18,374 research outputs found
Solar wind and temperature field of the troposphere
Relationship between solar wind velocities and temperature field of lower troposphere derived from satellite measurement
The Four-Loop Dressing Phase of N=4 SYM
We compute the dilatation generator in the su(2) sector of planar N=4 super
Yang-Mills theory at four-loops. We use the known world-sheet scattering matrix
to constrain the structure of the generator. The remaining few coefficients can
be computed directly from Feynman diagrams. This allows us to confirm previous
conjectures for the leading contribution to the dressing phase which is
proportional to zeta(3).Comment: 19 pages, v2: referenced adde
Two-Loop Sudakov Form Factor in a Theory with Mass Gap
The two-loop Sudakov form factor is computed in a U(1) model with a massive
gauge boson and a model with mass gap. We analyze the result
in the context of hard and infrared evolution equations and establish a
matching procedure which relates the theories with and without mass gap setting
the stage for the complete calculation of the dominant two-loop corrections to
electroweak processes at high energy.Comment: Latex, 5 pages, 2 figures. Bernd Feucht is Bernd Jantzen in later
publications. (The contents of the paper is unchanged.
Distinguishing coherent atomic processes using wave mixing
We are able to clearly distinguish the processes responsible for enhanced
low-intensity atomic Kerr nonlinearity, namely coherent population trapping and
coherent population oscillations in experiments performed on the Rb D1 line,
where one or the other process dominates under appropriate conditions. The
potential of this new approach based on wave mixing for probing coherent atomic
media is discussed. It allows the new spectral components to be detected with
sub-kHz resolution, which is well below the laser linewidth limit. Spatial
selectivity and enhanced sensitivity make this method useful for testing dilute
cold atomic samples.Comment: 9 pages, 5 figure
Experiment K-6-17. Structural changes and cell turnover in the rats small intestine induced by spaceflight
The purpose of this project was to test the hypothesis that the generalized, whole body decrease in synthetic activity associated with microgravity conditions of space flight as evidenced by negative nitrogen balance and muscle atrophy (Nicogossian and Parker, 1982; Oganov, 1981), as well as inhibited lymphocyte proliferation (Bechler and Cogoli, 1986), would be evident in cells characterized by a rapid rate of turnover. As a model, researchers chose to study the turnover of mucosal cells lining the jejunum of the small intestine, since these cells are among the most rapidly proliferating in the body. Under normal conditions, epithelial cells that line the small intestine are continually produced in the crypts of Lieberkuhn. These cells migrate out of the crypts onto intestinal villi, are progressively pushed up the villus as new crypt cells are formed, and ultimately reach the tip of villi where they are then descquamated. In rats, the entire process, from initial proliferation in crypts to desquamation, takes approximately 2 days (Cairnie et al., 1965; Lipkin, 1973). In this study, researchers determined the mitotic index for mucosal cells lining the proximal, middle, and distal regions of the jejunum in rats from three treatment groups (synchronous control, vivarium control and flight), and measured the depth of the crypts of Lieberkuhn and the length of villi present in each of the three jejunal regions sampled
Q2237+0305 source structure and dimensions from light curves simulation
Assuming a two-component quasar structure model consisting of a central
compact source and an extended outer feature, we produce microlensing
simulations for a population of star-like objects in the lens galaxy. Such a
model is a simplified version of that adopted to explain the brightness
variations observed in Q0957 (Schild & Vakulik 2003). The microlensing light
curves generated for a range of source parameters were compared to the light
curves obtained in the framework of the OGLE program. With a large number of
trials we built, in the domain of the source structure parameters, probability
distributions to find "good" realizations of light curves. The values of the
source parameters which provide the maximum of the joint probability
distribution calculated for all the image components, have been accepted as
estimates for the source structure parameters. The results favour the
two-component model of the quasar brightness structure over a single compact
central source model, and in general the simulations confirm the Schild-Vakulik
model that previously described successfully the microlensing and other
properties of Q0957. Adopting 3300 km/s for the transverse velocity of the
source, the effective size of the central source was determined to be about
2x10^15 cm, and Epsilon =2 was obtained for the ratio of the integral
luminosity of the outer feature to that of the central source.Comment: 7 pages, 4 figures, LaTe
Four-dimensional integration by parts with differential renormalization as a method of evaluation of Feynman diagrams
It is shown how strictly four-dimensional integration by parts combined with
differential renormalization and its infrared analogue can be applied for
calculation of Feynman diagrams.Comment: 6 pages, late
On a general analytical formula for U_q(su(3))-Clebsch-Gordan coefficients
We present the projection operator method in combination with the
Wigner-Racah calculus of the subalgebra U_q(su(2)) for calculation of
Clebsch-Gordan coefficients (CGCs) of the quantum algebra U_q(su(3)). The key
formulas of the method are couplings of the tensor and projection operators and
also a tensor form for the projection operator of U_q(su(3)). We obtain a very
compact general analytical formula for the U_q(su(3)) CGCs in terms of the
U_q(su(2)) Wigner 3nj-symbols.Comment: 9 pages, LaTeX; to be published in Yad. Fiz. (Phys. Atomic Nuclei),
(2001
Relationship Between Certain Parameters of the Troposphere and Ionosphere and the Variations of Solar Wind Velocities
Relationship between certain parameters of troposphere and ionosphere, and variations of solar wind velocitie
Two-Loop Iteration of Five-Point N=4 Super-Yang-Mills Amplitudes
We confirm by explicit computation the conjectured all-orders iteration of
planar maximally supersymmetric N=4 Yang-Mills theory in the nontrivial case of
five-point two-loop amplitudes. We compute the required unitarity cuts of the
integrand and evaluate the resulting integrals numerically using a
Mellin--Barnes representation and the automated package of ref.~[1]. This
confirmation of the iteration relation provides further evidence suggesting
that N=4 gauge theory is solvable.Comment: 4 pages, 3 figure
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