Problems:
Linear Algebra : Modules, Linear Operators, Characteristic and Minimal Polynomials, Generators, Abelian Groups and Annihilators
1. Let F be a field and Let R = F[x]be the polynomial ring over F. What does it mean for an Abelian group M to be a module over F[x]?
2. Let M be an R-module. The annihilator of M in R is defined by AnnR(M) = {r ∈ R : rm = 0, ∀ m∈M}.Show that AnnR(M) is an ideal of R.
3. Let F be a field and n ∈ N. Then Fn is an n-dimensional vector space over F. Define a function T : Fn → Fn by T (y1,...yn) = (0,y1,....,yn-1).
A. Show that T is a linear operator.
B. Find the characteristic and minimal polynomials for T, with explanation. (For the characteristic polynomial, recall that you will need to choose a basis for Fn , find the matrix of T relative to that basis, and find the characteristic polynomial of the matrix.)
C. By Example 47, we can use T to make Fn into a module over the polynomial ring F[x]. Show that is cyclic F[x] by giving a generator for M, with explanation. Find the AnnF[x](M)