- #1
spaghetti3451
- 1,344
- 33
Homework Statement
Show that the set of all ##n \times n## unitary matrices with unit determinant forms a group.
2. Homework Equations
The Attempt at a Solution
For two unitary matrices ##U_{1}## and ##U_{2}## with unit determinant, det(##U_{1}U_{2}##) = det(##U_{1}##)det(##U_{2}##) = 1.
So, closure is obeyed.
Matrix multiplication is associative.
The identity matrix is unitary with unit determinant.
For a unitary matrix ##U_{1}## with unit determinant, 1 = det(##U_{1}U_{1}^{-1}##) = det(##(U_{1}##)det(##U_{1})^{-1}##) = det(##U_{1})^{-1}##).
Therefore, the inverse exists.
Am I correct?