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We establish in this paper the logarithmic Bramson correction for Fisher-KPP equations on the lattice $\mathbb{Z}$. The level sets of solutions with step-like initial conditions are located at position $c_*t-\frac{3}{2\lambda_*}\ln…

Analysis of PDEs · Mathematics 2023-03-09 Christophe Besse , Grégory Faye , Jean-Michel Roquejoffre , Mingmin Zhang

We consider a class of reaction-diffusion equations of Fisher-KPP type in which the nonlinearity (reaction term) $f$ is merely $C^1$ at $u=0$ due to a logarithmic competition term. We first derive the asymptotic behavior of (minimal speed)…

Analysis of PDEs · Mathematics 2020-09-03 Emeric Bouin , Christopher Henderson

We study the one-dimensional Fisher-KPP equation, with an initial condition $u_0(x)$ that coincides with the step function except on a compact set. A well-known result of M. Bramson states that, as $t\to+\infty$, the solution converges to a…

Analysis of PDEs · Mathematics 2018-04-19 James Nolen , Jean-Michel Roquejoffre , Lenya Ryzhik

We study the long time behavior of solutions of periodic Fisher-KPP type equations in $\mathbb{R}^n$ that arise from compactly supported initial data. We prove that propagation along a fixed direction $e\in\mathbb{S}^{n-1}$ is completely…

Analysis of PDEs · Mathematics 2019-10-21 Beniada Shabani

We consider the solution to the scalar Fisher-KPP equation with front-like initial data, focusing on the location of its level sets at large times, particularly their deviation from points moving at the known spreading speed. We consider an…

Analysis of PDEs · Mathematics 2024-10-11 Matthieu Alfaro , Thomas Giletti , Dongyuan Xiao

The famous Fisher-KPP reaction diffusion model combines linear diffusion with the typical Fisher-KPP reaction term, and appears in a number of relevant applications. It is remarkable as a mathematical model since, in the case of linear…

Analysis of PDEs · Mathematics 2016-07-06 Alessandro Audrito , Juan Luis Vazquez

We consider the non-local Fisher-KPP equation modeling a population with individuals competing with each other for resources with a strength related to their distance, and obtain the asymptotics for the position of the invasion front…

Analysis of PDEs · Mathematics 2019-11-28 Emeric Bouin , Christopher Henderson , Lenya Ryzhik

We study a variant of the Fisher-KPP equation with nonlocal dispersal. Using the theory of large deviations, we show the emergence of a "Bramson-like" logarithmic delay for the linearised equation with step-like initial data. We conclude…

Analysis of PDEs · Mathematics 2024-01-19 Nathanaël Boutillon

In this paper, we investigate the location of the spreading front and convergence to traveling wave profile of solutions to the Fisher-KPP equation in the following two cases: (i) in unbounded domains with an expanding boundary; (ii) on the…

Analysis of PDEs · Mathematics 2025-09-16 King-Yeung Lam , Chang-Hong Wu

We consider here a model of accelerating fronts, introduced in [2], consisting of one equation with nonlocal diffusion on a line, coupled via the boundary condition with a reaction-diffusion equation of the Fisher-KPP type in the upper…

Analysis of PDEs · Mathematics 2019-11-11 Anne-Charline Chalmin , Jean-Michel Roquejoffre

We consider the Fisher-KPP equation with a non-local interaction term. Hamel and Ryzhik showed that in solutions of this equation, the front location at a large time $t$ is $\sqrt 2 t +o(t)$. We study the asymptotics of the second order…

Probability · Mathematics 2017-08-29 Sarah Penington

We study a Fisher-KPP equation with spatially periodic diffusion and reaction terms. We identify a class of periodic media for which the equation admits an explicit, closed-form solution. Through a nonlinear change of variables, the problem…

Analysis of PDEs · Mathematics 2025-12-09 Lionel Roques

We study the asymptotic behaviour, as time goes to infinity, of the Fisher-KPP equation $\partial_t u=\Delta u +u-u^2$ in spatial dimension $2$, when the initial condition looks like a Heaviside function. Thus the solution is,…

Analysis of PDEs · Mathematics 2017-02-28 Jean-Michel Roquejoffre , Violaine Roussier-Michon

We study the large time asymptotics of a solution of the Fisher-KPP reaction-diffusion equation, with an initial condition that is a compact perturbation of a step function. A well-known result of Bramson states that, in the reference frame…

Analysis of PDEs · Mathematics 2016-06-20 James Nolen , Jean-Michel Roquejoffre , Lenya Ryzhik

We prove existence of and construct transition fronts for a class of reaction- diffusion equations with spatially inhomogeneous Fisher-KPP type reactions and non-local diffusion. Our approach is based on finding these solutions as…

Analysis of PDEs · Mathematics 2014-10-29 Tau Shean Lim , Andrej Zlatos

We study the propagation properties of nonnegative and bounded solutions of the class of reaction-diffusion equations with nonlinear fractional diffusion: $u_{t} + (-\Delta)^s (u^m)=f(u)$. For all $0<s<1$ and $m> m_c=(N-2s)_+/N $, we…

Analysis of PDEs · Mathematics 2013-03-28 Diana Stan , Juan Luis Vázquez

This paper presents a novel way of computing front positions in Fisher-KPP equations. Our method is based on an exact relation between the Laplace transform of the initial condition and some integral functional of the front position. Using…

Statistical Mechanics · Physics 2018-06-13 Julien Berestycki , Éric Brunet , Bernard Derrida

We investigate the asymptotic speed of spread of the solutions of a non-autonomous Fisher-KPP equation with nonlocal diffusion, driven by a thin-tailed kernel. In this paper, we are concerned with both compactly supported and exponentially…

Analysis of PDEs · Mathematics 2023-08-04 Arnaud Ducrot , Zhucheng Jin

We consider the large time behaviour of solutions to the porous medium equation with a Fisher-KPP type reaction term and nonnegative, compactly supported initial function in $L^\infty(\mathbb{R}^N)\setminus\{0\}$: \begin{equation}…

Analysis of PDEs · Mathematics 2018-06-07 Yihong Du , Fernando Quiros , Maolin Zhou

Take the linearised FKPP equation \[\partial_t h =\partial^2_x h +h\] with boundary condition $h(m(t),t)=0$. Depending on the behaviour of the initial condition $h_0(x)=h(x,0)$ we obtain the asymptotics - up to a $o(1)$ term $r(t)$ - of the…

Probability · Mathematics 2017-02-08 Julien Berestycki , Éric Brunet , Simon C. Harris , Matthew I. Roberts
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