1,754 research outputs found
Explicit bounds on integrals of eigenfunctions over curves in surfaces of nonpositive curvature
Let be a compact Riemannian surface with nonpositive sectional
curvature and let be a closed geodesic in . And let be
an -normalized eigenfunction of the Laplace-Beltrami operator
with . Sogge, Xi, and Zhang showed
using the Gauss-Bonnet theorem that an improvement over the general bound. We
show this integral enjoys the same decay for a wide variety of curves, where
has nonpositive sectional curvature. These are the curves whose
geodesic curvature avoids, pointwise, the geodesic curvature of circles of
infinite radius tangent to .Comment: 23 pages, 3 figures, arXiv admin note: text overlap with
arXiv:1702.0355
Direct measurement of xenon flashtube opacity
Opacity measurement of xenon flash tube - optical mase
Application of DOT-MORSE coupling to the analysis of three-dimensional SNAP shielding problems
The use of discrete ordinates and Monte Carlo techniques to solve radiation transport problems is discussed. A general discussion of two possible coupling schemes is given for the two methods. The calculation of the reactor radiation scattered from a docked service and command module is used as an example of coupling discrete ordinates (DOT) and Monte Carlo (MORSE) calculations
Fourier coefficients of restrictions of eigenfunctions
Let be an orthonormal basis of Laplace eigenfunctions of a compact
Riemannian manifold . Let be a submanifold and let
be an orthonormal basis of Laplace eigenfunctions of with the
induced metric. We obtain joint asymptotics for the Fourier coefficients of restrictions of to . In particular, we
obtain asymptotics for the sums of the norm-squares of the Fourier coefficients
over the joint spectrum of the
(square roots of the) Laplacian on and the Laplacian
on in a family of suitably `thick' regions in . Thick regions
include (1) the truncated cone and
, and (2) the slowly thickening strip and , where
is monotonic and . Key tools for
obtaining these asymptotics include the composition calculus of Fourier
integral operators and a new multidimensional Tauberian theorem.Comment: 36 pages. Referees' suggestions incorporated. To appear in Sci. China
Mat
The VC-dimension of quadratic residues in finite fields
We study the Vapnik-Chervonenkis (VC) dimension of the set of quadratic
residues (i.e. squares) in finite fields, , when considered as a
subset of the additive group. We conjecture that as , the squares
have the maximum possible VC-dimension, viz. . We prove,
using the Weil bound for multiplicative character sums, that the VC-dimension
is . We also provide numerical evidence for
our conjectures. The results generalize to multiplicative subgroups of bounded index.Comment: 21 pages, 3 figure
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