Intertwining of maxima of sum of translates functions with nonsingular kernels

B. Farkas ; B. Nagy ; Sz. Gy. Révész

Trudy Instituta matematiki i mehaniki, Trudy Instituta Matematiki i Mekhaniki UrO RAN, Tome 28 (2022) no. 4, pp. 262-272

Résumé

In previous papers we investigated so-called sum of translates functions $F(\mathbf{x},t):=J(t)+\sum_{j=1}^n \nu_j K(t-x_j)$, where $J:[0,1]\to \underline{\mathbb{R}}:=\mathbb R\cup\{-\infty\}$ is a “sufficiently nondegenerate” and upper-bounded “field function”, and $K:[-1,1]\to \underline{\mathbb{R}}$ is a fixed “kernel function”, concave both on $(-1,0)$ and $(0,1)$, and also satisfying the singularity condition $K(0)=\lim_{t\to 0} K(t)=-\infty$. For node systems $\mathbf{x}:=(x_1,\ldots,x_n)$ with $x_0:=0\le x_1\le\dots\le x_n\le 1=:x_{n+1}$, we analyzed the behavior of the local maxima vector $\mathbf{m}:=(m_0,m_1,\ldots,m_n)$, where $m_j:=m_j(\mathbf{x}):=\sup_{x_j\le t\le x_{j+1}} F(\mathbf{x},t)$. Among other results we proved a strong intertwining property: if the kernel is decreasing on $(-1,0)$ and increasing on $(0,1)$, and the field function is upper semicontinuous, then for any two different node systems there are $i,j$ such that $m_i(\mathbf{x})$$m_i(\mathbf{y})$ and $m_j(\mathbf{x})>m_j(\mathbf{y})$. Here we partially succeed to extend this even to nonsingular kernels.

Détail

Keywords: minimax problems; kernel function; sum of translates function; vector of local maxima; equioscillation; intertwining of interval maxima.