767 research outputs found
Low dimensional strongly perfect lattices. I: The 12-dimensional case
It is shown that the Coxeter-Todd lattice is the unique strongly perfect
lattice in dimension 12
Symmetry and uniqueness of minimizers of Hartree type equations with external Coulomb potential
In the present article we study the radial symmetry of minimizers of the
energy functional, corresponding to the repulsive Hartree equation in external
Coulomb potential. To overcome the difficulties, resulting from the "bad" sign
of the nonlocal term, we modify the reflection method and then, by using
Pohozaev integral identities we get the symmetry result
Configurations of Extremal Even Unimodular Lattices
We extend the results of Ozeki on the configurations of extremal even
unimodular lattices. Specifically, we show that if L is such a lattice of rank
56, 72, or 96, then L is generated by its minimal-norm vectors.Comment: 8 pages. To appear, International Journal of Number Theor
Effects of motor patterns on water-soluble and membrane proteins and cholinesterase activity in subcellular fractions of rat brain tissue
Albino rats were kept for a year under conditions of daily motor load or constant hypokinesia. An increase in motor activity results in a rise in the acetylcholinesterase activity determined in the synaptosomal and purified mitochondrial fractions while hypokinesia induces a pronounced decrease in this enzyme activity. The butyrylcholinesterase activity somewhat decreases in the synaptosomal fraction after hypokinesia but does not change under the motor load pattern. Motor load causes an increase in the amount of synaptosomal water-soluble proteins possessing an intermediate electrophoretic mobility and seem to correspond to the brain-specific protein 14-3-2. In the synaptosomal fraction the amount of membrane proteins with a low electrophoretic mobility and with the cholinesterase activity rises. Hypokinesia, on the contrary, decreases the amount of these membrane proteins
Construction of spherical cubature formulas using lattices
We construct cubature formulas on spheres supported by homothetic images of
shells in some Euclidian lattices. Our analysis of these cubature formulas uses
results from the theory of modular forms. Examples are worked out on the sphere
of dimension n-1 for n=4, 8, 12, 14, 16, 20, 23, and 24, and the sizes of the
cubature formulas we obtain are compared with the lower bounds given by Linear
Programming
An elementary approach to toy models for D. H. Lehmer's conjecture
In 1947, Lehmer conjectured that the Ramanujan's tau function
never vanishes for all positive integers , where is the -th
Fourier coefficient of the cusp form of weight 12. The theory of
spherical -design is closely related to Lehmer's conjecture because it is
shown, by Venkov, de la Harpe, and Pache, that is equivalent to
the fact that the shell of norm of the -lattice is a spherical
8-design. So, Lehmer's conjecture is reformulated in terms of spherical
-design.
Lehmer's conjecture is difficult to prove, and still remains open. However,
Bannai-Miezaki showed that none of the nonempty shells of the integer lattice
\ZZ^2 in \RR^2 is a spherical 4-design, and that none of the nonempty
shells of the hexagonal lattice is a spherical 6-design. Moreover, none
of the nonempty shells of the integer lattices associated to the algebraic
integers of imaginary quadratic fields whose class number is either 1 or 2,
except for \QQ(\sqrt{-1}) and \QQ(\sqrt{-3}) is a spherical 2-design. In
the proof, the theory of modular forms played an important role.
Recently, Yudin found an elementary proof for the case of \ZZ^{2}-lattice
which does not use the theory of modular forms but uses the recent results of
Calcut. In this paper, we give the elementary (i.e., modular form free) proof
and discuss the relation between Calcut's results and the theory of imaginary
quadratic fields.Comment: 18 page
The Transmission Acoustic Scattering Problem for Bi-Spheres in Low-Frequency Regime
An acoustically soft sphere covered by a penetrable eccentric spherical shell disturbs the propagation of an incident
plane wave field. It is shown that there exists exactly one bispherical coordinate system that describes the given geometry.
The incident wave is assumed to have a wavelength which is
much larger than the characteristic dimension of the scatterer
and thus the low-frequency approximation method is applicable to
the scattering problem. The incomplete R-separation of variables
in bispherical coordinates and the normal differentiation involved
in the transmission boundary conditions lead to a three-term recurrence relation for the series coefficients corresponding to the
scattered fields. Thus, the potential boundary-value problem for
the leading low-frequency approximations is reduced to infinite
tridiagonal linear systems, which are solved analytically
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