A Perspective on the Landscape Problem


I discuss the historical roots of the landscape problem and propose criteria for its successful resolution. This provides a perspective to evaluate the possibility to solve it in several of the speculative cosmological scenarios under study including eternal inflation, cosmological natural selection and cyclic cosmologies.

Invited contribution for a special issue of Foundations of Physics titled Forty Years Of String Theory: Reflecting On the Foundations.

This is a preview of subscription content, access via your institution.


  1. 1.

    For several reasons this cannot be the AdS/CFT correspondence. One reason is that the cosmological constant has the wrong sign, another is that a cosmological theory cannot have boundaries or asymptotic regions, for reasons I will discuss below.

  2. 2.

    This partly reflects conclusions reached in joint work with Roberto Mangabeira Unger [80].

  3. 3.

    Which he named.

  4. 4.

    The evidence that quantum gravity effects eliminate singularities in this way has become much stronger recently. Compare older papers on bounces which employ mainly semiclassical methods [3436] to the newer literature on loop quantum cosmology which shows that bounces are generic in exact quantum evolutions of a class of quantum cosmological models [3741]. A study of modifications of coupling constants during bounces is in [42].

  5. 5.

    Claims by Penrose and Gurzadyan [1416] that these have been observed are presently controversial [1719].

  6. 6.

    Critiques of cosmological natural selection were published in [4851]. These have been all answered in the recent papers [27, 28] and book [1] (see especially the appendix and end notes).

  7. 7.

    Indeed, the use of the word landscape was meant to suggest the analogy to the fitness landscapes of evolutionary biology [1].

  8. 8.

    This prediction was pointed to in [1], which was published in 1997, just before the discovery of dark energy. “This means that we may expect that when all the observations have been sorted out, there will be a small cosmological constant, there will be a neutrino mass and Omega will not be exactly equal to one.” [1], p. 315.

  9. 9.

    An excellent historical and critical survey of the anthropic principle and related developments is in [73].

  10. 10.

    I am grateful to Ben Freivogel for conversations on this issue.


  1. 1.

    Smolin, L.: The Life of the Cosmos (1997). From Oxford University Press (in the USA), Weidenfeld and Nicolson (in the United Kingdom) and Einaudi Editorici (in Italy)

  2. 2.

    Strominger, A.: Superstrings with torsion. Nucl. Phys. B 274, 253 (1986)

    MathSciNet  ADS  Article  Google Scholar 

  3. 3.

    Kachru, S., Kallosh, R., Linde, A., Trivedi, S.P.: de Sitter vacua in string theory. Phys. Rev. D 68, 046005 (2003). arXiv:hep-th/0301240

    MathSciNet  ADS  Article  Google Scholar 

  4. 4.

    Susskind, L.: The anthropic landscape of string theory. arXiv:hep-th/0302219

  5. 5.

    Susskind, L.: The Cosmic Landscape: String Theory and the Illusion of Intelligent Design. Little Brown, New York (2006)

    Google Scholar 

  6. 6.

    Vilenkin, A.: Birth of inflationary universes. Phys. Rev. D 27, 2848 (1983)

    MathSciNet  ADS  Article  Google Scholar 

  7. 7.

    Linde, A.: The inflationary universe. Rep. Prog. Phys. 47, 925 (1984)

    MathSciNet  ADS  Article  Google Scholar 

  8. 8.

    Linde, A., Linde, D., Mezhlumian, A.: From the big bang theory to the theory of a stationary universe. Phys. Rev. D 49, 1783 (1994). arXiv:gr-qc/9306035

    ADS  Article  Google Scholar 

  9. 9.

    Garcia-Bellido, J., Linde, A.: Stationarity of inflation and predictions of quantum cosmology. Phys. Rev. D 51, 429 (1995). arXiv:hep-th/9408023

    MathSciNet  ADS  Article  Google Scholar 

  10. 10.

    Garriga, J., Vilenkin, A.: A prescription for probabilities in eternal inflation. Phys. Rev. D 64, 023507 (2001). arXiv:gr-qc/0102090

    ADS  Article  Google Scholar 

  11. 11.

    Steinhardt, P.J., Turok, N.: A cyclic model of the universe. Science 296, 1436 (2002)

    MathSciNet  ADS  MATH  Article  Google Scholar 

  12. 12.

    Steinhardt, P.J., Turok, N.: Cosmic evolution in a cyclic universe. Phys. Rev. D 65, 126003 (2002). arXiv:hep-th/0111098

    MathSciNet  ADS  Article  Google Scholar 

  13. 13.

