Leonard A. Rastrigin
I found the academic website of Leonard A. Rastrigin, see here.
He is the author of the famous Rastrigin Function, see it here. That function is hard to optimize, since it has so many local optima and the global optimum exhibits an inclination/slope. It also is a traditional benchmark in Evolutionary Computation to measure the optimization features of an Evolutionary Algorithm.
The general form of that function is the following:
The 3D shape of it:
As you can see, bigger the value of the steepness, more complex the fitness landscape becomes.
It's a beautiful function!
You can check Rastrigin's publication here.