Tbh, I mean parallel universe theory.
You said it's not bound to decay? But there are lot's of theories that suggest it will surely end someday. Like big crunch and my bet is on big freeze theory.

Imyourfed

It would've been better, had you described it a little. 

What do you call a Universe/alternate universe? 

Do you think the universe is big enough to be bound to any theories? 

For me, the universe is something that has no end, no horizen, no limit. It's endless and not bound to decay. There's no theory, there will never be  that can theorise it.