Stefano Marseglia



Papers

The papers are umbered according to their appearance on the arXiv. Unless otherwise mentioned, the arXiv and HAL versions coincide with the accepted version of the paper.
Preprints
  1. Isogeny graphs of abelian varieties and singular ideals in orders
    with Sarah Arpin and Caleb Springer
    arXiv --- HAL --- Magma code
  2. Abelian varieties over finite fields with commutative endomorphism algebra: theory and algorithms
    with Jonas Bergström and Valentijn Karemaker
    arXiv --- HAL --- Magma code --- code (examples)
Journals
  1. Ordinary abelian varieties: isogeny graphs and polarizations
    with Edgar Costa, Taylor Dupuy, David Roe, Christelle Vincent
    to appear in Research in Number Theory, part of the proceedings of the Sixteenth Algorithmic Number Theory Symposium (ANTS XVII).
    Awarded a prize for "Most reproducible code".
    arXiv (submitted version) --- HAL (submitted version) --- Magma code
  2. Weil polynomials of small degree
    Indagationes Mathematicae 37 (2026) no. 4, 1093-1116.
    journal (open access) --- arXiv --- HAL
  3. Labeling abelian varieties over finite fields
    with Edgar Costa, Taylor Dupuy, David Roe and Christelle Vincent
    in LuCaNT: Databases, Algorithms, and Computational Number Theory, (2026) Contemp. Math. 840, 277-283.
    journal --- arXiv --- HAL --- Magma code
  4. Abelian surfaces over finite fields containing no curves of genus 3 or less
    with Elena Berardini and Alejandro Giangreco Maidana
    Journal of Pure and Applied Algebra 230 (2026), no. 4, 108229.

    journal (open access) --- arXiv --- HAL
  5. Local isomorphism classes of fractional ideals of orders in étale algebras
    Journal of Algebra 673 (2025), 77-102.
    journal (open access) --- arXiv --- Magma code
  6. Abelian varieties over finite fields and their groups of rational points
    with Caleb Springer
    Algebra & Number Theory 19 (2025), no. 3, 521-550.
    journal (open access) --- arXiv (minor differences with the published version)
  7. Ideal classes of orders in quaternion algebras
    with Harry Smit and an Appendix by John Voight
    Journal of Pure and Applied Algebra 228 (2024), no. 7, 107649.

    journal (open access) --- arXiv --- Magma code
  8. Modules over orders, conjugacy classes of integral matrices, and abelian varieties over finite fields
    Research in Number Theory 11 (2025) no. 1, paper No. 27. part of the proceedings of the Sixteenth Algorithmic Number Theory Symposium (ANTS XVI).
    journal (open access) --- arXiv --- HAL --- Magma code for examples
  9. Cohen-Macaulay type of orders, generators and ideal classes
    Journal of Algebra 658 (2024), 247-276.
    journal (open access) --- arXiv --- Magma code
  10. Every finite abelian group is the group of rational points of an ordinary abelian variety over F2,F3 and F5
    with Caleb Springer
    Proceedings of the American Mathematical Society 151 (2023), no. 2, 501-510.
    journal --- arXiv
  11. Polarizations of abelian varieties over finite fields via canonical liftings,
    with Jonas Bergström and Valentijn Karemaker
    International Mathematics Research Notices. IMRN (2023), no.4, 3194-3248.
    journal (open access) --- arXiv --- Magma code --- code (examples)
  12. Products and Polarizations of Super-Isolated Abelian Varieties,
    with Travis Scholl
    Mathematische Zeitschrift, 300 (2022), no. 1, 445-462.
    journal (open access) --- arXiv --- Sage code
  13. Computing base extensions of ordinary abelian varieties over a finite field,
    International Journal of Number Theory 18 (2022), no. 9, 1957-1974.
    journal --- arXiv --- code (examples)
  14. Computing abelian varieties over finite fields isogenous to a power,
    Research in number theory 5 (2019), no. 4, paper no. 35.
    journal (open access) --- arXiv --- code (examples)
  15. Computing square-free polarized abelian varieties over finite fields,
    Mathematics of Computation 90 (2021), no. 328, 953-971.
    journal --- arXiv --- code (examples)
  16. Computing the ideal class monoid of an order,
    Journal of the London Mathematical Society 101 (2020), no. 3, 984-1007.
    journal --- arXiv
  17. Super-multiplicativity of ideal norms in number fields,
    Acta Arithmetica 193 (2020), no. 1, 75-93.
    journal --- arXiv
PhD thesis
  • Computing abelian varieties over finite fields,
    PhD thesis, defended on June 8, 2018, permanent link

