Root system data for type F

class sage.combinat.root_system.type_F.AmbientSpace(root_system, base_ring)

Bases: sage.combinat.root_system.ambient_space.AmbientSpace

The lattice behind F4. The computations are based on Bourbaki, Groupes et Algebres de Lie, Ch. 4,5,6 (planche VIII).

dimension()

EXAMPLES:

sage: e = RootSystem(['F',4]).ambient_space()
sage: e.dimension()
4
fundamental_weights()

EXAMPLES:

sage: e =  RootSystem(['F',4]).ambient_space()
sage: e.fundamental_weights()
Finite family {1: (1, 1, 0, 0), 2: (2, 1, 1, 0), 3: (3/2, 1/2, 1/2, 1/2), 4: (1, 0, 0, 0)}
negative_roots()

Returns the negative roots in self.

EXAMPLES:

sage: e = RootSystem(['F',4]).ambient_space()
sage: e.negative_roots()
[(-1, 0, 0, 0),
(0, -1, 0, 0),
(0, 0, -1, 0),
(0, 0, 0, -1),
(-1, -1, 0, 0),
(-1, 0, -1, 0),
(-1, 0, 0, -1),
(0, -1, -1, 0),
(0, -1, 0, -1),
(0, 0, -1, -1),
(-1, 1, 0, 0),
(-1, 0, 1, 0),
(-1, 0, 0, 1),
(0, -1, 1, 0),
(0, -1, 0, 1),
(0, 0, -1, 1),
(-1/2, -1/2, -1/2, -1/2),
(-1/2, -1/2, -1/2, 1/2),
(-1/2, -1/2, 1/2, -1/2),
(-1/2, -1/2, 1/2, 1/2),
(-1/2, 1/2, -1/2, -1/2),
(-1/2, 1/2, -1/2, 1/2),
(-1/2, 1/2, 1/2, -1/2),
(-1/2, 1/2, 1/2, 1/2)]
positive_roots()

These are the roots positive w.r. to lexicographic ordering of the basis elements (e1<...<e4).

EXAMPLES:

sage: e = RootSystem(['F',4]).ambient_space()
sage: e.positive_roots()
[(1, 0, 0, 0),
(0, 1, 0, 0),
(0, 0, 1, 0),
(0, 0, 0, 1),
(1, 1, 0, 0),
(1, 0, 1, 0),
(1, 0, 0, 1),
(0, 1, 1, 0),
(0, 1, 0, 1),
(0, 0, 1, 1),
(1, -1, 0, 0),
(1, 0, -1, 0),
(1, 0, 0, -1),
(0, 1, -1, 0),
(0, 1, 0, -1),
(0, 0, 1, -1),
(1/2, 1/2, 1/2, 1/2),
(1/2, 1/2, 1/2, -1/2),
(1/2, 1/2, -1/2, 1/2),
(1/2, 1/2, -1/2, -1/2),
(1/2, -1/2, 1/2, 1/2),
(1/2, -1/2, 1/2, -1/2),
(1/2, -1/2, -1/2, 1/2),
(1/2, -1/2, -1/2, -1/2)]
sage: e.rho()
(11/2, 5/2, 3/2, 1/2)
root(i, j=None, k=None, l=None, p1=0, p2=0, p3=0, p4=0)

Compute a root from base elements of the underlying lattice. The arguments specify the basis elements and the signs. Sadly, the base elements are indexed zero-based. We assume that if one of the indices is not given, the rest are not as well.

EXAMPLES:

sage: e = RootSystem(['F',4]).ambient_space()
sage: [ e.root(i,j,p2=1) for i in xrange(e.n) for j in xrange(i+1,e.n) ]
[(1, -1, 0, 0), (1, 0, -1, 0), (1, 0, 0, -1), (0, 1, -1, 0), (0, 1, 0, -1), (0, 0, 1, -1)]
simple_root(i)
There are computed as what Bourbaki calls the Base:
a1 = e2-e3, a2 = e3-e4, a3 = e4, a4 = 1/2*(e1-e2-e3-e4)

EXAMPLES:

sage: e = RootSystem(['F',4]).ambient_space()
sage: e.simple_roots()
Finite family {1: (0, 1, -1, 0), 2: (0, 0, 1, -1), 3: (0, 0, 0, 1), 4: (1/2, -1/2, -1/2, -1/2)}
class sage.combinat.root_system.type_F.CartanType

Bases: sage.combinat.root_system.cartan_type.CartanType_standard_finite, sage.combinat.root_system.cartan_type.CartanType_simple, sage.combinat.root_system.cartan_type.CartanType_crystalographic

EXAMPLES:

sage: ct = CartanType(['F',4])
sage: ct
['F', 4]
sage: ct._repr_(compact = True)
'F4'

sage: ct.is_irreducible()
True
sage: ct.is_finite()
True
sage: ct.is_crystalographic()
True
sage: ct.is_simply_laced()
False
sage: ct.dual()
['F', 4]^*
sage: ct.affine()
['F', 4, 1]

TESTS:

sage: ct == loads(dumps(ct))
True
AmbientSpace

alias of AmbientSpace

ascii_art(label=<function <lambda> at 0x4380c80>)

Returns a ascii art representation of the extended Dynkin diagram

EXAMPLES:

sage: print CartanType(['F',4]).ascii_art(label = lambda x: x+2)
O---O=>=O---O
3   4   5   6
dynkin_diagram()

Returns a Dynkin diagram for type F.

EXAMPLES:

sage: f = CartanType(['F',4]).dynkin_diagram()
sage: f
O---O=>=O---O
1   2   3   4
F4
sage: sorted(f.edges())
[(1, 2, 1), (2, 1, 1), (2, 3, 2), (3, 2, 1), (3, 4, 1), (4, 3, 1)]

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