415 research outputs found
Gravitomagnetism and Relative Observer Clock Effects
The gravitomagnetic clock effect and the Sagnac effect for circularly
rotating orbits in stationary axisymmetric spacetimes are studied from a
relative observer point of view, clarifying their relationships and the roles
played by special observer families. In particular Semer\'ak's recent
characterization of extremely accelerated observers in terms of the two-clock
clock effect is shown to be complemented by a similarly special property of the
single-clock clock effect.Comment: 19 pages, LaTeX, IOP macros with package epsf and 1 eps figure, to
appear in Classical and Quantum Gravity, slight revisio
The Sagnac Phase Shift suggested by the Aharonov-Bohm effect for relativistic matter beams
The phase shift due to the Sagnac Effect, for relativistic matter beams
counter-propagating in a rotating interferometer, is deduced on the bases of a
a formal analogy with the the Aharonov-Bohm effect. A procedure outlined by
Sakurai, in which non relativistic quantum mechanics and newtonian physics
appear together with some intrinsically relativistic elements, is generalized
to a fully relativistic context, using the Cattaneo's splitting technique. This
approach leads to an exact derivation, in a self-consistently relativistic way,
of the Sagnac effect. Sakurai's result is recovered in the first order
approximation.Comment: 18 pages, LaTeX, 2 EPS figures. To appear in General Relativity and
Gravitatio
Uveal melanoma UK national guidelines
The United Kingdom (UK) uveal melanoma guideline development group used an evidence based systematic approach (Scottish Intercollegiate Guidelines Network (SIGN)) to make recommendations in key areas of uncertainty in the field including: the use and effectiveness of new technologies for prognostication, the appropriate pathway for the surveillance of patients following treatment for primary uveal melanoma, the use and effectiveness of new technologies in the treatment of hepatic recurrence and the use of systemic treatments. The guidelines were sent for international peer review and have been accredited by NICE. A summary of key recommendations is presented. The full documents are available on the Melanoma Focus website
Coherent matter wave inertial sensors for precision measurements in space
We analyze the advantages of using ultra-cold coherent sources of atoms for
matter-wave interferometry in space. We present a proof-of-principle experiment
that is based on an analysis of the results previously published in [Richard et
al., Phys. Rev. Lett., 91, 010405 (2003)] from which we extract the ratio h/m
for 87Rb. This measurement shows that a limitation in accuracy arises due to
atomic interactions within the Bose-Einstein condensate
The difference that tenure makes
This paper argues that housing tenures cannot be reduced to either production relations or consumption relations. Instead, they need to be understood as modes of housing distribution, and as having complex and dynamic relations with social classes. Building on a critique of both the productionist and the consumptionist literature, as well as of formalist accounts of the relations between tenure and class, the paper attempts to lay the foundations for a new theory of housing tenure. In order to do this, a new theory of class is articulated, which is then used to throw new light on the nature of class-tenure relations
Spinor condensates and light scattering from Bose-Einstein condensates
These notes discuss two aspects of the physics of atomic Bose-Einstein
condensates: optical properties and spinor condensates. The first topic
includes light scattering experiments which probe the excitations of a
condensate in both the free-particle and phonon regime. At higher light
intensity, a new form of superradiance and phase-coherent matter wave
amplification were observed. We also discuss properties of spinor condensates
and describe studies of ground--state spin domain structures and dynamical
studies which revealed metastable excited states and quantum tunneling.Comment: 58 pages, 33 figures, to appear in Proceedings of Les Houches 1999
Summer School, Session LXXI
Brans-Dicke corrections to the gravitational Sagnac effect
The {\it exact} formulation for the effect of the Brans-Dicke scalar field on
the gravitational corrections to the Sagnac delay in the Jordan and Einstein
frames is presented for the first time. The results completely agree with the
known PPN factors in the weak field region. The calculations also reveal how
the Brans-Dicke coupling parameter (appears in various correction terms for
different types of source/observer orbits. A first order correction of roughly
2.83 x 10^{-1} fringe shift for visible light is introduced by the
gravity-scalar field combination for Earth bound equatorial orbits. It is also
demonstrated that the final predictions in the two frames do not differ. The
effect of the scalar field on the geodetic and Lense-Thirring precession of a
spherical gyroscope in circular polar orbit around the Earth is also computed
with an eye towards the Stanford Gravity Probe-B experiment currently in
progress. The feasibility of optical and matter-wave interferometric
measurements is discussed briefly.Comment: 35 pages, 2 figures, pdf (from MSWord), accepted Physical Review D,
January 2001. (revised from June 25, 2000 version
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