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.

Biography

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]

Recognition

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

Research contributions

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

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

• 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

• Cyclohedron

References