Research & Publications

I am broadly interested in algebraic geometry, with a focus on the use of logarithmic and tropical methods to establish results about the geometry of curves, moduli spaces, and enumerative geometry. A complete list of papers is available here, as well as on arXiv and GoogleScholar.

Selected Publications and Preprints

  • Logarithmic Gromov-Witten theory with expansions (2019). This project concerns the Gromov-Witten theory of degenerations, and especially those of normal crossings type. The main result establishes a formula for the Gromov-Witten invariants of a smooth fiber in a degeneration in terms of the invariants of strata in a degenerate fiber. It generalizes a celebrated formula due to Jun Li. The geometric input, via Abramovich-Karu semistable reduction theory, is the construction of new moduli spaces of stable maps to expansions of a target along the strata of a normal crossings divisor. The result can be viewed as an algebraic manifestation of a multifold symplectic sum formula. (Under review)
  • Moduli of stable maps in genus one & logarithmic geometry, Volumes I & II (2017) & Curve counting in genus one: relative geometry & elliptic singularities (2019). These three papers, the first two with Keli Santos-Parker and Jonathan Wise, and the final one with Luca Battistella and Navid Nabijou, investigate the relationship between tropical geometry, Gromov-Witten theory, and the structure of elliptic curve singularities. The first paper establishes the basic theory of radially aligned curves and contractions, and relates it to Smyth's work on pointed elliptic curves. The second paper applies this to solve the tropical inverse problem for curves in genus one, and desingularizes genus one logarithmic stable map spaces for toric targets. The final paper puts all this theory into practice, establishing new recursive algorithms for relative geometries, and explains the interaction between elliptic singularities and the splitting and degeneration formulas (Volume I in Geometry & Topology, Volume II in Algebra & Number Theory, final paper under review)
  • Brill-Noether theory for curves of a fixed gonality (2017). The Brill-Noether theorem governs the complexity of embeddings of smooth algebraic curves in projective space, when the complex structure on the curve is general. This paper, written with Dave Jensen, is a generalization of this theorem for curves which are general within a prescribed special locus. More precisely, we give a closed formula for the dimension of Brill-Noether varieties for general curves of a fixed gonality. The result was conjectured in earlier work of Nathan Pflueger, and provides an interpolation between the Brill-Noether theorem for general curves and Clifford's theorem for hyperelliptic curves. Hannah Larson has pushed these results in a beautiful direction. (Under review)
  • Skeletons of stable maps I: rational curves in toric varieties (2016). This paper constructs the moduli space of logarithmic stable maps from genus 0 curves to toric varieties in an elementary geometric fashion using non-archimedean and tropical geometry. The paper generalizes Tevelev's work on tropical compactifications for the space of pointed rational curves, as well as joint work with Cavalieri and Markwig when the target is a projective line. The result provides a very direct avenue of access to the geometry of these spaces. (Journal of the London Mathematical Society)
  • Tropicalizing the space of admissible covers (2014). The moduli space of admissible covers is a compactification of the Hurwitz scheme. In this paper with Renzo Cavalieri and Hannah Markwig, we identify a precise relationship between the non-archimedean analytic skeleton of this space and a tropical moduli space, using a framework outlined by Abramovich-Caporaso-Payne. The equality of tropical and algebraic Hurwitz numbers is established as a consequence. The latter is a general blueprint that explains why enumerative information survives the tropicalization process. (Mathematische Annalen)

Collaborators on ongoing work: Luca Battistella, Francesca Carocci, Yoav Len, Davesh Maulik, Navid Nabijou, Martin Ulirsch.