8,762 research outputs found
RUSSIAN FARM ENTERPRISE PERFORMANCE AND RESTRUCTURING: A DEBT PROBLEM OR A PROFITABILITY PROBLEM?
Farm Management,
Observation of Cosmic Acceleration and Determining the Fate of the Universe
Current observations of Type Ia supernovae provide evidence for cosmic
acceleration out to a redshift of z \lsim 1, leading to the possibility that
the universe is entering an inflationary epoch. However, inflation can take
place only if vacuum-energy (or other sufficiently slowly redshifting source of
energy density) dominates the energy density of a region of physical radius
1/H. We argue that for the best-fit values of and
inferred from the supernovae data, one must confirm cosmic acceleration out to
at least to infer that the universe is inflating.Comment: 4 pages;important changes in conclusion; published in Phys. Rev. Let
Dynamics of Polymers: a Mean-Field Theory
We derive a general mean-field theory of inhomogeneous polymer dynamics; a
theory whose form has been speculated and widely applied, but not heretofore
derived. Our approach involves a functional integral representation of a
Martin-Siggia-Rose type description of the exact many-chain dynamics. A saddle
point approximation to the generating functional, involving conditions where
the MSR action is stationary with respect to a collective density field
and a conjugate MSR response field , produces the desired dynamical
mean-field theory. Besides clarifying the proper structure of mean-field theory
out of equilibrium, our results have implications for numerical studies of
polymer dynamics involving hybrid particle-field simulation techniques such as
the single-chain in mean-field method (SCMF)
Ocular attention-sensing interface system
The purpose of the research was to develop an innovative human-computer interface based on eye movement and voice control. By eliminating a manual interface (keyboard, joystick, etc.), OASIS provides a control mechanism that is natural, efficient, accurate, and low in workload
Zero modes on cosmic strings in an external magnetic field
A classical analysis suggests that an external magnetic field can cause
trajectories of charge carriers on a superconducting domain wall or cosmic
string to bend, thus expelling charge carriers with energy above the mass
threshold into the bulk. We study this process by solving the Dirac equation
for a fermion of mass and charge , in the background of a domain wall
and a magnetic field of strength . We find that the modes of the charge
carriers get shifted into the bulk, in agreement with classical expectations.
However the dispersion relation for the zero modes changes dramatically --
instead of the usual linear dispersion relation, , the new
dispersion relation is well fit by where
for a thin wall in the weak field limit, and for a thick
wall of width . This result shows that the energy of the charge carriers on
the domain wall remains below the threshold for expulsion even in the presence
of an external magnetic field. If charge carriers are expelled due to an
additional perturbation, they are most likely to be ejected at the threshold
energy .Comment: 9 pages, 4 figure
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