Mathieu functions of general order: connection formulae, base functions and asymptotic formulae. IV. The Liouville-Green method applied to the Mathieu equation

The methods described in part III and the formulae derived in part II are applied to the construction of a comprehensive set of asymptotic formulae relating to the Mathieu equation y ′ ′ + ( λ + 2 h 2 cos ⁡ 2 z ) y = 0 with real parameters. These comprise formulae both ( a ) for the auxiliary parameters and ( b ), in terms of exponential and circular functions, for the fundamental solution, a function of a complex variable, and the various pairs of real-variable base-functions, all introduced in part II. With the aid of these, together with connection formulae also obtained in part II, approximations can readily be obtained for Mathieu functions of various types, including in particular periodic functions. Formulae for solutions are applicable on the half-strip { z : 0 ⩽ Re z ⩽ 1 2 π , Im z ⩾ 0 } , with the transition point of the differential equation which lies on its frontier removed, or in the case of real-variable solutions of the ordinary or modified equation, on the interval [0,½π] or [0, ∞] respectively, with the same qualification as for the half-strip when this is relevant. The formulae cover the full range of the parameters subject to A ≠ ± 2h 2 . The O -terms providing error estimates are uniformly valid on any subdomain of the independent variable and parameters on which they remain bounded.

Connection formulae are examined which relate a solution y(z) of the Mathieu equation y" + (A + 2h 2 cos 2z) y = 0 with the solutions y ( ± z ± nπ) generated from it by the symmetry group of the equation. The treatment is exact, and is made first in the context of more general periodic differential equations; the results are then specialized to the Mathieu equation, a function of the third kind, characterized by its asymptotic behaviour as z → ∞i, being taken as fundamental. Two parameter ranges are then distinguished, corresponding to the regions of the stability diagram (a) where the solutions are always unstable and ( b ) where subregions of stability and instability alternate. Auxiliary parameters are defined in the two cases, and pairs of real-variable base-functions are constructed, appropriate to the ordinary Mathieu equation and to two types of modified equation. These pairs satisfy criteria introduced by Miller (1950). Comprehensive formulae are derived, relating these base-functions to standard types of Mathieu function, and special attention is given to periodic solutions.


This is the first, introductory, paper of a series devoted to the derivation of a comprehensive set of approximate formulae for solutions of Mathieu’s equation with real parameters, in terms both of elementary and of higher transcendental functions. Order-of-magnitude error-estimates are obtained; these in every case reflect faithfully the behaviour of the actual error over the appropriate range of parameters and of independent variable. The general scope of the work is outlined in this Introduction, and is compared with that of previous work, in particular that of Langer (1934 b ). There then follows a description of the plan of the work and of the content of the several parts.


An account is given of the Liouville-Green method for the approximate solution, with error estimates, of linear second-order differential equations, together with certain extensions of the method. The purpose is to make readily available a range of techniques for use in the two final parts of the present series. The topics treated include: ( a ) the construction of approximations in terms of both elementary and higher transcendental functions, ( b ) the relations between approximations of the same solution in terms of different functions, ( c ) the identification of solutions and the estimation of connection coefficients, ( d ) uniform estimation of the error-control function in problems with more than one widely ranging parameter, ( e ) the construction of majorants for approximating functions, the last two being required for the derivation of satisfactory error estimates. There is little in this part that is new, though a method of constructing approximations in terms of Bessel functions is developed specifically for application to the Mathieu equation. Apart from this, some aspects of the presentation are thought to be novel.


The methods of part III are further applied to the construction of approximations for the fundamental solution and base functions of part II in terms of higher transcendental functions. The domain of validity is now the complete half-strip {z; 0 ≤ Re z ≤ ½π, Im z ≥. 0} without exceptional point. Relative remainder estimates are again uniformly valid provided they are bounded. Specifically, approximations are obtained in terms of: ( a ) Airy functions, applicable if A ≠ ± 2h 2 ; ( b ) parabolic cylinder functions, applicable if |A ≥ 4h 2 , including A = ± 2h 2 ; ( c ) Bessel functions, applicable if |A| ≥ 4h 2 ; these formulae have maximum relative error A - 3/2 h 2 O (l) on the half-strip, even if h is arbitrarily small, provided only that A -1 is bounded. This is significantly better when A/h 2 is large than the corresponding estimate, A -½ 0(1), for the Airy function approximations. Certain more refined estimates for the auxiliary parameters introduced in part II are also obtained.


1976 ◽  
Vol 43 (3) ◽  
pp. 455-458 ◽  
Author(s):  
Kenzo Sato

On the basis of the ordinary thin plate theory, the stability of a simply supported elliptical plate subjected to uniform compression in its middle plane is considered by the use of circular functions, hyperbolic functions, Mathieu functions, and modified Mathieu functions which are solutions of the equilibrium equation of the buckled plate. The first five eigenvalues for the buckling mode symmetrical about both axes are calculated numerically for a variety of aspect ratios of the ellipse. The limiting cases of a circular plate and of an infinitely long strip are also discussed.


1928 ◽  
Vol 24 (2) ◽  
pp. 223-230 ◽  
Author(s):  
S. Goldstein

The Mathieu functions of period π and 2π have recently been constructed by the help of analysis similar to that developed by Laplace, Kelvin, Darwin and Hough to find the free tides symmetrical about the axis of a rotating globe. The purpose of this note is to show that a similar construction can be carried out for the second solution of the Mathieu equation, when one solution is periodic in π or 2π, by the help of analysis similar to that used for forced tides. The construction is effected in a form suitable for numerical computation.


1928 ◽  
Vol 47 ◽  
pp. 294-301 ◽  
Author(s):  
E. L. Ince

The importance in Mathematical Physics of the Bessel functions, whose order is half an odd integer, suggests that the corresponding Mathieu functions may be worthy of a closer attention than they have yet received. At the very least it is expedient to pave the way for their computation. In the second paper bearing the above title, asymptotic developments of the characteristic numbers which correspond to these functions were given; it is here proposed, in the first place, to take the more direct line of approach.


Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3246
Author(s):  
Aiting Wang ◽  
Wenhua Wang ◽  
Baode Li

In 2011, Dekel et al. developed highly geometric Hardy spaces Hp(Θ), for the full range 0<p≤1, which were constructed by continuous multi-level ellipsoid covers Θ of Rn with high anisotropy in the sense that the ellipsoids can rapidly change shape from point to point and from level to level. In this article, when the ellipsoids in Θ rapidly change shape from level to level, the authors further obtain some real-variable characterizations of Hp(Θ) in terms of the radial, the non-tangential, and the tangential maximal functions, which generalize the known results on the anisotropic Hardy spaces of Bownik.


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