## Tags » Math.GR

#### Nested approximate subgroups

Suppose that are two subgroups of some ambient group , with the index of in being finite. Then is the union of left cosets of , thus for some set of cardinality . 1,036 more words

Expository

#### The standard branch of the matrix logarithm

Because of Euler’s identity , the complex exponential is not injective: for any complex and integer . As such, the complex logarithm is not well-defined as a single-valued function from to . 1,105 more words

Expository