English

A homeomorphism theorem for sums of translates

Classical Analysis and ODEs 2023-02-07 v3

Abstract

For a fixed positive integer nn consider continuous functions K1, K_1,\dots, Kn:[1,1]R{} K_n:[-1,1]\to \mathbb{R}\cup\{-\infty\} that are concave and real valued on [1,0)[-1,0) and on (0,1](0,1], and satisfy Kj(0)=K_j(0)=-\infty. Moreover, let J:[0,1]R{}J:[0,1]\to \mathbb{R}\cup\{-\infty\} be upper bounded and such that [0,1]J1({})[0,1]\setminus J^{-1}(\{-\infty\}) has at least n+1n+1 elements, but it is arbitrary otherwise. For x0:=0<x1<<xnxn+1:=1x_0:=0<x_1<\dots< x_n \le x_{n+1}:=1, so called nodes, and for t[0,1]t\in [0,1] consider the sum of translates function F(x1,,xn,t):=J(t)+j=1nKj(txj)F(x_1,\ldots,x_n,t):=J(t)+\sum_{j=1}^n K_j(t-x_j), and the vector of interval maximum values mj:=mj(x1,,xn):=maxt[xj,xj+1]F(x1,,xn,t)m_j:=m_j(x_1,\ldots,x_n):=\max_{t\in [x_j,x_{j+1}]}F(x_1,\ldots,x_n,t) (j=0,1,,nj=0,1,\ldots,n). We describe the structure of the arising interval maxima as the nodes run over the nn-dimensional simplex. Applications presented here range from abstract moving node Hermite-Fej\'er interpolation for generalized algebraic and trigonometric polynomials via Bojanov's problem to more abstract results of interpolation theoretic flavour.

Keywords

Cite

@article{arxiv.2112.11029,
  title  = {A homeomorphism theorem for sums of translates},
  author = {Bálint Farkas and Béla Nagy and Szilárd Gy. Révész},
  journal= {arXiv preprint arXiv:2112.11029},
  year   = {2023}
}

Comments

minor corrections to the previous version