TY - JOUR

T1 - How many universes are in the multiverse?

AU - Linde, Andrei

AU - Vanchurin, Vitaly

PY - 2010/4/20

Y1 - 2010/4/20

N2 - We argue that the total number of distinguishable locally Friedmann "universes" generated by eternal inflation is proportional to the exponent of the entropy of inflationary perturbations and is limited by ee3N, where N is the number of e-folds of slow-roll posteternal inflation. For simplest models of chaotic inflation, N is approximately equal to de Sitter entropy at the end of eternal inflation; it can be exponentially large. However, not all of these universes can be observed by a local observer. In the presence of a cosmological constant Λ the number of distinguishable universes is bounded by e|Λ|-3/4. In the context of the string theory landscape, the overall number of different universes is expected to be exponentially greater than the total number of vacua in the landscape. We discuss the possibility that the strongest constraint on the number of distinguishable universes may be related not to the properties of the multiverse but to the properties of observers.

AB - We argue that the total number of distinguishable locally Friedmann "universes" generated by eternal inflation is proportional to the exponent of the entropy of inflationary perturbations and is limited by ee3N, where N is the number of e-folds of slow-roll posteternal inflation. For simplest models of chaotic inflation, N is approximately equal to de Sitter entropy at the end of eternal inflation; it can be exponentially large. However, not all of these universes can be observed by a local observer. In the presence of a cosmological constant Λ the number of distinguishable universes is bounded by e|Λ|-3/4. In the context of the string theory landscape, the overall number of different universes is expected to be exponentially greater than the total number of vacua in the landscape. We discuss the possibility that the strongest constraint on the number of distinguishable universes may be related not to the properties of the multiverse but to the properties of observers.

UR - http://www.scopus.com/inward/record.url?scp=77952418594&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77952418594&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.81.083525

DO - 10.1103/PhysRevD.81.083525

M3 - Article

AN - SCOPUS:77952418594

VL - 81

JO - Physical Review D - Particles, Fields, Gravitation and Cosmology

JF - Physical Review D - Particles, Fields, Gravitation and Cosmology

SN - 1550-7998

IS - 8

M1 - 083525

ER -