11,932 research outputs found
The Hamilton-Waterloo Problem with even cycle lengths
The Hamilton-Waterloo Problem HWP asks for a
2-factorization of the complete graph or , the complete graph with
the edges of a 1-factor removed, into -factors and
-factors, where . In the case that and are both
even, the problem has been solved except possibly when
or when and are both odd, in which case necessarily . In this paper, we develop a new construction that creates
factorizations with larger cycles from existing factorizations under certain
conditions. This construction enables us to show that there is a solution to
HWP for odd and whenever the obvious
necessary conditions hold, except possibly if ; and
; ; or . This result almost completely
settles the existence problem for even cycles, other than the possible
exceptions noted above
Three undescribed pathogenic Phytophthora taxa from the south-west of Western Australia
The Phytophthora culture collection of the Vegetation Health Service of the Department of Environment and Conservation of Western Australia (WA) has been re-evaluated using DNA sequencing (Burgess et al., 2009). This has revealed many undescribed taxa previously classified as known morpho-species, one of which has recently been described as P. multivora (Scott et al., 2009).
The aim of this study was to describe three of these taxa, all of which occur in WA native ecosystems. They were compared with both the morphological species to which they are most similar and their closest phylogenetic relatives. In addition, the pathogenicity of these taxa was assessed in glasshouse trials
Coriolis force corrections to g-mode spectrum in 1D MHD model
The corrections to g-mode frequencies caused by the presence of a central
magnetic field and rotation of the Sun are calculated. The calculations are
carried out in the simple one dimensional magnetohydrodynamical model using the
approximations which allow one to find the purely analytical spectra of
magneto-gravity waves beyond the scope of the JWKB approximation and avoid in a
small background magnetic field the appearance of the cusp resonance which
locks a wave within the radiative zone. These analytic results are compared
with the satellite observations of the g-mode frequency shifts which are of the
order one per cent as given in the GOLF experiment at the SoHO board. The main
contribution turns out to be the magnetic frequency shift in the strong
magnetic field which obeys the used approximations. In particular, the fixed
magnetic field strength 700 KG results in the mentioned value of the frequency
shift for the g-mode of the radial order n=-10. The rotational shift due to the
Coriolis force appears to be small and does not exceed a fracton of per cent,
\alpha_\Omega < 0.003.Comment: RevTeX4, 9 pages, 4 eps figures; accepted for publication in
Astronomy Reports (Astronomicheskii Zhurnal
Location and Direction Dependent Effects in Collider Physics from Noncommutativity
We examine the leading order noncommutative corrections to the differential
and total cross sections for e+ e- --> q q-bar. After averaging over the
earth's rotation, the results depend on the latitude for the collider, as well
as the direction of the incoming beam. They also depend on scale and direction
of the noncommutativity. Using data from LEP, we exclude regions in the
parameter space spanned by the noncommutative scale and angle relative to the
earth's axis. We also investigate possible implications for phenomenology at
the future International Linear Collider.Comment: version to appear in PR
Cosmology and two-body problem of D-branes
In this paper, we investigate the dynamics and the evolution of the scale
factor of a probe Dp-brane which move in the background of source Dp-branes.
Action of the probe brane is described by the Born-Infeld action and the
interaction with the background R-R field. When the probe brane moves away from
the source branes, it expands by power law, whose index depends on the
dimension of the brane. If the energy density of the gauge field on the brane
is subdominant, the expansion is decelerating irrespective of the dimension of
the brane. On the other hand, when the probe brane is a Nambu-Goto brane, the
energy density of the gauge field can be dominant, in which case accelerating
expansion occurs for . The accelerating expansion stops when the
brane has expanded sufficiently so that the energy density of the gauge field
become subdominant.Comment: 6 pages, 7 figures, reference added, accepted for publication in PR
Neural signatures of strategic types in a two-person bargaining game
The management and manipulation of our own social image in the minds of others requires difficult and poorly understood computations. One computation useful in social image management is strategic deception: our ability and willingness to manipulate other people's beliefs about ourselves for gain. We used an interpersonal bargaining game to probe the capacity of players to manage their partner's beliefs about them. This probe parsed the group of subjects into three behavioral types according to their revealed level of strategic deception; these types were also distinguished by neural data measured during the game. The most deceptive subjects emitted behavioral signals that mimicked a more benign behavioral type, and their brains showed differential activation in right dorsolateral prefrontal cortex and left Brodmann area 10 at the time of this deception. In addition, strategic types showed a significant correlation between activation in the right temporoparietal junction and expected payoff that was absent in the other groups. The neurobehavioral types identified by the game raise the possibility of identifying quantitative biomarkers for the capacity to manipulate and maintain a social image in another person's mind
Rydberg atom formation in strongly correlated ultracold plasmas
In plasmas at very low temperatures formation of neutral atoms is dominated
by collisional three-body recombination, owing to the strong ~ T^(-9/2) scaling
of the corresponding recombination rate with the electron temperature T. While
this law is well established at high temperatures, the unphysical divergence as
T -> 0 clearly suggest a breakdown in the low-temperature regime. Here, we
present a combined molecular dynamics-Monte-Carlo study of electron-ion
recombination over a wide range of temperatures and densities. Our results
reproduce the known behavior of the recombination rate at high temperatures,
but reveal significant deviations with decreasing temperature. We discuss the
fate of the kinetic bottleneck and resolve the divergence-problem as the plasma
enters the ultracold, strongly coupled domain.Comment: 11 pages, 10 figure
On non-perturbative corrections to the Kahler potential
We present the results of a detailed investigation into the consequences of
adding specific string motivated non-perturbative corrections to the usual tree
level Kahler potential in dilaton dominated scenarios. The success of the model
is judged through our ability to obtain a realistic VEV for the dilaton < Re S
> ~ 2, corresponding to the true minima of the scalar potential and being
associated with a reasonable value for the SUSY breaking scale via the
gravitino mass. The status of the so-called moduli problem is also reviewed in
each of the ansatze studied. Those include previous proposals made in the
context of both the chiral and the linear multiplet formalisms to describe
gaugino condensation, and a new ansatz which shows explicitly the equivalence
between the two.Comment: 11 pages, LaTex, uses psfig.sty with 4 figure
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