X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=mjo%2Feja%2Feja_algebra.py;h=1302ca18bf9988f57048cdd9035e79212aa7ca3d;hb=858aa3653fd2e4ae8573f472cf3f0d698072c185;hp=7c8adc7400880b0c4a95f7d73dec6cd11113aec6;hpb=a4f0908c2216ff989161d33873102805d1c6aabd;p=sage.d.git diff --git a/mjo/eja/eja_algebra.py b/mjo/eja/eja_algebra.py index 7c8adc7..1302ca1 100644 --- a/mjo/eja/eja_algebra.py +++ b/mjo/eja/eja_algebra.py @@ -20,7 +20,9 @@ from itertools import repeat from sage.algebras.quatalg.quaternion_algebra import QuaternionAlgebra from sage.categories.magmatic_algebras import MagmaticAlgebras -from sage.combinat.free_module import CombinatorialFreeModule +from sage.categories.sets_cat import cartesian_product +from sage.combinat.free_module import (CombinatorialFreeModule, + CombinatorialFreeModule_CartesianProduct) from sage.matrix.constructor import matrix from sage.matrix.matrix_space import MatrixSpace from sage.misc.cachefunc import cached_method @@ -62,7 +64,8 @@ class FiniteDimensionalEJA(CombinatorialFreeModule): associative=False, check_field=True, check_axioms=True, - prefix='e'): + prefix='e', + category=None): if check_field: if not field.is_subring(RR): @@ -91,11 +94,12 @@ class FiniteDimensionalEJA(CombinatorialFreeModule): raise ValueError("inner-product is not commutative") - category = MagmaticAlgebras(field).FiniteDimensional() - category = category.WithBasis().Unital() - if associative: - # Element subalgebras can take advantage of this. - category = category.Associative() + if category is None: + category = MagmaticAlgebras(field).FiniteDimensional() + category = category.WithBasis().Unital() + if associative: + # Element subalgebras can take advantage of this. + category = category.Associative() # Call the superclass constructor so that we can use its from_vector() # method to build our multiplication table. @@ -687,7 +691,7 @@ class FiniteDimensionalEJA(CombinatorialFreeModule): Why implement this for non-matrix algebras? Avoiding special cases for the :class:`BilinearFormEJA` pays with simplicity in its own right. But mainly, we would like to be able to assume - that elements of a :class:`DirectSumEJA` can be displayed + that elements of a :class:`CartesianProductEJA` can be displayed nicely, without having to have special classes for direct sums one of whose components was a matrix algebra. @@ -1151,10 +1155,17 @@ class FiniteDimensionalEJA(CombinatorialFreeModule): # The theory says that only the first "r" coefficients are # nonzero, and they actually live in the original polynomial - # ring and not the fraction field. We negate them because - # in the actual characteristic polynomial, they get moved - # to the other side where x^r lives. - return -A_rref.solve_right(E*b).change_ring(R)[:r] + # ring and not the fraction field. We negate them because in + # the actual characteristic polynomial, they get moved to the + # other side where x^r lives. We don't bother to trim A_rref + # down to a square matrix and solve the resulting system, + # because the upper-left r-by-r portion of A_rref is + # guaranteed to be the identity matrix, so e.g. + # + # A_rref.solve_right(Y) + # + # would just be returning Y. + return (-E*b)[:r].change_ring(R) @cached_method def rank(self): @@ -1215,7 +1226,7 @@ class FiniteDimensionalEJA(CombinatorialFreeModule): sage: set_random_seed() # long time sage: J = random_eja() # long time - sage: caches = J.rank() # long time + sage: cached = J.rank() # long time sage: J.rank.clear_cache() # long time sage: J.rank() == cached # long time True @@ -2668,262 +2679,384 @@ class TrivialEJA(ConcreteEJA): return