Nawaf Bou-Rabee

  1. Non-asymptotic mixing of the MALA algorithm.

    Authors: Martin Hairer, Nawaf Bou-Rabee, Eric Vanden-Eijnden
    Subjects: Probability
    Abstract

    The Metropolis-Adjusted Langevin Algorithm (MALA), originally introduced to
    sample exactly the invariant measure of certain stochastic differential
    equations (SDE) on infinitely long time intervals, can also be used to
    approximate pathwise the solution of these SDEs on finite time intervals.
    However, when applied to an SDE with a nonglobally Lipschitz drift coefficient,
    the algorithm may not have a spectral gap even when the SDE does. This paper
    reconciles MALA's lack of a spectral gap with its ergodicity to the invariant
    measure of the SDE and finite time accuracy.

  2. A counterexample showing the semi-explicit Lie-Newmark algorithm is not variational.

    Authors: Nawaf Bou-Rabee, Giulia Ortolan, Alessandro Saccon
    Subjects: Numerical Analysis
    Abstract

    This paper presents a counterexample to the conjecture that the semi-explicit
    Lie-Newmark algorithm is variational. As a consequence the Lie-Newmark method
    is not well-suited for long-time simulation of rigid body-type mechanical
    systems. The counterexample consists of a rigid body in a static potential
    field.

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