Data

Data about endomorphism rings and polarizations of abelian varieties over finite fields for isogeny classes of abelian varieties is now on the LMFDB xyz.
Here are some examples:

Computer Packages

I mostly code in Magma. Here is a list of Magma tips and tricks I learned and collected.
Instructions on how to use each package are included in the attached README files.
We invite also to look at the code to produce the examples for the corresponding papers.
Don't hesitate to contact me if you have questions and/or comments!
AlgEt - part of Magma, since v2.29 - GitHub
- It provides functionalities to compute with orders in étale algebras over Q.
- In particular, one can compute isomorphism classes of modules and the monoid of the ideal classes of the fractional ideals of the order.
- The version available through GitHub includes functionalities for isomorphism classes of finitely generated modules over orders, which are not part of a Magma release.
- This packages is based on theory developed in Papers [3], [9], [10] and [13].
IdlClQuat - Magma - GitHub
- It provides functionalities to compute the isomorphism classes of ideals of an order in a quaternion algebra.
- This is a collaboration with Harry Smit.
- Currently, there is no plan to expand it.
- This packages is based on theory developed in Paper [11].
AbVarFq - Magma - GitHub
- It provides functionalities to compute isomorphism classes of abelian varieties (in the ordinary case and over a prime field) and polarizations (in the ordinary case).
- The package requires AlgEt.
- This packages is based on theory developed in Papers [3], [4] and [5].
PolsAbVarFpCanLift - Magma - GitHub
- It provides functionalities to compute polarizations for squarefree isogeny classes of abelian varieties over a prime field even when they are not ordinary.
- It is an expansion of the package AbVarFq.
- The package requires AbVarFq (and its dependencies).
- This packages is based on theory developed in Paper [7].
IsomClAbVarFqCommEndAlg - Magma - GitHub
- It provides functionalities to compute (unpolarized) Fq-isomorphism classes of abelian varieties over Fq belonging to an isogeny class with commutative Fq-endomorphism ring, for any finite field Fq. In particular, the code works for any p-rank. - It is an expansion of the package AbVarFq.
- This packages is based on theory developed in Paper [15].
AbVarFq_LMFDBLabels - Magma - GitHub
- Magma code implementing the labelling scheme for abelian varieties over a finite field in an isogeny class with commutative endomorphism algebra
- This packages is based on theory developed in Paper [16].
R_ell_isogeny_graphs - Magma - GitHub
- Magma code to compute and SageMath code to vizualize (R,ll)-isogeny graphs
- This code was written jointly with Sarah Arpin.
- This packages is based on theory developed in Paper [18].
EllipticCurves - Macaulay2 - GitHub
- It provides basic functionalities for computations with elliptic curves.
- Written in collaboration with Alessandro Oneto.
- The development is concluded.

Slides/Videos

Cohen-Macaulay type of endomorphism rings of abelian varieties over finite fields - Slides, - AGC²T 2023, CIRM, Luminy, France. - June 6, 2023.
Polarizations of abelian varieties over finite fields via canonical liftings - Slides, - Video - Utrecht Geometry Centrum, Utrecht University, Netherlands. - Mar 29, 2022.
Computing Isomorphism Classes of Abelian Varieties over Finite Fields - Slides, - Video - VaNTAGe 11th series "Curves and abelian varieties over finite fields" (online). - Feb 1, 2022.
Computing Isomorphism Classes of Abelian Varieties over Finite Fields - Slides - Semi-Plenary Talk: Curves over finite fields - past, present and future (online) - May 24, 2021.
Products and Polarizations of Super-Isolated Abelian Varieties - Slides - (Q)NTAG (online), Simon Fraser University, Burnaby, Canada - December 03, 2020.
Abelian varieties over finite fields isogenous to a power - Slides - Institut de recherche mathématique de Rennes IRMAR, , Rennes, France. - November 16, 2018.