Measure problem (cosmology)

Not to be confused with Measurement problem.

The measure problem in cosmology concerns how to compute the ratios of universes of different types within a multiverse. It typically arises in the context of eternal inflation. The problem arises because different approaches to calculating these ratios yield different results, and it is not clear which approach (if any) is correct.[1]

Measures can be evaluated by whether they predict observed physical constants, as well as whether they avoid counterintuitive implications, such as the youngness paradox or Boltzmann brains.[2] While dozens of measures have been proposed,[3]: 2  few physicists consider the problem to be solved.[4]

  1. ^ Cite error: The named reference Carroll2011 was invoked but never defined (see the help page).
  2. ^ Andrei Linde; Vitaly Vanchurin; Sergei Winitzki (15 Jan 2009). "Stationary Measure in the Multiverse". Journal of Cosmology and Astroparticle Physics. 2009 (1): 031. arXiv:0812.0005. Bibcode:2009JCAP...01..031L. doi:10.1088/1475-7516/2009/01/031. S2CID 119269055.
  3. ^ Linde, Andrei; Noorbala, Mahdiyar (9 September 2010). "Measure problem for eternal and non-eternal inflation". Journal of Cosmology and Astroparticle Physics. 2010 (9): 8. arXiv:1006.2170. Bibcode:2010JCAP...09..008L. doi:10.1088/1475-7516/2010/09/008. S2CID 119226491.
  4. ^ Wolchover, Natalie; Byrne, Peter (3 November 2014). "In a Multiverse, What Are the Odds?". Retrieved 8 January 2015.