arXiv subjects

Samuele Ferri

Publications and source records attributed to Samuele Ferri.

3 recordsLinked to original sources

arXiv2026

Dissolution of carbonate stones caused by CO2 pollutant: an erosion model

In this paper we introduce a new mathematical model describing the erosion process caused in carbonate stones by the dissolution of the porous matrix due to the penetration of carbonic acid present in the environment. Such model is formulated as nonlinear reaction-transport system in porous media governed by Darcy flow. We propose a numerical algorithm based on finite difference approximation that relies on level-set method at the boundaries and we show numerical tests that are in accordance with the literature in terms of the advancement of the erosion front.

math.NA↗

arXiv2025

Spectral analysis of the stiffness matrix sequence in the approximated Stokes equation

In the present paper, we analyze in detail the spectral features of the matrix sequences arising from the Taylor-Hood $\mathbb{P}_2$-$\mathbb{P}_1$ approximation of variable viscosity for $2d$ Stokes problem under weak assumptions on the regularity of the diffusion. Localization and distributional spectral results are provided, accompanied by numerical tests and visualizations. A preliminary study of the impact of our findings on the preconditioning problem is also presented. A final section with concluding remarks and open problems ends the current work.

math.NA↗

arXiv2025

Blocking structures, approximation, and preconditioning

We consider block-structured matrices $A_n$, where the blocks are of (block) unilevel Toeplitz type with $s\times t$ matrix-valued generating functions. Under mild assumptions on the size of the (rectangular) blocks, the asymptotic distribution of the singular values of {the} associated matrix-sequences is identified and, when the related singular value symbol is Hermitian, it coincides with the spectral symbol. Building on the theoretical derivations, we approximate the matrices with simplified block structures that show two important features: a) the related simplified matrix-sequence has the same distributions as $\{A_{{n}}\}_{{n}}$; b) a generic linear system involving the simplified structures can be solved in $O(n\log n)$ arithmetic operations. The two key properties a) and b) suggest a natural way for preconditioning a linear system with coefficient matrix $A_n$. Under mild assumptions, the singular value analysis and the spectral analysis of the preconditioned matrix-sequences is provided, together with a wide set of numerical experiments.

math.NA↗