Dear all,
I came across a question while I'm studying modern quantum
mechanics. I'm using the text book "Modern Quantum Mechanics" written
by J.J. Sakurai. While I'm working on the exercises, I got stuck in
the matrix representation of operator. Here it is:
Suppose a 2x2 matrix X (not necessarily Hermitian, nor unitary) is
written as
X = a0 + b . a
where b & a are vectors and a0, a1, a2, a3 are numbers
From my understanding, a1, a2 & a3 are the magitude of vector a in
different direction.
My real question, how can X be written as X = a0 + b.a
The RHS of the above formula are one dimension. But X should be a 2x2
matrix.
Can anyone give me some hints in understanding this problem. Thank
you.
Best Regards,
Calvin FONG
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