arXiv subjects

Marko Nedeljkov

Publications and source records attributed to Marko Nedeljkov.

10 recordsLinked to original sources

arXiv2026

Maximal entropy dissipation numerical scheme for conservation law systems

This paper presents a numerical finite volume method for conservation law systems that are adapted to the principle of maximal dissipation. The general assumptions are the existence of a strictly convex entropy functional and the finite propagation speed property of a given system. The procedure is based on a numerical flux construction obtained by the minimization of the entropy functional in each time step. The scheme satisfies assumptions of the Lax-Wendroff theorem. A limiting solution obtained by this scheme is compared with the classical weak solutions obtained by the Glimm or the Wave Front Tracking algorithm for one-dimensional systems.

math.NA↗

arXiv2025

Spherically symmetric collapsing solution in the form of shadow wave

This paper deals with isothermal Euler-Poisson system which is used to model collapse of self-gravitating Newtonian star. Density dependent viscosity term is added on the right-hand side of momentum equation and it has been proved that there exists stable shadow wave solution with unbounded density at the origin. This results is extended to the vanishing pressure case.

math.AP↗

arXiv2025

Maximal dissipation and shallow water flow -- the dam-break problem

The shallow water system with a bed jump describes a fluid flow over a dam, represented by a simple step function with the Riemann initial data is such that the vacuum is on the right-hand side. The main question is whether the fluid will stay on the left-hand side of the dam. After approximating the step function space derivative with a fixed shadow wave, solutions to that problem stay bounded. A proper connection between waves on both sides of the dam, and a unique solution afterward is found by using the maximal dissipation principle.

math.AP↗

arXiv2021

Shadow wave solutions for a scalar two-flux conservation law with Rankine-Hugoniot deficit

The paper deals with scalar conservation laws having a flux discontinuity at $x=0$ without a weak solution that satisfies the classical Rankine--Hugoniot jump condition at $x=0$. We are using unbounded solutions in the form of shadow waves supported by the origin for solving that problem. The shadow waves are nets of piecewise constant functions approximating a shock wave with added a delta function and sometimes another unbounded part.

math.AP↗

arXiv2020

Energy dissipation admissibility condition for conservation law systems admitting singular solutions

The main goal of the paper is to define and use a condition sufficient to choose a unique solution to conservation law systems with a singular measure in initial data. Different approximations can lead to solutions with different distributional limits. The new notion called backward energy condition is then to single out a proper approximation of the distributional initial data. The definition is based on the maximal energy dissipation defined in \cite{CD_1973}. Suppose that a conservation law system admits a supplementary law in space--time divergent form where the time component is a (strictly or not) convex function. It could be an energy density or a mathematical entropy in gas dynamic models, for example. One of the admissibility conditions is that a proper weak solution should maximally dissipate the energy or the mathematical entropy. We show that it is consistent with other admissibility conditions in the case of Riemann problems for systems of isentropic gas dynamics with non-positive pressure in the first part of the paper. Singular solutions to these systems are described by shadow waves, nets of piecewise constant approximations with respect to the time variable. In the second part, we define and apply the backward energy condition for those systems when the initial data contains a delta measure approximated by piecewise constant functions.

math.AP↗

arXiv2020

Shadow wave tracking procedure and initial data problem for pressureless gas model

In this paper the new procedure for a construction of an approximated solution to initial data problem for one-dimensional pressureless gas dynamics system is introduced. The procedure is based on solving the Riemann problems and tracking singular wave interactions. For that system the new problem with initial data containing Dirac delta function is solved whenever two waves interact. Use of the shadow waves as singular solutions to such problems enables us to easily solve the interaction problems. That permits us to make a simple extension of the well known Wave Front Tracking algorithm. A non-standard part of the new algorithm is dealing with delta functions as a part of a solution. In the final part of the paper we show that the approximated solution has a subsequence converging to a signed Radon measure.

math.AP↗

arXiv2017

Radially symmetric shadow wave solutions to the system of pressureless gas dynamics in arbitrary dimensions

Radially symmetric shadow wave solutions to the system of multidimensional pressureless gas dynamics are introduced, which allow one to capture concentration of mass. The transformation to a one-dimensional system with source terms is performed and physically meaningful boundary conditions at the origin are determined. Entropy conditions are derived and applied to single out physical (nonnegative mass) and dissipative (entropic) solutions. A complete solution to the pseudo-Riemann problem with initial data exhibiting a single shock on a sphere is obtained.

math.AP↗

arXiv2009

Delta shock wave interactions via wave front tracking method

In this paper we discuss delta shock interaction problem for a pressureless gas dynamics system with two different ways of approaching the subject. The first one is by using shadow wave solution concept. The result of two delta shock interactions is delta shock with non-constant speed in a general case. The second one is by perturbing the system with a small pressure term. The obtained perturbed system is strictly hyperbolic and its Riemann problem is solvable. We compare a limit of a numerical wave front tracking results as small pressure term vanishes with the shadow wave solution. Key words: weighted shadow waves, delta shock waves, wave front tracking, Riemann problem, interactions

math.AP↗

arXiv2006

Delta shock wave and interactions in a simple model case

The notion of a delta shock wave and a singular shock wave was introduced and employed by different authors, and it was shown that a large class of Riemann problems can be solved globally with these additional building blocks. The aim of this paper is to study the interaction of one type of these new solutions, the delta shock waves, with the classical types of solutions. Our model problem is $2 \times 2$ system derived from a simplified model of magneto-hydrodynamics. The solution concept used in the present paper can be simply described as analogous to the standard one but with $L^{\infty}$-functions substituted by measures in one component of a solution. Here, the delta function is represented by so called two sided delta function. We shall mention only two specific details from the complete interaction result. In some situation the interaction result may contain non-overcompressible delta shock wave called delta contact discontinuity. During delta shock and rarefaction wave interaction it may happen that some $L_{loc}^{1}$-function appear.

math.AP↗

arXiv2006

Singular shock waves in interactions

n a number of papers it was shown that there are one-dimensional systems such that they contain solutions with, so called, overcompressive singular shock waves besides the usual elementary waves (shock and rarefaction ones as well as contact discontinuities). One can see their definition for a general 2 $\times$ 2 system with fluxes linear in one of dependent variables in \cite{Ned1}. This paper is devoted to examining their interactions with themselves and elementary waves. After a discussion of systems given in a general form, a complete analysis will be given for the ion-acoustic system.

math.AP↗