Character table for the C₁₁ point group

C11     E       2 C11   2 C11^2 2 C11^3 2 C11^4 2 C11^5    <R> <p> <—d—> <——f——> <———g———> <————h————> <—————i—————> 
A       1.0000  1.0000  1.0000  1.0000  1.0000  1.0000     ..T ..T ....T ......T ........T ..........T ............T
E1  *   2.0000  1.6825  0.8308 -0.2846 -1.3097 -1.9189     TT. TT. ..TT. ....TT. ......TT. ........TT. ..........TT.
E2  *   2.0000  0.8308 -1.3097 -1.9189 -0.2846  1.6825     ... ... TT... ..TT... ....TT... ......TT... ........TT...
E3  *   2.0000 -0.2846 -1.9189  0.8308  1.6825 -1.3097     ... ... ..... TT..... ..TT..... ....TT..... ......TT.....
E4  *   2.0000 -1.3097 -0.2846  1.6825 -1.9189  0.8308     ... ... ..... ....... TT....... ..TT....... ....TT.......
E5  *   2.0000 -1.9189  1.6825 -1.3097  0.8308 -0.2846     ... ... ..... ....... ......... TT......... TTTT.........

 Irrational character values:  1.682507065662 = 2*cos(2*π/11)
                               0.830830026004 = 2*cos(4*π/11)
                              -0.284629676547 = 2*cos(6*π/11)
                              -1.309721467891 = 2*cos(8*π/11)
                              -1.918985947229 = 2*cos(10*π/11)



 Symmetry of Rotations and Cartesian products

A    R+p+d+f+g+h+i+j+k+l+m   Rz, z, z2, z3, z4, z5, z6 
E1   R+p+d+f+g+h+i+j+k+l+2m  {Rx, Ry}, {x, y}, {xz, yz}, {xz2, yz2}, {xz3, yz3}, {xz4, yz4}, {xz5, yz5} 
E2   d+f+g+h+i+j+k+2l+2m     {x2−y2, xy}, {z(x2−y2), xyz}, {z2(x2−y2), xyz2}, {z3(x2−y2), xyz3}, {z4(x2−y2), xyz4} 
E3   f+g+h+i+j+2k+2l+2m      {x(x2−3y2), y(3x2−y2)}, {xz(x2−3y2), yz(3x2−y2)}, {xz2(x2−3y2), yz2(3x2−y2)}, {xz3(x2−3y2), yz3(3x2−y2)} 
E4   g+h+i+2j+2k+2l+2m       {(x2−y2)2−4x2y2, xy(x2−y2)}, {z((x2−y2)2−4x2y2), xyz(x2−y2)}, {z2((x2−y2)2−4x2y2), xyz2(x2−y2)} 
E5   h+2i+2j+2k+2l+2m        {x(x2−(5+2√5)y2)(x2−(5−2√5)y2), y((5+2√5)x2−y2)((5−2√5)x2−y2)}, {x2(x2−3y2)2−y2(3x2−y2)2, xy(x2−3y2)(3x2−y2)}, {xz(x2−(5+2√5)y2)(x2−(5−2√5)y2), yz((5+2√5)x2−y2)((5−2√5)x2−y2)} 

 Notes:

    α  The order of the C11 point group is 11, and the order of the principal axis (C11) is 11. The group has 6 irreducible representations.

    β  The C11 point group is generated by one single symmetry element, C11. Therefore, it is a cyclic group.

    γ  The lowest nonvanishing multipole moment in C11 is 2 (dipole moment).

    δ  This is an Abelian point group (the commutative law holds between all symmetry operations).
       The C11 group is Abelian because it contains only one symmetry element, all the powers of which necessarily commute (sufficient condition).
       In Abelian groups, all symmetry operations form a class of their own, and all irreducible representations are one-dimensional.

    ε  Because the group is Abelian and the maximum order of rotation is >2, some irreducible representations have complex characters.
       These 10 cases have been combined into 5 two-dimensional representations that are no longer irreducible but have real-valued characters.
       Accordingly, 5 pairs of left and right rotations have been combined into one two-membered pseudo-class each.

    ζ  The 5 reducible “E” representations almost behave like true irreducible representations.
       Their norm, however, is twice the group order. Therefore, they have been marked with an asterisk in the table.
       This is essential when trying to decompose a reducible representation into “irreducible” ones using the familiar projection formula.

    η  The point group is chiral, as it does not contain any mirroring operation.

    θ  Some of the characters in the table are irrational because the order of the principal axis is neither 1,2,3,4 nor 6.
       These irrational values can be expressed as cosine values, or as solutions of algebraic equations with a leading coefficient of 1.
       All characters are algebraic integers of a degree just less than half the order of the principal axis.
       For this group, however, none of the irrational characters can be expressed by a closed algebraic form using real numbers only.

    ι  The regular hendecagon is the smallest regular polygon not constructible with ruler, compass and angle trisector.
       This is because 2*cos(2*π/11) has algebraic degree of five, being the solution of an irreducible quintic equation.
       Because this quintic equation is solvable, the value of cos(2*π/11) can be expressed using square and fifth roots and complex numbers.
       That algebraic form is, however, very complex and thus not shown here.