14,514 research outputs found
Midcourse navigation using statistical filter theory, a manual theodolite, and symbolic computer control
Midcourse navigation using statistical filter theory, manual theodolite, and symbolic computer control applied to manned spacecraf
Study of bonding between glass and plastic in glass-reinforced plastics - Extended work Quarterly progress report, 1 Jan. - 31 Mar. 1967
Procedures for fluorination and alkylation of glass fabric for subsequent use in production of laminate
A study of bonding between glass and plastic in glass-reinforced plastics, phase 3 Summary technical report no. 3, 31 Mar. 1966 - 15 Jul. 1967
Mechanical properties of chemical bonding between glass fibers and resin matri
Casimir energy density in closed hyperbolic universes
The original Casimir effect results from the difference in the vacuum
energies of the electromagnetic field, between that in a region of space with
boundary conditions and that in the same region without boundary conditions. In
this paper we develop the theory of a similar situation, involving a scalar
field in spacetimes with compact spatial sections of negative spatial
curvature.Comment: 10 pages. Contribution to the "Fifth Alexander Friedmann
International Seminar on Gravitation and Cosmology," Joao Pessoa, Brazil,
2002. Revised version, with altered Abstract and one new referenc
Hawking Radiation for Non-minimally Coupled Matter from Generalized 2D Black Hole Models
It is well known that spherically symmetric reduction of General Relativity
(SSG) leads to non-minimally coupled scalar matter. We generalize (and correct)
recent results to Hawking radiation for a class of dilaton models which share
with the Schwarzschild black hole non-minimal coupling of scalar fields and the
basic global structure. An inherent ambiguity of such models (if they differ
from SSG) is discussed. However, for SSG we obtain the rather disquieting
result of a negative Hawking flux at infinity, if the usual recipe for such
calculations is applied.Comment: 8 page
Scaling of cluster heterogeneity in percolation transitions
We investigate a critical scaling law for the cluster heterogeneity in
site and bond percolations in -dimensional lattices with . The
cluster heterogeneity is defined as the number of distinct cluster sizes. As an
occupation probability increases, the cluster size distribution evolves
from a monodisperse distribution to a polydisperse one in the subcritical
phase, and back to a monodisperse one in the supercritical phase. We show
analytically that diverges algebraically approaching the percolation
critical point as with the critical exponent
associated with the characteristic cluster size. Interestingly, its
finite-size-scaling behavior is governed by a new exponent where is the fractal dimension of the critical percolating
cluster and is the correlation length exponent. The corresponding scaling
variable defines a singular path to the critical point. All results are
confirmed by numerical simulations.Comment: 4 pages, 4 figure
Magnetic polarizability of hadrons from lattice QCD in the background field method
We present a calculation of hadron magnetic polarizability using the
techniques of lattice QCD. This is carried out by introducing a uniform
external magnetic field on the lattice and measuring the quadratic part of a
hadron's mass shift. The calculation is performed on a lattice with
standard Wilson actions at beta=6.0 (spacing fm) and pion mass down to
about 500 MeV. Results are obtained for 30 particles covering the entire baryon
octet (, , , , , , ,
) and decuplet (, , , ,
, , , , ,
), plus selected mesons (, , , , ,
, , , , , , ). The
results are compared with available values from experiments and other
theoretical calculations.Comment: 30 pages, 23 figures, 5 table
High-precision abundances of elements in Kepler LEGACY stars. Verification of trends with stellar age
HARPS-N spectra with S/N > 250 and MARCS model atmospheres were used to
derive abundances of C, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, and Y in ten
stars from the Kepler LEGACY sample (including the binary pair 16 Cyg A and B)
selected to have metallicities in the range -0.15 < [Fe/H] < +0.15 and ages
between 1 and 7 Gyr. Stellar gravities were obtained from seismic data and
effective temperatures were determined by comparing non-LTE iron abundances
derived from FeI and FeII lines. Available non-LTE corrections were also
applied when deriving abundances of the other elements. The results support the
[X/Fe]-age relations previously found for solar twins. [Mg/Fe], [Al/Fe], and
[Zn/Fe] decrease by ~0.1 dex over the lifetime of the Galactic thin disk due to
delayed contribution of iron from Type Ia supernovae relative to prompt
production of Mg, Al, and Zn in Type II supernovae. [Y/Mg] and [Y/Al], on the
other hand, increase by ~0.3 dex, which can be explained by an increasing
contribution of s-process elements from low-mass AGB stars as time goes on. The
trends of [C/Fe] and [O/Fe] are more complicated due to variations of the ratio
between refractory and volatile elements among stars of similar age. Two stars
with about the same age as the Sun show very different trends of [X/H] as a
function of elemental condensation temperature Tc and for 16 Cyg, the two
components have an abundance difference, which increases with Tc. These
anomalies may be connected to planet-star interactions.Comment: 13 pages with 7 figures. Accepted for publication in A&
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