Archimedean Components Research Articles

On Petersson norms of generic cusp forms and special values of adjoint L -functions for GSp4

We prove an explicit formula for the Petersson norms of some normalized generic cuspidal newforms on ${\rm GSp}_4$ whose archimedean components belong to either discrete series representations or spherical principal series representations. Our formula expresses the Petersson norms in terms of special values of adjoint $L$-functions and some elementary constants depending only on local representations.

On the images of Galois representations attached to low weight Siegel modular forms

Let $\pi$ be a cuspidal automorphic representation of $\mathrm{GSp}_4(\mathbf{A_Q})$, whose archimedean component is a holomorphic discrete series or limit of discrete series representation. If $\pi$ is not CAP or endoscopic, then we show that its associated $\ell$-adic Galois representations are irreducible and crystalline for $100\%$ of primes $\ell$. If, moreover, $\pi$ is neither an automorphic induction nor a symmetric cube lift, then we show that, for $100\%$ of primes $\ell$, the image of its mod $\ell$ Galois representation contains $\mathrm{Sp}_4(\mathbf{F}_{\ell})$.

Sato–Tate equidistribution for families of automorphic representations through the stable trace formula

In arXiv:1208.1945, Shin and Templier proved certain equidistribution bounds on local components of certain families of automorphic representations. We extend their weight-aspect results to families of automorphic representations where the Archimedean component is restricted to a single discrete-series representation instead of an entire $L$-packet. We do this by using a so-called "hyperendoscopy" version of the stable trace formula developed by Ferrari. The main technical difficulties are defining a version of hyperendoscopy that works for groups without simply connected derived subgroup and bounding the values of transfers of unramified functions. We also present an extension of Arthur's simple trace formula for test functions with Euler-Poincar\'e component at infinity to non-cuspidal groups since it does not seem to appear elsewhere in the literature.

Big principal series, -adic families and -invariants

In earlier work, the first named author generalized the construction of Darmon-style$\mathcal {L}$-invariants to cuspidal automorphic representations of semisimple groups of higher rank, which are cohomological with respect to the trivial coefficient system and Steinberg at a fixed prime. In this paper, assuming that the Archimedean component of the group has discrete series we show that these automorphic$\mathcal {L}$-invariants can be computed in terms of derivatives of Hecke eigenvalues in$p$-adic families. Our proof is novel even in the case of modular forms, which was established by Bertolini, Darmon and Iovita. The main new technical ingredient is the Koszul resolution of locally analytic principal series representations by Kohlhaase and Schraen. As an application of our results we settle a conjecture of Spieß: we show that automorphic$\mathcal {L}$-invariants of Hilbert modular forms of parallel weight$2$are independent of the sign character used to define them. Moreover, we show that they are invariant under Jacquet–Langlands transfer and, in fact, equal to the Fontaine–Mazur$\mathcal {L}$-invariant of the associated Galois representation. Under mild assumptions, we also prove the equality of automorphic and Fontaine–Mazur$\mathcal {L}$-invariants for representations of definite unitary groups of arbitrary rank. Finally, we study the case of Bianchi modular forms to show how our methods, given precise results on eigenvarieties, can also work in the absence of discrete series representations.

Semigroups whose right ideals are finitely generated

AbstractWe call a semigroup$S$weakly right noetherianif every right ideal of$S$is finitely generated; equivalently,$S$satisfies the ascending chain condition on right ideals. We provide an equivalent formulation of the property of being weakly right noetherian in terms of principal right ideals, and we also characterize weakly right noetherian monoids in terms of their acts. We investigate the behaviour of the property of being weakly right noetherian under quotients, subsemigroups and various semigroup-theoretic constructions. In particular, we find necessary and sufficient conditions for the direct product of two semigroups to be weakly right noetherian. We characterize weakly right noetherian regular semigroups in terms of their idempotents. We also find necessary and sufficient conditions for a strong semilattice of completely simple semigroups to be weakly right noetherian. Finally, we prove that a commutative semigroup$S$with finitely many archimedean components is weakly (right) noetherian if and only if$S/\mathcal {H}$is finitely generated.

(2102-6487) Ordinal sum constructions for aggregation functions on the real unit interval

We discuss ordinal sums as one of powerful tools in the aggregation theory serving, depending on the context, both as a construction method and as a representation, respectively. Up to recalling of several classical results dealing with ordinal sums, in particular dealing, e.g., with continuous t-norms, copulas, or recent results, e.g., concerning uninorms with continuous underlying functions, we present also several new results, such as the uniqueness of the link between t-norms or t-conorms, and related Archimedean components, problems dealing with the cardinality of the considered index sets in ordinal sums, or infinite ordinal sums of aggregation functions covering by one type of ordinal sums both t-norms and t-conorms ordinal sums.

