Примеры использования Coxeter diagram на Английском языке и их переводы на Русский язык
{-}
-
Official
-
Colloquial
Its Schläfli symbol is{∞}, and Coxeter diagram.
It has Coxeter diagram, and symmetry, order 72.
In this case the Dynkin diagrams exactly coincide with Coxeter diagrams.
Yellow edges labeled 4 come from right angle(unconnected)mirror nodes in the Coxeter diagram.
For each the Coxeter diagram can be deduced by identifying the hyperplane mirrors and labelling their connectivity, ignoring 90-degree dihedral angles order 2.
For example, the cube has Schläfli symbol{4,3}, and with its octahedral symmetry, or,it is represented by Coxeter diagram.
It is used in the definition of uniform prisms like Schläfli symbol{}×{p}, or Coxeter diagram as a Cartesian product of a line segment and a regular polygon.
Three different symbols are given for the same groups- as a letter/number,as a bracketed set of numbers, and as the Coxeter diagram.
For example, a real cube has Coxeter diagram, with octahedral symmetry order 48, and subgroup dihedral symmetry order 6, so the number of vertices of a cube is 48/6=8.
A 1-polytope is regular by definition andis represented by Schläfli symbol{}, or a Coxeter diagram with a single ringed node.
The unoriented Dynkin diagram is a form of Coxeter diagram, and corresponds to the Weyl group, which is the finite reflection group associated to the root system.
This operation for polyhedra is also called cantellation, e{p, q} e2{p, q} t0,2{p, q} rr{p, q},and has Coxeter diagram.
In parentheses are the orbifold notation,Coxeter notation(Coxeter diagram), the full Hermann-Mauguin notation, and the abbreviated one if different.
For example, the symbol A 2{\displaystyle A_{2}} may refer to:The Dynkin diagram with 2 connected nodes,, which may also be interpreted as a Coxeter diagram.
Thus Bn may refer to the unoriented diagram(a special kind of Coxeter diagram), the Weyl group(a concrete reflection group), or the abstract Coxeter group.
The A, D, E nomenclature also yields thesimply laced finite Coxeter groups, by the same diagrams: in this case the Dynkin diagrams exactly coincide with the Coxeter diagrams, as there are no multiple edges.
Beware also that while Dynkin diagram notation is standardized, Coxeter diagram and group notation is varied and sometimes agrees with Dynkin diagram notation and sometimes does not.
The down map is onto(by definition) but not one-to-one,as the Bn and Cn diagrams map to the same undirected diagram, with the resulting Coxeter diagram and Weyl group thus sometimes denoted BCn.
Two-dimensional hyperbolic triangle groups exist as rank 3 Coxeter diagrams, defined by triangle(p q r) for: 1 p+ 1 q+ 1 r< 1.{\displaystyle{\frac{ 1}{ p}}+{\ frac{ 1}{ q}}+{\ frac{1}{r}}.
Right angle fundamental triangles:(p q 2)General fundamental triangles:(p q r) Non-simplical fundamental domains The only possible fundamental domain in Euclidean 2-space that is not a simplex is the rectangle(∞ 2∞ 2), with Coxeter diagram.
As with all Wythoff constructions, polytopes generated by reflections,the number of vertices of a single-ringed Coxeter diagram polytope is equal to the order of the group divided by the order of the subgroup where the ringed node is removed.
A Coxeter-Dynkin diagram(or Coxeter diagram, Coxeter graph) is a graph with numerically labeled edges(called branches) representing the spatial relations between a collection of mirrors or reflecting hyperplanes.
Alternative convention include writing a number by the edge to indicate multiplicity(commonly used in Coxeter diagrams), darkening nodes to indicate root length, or using 120° angles on valence 2 nodes to make the nodes more distinct.
They can be seen in the Petrie polygons of the convex regular 4-polytopes, seen as regular plane polygons in the perimeter of Coxeter plane projection: In three dimensions, polytopes are called polyhedra: A regular polyhedron with Schläfli symbol{p,q}, Coxeter diagrams, has a regular face type{p}, and regular vertex figure{q.
Dynkin diagrams differ from Coxeter diagrams of finite groups in two important respects: Partly directed Dynkin diagrams are partly directed- any multiple edge(in Coxeter terms, labeled with"4" or above) has a direction(an arrow pointing from one node to the other); thus Dynkin diagrams have more data than the underlying Coxeter diagram undirected graph.
In general, a regular polychora with Schläfli symbol,{ p, q, r}{\displaystyle{\begin{Bmatrix}p, q,r\end{Bmatrix}}}, and Coxeter diagram, has a snub with extended Schläfli symbol s{ p, q, r}{\displaystyle s{\begin{Bmatrix}p, q, r\end{Bmatrix}}}, and.
Then Dynkin diagrams and Coxeter diagrams may be related as follows: By this is meant that Coxeter diagrams of finite groups correspond to point groups generated by reflections, while Dynkin diagrams must satisfy an additional restriction corresponding to the crystallographic restriction theorem, and that Coxeter diagrams are undirected, while Dynkin diagrams are(partly) directed.
The corresponding mathematical objects classified by the diagrams are: The blank in the upper right,corresponding to directed graphs with underlying undirected graph any Coxeter diagram(of a finite group), can be defined formally, but is little-discussed, and does not appear to admit a simple interpretation in terms of mathematical objects of interest.
Dynkin diagrams are closely related objects, which differ from Coxeter diagrams in two respects: firstly, branches labeled"4" orgreater are directed, while Coxeter diagrams are undirected; secondly, Dynkin diagrams must satisfy an additional(crystallographic) restriction, namely that the only allowed branch labels are 2, 3, 4, and 6.