22,802 research outputs found
One-parameter scaling theory for DNA extension in a nanochannel
Experiments measuring DNA extension in nanochannels are at odds with even the
most basic predictions of current scaling arguments for the conformations of
confined semiflexible polymers such as DNA. We show that a theory based on a
weakly self-avoiding, one-dimensional "telegraph" process collapses
experimental data and simulation results onto a single master curve throughout
the experimentally relevant region of parameter space and explains the
mechanisms at play.Comment: Revised version. 5 pages, 4 figures, revised version, supplementary
informatio
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Monitoring Insect Parasites in a Cotton Pest Management Program
This item is part of the Agricultural Experiment Station archive. It was digitized from a physical copy provided by the University Libraries at the University of Arizona. For more information, please email CALS Publications at [email protected]
Area Decay Law Implementation for Quark String Fragmentation
We apply the Area Decay Law (ADL) straightforwardly to simulate a quark
string hadronization and compare the results with the explicit analytic
calculations. We show that the usual "inclusive" Monte--Carlo simulations do
not correspond to the ADL because of two mistakes: not proper simulation of
two--dimensional probability density and lack of an important combinatorial
factor in a binary tree simulation. We also show how to simulate area decay law
"inclusively" avoiding the above--mentioned mistakes.Comment: 5 pages (REVTEX) + 3 figures (available in ps format from
G.G.Leptoukh , IPGAS-HE/93-3, to be
published in Phys. Rev.
Evidence for Hydrodynamic Evolution in Proton-Proton Scattering at LHC Energies
In scattering at LHC energies, large numbers of elementary scatterings
will contribute significantly, and the corresponding high multiplicity events
will be of particular interest. Elementary scatterings are parton ladders,
identified with color flux-tubes. In high multiplicity events, many of these
flux tubes are produced in the same space region, creating high energy
densities. We argue that there are good reasons to employ the successful
procedure used for heavy ion collisions: matter is assumed to thermalizes
quickly, such that the energy from the flux-tubes can be taken as initial
condition for a hydrodynamic expansion. This scenario gets spectacular support
from very recent results on Bose-Einstein correlations in scattering at
900 GeV at LHC.Comment: 11 pages, 20 figure
Distillability and positivity of partial transposes in general quantum field systems
Criteria for distillability, and the property of having a positive partial
transpose, are introduced for states of general bipartite quantum systems. The
framework is sufficiently general to include systems with an infinite number of
degrees of freedom, including quantum fields. We show that a large number of
states in relativistic quantum field theory, including the vacuum state and
thermal equilibrium states, are distillable over subsystems separated by
arbitrary spacelike distances. These results apply to any quantum field model.
It will also be shown that these results can be generalized to quantum fields
in curved spacetime, leading to the conclusion that there is a large number of
quantum field states which are distillable over subsystems separated by an
event horizon.Comment: 25 pages, 2 figures. v2: Typos removed, references and comments
added. v3: Expanded introduction and reference list. To appear in Rev. Math.
Phy
The structure of classical extensions of quantum probability theory
On the basis of a suggestive definition of a classical extension of quantum mechanics in terms of statistical models, we prove that every such classical extension is essentially given by the so-called MisraâBugajski reduction map. We consider how this map enables one to understand quantum mechanics as a reduced classical statistical theory on the projective Hilbert space as phase space and discuss features of the induced hidden-variable model. Moreover, some relevant technical results on the topology and Borel structure of the projective Hilbert space are reviewed
On the origin of white dwarfs with carbon-dominated atmospheres: the case of H1504+65
We explore different evolutionary scenarios to explain the helium deficiency
observed in H1504+65, the most massive known PG1159 star. We concentrate mainly
on the possibility that this star could be the result of mass loss shortly
after the born-again and during the subsequent evolution through the [WCL]
stage. This possibility is sustained by recent observational evidence of
extensive mass-loss events in Sakurai's object and is in line with the recent
finding that such mass losses give rise to PG1159 models with thin helium-rich
envelopes and large rates of period change, as demanded by the pulsating star
PG1159-035. We compute the post born again evolution of massive sequences by
taking into account different mass-loss rate histories. Our results show that
stationary winds during the post-born-again evolution fail to remove completely
the helium-rich envelope so as to explain the helium deficiency observed in
H1504+65. Stationary winds during the Sakurai and [WCL] stages only remove at
most half of the envelope surviving the violent hydrogen burning during the
born-again phase. In view of our results, the recently suggested evolutionary
connection born-again stars --> H1504+65 --> white dwarfs with carbon-rich
atmospheres is difficult to sustain unless the whole helium-rich envelope could
be ejected by non-stationary mass-loss episodes during the Sakurai stage.Comment: 5 pages, 2 figures. To be published in Astronomy & Astrophysic
A Spitzer/IRAC Search for Substellar Companions of the Debris Disk Star epsilon Eridani
We have used the InfraRed Array Camera (IRAC) onboard the Spitzer Space
telescope to search for low mass companions of the nearby debris disk star
epsilon Eridani. The star was observed in two epochs 39 days apart, with
different focal plane rotation to allow the subtraction of the instrumental
Point Spread Function, achieving a maximum sensitivity of 0.01 MJy/sr at 3.6
and 4.5 um, and 0.05 MJy/sr at 5.8 and 8.0 um. This sensitivity is not
sufficient to directly detect scattered or thermal radiation from the epsilon
Eridani debris disk. It is however sufficient to allow the detection of Jovian
planets with mass as low as 1 MJ in the IRAC 4.5 um band. In this band, we
detected over 460 sources within the 5.70 arcmin field of view of our images.
To test if any of these sources could be a low mass companion to epsilon
Eridani, we have compared their colors and magnitudes with models and
photometry of low mass objects. Of the sources detected in at least two IRAC
bands, none fall into the range of mid-IR color and luminosity expected for
cool, 1 Gyr substellar and planetary mass companions of epsilon Eridani, as
determined by both models and observations of field M, L and T dwarf. We
identify three new sources which have detections at 4.5 um only, the lower
limit placed on their [3.6]-[4.5] color consistent with models of planetary
mass objects. Their nature cannot be established with the currently available
data and a new observation at a later epoch will be needed to measure their
proper motion, in order to determine if they are physically associated to
epsilon Eridani.Comment: 36 pages, to be published on The Astrophysical Journal, vol. 647,
August 200
Infrared studies of H II regions and dust clouds near K3 - 50
New ground-based infrared observations of the K3â50 region are reported at wavelengths between 2 and 34 ÎŒm, and at 1 mm. The main results are (a) that the visible nebula K3â50 is displaced from its infrared and radio counterparts, (b) that component C1 (the OH source ON-3) appears very faint at λ â©œ 20ÎŒmâ , and is therefore probably obscured by several hundred magnitudes of visual extinction, (c) that both K3â50 and component Care associated with separate condensations of molecular hydrogen, each of about 3000 Mâ, and (d) there are no strong sources in this region at 20 ÎŒm other than those associated with H II condensations
Infrared studies of H II regions and dust clouds near K3 - 50
New ground-based infrared observations of the K3â50 region are reported at wavelengths between 2 and 34 ÎŒm, and at 1 mm. The main results are (a) that the visible nebula K3â50 is displaced from its infrared and radio counterparts, (b) that component C1 (the OH source ON-3) appears very faint at λ â©œ 20ÎŒmâ , and is therefore probably obscured by several hundred magnitudes of visual extinction, (c) that both K3â50 and component Care associated with separate condensations of molecular hydrogen, each of about 3000 Mâ, and (d) there are no strong sources in this region at 20 ÎŒm other than those associated with H II condensations
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