Ordinary Hecke Algebra Research Articles

Derived Hecke action at p and the ordinary p -adic cohomology of arithmetic manifolds

Abstract: We study the derived Hecke action at $p$ on the ordinary $p$-adic cohomology of arithmetic subgroups of reductive groups ${\rm G}(\Bbb{Q})$. This is the analog at $\ell=p$ of derived Hecke actions studied by Venkatesh in the tame case, and is the derived analog of Hida's theory for ordinary Hecke algebras. We show that properties of the derived Hecke action at $p$ are related to deep conjectures in Galois cohomology which are higher analogs of the classical Leopoldt conjecture.

Generalisations of Hecke algebras from loop braid groups

We introduce a generalisation $LH_n$ of the ordinary Hecke algebras informed by the loop braid group $LB_n$ and the extension of the Burau representation thereto. The ordinary Hecke algebra has many remarkable arithmetic and representation theoretic properties, and many applications. We show that $LH_n$ has analogues of several of these properties. In particular we %introduce consider a class of local (tensor space/functor) representations of the braid group derived from a meld of the (non-functor) Burau representation and the (functor) Deguchi {\em et al}-Kauffman--Saleur-Rittenberg representations here called Burau-Rittenberg representations. In its most supersymmetric case somewhat mystical cancellations of anomalies occur so that the Burau-Rittenberg representation extends to a loop Burau-Rittenberg representation. And this factors through $LH_n$. Let $SP_n$ denote the corresponding quotient algebra, $k$ the ground ring, and $t \in k$ the loop-Hecke parameter. We prove the following: 1) $LH_n$ is finite dimensional over a field. 2) The natural inclusion $LB_n \rightarrow LB_{n+1}$ passes to an inclusion $SP_n \rightarrow SP_{n+1}$. 3) Over $k=\mathbb{C}$, $SP_n / rad $ is generically the sum of simple matrix algebras of dimension (and Bratteli diagram) given by Pascal's triangle. 4) We determine the other fundamental invariants of $SP_n$ representation theory: the Cartan decomposition matrix; and the quiver, which is of type-A. 5) The structure of $SP_n $ is independent of the parameter $t$, except for $t= 1$. \item For $t^2 \neq 1$ then $LH_n \cong SP_n$ at least up to rank$n=7$ (for $t=-1$ they are not isomorphic for $n>2$; for $t=1$ they are not isomorphic for $n>1$). Finally we discuss a number of other intriguing points arising from this construction in topology, representation theory and combinatorics.

Ramification of the Eigencurve at Classical RM Points

AbstractJ. Bellaïche and M. Dimitrov showed that the$p$-adic eigencurve is smooth but not étale over the weight space at$p$-regular theta series attached to a character of a real quadratic field$F$in which$p$splits. In this paper we prove the existence of an isomorphism between the subring fixed by the Atkin–Lehner involution of the completed local ring of the eigencurve at these points and a universal ring representing a pseudo-deformation problem. Additionally, we give a precise criterion for which the ramification index is exactly 2. We finish this paper by proving the smoothness of the nearly ordinary and ordinary Hecke algebras for Hilbert modular forms over$F$at the overconvergent cuspidal Eisenstein points, being the base change lift for$\text{GL}(2)_{/F}$of these theta series. Our approach uses deformations and pseudo-deformations of reducible Galois representations.

Hida duality and the Iwasawa main conjecture

The central result of this paper is a refinement of Hida’s duality theorem between ordinary $${\varLambda }$$ -adic modular forms and the universal ordinary Hecke algebra. In particular, we give a sufficient condition for this duality to be integral with respect to particular submodules of the space of ordinary $${\varLambda }$$ -adic modular forms. This refinement allows us to give a simple proof that the universal ordinary cuspidal Hecke algebra modulo Eisenstein ideal is isomorphic to the Iwasawa algebra modulo an ideal related to the Kubota-Leopoldt p-adic L-function. The motivation behind these results stems from a proof of the Iwasawa main conjecture over $${\mathbb {Q}}$$ by Ohta. While simple and elegant, Ohta’s proof requires some restrictive hypotheses which we are able to remove using our results.

On the image of the Galois representation associated to a non-CM Hida family

Fix a prime $p > 2$. Let $\rho : \text{Gal}(\overline{\mathbb{Q}}/\mathbb{Q}) \to \text{GL}_2(\mathbb{I})$ be the Galois representation coming from a non-CM irreducible component $\mathbb{I}$ of Hida's $p$-ordinary Hecke algebra. Assume the residual representation $\bar{\rho}$ is absolutely irreducible. Under a minor technical condition we identify a subring $\mathbb{I}_0$ of $\mathbb{I}$ containing $\mathbb{Z}_p[[T]]$ such that the image of $\rho$ is large with respect to $\mathbb{I}_0$. That is, $\text{Im} \rho$ contains $\text{ker}(\text{SL}_2(\mathbb{I}_0) \to \text{SL}_2(\mathbb{I}_0/\mathfrak{a}))$ for some non-zero $\mathbb{I}_0$-ideal $\mathfrak{a}$. This paper builds on recent work of Hida who showed that the image of such a Galois representation is large with respect to $\mathbb{Z}_p[[T]]$. Our result is an $\mathbb{I}$-adic analogue of the description of the image of the Galois representation attached to a non-CM classical modular form obtained by Ribet and Momose in the 1980s.

