28,442 research outputs found
Regularized Green's Function for the Inverse Square Potential
A Green's function approach is presented for the D-dimensional inverse square
potential in quantum mechanics. This approach is implemented by the
introduction of hyperspherical coordinates and the use of a real-space
regulator in the regularized version of the model. The application of
Sturm-Liouville theory yields a closed expression for the radial energy Green's
function. Finally, the equivalence with a recent path-integral treatment of the
same problem is explicitly shown.Comment: 10 pages. The final section was expande
General Solutions for Tunneling of Scalar Fields with Quartic Potentials in de Sitter Space
The tunneling rates for scalar fields with quartic potentials in de Sitter
space in the limit of no gravitational back reaction are calculated numerically
and the results are fitted by analytic formulae.Comment: (Contours in Figure 1 corrected, two-dimensional fitting coefficient
corrected, references added.), 16 pages, KUNS 124
Nucleation at the DNA supercoiling transition
Twisting DNA under a constant applied force reveals a thermally activated
transition into a state with a supercoiled structure known as a plectoneme.
Using transition state theory, we predict the rate of this plectoneme
nucleation to be of order 10^4 Hz. We reconcile this with experiments that have
measured hopping rates of order 10 Hz by noting that the viscosity of the bead
used to manipulate the DNA limits the measured rate. We find that the intrinsic
bending caused by disorder in the base-pair sequence is important for
understanding the free energy barrier that governs the transition. Both
analytic and numerical methods are used in the calculations. We provide
extensive details on the numerical methods for simulating the elastic rod model
with and without disorder.Comment: 18 pages, 15 figure
Feasibility study of inlet shock stability system of YF-12
The feasibility of self actuating bleed valves as a shock stabilization system in the inlet of the YF-12 is considered for vortex valves, slide valves, and poppet valves. Analytical estimation of valve performance indicates that only the slide and poppet valves located in the inlet cowl can meet the desired steady state stabilizing flows, and of the two the poppet valve is substantially faster in response to dynamic disturbances. The poppet valve is, therefore, selected as the best shock stability system for the YF-12 inlet
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Continued evaluation of potential for geologic storage of carbon dioxide in the southeastern United States
Southern States Energy Board
Duke Energy
Santee Cooper Power
Southern CompanyBureau of Economic Geolog
Upper bound for the conductivity of nanotube networks
Films composed of nanotube networks have their conductivities regulated by
the junction resistances formed between tubes. Conductivity values are enhanced
by lower junction resistances but should reach a maximum that is limited by the
network morphology. By considering ideal ballistic-like contacts between
nanotubes we use the Kubo formalism to calculate the upper bound for the
conductivity of such films and show how it depends on the nanotube
concentration as well as on their aspect ratio. Highest measured conductivities
reported so far are approaching this limiting value, suggesting that further
progress lies with nanowires other than nanotubes.Comment: 3 pages, 1 figure. Minor changes. Accepted for publication in Applied
Physics Letter
Two-Dimensional Bosonization from Variable Shifts in the Path Integral
A method to perform bosonization of a fermionic theory in (1+1) dimensions in
a path integral framework is developed. The method relies exclusively on the
path integral property of allowing variable shifts, and does not depend on the
explicit form of Greens functions. Two examples, the Schwinger model and the
massless Thirring model, are worked out.Comment: 4 page
Vacuum Decay in Theories with Symmetry Breaking by Radiative Corrections
The standard bounce formalism for calculating the decay rate of a metastable
vacuum cannot be applied to theories in which the symmetry breaking is due to
radiative corrections, because in such theories the tree-level action has no
bounce solutions. In this paper I derive a modified formalism to deal with such
cases. As in the usual case, the bubble nucleation rate may be written in the
form . To leading approximation, is the bounce action obtained by
replacing the tree-level potential by the leading one-loop approximation to the
effective potential, in agreement with the generally adopted {\it ad hoc}
remedy. The next correction to (which is proportional to an inverse power
of a small coupling) is given in terms of the next-to-leading term in the
effective potential and the leading correction to the two-derivative term in
the effective action. The corrections beyond these (which may be included in
the prefactor) do not have simple expressions in terms of the effective
potential and the other functions in the effective action. In particular, the
scalar-loop terms which give an imaginary part to the effective potential do
not explicitly appear; the corresponding effects are included in a functional
determinant which gives a manifestly real result for the nucleation rate.Comment: 39 pages, CU-TP-57
No supercritical supercurvature mode conjecture in one-bubble open inflation
In the path integral approach to false vacuum decay with the effect of
gravity, there is an unsolved problem, called the negative mode problem. We
show that the appearance of a supercritical supercurvature mode in the
one-bubble open inflation scenario is equivalent to the existence of a negative
mode around the Euclidean bounce solution. Supercritical supercurvature modes
are those whose mode functions diverge exponentially for large spatial radius
on the time constant hypersurface of the open universe. Then we propose a
conjecture that there should be ``no supercritical supercurvature mode''. For a
class of models that contains a wide variety of tunneling potentials, this
conjecture is shown to be correct.Comment: 11 pages, 3 postscript figures, tarred, gzipped. submitted to Phys.
Rev. D1
Jet Modification in a Brick of QGP Matter
We have implemented the LPM effect into a microscopic transport model with
partonic degrees of freedom by following the algorithm of Zapp & Wiedemann. The
Landau-Pomeranchuk-Migdal (LPM) effect is a quantum interference process that
modifies the emission of radiation in the presence of a dense medium. In QCD
this results in a quadratic length dependence for radiative energy loss. This
is an important effect for the modification of jets by their passage through
the QGP.
We verify the leading parton energy loss in the model against the leading
order Baier-Dokshitzer-Mueller-Peigne-Schiff-Zakharov (BDMPS-Z) result.
We apply our model to the recent observations of the modification of di-jets
at the LHC.Comment: Presented at Panic 1
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