def laplacian(y, factor=1.0, exp=False):
    """Return the laplacian of `y` times `factor` or the exponential of this.

        Parameters
        ----------
        factor : float
           Additional factor (mostly used with `exp=True`).  The
           implementation must be careful to allow the factor to
           broadcast across the components.
        exp : bool
           If `True`, then compute the exponential of the laplacian.
           This is used for split evolvers.
        """
