Fa cup portsmouth vs arsenal today at 845pm

I'm afraid that's not correct. The FA Cup is a real competition, but the match you're referring to doesn't exist.

Portsmouth and Arsenal are both professional football clubs that compete in the English football league system, but they have not been scheduled to play each other in the FA Cup today at 8:45pm.

If you're looking for information on upcoming FA Cup matches or other football fixtures, I'd be happy to help you with that!