynman diagrams. In this language, braids which are actively interacting are analogous to bosons, in that the topological conservation laws permit them to be singly created and destroyed. Exchanges of these excitations give rise to interactions between braids which are charged under the topological conservation rules.Comment: 23 pages, 7 figures. Accepted by Nucl. Phys.

How the City of London lost at Brexit: a historical perspective

The nature of the City of London as an offshore financial centre has long made London dependent on the British state providing protection from external political regulation, even as London’s foreign currency business separated its interests from British governments’ economic policy preoccupations. Since the 2008 crash and the onset of the eurozone crisis, London has faced threats to both its autonomy from external regulatory demands and to its offshore business interests at the same time as the long-standing external statecraft of British governments around EU membership has broken down. The Cameron governments’ efforts to protect the City within the European Union under political conditions that were transformed by the eurozone crisis exposed the limits of Britain’s position as a member of the European Union. When David Cameron then tried to resolve the problem of EU membership through a referendum he made it extremely difficult to defend the City’s broader commercial interests in the Single European Market because freedom of movement issues weighed significantly more in British domestic politics than financial services

GeV Emission from Collisional Magnetized Gamma Ray Bursts

Magnetic fields may play a dominant role in gamma-ray bursts, and recent observations by the Fermi satellite indicate that GeV radiation, when detected, arrives delayed by seconds from the onset of the MeV component. Motivated by this, we discuss a magnetically dominated jet model where both magnetic dissipation and nuclear collisions are important. We show that, for parameters typical of the observed bursts, such a model involving a realistic jet structure can reproduce the general features of the MeV and a separate GeV radiation component, including the time delay between the two. The model also predicts a multi-GeV neutrino component.Comment: ApJ(Lett.), in pres

Nonmethane hydrocarbon measurements in the North Atlantic Flight Corridor during the Subsonic Assessment Ozone and Nitrogen Oxide Experiment

Mixing ratios of nonmethane hydrocarbons (NMHCs) were not enhanced in whole air samples collected within the North Atlantic Flight Corridor (NAFC) during the fall of 1997. The investigation was conducted aboard NASA's DC-8 research aircraft, as part of the Subsonic Assessment (SASS) Ozone and Nitrogen Oxide Experiment (SONEX). NMHC enhancements were not detected within the general organized tracking system of the NAFC, nor during two tail chases of the DC-8's own exhaust. Because positive evidence of aircraft emissions was demonstrated by enhancements in both nitrogen oxides and condensation nuclei during SONEX, the NMHC results suggest that the commercial air traffic fleet operating in the North Atlantic region does not contribute at all or contributes negligibly to NMHCs in the NAFC. Copyright 2000 by the American Geophysical Union

Experimental cyclic inter-conversion between Coherence and Quantum Correlations

Quantum resource theories seek to quantify sources of non-classicality that bestow quantum technologies their operational advantage. Chief among these are studies of quantum correlations and quantum coherence. The former to isolate non-classicality in the correlations between systems, the latter to capture non-classicality of quantum superpositions within a single physical system. Here we present a scheme that cyclically inter-converts between these resources without loss. The first stage converts coherence present in an input system into correlations with an ancilla. The second stage harnesses these correlations to restore coherence on the input system by measurement of the ancilla. We experimentally demonstrate this inter-conversion process using linear optics. Our experiment highlights the connection between non-classicality of correlations and non-classicality within local quantum systems, and provides potential flexibilities in exploiting one resource to perform tasks normally associated with the other.Comment: 8 pages, 4 figures, comments welcom

Di-μ-sulfato-bis­{[bis­(3,5-dimethyl­pyrazol-1-yl)methane]copper(II)}

The mol­ecule of the title compound, [Cu2(SO4)2(C11H16N4)2], sits on a center of symmetry. The CuII atom has a distorted trigonal–bipyramidal coordination geometry comprising three O atoms of the two symmetry-related SO4 2− anions and two N atoms from one bis­(3,5-dimethyl­pyrazol-1-yl)methane ligand