Jordan Basis for Differential Operator

fishshoe
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Homework Statement


Let V = P_n(\textbf{F}). Prove the differential operator D is nilpotent and find a Jordan basis.

Homework Equations


D(Ʃ a_k x^k ) = Ʃ k* a_k * x^{k-1}

The Attempt at a Solution


I already did the proof of D being nilpotent, which was easy. But we haven't covered what a "Jordan basis" is in class and it's not in either of my textbooks. I know what Jordan Canonical Form is, and Jordan blocks, but I don't know what a Jordan basis is.

Earlier I did a problem that showed that the matrix form of the differential operator on polynomials of order 2 or less. It was
<br /> \left[<br /> \begin{array}{ c c }<br /> 0 &amp; 1 &amp; 0 \\<br /> 0 &amp; 0 &amp; 2 \\<br /> 0 &amp; 0 &amp; 0<br /> \end{array} \right]<br />
Is that the kind of basis they're looking for here?
 
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No - in a Jordan basis, all entries in the superdiagonal (i.e. the line above the diagonal) have to be either 1 or zero.
 
So do I need something like

\begin{array}{ccc}
0 & 1 & 0 & \dots & 0 \\
0 & 0 & 1 & \dots & 0 \\
\dots \\
0 & 0 & 0 & \dots & 1 \\
0 & 0 & 0 & \dots & 0 \end{array}

as an n-vector Jordan basis for the polynomials of order up to n?
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

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