Joel David Hamkins

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Joel David Hamkins
Nationality American
Alma mater University of California, Berkeley
California Institute of Technology
Scientific career
Fields Mathematics, Philosophy
Institutions City University of New York
Doctoral advisor W. Hugh Woodin

Joel David Hamkins is an American mathematician and philosopher based at the City University of New York. He has made contributions in mathematical and philosophical logic, particularly set theory and the philosophy of set theory, in computability theory, and in group theory.


After earning a B.S. in mathematics at the California Institute of Technology, Hamkins earned his Ph.D. in mathematics in 1994 at the University of California, Berkeley under the supervision of W. Hugh Woodin, with a dissertation entitled Lifting and Extending Measures by Forcing; Fragile Measurability. He joined the faculty of the City University of New York in 1995, where he is a member of the doctoral faculties in Mathematics, in Philosophy and in Computer Science at the CUNY Graduate Center and professor of mathematics at the College of Staten Island. He has also held various faculty or visiting fellow positions at University of California at Berkeley, Kobe University, Carnegie Mellon University, University of Muenster, Georgia State University, University of Amsterdam, the Fields Institute, New York University and the Isaac Newton Institute.

In September 2018, Hamkins will move to the University of Oxford to become Professor of Logic in the Faculty of Philosophy and Sir Peter Strawson Fellow in Philosophy in University College, Oxford.[1]

Research contributions[edit]

Hamkins research work is cited,[2] and he gives talks,[3] including events for the general public.[4][5][6][7] Hamkins was interviewed on his research by Richard Marshall in 2013 for 3:AM Magazine, as part of an ongoing interview series for that magazine of prominent philosophers and public intellectuals,[8] and he is occasionally interviewed by the popular science media about issues in the philosophy of mathematics.[9][10]

Set theory[edit]

In set theory, Hamkins has investigated the indestructibility phenomenon of large cardinals, proving that small forcing necessarily ruins the indestructibility of supercompact and other large cardinals[11] and introducing the lottery preparation as a general method of forcing indestructibility.[12] Hamkins introduced the modal logic of forcing and proved with Benedikt Löwe that if ZFC is consistent, then the ZFC-provably valid principles of forcing are exactly those in the modal theory known as S4.2.[13] Hamkins, Linetsky and Reitz proved that every countable model of Gödel-Bernays set theory has a class forcing extension to a pointwise definable model, in which every set and class is definable without parameters.[14] Hamkins and Reitz introduced the ground axiom, which asserts that the set-theoretic universe is not a forcing extension of any inner model by set forcing. Hamkins proved that any two countable models of set theory are comparable by embeddability, and in particular that every countable model of set theory embeds into its own constructible universe.[15]

Philosophy of set theory[edit]

In his philosophical work, Hamkins has defended a multiverse perspective of mathematical truth,[16][17] arguing that diverse concepts of set give rise to different set-theoretic universes with different theories of mathematical truth. He argues that the Continuum Hypothesis question, for example, "is settled on the multiverse view by our extensive knowledge about how it behaves in the multiverse, and as a result it can no longer be settled in the manner formerly hoped for." (Hamkins 2012) Elliott Mendelson writes of Hamkins's work on the set-theoretic multiverse that, "the resulting study is an array of new fantastic, and sometimes bewildering, concepts and results that already have yielded a flowering of what amounts to a new branch of set theory. This ground-breaking paper gives us a glimpse of the amazingly fecund developments spearheaded by the author and...others..."[18]

Infinitary computability[edit]

Hamkins introduced with Jeff Kidder and Andy Lewis the theory of infinite-time Turing machines, a part of the subject of hypercomputation, with connections to descriptive set theory.[19]

In other computability work, Hamkins and Miasnikov proved that the classical halting problem for Turing machines, although undecidable, is nevertheless decidable on a set of asymptotic probability one, one of several results in generic-case complexity showing that a difficult or unsolvable problem can be easy on average.[20]

Group theory[edit]

In group theory, Hamkins proved that every group has a terminating transfinite automorphism tower.[21] With Simon Thomas, he proved that the height of the automorphism tower of a group can be modified by forcing.

