Search results for "Bounded"
showing 10 items of 658 documents
Topologie à l'infini et variétés à géométrie bornée
2013
We give a quick review on the asymptotic topology and the geometry of manifolds with bounded geometry, by quoting also some results obtained by the authors.
Order boundedness and spectrum in locally convex quasi *-algebras
2021
After a quick sketch of the basic aspects of locally convex quasi *-algebras, we focus on order bounded elements and use them to analyze some spectral properties, trying to generalize the approach already studied in the Banach case.
Order bounded elements of topological *-algebras
2012
Several different notions of {\em bounded} element of a topological *-algebra $\A$ are considered. The case where boundedness is defined via the natural order of $\A$ is examined in more details and it is proved that under certain circumstances (in particular, when $\A$ possesses sufficiently many *-representations) {\em order boundedness} is equivalent to {\em spectral boundedness}.
Colombeau Algebras and convolutions generated by self-adjoint operators
2017
The role of convolution of functions in the construction of Colombeau algebras of generalized functions is analyzed, with particular referring to the commutative relation with the derivation operator. The possibility to consider the A-convolution, with A an unbounded self-adjoint operator in Hilbert space, is discussed. K
MR3058477 Reviewed Ereú, Thomás; Sánchez, José L.; Merentes, Nelson; Wróbel, Małgorzata Uniformly continuous set-valued composition operators in the …
2011
In this paper it is established a property of a composition operator between spaces of functions of bounded variation in the sense of Schramm. Let X and Y be two real normed spaces, C a convex cone in X and I a closed bounded interval of the real line. Moreover let cc(Y) be the family of all non-empty closed convex and compact subsets of Y. The authors study the Nemytskij (composition) operator (HF)(t)=h(t,F(t)), where F: I \rightarrow C and h: I\times C \rightarrow cc(Y) is a given set-valued function. They show that if the Nemytskij operator $H$ is uniformly continuous and maps the space \Phi BV (I;C) of functions (from I to C) of bounded \Phi-variation in the sense of Schramm into the sp…
The completion of a C*-algebra with a locally convex topology
2006
There are examples of C*-algebras A that accept a locally convex *-topology t coarser than the given one, such that Ae[t] (the completion of A with respect to t) is a GB*-algebra. The multiplication of A[t] may be or not be jointly continuous. In the second case, Ae[t] may fail being a locally convex *-algebra, but it is a partial *-algebra. In both cases the structure and the representation theory of Ae[t] are investigated. If A[t+] denotes the t-closure of the positive cone A+ of the given C*-algebra A, then the property A[t]+ \cap (−A[t]+) = {0} is decisive for the existence of certain faithful *-representations of the corresponding *-algebra Ae[t].
MR2819034 Castillo, René Erlín The Nemytskii operator on bounded p-variation in the mean spaces. Mat. Enseñ. Univ. (N. S.) 19 (2011), no. 1, 31–41. (…
2012
The author introduces the notion of bounded $p$-variation in the sense of $L_p$-norm. Precisely: Let $f \in L_p[0,2\pi]$ with $1<p<\infty$. Let $P: 0=t_0 <t_1< \cdots <t_n=2\pi$ be a partion of $[0,2\pi]$ if $$V_p^m(f,T) = \sup \{\sum_{k=1} ^{n}\int_T\frac{|f(x+t_k)-f(x+t_{k-1})|^p)}{|t_k-t_{k-1}|^{p-1}}\}< \infty,$$ where the supremum is taken over all partitions $P$ of $[0,2\pi]$ and $T=\mathbb{R}/2\pi \mathbb{Z}$, then $f$ is said to be of bounded $p$-variation in the mean. The author obtains a Riesz type result for functions of bounded $p$-variation in the mean and gives some properties for functions of bounded $p$-variation by using the Nemytskii operator.
Faithfully representable topological *-algebras: some spectral properties
2018
A faithfully representable topological *-algebra (fr*-algebra) A0 is characterized by the fact that it possesses sufficiently many *-representations. Some spectral properties are examined, by constructing a convenient quasi *-algebra A over A0, starting from the order bounded elements of A0.
MR2789279 Aziz, Wadie; Leiva, Hugo; Merentes, Nelson; Rzepka, Beata A representation theorem for φ-bounded variation of functions in the sense of Rie…
2012
The authors consider the class $V_\varphi^R (I^b_a)$ of functions $f:I^b_a =[a_1,b_1]\times [a_2,b_2]\subset \mathbb{R}^2 \to \mathbb{R}$ with bounded $\varphi$-total variation in the sense of Riesz, where $\varphi: [0,+ \infty) \to [0,+ \infty)$ is nondecreasing and continuous with $\varphi(0)=0$ and $\varphi(t) \to +\infty$ as $t \to +\infty$. If we assume that $\varphi$ is also such that $\lim_{t \to +\infty}\frac{\varphi(t)}{t}= +\infty$, then we obtain the main result. Precisely, the authors give a characterization of function of two variables defined on a rectangle $I^b_a$ belonging to $V_\varphi^R (I^b_a)$. Clearly, this result is a generalization of the Riesz Lemma.
MR2664252 Aziz, W.; Leiva, H.; Merentes, N.; Sánchez, J. L. Functions of two variables with bounded φ-variation in the sense of Riesz. J. Math. Appl.…
2011
The authors consider the space $BV_\varphi^R (I^b_a,\mathbb{R})$ of functions $f:I^b_a =[a,b]\times [a,b]\subset \mathbb{R}^2 \to \mathbb{R}$ with a $\varphi$-bounded variation in the sense of Riesz, where $\varphi: [0,+ \infty) \to [0,+ \infty)$ is nondecreasing and continuous with $\varphi(0)=0$ and $\varphi(t) \to +\infty$ as $t \to +\infty$. The authors show that $BV_\varphi^R (I^b_a,\mathbb{R})$ is a Banach algebra. Let $h: I^b_a \times \mathbb{R} \to \mathbb{R}$ and let $H: \mathbb{R}^{I^b_a} \to \mathbb{R}$ be the composition operator associated to $h$, that is the operator defined by $(Hf)(x)= h(x, f(x))$ for each $x \in I^b_a$. Then the authors consider the problem of characterizin…