How unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem
We analyze cosmology assuming unitary quantum mechanics, using a tripartite partition into system, observer, and environment degrees of freedom. This generalizes the second law of thermodynamics to ‘‘The system’s entropy cannot decrease unless it interacts with the observer, and it cannot increase...
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| অন্যান্য লেখক: | |
| বিন্যাস: | প্রবন্ধ |
| ভাষা: | en_US |
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American Physical Society
2012
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| অনলাইন ব্যবহার করুন: | http://hdl.handle.net/1721.1/72144 https://orcid.org/0000-0001-7670-7190 |
| _version_ | 1826202959688499200 |
|---|---|
| author | Tegmark, Max Erik |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Tegmark, Max Erik |
| author_sort | Tegmark, Max Erik |
| collection | MIT |
| description | We analyze cosmology assuming unitary quantum mechanics, using a tripartite partition into system,
observer, and environment degrees of freedom. This generalizes the second law of thermodynamics to
‘‘The system’s entropy cannot decrease unless it interacts with the observer, and it cannot increase unless
it interacts with the environment.’’ The former follows from the quantum Bayes theorem we derive. We
show that because of the long-range entanglement created by cosmological inflation, the cosmic entropy
decreases exponentially rather than linearly with the number of bits of information observed, so that a
given observer can reduce entropy by much more than the amount of information her brain can store.
Indeed, we argue that as long as inflation has occurred in a non-negligible fraction of the volume, almost
all sentient observers will find themselves in a post-inflationary low-entropy Hubble volume, and we
humans have no reason to be surprised that we do so as well, which solves the so-called inflationary
entropy problem. An arguably worse problem for unitary cosmology involves gamma-ray-burst constraints
on the ‘‘big snap,’’ a fourth cosmic doomsday scenario alongside the ‘‘big crunch,’’ ‘‘big chill,’’
and ‘‘big rip,’’ where an increasingly granular nature of expanding space modifies our life-supporting laws
of physics. Our tripartite framework also clarifies when the popular quantum gravity approximation
G
8 GhT
i is valid, and how problems with recent attempts to explain dark energy as gravitational
backreaction from superhorizon scale fluctuations can be understood as a failure of this approximation. |
| first_indexed | 2024-09-23T12:28:03Z |
| format | Article |
| id | mit-1721.1/72144 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T12:28:03Z |
| publishDate | 2012 |
| publisher | American Physical Society |
| record_format | dspace |
| spelling | mit-1721.1/721442022-09-28T08:04:13Z How unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem Tegmark, Max Erik Massachusetts Institute of Technology. Department of Physics MIT Kavli Institute for Astrophysics and Space Research Tegmark, Max Erik Tegmark, Max Erik We analyze cosmology assuming unitary quantum mechanics, using a tripartite partition into system, observer, and environment degrees of freedom. This generalizes the second law of thermodynamics to ‘‘The system’s entropy cannot decrease unless it interacts with the observer, and it cannot increase unless it interacts with the environment.’’ The former follows from the quantum Bayes theorem we derive. We show that because of the long-range entanglement created by cosmological inflation, the cosmic entropy decreases exponentially rather than linearly with the number of bits of information observed, so that a given observer can reduce entropy by much more than the amount of information her brain can store. Indeed, we argue that as long as inflation has occurred in a non-negligible fraction of the volume, almost all sentient observers will find themselves in a post-inflationary low-entropy Hubble volume, and we humans have no reason to be surprised that we do so as well, which solves the so-called inflationary entropy problem. An arguably worse problem for unitary cosmology involves gamma-ray-burst constraints on the ‘‘big snap,’’ a fourth cosmic doomsday scenario alongside the ‘‘big crunch,’’ ‘‘big chill,’’ and ‘‘big rip,’’ where an increasingly granular nature of expanding space modifies our life-supporting laws of physics. Our tripartite framework also clarifies when the popular quantum gravity approximation G 8 GhT i is valid, and how problems with recent attempts to explain dark energy as gravitational backreaction from superhorizon scale fluctuations can be understood as a failure of this approximation. National Science Foundation (U.S.) (grant nos. AST-0708534, AST-090884 and AST-1105835) 2012-08-15T15:57:20Z 2012-08-15T15:57:20Z 2012-06 2011-08 Article http://purl.org/eprint/type/JournalArticle 1550-7998 1089-4918 http://hdl.handle.net/1721.1/72144 Tegmark, Max. “How Unitary Cosmology Generalizes Thermodynamics and Solves the Inflationary Entropy Problem.” Physical Review D 85.12 (2012): 123517. © 2012 American Physical Society. https://orcid.org/0000-0001-7670-7190 en_US http://dx.doi.org/10.1103/PhysRevD.85.123517 Physical Review D Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Physical Society APS |
| spellingShingle | Tegmark, Max Erik How unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem |
| title | How unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem |
| title_full | How unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem |
| title_fullStr | How unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem |
| title_full_unstemmed | How unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem |
| title_short | How unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem |
| title_sort | how unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem |
| url | http://hdl.handle.net/1721.1/72144 https://orcid.org/0000-0001-7670-7190 |
| work_keys_str_mv | AT tegmarkmaxerik howunitarycosmologygeneralizesthermodynamicsandsolvestheinflationaryentropyproblem |