Universe smaller than wavelengths?

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    Universe Wavelengths
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Discussion Overview

The discussion revolves around the existence of particles in the very early universe, particularly when its diameter was smaller than the wavelengths of those particles. Participants explore the implications of this scenario on current theoretical frameworks and the challenges in describing such conditions.

Discussion Character

  • Exploratory, Debate/contested, Conceptual clarification

Main Points Raised

  • Some participants question how particles could exist in an early universe smaller than their wavelengths, suggesting that wave descriptions may not be practical in this context.
  • One participant references a previous discussion about the observable universe, noting that only short wavelengths were allowed in the early universe, leading to high temperatures for particles.
  • Another participant emphasizes the lack of a comprehensive theory for the very early universe, arguing against complacency in accepting current limitations and advocating for the pursuit of a better theoretical framework.
  • A later reply mentions the absence of a quantum gravity theory, suggesting that a semi-classical approach is currently the best available method for understanding these conditions.

Areas of Agreement / Disagreement

Participants express differing views on the adequacy of current theories to describe the early universe, with some emphasizing the need for new theories while others acknowledge the limitations of existing approaches.

Contextual Notes

There are unresolved issues regarding the assumptions made about particle behavior and the definitions of relevant concepts in the context of the early universe.

kashiark
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How did particles exist in the very, very early universe when its diameter was smaller than their wavelengths? Are we just supposed to be content with the supposition that wave descriptions are impractical in this situation?
 
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I believe you are talking about the observable universe.

I discussed it here:
https://www.physicsforums.com/showthread.php?t=371333

so correct, it early Universe only short wavelengths were allowed, hence particles were very hot. I looked at it from E and t as non-commuting variables, you - from p and maximum size.
 
kashiark said:
How did particles exist in the very, very early universe when its diameter was smaller than their wavelengths? Are we just supposed to be content with the supposition that wave descriptions are impractical in this situation?

As of now we have no theory that describes the very early universe. All our current theories run into big problems there. Are we supposed to be content with it? No. That's what physics is all about: figuring it out, coming up with a theory that accurately describes these things.
 
We don't have quantum gravity theory yet,
so the semi-classical approach is the best we can do
 

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