Book contents
- Frontmatter
- Contents
- Preface
- Notation
- Chapter 1 General theory of quadratic forms
- Chapter 2 Positive definite quadratic forms over ℝ
- Chapter 3 Quadratic forms over local fields
- Chapter 4 Quadratic forms over ℚ
- Chapter 5 Quadratic forms over the p-adic integer ring
- Chapter 6 Quadratic forms over ℤ
- Chapter 7 Some functorial properties of positive definite quadratic forms
- Notes
- References
- Index
Chapter 6 - Quadratic forms over ℤ
Published online by Cambridge University Press: 20 March 2010
- Frontmatter
- Contents
- Preface
- Notation
- Chapter 1 General theory of quadratic forms
- Chapter 2 Positive definite quadratic forms over ℝ
- Chapter 3 Quadratic forms over local fields
- Chapter 4 Quadratic forms over ℚ
- Chapter 5 Quadratic forms over the p-adic integer ring
- Chapter 6 Quadratic forms over ℤ
- Chapter 7 Some functorial properties of positive definite quadratic forms
- Notes
- References
- Index
Summary
In this chapter and the next, we study quadratic forms over ℤ, which is the main goal of this book. All previous chapters converge here. There are still many facts which we do not cover in this chapter. The next has another character.
Fundamentals
Here we give some basic notations and facts. First of all we give a correspondence between local and global lattices.
Let a field F and a ring R be either ℚ and ℤ or ℚp and ℤp. A module L over R in a finite-dimensional vector space V over F is called a lattice on V if L is finitely generated and contains a basis of V. Then L has a basis over R and rank L = dim V.
Let V be a regular quadratic space over. A lattice on it is called a regular (quadratic) lattice.
If V∞ is positive definite, i.e. Q(x) > 0 for every non-zero x ∈ V∞, then V is called positive definite and a lattice on it is called a positive (definite quadratic) lattice. If V∞ is negative definite, i.e. Q(x) < 0 for every nonzero x ∈ V∞, then V is called negative definite and a lattice on it is called a negative (definite quadratic) lattice.
If V∞ is isotropic, then V is called indefinite and a lattice on it is called an indefinite (quadratic) lattice. We note that if V is indefinite and dim V ≥ 5, then V is isotropic by Theorem 4.4.1 and 3.5.1.
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- Information
- Arithmetic of Quadratic Forms , pp. 129 - 188Publisher: Cambridge University PressPrint publication year: 1993