Fokas method for linear convection-diffusion equation with time-dependent coefficients and its extension to other evolution equations

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Auteurs principaux: Kalimeris, Konstantinos, Özsarı, Türker
Format: Preprint
Publié: 2025
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author Kalimeris, Konstantinos
Özsarı, Türker
author_facet Kalimeris, Konstantinos
Özsarı, Türker
contents In this paper, we study a linear convection-diffusion equation with time-dependent coefficients on a bounded interval. The problem includes inhomogeneous Dirichlet boundary conditions and is motivated by physical models where the diffusivity and transport change with time, such as heat or mass transfer in non-stationary environments. We apply and adapt the Unified Transform Method (UTM), which handles both time-varying coefficients and nonzero boundary data, to obtain an explicit integral formula for the solution. %The method allows us to handle both time-varying coefficients and nonzero boundary data by removing unknown boundary traces emerging upon finite line Fourier transform (FLFT) through a spectral symmetry argument. Next, we study well-posedness of the model in fractional Sobolev spaces and prove spatial and temporal regularity estimates. We show that the smoothing effect of the heat operator is still prevalent even when coefficients depend on time under suitable sign and growth assumptions on the coefficients. Finally, we extend this approach to obtain the solution for several evolution equations with time-dependent coefficients, in one space variable.
format Preprint
id arxiv_https___arxiv_org_abs_2510_18100
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Fokas method for linear convection-diffusion equation with time-dependent coefficients and its extension to other evolution equations
Kalimeris, Konstantinos
Özsarı, Türker
Analysis of PDEs
35A01, 35A02, 35A22, 35B65, 35C15, 35D30, 35K20
In this paper, we study a linear convection-diffusion equation with time-dependent coefficients on a bounded interval. The problem includes inhomogeneous Dirichlet boundary conditions and is motivated by physical models where the diffusivity and transport change with time, such as heat or mass transfer in non-stationary environments. We apply and adapt the Unified Transform Method (UTM), which handles both time-varying coefficients and nonzero boundary data, to obtain an explicit integral formula for the solution. %The method allows us to handle both time-varying coefficients and nonzero boundary data by removing unknown boundary traces emerging upon finite line Fourier transform (FLFT) through a spectral symmetry argument. Next, we study well-posedness of the model in fractional Sobolev spaces and prove spatial and temporal regularity estimates. We show that the smoothing effect of the heat operator is still prevalent even when coefficients depend on time under suitable sign and growth assumptions on the coefficients. Finally, we extend this approach to obtain the solution for several evolution equations with time-dependent coefficients, in one space variable.
title Fokas method for linear convection-diffusion equation with time-dependent coefficients and its extension to other evolution equations
topic Analysis of PDEs
35A01, 35A02, 35A22, 35B65, 35C15, 35D30, 35K20
url https://arxiv.org/abs/2510.18100