Abstract. We investigate the following family of evolutionary 1+1 PDEs that describes the balance between convection and stretching for small viscosity in the dynamics of one-dimensional nonlinear waves in fluids:mt + umx Here u = g * m denotes u(x) = ∞ −∞ g(x − y)m(y) dy. This convolution (or filtering) relates velocity u to momentum density m by integration against the kernel g(x). We shall choose g(x) to be an even function so that u and m have the same parity under spatial reflection. When ν = 0, this equation is both reversible in time and parity invariant. We shall study the effects of the balance parameter b and the kernel g(x) on the solitary wave structures and investigate their interactions analytically for ν = 0 and numerically for small or zero viscosity.This family of equations admits the classic Burgers "ramps and cliffs" solutions, which are stable for −1 < b < 1 with small viscosity. These pulson solutions obey a finite-dimensional dynamical system for the time-dependent speeds pi(t) and positions qi(t). We study the pulson and peakon interactions analytically, and we determine their fate numerically under adding viscosity.Finally, as outlook, we propose an n-dimensional vector version of this evolutionary equation with convection and stretching, namely,for a defining relation, u = G * m. These solutions show quasi-one-dimensional behavior for n, k = 2, 1 that we find numerically to be stable for b = 2. The corresponding superposed solutions of * Received by the editors July 10, 2002; accepted for publication (in revised form) by M. Golubitsky January 30, 2003; published electronically August 23, 2003. This work was performed by an employee of the U.S. Government or under U.S. Government contract. The U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes. Copyright is owned by SIAM to the extent not limited by these rights.http Pi(s, t) G x − Q i(s, t) ds, u ∈ R n .These are momentum surfaces (or filaments for k = 1), defined on surfaces (or curves) x = Q i(s, t), i = 1, 2, . . . , N. For b = 2, the Pi(s, t), Qi(s, t) ∈ R n satisfy canonical Hamiltonian equations for geodesic motion on the space of n-vector valued k-surfaces with cometric G.