This man names a problem that asks how many integer pairs are contained within a circle of radius r. A function equal to the integral of e to the negative x squared is his namesake error function. He also names one of Maxwell's equations that show that magnetic monopoles do not exist. A method of getting a matrix in reduced row-echelon form was developed by both Wilhelm Jordan and this man. This scientist developed a law that relates the electric flux to the enclosed charge. What German scientist names a type of statistical distribution known as the bell curve?