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Background

I hail from Bucharest, Romania. I did my undergraduate studies at the Faculty of Mathematics of the University of Bucharest. Here is a picture from those days.

For my graduate studies, I went to Columbia University, receiving my Ph.D. degree in 1984. Here is a picture from around that time, taken in Cambridge, UK.

After a J.W. Gibbs Instructorship at Yale University, I came in 1986 to Northeastern University, where I've been ever since.

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Research

My research interests are in Topology, and how it relates to Algebra, Geometry, and Combinatorics. I currently investigate cohomology jumping loci, and their applications to algebraic varieties, low-dimensional topology, and toric topology, such as the study of hyperplane arrangements, Milnor fibrations, moment angle complexes, configuration spaces, and various classes of knots, links, and manifolds, as well as the homology and lower central series of discrete groups. Below are some recent papers and preprints (click here and here for a complete list).

- Flat connections and resonance varieties: from rank one to higher ranks (with A.D. Macinic, S. Papadima, C.R. Popescu),
*Trans. Amer. Math. Soc.* 369 (2017), no. 2, 1309-1343.
- On the topology of the Milnor fibration of a hyperplane arrangement,
*Rev. Roumaine Math. Pures Appl.* 62 (2017), no. 1, 191-215.
- The Milnor fibration of a hyperplane arrangement: from modular resonance to algebraic monodromy (with S. Papadima),
*Proc. London Math. Soc.* 114 (2017), no. 6, 961-1004.
- Pure virtual braids, resonance, and formality (with H. Wang),
*Math. Zeit.* 286 (2017), no. 3-4, 1495-1524.
- Abelian duality and propagation of resonance (with G. Denham and S. Yuzvinsky),
*Selecta Math.* 23 (2017), no. 4, 2331-2367.
- The pure braid groups and their relatives (with H. Wang), in:
*Perspectives in Lie theory*, 403-426, Springer INdAM series, vol. 19, Springer, Cham, 2017.
- Functional classification of protein structures by local structure matching in graph representation (with C. Mills, R. Garg, J. S. Lee, L. Tian, G. Cooperman, P. J. Beuning, and M. J. Ondrechen),
*Protein Science* 27 (2018), no. 6, 1125-1135.
- Local systems on arrangements of smooth, complex algebraic hypersurfaces (with G. Denham),
*Forum Math. Sigma* 6 (2018), e6, 20 pages, doi:10.1017/fms.2018.5.
- Infinitesimal finiteness obstructions (with S. Papadima),
*J. London Math. Soc.* 99 (2019), no. 1, 173-193.
- Cup products, lower central series, and holonomy Lie algebras (with H. Wang),
*J. Pure Appl. Alg.* 223 (2019), no. 8, 3359-3385.
- Naturality properties and comparison results for topological and infinitesimal embedded jump loci (with S. Papadima),
*Adv. in Math.* 350 (2019), 256-303.
- Formality properties of finitely generated groups and Lie algebras (with H. Wang),
*Forum Math.* 31 (2019), no. 4, 867-905.
- Chen ranks and resonance varieties of the upper McCool groups (with H. Wang),
*Adv. in Appl. Math.* 110 (2019), 197-234.
- The topology of compact Lie group actions through the lens of finite models (with S. Papadima),
*Int. Math. Res. Notices IMRN* 2019 (2019), no. 20, 6390-6436.
- Rank two topological and infinitesimal embedded jump loci of quasi-projective manifolds (with S. Papadima),
*J. Inst. Math. Jussieu* 19 (2020), no. 2, 451-485.
- Residually finite rationally
*p* groups (with T. Koberda), *Commun. Contemp. Math.* 22 (2020), no. 3, 1950016 (44 pages).
- Homology, lower central series, and hyperplane arrangements (with R.D. Porter),
*Eur. J. Math.* 6 (2020), nr. 3, 1039-1072.
- Taylor expansions of groups and filtered-formality (with H. Wang),
*Eur. J. Math.* 6 (2020), nr. 3, 1073-1096.
- Poincaré duality and resonance varieties,
*Proc. Roy. Soc. Edinburgh Sect. A.* (2019).
- Cohomology jump loci of 3-manifolds,
*Manuscripta Math.* (to appear).
- Sigma-invariants and tropical varieties, preprint Oct. 2020.

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Teaching

I teach a variety of math courses, both at the undergraduate and graduate level. If you are interested in taking a directed study course or a reading course with me (in addition to those courses regularly offered), please contact me.

- In Fall 2016, I taught MATH 3150, an undergraduate course in Real Analysis, and MATH 7221, a graduate Topology 2 course.
- In Spring 2017, I taught MATH 7321, a graduate Topology 3 course.
- In Spring 2018, I taught MATH 4565, an undergraduate course in Topology.
- In Fall 2018, I taught MATH 7221, a graduate Topology 2 course.
- In Summer-2 2020, I taught MATH 3175, an undergraduate course in Group Theory.