DeLillo decoded

If ever there was a book that needed an explanatory wiki, it’s Ratner’s Star (1976):

He was watching her bend the edges of a paper plate someone had left on the table. Again and again she folded the plate so that a different point on the circumference of the circle touched the same ketchup speck every time, a small stain located well off-center. She kept studying the resulting creases. (p. 53)

The creases form an ellipse, as Dr. Math explains.