Cosmic Inflation, the Arrow of Time & Boltzmann Brains

The thermodynamic arrow of time offers a very interesting perspective on cosmic inflation and the tuning problems it is meant to address. My research has explored the connection between these two topics from a variety of angles, and I believe further development of these connections will help us attain a deeper understanding of the cosmos and the role of cosmic inflation.

Some technical publications

  1. Cosmic Inflation and the Arrow of Time, in "Science and Ultimate Reality: Quantum Theory, Cosmology and Complexity", honoring John Wheeler's 90th birthday. J. D. Barrow, P.C.W. Davies, & C.L. Harper eds. Cambridge University Press (2004) astro-ph/0210527 (This paper is meant to be accessible to a wide range of trained scientists, not just experts in the field. It includes my first written discussion of the connection between inflation and the "Boltzmann Brain" problem.)
  2. Can the universe afford inflation? hep-th/0405270 Phys. Rev. D70 (2004) 063528 (de Sitter equilibrium picture using "Farhi-Guth-Gnuven" tunneling, also first use of the term "Boltzmann Brain" in a paper... the first appearance in seminar slides is on slide 36 here)
  3. Big picture notes on the arrow of time, tuning and cosmology for the 2019 "Out of Equilibrium World" workshop
  4. de Sitter equilibrium as a fundamental framework for cosmology (in the proceedings of the DICE2008 conference, Thomas Elze, ed). arXiv:0906.1047
  5. Eternal Inflation with Arrival Terminals arXiv:1406.7352 Phys.Rev. D91 (2015) 023503
  6. Tuning, Ergodicity, Equilibrium and Cosmology arXiv:1401.7309 Phys.Rev. D91 (2015) 10, 10351
  7. Cosmic curvature from de Sitter equilibrium cosmology arXiv:1104.3315, PhysRevLett.107.151102
  8. Holographic bounds and finite inflation arXiv:1410.6065, Phys. Rev. D 91, 043513 (2015)
  9. Ludwig Boltzmann, On Certain Questions of the Theory of Gases (Nature, Feb 28, 1895, p413) This is the paper where Boltzmann first mentioned the "Boltzmann Brain Problem" (but he does not call it that). Here (at slide 36) is the first record I know of using the term "Boltzmann Brain", which we also use in reference 2 above.


  1. The arrow of time in cosmology, cosmic inflation and the emergence of classicality Simons Program: Quantum Information in Cosmology, April 2018, Copenhagen (Video) Note: In "reel" 2, at the 8 min mark I start a discussion of the "free tuning" inflation exploits by selecting the Bunch-Davies vacuum.
  2. "Statement of Interest" prepared for the 2019-20 Simons Program.
  3. Cosmic Inflation Tutorial (for scientists not necessarily familiar with cosmology) Simons Program: Quantum Information in Cosmology, April 2018, Copenhagen (slides and video)
  4. A. Albrecht Les Houches Lectures on Inflation (slides here) in Post-Planck Cosmology: Lecture notes of the Les Houches Summer School: Volume 100, July 2013 (Oxford, 2015) DOI: 10.1093/acprof:oso/9780198728856.001.0001
  5. Cosmic Inflation: Open questions and perspectives on future surveys Cosmological Quests for the Next Decade, Daejeon April 2017
  6. Cosmic Inflation, Reflections on Motivations, Accomplishments and FutureOpportunities
  7. , Advances in Theoretical Cosmology in Light of Data, NORDITA July, 2017, Stockholm

More accessible information


  • My review of Sean Carroll's book on the arrow of time in Physics Today