Lafforgue pseudocharacters and parities of limits of Galois representations

Let $F$ be a CM field with totally real subfield $F^+$ and let $\pi$ be a $C$-algebraic cuspidal automorphic automorphic representation of $\mathrm{U}(a,b)(\mathbf{A}_{F^+})$ whose archimedean components lie in the (non-degenerate limit of) discrete series. We attach to $\pi$ a Galois representation $R_\pi:\mathrm{Gal}(\overline F/ F^+)\to{}^C\mathrm{U}(a,b)(\overline{\mathbf Q}_\ell)$ such that, for any complex conjugation element $c$, $R_\pi(c)$ is as predicted by the Buzzard--Gee conjecture. As a corollary, we deduce that the Galois representations attached to certain irregular, $C$-algebraic (essentially) conjugate self-dual cuspidal automorphic representations of $\mathrm{GL}_n(\mathbf A_F)$ are odd in the sense of Bella\"iche--Chenevier.

On counting cuspidal automorphic representations for GSp(4)

Abstract We find the number s k ⁢ ( p , Ω ) s_{k}(p,\Omega) of cuspidal automorphic representations of GSp ⁢ ( 4 , A Q ) \mathrm{GSp}(4,\mathbb{A}_{\mathbb{Q}}) with trivial central character such that the archimedean component is a holomorphic discrete series representation of weight k ≥ 3 k\geq 3 , and the non-archimedean component at 𝑝 is an Iwahori-spherical representation of type Ω and unramified otherwise. Using the automorphic Plancherel density theorem, we show how a limit version of our formula for s k ⁢ ( p , Ω ) s_{k}(p,\Omega) generalizes to the vector-valued case and a finite number of ramified places.

An explicit construction of non-tempered cusp forms on $$O(1,8n+1)$$

We explicitly construct non-holomorphic cusp forms on the orthogonal group of signature $$(1,8n+1)$$ for an arbitrary natural number n as liftings from Maass cusp forms of level one. In our previous works [31] and [24] the fundamental tool to show the automorphy of the lifting was the converse theorem by Maass. In this paper, we use the Fourier expansion of the theta lifts by Borcherds [4] instead. We also study cuspidal representations generated by such cusp forms and show that they are irreducible and that all of their non-archimedean local components are non-tempered while the archimedean component is tempered, if the Maass cusp forms are Hecke eigenforms. Our non-archimedean local theory relates Sugano’s local theory [39] to non-tempered automorphic forms or representations of a general orthogonal group in a transparent manner.

Strata Hasse invariants, Hecke algebras and Galois representations

We construct group-theoretical generalizations of the Hasse invariant on strata closures of the stacks mathop {Ghbox {-}{} mathtt{Zip}}nolimits ^{mu }. Restricting to zip data of Hodge type, we obtain a group-theoretical Hasse invariant on every Ekedahl–Oort stratum closure of a general Hodge-type Shimura variety. A key tool is the construction of a stack of zip flags mathop {Ghbox {-}{} mathtt{ZipFlag}}nolimits ^mu , fibered in flag varieties over mathop {Ghbox {-}{} mathtt{Zip}}nolimits ^{mu }. It provides a simultaneous generalization of the “classical case” homogeneous complex manifolds studied by Griffiths–Schmid and the “flag space” for Siegel varieties studied by Ekedahl–van der Geer. Four applications are obtained: (1) Pseudo-representations are attached to the coherent cohomology of Hodge-type Shimura varieties modulo a prime power. (2) Galois representations are associated to many automorphic representations with non-degenerate limit of discrete series Archimedean component. (3) It is shown that all Ekedahl–Oort strata in the minimal compactification of a Hodge-type Shimura variety are affine, thereby proving a conjecture of Oort. (4) Part of Serre’s letter to Tate on mod p modular forms is generalized to general Hodge-type Shimura varieties.

Archimedean zeta integrals on U(n,1)

For a dual pair of unitary groups with equal size, zeta integrals arising from Rallis inner product formula give the central values of certain automorphic L-functions. In this paper we explicitly calculate archimedean zeta integrals of this type for U(n,1), assuming that the corresponding archimedean component of the automorphic representation is a holomorphic discrete series.

Weakly separative weakly commutative semigroups

A semigroup S is called a weakly commutative semigroup if, for every a,b∈S, there is a positive integer n such that (ab) n ∈Sa∩bS. A semigroup S is called archimedean if, for every a,b∈S, there are positive integers m and n such that a n ∈SbS and b m ∈SaS. It is known that every weakly commutative semigroup is a semilattice of weakly commutative archimedean semigroups. A semigroup S is called a weakly separative semigroup if, for every a,b∈S, the assumption a 2=ab=b 2 implies a=b. In this paper we show that a weakly commutative semigroup is weakly separative if and only if its archimedean components are weakly cancellative. This result is a generalization of Theorem 4.16 of Clifford and Preston (The Algebraic Theory of Semigroups, Am. Math. Soc., Providence, 1961).

