55 citations · 72 across the 9 of their papers we have counts for
10 papers
Reduced Sum Implementation of the BURA Method for Spectral Fractional Diffusion Problems
Stanislav Harizanov, Nikola Kosturski, Ivan Lirkov +2
The numerical solution of spectral fractional diffusion problems in the form is studied, where is a selfadjoint elliptic operator in a bounded do…
A Survey on Numerical Methods for Spectral Space-Fractional Diffusion Problems
Stanislav Harizanov, Raytcho Lazarov, Svetozar Margenov
The survey is devoted to numerical solution of the fractional equation , , where is a symmetric positive definite operator corresponding to a second order elli…
Spectral Fractional Laplacian with Inhomogeneous Dirichlet Data: Questions, Problems, Solutions
Stanislav Harizanov, Svetozar Margenov, Nedyu Popivanov
In this paper we discuss the topic of correct setting for the equation , with . The definition of the fractional Laplacian on the whole space , $n=…
Mathematical and Computer Modeling of COVID-19 Transmission Dynamics in Bulgaria by Time-depended Inverse SEIR Model
Svetozar Margenov, Nedyu Popivanov, Iva Ugrinova +2
In this paper we explore a time-depended SEIR model, in which the dynamics of the infection in four groups from a selected target group (population), divided according to the infec…
The Best Uniform Rational Approximation: Applications to Solving Equations Involving Fractional powers of Elliptic Operators
Stanislav Harizanov, Raytcho Lazarov, Svetozar Margenov +1
In this paper we consider one particular mathematical problem of this large area of fractional powers of self-adjoined elliptic operators, defined either by Dunford-Taylor-like int…
Analysis of numerical methods for spectral fractional elliptic equations based on the best uniform rational approximation
Stanislav Harizanov, Raytcho Lazarov, Pencho Marinov +2
Here we study theoretically and compare experimentally an efficient method for solving systems of algebraic equations, where the matrix comes from the discretization of a fractiona…
Comparison analysis on two numerical methods for fractional diffusion problems based on rational approximations of
Stanislav Harizanov, Raytcho Lazarov, Pencho Marinov +2
We discuss, study, and compare experimentally three methods for solving the system of algebraic equations , , where is a symmetric a…
Positive approximations of the inverse of fractional powers of SPD M-matrices
Stanislav Harizanov, Svetozar Margenov
This study is motivated by the recent development in the fractional calculus and its applications. During last few years, several different techniques are proposed to localize the…
Optimal Solvers for Linear Systems with Fractional Powers of Sparse SPD Matrices
Stanislav Harizanov, Raytcho Lazarov, Pencho Marinov +2
In this paper we consider efficient algorithms for solving the algebraic equation , , where is a symmetric and positive defini…
Preconditioning of weighted H(div)-norm and applications to numerical simulation of highly heterogeneous media
Johannes Kraus, Raytcho Lazarov, Maria Lymbery +2
In this paper we propose and analyze a preconditioner for a system arising from a finite element approximation of second order elliptic problems describing processes in highly het-…