Solving Elliptic Problems by the Domain Decomposition Method Using Proconditioning Matrices Derived by Multilevel Splitting of the Finite Element Matrix. - Raytcho D. Lazarov; Panayot S. Vassilevski; Svetozar Margenov (ICS, 1987)

Finite difference schemes on grids with local refinement in time and space for parabolic problems I. Derivation, stability, and error analysis. - Richard E. Ewing; Raytcho D. Lazarov; Panayot S. Vassilevski (Computing, 1990)

Finite Difference Schemes on Triangular Cell-Centered Grids with Local Refinement. - Panayot S. Vassilevski; Svetozara I. Petrova; Raytcho D. Lazarov (SIAM J. Sci. Comput., 1992)

Convergence analysis of least-squares mixed finite elements. - Atanas I. Pehlivanov; Graham F. Carey; Raytcho D. Lazarov; Y. Shen (Computing, 1993)

Local refinement techniques for elliptic problems on cell-centered grids; II. Optimal order two-grid iterative methods. - Richard E. Ewing; Raytcho D. Lazarov; Panayot S. Vassilevski (Numer. Linear Algebra Appl., 1994)

Domain decomposition algorithms for mixed methods for second-order elliptic problems. - Zhangxin Chen; Richard E. Ewing; Raytcho D. Lazarov (Math. Comput., 1996)

Multilevel Preconditioners for Mixed Methods for Second Order Elliptic Problems. - Zhangxin Chen; Richard E. Ewing; Raytcho D. Lazarov; Serguei Maliassov; Yuri A. Kuznetsov (Numer. Linear Algebra Appl., 1996)

Preconditioning Mixed Finite Element Saddle-point Elliptic Problems. - Panayot S. Vassilevski; Raytcho D. Lazarov (Numer. Linear Algebra Appl., 1996)

A least-squares approach based on a discrete minus one inner product for first order systems. - James H. Bramble; Raytcho D. Lazarov; Joseph E. Pasciak (Math. Comput., 1997)

Mixed Finite Element Methods for Elliptic Problems on Non-Matching Grids. - Raytcho D. Lazarov; Joseph E. Pasciak; Panayot S. Vassilevski (LSSC, 1999)

Finite Volume Element Approximations of Nonlocal in Time One-Dimensional Flows in Porous Media. - Richard E. Ewing; Raytcho D. Lazarov; Yanping Lin (Computing, 2000)

Iterative solution of a coupled mixed and standard Galerkin discretization method for elliptic problems. - Raytcho D. Lazarov; Joseph E. Pasciak; Panayot S. Vassilevski (Numer. Linear Algebra Appl., 2001)

Multiplier Spaces for the Mortar Finite Element Method in Three Dimensions. - Chisup Kim; Raytcho D. Lazarov; Joseph E. Pasciak; Panayot S. Vassilevski (SIAM J. Numer. Anal., 2001)

A Modified Finite Volume Approximation of Second-Order Elliptic Equations with Discontinuous Coefficients. - Richard E. Ewing; Oleg P. Iliev; Raytcho D. Lazarov (SIAM J. Sci. Comput., 2001)

On a Two-Level Parallel MIC(0) Preconditioning of Crouzeix-Raviart Non-conforming FEM Systems. - Raytcho D. Lazarov; Svetozar Margenov (Numerical Methods and Application, 2002)

Virtual Telemetry for Dynamic Data-Driven Application Simulations. - Craig C. Douglas; Yalchin Efendiev; Richard E. Ewing; Raytcho D. Lazarov; Martin J. Cole; Greg Jones; Chris R. Johnson 001 (International Conference on Computational Science, 2003)

Almost optimal interior penalty discontinuous approximations of symmetric elliptic problems on non-matching grids. - Raytcho D. Lazarov; Joseph E. Pasciak; Joachim Schöberl; Panayot S. Vassilevski (Numerische Mathematik, 2003)

