# Root system data for type D¶

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

EXAMPLES:

sage: e = RootSystem(['A',3]).ambient_lattice()
sage: s = e.simple_reflections()

sage: L = RootSystem(['A',3]).coroot_lattice()
sage: e.has_coerce_map_from(L)
True
sage: e(L.simple_root(1))
(1, -1, 0, 0)

dimension()

EXAMPLES:

sage: e = RootSystem(['D',3]).ambient_space()
sage: e.dimension()
3

fundamental_weight(i)

EXAMPLES:

sage: RootSystem(['D',4]).ambient_space().fundamental_weights()
Finite family {1: (1, 0, 0, 0), 2: (1, 1, 0, 0), 3: (1/2, 1/2, 1/2, -1/2), 4: (1/2, 1/2, 1/2, 1/2)}

negative_roots()

EXAMPLES:

sage: RootSystem(['D',4]).ambient_space().negative_roots()
[(-1, 1, 0, 0),
(-1, 0, 1, 0),
(0, -1, 1, 0),
(-1, 0, 0, 1),
(0, -1, 0, 1),
(0, 0, -1, 1),
(-1, -1, 0, 0),
(-1, 0, -1, 0),
(0, -1, -1, 0),
(-1, 0, 0, -1),
(0, -1, 0, -1),
(0, 0, -1, -1)]

positive_roots()

EXAMPLES:

sage: RootSystem(['D',4]).ambient_space().positive_roots()
[(1, 1, 0, 0),
(1, 0, 1, 0),
(0, 1, 1, 0),
(1, 0, 0, 1),
(0, 1, 0, 1),
(0, 0, 1, 1),
(1, -1, 0, 0),
(1, 0, -1, 0),
(0, 1, -1, 0),
(1, 0, 0, -1),
(0, 1, 0, -1),
(0, 0, 1, -1)]

root(i, j, p1, p2)

Note that indexing starts at 0.

EXAMPLES:

sage: e = RootSystem(['D',3]).ambient_space()
sage: e.root(0, 1, 1, 1)
(-1, -1, 0)
sage: e.root(0, 0, 1, 1)
(-1, 0, 0)

simple_root(i)

EXAMPLES:

sage: RootSystem(['D',4]).ambient_space().simple_roots()
Finite family {1: (1, -1, 0, 0), 2: (0, 1, -1, 0), 3: (0, 0, 1, -1), 4: (0, 0, 1, 1)}

class sage.combinat.root_system.type_D.CartanType(n)

EXAMPLES:

sage: ct = CartanType(['D',4])
sage: ct
['D', 4]
sage: ct._repr_(compact = True)
'D4'

sage: ct.is_irreducible()
True
sage: ct.is_finite()
True
sage: ct.is_crystallographic()
True
sage: ct.is_simply_laced()
True
sage: ct.dual()
['D', 4]
sage: ct.affine()
['D', 4, 1]

sage: ct = CartanType(['D',2])
sage: ct.is_irreducible()
False
sage: ct.dual()
['D', 2]
sage: ct.affine()
Traceback (most recent call last):
...
ValueError: ['D', 2, 1] is not a valid Cartan type


TESTS:

sage: TestSuite(ct).run()

AmbientSpace

alias of AmbientSpace

ascii_art(label=<function <lambda> at 0x7f6692205320>, node=None)

Return a ascii art representation of the extended Dynkin diagram.

EXAMPLES:

sage: print CartanType(['D',3]).ascii_art()
O 3
|
|
O---O
1   2
sage: print CartanType(['D',4]).ascii_art()
O 4
|
|
O---O---O
1   2   3
sage: print CartanType(['D',4]).ascii_art(label = lambda x: x+2)
O 6
|
|
O---O---O
3   4   5
sage: print CartanType(['D',6]).ascii_art(label = lambda x: x+2)
O 8
|
|
O---O---O---O---O
3   4   5   6   7

coxeter_number()

Return the Coxeter number associated with self.

EXAMPLES:

sage: CartanType(['D',4]).coxeter_number()
6

dual_coxeter_number()

Return the dual Coxeter number associated with self.

EXAMPLES:

sage: CartanType(['D',4]).dual_coxeter_number()
6

dynkin_diagram()

Returns a Dynkin diagram for type D.

EXAMPLES:

sage: d = CartanType(['D',5]).dynkin_diagram(); d
O 5
|
|
O---O---O---O
1   2   3   4
D5
sage: sorted(d.edges())
[(1, 2, 1), (2, 1, 1), (2, 3, 1), (3, 2, 1), (3, 4, 1), (3, 5, 1), (4, 3, 1), (5, 3, 1)]

sage: d = CartanType(['D',4]).dynkin_diagram(); d
O 4
|
|
O---O---O
1   2   3
D4
sage: sorted(d.edges())
[(1, 2, 1), (2, 1, 1), (2, 3, 1), (2, 4, 1), (3, 2, 1), (4, 2, 1)]

sage: d = CartanType(['D',3]).dynkin_diagram(); d
O 3
|
|
O---O
1   2
D3
sage: sorted(d.edges())
[(1, 2, 1), (1, 3, 1), (2, 1, 1), (3, 1, 1)]

sage: d = CartanType(['D',2]).dynkin_diagram(); d
O   O
1   2
D2
sage: sorted(d.edges())
[]

is_atomic()

Implements CartanType_abstract.is_atomic()

$$D_2$$ is atomic, like all $$D_n$$, despite being non irreducible.

EXAMPLES:

sage: CartanType(["D",2]).is_atomic()
True
sage: CartanType(["D",2]).is_irreducible()
False


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