---
tag: KHK4WC0KG4
kind: statement
role: proposition
name: Weil's conjecture on Tamagawa numbers
aliases: [tamagawa-measure, the-weil-conjecture-on-tamagawa-numbers, weil-conjecture-about-tamagawa-numbers, weil-conjecture-for-tamagawa-numbers, weil-conjecture-on-tamagawa-numbers]
sources:
  - wikipedia: en:3036289@r1297000369
    locator: Weil's conjecture on Tamagawa numbers
    note: adopted
    mention: wikipedia://en/3036289
    sections: [Statement]
same_as:
  wikidata: Q7980185
  wikipedia: Weil's conjecture on Tamagawa numbers
inventory: [PW4223WE8F]
---

## Statement

In mathematics, the **Weil conjecture on Tamagawa numbers** is the statement that the Tamagawa number $\tau(G)$ of a simply connected simple algebraic group defined over a number field is 1. In this case, *simply connected* means "not having a proper *algebraic* covering" in the algebraic group theory sense, which is not always [[the topologists' meaning|0QW64ARSHB]].