    Penrose, R.: Cycles of Time. Random House, New York (2011)

    Google Scholar 

  14. 14.

    Gurzadyan, V.G., Penrose, R.: CCC-predicted low-variance circles in CMB sky and LCDM. arXiv:1104.5675

  15. 15.

    Gurzadyan, V.G., Penrose, R.: More on the low variance circles in CMB sky. arXiv:1012.1486

  16. 16.

    Gurzadyan, V.G., Penrose, R.: Concentric circles in WMAP data may provide evidence of violent pre-big-bang activity. arXiv:1011.3706

  17. 17.

    Wehus, I.K., Eriksen, H.K.: A search for concentric circles in the 7-year WMAP temperature sky maps. Astrophys. J. 733, L29 (2011). arXiv:1012.1268

    ADS  Article  Google Scholar 

  18. 18.

    Moss, A., Scott, D., Zibin, J.P.: No evidence for anomalously low variance circles on the sky. arXiv:1012.1305

  19. 19.

    Hajian, A.: Are there echoes from the pre-big bang universe? A search for low variance circles in the CMB sky. arXiv:1012.1656

  20. 20.

    Lehners, J.-L.: Diversity in the phoenix universe. arXiv:1107.4551

  21. 21.

    Lehners, J.-L., Steinhardt, P.J., Turok, N.: The return of the phoenix universe. Int. J. Mod. Phys. D 18, 2231–2235 (2009). arXiv:0910.0834

    ADS  MATH  Article  Google Scholar 

  22. 22.

    Smolin, L.: Did the universe evolve? Class. Quantum Gravity 9, 173–191 (1992)

    MathSciNet  ADS  Article  Google Scholar 

  23. 23.

    Smolin, L.: On the fate of black hole singularities and the parameters of the standard model. arXiv:gr-qc/9404011, CGPG-94/3-5

  24. 24.

    Smolin, L.: Using neutrons stars and primordial black holes to test theories of quantum gravity. arXiv:astro-ph/9712189

  25. 25.

    Smolin, L.: Cosmology as a problem in critical phenomena. In: Lopez-Pena, R., Capovilla, R., Garcia-Pelayo, R., Waalebroeck, H., Zertuche, F. (eds.) The Proceedings of the Guanajuato Conference on Complex Systems and Binary Networks. Springer, Berlin (1995). arXiv:gr-qc/9505022

    Google Scholar 

  26. 26.

    Smolin, L.: Experimental signatures of quantum gravity. In: The Proceedings of the Fourth Drexel Conference on Quantum Nonintegrability. International Press, Somerville (to appear). arXiv:gr-qc/9503027

  27. 27.

    Smolin, L.: Scientific alternatives to the anthropic principle. In: Carr, B., et al. (eds.) Universe or Multiverse. Cambridge University Press, Cambridge (2007). arXiv:hep-th/0407213

    Google Scholar 

  28. 28.

    Smolin, L.: The status of cosmological natural selection. arXiv:hep-th/0612185

  29. 29.

    Popper, K.: Conjectures and Refutations, pp. 33–39. Routledge & Keagan Paul, London (1963)

    Google Scholar 

  30. 30.

    Popper, K.: In: Schick, T. (ed.) Readings in the Philosophy of Science, pp. 9–13. Mayfield, Mountain View (2000)

    Google Scholar 

  31. 31.

    Popper, K.: In: Schick, T. (ed.) The Open Society and Its Enemies (1946)

    Google Scholar 

  32. 32.

    Popper, K.: In: Schick, T. (ed.) The Logic of Scientific Discovery (1959)

    Google Scholar 

  33. 33.

    Wheeler, J.A.: In: Rees, M., Ruffini, R., Wheeler, J.A. (eds.) Black Holes, Gravitational Waves and Cosmology. Gordon & Breach, New York (1974)

    Google Scholar 

  34. 34.

    Frolov, V.P., Markov, M.A., Mukhanov, M.A.: Through a black hole into a new universe? Phys. Lett. B 216, 272–276 (1989)

    MathSciNet  ADS  Article  Google Scholar 

  35. 35.

    Lawrence, A., Martinec, E.: String field theory in curved space-time and the resolution of spacelike singularities. Class. Quantum Gravity 13, 63 (1996). arXiv:hep-th/9509149

    MathSciNet  ADS  MATH  Article  Google Scholar 

  36. 36.

    Martinec, E.: Spacelike singularities in string theory. Class. Quantum Gravity 12, 941–950 (1995). arXiv:hep-th/9412074

    MathSciNet  ADS  MATH  Article  Google Scholar 

  37. 37.

