Questions tagged [lattices]
Lattices in the sense of discrete subgroups of Euclidean spaces, as used in number theory, discrete geometry, Lie groups, etc. (Not to be confused with lattice theory or lattices as used in physics! For lattices (ordered sets), use the tag: [lattice-theory])
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Minimal volume of fundamental domains of lattices
Consider a full rank integer lattice in $\mathbb{R}^n$. Let $v_1$ be the shortest non-zero vector in the lattice, $v_2$ be the shortest one among those not parallel to $v_1$, $v_3$ be the shortest one ...
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Computing the genus of certain ternary indefinite lattices
For $k$ a positive integer, let us consider the rank 3 ternary indefinite lattice $L=L_k$ with quadratic form
$$6kx^2-2(y^2+yz+z^2).$$
Its discriminant group has length $2$.
Question. Is this lattice ...
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Volume and basis for integer lattice subject to sparse constraint
Let $k<n$ be integers. Let $A\in \mathbb{Z}^{k \times n}$ be a sparse matrix, meaning that the number of nonzero entries in every row and every column is at most $O(1)$. Further, assume that ...
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density of lattices
I'm looking for references pertaining to the remark at the bottom of p.18 of Conway-Sloane, "Sphere Packings, Lattices and Groups" (3rd ed), henceforth referred to as "SPLG".
First,...
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Stabilizer in $G(\mathbb{Z})$ of point in fundamental domain $G(\mathbb{Z}) \backslash G(\mathbb{R}) / K$
Let $G$ be a semisimple group (the cases of primary interest to me are where $G$ is a special linear group or a special orthogonal group), let $K$ be a maximal compact subgroup of $G(\mathbb{R})$, and ...
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Lattices of $\mathbb{R}^s \ltimes_\varphi \mathbb{R}^k$
Edit: Thoughts updated (22/3/2021).
I've come across with the following problem.
Let $G=\mathbb{R}^s \ltimes_\varphi \mathbb{R}^k$ where $\varphi:\mathbb{R}^s\to \mathrm{Aut}(\mathbb{R}^k)=\mathsf{GL}(...
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About weight generator of quadratic lattices
I get stuck on Example 93:5 in O'Meara's book "Introduction to quadratic forms", where it is explained a method of find a weight generator of a quadratic lattice.
In this question I assume ...
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Computer program which computes the automorphism group of Gram Matrix of lattice?
$\DeclareMathOperator\GL{GL}\DeclareMathOperator\Aut{Aut}$Fixed $n \geq 2$, given $K \in \GL(n,Z)$. One can view $K$ is a Gram matrix of Lattice. I also imposed that $K$ is symmetric i.e $K^{T}=K$. We ...
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Number of lattice points in a structural symmetric convex body
Let $f$ is a convex symmetric function on the interval $[-a,a]$, i.e., $f(-x)=f(x)$ for $\forall \, x\in [-a,a]$. Then we consider a $n$-dimensional convex body in Euclidean space
\begin{equation}
\...
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Anchor sets for lattice polygons: Part I
Suppose $V=\{(x_1,y_1), (x_2,y_2),\dots,(x_v,y_v)\}$ is a vertex set of lattice points satisfying
$$0=x_1<x_2<\dots<x_v \qquad \text{and} \qquad y_1>y_2>\cdots>y_{v-1}>y_v=0.$$
...
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When does a subgroup of $\operatorname{GL}(n, \mathbb Q)$ have a bounded fundamental domain on $\mathbb R^n$?
$\DeclareMathOperator\GL{GL}$Let $G \subset M_{n\times n~}(\mathbb Z)$ be a finitely generated subgroup of $\GL(n,\mathbb Q)$ (i.e. $g\in G$ is an invertible matrix with entries in $\mathbb Z$). Then $...
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Vectors with minimal Hamming weight in a rational vector space?
Suppose given $n\ge 1$ and a subspace $U$ in $\mathbb{Q}^n$. It is given as $\mathbb{Q}$-span of certain known vectors.
For $x \in U$, we let the Hamming weight of $x$ be the number of its nonzero ...
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Understanding fusion categories from the perspective of anyons?
ncatlab defines a fusion category as "A fusion category is a rigid semisimple linear (Vect-enriched) monoidal category (“tensor category”), with only finitely many isomorphism classes of simple ...
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Sublattices in the standard integral symplectic lattice
Let $V$ denote $\mathbb{Z}^{2g}$ with its standard integral symplectic form $\omega = \sum_{i=0}^{g-1}dx_{2i} \wedge dx_{2i+1}$ (or, the homology lattice of a genus $g$ surface with its intersection ...
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Ordering preserved by an inverse frame homomorphism
Recall that a frame homomorphism $h:L\to M$ is called ($L$ and $M$ are frames):
Dense if, for any $x ∈ L$, $h(x) = 0$ implies $x = 0$.
Codense if, for any $x ∈ L$, $h(x) = 1$ implies $x = 1$.
