A Modular Interpretation of BBGS Towers

Abstract

In 2000, based on his procedure for constructing explicit towers of modular curves, Elkies deduced explicit equations of rank-2 Drinfeld modular curves which coincide with the asymptotically optimal towers of curves constructed by Garcia and Stichtenoth. In 2015, Bassa, Beelen, Garcia, and Stichtenoth constructed a celebrated (recursive and good) tower (BBGS-tower for short) of curves and outlined a modular interpretation of the defining equations. Soon after that, Gekeler studied in depth the modular curves coming from sparse Drinfeld modules. In this paper, to establish a link between these existing results, we propose and prove a generalized Elkies' Theorem which tells in detail how to directly describe a modular interpretation of the equations of rank-m Drinfeld modular curves with m>=2.

arXiv commentrevised the paper with the intention of presenting a correct and clear version

References in corpus (6)

• Explicit modular towers
• A rapid introduction to Drinfeld modules, $t$-modules, and $t$-motives
• Torsion Limits and Riemann-Roch Systems for Function Fields and Applications
• New maximal curves as ray class fields over Deligne-Lusztig curves
• A modular interpretation of various cubic towers
• An Explicit Shimura Tower of Function Fields over a Number Field: An Application of Takeuchi's List