arXiv subjects
Publications and source records attributed to Richard J. Mathar.
A C99 program is presented which calculates the Clausen sums for non-negative integer indices j and real arguments x. The implementation is split into three major cases. For large j, a direct, truncated summation of the sum is performed. For smaller j, the associate polynomial of x is evaluated if applicable; otherwise a Chebyshev series is constructed by repeated integration of a (truncated) Chebyshev representation of Cl_2(x), and evaluated.
The simple cubic lattice defines a set of points at regular distances. The volume of the Voronoi cells around each point may serve as a weight for integration over the entire space. We add interstitial points to this grid according to the rule that these have maximum distance to the existing points, or by the equivalent rule that they are placed at the vertices of the Voronoi cells of the existing lattice. Choices of that kind appear in numerical sampling with maximum independent data points if the numerical expense of computing values represented at the lattice points is high. The volumes and shapes of the Voronoi cells of these enriched/supersampled lattices are discussed in detail while this insertion is recursively executed three times in succession.
We tabulate the abscissae and associated weights for numerical integration of integrals with either the singular weight function (-log x)^m for exponents m=1, 2 or 3, or the symmetric weight function cos(pi*x/2). Standard brute force arithmetics generates explicit pairs of these values for up to 128 nodes.
A regular polygon circumscribing another regular polygon (with a different side number) may be tightened to minimize the difference of both areas. The manuscripts computes the optimum result under the restriction that both polygons are concentric, and obtains limits if the process is repeated in a two-dimensional Babuschka-doll fashion with side numbers increasing or decreasing by one or stepping through the prime numbers. The new aspect compared to the circumscription discussed in the literature so far is that further squeezing of the outer polygon is possible as we drop the requirement of drawing intermediate spacing circles between the polygon pairs.
The two Fresnel Integrals are real and imaginary part of the integral over complex-valued exp(ix^2) as a function of the upper limit. They are special cases of the integrals over x^m*exp(i*x^n) for integer powers m and n, which are essentially Incomplete Gamma Functions. We generalize one step further and focus on evaluation of the integrals with kernel p(x)*exp[i*phi(x)] and polynomials p and phi. Series reversion of phi seems not to help much, but repeated partial integration leads to a first order differential equation for an auxiliary oscillating function which allows to fuse the integrals and their complementary integrals.
The manuscript reviews Dirichlet Series of important multiplicative arithmetic functions. The aim is to represent these as products and ratios of Riemann zeta-functions, or, if that concise format is not found, to provide the leading factors of the infinite product over zeta-functions. If rooted at the Dirichlet series for powers, for sums-of-divisors and for Euler's totient, the inheritance of multiplicativity through Dirichlet convolution or ordinary multiplication of pairs of arithmetic functions generates most of the results.
Ten values of 12-j symbols of the first kind published earlier are challenged by values calculated with an independent Python program. The program first implements a narrow class of square roots of rational numbers, utilizing Python's unlimited representation of big integers. Wigner's 3jm symbols, 6-j, 9-j, 12-j and 15-j symbols are then calculated by their familiar representations as sums over products of these.
The 3-regular graphs representing sums over products of Wigner 3-jm symbols are drawn on up to 12 vertices (complete to 18j-symbols), and the irreducible graphs on up to 14 vertices (complete to 21j-symbols). The Lederer-Coxeter-Frucht notations of the Hamiltonian cycles in these graphs are tabulated to support search operations.
Association of some integers n >= 54 to divisibility classes in the Shevelev article of 2007 is corrected.
The polarization effect of the 31 reflections within the mirror train of an auxiliary telescope of the Very Large Telescope Interferometer is calculated as a function of pointing direction and rotator angle. With a rough estimate of the mean complex index of refraction of the reflecting surfaces, their Jones matrices are concatenated while tracing a ray from M1 up to the feeding mirror in front of an instrument. The net effect is summarized in terms of the axis ratio of the polarization ellipse of star light that was circularly polarized above the primary mirror.
The phase structure function accumulated by two parallel rays after transmission through a layer of turbulent air is best known by a proportionality to the 5/3rd power of the lateral distance in the aperture, derived from an isotropic Kolmogorov spectrum of the refractive index. For a von-Karman spectrum of the refractive index, a dependence involving a modified Bessel function of the ratio of the distance over the outer scale is also known. A further standard proposition is a proportionality to the path length through the atmospheric layer. The manuscript modifies this factor through a refined calculation of an integral representation of the structure function. The correction establishes a sub-linearity as the lateral distance grows in proportion to the layer thickness; it is more important for large than for small outer scales.
A group of infinite products over low-order rational polynomials evaluated at the sequence of prime numbers is loosely called the Hardy-Littlewood constants. In this manuscript we look at them as factors embedded in a super-product over primes, semiprimes, 3-almost primes etc. Numerical tables are derived by transformation into series over k-almost prime zeta functions. Alternative product representations in a basis of k-almost prime products associated with Euler's formula for the Riemann zeta function are also pointed out.
Estimators of outer scales of atmospheric turbulence usually fit the phase screen snapshots derived from local wave front sensors to a Zernike basis, and then compare the spectrum of expansion coefficients in this basis with a narrowing associated with decreasing outer scales. This manuscript discusses aspects that arise if the Zernike basis is exchanged for a Karhunen-Loeve basis of statistically independent modes. Data acquisition turns out to be more demanding because sensing the tip-tilt mode is required. The data reduction methodology is replaced by fitting of variance ratios of an entire (long exposure) data set. Statistical testing of hypotheses on outer scale models can be applied to a set of modes - supposing other noise originating from detector readout and the optical train can be disentangled.
The Clebsch--Gordan coefficients of the Kronecker products of the irreducible representations of the Quaternion Group Q8, of the Generalized Quaternion Groups Q16 and Q32, and of the factor group (Q32 X Q32)/{(1,1),(-1,-1)} are computed as eigenvectors of a well-known matrix of triple-products of the irreducible representations.
The Feigenbaum-Cvitanovic equation -lambda * g(x)= g(g(lambda * x)) is solved over the interval 0 <= x <= 1 with a Chebyshev series representation of g(x). Accurate expansion coefficients are tabulated for solutions g(x) = 1+O(x^z) with even exponents from z=2 up to z=14.
Real and imaginary part of the limit 2N->infinity of the integral int_{x=1..2N} exp(i*pi*x)*x^(1/x) dx are evaluated to 20 digits with brute force methods after multiple partial integration, or combining a standard Simpson integration over the first halve wave with series acceleration techniques for the alternating series co-phased to each of its points. The integrand is of the logarithmic kind; its branch cut limits the performance of integration techniques that rely on smooth higher order derivatives.
The manuscript establishes a series expansion of the core integral that relates changes in longitude and latitude along the geodetic line in oblate elliptical coordinates, and of a companion integral which is the path length along this line as a function of latitude. The expansion is a power series in the scaled (constant) altitude of the trajectory over the surface of the ellipsoid. Each term of this series is reduced to sums over inverse trigonometric functions, square roots and Elliptic Integrals. The aim is to avoid purely numerical means of integration.
Regular integer lattices are characterized by k unit vectors that build up their generator matrices. These have rank k for D-lattices, and are rank-deficient for A-lattices, for E_6 and E_7. We count lattice points inside hypercubes centered at the origin for all three types, as if classified by maximum infinity norm in the host lattice. The results assume polynomial format as a function of the hypercube edge length.