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We compare the usual operator modulus with two symmetrized variants, the arithmetic symmetric modulus and the quadratic symmetric modulus. For every unitarily invariant norm, we determine sharp equivalence constants among these three…

Functional Analysis · Mathematics 2026-03-03 Teng Zhang

The main purpose of this article is to study estimates for the Tsallis relative operator entropy, by the use of Hermite-Hadamard inequality. Thus, we obtain alternative bounds for the Tsallis relative operator entropy. In the process to…

Functional Analysis · Mathematics 2018-01-11 Shigeru Furuichi , Nicuşor Minculete

In this paper, we investigate the existence and multiplicity of weak solutions to problems involving a superposition operator of the type $$\int_{[0, 1]}(- \Delta)^s u d \mu(s),$$ for a signed measure $\mu$ on the interval of fractional…

Analysis of PDEs · Mathematics 2025-05-27 Danilo Gregorin Afonso , Rossella Bartolo , Giovanni Molica Bisci

We discuss when an operator, subject to a rather general inequality in hereditary form, admits a unitarily equivalent functional model of Agler type in the reproducing kernel Hilbert space associated to the inequality. To the contrary to…

Functional Analysis · Mathematics 2020-07-06 Luciano Abadias , Glenier Bello-Burguet , Dmitry Yakubovich

In this paper we consider a one quartic operator on the $\mathbb{R}^2$ with positive coefficients. Positive fixed points for a quartic operator, were investigated. Theorems on number of positive fixed points of the quartic operator, are…

Functional Analysis · Mathematics 2020-07-14 Yu. Kh. Eshkabilov , Sh. D. Nodirov

Quantum inequalities are lower bounds for local averages of quantum observables that have positive classical counterparts, such as the energy density or the Wick square. We establish such inequalities in general (possibly interacting)…

Mathematical Physics · Physics 2009-10-29 Henning Bostelmann , Christopher J. Fewster

In this paper, exploiting variational methods, the existence of three weak solutions for a class of elliptic equations involving a general operator in divergence form and with Dirichlet boundary condition is investigated. Several special…

Analysis of PDEs · Mathematics 2016-08-26 Giovanni Molica Bisci , Dušan Repovš

Let a quantified inequality constraint over the reals be a formula in the first-order predicate language over the structure of the real numbers, where the allowed predicate symbols are $\leq$ and $<$. Solving such constraints is an…

Logic in Computer Science · Computer Science 2025-10-20 Stefan Ratschan

Let $\mathcal{B}(\mathcal{H})$ denote the Banach algebra of all bounded linear operators acting on complex Hilbert spaces $\mathcal{H}$. In this paper, we first establish several sharply refined versions of Bohr's inequality analogues with…

Complex Variables · Mathematics 2024-11-05 Vasudevarao Allu , Raju Biswas , Rajib Mandal

Families of operator identities appeared as a consequence of an existence of finite-dimensional representation of (super) Lie algebras of first-order differential operators and $q$-deformed (quantum) algebras of first-order…

High Energy Physics - Theory · Physics 2009-10-22 Alexander Turbiner , Gerhard Post

Several applied problems are characterized by the need to numerically solve equations with an operator function (matrix function). In particular, in the last decade, mathematical models with a fractional power of an elliptic operator and…

Numerical Analysis · Mathematics 2021-05-24 Petr N. Vabishchevich

The spinless Salpeter equation presents a rather particular differential operator. In this paper we rewrite this equation into integral and integro-differential equations. This kind of equations are well known and can be more easily…

High Energy Physics - Phenomenology · Physics 2011-05-12 F Brau

We present a Diaz--Metcalf type operator inequality as a reverse Cauchy-Schwarz inequality and then apply it to get the operator versions of P\'{o}lya-Szeg\"{o}'s, Greub-Rheinboldt's, Kantorovich's, Shisha-Mond's, Schweitzer's, Cassels' and…

Functional Analysis · Mathematics 2012-03-22 M. S. Moslehian , R. Nakamoto , Y. Seo

Building up on classical linear formulations, we posit that a broad class of problems in signal synthesis and in signal recovery are reducible to the basic task of finding a point in a closed convex subset of a Hilbert space that satisfies…

Optimization and Control · Mathematics 2021-05-18 Patrick L. Combettes , Zev C. Woodstock

In this paper, we characterize complementable operators and provide more precise expressions for the Schur complement of these operators using a single Douglas solution. We demonstrate the existence of subspaces where the given operator is…

Functional Analysis · Mathematics 2024-06-18 Sachin Manjunath Naik , P. Sam Johnson

Some q-analysis variants of Hardy type inequalities of the form \int_0^b (x^{\alpha-1} \int_0^x t^{-\alpha} f(t) d_qt)^p d_qx \leq C \int_0^b f^p(t) d_qt with sharp constant C are proved and discussed. A similar result with the…

Classical Analysis and ODEs · Mathematics 2014-03-26 Lech Maligranda , Ryskul Oinarov , Lars-Erik Persson

We prove here the Melin H\"ormander inequality for operators with multiple characteristics.

Analysis of PDEs · Mathematics 2015-09-02 Bernard Lascar , Richard Lascar

We present an extension of a previously developed method employing the formalism of the fractional derivatives to solve new classes of integral equations. This method uses different forms of integral operators that generalizes the…

Mathematical Physics · Physics 2010-07-30 D. Babusci , G. Dattoli , D. Sacchetti

An inequality of Hardy type is established for quadratic forms involving Dirac operator and a weight $r^{-b}$ for functions in $\R^n$. The exact Hardy constant $c_b=c_b(n)$ is found and generalized minimizers are given. The constant $c_b$…

Analysis of PDEs · Mathematics 2008-12-16 Adimurthi , Kyril Tintarev

In this paper the boundary value problem for one class of the operator-differential equations of the third order on a semi-axis, where one of the boundary conditions is perturbed by some linear operator is researched. There are received…

Functional Analysis · Mathematics 2011-07-26 Araz R. Aliev , Sevindj F. Babayeva