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In mathematics, the special orthogonal group in three dimensions, otherwise known as the rotation group SO(3), is a naturally occurring example of a manifold.The various charts on SO(3) set up rival coordinate systems: in this case there cannot be said to be a preferred set of parameters describing a rotation.
The Lie algebra of SO(3) is denoted by () and consists of all skew-symmetric 3 × 3 matrices. [7] This may be seen by differentiating the orthogonality condition , A T A = I , A ∈ SO(3) . [ nb 2 ] The Lie bracket of two elements of s o ( 3 ) {\displaystyle {\mathfrak {so}}(3)} is, as for the Lie algebra of every matrix group, given by the ...
Thus as an irreducible representation of SO(3), H ℓ is isomorphic to the space of traceless symmetric tensors of degree ℓ. More generally, the analogous statements hold in higher dimensions: the space H ℓ of spherical harmonics on the n-sphere is the irreducible representation of SO(n+1) corresponding to the traceless symmetric ℓ-tensors.
The identity rotation I and the central inversion −I form a group C 2 of order 2, which is the centre of SO(4) and of both S 3 L and S 3 R. The centre of a group is a normal subgroup of that group. The factor group of C 2 in SO(4) is isomorphic to SO(3) × SO(3). The factor groups of S 3 L by C 2 and of S 3 R by C 2 are each isomorphic to
A graph is planar if it contains as a subdivision neither the complete bipartite graph K 3,3 nor the complete graph K 5. Another problem in subdivision containment is the Kelmans–Seymour conjecture: Every 5-vertex-connected graph that is not planar contains a subdivision of the 5-vertex complete graph K 5.
For example, when assigning aircraft to flights, the resulting conflict graph is an interval graph, so the coloring problem can be solved efficiently. In bandwidth allocation to radio stations, the resulting conflict graph is a unit disk graph, so the coloring problem is 3-approximable.
For a graph G, let χ(G) denote the chromatic number and Δ(G) the maximum degree of G.The list coloring number ch(G) satisfies the following properties.. ch(G) ≥ χ(G).A k-list-colorable graph must in particular have a list coloring when every vertex is assigned the same list of k colors, which corresponds to a usual k-coloring.
No graph can be 0-colored, so 0 is always a chromatic root. Only edgeless graphs can be 1-colored, so 1 is a chromatic root of every graph with at least one edge. On the other hand, except for these two points, no graph can have a chromatic root at a real number smaller than or equal to 32/27. [8]