A pattern with this lattice of translational symmetry cannot have more, but may have less symmetry than the lattice itself. A lattice in the sense of a 3- dimensional array of regularly spaced points coinciding with e. Lattices called root lattices are important in the theory of simple Lie algebras ; for example, the E8 lattice is related to a Lie algebra that goes by the same name.

If this equals 1, the lattice is called unimodular. The number of lattice points contained in a polytope all of whose vertices are elements of the lattice is described by the polytope's Ehrhart polynomial. Computational lattice problems have many applications in computer science. There are five 2D lattice types as given by the crystallographic restriction theorem. Below, the wallpaper group of the lattice is given in IUC notation , Orbifold notation , and Coxeter notation , along with a wallpaper diagram showing the symmetry domains.

Note that a pattern with this lattice of translational symmetry cannot have more, but may have less symmetry than the lattice itself. A full list of subgroups is available. If the symmetry group of a pattern contains an n -fold rotation then the lattice has n -fold symmetry for even n and 2 n -fold for odd n. For the classification of a given lattice, start with one point and take a nearest second point.

## A Lattice Point Counting Problem relating to the Heisenberg Groups

For the third point, not on the same line, consider its distances to both points. Among the points for which the smaller of these two distances is least, choose a point for which the larger of the two is least. Not logically equivalent but in the case of lattices giving the same result is just "Choose a point for which the larger of the two is least". The five cases correspond to the triangle being equilateral, right isosceles, right, isosceles, and scalene.

## Minkowski's theorem - Wikipedia

In a rhombic lattice, the shortest distance may either be a diagonal or a side of the rhombus, i. The general case is known as a period lattice. If the vectors p and q generate the lattice, instead of p and q we can also take p and p - q , etc. This ensures that p and q themselves are integer linear combinations of the other two vectors. Each pair p , q defines a parallelogram, all with the same area, the magnitude of the cross product. One parallelogram fully defines the whole object.

### Your Answer

Without further symmetry, this parallelogram is a fundamental parallelogram. The vectors p and q can be represented by complex numbers. We use a bound obtained by Swinnerton-Dyer's approximation determinant method.

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