From: Michael Orlitzky Date: Tue, 30 Jul 2019 22:17:16 +0000 (-0400) Subject: WIP: switch away from the algebra base class and use CombinatorialFreeModule. X-Git-Url: https://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=9c35b8d70e384cd98b8ec7eb7a84cf84db1d1137;p=sage.d.git WIP: switch away from the algebra base class and use CombinatorialFreeModule. --- diff --git a/mjo/eja/eja_algebra.py b/mjo/eja/eja_algebra.py index 362b03a..5e9c07c 100644 --- a/mjo/eja/eja_algebra.py +++ b/mjo/eja/eja_algebra.py @@ -5,9 +5,10 @@ are used in optimization, and have some additional nice methods beyond what can be supported in a general Jordan Algebra. """ -from sage.algebras.finite_dimensional_algebras.finite_dimensional_algebra import FiniteDimensionalAlgebra +#from sage.algebras.finite_dimensional_algebras.finite_dimensional_algebra import FiniteDimensionalAlgebra from sage.algebras.quatalg.quaternion_algebra import QuaternionAlgebra from sage.categories.finite_dimensional_algebras_with_basis import FiniteDimensionalAlgebrasWithBasis +from sage.combinat.free_module import CombinatorialFreeModule from sage.matrix.constructor import matrix from sage.misc.cachefunc import cached_method from sage.misc.prandom import choice @@ -20,50 +21,14 @@ from sage.structure.element import is_Matrix from sage.structure.category_object import normalize_names from mjo.eja.eja_element import FiniteDimensionalEuclideanJordanAlgebraElement -from mjo.eja.eja_utils import _vec2mat, _mat2vec - -class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): - @staticmethod - def __classcall_private__(cls, - field, - mult_table, - rank, - names='e', - assume_associative=False, - category=None, - natural_basis=None): - n = len(mult_table) - mult_table = [b.base_extend(field) for b in mult_table] - for b in mult_table: - b.set_immutable() - if not (is_Matrix(b) and b.dimensions() == (n, n)): - raise ValueError("input is not a multiplication table") - mult_table = tuple(mult_table) - - cat = FiniteDimensionalAlgebrasWithBasis(field) - cat.or_subcategory(category) - if assume_associative: - cat = cat.Associative() - - names = normalize_names(n, names) - - fda = super(FiniteDimensionalEuclideanJordanAlgebra, cls) - return fda.__classcall__(cls, - field, - mult_table, - rank, - assume_associative=assume_associative, - names=names, - category=cat, - natural_basis=natural_basis) - +from mjo.eja.eja_utils import _mat2vec +class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule): def __init__(self, field, mult_table, rank, - names='e', - assume_associative=False, + prefix='e', category=None, natural_basis=None): """ @@ -86,11 +51,14 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): self._rank = rank self._natural_basis = natural_basis self._multiplication_table = mult_table + if category is None: + category = FiniteDimensionalAlgebrasWithBasis(field).Unital() fda = super(FiniteDimensionalEuclideanJordanAlgebra, self) fda.__init__(field, - mult_table, - names=names, + range(len(mult_table)), + prefix=prefix, category=category) + self.print_options(bracket='') def _repr_(self): @@ -111,9 +79,15 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): Euclidean Jordan algebra of degree 3 over Real Double Field """ + # TODO: change this to say "dimension" and fix all the tests. fmt = "Euclidean Jordan algebra of degree {} over {}" - return fmt.format(self.degree(), self.base_ring()) + return fmt.format(self.dimension(), self.base_ring()) + def product_on_basis(self, i, j): + ei = self.basis()[i] + ej = self.basis()[j] + Lei = self._multiplication_table[i] + return self.from_vector(Lei*ej.to_vector()) def _a_regular_element(self): """ @@ -153,7 +127,7 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): """ z = self._a_regular_element() V = self.vector_space() - V1 = V.span_of_basis( (z**k).vector() for k in range(self.rank()) ) + V1 = V.span_of_basis( (z**k).to_vector() for k in range(self.rank()) ) b = (V1.basis() + V1.complement().basis()) return V.span_of_basis(b) @@ -205,11 +179,12 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): n = self.dimension() # Construct a new algebra over a multivariate polynomial ring... - names = ['X' + str(i) for i in range(1,n+1)] + names = tuple('X' + str(i) for i in range(1,n+1)) R = PolynomialRing(self.base_ring(), names) - J = FiniteDimensionalEuclideanJordanAlgebra(R, - self._multiplication_table, - r) + J = FiniteDimensionalEuclideanJordanAlgebra( + R, + tuple(self._multiplication_table), + r) idmat = matrix.identity(J.base_ring(), n) @@ -235,13 +210,13 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): # Handle the zeroth power separately, because computing # the unit element in J is mathematically suspect. - x0 = W.coordinates(self.one().vector()) - l1 = [ matrix.column(x0) ] - l1 += [ matrix.column(W.coordinates((x**k).vector())) + x0 = W.coordinate_vector(self.one().to_vector()) + l1 = [ x0.column() ] + l1 += [ W.coordinate_vector((x**k).to_vector()).column() for k in range(1,r) ] l2 = [idmat.column(k-1).column() for k in range(r+1, n+1)] A_of_x = matrix.block(R, 1, n, (l1 + l2)) - xr = W.coordinates((x**r).vector()) + xr = W.coordinate_vector((x**r).to_vector()) return (A_of_x, x, xr, A_of_x.det()) @@ -271,7 +246,7 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): sage: J = JordanSpinEJA(3) sage: p = J.characteristic_polynomial(); p X1^2 - X2^2 - X3^2 + (-2*t)*X1 + t^2 - sage: xvec = J.one().vector() + sage: xvec = J.one().to_vector() sage: p(*xvec) t^2 - 2*t + 1 @@ -359,7 +334,7 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): sage: J = RealSymmetricEJA(2) sage: J.basis() - Family (e0, e1, e2) + Finite family {0: e0, 1: e1, 2: e2} sage: J.natural_basis() ( [1 0] [0 1] [0 0] @@ -370,7 +345,7 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): sage: J = JordanSpinEJA(2) sage: J.basis() - Family (e0, e1) + Finite family {0: e0, 1: e1} sage: J.natural_basis() ( [1] [0] @@ -379,7 +354,7 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): """ if self._natural_basis is None: - return tuple( b.vector().column() for b in self.basis() ) + return tuple( b.to_vector().column() for b in self.basis() ) else: return self._natural_basis @@ -442,7 +417,7 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): # Now if there's an identity element in the algebra, this should work. coeffs = A.solve_right(b) - return self.linear_combination(zip(coeffs,self.gens())) + return self.linear_combination(zip(self.gens(), coeffs)) def rank(self): @@ -520,7 +495,7 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra): Vector space of dimension 3 over Rational Field """ - return self.zero().vector().parent().ambient_vector_space() + return self.zero().to_vector().parent().ambient_vector_space() Element = FiniteDimensionalEuclideanJordanAlgebraElement @@ -559,18 +534,17 @@ class RealCartesianProductEJA(FiniteDimensionalEuclideanJordanAlgebra): e2 """ - @staticmethod - def __classcall_private__(cls, n, field=QQ): - # The FiniteDimensionalAlgebra constructor takes a list of - # matrices, the ith representing right multiplication