The symbiotic branching model describes the evolution of two interacting populations and if started with complementary Heaviside functions, the interface where both populations are present remains compact. In this paper, we show tightness of the diffusively rescaled solutions and thus provide a first step towards a scaling limit for the interface. The crucial estimate involves a mixed fourth mo...

Problems of optimal control of movable lumped sources in distributed systems when controls belong to the classes of impulsive, piecewise constant, and Heaviside functions are considered in the paper. The optimal control problems are investigated for various cases, according to the position of the sources. Necessary optimality conditions are obtained for optimal control problems considered on al...

The contribution deals with use of overcomplete models and sparse parameter estimation for change point detection in one–dimensional stochastic processes. These processes are estimated by ’Heaviside’ functions. The BASIS PURSUIT algorithm is used to get sparse parameter estimation. The mentioned method of change point detection in stochastic processes is compared with standard methods by simula...

This article is concerned with the rigorous validation of anomalous spreading speeds in a system of coupled Fisher-KPP equations of cooperative type. Anomalous spreading refers to a scenario wherein the coupling of two equations leads to faster spreading speeds in one of the components. The existence of these spreading speeds can be predicted from the linearization about the unstable state. We ...

We study the nonlinear elliptic problem with discontinuous nonlinearity −∆u = f(u)H(u− μ) in Ω, u = h on ∂Ω, where H is the Heaviside unit function, f, h are given functions and μ is a positive real parameter. The domain Ω is the unit ball in Rn with n ≥ 3. We show the existence of a positive solution u and a hypersurface separating the region where −∆u = 0 from the region where −∆u = f(u). Our...

A subdomain variational inequality and its meshless linear complementary formulation are developed in the present paper for solving two-dimensional contact problems. The subdomain variational inequality will be defined in detail. The meshless method is based on a local weighted residual method with the Heaviside step function as the weighting function over a local subdomain and radial basis fun...

We study the asymptotic behavior of the wave function in a simple one dimensional model of ionization by pulses, in which the time-dependent potential is of the form V (x, t) = −2δ(x)(1 − e cosωt), where δ is the Dirac distribution. We find the ionization probability in the limit t → ∞ for all λ and ω. The long pulse limit is very singular, and, for ω = 0, the survival probability is const λ, m...

We propose the use of Heaviside transform with respect to the quark mass to investigate dynamical aspects of QCD. We show that at large momentum transfer the transformed propagator of massive quarks behaves softly and thus the dominant effect of explicit chiral symmetry breaking disappears through Heaviside transform. This suggests that the massless approximation would be more convenient to do ...