Name: UIN: Problem Set 8 Math 423, Section 200, Spring 2015 Due: Monday, April 6. Review Sections 7B and 7C in your textbook. Complete the following items, staple this page to the front of your work, and turn your assignment in at the beginning of class on Monday, April 6. One of the problems is considered extra credit. Remember to fully justify all your answers, and provide complete details. Neatness is greatly appreciated. Recall that if T is an operator on V and λ is an eigenvalue of T , E(λ, T ) = ker(T − λ idV ) is the λ-eigenspace of T . 1. Let V be a finite dimensional inner product space over C. Show that T ∈ L (V) is normal if and only if all pairs of eigenvectors corresponding to different eigenvalues are orthogonal and V = E(λ1 , T ) ⊕ · · · ⊕ E(λm , T ), where λ1 , . . . , λm are the distinct eigenvalues of T . 2. Let V be a finite dimensional inner product space over R. Show that T ∈ L (V) is self-adjoint if and only if all pairs of eigenvectors corresponding to different eigenvalues are orthogonal and V = E(λ1 , T ) ⊕ · · · ⊕ E(λm , T ), where λ1 , . . . , λm are the distinct eigenvalues of T . 3. Give an example of a diagonalizable operator T ∈ L (R3 ) that is not self-adjoint with respect to the Euclidean inner product. 4. Find a ∈ R so that the matrix 1 1 0 0 1 1 1 0 a represents a normal operator T ∈ L (R3 ) with respect to the standard basis of R3 , where R3 is considered with the usual Euclidean inner product. Page 1 5. a. Give an example of a diagonalizable operator T ∈ L (C2 ) (considered with the Euclidean inner product) whose matrix with respect to the standard basis is symmetric, but which cannot be diagonalized with respect to an orthonormal basis. b. Give an example of a non-diagonalizable operator T ∈ L (C2 ) (considered with the Euclidean inner product) whose matrix with respect to the standard basis is symmetric. 6. Let V be a finite dimensional inner product space, and let T ∈ L (V) be self-adjoint. Suppose 2 and 3 are the only eigenvalues of T . Show that T 2 − 5T + 6 idV = 0. 7. Let V be a finite dimensional inner product space over C. Prove that a normal operator T ∈ L (V) is self-adjoint if and only if all of its eigenvalues are real. 8. Let V be a finite dimensional inner product space over C. Suppose that T ∈ L (V) is a normal operator such that T 9 = T 8 . Prove that T is self-adjoint and T 2 = T . 9. Let V be a finite dimensional inner product space, T ∈ L (V) self-adjoint, λ ∈ F and ε > 0. Suppose there exists v such that kvk = 1 and kT v − λvk < ε. Prove that T has an eigenvalue λ0 such that |λ0 − λ| < ε. 10. Let U be a finite dimensional R-vector space, and T ∈ L (U). Prove that T is diagonalizable if and only if there is an inner product on U that makes T into a self-adjoint operator. 11. Let V be a finite dimensional inner product space over C. Prove that every normal operator on V has a square root. 1/10 2/10 3/10 4/10 5/10 6/10 7/10 8/10 9/10 10/10 11/10 Through the course of this assignment, I have followed the Aggie Code of Honor. An Aggie does not lie, cheat or steal or tolerate those who do. Signed: Page 2 Total/100