Are there any defining characteristics of our universe that could be different for other universes (or "instances of our universe") that operate under the same laws of physics?

And which, if any, are known or suspected to determine physical constants?

For example:

  1. If I'm reading this correctly, then there is no concept of "energy" that is constant across time for our universe. But could we say something like, "Our universe had energy of X at time T after the singularity?" Would this be a unique characteristic of our universe, in the sense that, "It could have instead had energy of Y at time T?"

  2. Our universe may have a rotational moment, which again may not be constant with time, but which would be a distinct characteristic.

Or, perhaps one could ask this the other way: Which physical constants of our universe are independent of physical laws? E.g., could we say, "Our instance of the universe is one in which h is 6.626... but not only could it instead be 6.726... but also we would not expect to observe a qualitatively different universe if that were the case?"

I.e., could we say that our universe is one of many possible and similar universes along some parameter spaces, including parameters (α, β, γ...)?

(Or can no statements like this be made? The converse would be something like, "We only know that the laws we have identified hold in this universe and with these parameters. We can't deduce the cosmological consequences of even a small change to any of these physical constants from their observable value here, and/or there is no reason to believe that our physical laws would hold if any characteristic of our universe were different.")

  • $\begingroup$ "Are there any defining characteristics of our universe that could be different for other universes (or "instances of our universe") that operate under the same laws of physics?". By definition, any other possible universe would NEED different parameters for at least one physical constant, otherwise how could we distinguish "us" from "them"? $\endgroup$ – user108787 May 1 '16 at 16:47
  • $\begingroup$ @count_to_10: That's part of the question. If we can say, "Our universe has energy X or rotational-velocity Y at time t," but those parameters don't affect physical constants, then if we "meet" someone who says, "My universe has energy X' at time t," then they "come from" a different universe. $\endgroup$ – feetwet May 1 '16 at 17:01
  • $\begingroup$ I would argue that, if 2 universes have the same initial parameters, then they would end up in the same rotational, (or not) state. But hopefully you get a full answer from someone better qualified than I in cosmology. $\endgroup$ – user108787 May 1 '16 at 17:14
  • $\begingroup$ This might interest you regarding rotation, possibly the distribution of galaxies would be different: news.discovery.com/space/… $\endgroup$ – user108787 May 1 '16 at 17:19
  • $\begingroup$ @count_to_10 - Yes, this is essentially an "initial parameter" question. I phrased it the way I did because the "initial" part can be tricky because it's a singularity and my understanding is we don't have good ways of talking about the "initial" condition of the universe. So instead I'm asking about conditions at some t sufficiently large that we can talk about it in the context of our current understanding. $\endgroup$ – feetwet May 1 '16 at 17:25

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