Rodica Simion

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Rodica Eugenia Simion (January 18, 1955 – January 7, 2000) was a Romanian-American mathematician. She was the Columbian School Professor of Mathematics at George Washington University. Her research concerned combinatorics: she was a pioneer in the study of permutation patterns, and an expert on noncrossing partitions.


Simion was one of the top competitors in the Romanian national mathematical olympiads.[1] She graduated from the University of Bucharest in 1974, and immigrated to the United States in 1976.[2] She did her graduate studies at the University of Pennsylvania, earning a Ph.D. in 1981 under the supervision of Herbert Wilf.[2][3] After teaching at Southern Illinois University and Bryn Mawr College, she moved to George Washington University in 1987, and became Columbian School Professor in 1997.[2]


She is included in a deck of playing cards featuring notable women mathematicians published by the Association of Women in Mathematics.[4]

Research contributions[edit]

Simion's thesis research concerned the concavity and unimodality of certain combinatorially defined sequences,[5] and included what Richard P. Stanley calls "a very influential result" that the zeros of certain polynomials are all real.[2]

Next, with Frank Schmidt, she was one of the first to study the combinatorics of sets of permutations defined by forbidden patterns; she found a bijective proof that the stack-sortable permutations and the permutations formed by interleaving two monotonic sequences are equinumerous, and found combinatorial enumerations of many permutation classes.[2][5] The "simsun permutations" were named after her and Sheila Sundaram, after their initial studies of these objects;[6][7] a simsun permutation is a permutation in which, for all k, the subsequence of the smallest k elements has no three consecutive elements in decreasing order.[8]

Simion also did extensive research on noncrossing partitions, and became "perhaps the world's leading authority" on them.[2]

Other activities[edit]

Simion was the main organizer of an exhibit about mathematics, Beyond Numbers, at the Maryland Science Center, based in part on her earlier experience organizing a similar exhibit at George Washington University.[2][9] She was also a leader in George Washington University's annual Summer Program for Women in Mathematics.[2] As well as being a mathematician, Simion was a poet and painter;[6][10] her poem "Immigrant Complex" was published in a collection of mathematical poetry in 1979.[11]

Selected publications[edit]

  • Simion, Rodica (1984), "A multi-indexed Sturm sequence of polynomials and unimodality of certain combinatorial sequences", Journal of Combinatorial Theory, Series A, 36 (1): 15–22, doi:10.1016/0097-3165(84)90075-X, MR 0728500.
  • Simion, Rodica; Schmidt, Frank W. (1985), "Restricted permutations", European Journal of Combinatorics, 6 (4): 383–406, doi:10.1016/s0195-6698(85)80052-4, MR 0829358.
  • Simion, Rodica; Ullman, Daniel (1991), "On the structure of the lattice of noncrossing partitions", Discrete Mathematics, 98 (3): 193–206, doi:10.1016/0012-365X(91)90376-D, MR 1144402.
  • Simion, Rodica (2000), "Noncrossing partitions", Discrete Mathematics, 217 (1–3): 367–409, doi:10.1016/S0012-365X(99)00273-3, MR 1766277.

See also[edit]


  1. ^ Crapanzano, Theresa (January 20, 2000), "GW mourns after math professor passes away", The GW Hatchet.
  2. ^ a b c d e f g h Stanley, Richard P. (2000), "Rodica Simion: January 18, 1955 – January 7, 2000" (PDF), Pi Mu Epsilon Journal, 11: 83–86.
  3. ^ Rodica Simion at the Mathematics Genealogy Project
  4. ^ "Mathematicians of EvenQuads Deck 1",, retrieved 2022-06-18
  5. ^ a b Wilf, Herbert (January 2000), Rodica Simion (1955–2000), Remarks at a special session of an AMS meeting in Washington, D.C..
  6. ^ a b Zeilberger, Doron (January 2000), RODICA SIMION (1955-2000): An (almost) Perfect Enumerator and Human Being.
  7. ^ Sundaram, Sheila (2002), "Reminiscences of Rodica Simion", Advances in Applied Mathematics, 28 (3–4): 285–286, doi:10.1006/aama.2001.0785, MR 1899997.
  8. ^ Deutsch, Emeric; Elizalde, Sergi (2012), "Restricted simsun permutations", Annals of Combinatorics, 16 (2): 253–269, arXiv:0912.1361, doi:10.1007/s00026-012-0129-6, MR 2927606, S2CID 115172092.
  9. ^ Bonin, Joseph E. (2002), "A remembrance of Rodica Simion", Advances in Applied Mathematics, 28 (3–4): 280–281, doi:10.1006/aama.2001.0783, MR 1899995.
  10. ^ Kalai, Gil (January 7, 2000), Rodica Simion: Immigrant Complex, Combinatorics and more.
  11. ^ Robson, Ernest M.; Wimp, Jet, eds. (1979), Against infinity: an anthology of contemporary mathematical poetry, Primary Press, pp. 65–66, ISBN 9780934982016.