Big Galois representations and -adic -functions

Let$p\geqslant 5$be a prime. If an irreducible component of the spectrum of the ‘big’ ordinary Hecke algebra does not have complex multiplication, under mild assumptions, we prove that the image of its Galois representation contains, up to finite error, a principal congruence subgroup${\rm\Gamma}(L)$of$\text{SL}_{2}(\mathbb{Z}_{p}[[T]])$for a principal ideal$(L)\neq 0$of$\mathbb{Z}_{p}[[T]]$for the canonical ‘weight’ variable$t=1+T$. If$L\notin {\rm\Lambda}^{\times }$, the power series$L$is proven to be a factor of the Kubota–Leopoldt$p$-adic$L$-function or of the square of the anticyclotomic Katz$p$-adic$L$-function or a power of$(t^{p^{m}}-1)$.

On Artin representations and nearly ordinary Hecke algebras over totally real fields

We prove many new cases of the strong Artin conjecture for two-dimensional, totally odd, insoluble (icosahedral) representations \mathrm{Gal}(\overline{F}/F)\rightarrow GL_2(\mathbf{C}) of the absolute Galois group of a totally real field F .

Image of Λ-adic Galois representations modulo p

Let p≥5 be a prime. If an irreducible component of the spectrum of the ‘big’ ordinary Hecke algebra does not have complex multiplication, under mild assumptions, we prove that the image of its mod p Galois representation contains an open subgroup of for the canonical “weight” variable T. This fact appears to be deep, as it is almost equivalent to the vanishing of the μ-invariant of the Kubota–Leopoldt p-adic L-function and the anticyclotomic Katz p-adic L-function. Another key ingredient of the proof is the anticyclotomic main conjecture proven by Rubin/Mazur–Tilouine.

Nearly ordinary rank four Galois representations and $p$-adic Siegel modular forms

This paper is devoted to the proof of two results. The first was conjectured in 1994 by the author. It concerns the identity, under certain assumptions, of the universal deformation ring of p-nearly ordinary Galois representations and a local component of the universal nearly ordinary Hecke algebra in the sense of Hida. The other, which relies on the first, concerns the modularity of certain abelian surfaces. More precisely, one can associate to certain irreducible abelian surfaces defined over the rationals overconvergent p-adic cusp eigenforms. The question of whether these forms are classical is not studied in this paper.

On quantum group symmetry and Bethe ansatz for the asymmetric twin spin chain withintegrable boundary

Motivated by a study of the crossing symmetry of the asymmetric twin or ‘gemini’representation of the affine Hecke algebra we give a construction for crossing tensor spacerepresentations of ordinary Hecke algebras. These representations build solutions to theYang–Baxter equation satisfying the crossing condition (that is, integrable quantum spinchains). We show that every crossing representation of the Temperley–Lieb algebra appearsin this construction, and in particular that this construction builds new representations. Weextend these to new representations of the blob algebra, which build new solutions to theboundary Yang–Baxter equation (i.e. open spin chains with integrable boundaryconditions).We prove that the open spin chain Hamiltonian derived from Sklyanin’s commutingtransfer matrix using such a solution can always be expressed as the representation of anelement of the blob algebra, and determine this element. We determine the representationtheory (irreducible content) of the new representations and hence show that all suchHamiltonians have the same spectrum up to multiplicity, for any given value of thealgebraic boundary parameter. (A corollary is that our models have the samespectrum as the open XXZ chain with nondiagonal boundary—despite differingfrom this model in having reference states.) Using these multiplicity data, andother ideas, we investigate the underlying quantum group symmetry of the newHamiltonians. We derive the form of the spectrum and the Bethe ansatz equations.

CONTROL THEOREMS OF COHERENT SHEAVES ON SHIMURA VARIETIES OF PEL TYPE

An exact control theorem is proven for nearly ordinary -adic automorphic forms on symplectic and unitary groups over totally real fields if the algebraic group is split at . In particular, a given nearly ordinary holomorphic Hecke eigenform can be lifted to a family of holomorphic Hecke eigenforms indexed by weights of the standard maximal split torus of the group. Their -points of the split torus. The method is applicable to any reductive algebraic groups yielding Shimura varieties of PEL type under mild assumptions on the existence of integral toroidal compactification of the variety. Even in the Hilbert modular case, the result contains something new: freeness of the universal nearly ordinary Hecke algebra over the Iwasawa algebra, which eluded my scrutiny when I studied general theory of the -adic Hecke algebra in the 1980s.AMS 2000 Mathematics subject classification: Primary 11F03; 11F30; 11F33; 11F41; 11F60; 11G15; 11G18

The eisenstein ideal in Hida's ordinary Hecke algebra

The eisenstein ideal in Hida's ordinary Hecke algebra

On the ordinary Hecke algebra

We show that, under relatively simple assumptions which “almost always” hold, the structure of Hida's ordinary Hecke algebra can be explicitly determined. The assumptions are such that they can easily be checked in specific cases, and we do so for a range of examples involving small primes and forms of level one and low weight.