# Rodica Simion

**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]}

## Research contributions

Simion's thesis research concerned the concavity and unimodality of certain combinatorially defined sequences,^{[4]} 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]}^{[4]} The "simsun permutations" were named after her and Sheila Sundaram, after their initial studies of these objects;^{[5]}^{[6]} 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.^{[7]}

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]}^{[8]} 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;^{[5]}^{[9]} her poem "Immigrant Complex" was published in a collection of mathematical poetry in 1979.^{[10]}

## 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 728500. - 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 829358. - 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.

## References

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