TY - JOUR
AU - Dmytryshyn, M.I.
PY - 2020/12/27
Y2 - 2024/06/17
TI - Approximation of positive operators by analytic vectors
JF - Carpathian Mathematical Publications
JA - Carpathian Math. Publ.
VL - 12
IS - 2
SE - Scientific articles
DO - 10.15330/cmp.12.2.412-418
UR - https://journals.pnu.edu.ua/index.php/cmp/article/view/4441
SP - 412-418
AB - <p>We give the estimates of approximation errors while approximating of a positive operator $A$ in a Banach space by analytic vectors. Our main results are formulated in the form of Bernstein and Jackson type inequalities with explicitly calculated constants. We consider the classes of invariant subspaces ${\mathcal E}_{q,p}^{
u,\alpha}(A)$ of analytic vectors of $A$ and the special scale of approximation spaces $\mathcal {B}_{q,p,\tau}^{s,\alpha}(A)$ associated with the complex degrees of positive operator. The approximation spaces are determined by $E$-functional, that plays a similar role as the module of smoothness. We show that the approximation spaces can be considered as interpolation spaces generated by $K$-method of real interpolation. The constants in the Bernstein and Jackson type inequalities are expressed using the normalization factor.</p>
ER -