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In this paper, we show several bounds for the numerical radius of a Hilbert space operator in terms of the Euclidean operator norm. The obtained forms will enable us to find interesting refinements of celebrated results in the literature. Then, the $f$-operator radius, recently defined as a generalization of the Euclidean operator radius, will be studied. Many upper bounds will be found and matched with existing results that treat the numerical radius. Special cases of this discussion will lead to some refinements and generalizations of some well-established results in the field. Further, numerical examples are given to support our findings, and a simple optimization application will be presented.

In this paper, we introduce the $f-$operator radius of Hilbert space operators as a generalization of the Euclidean operator radius and the $q-$operator radius. Properties of the newly defined radius are discussed, emphasizing how it extends some known results in the literature.

In this work, Some new inequalities for the numerical radius of block $n$-by-$n$ matrices are presented. As an application, bounding of zeros of polynomials using the Frobenius companion matrix partitioned by the Cartesian decomposition approach is proved and affirmed by a numerical example showing that our approach of bounding zeros of polynomials could be very effective in comparison with the most famous and some recent results presented in the field., Comment: 15 pages

In this work, a refinement of the Cauchy--Schwarz inequality in inner product space is proved. A more general refinement of the Kato's inequality or the so called mixed Schwarz inequality is established. Refinements of some famous numerical radius inequalities are also pointed out. As shown in this work, these refinements generalize and refine some recent and old results obtained in literature. Among others, it is proved that if $T\in\mathscr{B}\left(\mathscr{H}\right)$, then \begin{align*} \omega^{2}\left(T\right) &\le \frac{1}{12} \left\| \left| T \right|+\left| {T^* } \right|\right\|^2 + \frac{1}{3} \omega\left(T\right)\left\| \left| T \right|+\left| {T^* } \right|\right\| \\ &\le\frac{1}{6} \left\| \left| T \right|^2+ \left| {T^* } \right|^2 \right\| + \frac{1}{3} \omega\left(T\right)\left\| \left| T \right|+\left| {T^* } \right|\right\|, \end{align*} which refines the recent inequality obtained by Kittaneh and Moradi in \cite{KM}., Comment: 13 pages

In this work, some new upper and lower bounds of the Davis-Wielandt radius are introduced. Generalizations of some presented results are obtained. Some bounds of the Davis-Wielandt radius for $n\times n$ operator matrices are established. An extension of the Davis-Wielandt radius to the Euclidean operator radius is introduced., Comment: 19 pages

In this work, the mixed Schwarz inequality for semi-Hilbertian space operators is proved. Namely, for every positive Hilbert space operator $A$. If $f$ and $g$ are nonnegative continuous functions on $\left[0,\infty\right)$ satisfying $f(t)g(t) =t$ $(t\ge0)$, then \begin{align*} \left| {\left\langle {T x,y} \right\rangle_A } \right| \le \left\| {f\left( {\left| T \right|_A x} \right)} \right\|_A \left\| {g\left( {\left| {T^{\sharp_A } } \right|_A y} \right)} \right\|_A \end{align*} for every Hilbert space operator $T$ such that the range of $T^* A$ is a subset in the range of $A$, such that $A$ commutes with $T$, and for all vectors $x,y\in \mathscr{H}$, where $\left| T \right|_A = \left(AT^{\sharp_A}T\right)^{1/2}$ such that $T^{\sharp_A}=A^\dagger T^*A$, where $A^\dagger$ is the Moore-Penrose inverse of $A$. Based on that, some inequalities for the $A$-numerical radius are introduced., Comment: 17 pages

We show that if $f$ is a non-negative superquadratic function, then $A\mapsto\mathrm{Tr}f(A)$ is a superquadratic function on the matrix algebra. In particular, \begin{align*} \tr f\left( {\frac{{A + B}}{2}} \right) +\tr f\left(\left| {\frac{{A - B}}{2}}\right|\right) \leq \frac{{\tr {f\left( A \right)} + \tr {f\left( B \right)} }}{2} \end{align*} holds for all positive matrices $A,B$. In addition, we present a Klein's inequality for superquadratic functions as $$ \mathrm{Tr}[f(A)-f(B)-(A-B)f'(B)]\geq \mathrm{Tr}[f(|A-B|)] $$ for all positive matrices $A,B$. It gives in particular an improvement of the Klein's inequality for non-negative convex function. As a consequence, some variants of the Jensen trace inequality for superquadratic functions have been presented.

