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## Summary:

- Is there any version of string theory or cosmological inflation that allows the most fundamental laws and constants change between universes?

## Main Question or Discussion Point

Is there any version of string theory or cosmological inflation that allows the most fundamental laws and constants change between universes?

String Theory and Cosmological Inflation are two theories or models that allow multiple universes to exist. Laws and constants of physics could change between one universe and another one. But the most fundamental laws of nature (like conservation of energy) would remain the same. In other words, while effective laws of physics would change, fundamental laws would stay the same.

For example, Andrei Linde is one of the most prominent physicists that propose that inflation theory is true. In one of his articles (Inflation, Quantum Cosmology and the Anthropic Principle) (link: https://arxiv.org/abs/hep-th/0211048) he says:

So is it there any well-known version of any of these theories (cosmological inflation or string theory) that would allow even these fundamental laws to change between universes? Or there is no specific version, and Linde was just speculating about making possible and hypothetical models of inflation where this could happen?

String Theory and Cosmological Inflation are two theories or models that allow multiple universes to exist. Laws and constants of physics could change between one universe and another one. But the most fundamental laws of nature (like conservation of energy) would remain the same. In other words, while effective laws of physics would change, fundamental laws would stay the same.

For example, Andrei Linde is one of the most prominent physicists that propose that inflation theory is true. In one of his articles (Inflation, Quantum Cosmology and the Anthropic Principle) (link: https://arxiv.org/abs/hep-th/0211048) he says:

This seem to indicate that in inflation theory we could also consider or include universes where not only low-energy laws of physics would be different, but also more fundamental ones. The problem is that the author does not clarify and does not indicate whether is it there any specific version of inflation theory that allows this.Inflationary theory allows our universe to be divided into different parts with different laws of low-energy physics that are allowed by the unique fundamental theory. Most importantly, it makes each of such domains exponentially large, which is a necessary part of justification of the anthropic principle. The diversity of possible laws of physics can be very high,especially in the models of eternal chaotic inflation where quantum fluctuations can have an extremely large amplitude, which makes the transition between all possible states particularly easy. In addition to that, one can consider different universes with different laws of physics in each of them. This does not necessarily require introduction of quantum cosmology, many-world interpretation of quantum mechanics, and baby universe theory. It is sufficient to consider an extended action represented by a sum of all possible actions of all possible theories in all possible universes. One may call this structure a ‘multiverse.’

So is it there any well-known version of any of these theories (cosmological inflation or string theory) that would allow even these fundamental laws to change between universes? Or there is no specific version, and Linde was just speculating about making possible and hypothetical models of inflation where this could happen?