def character(self):
r"""
Return the character of this module `M` in the `C` basis
OUTPUT:
- a linear combination `\chi(M) = \sum c_i C_i`, where
`c_i` is the character (i.e. the trace) on `M` of any
idempotent `e` in the regular `J`-class indexed by `i`.
EXAMPLES::
sage: M = Monoids().HTrivial().Finite().example(); M
The finite H-trivial monoid of order preserving maps on {1, .., 3}
sage: M.rename("M")
sage: R = M.regular_representation(side = 'left')
sage: R.character()
10*C[0] + 4*C[1] + C[2]
sage: R.character().parent()
The left-character ring of M over Rational Field in the basis of characters of left-class functions modules
sage: R = M.regular_representation(side = 'right')
sage: R.character()
10*C[0] + 6*C[1] + 3*C[2]
sage: R.character().parent()
The right-character ring of M over Rational Field in the basis of characters of right-class functions modules
"""
S = self.semigroup()
C = S.character_ring(self.base_ring(), side=self.side()).C()
base_ring = C.base_ring()
e = S.j_transversal_of_idempotents()
# Remark: let e and f be two idempotents, and identify
# them with the corresponding linear projections
# acting on ``self``. If e <=_J f, then the rank of e
# is smaller than the rank of f.
#
# Corollary: the set of idempotents having non zero
# character (the support below) is an upper ideal in J-order.
#
# We use this to avoid computing the character for all
# regular J-classes.
#
# I am not yet sure that this works in non zero
# characteristic, so let's be safe.
assert self.base_ring().characteristic() == 0
from sage.combinat.backtrack import TransitiveIdeal
P = S.j_poset_on_regular_classes()
@cached_function
def character(i):
return self.character_of(e[i])
def children(i):
return (j for j in P.lower_covers(i) if character(j))
support = TransitiveIdeal(children, [P.top()])
return C.sum_of_terms(
(i, base_ring(character(i))) for i in support)
def __iter__(self, index_set=None, max_depth=float('inf')):
"""
Return an iterator over the elements of ``self``.
INPUT:
- ``index_set`` -- (Default: ``None``) The index set; if ``None``
then use the index set of the crystal
- ``max_depth`` -- (Default: infinity) The maximum depth to build
The iteration order is not specified except that, if
``max_depth`` is finite, then the iteration goes depth by
depth.
EXAMPLES::
sage: C = crystals.LSPaths(['A',2,1],[-1,0,1])
sage: C.__iter__.__module__
'sage.categories.crystals'
sage: g = C.__iter__()
sage: g.next()
(-Lambda[0] + Lambda[2],)
sage: g.next()
(Lambda[0] - Lambda[1] + delta,)
sage: g.next()
(Lambda[1] - Lambda[2] + delta,)
sage: g.next()
(-Lambda[0] + Lambda[2] + delta,)
sage: g.next()
(Lambda[1] - Lambda[2],)
sage: sorted(C.__iter__(index_set=[1,2]), key=str)
[(-Lambda[0] + Lambda[2],),
(Lambda[0] - Lambda[1],),
(Lambda[1] - Lambda[2],)]
sage: sorted(C.__iter__(max_depth=1), key=str)
[(-Lambda[0] + Lambda[2],),
(Lambda[0] - Lambda[1] + delta,),
(Lambda[1] - Lambda[2],)]
"""
if index_set is None:
index_set = self.index_set()
if max_depth < float('inf'):
from sage.combinat.backtrack import TransitiveIdealGraded
return TransitiveIdealGraded(lambda x: [x.f(i) for i in index_set]
+ [x.e(i) for i in index_set],
self.module_generators, max_depth).__iter__()
from sage.combinat.backtrack import TransitiveIdeal
return TransitiveIdeal(lambda x: [x.f(i) for i in index_set]
+ [x.e(i) for i in index_set],
self.module_generators).__iter__()
def set(self):
r"""
Naive algorithm to give a set with all the elements of the conjugacy
class.
