65,230 research outputs found
Atomic screening of nuclear transitions
In the analysis of time-reversal and Mössbauer absorption experiments, it is important to consider atomic processes which interfere with the direct nuclear transition. Interaction of the photon with the atomic electrons causes the radiation to acquire a phase shift, specified by the interference parameter ξ(L_π). We present theoretical expressions for ξ and compare our calculated values with experiment. Satisfactory agreement is obtained. In particular, an apparent violation of time-reversal invariance in the 129-keV transition of ^(191)Ir is fully explained by these effects
Integrity bases for local invariants of composite quantum systems
Unitary group branchings appropriate to the calculation of local invariants
of density matrices of composite quantum systems are formulated using the
method of -function plethysms. From this, the generating function for the
number of invariants at each degree in the density matrix can be computed. For
the case of two two-level systems the generating function is . Factorisation of such series leads
in principle to the identification of an integrity basis of algebraically
independent invariants. This note replaces Appendix B of our paper\cite{us} J
Phys {\bf A33} (2000) 1895-1914 (\texttt{quant-ph/0001076}) which is incorrect.Comment: Latex, 4 pages, correcting Appendix B of quant-ph/0001076 Error in
corrected and conclusions modified accordingl
Superfluid Phase Stability of He in Axially Anisotropic Aerogel
Measurements of superfluid He in 98% aerogel demonstrate the existence of
a metastable \emph{A}-like phase and a stable \emph{B}-like phase. It has been
suggested that the relative stability of these two phases is controlled by
anisotropic quasiparticle scattering in the aerogel. Anisotropic scattering
produced by axial compression of the aerogel has been predicted to stabilize
the axial state of superfluid He. To explore this possiblity, we used
transverse acoustic impedance to map out the phase diagram of superfluid He
in a % porous silica aerogel subjected to 17% axial compression. We
have previously shown that axial anisotropy in aerogel leads to optical
birefringence and that optical cross-polarization studies can be used to
characterize such anisotropy. Consequently, we have performed optical
cross-polarization experiments to verify the presence and uniformity of the
axial anisotropy in our aerogel sample. We find that uniform axial anisotropy
introduced by 17% compression does not stabilize the \emph{A}-like phase. We
also find an increase in the supercooling of the \emph{A}-like phase at lower
pressure, indicating a modification to \emph{B}-like phase nucleation in
\emph{globally} anisotropic aerogels.Comment: 4 pages, 4 figures, submitted to LT25 (25th International Conference
on Low Temperature Physics
Research program to develop a technology improvement program for closed die forging Final report
Upset forging tests on aluminum and titanium alloys and maraging steel using high temperature die
Cosmic Strings, Zero Modes and SUSY breaking in Nonabelian N=1 Gauge Theories
We investigate the microphysics of cosmic strings in Nonabelian gauge
theories with N=1 supersymmetry. We give the vortex solutions in a specific
example and demonstrate that fermionic superconductivity arises because of the
couplings and interactions dictated by supersymmetry. We then use supersymmetry
transformations to obtain the relevant fermionic zero modes and investigate the
role of soft supersymmetry breaking on the existence and properties of the
superconducting strings.Comment: 12 pages, RevTex, submitted to Phys. Rev.
Interaction of a two-dimensional strip boundary layer with a three-dimensional transonic swept-wing code
A 3D inviscid transonic analysis code was combined with a 2D strip integral boundary layer technique to form an approximate interaction procedure for analyzing the flow over a high aspect ratio wing near cruise conditions. Converged results obtained using the procedure for an aspect ratio 10.3 supercritical wing are discussed. Angle of attack adjustments were made during the iterative procedure in order to compensate for the viscous lift loss. A comparison of the calculations with experimental data is presented
Ambient Atmospheric Hydrocarbon Content as Determined by Gas Chromatographic Techniques from Rural Tidewater Virginia in Late Spring 1974
In an attempt to ascertain the naturally generated hydrocarbon contribution to the air quality of the Hampton Roads region of Tidewater Virginia, a series of 27 air samples was obtained in two rural locations during late spring of 1974. These samples were analyzed for their hydrocarbon content (carbon number range C5 to C10) using gas chromatographic techniques. The thirty different hydrocarbon species were identified and monitored in the experiment. Preliminary analysis of the data indicates an average concentration of 397 parts per billion by weight (carbon) for the total non-methane hydrocarbon loading for C5 to C10 during the experiment. This value exceeds the National Primary Air Quality Standards as set by the Environmental Protection Agency
The Dual Formulation of Cosmic Strings and Vortices
We study four dimensional systems of global, axionic and local strings. By
using the path integral formalism, we derive the dual formulation of these
systems, where Goldstone bosons, axions and missive vector bosons are described
by antisymmetric tensor fields, and strings appear as a source for these tensor
fields. We show also how magnetic monopoles attached to local strings are
described in the dual formulation. We conclude with some remarks.Comment: 18 pages, CU-TP-588 and CERN-TH.6780/9
Nanoscale Torsional Optomechanics
Optomechanical transduction is demonstrated for nanoscale torsional
resonators evanescently coupled to optical microdisk whispering gallery mode
resonators. The on-chip, integrated devices are measured using a fully
fiber-based system, including a tapered and dimpled optical fiber probe. With a
thermomechanically calibrated optomechanical noise floor down to 7 fm/sqrt(Hz),
these devices open the door for a wide range of physical measurements involving
extremely small torques, as little as 4x10^-20 N*m.Comment: 4 pages, 4 figures - Accepted to APL Oct 22nd, 2012. To appear in
February 4th issue - as cover articl
Magneto-Acoustic Spectroscopy in Superfluid 3He-B
We have used the recently discovered acoustic Faraday effect in superfluid
3He to perform high resolution spectroscopy of an excited state of the
superfluid condensate. With acoustic cavity interferometry we measure the
rotation of the plane of polarization of a transverse sound wave propagating in
the direction of magnetic field from which we determine the Zeeman energy of
the excited state. We interpret the Lande g-factor, combined with the
zero-field energies of the state, using the theory of Sauls and Serene to
calculate the strength of f -wave interactions in 3He.Comment: 4 pages, 5 figures, submitted to PRL, Aug 30th, 200
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