373,466 research outputs found
The magnetic field generated by an electron bound in angular-momentum eigenstates
The magnetic field generated by an electron bound in a spherically symmetric
potential is calculated for eigenstates of the orbital and total angular
momentum. General expressions are presented for the current density in such
states and the magnetic field is calculated through the vector potential, which
is obtained from the current density by direct integration. The method is
applied to the hydrogen atom, for which we reproduce and extend known results.Comment: This article is a long version of our article which will appear in
Eur. J.phys.20. It contains 22 pages 3 figure
High-velocity gas towards the LMC resides in the Milky Way halo
To explore the origin of high-velocity gas in the direction of the Large
Magellanic Cloud (LMC) we analyze absorption lines in the ultraviolet spectrum
of a Galactic halo star that is located in front of the LMC at d=9.2 kpc
distance. We study the velocity-component structure of low and intermediate
metal ions in the spectrum of RXJ0439.8-6809, as obtained with the Cosmic
Origins Spectrograph (COS) onboard HST, and measure equivalent widths and
column densities for these ions. We supplement our COS data with a
Far-Ultraviolet Spectroscopic Explorer spectrum of the nearby LMC star Sk-69 59
and with HI 21cm data from the Leiden-Argentina-Bonn (LAB) survey. Metal
absorption towards RXJ0439.8-6809 is unambiguously detected in three different
velocity components near v_LSR=0,+60, and +150 km/s. The presence of absorption
proves that all three gas components are situated in front of the star, thus
being located in the disk and inner halo of the Milky Way. For the
high-velocity cloud (HVC) at v_LSR=+150 km/s we derive an oxygen abundance of
[O/H]=-0.63 (~0.2 solar) from the neighbouring Sk-69 59 sightline, in
accordance with previous abundance measurements for this HVC. From the observed
kinematics we infer that the HVC hardly participates in the Galactic rotation.
Our study shows that the HVC towards the LMC represents a Milky Way halo cloud
that traces low-column density gas with relatively low metallicity. It rules
out scenarios in which the HVC represents material close to the LMC that stems
from a LMC outflow.Comment: 4 pages, 3 figures; submitted to A&A Letter
Continuous-feed nanocasting process for the synthesis of bismuth nanowire composites
We present a novel, continuous-feed nanocasting procedure for the synthesis
of bismuth nanowire structures embedded in the pores of a mesoporous silica
template. The immobilization of a bismuth salt inside the silica template from
a diluted metal salt solution yields a sufficiently high loading to obtain
electrically conducting bulk nanowire composite samples after reduction and
sintering the nanocomposite powders. Electrical resistivity measurements of
sintered bismuth nanowires embedded in the silica template reveal
size-quantization effects
Magnetic vortex in color-flavor locked quark matter
Within Ginzburg-Landau theory, we study the structure of a magnetic vortex in
color-flavor locked quark matter. This vortex is characterized by winding of
the SU(3) phase in color-flavor space, as well as by the presence of a
color-flavor unlocked condensate in the core. We estimate the upper and lower
critical fields and the critical Ginzburg-Landau parameter that distinguishes
between type I and type II superconductors.Comment: 8 pages, 1 figur
Prototyping Virtual Data Technologies in ATLAS Data Challenge 1 Production
For efficiency of the large production tasks distributed worldwide, it is
essential to provide shared production management tools comprised of
integratable and interoperable services. To enhance the ATLAS DC1 production
toolkit, we introduced and tested a Virtual Data services component. For each
major data transformation step identified in the ATLAS data processing pipeline
(event generation, detector simulation, background pile-up and digitization,
etc) the Virtual Data Cookbook (VDC) catalogue encapsulates the specific data
transformation knowledge and the validated parameters settings that must be
provided before the data transformation invocation. To provide for local-remote
transparency during DC1 production, the VDC database server delivered in a
controlled way both the validated production parameters and the templated
production recipes for thousands of the event generation and detector
simulation jobs around the world, simplifying the production management
solutions.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 5 pages, 3 figures, pdf. PSN TUCP01
Sp(2)-Symmetric Lagrangian BRST Quantization
One Lagrangian BRST quantization principle is that of imposing correct
Schwinger-Dyson equations through the BRST Ward identities. In this paper we
show how to derive the analogous -symmetric quantization condition in
flat coordinates from an underlying -symmetric Schwinger-Dyson BRST
symmetry. We also show under what conditions this can be recast in the language
of triplectic quantization.Comment: LaTeX, 19 page
Dependence of spin susceptibility of a two-dimensional electron system on the valley degree of freedom
We report measurements of the spin susceptibility, ,
in an AlAs two-dimensional electron system where, via the application of
in-plane stress, we transfer electrons from one conduction-band valley to
another ( is the valley degeneracy, and and are the electron
effective mass and g-factor). At a given density, when the two valleys are
equally populated (), the measured is smaller than when only
one valley is occupied (). This observation counters the common
assumption that a two-valley two-dimensional system is effectively more dilute
than a single-valley system because of its smaller Fermi energy.Comment: 4 pages, 3 figure
Phase transitions of nematic rubbers
Single crystal nematic elastomers undergo a transition from a strongly
ordered phase N to an "isotropic" phase I. We show that: (a) samples produced
under tension by the Finkelmann procedure are intrinsically anisotropic and
should show a small (temperature dependent) birefringence in the high
temperature I phase. (b) for the I->Ntransition via cooling there is a spinodal
limit but for the N->I transition via heating there is no soft mode at the
standard spinodal temperature. (c) the N->I transition is reminiscent of a
martensitic transformation: nucleation of the I phase should occur in the form
of platelets, making a well defined angle with the director.Comment: 7 pages, 3 figures (To appear in Europhys. Lett.
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