As is well-known, unlike the one-dimensional case, there exist nonnegative polynomials in several real variables that are not sums of squares. First, we briefly review a method approximating any real-valued continuous compactly supported function defined on closed unbounded subset by dominating special This also works several-dimensional cases. To perform this, Hahn–Banach-type theorem (Kantoro...

1. Topological Vector Spaces 1 1.1. The Krein-Milman theorem 7 2. Banach Algebras 11 2.1. Commutative Banach algebras 14 2.2. ∗–Algebras (over complexes) 17 2.3. Problems on Banach algebras 20 3. The Spectral Theorem 21 3.1. Problems on the Spectral Theorem (Multiplication Operator Form) 26 3.2. Integration with respect to a Projection Valued Measure 27 3.3. The Functional Calculus 34 4. Unboun...

This paper presents a criteria for the existence and uniqueness of solutions to two point boundary value problems associated with a second order non-linear fuzzy differential equations. The main tools employed are estimates on Green’s function, Ascoli’s Lemma and a fixed point theorem of Banach. Mathematics subject classification (2000): 34A10, 26E50, 34B15.

‎In this paper‎, ‎we prove some theorems related to properties of‎ ‎generalized symmetric hybrid mappings in Banach spaces‎. ‎Using Banach‎ ‎limits‎, ‎we prove a fixed point theorem for symmetric generalized‎ ‎hybrid mappings in Banach spaces‎. ‎Moreover‎, ‎we prove some weak‎ ‎convergence theorems for such mappings by using Ishikawa iteration‎ ‎method in a uniformly convex Banach space.

1. Topological Vector Spaces 1 1.1. The Krein-Milman theorem 7 2. Banach Algebras 11 2.1. Commutative Banach algebras 14 2.2. ∗–Algebras (over complexes) 17 2.3. Problems on Banach algebras 20 3. The Spectral Theorem 21 3.1. Problems on the Spectral Theorem (Multiplication Operator Form) 26 3.2. Integration with respect to a Projection Valued Measure 27 3.3. The Functional Calculus 34 4. Unboun...

where Id is the identity operator on C[0, 1]. This equation is now called Daugavet equation. The Banach space X is said to have the Daugavet property when all compact operators on X satisfy the Daugavet equation. More information about the Daugavet spaces can be found in [Werner, 2001]. In the same paper was also posed the question, whether the Banach space of Lipschitz functions on unit square...

The Banach contraction principle appeared in explicit form in Banach’s thesis [5] in 1922 where it was used to establish the existence of a solution for an integral equation. Since then, it has become a very popular tool in solving existence problems in many branches of mathematics. Extensions of this principle were obtained either by generalizing the domain of mappings or by extending the cont...