For the Nerd who has everything...

For those still struggling to find new presents for their mathematically gifted relatives and friends here is a physical model of a 3 dimensional Hilbert curve created by Henry Segerman and available from Shapeways.


The Hilbert curve is a space filling fractal mathematical object described by German mathematician David Hilbert in 1891 and related to the Peano curve (more on it here). 

Since the curve is a single loop it can be opened up and used as a hair accessory.