27,334 research outputs found
From Wires to Cosmology
We provide a statistical framework for characterizing stochastic particle
production in the early universe via a precise correspondence to current
conduction in wires with impurities. Our approach is particularly useful when
the microphysics is uncertain and the dynamics are complex, but only
coarse-grained information is of interest. We study scenarios with multiple
interacting fields and derive the evolution of the particle occupation numbers
from a Fokker-Planck equation. At late times, the typical occupation numbers
grow exponentially which is the analog of Anderson localization for disordered
wires. Some statistical features of the occupation numbers show hints of
universality in the limit of a large number of interactions and/or a large
number of fields. For test cases, excellent agreement is found between our
analytic results and numerical simulations.Comment: v3: minor changes and references added; matches published version in
JCA
Relativistic dark matter at the Galactic center
In a large region of the supersymmetry parameter space, the annihilation
cross section for neutralino dark matter is strongly dependent on the relative
velocity of the incoming particles. We explore the consequences of this
velocity dependence in the context of indirect detection of dark matter from
the galactic center. We find that the increase in the annihilation cross
section at high velocities leads to a flattening of the halo density profile
near the galactic center and an enhancement of the annihilation signal.Comment: 13 pages, 9 figure
Prethermalization Production of Dark Matter
At the end of inflation, the inflaton field decays into an initially
nonthermal population of relativistic particles which eventually thermalize. We
consider the production of dark matter from this relativistic plasma, focusing
on the prethermal phase. We find that for a production cross section
with , the present dark matter abundance is produced
during the prethermal phase of its progenitors. For , entropy
production during reheating makes the nonthermal contribution to the present
dark matter abundance subdominant compared to that produced thermally. As
specific examples, we verify that the nonthermal contribution is irrelevant for
gravitino production in low scale supersymmetric models () and is dominant
for gravitino production in high scale supersymmetry models ().Comment: 12 pages, 4 figure
Characterising resistance to Turnip mosaic virus (TuMV) in Turnip (Brassica rapa rapa)
A Brassica rapa rapa L. line has been identified with high resistance to seven isolates of Turnip mosaic virus (TuMV) (including UK 1, CHN 5, CZE 1, CDN 1, GBR 6, POL 1 and UK 4) representing the major pathotypes of the virus. Resistant plants showed no symptoms following mechanical inoculation with TuMV and no virus was detected in the plants by ELISA. A cross was made between the rapid-cycling Brassica rapa line R-o-18 (which has been found to be susceptible to all the TuMV isolates) and a plant from the resistant B. rapa rapa line. The small amount of the F1 generation seed available from this cross has been grown and inoculated with the seven TuMV isolates. F1 plants were uniformly resistant to the UK 1 isolate of TuMV, uniformly susceptible to the CHN 5 isolate (only 2 plants inoculated) and segregated for resistance and susceptibility to the other five TuMV isolates. This suggested that the parent B. rapa rapa plant used in the cross was probably homozygous for one, or more dominant resistance genes to the UK 1 isolate of TuMV and heterozygous for one, or more dominant resistance genes to the other TuMV isolates. When self seed (S1) from the parent plant from the resistant line was inoculated with the TuMV isolates GBR 6 and UK 4, the segregation for the former isolate was not significantly different from 3 resistant to 1 susceptible, whereas for the latter isolate, the segregation was 4 resistant to 9 susceptible, suggesting resistance to GBR 6 is controlled by a single dominant gene, whereas resistance to UK 4 is controlled by two or more dominant resistance genes. The putative resistance genes appear to confer hitherto unknown dominant TuMV resistance specificities, and in combination have the exciting potential of providing durable resistance to TuMV
Probing early-universe phase transitions with CMB spectral distortions
Global, symmetry-breaking phase transitions in the early universe can
generate scaling seed networks which lead to metric perturbations. The acoustic
waves in the photon-baryon plasma sourced by these metric perturbations, when
Silk damped, generate spectral distortions of the cosmic microwave background
(CMB). In this work, the chemical potential distortion () due to scaling
seed networks is computed and the accompanying Compton -type distortion is
estimated. The specific model of choice is the nonlinear -model
for , but the results remain the same order of magnitude for other
scaling seeds. If CMB anisotropy constraints to the model are saturated,
the resulting chemical potential distortion .Comment: 17 pages, 6 figures, v2: References added, submitted to Phys. Rev.
Langmuir dark solitons in dense ultrarelativistic electron-positron gravito-plasma in pulsar magnetosphere
Nonlinear propagation of electrostatic modes in ultrarelativistic dense
elelectron-positron gravito-plasma at the polar cap region of pulsar
magnetosphere is considered. A nonlinear Schr\"{o}dinger equation is obtained
from the reductive perturbation method which predicts the existence of Langmuir
dark solitons. Relevance of the propagating dark solitons to the pulsar radio
emission is discussed.Comment: 6 pages, 7 figures. Accepted for publication in Astrophysics and
Space Science. arXiv admin note: text overlap with arXiv:astro-ph/9808047 by
other authors without attributio
- …