A Note on Data-Driven Contaminant Simulation. - Craig C. Douglas; Chad E. Shannon; Yalchin Efendiev; Richard E. Ewing; Victor Ginting; Raytcho D. Lazarov; Martin J. Cole; Greg Jones; Chris R. Johnson 001; Jennifer Simpson (International Conference on Computational Science, 2004)

Multiscale Interpolation, Backward in Time Error Analysis for Data-Driven Contaminant Simulation. - Craig C. Douglas; Yalchin Efendiev; Richard E. Ewing; Victor Ginting; Raytcho D. Lazarov; Martin J. Cole; Greg Jones; Chris R. Johnson 001 (International Conference on Computational Science (2), 2005)

Postprocessing and Improved Accuracy of the Lowest-Order Mixed Finite Element Approximation for Biharmonic Eigenvalues. - Andrey B. Andreev; Raytcho D. Lazarov; Milena R. Racheva (LSSC, 2005)

Higher-order finite element methods. - Raytcho D. Lazarov (Math. Comput., 2005)

A finite volume element method for a non-linear elliptic problem. - Panagiotis Chatzipantelidis; Victor Ginting; Raytcho D. Lazarov (Numer. Linear Algebra Appl., 2005)

Explicit and Averaging A Posteriori Error Estimates for Adaptive Finite Volume Methods. - Carsten Carstensen; Raytcho D. Lazarov; Stanimire Tomov (SIAM J. Numer. Anal., 2005)

Error Estimates for a Finite Volume Element Method for Elliptic PDEs in Nonconvex Polygonal Domains. - Panagiotis Chatzipantelidis; Raytcho D. Lazarov (SIAM J. Numer. Anal., 2005)

Dynamic Contaminant Identification in Water. - Craig C. Douglas; J. Clay Harris; Mohamed Iskandarani; Chris R. Johnson 001; Robert A. Lodder; Steven G. Parker; Martin J. Cole; Richard E. Ewing; Yalchin Efendiev; Raytcho D. Lazarov; Guan Qin (International Conference on Computational Science (3), 2006)

Dynamic Data Driven Simulations in Stochastic Environments. - Craig C. Douglas; Yalchin Efendiev; Richard E. Ewing; Victor Ginting; Raytcho D. Lazarov (Computing, 2006)

Two-level preconditioning of discontinuous Galerkin approximations of second-order elliptic equations. - Veselin Dobrev; Raytcho D. Lazarov; Panayot S. Vassilevski; Ludmil T. Zikatanov (Numer. Linear Algebra Appl., 2006)

On the occasion of the sixtieth birthday of Richard E. Ewing. - Raytcho D. Lazarov; Joseph E. Pasciak; Guan Qin (Numer. Linear Algebra Appl., 2006)

Some new error estimates of a semidiscrete finite volume element method for a parabolic integro-differential equation with nonsmooth initial data. - Rajen Kumar Sinha; Richard E. Ewing; Raytcho D. Lazarov (SIAM J. Numer. Anal., 2006)

CBS constants for multilevel splitting of graph-Laplacian and application to preconditioning of discontinuous Galerkin systems. - Raytcho D. Lazarov; Svetozar Margenov (J. Complex., 2007)

On the balancing principle for some problems of Numerical Analysis. - Raytcho D. Lazarov; Shuai Lu; Sergei V. Pereverzev (Numerische Mathematik, 2007)

Discontinuous Galerkin Subgrid Finite Element Method for Heterogeneous Brinkman's Equations. - Oleg P. Iliev; Raytcho D. Lazarov; Joerg Willems (LSSC, 2009)

Unified Hybridization of Discontinuous Galerkin, Mixed, and Continuous Galerkin Methods for Second Order Elliptic Problems. - Bernardo Cockburn; Jayadeep Gopalakrishnan; Raytcho D. Lazarov (SIAM J. Numer. Anal., 2009)

Mixed Finite Element Approximations of Parabolic Integro-Differential Equations with Nonsmooth Initial Data. - Rajen Kumar Sinha; Richard E. Ewing; Raytcho D. Lazarov (SIAM J. Numer. Anal., 2009)

