# Questions tagged [quadratic-forms]

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.

**5**

**0**answers

### System of quadratic equations

**4**

**0**answers

### Witt ring of a field with Pythagoras number $2$

**1**

**0**answers

### Existence of solutions to quadratic vector equation

**1**

**0**answers

### Simultaneous diagonalization of two rational forms

**2**

**0**answers

### Is there an integer-valued quadratic polynomial $P(x,y)$ such that $\{P(x,y)+2^k:\ x,y\in\mathbb Z\ \text{and}\ k\in\mathbb N\}=\mathbb Z^+$?

**2**

**1**answer

### When are rings of the form $K[x_1,…,x_n]/(Q)$ principal ideal domains when $Q$ is quadratic?

**4**

**1**answer

### Computing the genus of certain ternary indefinite lattices

**4**

**1**answer

### Classification of vector spaces with a quadratic form and an order n automorphism

**1**

**2**answers

### Convexity of inverse quadratic form

**3**

**1**answer

### The covariance matrix of quadratic form, without normal assumption

**3**

**2**answers

### Generators of the orthogonal group of a quadratic form in odd dimension in characteristic 2

**4**

**1**answer

### Is the map $GL_n(\mathbb{Z})\to GL_n(\mathbb{Z}/2\mathbb{Z})$ surjective?

**1**

**0**answers

### finding automorphisms of binary hermitian forms

**3**

**1**answer

### Under what conditions is the polynomial of degree $6$ irreducible?

**4**

**1**answer

### Finding Motzkin's original paper on copositive quadratic forms

**2**

**1**answer

### binary quadratic forms order four in the form class group not having desired coefficients

**19**

**1**answer

### A list of proofs of the Hasse–Minkowski theorem

**5**

**1**answer

### Modular forms and number of representations by binary quadratic forms

**1**

**0**answers

### The splitting pattern of the Killing form of an algebraic group and the Tits index

**1**

**0**answers

### Rational quadratic form with given determinant and Hasse-Witt invariant

**1**

**0**answers

### About weight generator of quadratic lattices

**1**

**1**answer

### How do you solve this quadratic matrix equation?

**3**

**2**answers

### Correspondence between binary quadratic representations and proper ideals of quadratic number fields

**5**

**0**answers

### Linearly independent quadratic forms vanishing on a finite set of points

**1**

**0**answers

### How should the first n natural numbers be arranged in a circle to minimize the sum of the products of adjacent pairs? [closed]

**6**

**1**answer

### Hasse invariant and the Clifford algbera

**1**

**0**answers

### Siegel's formula for generalized theta series with characteristics?

**0**

**0**answers

### Integral of the product l of the pdf of two univariate gaussian regression models with respect to the parameter

**7**

**0**answers

### the gaps between values of a positive binary quadratic form at integer points

**8**

**1**answer

### Standard conjecture on u-invariants?

**-1**

**1**answer

### Questions on $x^2+y^2+z^2$, $x^2+y^2+2z^2$ and $x^2+2y^2+3z^2$

**6**

**1**answer

### Invariant Lagrangian in the first homology of a cover of a surface

**4**

**1**answer

### Is there a trigonometric field which is different enough from real numbers?

**2**

**0**answers

### Is there a method to solve a non-linear quadratic matrix equation?

**-1**

**1**answer

### $7n=x^2+2y^2+4z^2$ with or without $x^2\equiv y^2\equiv z^2\pmod 7$

**9**

**0**answers

### Leech lattice and rational varieties

**4**

**1**answer

### Conics and triples of binary quadratic forms

**5**

**1**answer

### Proof that $x^2 + y^2 - z^2$ is universal

**5**

**1**answer

### Set of quadratic forms that represents all primes

**3**

**1**answer

### Reference request: relationship between discriminant and smoothness of a conic over arbitrary fields

**2**

**0**answers

### Existence theorem for symmetric nondegenerate forms over a ring

**7**

**2**answers

### Determining if a quadratic form is non-negative if variables are non-negative

**11**

**0**answers

### Characterization of certain 4-dimensional lattices

**0**

**0**answers

### Can you efficiently solve a linear system with a quadratic multivariate polynomial of degree 2?

**0**

**1**answer

### The stabiliser group of an isotropic quadratic form over $\mathbb{Q}_p$ is non-compact?

**-3**

**1**answer

### Doubt about lemma for polynomial equivalence [closed]

**6**

**3**answers

### Representation theorem for quadratic form on Hilbert space

**2**

**0**answers

### Maximal connected subgroup of orthogonal group

**1**

**0**answers

### Stabilizer group uniquely determines subspace

**3**

**1**answer