.. TODO::
Implement a non-naive algorithm, cf. for instance
G. Butler: "An Inductive Schema for Computing Conjugacy Classes
in Permutation Groups", Math. of Comp. Vol. 62, No. 205 (1994)
EXAMPLES:
Groups of permutations::
sage: G = SymmetricGroup(3)
sage: g = G((1,2))
sage: C = ConjugacyClass(G,g)
sage: S = [(2,3), (1,2), (1,3)]
sage: C.set() == Set(G(x) for x in S)
True
Groups of matrices over finite fields::
sage: F = GF(5)
sage: gens = [matrix(F,2,[1,2, -1, 1]), matrix(F,2, [1,1, 0,1])]
sage: H = MatrixGroup(gens)
sage: h = H(matrix(F,2,[1,2, -1, 1]))
sage: C = ConjugacyClass(H,h)
sage: S = [[[3, 2], [2, 4]], [[0, 1], [2, 2]], [[3, 4], [1, 4]],\
[[0, 3], [4, 2]], [[1, 2], [4, 1]], [[2, 1], [2, 0]],\
[[4, 1], [4, 3]], [[4, 4], [1, 3]], [[2, 4], [3, 0]],\
[[1, 4], [2, 1]], [[3, 3], [3, 4]], [[2, 3], [4, 0]],\
[[0, 2], [1, 2]], [[1, 3], [1, 1]], [[4, 3], [3, 3]],\
[[4, 2], [2, 3]], [[0, 4], [3, 2]], [[1, 1], [3, 1]],\
[[2, 2], [1, 0]], [[3, 1], [4, 4]]]
sage: C.set() == Set(H(x) for x in S)
True
"""
from sage.sets.set import Set
from sage.combinat.backtrack import TransitiveIdeal
if self._parent.is_finite():
g = self._representative
G = self._parent
gens = G.gens()
return Set(x for x in TransitiveIdeal(
lambda y: [c * y * c**-1 for c in gens], [g]))
else:
raise NotImplementedError(
"Listing the elements of conjugacy classes is not implemented for infinite groups!"
)
def __iter__(self):
"""
Returns an iterator over the elements of ``self``.
EXAMPLES::
sage: S = FiniteSemigroups().example(alphabet=('x','y'))
sage: it = S.__iter__()
sage: list(it)
['y', 'x', 'xy', 'yx']
"""
from sage.combinat.backtrack import TransitiveIdeal
return TransitiveIdeal(self.succ_generators(side = "right"), self.semigroup_generators()).__iter__()
def positive_roots(self):
r"""
Returns the positive roots of self.
EXAMPLES::
sage: L = RootSystem(['A',3]).root_lattice()
sage: sorted(L.positive_roots())
[alpha[1], alpha[1] + alpha[2], alpha[1] + alpha[2] + alpha[3], alpha[2], alpha[2] + alpha[3], alpha[3]]
Algorithm: generate them from the simple roots by applying
successive reflections toward the positive chamber.
"""
assert self.cartan_type().is_finite()
return TransitiveIdeal(attrcall('pred'), self.simple_roots())
def __iter__(self):
"""
Returns the iterator of ``self``.
EXAMPLES::
sage: KRT = crystals.TensorProductOfKirillovReshetikhinTableaux(['A', 3, 1], [[2,1], [1,1]])
sage: g = KRT.__iter__()
sage: g.next()
[[2], [3]] (X) [[1]]
sage: g.next()
[[2], [4]] (X) [[1]]
"""
index_set = self._cartan_type.classical().index_set()
from sage.combinat.backtrack import TransitiveIdeal
return TransitiveIdeal(lambda x: [x.f(i) for i in index_set],
self.module_generators).__iter__()
def __iter__(self):
r"""
Return an iterator over the elements of ``self``.
This brute force implementation recursively multiplies
together the distinguished semigroup generators.
.. SEEALSO:: :meth:`semigroup_generators`
EXAMPLES::
sage: S = FiniteSemigroups().example(alphabet=('x','y'))
sage: it = S.__iter__()
sage: list(it)
['y', 'x', 'xy', 'yx']
"""
from sage.combinat.backtrack import TransitiveIdeal
return TransitiveIdeal(self.succ_generators(side = "right"), self.semigroup_generators()).__iter__()
def smaller(self):
r"""
Returns the elements in the orbit of self which are
smaller than self in the weak order.
EXAMPLES::
sage: L = RootSystem(['A',3]).ambient_lattice()
sage: e = L.basis()
sage: e[2].smaller()
[(0, 0, 1, 0), (0, 1, 0, 0), (1, 0, 0, 0)]
sage: len(L.rho().smaller())
1
sage: len((-L.rho()).smaller())
24
sage: sorted([len(x.smaller()) for x in L.rho().orbit()])
[1, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 5, 5, 6, 6, 6, 8, 8, 8, 8, 12, 12, 12, 24]
"""
return [x for x in TransitiveIdeal(attrcall('pred'), [self])]
def ideal(self, gens, side="twosided"):
r"""
Return the ``side``-sided ideal generated by ``gens``.
