# QM, Give an example of a state vector |psi> being represented in a space spanned

1. Oct 25, 2011

### jinksys

1. The problem statement, all variables and given/known data
for discrete basis vectors {{e_n}}, a state vector |psi> is represented by a column vector, with elements being psi_n = <e_n|psi>. When basis vectors correspond to those with continuous eigenvalues, vectors are represented by functions. Give such an example of a state vector |psi> being represented in a space spanned by position eigenvectors {|x>}.

2. Relevant equations

3. The attempt at a solution

C_n = <x_n | psi>

I'm really taking a shot in the dark with this one. I'm using Griffith's, so I assume my solutions lies somewhere in chapter 3.

2. Oct 26, 2011

### dextercioby

Re: QM, Give an example of a state vector |psi> being represented in a space spanned.

So...$|\psi\rangle$ is a ket which is part of the space spanned by eigenvectors of X, the latter being kets satisfying $X|x\rangle = x |x\rangle$, where the x is a real number, the spectral value of X.

Soo... $|\psi\rangle = \mbox{(something)} ~ |x\rangle$

What's (something) equal to ?

3. Oct 26, 2011

### jinksys

Re: QM, Give an example of a state vector |psi> being represented in a space spanned.

When you say spectral value, is that the same as the eigenvalue?

4. Oct 26, 2011

### dextercioby

Re: QM, Give an example of a state vector |psi> being represented in a space spanned.

A generalization of eigenvalue. But you can think of it in a simplified way as an eigenvalue.