Algebraic properties of Riordan subgroups

Journal of Algebraic Combinatorics - We present properties of the group structure of Riordan arrays. We examine similar properties among known Riordan subgroups, and from this, we define...     

The anti‐dissipative,non‐monotone behavior of Petrov–Galerkin upwinding

The Petrov–Galerkin method has been developed with the primary goal of damping spurious oscillations near discontinuities in advection dominated flows. For time‐dependent problems, the typical Petrov–Galerkin method is based on the minimization of the dispersion error and the simultaneous selective addition of dissipation. This optimal design helps to dampen the oscillations prevalent near discontinuities in standard Bubnov–Galerkin solutions. However, it is demonstrated that when the Courant number is less than 1, the Petrov–Galerkin method actually amplifies undershoots at the base of discontinuities. This is shown in an heuristic manner, and is demonstrated with numerical experiments with the scalar advection and Richards' equations. A discussion of monotonicity preservation as a design criterion, as opposed to phase or amplitude error minimization, is also presented. The Petrov–Galerkin method is further linked to the high‐resolution, total variation diminishing (TVD) finite volume method in order to obtain a monotonicity preserving Petrov–Galerkin method.     

ON NONLINEAR ELLIPTIC HEMIVARIATIONAL INEQUALITIES OF SECOND ORDER

In this paper, a nonlinear hemivariational inequality of second order with a forcing term of subcritical growth is studied. Using techniques from multivalued analysis and the theory of nonlinear operators of monotone type, an existence theorem for the Dirichlet boundary value problem is proved.     

Positive solutions for nonlinear nonhomogeneous Dirichlet problems with concave-convex nonlinearities

We consider a nonlinear parametric Dirichlet equation driven by a nonhomogeneous differential operator involving a reaction exhibiting the competing effects of concave and convex terms. Using variational methods combined with truncation and comparison techniques we prove a bifurcation near zero theorem describing the dependence of the positive solutions on the parameter \(\lambda >0\).     

Multiple Solutions for Nearly Resonant Nonlinear Dirichlet Problems

In this paper we consider parametric nonlinear elliptic problems driven by the p-Laplacian differential operator and with the parameter ?? near ?? ₁, the principal eigenvalue of the negative Dirichlet p-Laplacian (near resonance). We consider both cases when ???<??? ₁ (near resonance from the left) and when ???>??? ₁ (near resonance from the right). Our approach combines variational methods based on the critical point theory, together with truncation techniques and Morse theory.     

Neumann problems resonant at zero and infinity

We consider a semilinear Neumann problem with a reaction which is resonant at both zero and ±∞. Using a combination of methods from critical point theory, together with truncation techniques, the use of upper–lower solutions and of the Morse theory (critical groups), we show that the problem has at least five nontrivial smooth solutions, four of which have constant sign (two positive and two negative).     

The evolutionary dynamics of audit

A critical issue in auditing is provisioning of reasonable assurance that the financial reports are free from material misstatements. The auditing detection problem can be viewed as a two-player game between the auditor and the auditee where the auditor aims at eliminating misstatements, reducing at the same time his audit efforts, while the auditee aims at benefiting from fraudulent financial reporting and defalcation.In this paper, the auditing/fraud detection problem is modeled employing evolutionary game theory. It is proved that, given that the players have accurate information for the parameters involved in the problem, the auditing/fraud detection game is stable but not asymptotically stable. The case of the auditor being partially informed about the auditee firm is also studied and it is concluded that if the auditor is partially informed about the auditee firm, a more comprehensive audit is necessary to guarantee quality of audit. Finally, analytical results are derived concerning the impact of audit tenure on audit quality.     

Nonsmooth generalized guiding functions for periodic differential inclusions

We consider the periodic problem for differential inclusions in $$ \user2{\mathbb{R}}^{\rm N} $$ with a nonconvex-valued orientor field F(t, ζ), which is lower semicontinuous in $$ \zeta \in \user2{\mathbb{R}}^{\rm N} $$ Using the notion of a nonsmooth, locally Lipschitz generalized guiding function, we prove that the inclusion has periodic solutions. We have two such existence theorems. We also study the “convex” periodic problem and prove an existence result under upper semicontinuity hypothesis on F(t, ·) and using a nonsmooth guiding function. Our work was motivated by the recent paper of Mawhin-Ward [23] and extends the single-valued results of Mawhin [19] and the multivalued results of De Blasi-Górniewicz-Pianigiani [4], where either the guiding function is C¹ or the conditions on F are more restrictive and more difficult to verify.     

Multiple solutions for strongly resonant nonlinear elliptic problems with discontinuities

We examine a nonlinear strongly resonant elliptic problem driven by the -Laplacian and with a discontinuous nonlinearity. We assume that the discontinuity points are countable and at them the nonlinearity has an upward jump discontinuity. We show that the problem has at least two nontrivial solutions without using a multivalued interpretation of the problem as it is often the case in the literature. Our approach is variational based on the nonsmooth critical point theory for locally Lipschitz functions.

     

Nonlinear Boundary Value Problems for Second Order Differential Inclusions

In this paper we study two boundary value problems for second order strongly nonlinear differential inclusions involving a maximal monotone term. The first is a vector problem with Dirichlet boundary conditions and a nonlinear differential operator of the form x ↦ a(x, x′)′. In this problem the maximal monotone term is required to be defined everywhere in the state space ℝ^N. The second problem is a scalar problem with periodic boundary conditions and a differential operator of the form x ↦ (a(x)x′)′. In this case the maximal monotone term need not be defined everywhere, incorporating into our framework differential variational inequalities. Using techniques from multivalued analysis and from nonlinear analysis, we prove the existence of solutions for both problems under convexity and nonconvexity conditions on the multivalued right-hand side.