Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options answers only not deleted user 48142

Algebraic and geometric theory of quadratic forms and symmetric bilinear forms, e.g., values attained by quadratic forms, isotropic subspaces, the Witt ring, invariants of quadratic forms, the discriminant and Clifford algebra of a quadratic form, Pfister forms, automorphisms of quadratic forms.

6 votes

Equivalence of quadratic forms over $p$-adic integers vs over localisation at $p$

Since $\mathbb{Z}_{(p)}$ can be thought of as a subring of $\mathbb{Z}_{p}$, if two quadratic forms $Q_{1}$ and $Q_{2}$ are equivalent over $\mathbb{Z}_{(p)}$, then they must be equivalence over $\mat …
Jeremy Rouse's user avatar
  • 20.4k
8 votes
Accepted

Calculating the explicit constant – Siegel zeros and class numbers

One place to find this worked out in detail is the paper "On the Siegel-Tatuzawa theorem" by Jeffrey Hoffstein (published in 1980 in Acta Arithmetica). Lemma 1 of that paper states that if $\chi$ is a …
Jeremy Rouse's user avatar
  • 20.4k
5 votes
Accepted

Can each natural number be represented by $2w^2+x^2+y^2+z^2+xyz$ with $x,y,z\in\mathbb N$?

The answer to question 1 is yes - the other questions seem to me to be more difficult. If $n$ is odd, then there are non-negative integers $w$, $x$ and $y$ so that $n = 2w^{2} + x^{2} + y^{2}$. One wa …
Jeremy Rouse's user avatar
  • 20.4k
7 votes

Proof of Witt's result about quaternion extensions

The problem you raise is tied to the "embedding problem." There is chapter devoted to this in Malle and Matzat's "Inverse Galois Theory" text (here's a link to the publisher's page about this book). …
Jeremy Rouse's user avatar
  • 20.4k
6 votes
Accepted

Ternary quadratic form theta series as Hecke eigenforms and class number one

There are many specific questions raised in this post. I will address the main one and show that if a $Q$ is a ternary quadratic form and the theta series $\theta_{Q}$ is a Hecke eigenform, then $Q$ h …
Jeremy Rouse's user avatar
  • 20.4k
7 votes
Accepted

Simple comparison of positive ternary quadratic form representation counts

No, this isn't true in general. You could, for example, take $f(x,y,z) = x^{2} + y^{2} + 13z^{2}$. Then $R(1) = 4$ and $R(25) = 12$. The form is isotropic at $5$ (since $5$ doesn't divide the discrimi …
Jeremy Rouse's user avatar
  • 20.4k
7 votes
Accepted

Class number for binary quadratic forms discriminant $\Delta$ to class number $\mathbb Q(\sq...

It seems to me that what Buell says about the narrow class group is not quite right (it's hard for me to say, as I don't have a copy of it). Magma tells me that in $\mathbb{Q}(\sqrt{210})$, the narrow …
Jeremy Rouse's user avatar
  • 20.4k
8 votes

The Chebotarev Density Theorem and the representation of infinitely many numbers by forms

The example of Heath-Brown's article is a good one. For a bit more elementary examples, you can fix a number field $K$ with $[K : \mathbb{Q}] = n$ and ring of integers $\mathcal{O}_{K}$ and pick a bas …
Jeremy Rouse's user avatar
  • 20.4k