cls(**kwargs) -class DirectSumEJA(FiniteDimensionalEJA): +class CartesianProductEJA(CombinatorialFreeModule_CartesianProduct, + FiniteDimensionalEJA): r""" - The external (orthogonal) direct sum of two other Euclidean Jordan - algebras. Essentially the Cartesian product of its two factors. - Every Euclidean Jordan algebra decomposes into an orthogonal - direct sum of simple Euclidean Jordan algebras, so no generality - is lost by providing only this construction. + The external (orthogonal) direct sum of two or more Euclidean + Jordan algebras. Every Euclidean Jordan algebra decomposes into an + orthogonal direct sum of simple Euclidean Jordan algebras which is + then isometric to a Cartesian product, so no generality is lost by + providing only this construction. SETUP:: - sage: from mjo.eja.eja_algebra import (random_eja, + sage: from mjo.eja.eja_algebra import (CartesianProductEJA, ....: HadamardEJA, - ....: RealSymmetricEJA, - ....: DirectSumEJA) + ....: JordanSpinEJA, + ....: RealSymmetricEJA) - EXAMPLES:: + EXAMPLES: + + The Jordan product is inherited from our factors and implemented by + our CombinatorialFreeModule Cartesian product superclass:: + sage: set_random_seed() sage: J1 = HadamardEJA(2) - sage: J2 = RealSymmetricEJA(3) - sage: J = DirectSumEJA(J1,J2) - sage: J.dimension() - 8 - sage: J.rank() - 5 - sage: J.matrix_space() - The Cartesian product of (Full MatrixSpace of 2 by 1 dense matrices - over Algebraic Real Field, Full MatrixSpace of 3 by 3 dense matrices - over Algebraic Real Field) + sage: J2 = RealSymmetricEJA(2) + sage: J = cartesian_product([J1,J2]) + sage: x,y = J.random_elements(2) + sage: x*y in J + True + + The ability to retrieve the original factors is implemented by our + CombinatorialFreeModule Cartesian product superclass:: + + sage: J1 = HadamardEJA(2, field=QQ) + sage: J2 = JordanSpinEJA(3, field=QQ) + sage: J = cartesian_product([J1,J2]) + sage: J.cartesian_factors() + (Euclidean Jordan algebra of dimension 2 over Rational Field, + Euclidean Jordan algebra of dimension 3 over Rational Field) + + You can provide more than two factors:: + + sage: J1 = HadamardEJA(2) + sage: J2 = JordanSpinEJA(3) + sage: J3 = RealSymmetricEJA(3) + sage: cartesian_product([J1,J2,J3]) + Euclidean Jordan algebra of dimension 2 over Algebraic Real + Field (+) Euclidean Jordan algebra of dimension 3 over Algebraic + Real Field (+) Euclidean Jordan algebra of dimension 6 over + Algebraic Real Field TESTS: - The external direct sum construction is only valid when the two factors - have the same base ring; an error is raised otherwise:: + All factors must share the same base field:: - sage: set_random_seed() - sage: J1 = random_eja(field=AA) - sage: J2 = random_eja(field=QQ,orthonormalize=False) - sage: J = DirectSumEJA(J1,J2) + sage: J1 = HadamardEJA(2, field=QQ) + sage: J2 = RealSymmetricEJA(2) + sage: CartesianProductEJA((J1,J2)) Traceback (most recent call last): ... - ValueError: algebras must share the same base field + ValueError: all factors must share the same base field """ - def __init__(self, J1, J2, **kwargs): - if J1.base_ring() != J2.base_ring(): - raise ValueError("algebras must share the same base field") - field = J1.base_ring() - - M = J1.matrix_space().cartesian_product(J2.matrix_space()) - self._cartprod_algebra = J1.cartesian_product(J2) - - self._matrix_basis = tuple( [M((a,0)) for a in J1.matrix_basis()] + - [M((0,b)) for b in J2.matrix_basis()] ) - - n = len(self._matrix_basis) - self._sets = None - CombinatorialFreeModule.