by the ith - # basis element in the vector space. So if e_1 = (1,0,0), then - # right (Hadamard) multiplication of x by e_1 picks out the first + def __init__(self, n, field=QQ): + # The superclass constructor takes a list of matrices, the ith + # representing right multiplication by the ith basis element + # in the vector space. So if e_1 = (1,0,0), then right + # (Hadamard) multiplication of x by e_1 picks out the first # component of x; and likewise for the ith basis element e_i. Qs = [ matrix(field, n, n, lambda k,j: 1*(k == j == i)) for i in xrange(n) ] - fdeja = super(RealCartesianProductEJA, cls) - return fdeja.__classcall_private__(cls, field, Qs, rank=n) + fdeja = super(RealCartesianProductEJA, self) + return fdeja.__init__(field, Qs, rank=n) def inner_product(self, x, y): return _usual_ip(x,y) @@ -755,30 +729,21 @@ def _multiplication_table_from_matrix_basis(basis): dimension = basis[0].nrows() V = VectorSpace(field, dimension**2) - W = V.span( _mat2vec(s) for s in basis ) - - # Taking the span above reorders our basis (thanks, jerk!) so we - # need to put our "matrix basis" in the same order as the - # (reordered) vector basis. - S = tuple( _vec2mat(b) for b in W.basis() ) + W = V.span_of_basis( _mat2vec(s) for s in basis ) Qs = [] - for s in S: + for s in basis: # Brute force the multiplication-by-s matrix by looping # through all elements of the basis and doing the computation - # to find out what the corresponding row should be. BEWARE: - # these multiplication tables won't be symmetric! It therefore - # becomes REALLY IMPORTANT that the underlying algebra - # constructor uses ROW vectors and not COLUMN vectors. That's - # why we're computing rows here and not columns. - Q_rows = [] - for t in S: - this_row = _mat2vec((s*t + t*s)/2) - Q_rows.append(W.coordinates(this_row)) - Q = matrix(field, W.dimension(), Q_rows) + # to find out what the corresponding row should be. + Q_cols = [] + for t in basis: + this_col = _mat2vec((s*t + t*s)/2) + Q_cols.append(W.coordinates(this_col)) + Q = matrix.column(field, W.dimension(), Q_cols) Qs.append(Q) - return (Qs, S) + return Qs def _embed_complex_matrix(M): @@ -1009,7 +974,7 @@ def _unembed_quaternion_matrix(M): # The usual inner product on R^n. def _usual_ip(x,y): - return x.vector().inner_product(y.vector()) + return x.to_vector().inner_product(y.to_vector()) # The inner product used for the real symmetric simple EJA. # We keep it as a separate function because e.g. the complex @@ -1068,17 +1033,15 @@ class RealSymmetricEJA(FiniteDimensionalEuclideanJordanAlgebra): True """ - @staticmethod - def __classcall_private__(cls, n, field=QQ): + def __init__(self, n, field=QQ): S = _real_symmetric_basis(n, field=field) - (Qs, T) = _multiplication_table_from_matrix_basis(S) + Qs = _multiplication_table_from_matrix_basis(S) - fdeja = super(RealSymmetricEJA, cls) - return fdeja.__classcall_private__(cls, - field, - Qs, - rank=n, - natural_basis=T) + fdeja = super(RealSymmetricEJA, self) + return fdeja.__init__(field, + Qs, + rank=n, + natural_basis=S) def inner_product(self, x, y): return _matrix_ip(x,y) @@ -1122,17 +1085,16 @@ class ComplexHermitianEJA(FiniteDimensionalEuclideanJordanAlgebra): True """ - @staticmethod - def __classcall_private__(cls, n, field=QQ): + def __init__(self, n, field=QQ): S = _complex_hermitian_basis(n) - (Qs, T) = _multiplication_table_from_matrix_basis(S) + Qs = _multiplication_table_from_matrix_basis(S) + + fdeja = super(ComplexHermitianEJA, self) + return fdeja.