2,762 research outputs found
Singular value decomposition for the 2D fan-beam Radon transform of tensor fields
In this article we study the fan-beam Radon transform of
symmetrical solenoidal 2D tensor fields of arbitrary rank in a unit disc
as the operator, acting from the object space to the data space
The orthogonal polynomial basis of solenoidal tensor
fields on the disc was built with the help of Zernike polynomials
and then a singular value decomposition (SVD) for the operator
was obtained. The inversion formula for the fan-beam tensor transform follows from this decomposition. Thus obtained inversion formula can be
used as a tomographic filter for splitting a known tensor field into potential
and solenoidal parts. Numerical results are presented.Comment: LaTeX, 37 pages with 5 figure
A Solvable Model for Nonlinear Mean Field Dynamo
We formulate a solvable model that describes generation and saturation of
mean magnetic field in a dynamo with kinetic helicity, in the limit of large
magnetic Prandtl number. This model is based on the assumption that the
stochastic part of the velocity field is Gaussian and white in time (the
Kazantsev-Kraichnan ensemble), while the regular part describing the back
reaction of the magnetic field is chosen from balancing the viscous and Lorentz
stresses in the MHD Navier-Stokes equation. The model provides an analytical
explanation for previously obtained numerical results.Comment: 6 page
The Adler -function for SQCD regularized by higher covariant derivatives in the three-loop approximation
We calculate the Adler -function for SQCD in the three-loop
approximation using the higher covariant derivative regularization and the
NSVZ-like subtraction scheme. The recently formulated all-order relation
between the Adler function and the anomalous dimension of the matter
superfields defined in terms of the bare coupling constant is first considered
and generalized to the case of an arbitrary representation for the chiral
matter superfields. The correctness of this all-order relation is explicitly
verified at the three-loop level. The special renormalization scheme in which
this all-order relation remains valid for the -function and the anomalous
dimension defined in terms of the renormalized coupling constant is constructed
in the case of using the higher derivative regularization. The analytic
expression for the Adler function for SQCD is found in this scheme
to the order . The problem of scheme-dependence of the
-function and the NSVZ-like equation is briefly discussed.Comment: 25 pages, 2 figures; the version accepted for publication in Nuclear
Physics
On the possible origin of meteoroid generating asteroid orbits
A mechanism to replenish the Apollo and Amor groups by resonant asteroid-orbit transformation is suggested. The method of this mechanism and the results obtained are discussed
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