Wiener’s problem for positive definite functions

Schoenberg’s Problem on Positive Definite Functions

On a Problem of Turán about Positive Definite Functions

We study the following question posed by Turán. Suppose Ω is a convex body in Euclidean space Rd which is symmetric in Ω and with value 1 at the origin; which one has the largest integral? It is probably the case that the extremal function is the indicator of the half-body convolved with itself and properly scaled, but this has been proved only for a small class of domains so far. We add to thi...

Some numerical radius inequalities with positive definite functions

 ‎Using several examples of positive definite functions‎, ‎some inequalities for the numerical radius of‎ ‎matrices are investigated‎. ‎Also‎, ‎some open problems are stated‎.

Interpolation with Positive Definite Functions

I t i s well-known t h a t k r i g i n g and i n t e r p o l a t i o n by s p l i n e s a r e e q u i v a l e n t . Kr ig ing i s based on a s t o c h a s t i c f o r m u l a t i o n whereas s p l i n e s a r e f o r m u l a t e d I n a d e t e r m i n i s t i c way. A t h i r d p r e s e n t a t i o n i s g i v e n i n terms of Rad ia l P a s i s F u n c t i o n s . The c n n n e c t l o n s b...

Strictly Hermitian Positive Definite Functions

Let H be any complex inner product space with inner product < ·, · >. We say that f : | C → | C is Hermitian positive definite on H if the matrix ( f(< z,z >) )n r,s=1 (∗) is Hermitian positive definite for all choice of z, . . . ,z in H, all n. It is strictly Hermitian positive definite if the matrix (∗) is also non-singular for any choice of distinct z, . . . ,z in H. In this article we prove...