" a positive definite quadratic form" Mobius, Namely, the lower parabola is in the xz plane, the upper one in the yz plane. The origin is a “saddle” point.

The Sensual (Quadratic) Form

www.maths.ed.ac.uk/~aar/.../conwaysens.pdf

University of Edinburgh

where J.L(d) is the Mobius function. However, in the first lecture, we ...... If a positive defInite quadratic form (in any num- ber of variables) with integral matrix

http://uregina.ca/~mareal/cs5.pdf

Namely, the lower parabola is in the xz plane, the upper one in the yz plane. The origin is a “saddle” point. 

To each P in S the Gauss map assigns a point N(P) on the unit sphere S 2 .