50,752 research outputs found
Vibrations and stresses in layered anisotropic cylinders
An equation describing the radial displacement in a k layered anisotropic cylinder was obtained. The cylinders are initially unstressed but are subjected to either a time dependent normal stress or a displacement at the external boundaries of the laminate. The solution is obtained by utilizing the Vodicka orthogonalization technique. Numerical examples are given to illustrate the procedure
A transport coefficient: the electrical conductivity
I describe the lattice determination of the electrical conductivity of the
quark gluon plasma. Since this is the first extraction of a transport
coefficient with a degree of control over errors, I next use this to make
estimates of other transport related quantities using simple kinetic theory
formulae. The resulting estimates are applied to fluctuations, ultra-soft
photon spectra and the viscosity. Dimming of ultra-soft photons is exponential
in the mean free path, and hence is a very sensitive probe of transport.Comment: Talk given in ICPAQGP 2005, SINP, Kolkat
Fe and N self-diffusion in non-magnetic Fe:N
Fe and N self-diffusion in non-magnetic FeN has been studied using neutron
reflectivity. The isotope labelled multilayers, FeN/57Fe:N and Fe:N/Fe:15N were
prepared using magnetron sputtering. It was remarkable to observe that N
diffusion was slower compared to Fe while the atomic size of Fe is larger
compared to N. An attempt has been made to understand the diffusion of Fe and N
in non-magnetic Fe:N
Laser-assisted solar cell metallization processing
Laser-assisted processing techniques for producing high-quality solar cell metallization patterns are being investigated, developed, and characterized. The tasks comprising these investigations are outlined
The Chern-Simons Source as a Conformal Family and Its Vertex Operators
In a previous work, a straightforward canonical approach to the source-free
quantum Chern-Simons dynamics was developed. It makes use of neither gauge
conditions nor functional integrals and needs only ideas known from QCD and
quantum gravity. It gives Witten's conformal edge states in a simple way when
the spatial slice is a disc. Here we extend the formalism by including sources
as well. The quantum states of a source with a fixed spatial location are shown
to be those of a conformal family, a result also discovered first by Witten.
The internal states of a source are not thus associated with just a single ray
of a Hilbert space. Vertex operators for both abelian and nonabelian sources
are constructed. The regularized abelian Wilson line is proved to be a vertex
operator. We also argue in favor of a similar nonabelian result. The
spin-statistics theorem is established for Chern-Simons dynamics even though
the sources are not described by relativistic quantum fields. The proof employs
geometrical methods which we find are strikingly transparent and pleasing. It
is based on the research of European physicists about ``fields localized on
cones.'
2+1 Einstein Gravity as a Deformed Chern-Simons Theory
The usual description of 2+1 dimensional Einstein gravity as a Chern-Simons
(CS) theory is extended to a one parameter family of descriptions of 2+1
Einstein gravity. This is done by replacing the Poincare' gauge group symmetry
by a q-deformed Poincare' gauge group symmetry, with the former recovered when
q-> 1. As a result, we obtain a one parameter family of Hamiltonian
formulations for 2+1 gravity. Although formulated in terms of noncommuting
dreibeins and spin-connection fields, our expression for the action and our
field equations, appropriately ordered, are identical in form to the ordinary
ones. Moreover, starting with a properly defined metric tensor, the usual
metric theory can be built; the Christoffel symbols and space-time curvature
having the usual expressions in terms of the metric tensor, and being
represented by c-numbers. In this article, we also couple the theory to
particle sources, and find that these sources carry exotic angular momentum.
Finally, problems related to the introduction of a cosmological constant are
discussed.Comment: Latex file, 26 pages, no figure
Characterization and comparative evaluation of novel planar electromagnetic sensors
The characterization of three types of novel planar electromagnetic sensors: 1) meander; 2) mesh; and 3) interdigital configuration, has been studied and their comparative performance has been evaluated based on their areas of applications. All of them are suitable for inspection and evaluation of system properties without destroying them. The experiments on fabricated sensors have been conducted and the results are presented here. The target application is to use a mixture of different types of sensors to detect plasti
Staggered fermion matrix elements using smeared operators
We investigate the use of two kinds of staggered fermion operators, smeared
and unsmeared. The smeared operators extend over a hypercube, and tend to
have smaller perturbative corrections than the corresponding unsmeared
operators. We use these operators to calculate kaon weak matrix elements on
quenched ensembles at , 6.2 and 6.4. Extrapolating to the continuum
limit, we find . The
systematic error is dominated by the uncertainty in the matching between
lattice and continuum operators due to the truncation of perturbation theory at
one-loop. We do not include any estimate of the errors due to quenching or to
the use of degenerate and quarks. For the
electromagnetic penguin operators we find
and . We also use the ratio of unsmeared to
smeared operators to make a partially non-perturbative estimate of the
renormalization of the quark mass for staggered fermions. We find that tadpole
improved perturbation theory works well if the coupling is chosen to be
\alpha_\MSbar(q^*=1/a).Comment: 22 pages, 1 figure, uses eps
Detecting cold gas at intermediate redshifts: GMRT survey using Mg II systems
Intervening HI 21-cm absorption systems at z > 1.0 are very rare and only 4
confirmed detections have been reported in the literature. Despite their
scarcity, they provide interesting and unique insights into the physical
conditions in the interstellar medium of high-z galaxies. Moreover, they can
provide independent constraints on the variation of fundamental constants. We
report 3 new detections based on our ongoing Giant Metrewave Radio Telescope
(GMRT) survey for 21-cm absorbers at 1.10< z_abs< 1.45 from candidate damped
Lyman_alpha systems. The 21-cm lines are narrow for the z_abs = 1.3710 system
towards SDSS J0108-0037 and z_abs = 1.1726 system toward SDSS J2358-1020. Based
on line full-width at half maximum, the kinetic temperatures are <= 5200 K and
<=800 K, respectively. The 21-cm absorption profile of the third system, z_abs
=1.1908 system towards SDSS J0804+3012, is shallow, broad and complex,
extending up to 100 km/s. The centroids of the 21-cm lines are found to be
shifted with respect to the corresponding centroids of the metal lines derived
from SDSS spectra. This may mean that the 21-cm absorption is not associated
with the strongest metal line component.Comment: 13 pages with 5 figures. Accepted for publication in ApJ
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