I have a $8\times 8$ matrix, whose 2,3,5,8-th row and columns are zero:
mat = {{1/2, 0, 0, 0, 0, 1/2 E^(-I t w1), -(1/2) E^(-2 I t w1 - I t w2),
0}, {0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0,
0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0,
0}, {-(1/2) E^(I theta1 - I t w2), 0, 0, 0, 0,
1/2 E^(I theta1 - I t w1 - I t w2),
1/2 E^(I theta1 - 2 I t w1 - 2 I t w2),
0}, {1/2 E^(I theta1 + I theta2 - I t w2), 0, 0, 0,
0, -(1/2) E^(I theta1 + I theta2 - I t w1 - I t w2),
1/2 E^(I theta1 + I theta2 - 2 I t w1 - 2 I t w2), 0}, {0, 0, 0, 0,
0, 0, 0, 0}}
The above matrix looks like this:
What I want to do is, by removing the row/column with zero entries, I want to condense this into $4\times 4$ matrix. How can I do this?