This brute force implementation recursively multiplies the
elements of ``gens`` by the distinguished generators of
this semigroup.
.. SEEALSO:: :meth:`semigroup_generators`
INPUT::
- ``gens``: a list (or iterable) of elements of ``self``
- ``side``: [default: "twosided"] "left", "right" or "twosided"
EXAMPLES::
sage: S = FiniteSemigroups().example()
sage: list(S.ideal([S('cab')], side="left"))
['cab', 'dcab', 'adcb', 'acb', 'bdca', 'bca', 'abdc',
'cadb', 'acdb', 'bacd', 'abcd', 'cbad', 'abc', 'acbd',
'dbac', 'dabc', 'cbda', 'bcad', 'cabd', 'dcba',
'bdac', 'cba', 'badc', 'bac', 'cdab', 'dacb', 'dbca',
'cdba', 'adbc', 'bcda']
sage: list(S.ideal([S('cab')], side="right"))
['cab', 'cabd']
sage: list(S.ideal([S('cab')], side="twosided"))
['cab', 'dcab', 'acb', 'adcb', 'acbd', 'bdca', 'bca',
'cabd', 'abdc', 'cadb', 'acdb', 'bacd', 'abcd', 'cbad',
'abc', 'dbac', 'dabc', 'cbda', 'bcad', 'dcba', 'bdac',
'cba', 'cdab', 'bac', 'badc', 'dacb', 'dbca', 'cdba',
'adbc', 'bcda']
sage: list(S.ideal([S('cab')]))
['cab', 'dcab', 'acb', 'adcb', 'acbd', 'bdca', 'bca',
'cabd', 'abdc', 'cadb', 'acdb', 'bacd', 'abcd', 'cbad',
'abc', 'dbac', 'dabc', 'cbda', 'bcad', 'dcba', 'bdac',
'cba', 'cdab', 'bac', 'badc', 'dacb', 'dbca', 'cdba',
'adbc', 'bcda']
"""
from sage.combinat.backtrack import TransitiveIdeal
return TransitiveIdeal(self.succ_generators(side = side), gens)
def elements(self):
r"""
Returns the elements of ``self``
Those are constructed as the elements below the maximal
elements of ``self`` in Bruhat order.
OUTPUT: a :class:`TransitiveIdeal` object
EXAMPLES::
sage: PF = WeylGroup(['A',3]).pieri_factors()
sage: [w.reduced_word() for w in PF.elements()]
[[3, 2, 1], [2, 1], [1], [], [3, 1], [3], [3, 2], [2]]
..seealso:: :meth:`maximal_elements`
TODO: possibly remove this method and instead have this class
inherit from :class:`TransitiveIdeal`.
"""
return TransitiveIdeal(attrcall('bruhat_lower_covers'), self.maximal_elements())
def cluster(self, pt=None):
r"""
Return an iterator over the open cluster containing the point pt.
INPUT:
- ``pt`` - tuple, point in Z^d. If None, pt=zero is considered.
EXAMPLES:
sage: from slabbe import BondPercolationSample
sage: S = BondPercolationSample(0.5)
sage: it = S.cluster()
sage: next(it)
(0, 0)
"""
if pt is None:
pt = self.zero()
generators = [pt]
return iter(TransitiveIdeal(self.children, generators))
def ideal(self, gens, side="twosided"):
r"""
Returns the ``side``-sided ideal generated by ``gens``.
