Online Academic Resources

Here are some (mostly) academic resources:

  • MIT OpenCourseWare has math, science and engineering classes, including online lecture videos and worked tutorial problems. (The equivalent lectures for MATH 262 can be found here.)

  • Khan Academy has lots of interesting academic videos.

  • Terry Tao's math blog.

  • XKCD comics.




    Small Dispersive Shocks

    In certain transport equations, dissipation governs the behavior at small length scales. As the dissipation goes to zero, the equations can become hyperbolic and develop shocks (for instance the inviscid Burgers equation). Here the Rankine-Hugoniot shock conditions typically describe the propagation of the shock front. In complete contrast, the small scale physics in other wave systems (for example in some optical systems) are described by dispersion. As a result, these dispersive regulated shock systems exhibit radically different behavior near the shock front.

    Using techniques based on Whitham averaging, Gurevich and Pitaevskii, (Nonstationary structure of a collisionless shock wave, Sov. Phys. JETP 38, 291 (1974)) develop a theory for a single phase (single frequency) dispersive regulated shock. Following their work, the study of zero-limit dispersive wave systems has resulted in several very nice ideas and techniques.

    A Soft Introduction to Dispersive Shocks
    These notes (originally for a course project - 18.377J) contain an introduction to dispersive shocks. Some topics included are: physical background and modeling, Whitham averaging for KdV, and some basic numerical methods for evolving solutions.

    This is really only the start. Some other interesting papers are:

  • P. D. Lax, C. D. Levermore
    The small dispersion limit of the Korteweg-de Vries equation. I. II. III.
    Comm. Pure Appl. Math. 36 (1983), No. 3, 253-290; No. 5, 571-593; No. 6, 809-829.
  • H. Flaschka, M. G. Forest, D. W. McLaughlin
    Multiphase averaging and the inverse spectral solution of the Korteweg-deVries equation
    Comm. Pure Appl. Math. 33, (1980), pp. 739-784.
  • D. McLaughlin, J. Strain
    Computing the weak limit of KdV
    Comm. Pur Appl. Math. 47, (1994), 1319-1364.
  • P. Deift, X. Zhou,
    A Steepest Descent Method for Oscillatory Riemann-Hilbert Problems; Asymptotics for the MKdV Equation, Ann. of Math. 137, (1993), 295-368.