Solved by ptrblck in post #2 
              
              
                The plain Python code calculates: 
-(0.9955 ** 0.0448)
> -0.9997979654463205

While you are trying to calculate 
(-0.9955) ** 0.0448
> (0.989911956308302+0.14025081271947198j)

in PyTorch, which is a complex number. 
If you want the first output in PyTorch, just use: 
-1.0 * torch.tensor([0.9955]) *…