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The charge of the universe is said to be zero. The most general argument I hear about this is that: since there was no net charge before the universe there must not be any after. Hence the universe is neutral.

But since many theorists believe in a multi-verse*, shouldn't the total charge of the multiverse be zero and individual universes might or might not have charges?

Yet people say that the universe is neutral. Since I'm not very familiar with the topic, I assume that there must be other ways to find out.

Can someone clarify why the universe is electrically neutral.

*By multiverse I am referring to the first-level Tegmark multiverse.

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    $\begingroup$ Shouldn't that be Tegmark lost Science fiction novel ;)? $\endgroup$ – Mozibur Ullah Jan 17 '19 at 19:51
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The most general argument I hear about this is that: since there was no net charge before the universe there must not be any after. Hence the universe is neutral.

No, this is not a valid argument, because modern cosmological theories do not describe the big bang as an event that happened in a pre-existing spacetime:

http://physics.stackexchange.com/questions/5150/did-spacetime-start-with-the-big-bang

Yet people say that the universe is neutral.

What people?

We do know observationally that large structures have nearly zero total charge, since otherwise we would see forces acting on galaxies and so on.

The structure of quantum mechanics is also such that there is no way for us to observe, even in principle, quantum-mechanical interference effects between states that have different charge. This is what superselection is about. Therefore the idea of different parallel universes having different charges is not testable, even in principle.

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Depends on exactly what you mean by "universe". If you mean all we can observe, then I do not think there is any good reason why the total charge should be zero. All it takes is one electron to move across the cosmological horizon to change that.

If you instead mean (as I guess you do) the "bubble" in the multiverse that we are said to live in, then the answer would be that the charge is zero because the original field (the inflaton) didn't have a charge. Instead, charges were created only with matter when the field decayed.

Now, this assumes that charge is conserved, which it may not be. If it isn't conserved, then there is again no good reason why the total should sum to zero.

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  • $\begingroup$ But if there exist other bubble universes then by conservation of charge the net charge of all of the bubbles should sum up to zero, right? $\endgroup$ – Manvendra Somvanshi Jan 17 '19 at 13:59
  • $\begingroup$ if it's not conserved, there is no reason why this should be the case either $\endgroup$ – WIMP Jan 17 '19 at 14:00

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