Definition (Invertible)
A Linear Map is called invertible or an isomorphism if there is another linear map such that and .
Definition (Inverse)
We call the inverse to .
Definition (Isomorphic)
We say that the vector spaces and are isomorphic if there is an isomorphism , and we use the notation
We denote the inverse to a linear map to be .
Remark
The notion of invertibility and isomorphism are telling us when two vector spaces are “essentially the same”. To get a better sense of why this is true we consider the following:
Remark
If is a finite dimensional vector space with , then what this theorem is telling us is that If we are trying to solve a problem about , then we can try to translate that problem to a problem about using an isomorphism , solve the problem using the techniques we’ve learned in and then transfer the solution back to V using
Ring
Bijective
Invertible
Linear Map
Inverse Matrix
Matrix of Linear Map
Upper-Triangular
Finite Dimensional
Diffeomorphism
Linear Group
Matrix Lie Group
Uniquely Decodable
Closed-loop Predictor Coefficients
WSS Predictor Coefficients
Companding Quantization
Rate Distortion Function
Capacity of Parallel Gaussian Channels
Differential Entropy
Multivariate Gaussian