...
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How can I construct an element in a particular "quadrant" of a lattice (preferably short)?
Given a basis for a full-rank lattice $\mathcal{L} \subset \mathbb{R}^n$ I want to find a vector with totally positive entries, in other words an element belonging to $\mathcal{L} \cap Q$ where $Q$ is ...
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How much Gleason type theorem do I need? Quasi states vs. states
Let $\varphi$ be a quasi state on $B(H)$. What does it mean? It means that $\varphi(cA)=c\varphi(A)$ for $c \in \mathbb{C}, A \in B(H)$, $\varphi(A) \geq 0$ for positive $A$ and $\varphi(A+B)=\varphi(...
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Bound on mutually x-ray-visible lattice points?
Say that two lattice points $a$ and $b$ of $\mathbb{Z}^d$
are $x$-visible to one another if the segment $ab$
contains at most $x$ lattice points (excluding $a$ and $b$).
So $x$-visiblity is "x-...
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There are at most four mutually visible lattice points—?
Say that two lattice points $a$ and $b$ of $\mathbb{Z}^2$
are visible to one another if the line segment $ab$
contains no other lattice points.
While exploring lattice polygons all of whose vertices
...
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A number theoretic unlikely intersection phenomenon
Let $h_1, \cdots, h_k$ be co-prime integers, $k \geq 3$. Let $n$ be a square-free positive integer, understood to be extremely large compared to the $h_i$'s, and such that $\omega(n)$, the number of ...
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Efficiently find at least one lattice point on hyperbola of equation $axy+bx+cy+d=0$
I need an algorithm to efficiently find at least one lattice point on a hyperbola of equation $axy+bx+cy+d=0$.
Lattice point means integer coordinates and equation with integer means diophantine ...
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Conway big picture for congruence subgroups of $\mathrm{SL}_3(\mathbb{Z})$
I saw in Conway’s paper "Understanding groups like $\Gamma_0(N)$" that the so-called Big Picture can give simple interpretations for important objects in number theory, such as Hecke ...
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Source on counting lattice points on a line
Looking for a book or article on the result linked below. The result tells us that the number of lattice points on a line between points $(a,b)$ and $(c,d)$ is given by $\gcd(a-c,b-d)+1$.
https://math....
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Deep Holes of the tensor product of two lattices
Let $L_0, L_1$ be Euclidean lattices (say full rank) of dimension $n_i$. Let $\lambda_1(L_i)$ denote the length of the shortest vector of $L_i$, and let $\rho(L_i)$ denote the covering radius of $L_i$:...
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Deciding isometry of unimodular lattices by Gram matrices
Say I have two unimodular lattices $A$ and $B$, represented by their Gram matrices.
Question: Is there an algorithm to decide whether $A$ and $B$ are isometric, i.e. whether there exists a matrix $S \...
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Property of convex polygons on integer lattice structures
Another graduate student and I are working on an research project and are looking for a paper or other source that has a proof for a result about polygons on an integer lattice structure. Suppose you ...
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Do discrete embeddings of surface groups not necessarily carry an embedding of SL_2?
We can get arithmetic lattices isomorphic to free groups in $\mathrm{SL}_2\mathbb{R}$, so in general we can’t expect homomorphisms of lattices into semisimple Lie groups to say much about $\mathrm{SL}...
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Characterization of certain 4-dimensional lattices
Let $\Lambda \subset {\bf Q}^4$ be a lattice, i.e., $\Lambda$ is a free abelian group and $\Lambda \otimes {\bf Q} = {\bf Q^4}$.
The determinants of those dilation-rotations (i.e. linear maps of ${\bf ...
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number of integer points inside a triangle and its area
Let $T$ be a triangle in $\mathbb{R}^2$ defined by $y = \alpha x$, $y = \beta$ and $x = \gamma$ where
$\alpha, \beta, \gamma \in \mathbb{R}_{>0}$. I am interested in obtaining an estimate for the ...
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Counting integral points in a rank-2 lattice
Let $\Lambda \subset \mathbb{Z}^n, n \geq 2$ be a lattice of rank 2. It is well-known (see for example Lemma 4.5 in this book) that
$$\displaystyle \#\{\mathbf{x} \in \Lambda : \mathbf{x} \text{ is ...
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Matrix groups with two generators
Given two matrices $A,B\in{\rm{SL}}_2(\Bbb{R})$, is there any criterion guaranteeing that the subgroup they generate is discrete? What if one puts restrictions on $A,B$ e.g. they are both elliptic? ...
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Theta Function Associated to Kummer Lattice
This is something which I feel must be out in the literature somewhere, but I have been unable to find anything.
If we let $\text{Km}(A)$ be the Kummer $K3$ surface associated to an abelian surface $A$...
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Does the standard arithmetic subgroup of a closed $\mathbb{Q}$-algebraic groups have non-trivial $\mathbb{Q}$-characters?
