Semisimple Lie Group
A Lie Group which has a simply connected covering group Homeomorphic to 
. The prototype is anyconnected closed subgroup of upper Triangular Complex Matrices. TheHeisenberg Group is such a group.
References
Knapp, A. W. ``Group Representations and Harmonic Analysis, Part II.'' Not. Amer. Math. Soc. 43, 537-549, 1996.
- Art Gallery Theorem
- Articulation Vertex
- Artin Braid Group
- Artinian Group
- Artinian Ring
- Artin L-Function
- Artin Reciprocity
- Artin's Conjecture
- Artin's Constant
- Artin's Reciprocity Theorem
- Artistic Series
- ASA Theorem
- Aschbacher's Component Theorem
- A-Sequence
- Associative
- Associative Algebra
- Associative Magic Square
- ASS Theorem
- Astroid
- Astroidal Ellipsoid
- Astroid Evolute
- Astroid Involute
- Astroid Pedal Curve
- Astroid Radial Curve
- Asymptosy