Invertibility and Isomorphisms

7 important questions on Invertibility and Isomorphisms

What is an invertible transformation?

-A linear transformation T is invertible if it's inverse exists.
If T:V->W is linear, and there exists U:W->V linear then U is the inverse of T and can be denoted by T^(-1)
-TU=Iw and UT=Iv
-The inverse of every T is unique

What are some properties of invertible functions T and U?

-inverse of (TU)= inverse(U) x inverse(T)
- inverse of T^(-1) = T
-a function T is invertible iff it is bijective
-if  T:V->W is linear, and V and W are finite dimensional vector spaces with the same dimension then, T is invertible iff rank(T)=dim(V)
-if T:V->W is invertible & linear then T(-1):W->V is linear
-if T is invertible & linear from V to W then V is finite-dimensional iff W is finite dimentsional and dim(V)=dim(W)

What are some properties of an invertible square matrix?

If A is an nxn matrix, then A is invertible iff there exists a nxn matrix B such that AB=BA=I(nxn)
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What is an invertible matrix representation?

If V,W are finite-dim v.s with orderes basis beta and gamma and T:V->W is linear.
Then T is invertible iff [T] beta gamma is invertible
- the matrix representation of the inverse of T with respect to beta and gamma = the inverse of the matrix representation of T with respect to beta and gamma

When is a square matrix invertible?

An nxn matrix A is invertible iff La (left transformation of A) is invertible
-the inverse of the left transformation of A = the left transformation of the inverse of A

What is an isomorphic linear transformation?

If T and W are vector spaces over the same field F. V is isomorphic to W if there exists a linear transformation T:V->W, which is invertible.
-In that case T is called an isomorphism from V to W
- If V,  W are finite-din v.s. , then T is isomorphic from V to W iff dim(V)=dim(W)

When is a vector space F an isomorphism?

Let V be a v.s over F. Then V is isomorphic to Fn iff dim(V)=n

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