algebraic curve

An algebraic curve is an algebraic variety of dimension $1$. Typically one restricts considerations to either affine or projective algebraic curves. Most often one treats the plane algebraic curves, i.e. curves with an embedding into $\mathbf{A}^2$ or $\mathbf{P}^2$; they are the locus of solutions of a single algebraic equation.

An *algebraic curve* over a field $F$ is the locus of solutions of $(n-1)$-polynomials in $n$-variables of type $F$, provided the Krull dimension of the ring is $1$.

- Every projective algebraic curve is birationally equivalent to a plane algebraic curve
- Mordell conjecture: every algebraic curve of genus $g\geq 2$ defined over rationals has at least one point over rationals
- To a nonsingular curve $C$ over the field of complex numbers one associates an abelian variety, namely its Jacobian variety together with the period map or Abel-Jacobi map $C\to J(C)$.

number fields (“function fields of curves over F1”) | function fields of curves over finite fields $\mathbb{F}_q$ (arithmetic curves) | Riemann surfaces/complex curves | |
---|---|---|---|

affine and projective line | |||

$\mathbb{Z}$ (integers) | $\mathbb{F}_q[t]$ (polynomials, function algebra on affine line $\mathbb{A}^1_{\mathbb{F}_q}$) | $\mathcal{O}_{\mathbb{C}}$ (holomorphic functions on complex plane) | |

$\mathbb{Q}$ (rational numbers) | $\mathbb{F}_q(t)$ (rational functions) | meromorphic functions on complex plane | |

$p$ (prime number/non-archimedean place) | $x \in \mathbb{F}_p$ | $x \in \mathbb{C}$ | |

$\infty$ (place at infinity) | $\infty$ | ||

$Spec(\mathbb{Z})$ (Spec(Z)) | $\mathbb{A}^1_{\mathbb{F}_q}$ (affine line) | complex plane | |

$Spec(\mathbb{Z}) \cup place_{\infty}$ | $\mathbb{P}_{\mathbb{F}_q}$ (projective line) | Riemann sphere | |

genus of the rational numbers = 0 | genus of the Riemann sphere = 0 | ||

formal neighbourhoods | |||

$\mathbb{Z}_p$ (p-adic integers) | $\mathbb{F}_q[ [ t -x ] ]$ (power series around $x$) | $\mathbb{C}[ [t-x] ]$ (holomorphic functions on formal disk around $x$) | |

$Spf(\mathbb{Z}_p)\underset{Spec(\mathbb{Z})}{\times} X$ (“$p$-arithmetic jet space” of $X$ at $p$) | formal disks in $X$ | ||

$\mathbb{Q}_p$ (p-adic numbers) | $\mathbb{F}_q((t-x))$ (Laurent series around $x$) | $\mathbb{C}((t-x))$ (holomorphic functions on punctured formal disk around $x$) | |

$\mathbb{A}_{\mathbb{Q}} = \underset{p\; place}{\prod^\prime}\mathbb{Q}_p$ (ring of adeles) | $\mathbb{A}_{\mathbb{F}_q((t))}$ ( adeles of function field ) | $\underset{x \in \mathbb{C}}{\prod^\prime} \mathbb{C}((t-x))$ (restricted product of holomorphic functions on all punctured formal disks, finitely of which do not extend to the unpunctured disks) | |

$\mathbb{I}_{\mathbb{Q}} = GL_1(\mathbb{A}_{\mathbb{Q}})$ (group of ideles) | $\mathbb{I}_{\mathbb{F}_q((t))}$ ( ideles of function field ) | $\underset{x \in \mathbb{C}}{\prod^\prime} GL_1(\mathbb{C}((t-x)))$ | |

zeta functions | |||

Riemann zeta function | Goss zeta function | ||

branched covering curves | |||

$K$ a number field ($\mathbb{Q} \hookrightarrow K$ a possibly ramified finite dimensional field extension) | $K$ a function field of an algebraic curve $\Sigma$ over $\mathbb{F}_p$ | $K_\Sigma$ (sheaf of rational functions on complex curve $\Sigma$) | |

$\mathcal{O}_K$ (ring of integers) | $\mathcal{O}_{\Sigma}$ (structure sheaf) | ||

$Spec_{an}(\mathcal{O}_K) \to Spec(\mathbb{Z})$ (spectrum with archimedean places) | $\Sigma$ (arithmetic curve) | $\Sigma \to \mathbb{C}P^1$ (complex curve being branched cover of Riemann sphere) | |

genus of a number field | genus of an algebraic curve | genus of a surface | |

formal neighbourhoods | |||

$v$ prime ideal in ring of integers $\mathcal{O}_K$ | $x \in \Sigma$ | $x \in \Sigma$ | |

$K_v$ (formal completion at $v$) | $\mathbb{C}((t_x))$ (function algebra on punctured formal disk around $x$) | ||

$\mathcal{O}_{K_v}$ (ring of integers of formal completion) | $\mathbb{C}[ [ t_x ] ]$ (function algebra on formal disk around $x$) | ||

$\mathbb{A}_K$ (ring of adeles) | $\prod^\prime_{x\in \Sigma} \mathbb{C}((t_x))$ (restricted product of function rings on all punctured formal disks around all points in $\Sigma$) | ||

$\mathcal{O}$ | $\prod_{x\in \Sigma} \mathbb{C}[ [t_x] ]$ (function ring on all formal disks around all points in $\Sigma$) | ||

$\mathbb{I}_K = GL_1(\mathbb{A}_K)$ (group of ideles) | $\prod^\prime_{x\in \Sigma} GL_1(\mathbb{C}((t_x)))$ | ||

Galois theory | |||

Galois group | “ | $\pi_1(\Sigma)$ fundamental group | |

Galois representation | “ | flat connection (“local system”) on $\Sigma$ | |

class field theory | |||

class field theory | “ | geometric class field theory | |

Hilbert reciprocity law | Artin reciprocity law | Weil reciprocity law | |

$GL_1(K)\backslash GL_1(\mathbb{A}_K)$ (idele class group) | “ | ||

$GL_1(K)\backslash GL_1(\mathbb{A}_K)/GL_1(\mathcal{O})$ | “ | $Bun_{GL_1}(\Sigma)$ (moduli stack of line bundles, by Weil uniformization theorem) | |

non-abelian class field theory and automorphy | |||

number field Langlands correspondence | function field Langlands correspondence | geometric Langlands correspondence | |

$GL_n(K) \backslash GL_n(\mathbb{A}_K)//GL_n(\mathcal{O})$ (constant sheaves on this stack form unramified automorphic representations) | “ | $Bun_{GL_n(\mathbb{C})}(\Sigma)$ (moduli stack of bundles on the curve $\Sigma$, by Weil uniformization theorem) | |

Tamagawa-Weil for number fields | Tamagawa-Weil for function fields | ||

zeta functions | |||

Dedekind zeta function | Weil zeta function | zeta function of a Riemann surface |

Related $n$Lab entries include moduli space of curves, stable curve?, Jacobian variety, Mordell conjecture, Riemann surface, elliptic curve, Bezout's theorem

- Wikipedia,
*Algebraic curve*

Revised on July 17, 2014 12:00:54
by Urs Schreiber
(82.136.246.44)