    Bojowald, M.: Isotropic loop quantum cosmology. Class. Quantum Gravity 19, 2717–2742 (2002). arXiv:gr-qc/0202077

    MathSciNet  ADS  MATH  Article  Google Scholar 

  38. 38.

    Bojowald, M.: Inflation from quantum geometry. arXiv:gr-qc/0206054

  39. 39.

    Bojowald, M.: The semiclassical limit of loop quantum cosmology. Class. Quantum Gravity 18, L109–L116 (2001). arXiv:gr-qc/0105113

    MathSciNet  ADS  MATH  Article  Google Scholar 

  40. 40.

    Bojowald, M.: Dynamical initial conditions in quantum cosmology. Phys. Rev. Lett. 87, 121301 (2001). arXiv:gr-qc/0104072

    MathSciNet  ADS  Article  Google Scholar 

  41. 41.

    Tsujikawa, S., Singh, P., Maartens, R.: Loop quantum gravity effects on inflation and the CMB. arXiv:astro-ph/0311015

  42. 42.

    Gambini, R., Pullin, J.: Discrete quantum gravity: a mechanism for selecting the value of fundamental constants. Int. J. Mod. Phys. D 12, 1775–1782 (2003). arXiv:gr-qc/0306095

    MathSciNet  ADS  Article  Google Scholar 

  43. 43.

    Dirac, P.A.M.: The relation between mathematics and physics. Proc. R. Soc. Edinb. 59, 122–129 (1939)

    MATH  Google Scholar 

  44. 44.

    Peirce, C.S.: The architecture of theories. Monist (1891). Reprinted in Buchler, J. (ed.) Philosophical Writings of Peirce. Dover, New York (1955)

  45. 45.

    Leibniz, G.W.: The Monadology (1698), translated by Robert Latta, availabe at http://oregonstate.edu/instruct/phl302/texts/leibniz/monadology.html

  46. 46.

    Leibniz, G.W.: In: Francks, R., Woolhouse, R.S. (eds.) Oxford Philosophical Texts. Oxford University Press, London (1999)

    Google Scholar 

  47. 47.

    Alexander, H.G. (ed.): The Leibniz-Clarke Correspondence. Manchester University Press, Manchester (1956). For an annotated selection, see http://www.bun.kyoto-u.ac.jp?suchii/leibniz-clarke.html

    Google Scholar 

  48. 48.

    Rothman, T., Ellis, G.F.R.: Smolin’s natural selection hypothesis. Q. J. R. Astron. Soc. 34, 201–212 (1993)

    ADS  Google Scholar 

  49. 49.

    Vilenkin, A.: On cosmic natural selection. arXiv:hep-th/0610051

  50. 50.

    Harrison, E.R.: The natural selection of universes containing intelligent life. Q. J. R. Astron. Soc. 36(3), 193 (1995)

    ADS  Google Scholar 

  51. 51.

    Silk, J.: Review of Life of the Cosmos. Science 227, 644 (1997)

    Article  Google Scholar 

  52. 52.

    Brown, G.E., Bethe, H.A.: A scenario for a large number of low mass black holes in the Galaxy. Astrophys. J. 423, 659 (1994)

    ADS  Article  Google Scholar 

  53. 53.

    Brown, G.E.: Accretion onto and radiation from the compact object formed in SN1987A. Astrophys. J. 436, 843 (1994)

    ADS  Article  Google Scholar 

  54. 54.

    Brown, G.E.: The equation of state of dense matter: supernovae, neutron stars and black holes. Nucl. Phys. A 574, 217 (1994)

    ADS  Article  Google Scholar 

  55. 55.

    Brown, G.E.: Kaon condensation in dense matter. Preprint

  56. 56.

    Bethe, H.A., Brown, G.E.: Observational constraints on the maximum neutron star mass. Preprint

  57. 57.

    Lattimer, J.M., Prakash, M.: What a two solar mass neutron star really means. 4. To appear in Gerry Brown’s Festschrift; Editor: Sabine Lee (World Scientific). arXiv:1012.3208

  58. 58.

    Feeney, S.M., Johnson, M.C., Mortlock, D.J., Peiris, H.V.: First observational tests of eternal inflation: analysis methods and WMAP 7-year results. Phys. Rev. D 84, 043507 (2011). arXiv:1012.3667

    ADS  Article  Google Scholar 

  59. 59.

    Aguirre, A., Johnson, M.C.: A status report on the observability of cosmic bubble collisions. Rep. Prog. Phys. 74, 074901 (2011). arXiv:0908.4105

    ADS  Article  Google Scholar 

  60. 60.