__init__(field, + Qs, + rank=n, + natural_basis=S) - fdeja = super(ComplexHermitianEJA, cls) - return fdeja.__classcall_private__(cls, - field, - Qs, - rank=n, - natural_basis=T) def inner_product(self, x, y): # Since a+bi on the diagonal is represented as @@ -1183,17 +1145,15 @@ class QuaternionHermitianEJA(FiniteDimensionalEuclideanJordanAlgebra): True """ - @staticmethod - def __classcall_private__(cls, n, field=QQ): + def __init__(self, n, field=QQ): S = _quaternion_hermitian_basis(n) - (Qs, T) = _multiplication_table_from_matrix_basis(S) + Qs = _multiplication_table_from_matrix_basis(S) - fdeja = super(QuaternionHermitianEJA, cls) - return fdeja.__classcall_private__(cls, - field, - Qs, - rank=n, - natural_basis=T) + fdeja = super(QuaternionHermitianEJA, self) + return fdeja.__init__(field, + Qs, + rank=n, + natural_basis=S) def inner_product(self, x, y): # Since a+bi+cj+dk on the diagonal is represented as @@ -1241,8 +1201,7 @@ class JordanSpinEJA(FiniteDimensionalEuclideanJordanAlgebra): 0 """ - @staticmethod - def __classcall_private__(cls, n, field=QQ): + def __init__(self, n, field=QQ): Qs = [] id_matrix = matrix.identity(field, n) for i in xrange(n): @@ -1259,8 +1218,8 @@ class JordanSpinEJA(FiniteDimensionalEuclideanJordanAlgebra): # The rank of the spin algebra is two, unless we're in a # one-dimensional ambient space (because the rank is bounded by # the ambient dimension). - fdeja = super(JordanSpinEJA, cls) - return fdeja.__classcall_private__(cls, field, Qs, rank=min(n,2)) + fdeja = super(JordanSpinEJA, self) + return fdeja.__init__(field, Qs, rank=min(n,2)) def inner_product(self, x, y): return _usual_ip(x,y) diff --git a/mjo/eja/eja_element.py b/mjo/eja/eja_element.py index 00a15a1..107603c 100644 --- a/mjo/eja/eja_element.py +++ b/mjo/eja/eja_element.py @@ -1,6 +1,6 @@ -from sage.algebras.finite_dimensional_algebras.finite_dimensional_algebra_element import FiniteDimensionalAlgebraElement from sage.matrix.constructor import matrix from sage.modules.free_module import VectorSpace +from sage.modules.with_basis.indexed_element import IndexedFreeModuleElement # TODO: make this unnecessary somehow. from sage.misc.lazy_import import lazy_import @@ -10,7 +10,7 @@ lazy_import('mjo.eja.eja_subalgebra', from mjo.eja.eja_operator import FiniteDimensionalEuclideanJordanAlgebraOperator from mjo.eja.eja_utils import _mat2vec -class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraElement): +class FiniteDimensionalEuclideanJordanAlgebraElement(IndexedFreeModuleElement): """ An element of a Euclidean Jordan algebra. """ @@ -25,7 +25,7 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle dir(self.__class__) ) - def __init__(self, A, elt=None): + def __init__(self, A, elt): """ SETUP:: @@ -60,7 +60,7 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle sage: set_random_seed() sage: J = random_eja() sage: v = J.vector_space().random_element() - sage: J(v).vector() == v + sage: J(v).to_vector() == v True """ @@ -75,8 +75,9 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle # already fits into the algebra, but also happens to live # in the parent's "natural ambient space" (this happens with # vectors in R^n). + ifme = super(FiniteDimensionalEuclideanJordanAlgebraElement, self) try: - FiniteDimensionalAlgebraElement.__init__(self, A, elt) + ifme.__init__(A, elt) except ValueError: natural_basis = A.natural_basis() if elt in natural_basis[0].matrix_space(): @@ -85,8 +86,9 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle # natural-basis coordinates ourselves. V = VectorSpace(elt.base_ring(), elt.nrows()**2) W = V.span( _mat2vec(s) for s in natural_basis ) - coords = W.coordinates(_mat2vec(elt)) - FiniteDimensionalAlgebraElement.