Moment Problem

arimoto@iname.com

Please inform me if you have an idea in the question stated below.

 

@We cite a paper :

Codimension of polynomial subspace in @for discrete indeterminate measure .

Andrew G.Bakan, Proceedings of the AMS,(2002)vol.130,no 12,3545-3553

Abstracts:

Let be the set of positive Borel measures on the real line @with moments of all orders. A measure is said to be indeterminate if the set @contains at least one measure

other than@ @@@where @is a set of measures such that

@

 

Theorem 1.Let

be any discrete indeterminate measure from the class .

Then the following statements hold.

(A)If ,

where codim @denotes the codimension of the closures of the algebraic polynomialsin .

(B)If @is an n-canonical measure for some nonnegative integer n, then@ there exist numbers , such that

,,

 

I am here interested in a relation between the part (B) in this Theorem and the Cassiefs Proposition in the following.

 

Cassier has characterized n canonical measures in the following way:

 

Proposition 4. Soit @une measure ayant des moments de tous les orders, @un entire, @des points distincts de @nfapartement pas au support de , et @des constantes strictement positives. On a alors les equivalences:

a) @est N-extremale;

b) .

Measures Canoniques dan le Problem Classique des Momens.

Ann.Inst.Fourier,Grenoble,34,2(1984),45-52.

 

Question[1]:

Is Cassierfs Proposition@ a special case of the Bakanfs Theorem 1 ?

For example @for n points of k. Doesfnt this be permitted?

Question[2]:

is known to be a value at of some N-extremal measure.

Cassierfs@ proposition@ said that n-canonocal measures are larger than N-extremal measure for n supporting points. But Theorem 1 seems to describe that n canonical measure is less than N-extremal measure@ @in .

Is this a contradiction?@ I think that itfs not, and@ that fs@ should come from more than two N-extremal measures. Probably they come from the n N-extremal measures.

 

Akio Arimoto

Musashi Institute of Technology,

Setagaya-ku@Tamazutumi@‚P|‚Q‚X|‚P,158

Tokyo Japan

 

mailto:arimoto@iname.com

 

Barry Simon The classical moment problem as a self-adjoint finite difference operator

1997,Advances in Mathematics, arXiv:math-ph/9906008

Theorem 4.17, (p.45)

where . These are rewritten by Bakan as the following way:

.

We have , @is the rational function of the order n.

Hence

 

2002/10/25

Bakan wrote

,

whose denominator and nominator are by Nevalinna

@(1)

.(2)

Real numbers fs are zeros of ,

, (3)

in the same time they are support points of .

It is easy that

.

Now let @be zeros of the polynomial ,

,

From (1),(2) and (3),

 

and hence we have

 

von Neumann extremal measure @is obtained by making .

Thus we have

.

 

Hence

. In other words,

, and

.

 

By Lagrange interpolation formula, we have

,

and by differentiating both sides, we have

 

 

.

Putting ,