Some extensions of Berezin number inequalities on operators

Abstract

In this paper, we establish some upper bounds for Berezin number inequalities including of $2\times 2$ operator matrices and their off-diagonal parts. Among other inequalities, it is shown that if $T=\left[\begin{array}{cc} 0&X, Y&0 \end{array}\right]$, then \begin{align*} \textbf{ber}^{r}(T)\leq 2^{r-2}\left(\textbf{ber}(f^{2r}(|X|)+g^{2r}(|Y^*|))+\textbf{ber}(f^{2r}(|Y|)+g^{2r}(|X^*|))\right)\\ -2^{r-2} \inf_{\|(k_{\lambda_{1}},k_{\lambda_{2}})\|=1} \eta(k_{\lambda_{1}},k_{\lambda_{2}}), \end{align*} where $\eta (k_{\lambda_{1}}, k_{\lambda_{2}}) = \left(\left\langle(f^{2r}(|X|)+g^{2r}(|Y^*|)\right)k_{\lambda_{2}},k_{\lambda_{2}}\right\rangle^\frac{1}{2}-\left\langle \left(f^{2r}(|Y|)+g^{2r}(|X^*|)\right)k_{\lambda_{1}},k_{\lambda_{1}}\right\rangle^\frac{1}{2})^2$, $X, Y$ are bounded linear operators on a Hilbert space $\mathcal H=\mathcal H(\Omega)$, $r\geq 1$ and $f$, $g$ are nonnegative continuous functions on $[0, \infty)$ satisfying the relation $f(t)g(t)=t\,(t\in[0, \infty))$.