I hail from Bucharest, Romania. After completing high school, 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.

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.

Recent papers and preprints

• 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. Porter), Eur. J. Math. 6 (2020), no. 3, 1039–1072.
• Taylor expansions of groups and filtered-formality (with H. Wang), Eur. J. Math. 6 (2020), no. 3, 1073–1096.
• Poincaré duality and resonance varieties, Proc. Roy. Soc. Edinburgh Sect. A. 150 (2020), no. 6, 3001–3027.
• Sigma-invariants and tropical varieties, Math. Annalen 380 (2021), no. 3-4, 1427–1463.
• Cohomology jump loci of 3-manifolds, Manuscripta Math. 67 (2022), no. 1-2, 89–123.
• Differential graded algebras, Steenrod cup-one products, binomial operations, and Massey products (with R. Porter), Topology Appl. 313 (2022), 107987.
• Cohomology, Bocksteins, and resonance varieties in characteristic 2, 131–157, Contemp. Math., vol. 790, Amer. Math. Soc., 2023
• Formality and finiteness in rational homotopy theory, EMS Surv. Math. Sci. 10 (2023), no. 2, 321–403.
• Higher resonance schemes and Koszul modules of simplicial complexes (with M. Aprodu, G. Farkas, C. Raicu, and A. Sammartano), J. Algebraic Combin 59 (2024), no. 4, 787–805.
• Alexander invariants and cohomology jump loci in group extensions, Ann. Sc. Norm. Super. Pisa 25 (2024), no. 2, 1085–1154.
• Milnor fibrations of arrangements with trivial algebraic monodromy, Rev. Roumaine Math. Pures Appl. 69 (2024), no. 2, 235–293.
• Reduced resonance schemes and Chen ranks (with M. Aprodu, G. Farkas, and C. Raicu), J. Reine Angew. Math. 814 (2024), 205–240.
• Lower central series and split extensions, preprint May 2021.
• Cup-one algebras and 1-minimal models (with R. Porter), preprint June 2023.
• On the topology and combinatorics of decomposable arrangements, preprint April 2024.

Teaching

I teach a variety of math courses, both at the undergraduate and graduate levels. 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 2021, I taught MATH 4565, an undergraduate course in Topology.
• In Spring 2022, I taught MATH 7721, a Readings in Topology course.
• In Summer-2 2022, I taught MATH 3175, an undergraduate course in Group Theory.
• In Fall 2022, I taught MATH 3150, an undergraduate course in Real Analysis, and MATH 4565, an undergraduate course in Topology.
• In Fall 2023, I taught MATH 3150 Real Analysis and MATH 4565 Topology.
• In Spring 2024, I taught MATH 3175, an undergraduate course in Group Theory.
• In Fall 2024, I teach MATH 3150 Real Analysis and MATH 4565 Topology.
• In Spring 2025, I will teach MATH 3150 Real Analysis.

Activities

• In 2021, I participated in a couple of virtual meetings: a workshop on Logarithmic Vector Fields and Freeness of Divisors and Arrangements, hosted by MFO Oberwolfach, and the TIBĂR60 Conference, hosted by the University of Wisconsin-Madison. In October, I organized with Peter Crooks a conference on Compactifications, Configurations, and Cohomology at Northeastern, the proceedings of which will soon appear in an AMS Contemporary Mathematics volume. Also in the fall of 2021, I got back on the road and I gave talks at the conference in Algebraic Geometry for Alexandru Dimca’s retirement, held in Ischia, Italy, and at the conference on Braids, Links, and Applications, held at IMSA, University of Miami.
• In spring 2022, I participated in a workshop on Braids held at ICERM in Providence, RI and I visited IMAR in Bucharest, Romania. In May–June I was at CIRM in Trento, Italy on a Research in Pairs stay, then visited again IMAR in Bucharest, after which I participated and gave a talk at the Arrangements in Ticino conference in Locarno, Switzerland. In November I was in Germany, where I participated in a conference on Resonance, topological invariants of groups, and moduli at Humboldt University Berlin and a workshop on Pfaffians, tensors, and applications at MPI MiS Leipzig.
• In January–February 2023, I visited the Sydney Mathematical Research Institute at the University of Sydney. In March, I participated in a workshop on Various guises of reflection arrangements at ICMS in Edinburgh, UK, and made brief visits at UC Louvain in Belgium and the University of Strasbourg in France. Back in Boston, I gave seminar talks at Tufts and Harvard, and participated in the Auslander Conference in Woods Hole, MA. In May-July, I visited IMAR in Bucharest, during which time I participated in a conference on Algebraic and topological interplay of algebraic varieties in Jaca, Spain, a research school on Singularities and Applications at the University of Lille, France, the Tenth Congress of Romanian Mathematicians in Pitești, and a
• In January–February 2023, I visited the Sydney Mathematical Research Institute at the University of Sydney. In March, I participated in a workshop on Various guises of reflection arrangements at ICMS in Edinburgh, UK, and made brief visits at UC Louvain in Belgium and the University of Strasbourg in France. Back in Boston, I gave seminar talks at Tufts and Harvard, and participated in the Auslander Conference in Woods Hole, MA. In May-July, I visited IMAR in Bucharest; during that time, I gave a couple of seminar talks and participated in a conference on Algebraic and topological interplay of algebraic varieties in Jaca, Spain, a research school on Singularities and Applications at the University of Lille, France, the Tenth Congress of Romanian Mathematicians in Pitești, and a conference on Geometry, Topology and Algebra of Singular Spaces at IMAR. Finally, in December I participated in a conference on Hyperplane Arrangements at Rikkyo University in Tokyo, Japan, and visited Osaka University, where I gave a seminar talk.
• In March 2024, I participated in a workshop on Artin groups and arrangements at SLMath in Berkeley, CA. In May, I visited the University of Berlin, where I gave a seminar talk, and then gave a series of lectures at the Master class on Hodge theory and cohomological jump loci at Stockholm University. In June, I participated in a workshop on Arrangements, matroids and logarithmic vector fields at MFO in Oberwolfach, Germany, while in late July, I participated in a workshop on Polyhedral products at the Fields Institute in Toronto, Canada.

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