On spaces of continuous linear mappings between locally convex spaces

We characterize the pairs of Moscatelli Frechet and spaces such that: 1) Every continuous linear map from E into F sends bounded sets in E into precompact ones in F. 2) Every bounded map from E into F sends some 0-neighbourhood in E into a precompact set in F.

We give an expression for the most general continuous linear input-output map that takes the space of (Lebesgue) integrable functions into itself. This expression is a function-space limit of an integral. As an application, a representation result is given for an important family of linear maps that take the space of bounded measurable functions into itself and satisfy a certain continuity condition, and it is noted that no such result holds for a general continuous linear maps that takes the space into itself and meets the continuity condition. Some related material concerning engineering education is also given.

For the Fr'{e}chet algebras $(A, (p_k))$ and $(B, (q_k))$ and $n in mathbb{N}$, $ngeq 2$, a linear map $T:A rightarrow B$ is called textit{almost $n$-multiplicative}, with respect to $(p_k)$ and $(q_k)$, if there exists $varepsilongeq 0$ such that$$q_k(Ta_1a_2cdots a_n-Ta_1Ta_2cdots Ta_n)leq varepsilon p_k(a_1) p_k(a_2)cdots p_k(a_n),$$for each $kin mathbb{N}$ and $a_1, a_2, ldots, a_nin A$. The linear map $T$ is called textit{weakly almost $n$-multiplicative}, if there exists $varepsilongeq 0$ such that for every $kin mathbb{N}$ there exists $n(k)in mathbb{N}$ with$$q_k(Ta_1a_2cdots a_n-Ta_1Ta_2cdots Ta_n)leq varepsilon p_{n(k)}(a_1) p_{n(k)}(a_2)cdots p_{n(k)}(a_n),$$for each $k in mathbb{N}$ and $a_1, a_2, ldots, a_nin A$.The linear map $T$ is called $n$-multiplicative if$$Ta_{1}a_{2} cdots a_{n} = Ta_{1} Ta_{2} cdots Ta_{n},$$for every $a_{1}, a_{2},ldots, a_{n} in A$.In this paper, we investigate automatic continuity of (weakly) almost $n$-multiplicative maps between certain classes of Fr'{e}chet algebras, including Banach algebras. We show that if $(A, (p_k))$ is a Fr'{e}chet algebra and $T: A rightarrow mathbb{C}$ is a weakly almost $n$-multiplicative linear functional, then either $T$ is $n$-multiplicative, or it is continuous. Moreover, if $(A, (p_k))$ and $(B, (q_k))$ are Fr'{e}chet algebras and $T:A rightarrow B$ is a continuous linear map, then under certain conditions $T$ is weakly almost $n$-multiplicative for each $ngeq 2$. In particular, every continuous linear functional on $A$ is weakly almost $n$-multiplicative for each $ngeq 2$.

Analytical expressions for power spectral density issued from one-dimensional continuous piecewise linear maps with three slopes

A linear map $T$ from a Banach algebra $A$ into another $B$ preserves zero products if $T(a)T(b)=0$ whenever $a,b\in A$ are such that $ab=0$. This paper is mainly concerned with the question of whether every continuous linear surjective map $T\colon A\rig

It is well-known that the algebraic tensor product E ⊗ Y of a not necessarily locally convex topological vector space E and a locally convex space Y can be identified with a subspace of the so-called e-product EeY (a space of continuous linear mappings from Y′ into E). So, whenever EeY is complete, even the completed tensor product is (isomorphic to) a subspace of EeY. As this occurs in many important cases, it is interesting to remark that, for each continuous linear operator u from a locally convex space F into E, there exists a locally convex U with continuous embedding j∶U→E and a continuous linear map u∶F→U such that u=j·u. As main applications of a combination of these ideas, we obtain a characterization of the functions in as continuous functions with values in locally convex spaces (this gives new aspects for the intergration theory of Gramsch [5]) and a result extending a theorem in [6] on holomorphic functions with values in non locally convex spaces to arbitrary complex manifolds.

A theory of test function spaces is developed. These are generalizations of test function spaces of type Hμ. The elements of the dual spaces are called ultradistributions, It is shown that the Hankel transformation hμ for μ≧−1/2 is a continuous linear mapping from each of these spaces into certain spaces of the above type. The generalized Hankel transformation hμ′ is defined as a continuous linear mapping between the dual spaces. Hankel transformations of arbitrary order and also of arbitrary growth are studied. The theory thus developed is applied to prove a uniqueness theorem for the Cauchy problem for the operator Sμ.

<abstract><p>In this paper, we show that every continuous linear map between unital $ C^\ast $-algebras is skew Lie triple derivable at the identity is a $ \ast $-derivation and that every continuous linear map between unital $ C^\ast $-algebras which is a skew Lie triple homomorphism at the identity is a Jordan $ \ast $-homomorphism.</p></abstract>

Continuous extension of functions from countable sets

The purpose of this paper is to introduce and to discuss the concept of orthogonality in the locally convex spaces, and obtaining some results on orthogonality in locally convex spaces similar to orthogonality of normed spaces. We shall obtain some characterizations of the best approximation and the best coapproximation in locally convex spaces.

Surjective linear maps preserving local spectra

If E is a complex (DFC)-space (see § 2), we show that E leads to pure uniform holomorphy (see §2) if and only if its Frechet dual space E′ is separable (see Theorem 1, where these two conditions have other eight equivalent ones). By using a theorem of Mujica (see §4), we consider the (DFC)-space K(K) of germs around K of holomorphic C-valued functions where K is a nonvoid compact subset of a complex metrizable locally convex space E, and ℋ(K) is endowed with the topology ℐ0 obtained as an inductive limit of compact-open topologies (see §4). Not only Theorem 1 applies to ℋ(K), with E replaced by ℋ(K) in its statement, but also ℋ(K) leads to pure uniform holomorphy if and only if E is separable (see Theorem 2).

Linear maps preserving G-unitary operators in Hilbert space

Let $G$ be a locally compact amenable group. The goal of this paper is to investigate the problem of surjective zero products preserving maps from the Fourier algebra of $G$ into a completely contractive Banach algebra. We show that if $B$ is a completely contractive Banach algebra which is faithful and factors weakly, then every surjective completely bounded linear map from $A(G)$ into $B$ which preserves zero products is a weighted homomorphism. Moreover an equivalent condition is given for such a map to be a homomorphism. In particular, this result implies that if $B$ is a commutative C$^*$-algebra or a matrix space and $T:A(G)\rightarrow B$ is a continuous surjective linear map which preserves zero products, then $T$ is a weighted homomorphism and there is an equivalent condition for $T$ to be a homomorphism.

K-POTENT PRESERVING LINEAR MAPS