I am trying to understand the Borel-Harish Chandra theorem about arithmetic subgroups being lattices.
Suppose $G$ is an algebraic group inside $GL_n(\mathbb{C})$ such that it is definable as a zero ...
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2
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lattice suprema vs pointwise suprema
What is the difference between the lattice supremum and the pointwise supremum of a family of functions? I mean, given a family of real valued functions $\mathcal{F}$, is the function $\sup\mathcal{F}:...
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Euler characteristic with compact support of spaces of Euclidean lattices
Has the Euler characteristic with compact support of $\mathrm{SL}_n(\mathbb R)/\mathrm{SL}_n(\mathbb Z)$ been computed ? References? Thanks.
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Can all proper sublattices of $\mathbb{Z}^n$ be generated cyclically?
Let $\Lambda \subset \mathbb{Z}^n$ be a proper sublattice (so that $\Lambda \ne \mathbb{Z}^n$). We say that $\Lambda$ is cyclically generated if there exists a matrix $M \in \text{GL}_n(\mathbb{Z})$ ...
9
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A lattice with Monster group symmetries
The book Mathematical Evolutions contains the following excerpt:
A last, famous, example is the following. It is known that in the space
of one hundred and ninety six thousand eight hundred and ...
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Getting more out of Minkowski's convex body theorem in the case of non-convex bodies
Problem. In number theory one generally proves the finiteness of the Picard group of a number field using Minkowski's convex body theorem. The actual body $S_p$ of interest in the proof, depending on ...
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Why do bees create hexagonal cells ? (Mathematical reasons)
Question 0 Are there any mathematical phenomena which are related to the form of honeycomb cells?
Question 1 Maybe hexagonal lattices satisfy certain optimality condition(s) which are related to it? ...
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Given a lattice in $\mathbb{Z}^n$, what can be said about its 'transpose' lattice?
I apologize if this notion is well-known, but I couldn't find anything useful and I am not sure what key words to look for.
Suppose we have a lattice $\Lambda \subset \mathbb{Z}^n$, given by in the ...
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Lattice points in hypercubes
Let $ (\Lambda_n) $ be a family of lattices, $ \Lambda_n \subset \mathbb{Z}^n $, with $ \det\Lambda_n \sim n $ as $ n \to \infty $ (meaning $ \lim_{n\to\infty} n^{-1} \det\Lambda_n = 1$). I am ...
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Finding a superbase in a lattice of Voronoi first kind
An $n$-dimensional lattice in $\mathbb R^n$ is said to be of Voronoi’s first kind if it there exists $n+1$ vectors $b_1,\cdots b_{n+1}$ (called the superbase) such that
$\{b_1,\ldots,b_n \}$ is a ...
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Number of points in a lattice and an oblong box
I have a very simple question in geometry of numbers. (It is a slight modification of Counting points on the intersection of a box and a lattice .) There's a bound I can easily prove, and it's good ...
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An integral Jacobson-Morozov theorem?
$\DeclareMathOperator\SL{SL}$I want to ask if there exists a version of the Jacobson–Morozov theorem for integer matrices. A first approximation would ask: given an integral unipotent matrix $m \in \...
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Reference request: placing a set with respect to the integer grid
For $x=(x_1,...,x_n)\in \mathbb{R}^n$, let $Q_x=(x_1,x_1+1)\times ...\times (x_n,x_n+1)$ - the open cube having $x$ in its "bottom left" corner. It seems, I can prove (see a draft here) the following
...
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what is the number of paths returning to 0 on the hexagonal lattice
I am looking for an estimation of the number of paths of length $n$ going from 0 to 0 on the hexagonal (or honeycomb) lattice.
I can find plenty on references on self avoiding paths, but I am looking ...
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Homomorphisms from higher rank lattices with infinite center to $\mathbb{Z}$
Suppose that $\Gamma$ is an irreducible lattice in a semi-simple real Lie group $G$ of higher rank (with infinite center!), is every homomorphism $\Gamma \to \mathbb{Z}$ trivial?
The case where $G$ ...
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Small linear relations in unbalanced diophantine equations from primitive Pythagorean triples
$r$ is parameter. Pick coprime $m,n\in[r,2r]$ with $mn$ even. Consider the Linear Diophantine Equation $$a^4u+b^4v+c^2z=0$$ where $a=m^2-n^2$, $b=2mn$ and $c=m^2+n^2$.
Is it true that there are ...
0
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0
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Upper bounds on the length of the shortest vector in lattices associated to polynomial congruences
We consider a lattice $\Lambda \subset \mathbb{Z}^2$, and put $\lambda_1(\Lambda), \lambda_2(\Lambda)$ for successive minima of the lattice $\Lambda$.
By a well-known theorem of Minkowski, one has ...
2
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Another generalization of the Gauss circle problem
In this question I asked for a generalization of the Gauss circle problem, the type of generalization I am asking is to view the Gauss circle problem as one about counting algebraic integers of ...