    Carter, B.: In: Longair, M. (ed.) Confrontation of Cosmological Theories with Observational Data, IAU Symposium, vol. 63, p. 291. Reidel, Dordrecht (1974)

    Google Scholar 

  61. 61.

    Carr, B.J., Rees, M.J.: Nature 278, 605 (1979)

    ADS  Article  Google Scholar 

  62. 62.

    Carter, B.: The significance of numerical coincidences in nature. Unpublished preprint, Cambridge University (1967)

  63. 63.

    Barrow, J.D., Tipler, F.J.: The Anthropic Cosmological Principle. Oxford University Press, Oxford (1986)

    Google Scholar 

  64. 64.

    Smolin, L.: The Trouble with Physics. Houghton-Mifflin, Boston (2006)

    Google Scholar 

  65. 65.

    Weinberg, S.: Anthropic bound on the Cosmological Constant. Phys. Rev. Lett. 59, 2067 (1987)

    Article  Google Scholar 

  66. 66.

    Weinberg, S.: A priori probability distribution of the cosmological constant. Phys. Rev. D 61, 103505 (2000). arXiv:astro-ph/0002387

    MathSciNet  ADS  Article  Google Scholar 

  67. 67.

    Weinberg, S.: The cosmological constant problems. arXiv:astro-ph/0005265

  68. 68.

    Rees, M.J.: Anthropic Reasoning: clues to a fundamental theory. Complexity 3, 17 (1997)

    Article  Google Scholar 

  69. 69.

    Rees, M.J.: In: Wickramasinghe, C., et al. (eds.) Fred Hoyle’s Universe. Kluwer Academic, Dordrecht (2003). arXiv:astro-ph/0401424

    Google Scholar 

  70. 70.

    Tegmark, M., Rees, M.J.: Why is the CMB fluctuation level 10−5? Astrophys. J. 499, 526 (1998). arXiv:astro-ph/9709058

    ADS  Article  Google Scholar 

  71. 71.

    Graesser, M.L., Hsu, S.D.H., Jenkins, A., Wise, M.B.: Anthropic distribution for cosmological constant and primordial density perturbations. arXiv:hep-th/0407174

  72. 72.

    Garriga, J., Vilenkin, A.: Anthropic prediction for lambda and the Q catastrophe. Prog. Theor. Phys. Suppl. 163, 245–257 (2006). arXiv:hep-th/0508005

    MathSciNet  ADS  Article  Google Scholar 

  73. 73.

    Kragh, H.: Higher Speculations: Grand Theories and Failed Revolutions in Physics and Cosmology. Oxford University Press, London (2011)

    Google Scholar 

  74. 74.

    Ahmed, M., Dodelson, S., Greene, P.B., Sorkin, R.: Everpresent lambda. arXiv:astro-ph/0209274

  75. 75.

    Ellis, G., Smolin, L.: The weak anthropic principle and the landscape of string theory. arXiv:0901.2414 [hep-th]

  76. 76.

    DeWolfe, O., Giryavets, A., Kachru, S., Taylor, W.: Type IIA moduli stabilization (2005). arXiv:hep-th/0505160

  77. 77.

    Shelton, J., Taylor, W., Wecht, B.: Generalized flux vacua (2006). arXiv:hep-th/0607015

  78. 78.

    Freidel, L.: Reconstructing AdS/CFT. arXiv:0804.0632

  79. 79.

    Gomes, H., Gryb, S., Koslowski, T., Mercati, F.: The gravity/CFT correspondence. arXiv:1105.0938

  80. 80.

    Mangabeira Unger, R., Smolin, L.: Book manuscript in preparation

Download references


I am grateful to Roberto Mangabeira Unger for proposing a collaboration on evolving laws of nature which stimulated and sharpened many of the ideas and arguments contained here. Results of our joint work, on which this essay is partially based, will be published in [80]. I am grateful to many colleagues at Perimeter Institute including Niayesh Afshordi, Latham Bole, Matt Johnson and Neil Turok for conversations on these issues. I have also learned a great deal from the opportunity to listen to conferences where various attempts to resolve the landscape problem were critically examined. Research at Perimeter Institute for Theoretical Physics is supported in part by the Government of Canada through NSERC and by the Province of Ontario through MRI.

Author information



Corresponding author

Correspondence to Lee Smolin.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Smolin, L. A Perspective on the Landscape Problem. Found Phys 43, 21–45 (2013). https://doi.org/10.1007/s10701-012-9652-x

Download citation


  • String theory
  • Landscape