16,433 research outputs found
Three nontrivial solutions for the p-Laplacian Neumann problems with a concave nonlinearity near the origin
No full textWe consider a nonlinear Neumann problem driven by the p-
Laplacian, with a right-hand side nonlinearity which is concave near the
origin. Using variational techniques, combined with the method of upper-lower
solutions and with Morse theory, we show that the problem has at least three
nontrivial smooth solutions, two of which have a constant sign (one positive
and one negative).FCTPOCI/MAT/55524/200
Mean Curvature Flow with a Neumann Boundary Condition in Flat Spaces
No full textIn this thesis I study mean curvature flow in both Euclidean and Minkowski space with a Neumann boundary condition. In Minkowski space I show that for a convex timelike cone boundary condition, with compatible spacelike initial data, mean curvature flow with a perpendicular Neumann boundary condition exists for all time. Furthermore, by a blowdown argument I show convergence as t →∞ to a homothetically expanding hyperbolic hyperplane. I also study the case of graphs over convex domains in Minkowski space. I obtain long time existence for spacelike initial graphs which are taken by mean curvature flow with a Neumann boundary condition to a constant function as t →∞. In Euclidean space I consider boundary manifolds that are rotational tori where I write t for the unit vector field in the direction of the rotation. If the initial manifold M₀ is compatible with the boundary condition, and at no point has t as a tangent vector, then mean curvature flow with a perpendicular Neumann boundary condition exists for all time and converges to a flat cross-section of the boundary torus. I also discuss other constant angle boundary conditions
The Neumann problem for quasilinear differential equations
No full textsummary:In this note we prove the existence of extremal solutions of the quasilinear Neumann problem , a.e. on , , in the order interval , where and are respectively a lower and an upper solution of the Neumann problem
Robert Neumann: Mit eigener Feder
No full textRobert Neumann (1897–1957, Austrian exiled author and Vicepresidet of the PEN International, was even a disputatious antifascist political writer. His essays, his letters and biograpical documents give a vivid portrait of the diversity of literary life in Germay and Austria (before 1933/after 1958) and of exile in England (1933–1958).Der österreichische Schriftsteller Robert Neumann (1897–1975), Exilant und Vizepräsident des PEN International, war auch ein streitbarer antifaschistischer Publizist. Seine politisch-literarischen Aufsätze, seine Briefe und biographischen Dokumente ergeben ein lebendiges und facettenreiches Bild des literarischen Lebens in Deutschland und Österreich (vor 1933/nach 1958) und des Exils in England (1933–1958)
Equilibrio competitivo y soportes del crecimiento en el modelo de Von Neumann
No full textThis paper shows the existence of a reproducible competitive equilibrium in the general Von Neumann growth model, extending in this way a result due to Roemer.
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Generalised Dirichelt-to-Neumann map in time dependent domains
No full textWe study the heat, linear Schrodinger and linear KdV equations in the domain l(t) < x < ∞, 0 < t < T, with prescribed initial and boundary conditions and with
l(t) a given differentiable function. For the first two equations, we show that the unknown Neumann or Dirichlet boundary value can be computed as the solution of a
linear Volterra integral equation with an explicit weakly singular kernel. This integral equation can be derived from the formal Fourier integral representation of the solution.
For the linear KdV equation we show that the two unknown boundary values can be computed as the solution of a system of linear Volterra integral equations with explicit
weakly singular kernels. The derivation in this case makes crucial use of analyticity and certain invariance properties in the complex spectral plane.
The above Volterra equations are shown to admit a unique solution
The von Neumann Model and the Early Models of General Equilibrium
No full textThe paper reconstructs the von Neumann model, comments on its salient features and critically reviews some of its generalisations. The issues related to thetreatment of consumption, decomposability and uniqueness of the rate of growth and interest will be especially scrutinised. The most prominent models of general equilibrium that appeared before or roughly at the same time as von Neumann's model will be also reviewed in the paper and compared with it. It will be demonstrated that none of them had any noticeable influence on von Neumann's model, which is genuinely distinct, ideologically free and methodologically fresh and forward-looking. It will be argued that the model can be viewed as a brilliant mathematical metaphor of some deep-rooted old vision, pertaining to the core issues of commodity production
A comparison of deflation and the balancing Neumann-Neumann preconditioner
No full textIn this paper we compare various preconditioners for the numerical solution of partial differential equations. We compare the well-known balancing Neumann Neumann preconditioner used in domain decomposition methods with a so-called deflation preconditioner. We prove that the effective condition number of the deflated preconditioned system is always, i.e. for all deflation vectors and all restrictions and prolongations, below the condition number of the system preconditioned by the balancing Neumann-Neumann preconditioner. Even more, we establish that both preconditioners lead to almost the same spectra. The zero eigenvalues of the deflation preconditioned system are replaced by eigenvalues which are one if the balancing Neumann-Neumann preconditioner is used. Moreover, we proved that the A-norm of the errors of the iterates build by the deflation preconditioner is always below the A-norm of the errors of the iterates build by the balancing Neumann-Neumann preconditioner. Additionally, the amount of work of one iteration of the de ation preconditioned system is less than the amount of work of one iteration of the balancing Neumann-Neumann preconditioned system. Finally, we establish that the deflation preconditioner and the balancing Neumann-Neumann preconditioner produces the same iterates if one uses certain starting vectors. Numerical results for porous media flows emphasize the theoretical results.Electrical Engineering, Mathematics and Computer Scienc
Mesh-based numerical implementation of the localized boundary-domain integral equation method to a variable-coefficient Neumann problem
No full textAn implementation of the localized boundary-domain integral-equation (LBDIE) method for the numerical solution of the Neumann boundary-value problem for a second-order linear elliptic PDE with variable coefficient is discussed. The LBDIE method uses a specially constructed localized parametrix (Levi function) to reduce the BVP to a LBDIE. After employing a mesh-based discretization, the integral equation is reduced to a sparse system of linear algebraic equations that is solved numerically. Since the Neumann BVP is not unconditionally and uniquely solvable, neither is the LBDIE. Numerical implementation of the finite-dimensional perturbation approach that reduces the integral equation to an unconditionally and uniquely solvable equation, is also discussed
Irrational behavior in the Brown-von Neumann-Nash dynamics
No full textWe present a class of games with a pure strategy being strictly dominated by another pure strategy such that the former survives along most solutions of the Brown-von Neumann-Nash dynamics.Nash map, BNN dynamics, Dominated strategies
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