By Bernard Aupetit

This e-book grew out of lectures on spectral concept which the writer gave on the Scuola. Normale Superiore di Pisa in 1985 and on the Universite Laval in 1987. Its objective is to supply a slightly quickly creation to the hot ideas of subhar monic features and analytic multifunctions in spectral thought. after all there are numerous paths which input the big woodland of spectral thought: we selected to stick with these of subharmonicity and a number of other complicated variables regularly simply because they've been came upon just recently and aren't but a lot frequented. In our booklet seasoned pri6t6$ $pectrale$ de$ algebre$ de Banach, Berlin, 1979, we made a primary incursion, a slightly technical one, into those newly stumbled on parts. on the grounds that that point the timber and the thorns were lower, so the stroll is extra agreeable and we will pass even additional. with the intention to comprehend the evolution of spectral idea from its very beginnings, it's essential look at the subsequent books: Jean Dieudonne, Hutory of practical AnaIY$u, Amsterdam, 1981; Antonie Frans Monna., sensible AnaIY$i$ in Hutorical Per$pective, Utrecht, 1973; and Frederic Riesz & Bela SzOkefalvi-Nagy, Le on$ d'anaIY$e fonctionnelle, Budapest, 1952. but the photograph has replaced considering those 3 very good books have been written. Readers may well persuade themselves of this by way of evaluating the classical textbooks of Frans Rellich, Perturbation thought, long island, 1969, and Tosio Kato, Perturbation thought for Linear Operator$, Berlin, 1966, with the current paintings.

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H d . h . PI P2 III t e secon term gIve t e equatIOn 36(n - 2j)(n - 2j + l)bj + 4(3j + 8 + 2)(3n + 12(n - 2j)aj = 0, 3j + 301 + 6 + l)bi +I (4) h-Harmonic Polynomials, h-Hankel Transform, ... 41 where 0:::; j :::; [(n-1)/2]. We set 8 = -1 in (3) and (4). "( n _ 2J. b. (n-2j+1)! 4 of [371]. "( n + l)n-i _ 2J. ')' b. (n-2j+1)! ' and this gives the h-harmonic polynomial P3n+5(Z) = Z2 r3n+3C::t: (cos 9) - zr 3nH C::+ I(cos 39) = z2c~~il,a)(z3), n ~ -1, (6) of degree 3n + 5. The conjugates of the polynomials (5) and (6) are also h-harmonic.

The operators Tt. We can consider on h-harmonic polynomials the scalar product of the space ,r}(sn-I, h 2 dw). Therefore, we have the operator T;* which is adjoint to the operator T i . Since Tif)f C f)f+1 then T;* f)f C f)f-1. The aim of this section is to prove the formula Ttp(x) = (n + 2r + 21') [XiP(X) - (n + 2r + 21' - 2)-1 IxI2TiP(X)] , where P E f)~ and l' P E f)~, = 0'1 + ... + am. To prove this formula we first show that for + 2TiP(X), (2) 2)-1IxI 2Tip(X) E f)~+I. (3) ~h(XiP(X)) = Xi~hP(X) XiP(X) - (n By the product rules for ~ ~ + 2r + 21' - and \7 we have ~h(XiP(X)) = Xi~p(X) apeX) + 2~ .

Ft + (VFt, VF2 ))dx, (2) n where F I ,F2 E C 2 (n). (hh) n + (V(hh), V(fz h))] dx. (3) Chapter 1. 22 If Fl = h 1 ,F2 = fthh in (2), then we get j fth ~~ hdp, = an j [fd2hflh + (V(Jd2h), Vh)]dx. (4) n Subtracting equation (4) from equation (3) after some transformations we obtain the relation j h ~ h 2dp, = an j[hh(fl(fth) - ftflh) + h2(Vft, Vfz)]dx n which leads to formula (1). Lemma is proved. Theorem 1. If PI E f)~'P2 E f)~ and r j f:. k, then pl(X)p2(X)h(x)2dw = o. (5) S,",-1 Proof By using formula (1), the fact that the operator Dh is symmetric, and the formula 1 en j f(x)dx = j r,,-ldr j B 0 f(rx)dw(x), sn-l we obtain (degpl - degp2) j PIP2h2dw = en j(P2LhPl - PILhP2)h2dx B sn-l = en j (P2DhPl - PI DhP2)h 2dx = O.