Infinite chess[edit]

On the topic of infinite chess, Hamkins, Brumleve and Schlicht proved that the mate-in-n problem of infinite chess is decidable.[22] Hamkins and Evans investigated transfinite game values in infinite chess, proving that every countable ordinal arises as the game value of a position in infinite three-dimensional chess.[23]


Hamkins is the top-rated[24] user by reputation score on MathOverflow.[25][26][27] Gil Kalai describes him as "one of those distinguished mathematicians whose arrays of MO answers in their areas of interest draw coherent deep pictures for these areas that you probably cannot find anywhere else."[28]


  1. ^ Hamkins, Joel David (May 17, 2018). "Oxford University, Professor of Logic & Sir Peter Strawson Fellow, University College Oxford". 
  2. ^ J. D. Hamkins: Google Scholar profile.
  3. ^ List of talks, from Hamkins's web page.
  4. ^ The Span of Infinity, Helix Center roundtable, October 25, 2014. (Hamkins was a panelist.)
  5. ^ J. D. Hamkins, plenary General Public Lecture, Higher infinity and the Foundations of Mathematics, American Association for the Advancement of Science, Pacific Division, June, 2014.
  6. ^ A Meeting at the Crossroads - Science, Performance and the Art of Possibility, The Intrinsic Value Project, Underground Zero, New York City, July 9 & 10, 2014. (Hamkins was a panelist.)
  7. ^ The Future of Infinity: Solving Math's Most Notorious Problem, World Science Festival, New York City, June 1, 2013. (Hamkins was a panelist.)
  8. ^ Richard Marshall, Playing Infinite Chess, 3AM Magazine, March 25, 2013.
  9. ^ Jacob Aron, Mathematicians Think Like Machines for Perfect Proofs New Scientist, 26 June 2013.
  10. ^ Erica Klarreich, Infinite Wisdom, Science News, Volume 164, No. 9, August 30, 2003, p. 139.
  11. ^ David Hamkins, Joel (1998). "Small Forcing Makes any Cardinal Superdestructible". The Journal of Symbolic Logic. 63 (1): 51–58. arXiv:1607.00684Freely accessible. doi:10.2307/2586586. 
  12. ^ David Hamkins, Joel (2000). "The Lottery Preparation". Annals of Pure and Applied Logic. 101 (2–3): 103–146. doi:10.1016/S0168-0072(99)00010-X. 
  13. ^ David Hamkins, Joel; Löwe, Benedikt (2008). "The modal logic of forcing". Transactions of the American Mathematical Society. 360 (4): 1793–1817. arXiv:math/0509616Freely accessible. doi:10.1090/s0002-9947-07-04297-3. 
  14. ^ David Hamkins, Joel (2013). "David Linetsky and Jonas Reitz, Pointwise definable models of set theory". The Journal of Symbolic Logic. 78 (1): 139–156. arXiv:1105.4597Freely accessible. doi:10.2178/jsl.7801090. 
  15. ^ David Hamkins, Joel (2013). "Every countable model of set theory embeds into its own constructible universe". J. Math. Log. 13 (2): 1350006. doi:10.1142/S0219061313500062. 
  16. ^ "The set-theoretic multiverse". The Review of Symbolic Logic. 5 (03): 416–449. 2012. doi:10.1017/S1755020311000359. 
  17. ^ J. D. Hamkins, The multiverse perspective on determinateness in set theory, talk at the Exploring the Frontiers of Incompleteness, Harvard University, October 19, 2011. video
  18. ^ Elliott Mendelson, Zentralblatt review of J. D. Hamkins, The set-theoretic multiverse, Review of Symbolic Logic, 5, No. 3, 416-449 (2012), Zbl 1260.03103.
  19. ^ David Hamkins, Joel; Lewis, Andy (2000). "Infinite-time Turing machines". The Journal of Symbolic Logic. 65 (02): 567–604. doi:10.2307/2586556. 
  20. ^ David Hamkins, Joel; Miasnikov, Alexei (2006). "The Halting Problem Is Decidable on a Set of Asymptotic Probability One". Notre Dame J. Formal Logic. 47 (4): 515–524. doi:10.1305/ndjfl/1168352664. 
  21. ^ "Every group has a terminating automorphism tower". Proceedings of the American Mathematical Society. 126 (11): 3223–3226. 1998. doi:10.1090/s0002-9939-98-04797-2. 
  22. ^ Brumleve, Dan; David Hamkins, Joel; Schlicht, Philipp (2012). "The mate-in-n problem of infinite chess is decidable, in How the World Computes". Lecture Notes in Computer Science. 7318: 78–88. doi:10.1007/978-3-642-30870-3_9. 
  23. ^ C. D. A. Evans and J. D. Hamkins, "Transfinite game values in infinite chess," Integers, volume 14, Paper No. G2, 36, 2014.
  24. ^ MathOverflow users, by reputation score.
  25. ^ MathOverflow announcement of Hamkins breaking 100,000 reputation score, September 17, 2014.
  26. ^ MathOverflow announcement of Hamkins posting 1000th answer, January 30, 2014.
  27. ^ Erica Klarreich, The Global Math Commons, Simons Foundation Science News, May 18, 2011.
  28. ^ Gil Kalai on Hamkins's MathOverflow achievements, January 29, 2014.

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