A Wiles-Diamond numerical criterion in higher dimensions

A Wiles-Diamond numerical criterion in higher dimensions

 Chandrashekhar Khare, UCLA
IAS - Simonyi Hall Seminar Room SH-101

In-Person and Online Talk

Zoom Link: https://theias.zoom.us/j/88393312988?pwd=emtLbTJ5ZnMvS3hBVmNmYjhIUEFIdz09

Wiles’s proof of  the modularity of (semistable) elliptic curves over the rationals and Fermat’s Last Theorem relied on his invention of  a modularity lifting method.

There were two strands to the method:

(i) A numerical criterion to for a map of rings to be an   isomorphism between complete intersections that are finite flat over Z_p  in Wiles’s paper on FLT, subsequently  generalized by Fred Diamond.

(ii) Patching (in his paper with Taylor)

The patching method  has been vastly generalized; in particular Calegari-Geraghty  found a way to generalize it in principle to prove (potential) modularity of elliptic curves over imaginary quadratic fields (a situation of ``positive defect’’).  Their method has been made unconditional to prove  modularity lifting results  over CM fields in the ten author paper. The numerical criterion has yet to be be generalized to positive defect.

In joint work with Srikanth Iyengar and Jeff Manning we give  a development of the Wiles-Diamond numerical criterion to situations of positive defect (for example to proving modularity results for torsion Galois representations  over imaginary quadratic fields). This in principle allows one to prove integral R=T theorems (in minimal and non-minimal situations),  for which just the use of patching seems inadequate. One interest of proving such integral versions of modularity lifting is that in these situations, the  Betti cohomology groups  of  3-dimensional Bianchi manifolds  (the analog of the modular curves over imaginary quadratic fields)  have a lot of torsion. Our strategy consists of  proving a higher dimensional version of the numerical criterion of Wiles-Diamond and applying it  to prove integral R=T theorems (in the non-minimal case) after patching.