664 research outputs found
On the Stability of Compactified D=11 Supermembranes
We prove D=11 supermembrane theories wrapping around in an irreducible way
over on the target manifold, have a
hamiltonian with strict minima and without infinite dimensional valleys at the
minima for the bosonic sector. The minima occur at monopole connections of an
associated U(1) bundle over topologically non trivial Riemann surfaces of
arbitrary genus. Explicit expressions for the minimal connections in terms of
membrane maps are presented. The minimal maps and corresponding connections
satisfy the BPS condition with half SUSY.Comment: 15 pages, latex. Added comments in conclusions and more reference
BRST Formulation of 4-Monopoles
A supersymmetric gauge invariant action is constructed over any 4-dimensional
Riemannian manifold describing Witten's theory of 4-monopoles. The topological
supersymmetric algebra closes off-shell. The multiplets include the auxiliary
fields and the Wess-Zumino fields in an unusual way, arising naturally from
BRST gauge fixing. A new canonical approach over Riemann manifolds is followed,
using a Morse function as an euclidean time and taking into account the BRST
boundary conditions that come from the BFV formulation. This allows a
construction of the effective action starting from gauge principles.Comment: 18 pages, Amste
On Auxiliary Fields in BF Theories
We discuss the structure of auxiliary fields for non-Abelian BF theories in
arbitrary dimensions. By modifying the classical BRST operator, we build the
on-shell invariant complete quantum action. Therefore, we introduce the
auxiliary fields which close the BRST algebra and lead to the invariant
extension of the classical action.Comment: 7 pages, minor changes, typos in equations corrected and
acknowledgements adde
Interrelationship Between Broadband NIRS Measurements of Cerebral Cytochrome C Oxidase and Systemic Changes Indicates Injury Severity in Neonatal Encephalopathy
Perinatal hypoxic ischaemic encephalopathy (HIE) is associated with severe neurodevelopmental problems and mortality. There is a clinical need for techniques to provide cotside assessment of the injury extent. This study aims to use non-invasive cerebral broadband near-infrared spectroscopy (NIRS) in combination with systemic physiology to assess the severity of HIE injury. Broadband NIRS is used to measure the changes in haemodynamics, oxygenation and the oxidation state of cytochrome c oxidase (oxCCO). We used canonical correlation analysis (CCA), a multivariate statistical technique, to measure the relationship between cerebral broadband NIRS measurements and systemic physiology. A strong relationship between the metabolic marker, oxCCO, and systemic changes indicated severe brain injury; if more than 60 % of the oxCCO signal could be explained by the systemic variations, then the neurodevelopmental outcome was poor. This boundary has high sensitivity and specificity (100 and 83 %, respectively). Broadband NIRS measured concentration changes of the oxidation state of cytochrome c oxidase has the potential to become a useful cotside tool for assessment of injury severity following hypoxic ischaemic brain injury
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