Search results for "Matematica"
showing 10 items of 1637 documents
MR3085505 Reviewed Boonpogkrong, Varayu Stokes' theorem on manifolds: a Kurzweil-Henstock approach. Taiwanese J. Math. 17 (2013), no. 4, 1183–1196
2013
Speeds of discontinuity waves in turbulent superfluids
2012
In this work, using a hydrodynamical model previously formulated, the possible modes of propagation of discontinuity waves in turbulent superfluids are studied in the nonlinear regimes. The field equations are written down, then the wave speeds are determined in a constant state.
MR3091813 Botelho, Fernanda; Jamison, James; Molnár, Lajos Surjective isometries on Grassmann spaces. J. Funct. Anal. 265 (2013), no. 10, 2226–2238. …
2014
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.
Generalized Weyl's theorem and quasi-affiniy.
2010
A bounded operator T in L(X) acting on a Banach space X is said to satisfy generalized Weyl's theorem if the complement in the spectrum of the B-Weyl spectrum is the set of all eigenvalues which are isolated points of the spectrum. In this paper we prove that generalized Weyl's theorem holds for several classes of operators, extending previous results obtained in [24] and [15]. We also consider the preservation of generalized Weyl's theorem between two operators T in L(X), S in L(Y ) in the case that these are intertwined by a quasi-affinity A in L(X; Y ), or in the more general case that T and S are asymptotically intertwined by A.
MR2370688 (2009e:46013) Navarro-Pascual, J. C.; Mena-Jurado, J. F.; Sánchez-Lirola, M. G. A two-dimensional inequality and uniformly continuous retra…
2009
Let X be an infinite-dimensional uniformly convex Banach space and let BX and SX be its closed unit ball and unit sphere, respectively. The main result of the paper is that the identity mapping on BX can be expressed as the mean of n uniformly continuous retractions from BX onto SX for every n >= 3. Then, the authors observe that the result holds under a property weaker than uniform convexity, satisfied by any complex Banach space, so that the result generalizes that of [A. Jim´enez-Vargas et al., Studia Math. 135 (1999), no. 1, 75–81; MR1686372 (2000b:46025)]. As an application the extremal structure of spaces of vector-valued uniformly continuous mappings is studied.
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.
On some parameters related to weak noncompactness in L1(μ,E)
2009
A measure of weak noncompactness γU is defined in a Banach space X in terms of convex compactness. We obtain relationships between the measure γU(A) of a bounded set A in the Bochner space L1(μ,E) and two parameters Π(A) and Λ1(A) related, respectively, to uniform integrability and weak-tightness. The criterion for relative weak compactness in L1(μ,E) is recovered.
Optimization Problems via Best Proximity Point Analysis
2014
Many problems arising in different areas of mathematics, such as optimization, variational analysis, and differential equations, can be modeled as equations of the form Tx=x, where T is a given mapping in the framework of a metric space. However, such equation does not necessarily possess a solution if T happens to be nonself-mapping. In such situations, one speculates to determine an approximate solution x (called a best proximity point) that is optimal in the sense that the distance between x and Tx is minimum. The aim of best proximity point analysis is to provide sufficient conditions that assure the existence and uniqueness of a best proximity point. This special issue is focused on th…