AdS/CFT For Non-Boundary Manifolds

In its Euclidean formulation, the AdS/CFT correspondence begins as a study of Yang-Mills conformal field theories on the sphere, S^4. It has been successfully extended, however, to S^1 X S^3 and to the torus T^4. It is natural to hope that it can be made to work for any manifold on which it is possible to define a stable Yang-Mills conformal field theory. We consider a possible classification of such manifolds, and show how to deal with the most obvious objection : the existence of manifolds which cannot be represented as boundaries. We confirm Witten's suggestion that this can be done with the help of a brane in the bulk.Comment: 21 pages, 1 eps figure (1000x500), remarks on p-brane stress-tensor clarifie

Modeling-Free Bounds on Nonrenormalizable Isotropic Lorentz and CPT Violation in QED

The strongest bounds on some forms of Lorentz and CPT violation come from astrophysical data, and placing such bounds may require understanding and modeling distant sources of radiation. However, it is also desirable to have bounds that do not rely on these kinds of detailed models. Bounds that do not rely on any modeling of astrophysical objects may be derived both from laboratory experiments and certain kinds of astrophysical observations. The strongest such bounds on isotropic modifications of electron, positron, and photon dispersion relations of the form E^2 = p^2 + m^ 2 + epsilon p^3 come from data on cosmological birefringence, the absence of photon decay, and radiation from lepton beams. The bounds range in strength from the 4 x 10^(-13) to 6 x 10^(-33) (GeV)^(-1) levels.Comment: New title, 12 pages, version to appear in Phys. Rev.

There is No Ambiguity in the Radiatively Induced Gravitational Chern-Simons Term

Quantum corrections to Lorentz- and CPT-violating QED in flat spacetime produce unusual radiative corrections, which can be finite but of undetermined magnitude. The corresponding radiative corrections in a gravitational theory are even stranger, since the term in the fermion action involving a preferred axial vector $b^{\mu}$ would give rise to a gravitational Chern-Simons term that is proportional $b^{\mu}$, yet which actually does not break Lorentz invariance. Initially, the coefficient of this gravitational Chern-Simons term appears to have the same ambiguity as the coefficient for the analogous term in QED. However, this puzzle is resolved by the fact that the gravitational theory has more stringent gauge invariance requirements. Lorentz symmetry in a metric theory of gravity can only be broken spontaneously, and when the vector $b^{\mu}$ arises from spontaneous symmetry breaking, these specific radiative corrections are no longer ambiguous but instead must vanish identically.Comment: 16 page

How Does the Quark-Gluon Plasma Know the Collision Energy?

Heavy ion collisions at the LHC facility generate a Quark-Gluon Plasma (QGP) which, for central collisions, has a higher energy density and temperature than the plasma generated in central collisions at the RHIC. But sufficiently peripheral LHC collisions give rise to plasmas which have the \emph{same} energy density and temperature as the "central" RHIC plasmas. One might assume that the two versions of the QGP would have very similar properties (for example, with regard to jet quenching), but recent investigations have suggested that \emph{they do not}: the plasma "knows" that the overall collision energy is different in the two cases. We argue, using a gauge-gravity analysis, that the strong magnetic fields arising in one case (peripheral collisions), but not the other, may be relevant here. If the residual magnetic field in peripheral LHC plasmas is of the order of at least $eB\,\approx \,5\,m^2_{\pi}$, then the model predicts modifications of the relevant quenching parameter which approach those recently reported.Comment: 16 pages, one figure; version to appear in Nuclear Physics

ADVANCING THE SEPARATION SCIENCES THROUGH THE DELIVERY OF NEW MATERIALS, TECHNOLOGY AND METHODOLOGY.

A thesis and collection of works submitted to Plymouth University in partial fulfilment for the degree of DOCTOR OF SCIENC