- Double torus
In mathematics, a

**double torus**is a topological object formed by theconnected sum of two torii. That is to say, from each of two torii the interior of a disk is removed, and the boundaries of the two disks are identified (glued together), forming a double torus.This is the simplest case of the connected sum of "n" torii. A connected sum of torii is an example of a

two dimensional manifold. According to the classification theorem for 2-manifolds, every compact connected 2-manifold is either a sphere, a connected sum of torii, or a connected sum ofprojective plane s.Double torus knot s are studied inknot theory .**Example**The

Bolza surface is the most symmetric hyperbolic surface ofgenus 2.**References*** James R. Munkres, "Topology, Second Edition", Prentice-Hall, 2000, ISBN 0-13-181629-2.

* William S. Massey, "Algebraic Topology: An Introduction", Harbrace, 1967.

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