INPUT::
- ``gens``: a list (or iterable) of elements of ``self``
- ``side``: [default: "twosided"] "left", "right" or "twosided"
EXAMPLES::
sage: S = FiniteSemigroups().example()
sage: list(S.ideal([S('cab')], side="left"))
['cab', 'dcab', 'adcb', 'acb', 'bdca', 'bca', 'abdc',
'cadb', 'acdb', 'bacd', 'abcd', 'cbad', 'abc', 'acbd',
'dbac', 'dabc', 'cbda', 'bcad', 'cabd', 'dcba',
'bdac', 'cba', 'badc', 'bac', 'cdab', 'dacb', 'dbca',
'cdba', 'adbc', 'bcda']
sage: list(S.ideal([S('cab')], side="right"))
['cab', 'cabd']
sage: list(S.ideal([S('cab')], side="twosided"))
['cab', 'dcab', 'acb', 'adcb', 'acbd', 'bdca', 'bca',
'cabd', 'abdc', 'cadb', 'acdb', 'bacd', 'abcd', 'cbad',
'abc', 'dbac', 'dabc', 'cbda', 'bcad', 'dcba', 'bdac',
'cba', 'cdab', 'bac', 'badc', 'dacb', 'dbca', 'cdba',
'adbc', 'bcda']
sage: list(S.ideal([S('cab')]))
['cab', 'dcab', 'acb', 'adcb', 'acbd', 'bdca', 'bca',
'cabd', 'abdc', 'cadb', 'acdb', 'bacd', 'abcd', 'cbad',
'abc', 'dbac', 'dabc', 'cbda', 'bcad', 'dcba', 'bdac',
'cba', 'cdab', 'bac', 'badc', 'dacb', 'dbca', 'cdba',
'adbc', 'bcda']
"""
from sage.combinat.backtrack import TransitiveIdeal
return TransitiveIdeal(self.succ_generators(side=side), gens)
def orbit(self):
r"""
The orbit of self under the action of the Weyl group
EXAMPLES::
`\rho` is a regular element whose orbit is in bijection with the Weyl group.
In particular, it as 6 elements for the symmetric group `S_3`::
sage: L = RootSystem(["A", 2]).ambient_lattice()
sage: sorted(L.rho().orbit()) # the output order is not specified
[(1, 2, 0), (1, 0, 2), (2, 1, 0), (2, 0, 1), (0, 1, 2), (0, 2, 1)]
sage: L = RootSystem(["A", 3]).weight_lattice()
sage: len(L.rho().orbit())
24
sage: len(L.fundamental_weights()[1].orbit())
4
sage: len(L.fundamental_weights()[2].orbit())
6
"""
return [
x for x in TransitiveIdeal(attrcall('simple_reflections'), [self])
]
def __iter__(self):
from sage.combinat.backtrack import TransitiveIdeal
return TransitiveIdeal(self.succ_generators(side="right"),
[self.one()]).__iter__()
def __iter__(self, index_set=None, max_depth=float('inf')):
"""
Returns the iterator of ``self``.
INPUT:
- ``index_set`` -- (Default: ``None``) The index set; if ``None``
then use the index set of the crystal
- ``max_depth`` -- (Default: infinity) The maximum depth to build
EXAMPLES::
sage: C = CrystalOfLSPaths(['A',2,1],[-1,0,1])
sage: C.__iter__.__module__
'sage.categories.crystals'
sage: g = C.__iter__()
sage: g.next()
(-Lambda[0] + Lambda[2],)
sage: g.next()
(Lambda[0] - Lambda[1] + delta,)
sage: g.next()
(Lambda[1] - Lambda[2] + delta,)
sage: g.next()
(Lambda[1] - Lambda[2],)
sage: g.next()
(Lambda[0] - Lambda[1],)
sage: h = C.__iter__(index_set=[1,2])
sage: h.next()
(-Lambda[0] + Lambda[2],)
sage: h.next()
(Lambda[1] - Lambda[2],)
sage: h.next()
(Lambda[0] - Lambda[1],)
sage: h.next()
Traceback (most recent call last):
...
StopIteration
sage: g = C.__iter__(max_depth=1)
sage: g.next()
(-Lambda[0] + Lambda[2],)
sage: g.next()
(Lambda[1] - Lambda[2],)
sage: g.next()
(Lambda[0] - Lambda[1] + delta,)
sage: h.next()
Traceback (most recent call last):
...
StopIteration
"""
if index_set is None:
index_set = self.index_set()
if max_depth < float('inf'):
from sage.combinat.backtrack import TransitiveIdealGraded
return TransitiveIdealGraded(lambda x: [x.f(i) for i in index_set]
+ [x.e(i) for i in index_set],
self.module_generators, max_depth).__iter__()
from sage.combinat.backtrack import TransitiveIdeal
return TransitiveIdeal(lambda x: [x.f(i) for i in index_set]
+ [x.e(i) for i in index_set],
self.module_generators).__iter__()
