The unsatisfactory answer:
x = tr.tensor([True]*10, dtype=tr.bool)
y = tr.tensor([True]*10, dtype=tr.bool)

x[3]    = False
y[~x]   = False # works fine
temp = x[y]
temp[3] = False
x[y] = temp # works fine

But c’mon is there any nice solution? Actually the tensors contain more than 1000 bools and i have to do these operations very often in a for loop so i do not want to copy them.