A Simplified Method for Upscaling Composite Materials with High Contrast of the Conductivity. - Richard E. Ewing; Oleg Iliev 001; Raytcho D. Lazarov; Irina Rybak; Joerg Willems (SIAM J. Sci. Comput., 2009)

Least squares approach for initial data recovery in dynamic data-driven applications simulations. - Craig C. Douglas; Yalchin Efendiev; Richard E. Ewing; Victor Ginting; Raytcho D. Lazarov; Martin J. Cole; Greg Jones (Comput. Vis. Sci., 2010)

Fast numerical upscaling of heat equation for fibrous materials. - Oleg Iliev 001; Raytcho D. Lazarov; Joerg Willems (Comput. Vis. Sci., 2010)

Robust Solvers for Symmetric Positive Definite Operators and Weighted Poincaré Inequalities. - Yalchin Efendiev; Juan Galvis; Raytcho D. Lazarov; Joerg Willems (LSSC, 2011)

Variational Multiscale Finite Element Method for Flows in Highly Porous Media. - Oleg P. Iliev; Raytcho D. Lazarov; Joerg Willems (Multiscale Model. Simul., 2011)

Galerkin FEM for Fractional Order Parabolic Equations with Initial Data in H - s , 0 ≤ s ≤ 1. - Bangti Jin; Raytcho D. Lazarov; Joseph E. Pasciak; Zhi Zhou 002 (NAA, 2012)

Robust Two-level Domain Decomposition Preconditioners for High-contrast Anisotropic Flows in Multiscale Media. - Yalchin Efendiev; Juan Galvis; Raytcho D. Lazarov; Svetozar Margenov; Jun Ren (Comput. Methods Appl. Math., 2012)

Some error estimates for the lumped mass finite element method for a parabolic problem. - Panagiotis Chatzipantelidis; Raytcho D. Lazarov; Vidar Thomée (Math. Comput., 2012)

Mixed FEM for Second Order Elliptic Problems on Polygonal Meshes with BEM-Based Spaces. - Yalchin Efendiev; Juan Galvis; Raytcho D. Lazarov; Steffen Weißer (LSSC, 2013)

Some Error Estimates for the Finite Volume Element Method for a Parabolic Problem. - Panagiotis Chatzipantelidis; Raytcho D. Lazarov; Vidar Thomée (Comput. Methods Appl. Math., 2013)

Generalized multiscale finite element method. Symmetric interior penalty coupling. - Yalchin Efendiev; Juan Galvis; Raytcho D. Lazarov; M. Moon; Marcus Sarkis (J. Comput. Phys., 2013)

Error Estimates for a Semidiscrete Finite Element Method for Fractional Order Parabolic Equations. - Bangti Jin; Raytcho D. Lazarov; Zhi Zhou 002 (SIAM J. Numer. Anal., 2013)

Multiscale Domain Decomposition Preconditioners for Anisotropic High-Contrast Problems. - Yalchin Efendiev; Juan Galvis; Raytcho D. Lazarov; Svetozar Margenov; Jun Ren (Domain Decomposition Methods in Science and Engineering XX, 2013)

Error Analysis of a Finite Element Method for the Space-Fractional Parabolic Equation. - Bangti Jin; Raytcho D. Lazarov; Joseph E. Pasciak; Zhi Zhou 002 (SIAM J. Numer. Anal., 2014)

The Galerkin finite element method for a multi-term time-fractional diffusion equation. - Bangti Jin; Raytcho D. Lazarov; Yikan Liu; Zhi Zhou 002 (J. Comput. Phys., 2015)

Variational formulation of problems involving fractional order differential operators. - Bangti Jin; Raytcho D. Lazarov; Joseph E. Pasciak; William Rundell (Math. Comput., 2015)

An analysis of the Rayleigh-Stokes problem for a generalized second-grade fluid. - Emilia G. Bazhlekova; Bangti Jin; Raytcho D. Lazarov; Zhi Zhou 002 (Numerische Mathematik, 2015)