Hierarchical Kendall copulas: Properties and inference

AbstractWhile there is substantial need for dependence models in higher dimensions, most existing models quickly become rather restrictive and barely balance parsimony and flexibility. Hierarchical constructions may improve on that by grouping variables in different levels. In this paper, the new class of hierarchical Kendall copulas is proposed and discussed. Hierarchical Kendall copulas are built up by flexible copulas specified for groups of variables, where aggregation is facilitated by the Kendall distribution function, the multivariate analog to the probability integral transform for univariate random variables. After deriving properties of the general model formulation, particular focus is given to inference techniques of hierarchical Kendall copulas with Archimedean components, for which closed‐form analytical expressions can be derived. A substantive application to German stock returns finally shows that hierarchical Kendall copulas perform very well for real data, out‐of‐ as well as in‐sample. The Canadian Journal of Statistics 42: 78–108; 2014 © 2014 Statistical Society of Canada

Galois representations associated to holomorphic limits of discrete series

AbstractGeneralizing previous results of Deligne–Serre and Taylor, Galois representations are attached to cuspidal automorphic representations of unitary groups whose Archimedean component is a holomorphic limit of discrete series. The main ingredient is a construction of congruences, using the Hasse invariant, that is independent of$q$-expansions.

Galois representations associated with unitary groups over ℚ

We show that a cuspidal automorphic representation π= ⊗l≤∞πl of a unitary similitude group GU(a,b)∕ℚ with archimedean component π∞ in a regular discrete series has an associated (a+b)-dimensional p-adic Galois representation with Frobenius eigenvalues given by the local base change parameters for all primes l such that πl and GU(a,b) are unramified.

On the cuspidal cohomology of arithmetic groups

It is the main objective of this paper to show a vanishing result for cuspidal cohomology of arithmetic groups in classical groups~$G$ defined over some number field~$k$. Our approach relies on the fact that cuspidal automorphic forms are nonsingular in the sense of Howe. This result puts a strong constraint on the (archimedean components of) irreducible cuspidal automorphic representations of $G$ that can possibly contribute to the cuspidal cohomology. Combining this with the classification of Vogan-Zuckerman of unitary representations with nonzero cohomology provides a constant $r_0(G/k)$, only depending on $G/k$, below which the cuspidal cohomology vanishes. We will give a formula for this constant for each classical group of type (I) in the classification scheme due to Weil. We conclude with making this result explicit for some split classical groups over a totally real algebraic number field.

R-bands of r-archimedean ordered semigroups

Some semigroups (without order) are decomposable into r-archimedean semigroups. In the present paper we deal with the problem of decomposing certain ordered semigroups into r (l)-archimedean components. The semilattice congruences play an important role in the decomposition of semigroups -without order. When we pass from semigroups without order to ordered semigroups, the same role is played by the complete semilattice congruences. The characterization of complete semilattices of semigroups of a given type has been considered by the same authors. Band congruences play an important role in studying the decomposition of some ordered semigroups, like the decomposition of t-archimedean ordered semigroups. The r (l)-band congruences have been also proved to be useful in studying the decomposition of some types of ordered semigroups, especially the decomposition of r (l)-archimedean ordered semigroups. In this paper we first prove that an ordered semigroup S is an r (resp. l)-band of semigroups of a given type \( \mathcal{T} \) if and only if it is decomposable into pairwise disjoint subsemigroups Sα of S of type \( \mathcal{T} \) indexed by a band B such that SαSβ ⊆ Sαβ for all α, β ∈ B and Sα ∩ (Sβ] ≡ O implies α = βα (resp. α = αβ). Thenwe characterize the r (resp. l)-bands of r (resp. l)-archimedean semigroups.

The rank of a commutative semigroup

The concept of rank of a commutative cancellative semigroup is extended to all commutative semigroups $S$ by defining $\mathop{\rm rank}S$ as the supremum of cardinalities of finite independent subsets of $S$. Representing such a semigroup $S$ as a semilattice $Y$ of (archimedean) components $S_\alpha $, we prove that $\mathop{\rm rank}S$ is the supremum of ranks of various $S_\alpha $. Representing a commutative separative semigroup $S$ as a semilattice of its (cancellative) archimedean components, the main result of the paper provides several characterizations of $\mathop{\rm rank}S$; in particular if $\mathop{\rm rank}S$ is finite. Subdirect products of a semilattice and a commutative cancellative semigroup are treated briefly. We give a classification of all commutative separative semigroups which admit a generating set of one or two elements, and compute their ranks.

Cancellativity properties for t-norms and t-subnorms

On the one hand, cancellativity properties are mainly used to express to which extend the partial functions of a t-subnorm T are injective. On the other hand, the zooms of T corresponding to its non-trivial Archimedean components are t-subnorms that largely determine T. Fixing one out of four basic types of cancellativity (cancellativity, conditional cancellativity, weak cancellativity and weak conditional cancellativity) we figure out which less restrictive type of cancellativity expresses that all maximal Archimedean zooms of T satisfy the given cancellativity property. We lay bare the mutual relationships between all these types of cancellativity and solve an open problem posed by Klement et al.

Semilattices of Archimedean Ordered Semigroups

In this paper we deal with the decomposition of some classes of ordered semigroups into archimedean components. In particular, we prove that in ordered semigroups the concepts of semilattices of archimedean semigroups and of complete semilattices of archimedean semigroups are the same. In addition, we discuss similarities and differences between semigroups (without order) and ordered semigroups.