So I know there are several types of acquisition function for Bayesian optimization technique. But according to Wikipedia
There are several methods used to define the prior/posterior distribution over the objective function. The most common two methods use Gaussian processes in a method called Kriging. Another less expensive method uses the Parzen-Tree estimator to construct two distributions for 'high' and 'low' points, and then finds the location that maximizes the expected improvement.
So is the expected improvement a Gaussian process, or is it something different?