7 papers
Duality for Delsarte's extremal problem on locally compact Abelian groups
Elena E. Berdysheva, Bálint Farkas, Marcell Gaál +2
The Delsarte extremal problem for positive definite functions, originally introduced by Delsarte in coding theory to bound the size of error-correcting codes, has since found appli…
Duality for Delsarte's extremal problem on compact Gelfand pairs
Elena E. Berdysheva, Bálint Farkas, Marcell Gaál +2
We study Delsarte-type problems for positive definite functions on compact Gelfand pairs as infinite-dimensional linear programming problems. This setup includes, as a particular c…
On extremal problems of Delsarte type for positive definite functions on LCA groups
Elena E. Berdysheva, Mita D. Ramabulana, Szilárd Gy. Révész
A unifying framework for some extremal problems on locally compact Abelian groups is considered, special cases of which include the Delsarte and Turán extremal problems. A slight v…
The pointwise limit of metric integral operators approximating set-valued functions
Elena E. Berdysheva, Nira Dyn, Elza Farkhi +1
For set-valued functions (SVFs, multifunctions), mapping a compact interval into the space of compact non-empty subsets of , we study approximation based on…
Metric approximation of set-valued functions of bounded variation by integral operators
Elena E. Berdysheva, Nira Dyn, Elza Farkhi +1
We introduce an adaptation of integral approximation operators to set-valued functions (SVFs, multifunctions), mapping a compact interval into the space of compact non-empt…
Metric Fourier approximation of set-valued functions of bounded variation
Elena E. Berdysheva, Nira Dyn, Elza Farkhi +1
We introduce and investigate an adaptation of Fourier series to set-valued functions (multifunctions, SVFs) of bounded variation. In our approach we define an analogue of the parti…
Delsarte's Extremal Problem and Packing on Locally Compact Abelian Groups
Elena Berdysheva, Szilárd Gy. Révész
Let G be a locally compact Abelian group, and let X, Y be two open sets in G. We investigate the extremal constant C(X,Y) defined to be the supremum of integrals of functions f fro…