We study a system consisting of n particles, moving forward in jumps on the real line. Each particle can make both independent jumps, whose sizes have some distribution, and ‘synchronization’ jumps, which allow it to join a randomly chosen other particle if the latter happens to be ahead of it. The system state is the empirical distribution of particle locations. We consider the mean-field asymptotic regime where $n\to\infty$. We prove that $v_n$, the steady-state speed of advance of the particle system, converges, as $n\to\infty$, to a limit $v_{**}$ which can easily be found from a minimum speed selection principle. Also we prove that as $n\to\infty$, the system dynamics converges to that of a deterministic mean-field limit (MFL). We show that the average speed of advance of any MFL is lower-bounded by $v_{**}$, and the speed of a ‘benchmark’ MFL, resulting from all particles initially being co-located, is equal to $v_{**}$. In the special case of exponentially distributed independent jump sizes, we prove that a traveling-wave MFL with speed v exists if and only if $v\ge v_{**}$, with $v_{**}$ having a simple explicit form; we also show the existence of traveling waves for the modified systems with a left or right boundary moving at a constant speed v. We provide bounds on an MFL’s average speed of advance, depending on the right tail exponent of its initial state. We conjecture that these results for exponential jump sizes extend to general jump sizes.

This article studies propagating traveling waves in a class of reaction-diffusion systems which model isothermal autocatalytic chemical reactions as well as microbial growth and competition in a flow reactor. In the context of isothermal autocatalytic systems, two different cases will be studied. The first is autocatalytic chemical reaction of order m without decay. The second is chemical reaction of order m with a decay of order n, where m and n are positive integers and m>n≥1. A typical system in autocatalysis is A+2B→3B and B→C involving two chemical species, a reactant A and an auto-catalyst B and C an inert chemical species.

The numerical computation gives more accurate estimates on minimum speed of traveling waves for autocatalytic reaction without decay, providing useful insight in the study of stability of traveling waves.

For autocatalytic reaction of order m = 2 with linear decay n = 1, which has a particular important role in chemical waves, it is shown numerically that there exist multiple traveling waves with 1, 2 and 3 peaks with certain choices of parameters.

We review recent results on stability of traveling waves in partly parabolicreaction-diffusion systems with stable or marginally stable equilibria. We explain howattention to what are apparently mathematical technicalities has led to theorems thatallow one to convert spectral calculations, which are used in the sciences and engineeringto study stability of a wave, into detailed, theoretically-based information about thebehavior of perturbations of the wave.

Traveling waves for the nonlocal Fisher Equation can exhibit much more complex behaviourthan for the usual Fisher equation. A striking numerical observation is that a travelingwave with minimal speed can connect a dynamically unstable steady state 0 to a Turingunstable steady state 1, see [12]. This is provedin [1, 6] inthe case where the speed is far from minimal, where we expect the wave to be monotone.

Here we introduce a simplified nonlocal Fisher equation for which we can build simpleanalytical traveling wave solutions that exhibit various behaviours. These travelingwaves, with minimal speed or not, can (i) connect monotonically 0 and 1, (ii) connectthese two states non-monotonically, and (iii) connect 0 to a wavetrain around 1. Thelatter exist in a regime where time dynamics converges to another object observed in[3, 8]: awave that connects 0 to a pulsating wave around 1.

Mechanisms contributing to the spread of avian influenza seem to be well identified, buthow their interplay led to the current worldwide spread pattern of H5N1 influenza is still unknowndue to the lack of effective global surveillance and relevant data. Here we develop some deterministicmodels based on the transmission cycle and modes of H5N1 and focusing on the interactionamong poultry, wild birds and environment. Some of the model parameters are obtained fromexisting literatures, and others are allowed to vary in order to assess the effectiveness of variouscontrol strategies involving bird migration, agro-ecological environments, live and dead poultrytrading, smuggling of wild birds, mechanical movement of infected materials and specific farmingpractices. Our simulations are carried out for a set of parameters that leads to the basic reproductionnumber 3.3. We show that by reducing 95% of the initial susceptible poultry population or bykilling all infected poultry birds within one day, one may control the disease outbreak in a localsetting. Our simulation shows that cleaning the environment is also a feasible and useful controlmeasure, but culling wild birds and destroying their habitat are ineffective control measures. Weuse a one dimensional PDE model to examine the contribution to the spatial spread rate by thesize of the susceptible poultry birds, the diffusion rates of the wild birds and the virus. We noticethe diffusion rate of the wild birds with high mortality has very little impact on the spread speed.But for the wild birds who can survive the infection, depending on the direction of convection,their diffusion rate can substantially increase the spread rate, indicating a significant role of themigration of these type of wild birds in the spread of the disease.