__init__(self, A, coords) + coords = W.coordinate_vector(_mat2vec(elt)) + ifme.__init__(A, coords) + def __pow__(self, n): """ @@ -228,7 +230,7 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle """ p = self.parent().characteristic_polynomial() - return p(*self.vector()) + return p(*self.to_vector()) def inner_product(self, other): @@ -437,7 +439,7 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle # -1 to ensure that _charpoly_coeff(0) is really what # appears in front of t^{0} in the charpoly. However, # we want (-1)^r times THAT for the determinant. - return ((-1)**r)*p(*self.vector()) + return ((-1)**r)*p(*self.to_vector()) def inverse(self): @@ -465,7 +467,7 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle sage: x = J.random_element() sage: while not x.is_invertible(): ....: x = J.random_element() - sage: x_vec = x.vector() + sage: x_vec = x.to_vector() sage: x0 = x_vec[0] sage: x_bar = x_vec[1:] sage: coeff = ~(x0^2 - x_bar.inner_product(x_bar)) @@ -765,8 +767,8 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle sage: y = J.random_element() sage: while y == y.coefficient(0)*J.one(): ....: y = J.random_element() - sage: y0 = y.vector()[0] - sage: y_bar = y.vector()[1:] + sage: y0 = y.to_vector()[0] + sage: y_bar = y.to_vector()[1:] sage: actual = y.minimal_polynomial() sage: t = PolynomialRing(J.base_ring(),'t').gen(0) sage: expected = t^2 - 2*y0*t + (y0^2 - norm(y_bar)^2) @@ -783,7 +785,7 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle """ A = self.subalgebra_generated_by() - return A(self).operator().minimal_polynomial() + return A.element_class(A,self).operator().minimal_polynomial() @@ -837,7 +839,7 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle """ B = self.parent().natural_basis() W = B[0].matrix_space() - return W.linear_combination(zip(self.vector(), B)) + return W.linear_combination(zip(B,self.to_vector())) def operator(self): @@ -862,11 +864,10 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle """ P = self.parent() - fda_elt = FiniteDimensionalAlgebraElement(P, self) return FiniteDimensionalEuclideanJordanAlgebraOperator( P, P, - fda_elt.matrix().transpose() ) + self.to_matrix() ) def quadratic_representation(self, other=None): @@ -887,7 +888,7 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle sage: n = ZZ.random_element(1,10) sage: J = JordanSpinEJA(n) sage: x = J.random_element() - sage: x_vec = x.vector() + sage: x_vec = x.to_vector() sage: x0 = x_vec[0] sage: x_bar = x_vec[1:] sage: A = matrix(QQ, 1, [x_vec.inner_product(x_vec)]) @@ -1070,7 +1071,7 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle # Our FiniteDimensionalAlgebraElement superclass uses rows. u_next = u**(s+1) A = u_next.operator().matrix() - c = J(A.solve_right(u_next.vector())) + c = J(A.solve_right(u_next.to_vector())) # Now c is the idempotent we want, but it still lives in the subalgebra. return c.superalgebra_element() @@ -1116,7 +1117,7 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(FiniteDimensionalAlgebraEle # -1 to ensure that _charpoly_coeff(r-1) is really what # appears in front of t^{r-1} in the charpoly. However, # we want the negative of THAT for the trace. - return -p(*self.vector()) + return -p(*self.to_vector()) def trace_inner_product(self, other): diff --git a/mjo/eja/eja_operator.py b/mjo/eja/eja_operator.py index 1f10048..8973a95 100644 --- a/mjo/eja/eja_operator.py +++ b/mjo/eja/eja_operator.py @@ -46,14 +46,14 @@ class FiniteDimensionalEuclideanJordanAlgebraOperator(Map): EXAMPLES:: sage: J = JordanSpinEJA(3) - sage: x = J.linear_combination(zip(range(len(J.gens())), J.gens())) + sage: x = J.linear_combination(zip(J.gens(),range(len(J.gens())))) sage: id = identity_matrix(J.base_ring(), J.dimension()) sage: f = FiniteDimensionalEuclideanJordanAlgebraOperator(J,J,id) sage: f(x) == x True """ - return self.codomain()(self.matrix()*x.vector()) + return self.codomain().from_vector(self.matrix()*x.to_vector()) def _add_(self, other): diff --git a/mjo/eja/eja_subalgebra.py b/mjo/eja/eja_subalgebra.py index 5ac0a77..a774b98 100644 --- a/mjo/eja/eja_subalgebra.py +++ b/mjo/eja/eja_subalgebra.py @@ -1,49 +1,122 @@ from sage.matrix.constructor import matrix -from sage.structure.category_object import normalize_names from mjo.eja.eja_algebra import FiniteDimensionalEuclideanJordanAlgebra from mjo.eja.eja_element import FiniteDimensionalEuclideanJordanAlgebraElement -class FiniteDimensionalEuclideanJordanElementSubalgebra(FiniteDimensionalEuclideanJordanAlgebra): +class FiniteDimensionalEuclideanJordanElementSubalgebraElement(FiniteDimensionalEuclideanJordanAlgebraElement): """ - The subalgebra of an EJA generated by a single element. - SETUP:: - sage: from mjo.eja.eja_algebra import FiniteDimensionalEuclideanJordanAlgebra + sage: from mjo.eja.eja_algebra import random_eja + + TESTS:: + + The natural representation of an element in the subalgebra is + the same as its natural representation in the superalgebra:: + + sage: set_random_seed() + sage: A = random_eja().random_element().subalgebra_generated_by() + sage: y = A.random_element() + sage: actual = y.natural_representation() + sage: expected = y.superalgebra_element().natural_representation() + sage: actual == expected + True + + """ + def __init__(self, A, elt): + """ + SETUP:: + + sage: from mjo.eja.eja_algebra import RealSymmetricEJA + sage: from mjo.eja.eja_subalgebra import FiniteDimensionalEuclideanJordanElementSubalgebra + + EXAMPLES:: + + sage: J = RealSymmetricEJA(3) + sage: x = sum( i*J.gens()[i] for i in range(6) ) + sage: K = FiniteDimensionalEuclideanJordanElementSubalgebra(x) + sage: [ K.element_class(K,x^k) for k in range(J.rank()) ] + [f0, f1, f2] + + :: + + """ + if elt in A.superalgebra(): + # Try to convert a parent algebra element into a + # subalgebra element... + try: + coords = A.vector_space().coordinate_vector(elt.to_vector()) + elt = A.from_vector(coords).monomial_coefficients() + except AttributeError: + # Catches a missing method in elt.to_vector() + pass + + s = super(FiniteDimensionalEuclideanJordanElementSubalgebraElement, + self) + + s.__init__(A, elt) + + + def superalgebra_element(self): + """ + Return the object in our algebra's superalgebra that corresponds + to myself. + + SETUP:: + + sage: from mjo.eja.eja_algebra import (RealSymmetricEJA, + ....: random_eja) - TESTS: + EXAMPLES:: + + sage: J = RealSymmetricEJA(3) + sage: x = sum(J.gens()) + sage: x + e0 + e1 + e2 + e3 + e4 + e5 + sage: A = x.subalgebra_generated_by() + sage: A.element_class(A,x) + f1 + sage: A.element_class(A,x).superalgebra_element() + e0 + e1 + e2 + e3 + e4 + e5 + + TESTS: + + We can convert back and forth faithfully:: + + sage: set_random_seed() + sage: J = random_eja() + sage: x = J.random_element() + sage: A = x.subalgebra_generated_by() + sage: A.element_class(A,x).superalgebra_element() == x + True + sage: y = A.random_element() + sage: A.element_class(A,y.superalgebra_element()) == y + True + + """ + return self.parent().superalgebra().linear_combination( + zip(self.parent()._superalgebra_basis, self.to_vector()) ) - Ensure that non-clashing names are chosen:: - sage: m1 = matrix.identity(QQ,2) - sage: m2 = matrix(QQ, [[0,1], - ....: [1,0]]) - sage: J = FiniteDimensionalEuclideanJordanAlgebra(QQ, - ....: [m1,m2], - ....: 2, - ....: names='f') - sage: J.variable_names() - ('f0', 'f1') - sage: A = sum(J.gens()).subalgebra_generated_by() - sage: A.variable_names() - ('g0', 'g1') + +class FiniteDimensionalEuclideanJordanElementSubalgebra(FiniteDimensionalEuclideanJordanAlgebra): + """ + The subalgebra of an EJA generated by a single element. """ - @staticmethod - def __classcall_private__(cls, elt): + def __init__(self, elt): superalgebra = elt.parent() # First compute the vector subspace spanned by the powers of # the given element. V = superalgebra.vector_space() superalgebra_basis = [superalgebra.one()] - basis_vectors = [superalgebra.one().vector()] + basis_vectors = [superalgebra.one().to_vector()] W = V.span_of_basis(basis_vectors) for exponent in range(1, V.dimension()): new_power = elt**exponent - basis_vectors.append( new_power.vector() ) + basis_vectors.append( new_power.to_vector() ) try: W = V.span_of_basis(basis_vectors) superalgebra_basis.append( new_power ) @@ -58,7 +131,7 @@ class FiniteDimensionalEuclideanJordanElementSubalgebra(FiniteDimensionalEuclide # Now figure out the entries of the right-multiplication # matrix for the successive basis elements b0, b1,... of # that subspace. - F = superalgebra.base_ring() + field = superalgebra.base_ring() mult_table = [] for b_right in superalgebra_basis: b_right_rows = [] @@ -73,15 +146,18 @@ class FiniteDimensionalEuclideanJordanElementSubalgebra(FiniteDimensionalEuclide # Multiply in the original EJA, but then get the # coordinates from the subalgebra in terms of its # basis. - this_row = W.coordinates((b_left*b_right).vector()) + this_row = W.coordinates((b_left*b_right).to_vector()) b_right_rows.append(this_row) - b_right_matrix = matrix(F, b_right_rows) + b_right_matrix = matrix(field, b_right_rows) mult_table.append(b_right_matrix) for m in mult_table: m.set_immutable() mult_table = tuple(mult_table) + # TODO: We'll have to redo this and make it unique again... + prefix = 'f' + # The rank is the highest possible degree of a minimal # polynomial, and is bounded above by the dimension. We know # in this case that there's an element whose minimal @@ -90,60 +166,23 @@ class FiniteDimensionalEuclideanJordanElementSubalgebra(FiniteDimensionalEuclide # its rank too. rank = W.dimension() - # EJAs are power-associative, and this algebra is nothin but - # powers. - assume_associative=True - - # Figure out a non-conflicting set of names to use. - valid_names = ['f','g','h','a','b','c','d'] - name_idx = 0 - names = normalize_names(W.dimension(), valid_names[0]) - # This loops so long as the list of collisions is nonempty. - # Just crash if we run out of names without finding a set that - # don't conflict with the parent algebra. - while [y for y in names if y in superalgebra.variable_names()]: - name_idx += 1 - names = normalize_names(W.dimension(), valid_names[name_idx]) - - cat = superalgebra.category().Associative() + category = superalgebra.category().Associative() natural_basis = tuple( b.natural_representation() for b in superalgebra_basis ) - fdeja = super(FiniteDimensionalEuclideanJordanElementSubalgebra, cls) - return fdeja.