A Multiscale HDG Method for Second Order Elliptic Equations. Part I. Polynomial and Homogenization-Based Multiscale Spaces. - Yalchin Efendiev; Raytcho D. Lazarov; Ke Shi 005 (SIAM J. Numer. Anal., 2015)

Multiscale direction-splitting algorithms for parabolic equations with highly heterogeneous coefficients. - Shriram Srinivasan; Raytcho D. Lazarov; Peter D. Minev (Comput. Math. Appl., 2016)

A simple finite element method for boundary value problems with a Riemann-Liouville derivative. - Bangti Jin; Raytcho D. Lazarov; Xiliang Lu; Zhi Zhou 002 (J. Comput. Appl. Math., 2016)

A Petrov-Galerkin Finite Element Method for Fractional Convection-Diffusion Equations. - Bangti Jin; Raytcho D. Lazarov; Zhi Zhou 002 (SIAM J. Numer. Anal., 2016)

Two Fully Discrete Schemes for Fractional Diffusion and Diffusion-Wave Equations with Nonsmooth Data. - Bangti Jin; Raytcho D. Lazarov; Zhi Zhou 002 (SIAM J. Sci. Comput., 2016)

Preconditioning Heterogeneous H(div) Problems by Additive Schur Complement Approximation and Applications. - Johannes K. Kraus; Raytcho D. Lazarov; Maria Lymbery; Svetozar Margenov; Ludmil T. Zikatanov (SIAM J. Sci. Comput., 2016)

Preface: Numerical Analysis of Fractional Differential Equations. - Bangti Jin; Raytcho D. Lazarov; Petr N. Vabishchevich (Comput. Methods Appl. Math., 2017)

Geometric Multigrid for Darcy and Brinkman models of flows in highly heterogeneous porous media: A numerical study. - Guido Kanschat; Raytcho D. Lazarov; Youli Mao (J. Comput. Appl. Math., 2017)

On nonnegativity preservation in finite element methods for subdiffusion equations. - Bangti Jin; Raytcho D. Lazarov; Vidar Thomée; Zhi Zhou 002 (Math. Comput., 2017)

Space-Time Petrov-Galerkin FEM for Fractional Diffusion Problems. - Beiping Duan; Bangti Jin; Raytcho D. Lazarov; Joseph E. Pasciak; Zhi Zhou 002 (Comput. Methods Appl. Math., 2018)

A note on the uniform inf-sup condition for the Brinkman problem in highly heterogeneous media. - Raytcho D. Lazarov; Aziz Takhirov (J. Comput. Appl. Math., 2018)

Optimal solvers for linear systems with fractional powers of sparse SPD matrices. - Stanislav Harizanov; Raytcho D. Lazarov; Svetozar Margenov; Pencho Marinov; Yavor Vutov (Numer. Linear Algebra Appl., 2018)

The Best Uniform Rational Approximation: Applications to Solving Equations Involving Fractional powers of Elliptic Operators. - Stanislav Harizanov; Raytcho D. Lazarov; Svetozar Margenov; Pencho Marinov (CoRR, 2019)

Numerical solution of fractional diffusion-reaction problems based on BURA. - Stanislav Harizanov; Raytcho D. Lazarov; Svetozar Margenov; Pencho Marinov (Comput. Math. Appl., 2020)

Modern Problems of Numerical Analysis. On the Centenary of the Birth of Alexander Andreevich Samarskii. - Raytcho D. Lazarov; Piotr P. Matus; Petr N. Vabishchevich (Comput. Methods Appl. Math., 2020)

A Survey on Numerical Methods for Spectral Space-Fractional Diffusion Problems. - Stanislav Harizanov; Raytcho D. Lazarov; Svetozar Margenov (CoRR, 2020)

Analysis of numerical methods for spectral fractional elliptic equations based on the best uniform rational approximation. - Stanislav Harizanov; Raytcho D. Lazarov; Svetozar Margenov; Pencho Marinov; Joseph E. Pasciak (J. Comput. Phys., 2020)