arXiv subjects

Tim Heilmann

Publications and source records attributed to Tim Heilmann.

5 recordsLinked to original sources

arXiv2026

$\Gamma$-convergence for nonlocal phase transitions involving the $H^{1/2}$ norm and surfactants

We study functionals \begin{equation*} F_\varepsilon (u,\rho) := \frac{1}{\varepsilon} \int_\Omega W(u) \, dx + \frac{1}{|\ln(\varepsilon)|} \int_\Omega \int_\Omega \frac{(u(y) - u(x))^2}{|y - x|^{N+1}} \, dy \,dx + \frac{1}{|\ln(\varepsilon)|} \int_\Omega \left| \int_\Omega \frac{(u(y) - u(x))^2}{|y - x|^{N+1}} \, dy - \rho(x) \right| \,dx \end{equation*} for a double-well potential $W$ and a nonlocal, critically scaled gradient-like term, together with a surfactant term. We show compactness in the space of $BV$ functions on $\Omega$ and the $\Gamma$-convergence to an energy given as local perimeter-type functional, depending also on the limit density of surfactant on the interface, plus the total variation of the surfactant measure away from the interface.

math.AP↗

arXiv2025

$\Gamma$-convergence for nonlocal phase transitions involving the $H^{1/2}$ norm

We study functionals \begin{equation*} F_\varepsilon (u) := \lambda_\varepsilon \int_\Omega W(u) \, dx + \varepsilon \|u\|_{H^{1/2}}^2 \end{equation*} for a double well potential $W$ and the Gagliardo seminorm $\|\cdot\|_{H^{1/2}}$ when $\varepsilon \ln(\lambda_\varepsilon) \rightarrow k$ as $\varepsilon \rightarrow 0^+$ and show compactness in the space of $BV$ functions on $\Omega$ and the $\Gamma$-convergence to the classical surface tension functional.

math.AP↗

arXiv2024

Surfactants in a Non-local Model for Phase Transitions

We investigate the influence of surfactants on stabilizing the formation of interfaces in non-local anisotropic two-phase fluid at equilibrium. The analysis focuses on singularly perturbed non-local van der Waals-Cahn-Hillard-type energies, supplemented with a term that accounts for the interaction between the surfactant and the fluid. We derive by Gamma-convergence the effective surface tension model as the thickness of the transition layer vanishes and show that it decreases when the surfactant segregates to the interface.

math.AP↗

arXiv2024

A notion of $s$-fractional mass for $1$-currents in higher codimension

In this paper we propose a notion of $s$-fractional mass for $1$-currents in $\R^d$. Such a notion generalizes the notion of $s$-fractional perimeters for sets in the plane to higher codimension one-dimensional singularities. Remarkably, the limit as $s\to 1$ of the $s$-fractional mass gives back the classical notion of length for regular enough curves in $\R^d$. We prove a lower semi-continuity and compactness result for sequences of $1$-currents with uniformly bounded fractional mass and support. Moreover, we prove the density of weighted polygonal, closed and compact oriented curves in the class of divergence-free 1-currents with compact support and finite fractional mass. Finally, we discuss some possible applications of our notion of fractional mass to build up purely geometrical approaches to the variational modeling of dislocation lines in crystals and to vortex filaments in superconductivity.

math.FA↗

arXiv2024

Surfactants in the Two Gradient Theory of Phase Transitions

We investigate the influence of surfactants on stabilizing the formation of interfaces in solid-solid phase transitions. The analysis focuses on singularly perturbed van der Waals-Cahn-Hillard-type energies for gradient vector fields, supplemented with a term that accounts for the interaction between the surfactant and the solid. Assuming the potential term to have only two rank-one connected wells, we prove that the effective energy for the formation of an interface decreases when the surfactant segregate to the interface.

math.AP↗