In this work, we improve and refine some numerical radius inequalities. In particular, for all Hilbert space operators $T$, the celebrated Kittaneh inequality reads: \begin{align*} \frac{1}{4}\left\| T^*T + TT^*\right\|\le w^{2 }\left(T \right) \le \frac{1}{2}\left\| T^*T + TT^*\right\|. \end{align*} In this work we provide some important refinements for the upper bound of the Kittaned inequality. Indeed, we establish \begin{align*} w^{2 }\left(T \right) \le \frac{1}{2}\left\| T^*T + TT^*\right\| - \frac{1}{4} \mathop {\inf }\limits_{\left\| x \right\| = 1} \left( {\left\langle {\left| T \right|x,x} \right\rangle - \left\langle {\left| T^* \right|x,x} \right\rangle } \right)^2, \end{align*} which also refined and improved as \begin{align*} w^{2 }\left(T \right) \le \frac{1}{2}\left\| T^*T + TT^*\right\| - \frac{1}{2} \mathop {\inf }\limits_{\left\| x \right\| = 1} \left( {\left\langle {\left| T \right|x,x} \right\rangle - \left\langle {\left| T^* \right|x,x} \right\rangle } \right)^2, \end{align*} and \begin{align*} w^{2 }\left(T \right) \le \frac{1}{2} \left\|T^*T+TT^* \right\| -\frac{1}{2} \mathop {\inf }\limits_{\left\| x \right\| = 1} \left(\left\langle {\left| T \right|^{2 }x,x} \right\rangle^{\frac{1}{2}} - \left\langle {\left| T^* \right|^{2 } x,x} \right\rangle^{\frac{1}{2}}\right)^2, \end{align*} with third improvement \begin{align*} w^2 \left( {T } \right) \le \frac{1}{4 }\left\| {\left| T \right| + \left| {T^* } \right| } \right\|^{2} - \frac{1}{{4 }}\mathop {\inf }\limits_{\left\| x \right\| = 1} \left( {\left\langle {\left| T \right| x,x} \right\rangle - \left\langle {\left| {T^* } \right| x,x} \right\rangle } \right)^2. \end{align*} Other general related results are also considered., Comment: 11. arXiv admin note: text overlap with arXiv:1811.08025

In this work, we construct a new general two-point quadratre rules for the Riemann--Stieltjes integral $\int_a^b {f\left( t \right)du\left( t \right)}$, where the integrand $f$ is assumed to be satisfied with the H\"{o}lder condition on $[a,b]$ and the integrator $u$ is of bounded variation on $[a,b]$. The dual formulas under the same assumption are proved. Some sharp error $L^p$--Error estimates for the proposed quadrature rules are also obtained., Comment: 19 pages. arXiv admin note: text overlap with arXiv:1812.10674

In this work, sharp Wirtinger type inequalities for double integrals are established. As applications, two sharp \v{C}eby\v{s}ev type inequalities for absolutely continuous functions whose second partial derivatives belong to $L^2$ space are proved., Comment: 16 pages

In this work, an extension of two-point Ostrowski's formula for $n$-times differentiable functions is proved. A generalization of Taylor formula is deduced. An identity of Fink type for this extension is provided. Error estimates for the considered formulas are also given. Two-point Ostrowski-Gruss type inequalities are pointed out. An expansion of Guessab--Schmeisser two points formula for $n$-times differentiable functions via Fink type identity is established. Generalization of the main result for harmonic sequence of polynomials is established. Several bounds of the presented results are proved., Comment: 32 pages. arXiv admin note: text overlap with arXiv:1703.01535

