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AutomorphicLFunction

Stephen Crowley edited this page Jun 8, 2023 · 7 revisions

An automorphic L-function is a complex-valued function that plays a central role in the theory of automorphic forms and number theory. Automorphic forms are a generalization of classical objects like modular forms and are functions on certain topological spaces that satisfy specific transformation properties under the action of a discrete group.

Automorphic L-functions are constructed from automorphic forms or representations and are a generalization of other famous L-functions like the Riemann zeta function or Dirichlet L-functions, which are essential in understanding the distribution of prime numbers.

These L-functions have deep connections with various areas of mathematics, such as algebraic geometry, representation theory, and arithmetic geometry. They have numerous applications, including to the study of Diophantine equations, the distribution of prime numbers, and the behavior of arithmetic objects.

One of the key conjectures surrounding automorphic L-functions is the Langlands Program, which seeks to establish a far-reaching correspondence between automorphic forms and Galois representations. This conjectural framework aims to unify many aspects of number theory and has profound implications for our understanding of the structure and properties of these L-functions.

In summary, automorphic L-functions are complex-valued functions arising from automorphic forms or representations with deep connections to number theory and other areas of mathematics. They play a crucial role in understanding various arithmetic phenomena and are central to ongoing research in the field.

More precisely

A more technical summary of automorphic L-functions involves introducing some of the key concepts and definitions from the theory of automorphic forms and their associated L-functions. Here, we'll mention a few of these concepts along with relevant formulas, but keep in mind that this is only a brief introduction to a rich and deep area of mathematics.

  1. Automorphic forms: An automorphic form is a complex-valued function on a quotient space $G(\mathbb{Q})\backslash G(\mathbb{A})/K$, where $G$ is a reductive algebraic group defined over the rational numbers $\mathbb{Q}$, $G(\mathbb{A})$ is the group of its adelic points, and $K$ is an open compact subgroup of $G(\mathbb{A})$. The function satisfies certain transformation properties under the action of a discrete subgroup $\Gamma \subseteq G(\mathbb{Q})$ and has additional analytic properties.

  2. Automorphic representations: Automorphic forms give rise to automorphic representations, which are certain representations of $G(\mathbb{A})$ on a Hilbert space of functions. These representations are constructed from automorphic forms by considering their Fourier expansions and analyzing the action of the group $G(\mathbb{A})$.

  3. Hecke operators: Hecke operators are certain linear operators acting on the space of automorphic forms or automorphic representations. For a prime $p$ and an integer $n$, the $n$-th Hecke operator $T_p(n)$ acts on an automorphic form $f$ as follows:

    $$T_p(n)f = \sum_{d | (p,n)} d^{k-1} f | M_p(d, n/d)$$

    Here, $k$ is the weight of the automorphic form $f$, $M_p(d, n/d)$ is a matrix corresponding to the action of the Hecke operator, and $f | M_p(d, n/d)$ denotes the action of the matrix on the function $f$.

  4. Automorphic L-functions: Given an automorphic representation $\pi$ of $G(\mathbb{A})$, we can associate an automorphic L-function $L(s,\pi)$ to it. These L-functions are usually defined as a product over all prime numbers $p$:

    $$L(s,\pi) = \prod_p L_p(s,\pi_p)^{-1}$$

    Here, $L_p(s,\pi_p)$ are the local L-factors at each prime $p$, which are determined by the action of the Hecke operators on the automorphic representation $\pi$.

  5. Analytic properties: Automorphic L-functions are expected to satisfy certain analytic properties, such as having a meromorphic continuation to the entire complex plane, satisfying a functional equation relating $L(s,\pi)$ and $L(1-s,\pi')$, where $\pi'$ is the contragredient representation, and having specific growth properties for their coefficients.

These are just a few key concepts and formulas involved in the study of automorphic L-functions. The full theory is much more intricate and requires a deep understanding of algebraic and analytic number theory, as well as various aspects of algebraic geometry, representation theory, and harmonic analysis.

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