- #1

- 13

- 0

I learn that an operator can be represented by basis vectors

If the basis vector is complete, the following relation holds

There exist coefficient Mij such that

Sigma Mij |i > < j|. = I , |i> is the basis! and I is the identity matrix

But isn't that in linear algebra

We call the set of basis is complete when

Any vector can be expressed into their linear combination

I wonder why here we seems have 2 definition of completeness