In this work, a pre-Gr\"{u}ss inequality for positive Hilbert space operators is proved. So that, some numerical radius inequalities are proved. On the other hand, based on a non-commutative Binomial formula, a non-commutative upper bound for the numerical radius of the summand of two bounded linear Hilbert space operators is proved. A commutative version is also obtained as well., Comment: 10 pages

In this work, generalizations of some inequalities for continuous $h$-synchronous ($h$-asynchronous) functions of linear bounded selfadjoint operators under positive linear maps in Hilbert spaces are proved., Comment: 12 pages. arXiv admin note: substantial text overlap with arXiv:1708.06447

In this work, an extension of the generalized mixed Schwarz inequality is proved. A companion of the generalized mixed Schwarz inequality is established by merging both Cartesian and Polar decompositions of operators. Based on that some numerical radius inequalities are proved., Comment: 14 pages

In this work, some generalizations and refinements inequalities for numerical radius of the product of Hilbert space operators are proved. New inequalities for numerical radius of block matrices of Hilbert space operators are also established., Comment: 18 pages. arXiv admin note: text overlap with arXiv:1810.05710, arXiv:1810.10067

In this work, an improvement of H\"{o}lder-McCarty inequality is established. Based on that, several refinements of the generalized mixed Schwarz inequality are obtained. Consequently, some new numerical radius inequalities are proved. New inequalities for numerical radius of $n\times n$ matrix of Hilbert space operators are proved as well. Some refinements of some earlier results were proved in literature are also given. Some of the presented results are refined and it shown to be better than earlier results were proved in literature., Comment: 15 pages

In this work, operator version of Popoviciu's inequality for positive selfadjoint operators in Hilbert spaces under positive linear maps for superquadratic functions is proved. Analogously, using the same technique operator version of Popoviciu's inequality for convex functions is obtained. Some other related inequalities are also deduced., Comment: 11 pages

In this work, the q-analogue of Bernoulli inequality is proved. Some other related results are presented., Comment: 7 pages

In this work, several inequalities of Popoviciu type for h-MN-convex functions are proved, where M or N are denote to Arithmetic, Geometric and Harmonic means and $h$ is a non-negative superadditive or subadditive function., Comment: 26 pages

In this work, we introduce the class of $h$-${\rm{MN}}$-convex functions by generalizing the concept of ${\rm{MN}}$-convexity and combining it with $h$-convexity. Namely, Let $I,J$ be two intervals subset of $\left(0,\infty\right)$ such that $\left(0,1\right)\subseteq J$ and $\left[a,b\right]\subseteq I$. Consider a non-negative function $h: (0,\infty)\to \left(0,\infty\right)$ and let ${\rm{M}}:\left[0,1\right]\to \left[a,b\right] $ $(0

In this work, generalization of some inequalities for continuous $h$-synchronous ($h$-asynchronous) functions of selfadjoint linear operators in Hilbert spaces are proved., Comment: 14 pages

In this work, a generalization of Chebyshev functional is presented. New inequalities of Gruss type via Pompeiu's mean value theorem are established. Improvements of some old inequalities are proved. A generalization of pre-Gruss inequality is elaborated. Some remarks to further generalization of Chebyshev functional are presented. As applications, bounds for the reverse of CBS inequality are deduced. Hardy type inequalities on bounded real interval [a,b] under some other circumstances are introduced. Other related ramified inequalities for differentiable functions are also given., Comment: 30 pages

In this work, a generalization of pre-Gr\"{u}ss inequality is established. Several bounds for the difference between two \v{C}eby\v{s}ev functional are proved., Comment: 18 pages

In this work, an expansion of Guessab-Schmeisser two points formula for n-times differentiable functions via Fink type identity is established. Generalization of the main result for harmonic sequence of polynomials is established. Several bounds of the presented results are proved. As applications, some quadrature rules are elaborated and discussed. Error bounds of the presented quadrature rules via Chebyshev-Gruss type inequalities are also provided., Comment: 27 pages

Extensions and generalizations of Alzer's inequality; which is of Wirtinger type are proved. As applications, sharp trapezoid type inequality and sharp bound for the geometric mean are deduced., Comment: 8 pages