14,612 research outputs found
Recommended from our members
On the block wavelet transform applied to the boundary element method
This paper follows an earlier work by Bucher et al. [1] on the application of wavelet transforms to the boundary element method, which shows how to reuse models stored in compressed form to solve new models with the same geometry but arbitrary load cases - the so-called virtual assembly technique. The extension presented in this paper involves a new computational procedure created to perform the required two-dimensional wavelet transforms by blocks, theoretically allowing the compression of matrices of arbitrary size. Details of the computer implementation that allows the use of this methodology for very large models or at high compression ratios are given. A numerical application shows a standard PC being used to solve a 131,072 DOF model, previously compressed, for 100 distinct load cases in less than 1 hour – or 33 seconds for each load case
Symmetries of plane partitions and the permanent-determinant method
In the paper [J. Combin. Theory Ser. A 43 (1986), 103--113], Stanley gives
formulas for the number of plane partitions in each of ten symmetry classes.
This paper together with results by Andrews [J. Combin. Theory Ser. A 66
(1994), 28-39] and Stembridge [Adv. Math 111 (1995), 227-243] completes the
project of proving all ten formulas.
We enumerate cyclically symmetric, self-complementary plane partitions. We
first convert plane partitions to tilings of a hexagon in the plane by
rhombuses, or equivalently to matchings in a certain planar graph. We can then
use the permanent-determinant method or a variant, the Hafnian-Pfaffian method,
to obtain the answer as the determinant or Pfaffian of a matrix in each of the
ten cases. We row-reduce the resulting matrix in the case under consideration
to prove the formula. A similar row-reduction process can be carried out in
many of the other cases, and we analyze three other symmetry classes of plane
partitions for comparison
Matrix Models, Complex Geometry and Integrable Systems. I
We consider the simplest gauge theories given by one- and two- matrix
integrals and concentrate on their stringy and geometric properties. We remind
general integrable structure behind the matrix integrals and turn to the
geometric properties of planar matrix models, demonstrating that they are
universally described in terms of integrable systems directly related to the
theory of complex curves. We study the main ingredients of this geometric
picture, suggesting that it can be generalized beyond one complex dimension,
and formulate them in terms of the quasiclassical integrable systems, solved by
construction of tau-functions or prepotentials. The complex curves and
tau-functions of one- and two- matrix models are discussed in detail.Comment: 52 pages, 19 figures, based on several lecture courses and the talks
at "Complex geometry and string theory" and the Polivanov memorial seminar;
misprints corrected, references adde
- …