__classcall__(cls, - F, - mult_table, - rank, - superalgebra_basis, - W, - assume_associative=assume_associative, - names=names, - category=cat, - natural_basis=natural_basis) - - def __init__(self, - field, - mult_table, - rank, - superalgebra_basis, - vector_space, - assume_associative=True, - names='f', - category=None, - natural_basis=None): - - self._superalgebra = superalgebra_basis[0].parent() - self._vector_space = vector_space + self._superalgebra = superalgebra + self._vector_space = W self._superalgebra_basis = superalgebra_basis + fdeja = super(FiniteDimensionalEuclideanJordanElementSubalgebra, self) - fdeja.__init__(field, - mult_table, - rank, - assume_associative=assume_associative, - names=names, - category=category, - natural_basis=natural_basis) + return fdeja.__init__(field, + mult_table, + rank, + prefix=prefix, + category=category, + natural_basis=natural_basis) + def superalgebra(self): @@ -171,106 +210,15 @@ class FiniteDimensionalEuclideanJordanElementSubalgebra(FiniteDimensionalEuclide [ 1 0 0 1 0 1] [ 0 1 2 3 4 5] [ 5 11 14 26 34 45] - sage: (x^0).vector() + sage: (x^0).to_vector() (1, 0, 0, 1, 0, 1) - sage: (x^1).vector() + sage: (x^1).to_vector() (0, 1, 2, 3, 4, 5) - sage: (x^2).vector() + sage: (x^2).to_vector() (5, 11, 14, 26, 34, 45) """ return self._vector_space - class Element(FiniteDimensionalEuclideanJordanAlgebraElement): - """ - - SETUP:: - - sage: from mjo.eja.eja_algebra import random_eja - - TESTS:: - - The natural representation of an element in the subalgebra is - the same as its natural representation in the superalgebra:: - - sage: set_random_seed() - sage: A = random_eja().random_element().subalgebra_generated_by() - sage: y = A.random_element() - sage: actual = y.natural_representation() - sage: expected = y.superalgebra_element().natural_representation() - sage: actual == expected - True - - """ - def __init__(self, A, elt=None): - """ - SETUP:: - - sage: from mjo.eja.eja_algebra import RealSymmetricEJA - sage: from mjo.eja.eja_subalgebra import FiniteDimensionalEuclideanJordanElementSubalgebra - - EXAMPLES:: - - sage: J = RealSymmetricEJA(3) - sage: x = sum( i*J.gens()[i] for i in range(6) ) - sage: K = FiniteDimensionalEuclideanJordanElementSubalgebra(x) - sage: [ K(x^k) for k in range(J.rank()) ] - [f0, f1, f2] - - :: - - """ - if elt in A.superalgebra(): - # Try to convert a parent algebra element into a - # subalgebra element... - try: - coords = A.vector_space().coordinates(elt.vector()) - elt = A(coords) - except AttributeError: - # Catches a missing method in elt.vector() - pass - - FiniteDimensionalEuclideanJordanAlgebraElement.__init__(self, - A, - elt) - - def superalgebra_element(self): - """ - Return the object in our algebra's superalgebra that corresponds - to myself. - - SETUP:: - - sage: from mjo.eja.eja_algebra import (RealSymmetricEJA, - ....: random_eja) - - EXAMPLES:: - - sage: J = RealSymmetricEJA(3) - sage: x = sum(J.gens()) - sage: x - e0 + e1 + e2 + e3 + e4 + e5 - sage: A = x.subalgebra_generated_by() - sage: A(x) - f1 - sage: A(x).superalgebra_element() - e0 + e1 + e2 + e3 + e4 + e5 - - TESTS: - - We can convert back and forth faithfully:: - - sage: set_random_seed() - sage: J = random_eja() - sage: x = J.random_element() - sage: A = x.subalgebra_generated_by() - sage: A(x).superalgebra_element() == x - True - sage: y = A.random_element() - sage: A(y.superalgebra_element()) == y - True - - """ - return self.parent().superalgebra().linear_combination( - zip(self.vector(), self.parent()._superalgebra_basis) ) + Element = FiniteDimensionalEuclideanJordanElementSubalgebraElement