Search results for "Matematica"
showing 10 items of 1637 documents
Nonlocal model of Superfluid Turbulence: Constitutive Theory
2014
In this paper, the constitutive restrictions for the fluxes in a nonlocal model of superfluid turbulence are deduced from the entropy principle, using the Liu method of Lagrange multipliers. The proposed model chooses as fundamental fields the density, the velocity, the energy density, the heat flux, and the averaged vortex line length per unit volume. The onstitutive quantities are assumed to depend on the fundamental fields and on their first derivative.
Modelling of Systems with a Dispersed Phase: “Measuring” Small Sets in the Presence of Elliptic Operators
2016
When modelling systems with a dispersed phase involving elliptic operators, as is the case of the Stokes or Navier-Stokes problem or the heat equation in a bounded domain, the geometrical structure of the space occupied by the dispersed phase enters in the homogenization process through its capacity, a quantity which can be used to define the equivalence classes in \(H^1\). We shall review the relationship between capacity and homogenization terms in the limit when the number of inclusions becomes large, focusing in particular on the situation where the distribution of inclusions is not necessarily too regular (i.e. it is not periodic).
The Heisenberg dynamics of spin systems: A quasi*‐algebras approach
1996
The problem of the existence of the thermodynamical limit of the algebraic dynamics for a class of spin systems is considered in the framework of a generalized algebraic approach in terms of a special class of quasi*-algebras, called CQ*-algebras. Physical applications to (almost) mean-field models and to bubble models are discussed. © 1996 American Institute of Physics.
Discrete KP Equation and Momentum Mapping of Toda System
2003
Abstract A new approach to discrete KP equation is considered, starting from the Gelfand-Zakhharevich theory for the research of Casimir function for Toda Poisson pencil. The link between the usual approach through the use of discrete Lax operators, is emphasized. We show that these two different formulations of the discrete KP equation are equivalent and they are different representations of the same equations. The relation between the two approaches to the KP equation is obtained by a change of frame in the space of upper truncated Laurent series and translated into the space of shift operators.
Fixed point theorems in generalized partially orderedG-metric spaces
2010
In this paper, we consider the concept of a $\Omega$-distance on a complete partially ordered G-metric space and prove some fixed point theorems.
HENSTOCK INTEGRAL AND DINI-RIEMANN THEOREM
2009
In [5] an analogue of the classical Dini-Riemann theorem related to non-absolutely convergent series of real number is obtained for the Lebesgue improper integral. Here we are extending it to the case of the Henstock integral.
Anisotropic elliptic equations with gradient-dependent lower order terms and L^1 data
2023
<abstract><p>We prove the existence of a weak solution for a general class of Dirichlet anisotropic elliptic problems such as $ \mathcal Au+\Phi(x, u, \nabla u) = \mathfrak{B}u+f $ in $ \Omega $, where $ \Omega $ is a bounded open subset of $ \mathbb R^N $ and $ f\in L^1(\Omega) $ is arbitrary. The principal part is a divergence-form nonlinear anisotropic operator $ \mathcal A $, the prototype of which is $ \mathcal A u = -\sum_{j = 1}^N \partial_j(|\partial_j u|^{p_j-2}\partial_j u) $ with $ p_j &gt; 1 $ for all $ 1\leq j\leq N $ and $ \sum_{j = 1}^N (1/p_j) &gt; 1 $. As a novelty in this paper, our lower order terms involve a new class of operators $ \mathfrak B $ such…
A C-free approach to linear ODEs with constant coefficients
2012
The purpose of this paper is to present an alternative way of establishing the general solution of the equation x''(t)+x(t)=0 without relying on complex numbers. Our method can be extended to the corresponding non-homogeneous equation and, more generally, to higher-order equations.
Linear dynamics induced by odometers
2022
Weighted shifts are an important concrete class of operators in linear dynamics. In particular, they are an essential tool in distinguishing variety dynamical properties. Recently, a systematic study of dynamical properties of composition operators on $L^p$ spaces has been initiated. This class of operators includes weighted shifts and also allows flexibility in construction of other concrete examples. In this article, we study one such concrete class of operators, namely composition operators induced by measures on odometers. In particular, we study measures on odometers which induce mixing and transitive linear operators on $L^p$ spaces.
Transition to superfluidity in liquid 4He
2012
In this work the transition from normal liquid helium I to superfluid liquid helium II, controlled by temperature and pressure, is studied in the simplified assumption of absence of viscosity. A macroscopic thermodynamical model is presented, which chooses as new independent fields the heat flux q and a phase field function f. For the heat flux a modification of Cattaneo equation is written, while for the function f a time dependent Ginzburg-Landau equation is proposed.