It is known that for $C^{\infty}$ determining sets Markov's property is equivalent to Bernstein's property. The purpose of this paper is to prove an analogous result in the case of compact subsets of algebraic varieties.
We prove that the sharp constant in the univariate Bernstein--Nikolskii inequality for entire functions of exponential type is the limit of the sharp constant in the V. A. Markov type inequality with an exponential weight for coefficients of an algebraic polynomials of degree n as $n\to\iy$.
For parameters $\,c\in(0,1)\,$ and $\,β>0$, let $\,\ell_{2}(c,β)\,$ be the Hilbert space of real functions defined on $\,\mathbb{N}\,$ (i.e., real sequences), for which $$ \| f \|_{c,β}^2 := \sum_{k=0}^{\infty}\frac{(β)_k}{k!}\,c^k\,[f(k)]^2<\infty\,. $$ We study the best (i.e., the smallest possible) constant $\,γ_n(c,β)\,$ in the discrete Markov-Bernstein inequality $$ \|ΔP\|_{c,β}\leq γ_n(c,β)\,\|P\|_{c,β}\,,\quad P\in\mathcal{P}_n\,, $$ where $\,\mathcal{P}_n\,$ is the set of real algebraic polynomials of degree at most $\,n\,$ and $\,Δf(x):=f(x+1)-f(x)\,$. We prove that: (i) $\displaystyl…
We prove two-sided estimates for the best (i.e., the smallest possible) constant $\,c_n(α)\,$ in the Markov inequality $$ \|p_n'\|_{w_α} \le c_n(α) \|p_n\|_{w_α}\,, \qquad p_n \in {\cal P}_n\,. $$ Here, ${\cal P}_n$ stands for the set of algebraic polynomials of degree $\le n$, $\,w_α(x) := x^α\,e^{-x}$, $\,α> -1$, is the Laguerre weight function, and $\|\cdot\|_{w_α}$ is the associated $L_2$-norm, $$ \|f\|_{w_α} = \left(\int_{0}^{\infty} |f(x)|^2 w_α(x)\,dx\right)^{1/2}\,. $$ Our approach is based on the fact that $\,c_n^{-2}(α)\,$ equals the smallest zero of a polynomial $\,Q_n$, orthogonal …