53 research outputs found
Wormholes in AdS
We construct a few Euclidean supergravity solutions with multiple boundaries.
We consider examples where the corresponding boundary field theory is well
defined on each boundary. We point out that these configurations are puzzling
from the AdS/CFT point of view. A proper understanding of the AdS/CFT
dictionary for these cases might yield some information about the physics of
closed universes.Comment: 38 pages, 2 figures, harvmac. v2: minor typos corrected and
references adde
Omega-3 polyunsaturated fatty acids: Their potential role in blood pressure prevention and management
Omega-3 polyunsaturated fatty acids (PUFAs) from fish and fish oils appear to protect against coronary heart disease: their dietary intake is in fact inversely associated to cardiovascular disease morbidity/mortality in population studies. Recent evidence suggests that at least part of their heart protective effect is mediated by a relatively small but significant decrease in blood pressure level. In fact, omega-3 PUFAs exhibit wide-ranging biological actions that include regulating both vasomotor tone and renal sodium excretion, partly competing with omega-6 PUFAs for common metabolic enzymes and thereby decreasing the production of vasocostrincting rather than vasodilating and anti-inflammatory eicosanoids. PUFAs also reduce angiotensin-converting enzyme (ACE) activity, angiotensin II formation, TGF-beta expression, enhance eNO generation and activate the parasympathetic nervous system. The final result is improved vasodilation and arterial compliance of both small and large arteries. Preliminary clinical trials involving dyslipidemic patients, diabetics and elderly subjects, as well as normotensive and hypertensive subjects confirm this working hypothesis. Future research will clarify if PUFA supplementation could improve the antihypertensive action of specific blood pressure lowering drug classes and of statins
de Sitter gauge theories and induced gravities
Pure de Sitter, anti de Sitter, and orthogonal gauge theories in
four-dimensional Euclidean spacetime are studied. It is shown that, if the
theory is asymptotically free and a dynamical mass is generated, then an
effective geometry may be induced and a gravity theory emerges. The asymptotic
freedom and the running of the mass might account for an In\"on\"u-Wigner
contraction which induces a breaking of the gauge group to the Lorentz group,
while the mass itself is responsible for the coset sector of the gauge field to
be identified with the effective vierbein. Furthermore, the resulting local
isometries are Lorentzian for the anti de Sitter group and Euclidean for the de
Sitter and orthogonal groups.Comment: Sections added. Text reviewed. References added. 14 pages, no
figures. Final version to appear in EPJ
Holography and Quaternionic Taub-NUT
As a concrete application of the holographic correspondence to manifolds
which are only asymptotically Anti-de Sitter, we take a closer look at the
quaternionic Taub-NUT space. This is a four dimensional, non-compact,
inhomogeneous, riemannian manifold with the interesting property of smoothly
interpolating between two symmetric spaces, AdS_4 itself and the coset
SU(2,1)/U(2). Even more interesting is the fact that the scalar curvature of
the induced conformal structure at the boundary (corresponding to a squashed
three-sphere) changes sign as we interpolate between these two limiting cases.
Using twistor methods, we construct the bulk-to-bulk and bulk-to-boundary
propagators for conformally coupled scalars on quaternionic Taub-NUT. This may
eventually enable us to calculate correlation functions in the dual strongly
coupled CFT on a squashed S^3 using the standard AdS/CFT prescription.Comment: 1+36 pages, no figures. Some minor typos correcte
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Think Again – Supplying War: Reappraising Military Logistics and Its Centrality to Strategy and War
This article argues that logistics constrains strategic opportunity while itself being heavily circumscribed by strategic and operational planning. With the academic literature all but ignoring the centrality of logistics to strategy and war, this article argues for a reappraisal of the critical role of military logistics, and posits that the study and conduct of war and strategy are incomplete at best or false at worst when they ignore this crucial component of the art of war. The article conceptualises the logistics–strategy nexus in a novel way, explores its contemporary manifestation in an age of uncertainty, and applies it to a detailed case study of UK operations in Iraq and Afghanistan since 2001
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