2H Vs. dual wield 1H

have been searching for a while and their seems to be a lot of conjecture so i was wondering if a developer could weigh in. Is there a damage multiplier that affects 1H in dual wield and is there a damage multiplier for 2H if so what are they? don't respond with conjecture I'm looking for verifiable information with an official source well unless someone wants to do the math for me and upload screenshots to verify :)

thanks in advance

F1tch

2H Vs. dual wield 1H