Abstract:
We consider the Bernstein–Jackson–Nikol'skii inequalities for fractional derivatives in the case when the norm is asymmetric. Assume that $n\in\mathbb N$, $p_1,p_2,q_1,q_2\in[1,\infty]$, and $\alpha\in\mathbb R_+$. Then
$$
\sup_{\substack t_n\in\tau_n\\t_n\not\equiv 0}\dfrac{\|D^\alpha t_n\|_{q_1,q_2}}{\|t_n\|_{p_1,p_2}}\asymp I_\alpha n^{\alpha+\psi_1(p_1,p_2,q_1,q_2)}+n^{\alpha+\psi_2(p_1,p_2,q_1,q_2)},
$$
where
$$
I_\alpha=\begin{cases}
\alpha,&0\leqslant\alpha\leqslant 1,\\ 1,&\alpha\geqslant 1,
\end{cases}
$$
and the functions $\psi_1$ and $\psi_2$ are given by an explicit formula. The asymptotic behaviour is with respect to $n$ for fixed $\alpha$, $p_1$, $p_2$, $q_1$ and $q_2$.