4,524 research outputs found
Eccentric double white dwarfs as LISA sources in globular clusters
We consider the formation of double white dwarfs (DWDs) through dynamical
interactions in globular clusters. Such interactions can give rise to eccentric
DWDs, in contrast to the exclusively circular population expected to form in
the Galactic disk. We show that for a 5-year Laser Interferometer Space Antenna
(LISA) mission and distances as far as the Large Magellanic Cloud, multiple
harmonics from eccentric DWDs can be detected at a signal-to-noise ratio higher
than 8 for at least a handful of eccentric DWDs, given their formation rate and
typical lifetimes estimated from current cluster simulations. Consequently the
association of eccentricity with stellar-mass LISA sources does not uniquely
involve neutron stars, as is usually assumed. Due to the difficulty of
detecting (eccentric) DWDs with present and planned electromagnetic
observatories, LISA could provide unique dynamical identifications of these
systems in globular clusters.Comment: Published in ApJ 665, L5
Scattering of Noncommutative Waves and Solitons in a Supersymmetric Chiral Model in 2+1 Dimensions
Interactions of noncommutative waves and solitons in 2+1 dimensions can be
analyzed exactly for a supersymmetric and integrable U(n) chiral model
extending the Ward model. Using the Moyal-deformed dressing method in an
antichiral superspace, we construct explicit time-dependent solutions of its
noncommutative field equations by iteratively solving linear equations. The
approach is illustrated by presenting scattering configurations for two
noncommutative U(2) plane waves and for two noncommutative U(2) solitons as
well as by producing a noncommutative U(1) two-soliton bound state.Comment: 1+13 pages; v2: reference added, version published in JHE
Detrended fluctuation analysis as a statistical tool to monitor the climate
Detrended fluctuation analysis is used to investigate power law relationship
between the monthly averages of the maximum daily temperatures for different
locations in the western US. On the map created by the power law exponents, we
can distinguish different geographical regions with different power law
exponents. When the power law exponents obtained from the detrended fluctuation
analysis are plotted versus the standard deviation of the temperature
fluctuations, we observe different data points belonging to the different
climates, hence indicating that by observing the long-time trends in the
fluctuations of temperature we can distinguish between different climates.Comment: 8 pages, 4 figures, submitted to JSTA
Russian Amino Chelate Fertilizers of Agrovin Type Applied on White Cabbage
When applying synthetic chelate fertilizers, the plant ”takes away” only the element of nutrition, and the chelator (as a foreign element, ballast) gets into the soil, where over time, accumulating, creates negative environmental consequences. The use of amino acids in foliar fertilizers is one of the most promising ways to eliminate the impact of harmful environmental conditions on agricultural plants. In addition, consumers have recently been very interested in organic food and have been demanding quality and food safety. Translocation of amino acids takes place both in the phloem and in the xylem, which helps to dispose of nitrogen in the roots and above-ground part of the plant and accelerates the retransmission of nutrients in plants, in particular, fixed elements. The absorption rate of amino acids depends on the biological characteristics of the plants and the characteristics of the amino acids. The research is aimed at determining the influence of leaf fertilizing with amino chelate fertilizers of the Agrovin series on the growth, development and yield of white cabbage
Scaling in the Bombay Stock Exchange Index
In this paper we study BSE Index financial time series for fractal and
multifractal behaviour. We show that Bombay stock Exchange (BSE)Index time
series is mono-fractal and can be represented by a fractional Brownian motion.Comment: 11 pages,3 figure
Self-Duality in D <= 8-dimensional Euclidean Gravity
In the context of D-dimensional Euclidean gravity, we define the natural
generalisation to D-dimensions of the self-dual Yang-Mills equations, as
duality conditions on the curvature 2-form of a Riemannian manifold. Solutions
to these self-duality equations are provided by manifolds of SU(2), SU(3), G_2
and Spin(7) holonomy. The equations in eight dimensions are a master set for
those in lower dimensions. By considering gauge fields propagating on these
self-dual manifolds and embedding the spin connection in the gauge connection,
solutions to the D-dimensional equations for self-dual Yang-Mills fields are
found. We show that the Yang-Mills action on such manifolds is topologically
bounded from below, with the bound saturated precisely when the Yang-Mills
field is self-dual. These results have a natural interpretation in
supersymmetric string theory.Comment: 9 pages, Latex, factors in eqn. (6) corrected, acknowledgement and
reference added, typos fixe
Supernova Ia: a Converging Delayed Detonation Wave
A model of a carbon-oxygen (C--O) presupernova core with an initial mass 1.33
M_\odot, an initial carbon mass fraction 0.27, and with an average mass
growth-rate 5 x 10^{-7} M_\odot/yr due to accretion in a binary system was
evolved from initial central density 10^9 g/cm^3, and temperature 2.05 x 10^8 K
through convective core formation and its subsequent expansion to the carbon
runaway at the center. The only thermonuclear reaction contained in the
equations of evolution and runaway was the carbon burning reaction 12C + 12C
with an energy release corresponding to the full transition of carbon and
oxygen (with the same rate as carbon) into 56Ni. As a parameter we take
\alpha_c - a ratio of a mixing length to the size of the convective zone. In
spite of the crude assumptions, we obtained a pattern of the runaway acceptable
for the supernova theory with the strong dependence of its duration on
\alpha_c. In the variants with large enough values of \alpha_c=4.0 x 10^{-3}
and 3.0 x 10^{-3} the fuel combustion occurred from the very beginning as a
prompt detonation. In the range of 2.0 x 10^{-3} >= \alpha_c >= 3.0 x 10^{-4}
the burning started as a deflagration with excitation of stellar pulsations
with growing amplitude. Eventually, the detonation set in, which was activated
near the surface layers of the presupernova (with m about 1.33 M_\odot) and
penetrated into the star down to the deflagration front. Excitation of model
pulsations and formation of a detonation front are described in detail for the
variant with \alpha_c=1.0 x 10^{-3}.Comment: 13 pages, 11 figures, to appear in Astronomy Letter
Yang-Mills instantons and dyons on homogeneous G_2-manifolds
We consider Lie G-valued Yang-Mills fields on the space R x G/H, where G/H is
a compact nearly K"ahler six-dimensional homogeneous space, and the manifold R
x G/H carries a G_2-structure. After imposing a general G-invariance condition,
Yang-Mills theory with torsion on R x G/H is reduced to Newtonian mechanics of
a particle moving in R^6, R^4 or R^2 under the influence of an inverted
double-well-type potential for the cases G/H = SU(3)/U(1)xU(1),
Sp(2)/Sp(1)xU(1) or G_2/SU(3), respectively. We analyze all critical points and
present analytical and numerical kink- and bounce-type solutions, which yield
G-invariant instanton configurations on those cosets. Periodic solutions on S^1
x G/H and dyons on iR x G/H are also given.Comment: 1+26 pages, 14 figures, 6 miniplot
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