# Math Help - example problem

1. ## example problem

Would someone help me with this problem?

Give an example of a linear operator T on an inner product space V such that N(T) does not equal N(T*).

2. Is N(T) supposed to be the null space of T, or the dimension of the null space?

If N(T) = null space of T, then you can get an example in two dimensions. Take $T=\begin{bmatrix}0&1\\0&0\end{bmatrix}$.

If N(T) means the nullity of T then you have to go to an infinite-dimensional space. The simplest example would be the unilateral shift on $\ell_2$. This is 1-1, so has zero-dimensional null space. But its adjoint is the backwards shift, which has one-dimensional kernel.