746 research outputs found
Gauged Six-dimensional Supergravity from Massive Type IIA
We obtain the complete non-linear Kaluza-Klein ansatz for the reduction of
the bosonic sector of massive type IIA supergravity to the Romans F(4) gauged
supergravity in six dimensions. The latter arises as a consistent warped S^4
reduction.Comment: Latex, 7 page
Anti-de Sitter space, branes, singletons, superconformal field theories and all that
There has recently been a revival of interest in anti de-Sitter space (AdS)
brought about by the conjectured duality beteeen physics in the bulk of AdS and
a conformal field theory on the boundary. Since the whole subject of branes,
singletons and superconformal field theories on the AdS boundary was an active
area of research about ten years ago, I begin with a historical review,
including the ``Membrane at the end of the universe'' idea. Next I discuss two
recent papers with Lu and Pope on on and on , respectively. In each case we note that odd-dimensional spheres
may be regarded as U(1) bundles over and that this
permits an unconventional ``Hopf''duality along the U(1) fibre. This leads in
particular to the phenomenon of BPS without BPS whereby states which appear to
be non-BPS in one picture are seen to be BPS in the dual picture.Comment: Minor improvements. 37 pages Latex. Based on talks delivered at the
the PASCOS 98 conference, Northeastern University, March 1998; the
Superfivebranes and Physics in 5+1 Dimensions conference, ICTP, Trieste,
Italy, April 1998; the Arnowitt Fest, Texas A&M University, April 1998; the
Strings 98 conference, ITP, Santa Barbara, June 199
Heat propagation models for superconducting nanobridges at millikelvin temperatures
Nanoscale superconducting quantum interference devices (nanoSQUIDs) most commonly use Dayem bridges as Josephson elements to reduce the loop size and achieve high spin sensitivity. Except at temperatures close to the critical temperature T c, the electrical characteristics of these bridges exhibit undesirable thermal hysteresis which complicates device operation. This makes proper thermal analysis an essential design consideration for optimising nanoSQUID performance at ultralow temperatures. However the existing theoretical models for this hysteresis were developed for micron-scale devices operating close to liquid helium temperatures, and are not fully applicable to a new generation of much smaller devices operating at significantly lower temperatures. We have therefore developed a new analytic heat model which enables a more accurate prediction of the thermal behaviour in such circumstances. We demonstrate that this model is in good agreement with experimental results measured down to 100 mK and discuss its validity for different nanoSQUID geometries
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