__init__( - self, - field, - range(n), - category=self._cartprod_algebra.category(), - bracket=False, - **kwargs) - self.rank.set_cache(J1.rank() + J2.rank()) + def __init__(self, modules, **kwargs): + CombinatorialFreeModule_CartesianProduct.__init__(self, modules) + field = modules[0].base_ring() + if not all( J.base_ring() == field for J in modules ): + raise ValueError("all factors must share the same base field") + + basis = tuple( b.to_vector().column() for b in self.basis() ) + + # Define jordan/inner products that operate on the basis. + def jordan_product(x_mat,y_mat): + x = self.from_vector(_mat2vec(x_mat)) + y = self.from_vector(_mat2vec(y_mat)) + return self.cartesian_jordan_product(x,y).to_vector().column() + + def inner_product(x_mat, y_mat): + x = self.from_vector(_mat2vec(x_mat)) + y = self.from_vector(_mat2vec(y_mat)) + return self.cartesian_inner_product(x,y) + + # Use whatever category the superclass came up with. Usually + # some join of the EJA and Cartesian product + # categories. There's no need to check the field since it + # already came from an EJA. Likewise the axioms are guaranteed + # to be satisfied. + FiniteDimensionalEJA.__init__(self, + basis, + jordan_product, + inner_product, + field=field, + check_field=False, + check_axioms=False, + category=self.category(), + **kwargs) + + self.rank.set_cache(sum(J.rank() for J in modules)) + @cached_method + def cartesian_projection(self, i): + r""" + SETUP:: + sage: from mjo.eja.eja_algebra import (random_eja, + ....: JordanSpinEJA, + ....: HadamardEJA, + ....: RealSymmetricEJA, + ....: ComplexHermitianEJA) + + EXAMPLES: + + The projection morphisms are Euclidean Jordan algebra + operators:: + + sage: J1 = HadamardEJA(2) + sage: J2 = RealSymmetricEJA(2) + sage: J = cartesian_product([J1,J2]) + sage: J.cartesian_projection(0) + Linear operator between finite-dimensional Euclidean Jordan + algebras represented by the matrix: + [1 0 0 0 0] + [0 1 0 0 0] + Domain: Euclidean Jordan algebra of dimension 2 over Algebraic + Real Field (+) Euclidean Jordan algebra of dimension 3 over + Algebraic Real Field + Codomain: Euclidean Jordan algebra of dimension 2 over Algebraic + Real Field + sage: J.cartesian_projection(1) + Linear operator between finite-dimensional Euclidean Jordan + algebras represented by the matrix: + [0 0 1 0 0] + [0 0 0 1 0] + [0 0 0 0 1] + Domain: Euclidean Jordan algebra of dimension 2 over Algebraic + Real Field (+) Euclidean Jordan algebra of dimension 3 over + Algebraic Real Field + Codomain: Euclidean Jordan algebra of dimension 3 over Algebraic + Real Field + + The projections work the way you'd expect on the vector + representation of an element:: + + sage: J1 = JordanSpinEJA(2) + sage: J2 = ComplexHermitianEJA(2) + sage: J = cartesian_product([J1,J2]) + sage: pi_left = J.cartesian_projection(0) + sage: pi_right = J.cartesian_projection(1) + sage: pi_left(J.one()).to_vector() + (1, 0) + sage: pi_right(J.one()).to_vector() + (1, 0, 0, 1) + sage: J.one().to_vector() + (1, 0, 1, 0, 0, 1) + + TESTS: + + The answer never changes:: + + sage: set_random_seed() + sage: J1 = random_eja() + sage: J2 = random_eja() + sage: J = cartesian_product([J1,J2]) + sage: P0 = J.cartesian_projection(0) + sage: P1 = J.cartesian_projection(0) + sage: P0 == P1 + True + + """ + Ji = self.cartesian_factors()[i] + # Requires the fix on Trac 31421/31422 to work! + Pi = super().cartesian_projection(i) + return FiniteDimensionalEJAOperator(self,Ji,Pi.matrix()) - def product(self,x,y): + @cached_method + def cartesian_embedding(self, i): r""" SETUP:: - sage: from mjo.eja.eja_algebra import (JordanSpinEJA, - ....: ComplexHermitianEJA, - ....: DirectSumEJA) + sage: from mjo.eja.eja_algebra import (random_eja, + ....: JordanSpinEJA, + ....: HadamardEJA, + ....: RealSymmetricEJA) - TESTS:: + EXAMPLES: + + The embedding morphisms are Euclidean Jordan algebra + operators:: + + sage: J1 = HadamardEJA(2) + sage: J2 = RealSymmetricEJA(2) + sage: J = cartesian_product([J1,J2]) + sage: J.cartesian_embedding(0) + Linear operator between finite-dimensional Euclidean Jordan + algebras represented by the matrix: + [1 0] + [0 1] + [0 0] + [0 0] + [0 0] + Domain: Euclidean Jordan algebra of dimension 2 over + Algebraic Real Field + Codomain: Euclidean Jordan algebra of dimension 2 over + Algebraic Real Field (+) Euclidean Jordan algebra of + dimension 3 over Algebraic Real Field + sage: J.cartesian_embedding(1) + Linear operator between finite-dimensional Euclidean Jordan + algebras represented by the matrix: + [0 0 0] + [0 0 0] + [1 0 0] + [0 1 0] + [0 0 1] + Domain: Euclidean Jordan algebra of dimension 3 over + Algebraic Real Field + Codomain: Euclidean Jordan algebra of dimension 2 over + Algebraic Real Field (+) Euclidean Jordan algebra of + dimension 3 over Algebraic Real Field + + The embeddings work the way you'd expect on the vector + representation of an element:: + + sage: J1 = JordanSpinEJA(3) + sage: J2 = RealSymmetricEJA(2) + sage: J = cartesian_product([J1,J2]) + sage: iota_left = J.cartesian_embedding(0) + sage: iota_right = J.cartesian_embedding(1) + sage: iota_left(J1.zero()) == J.zero() + True + sage: iota_right(J2.zero()) == J.zero() + True + sage: J1.one().to_vector() + (1, 0, 0) + sage: iota_left(J1.one()).to_vector() + (1, 0, 0, 0, 0, 0) + sage: J2.one().to_vector() + (1, 0, 1) + sage: iota_right(J2.one()).to_vector() + (0, 0, 0, 1, 0, 1) + sage: J.one().to_vector() + (1, 0, 0, 1, 0, 1) + + TESTS: + + The answer never changes:: sage: set_random_seed() - sage: J1 = JordanSpinEJA(3, field=QQ) - sage: J2 = ComplexHermitianEJA(2, field=QQ, orthonormalize=False) - sage: J = DirectSumEJA(J1,J2) - sage: J.random_element()*J.random_element() in J + sage: J1 = random_eja() + sage: J2 = random_eja() + sage: J = cartesian_product([J1,J2]) + sage: E0 = J.cartesian_embedding(0) + sage: E1 = J.cartesian_embedding(0) + sage: E0 == E1 + True + + Composing a projection with the corresponding inclusion should + produce the identity map, and mismatching them should produce + the zero map:: + + sage: set_random_seed() + sage: J1 = random_eja() + sage: J2 = random_eja() + sage: J = cartesian_product([J1,J2]) + sage: iota_left = J.cartesian_embedding(0) + sage: iota_right = J.cartesian_embedding(1) + sage: pi_left = J.cartesian_projection(0) + sage: pi_right = J.cartesian_projection(1) + sage: pi_left*iota_left == J1.one().operator() + True + sage: pi_right*iota_right == J2.one().operator() + True + sage: (pi_left*iota_right).is_zero() + True + sage: (pi_right*iota_left).is_zero() True """ - xv = self._cartprod_algebra.from_vector(x.to_vector()) - yv = self._cartprod_algebra.from_vector(y.to_vector()) - return self.from_vector((xv*yv).to_vector()) + Ji = self.cartesian_factors()[i] + # Requires the fix on Trac 31421/31422 to work! + Ei = super().cartesian_embedding(i) + return FiniteDimensionalEJAOperator(Ji,self,Ei.matrix()) - def cartesian_factors(self): + def cartesian_jordan_product(self, x, y): r""" - Return the pair of this algebra's factors. + The componentwise Jordan product. + + We project ``x`` and ``y`` onto our factors, and add up the + Jordan products from the subalgebras. This may still be useful + after (if) the default Jordan product in the Cartesian product + algebra is overridden. SETUP:: sage: from mjo.eja.eja_algebra import (HadamardEJA, - ....: JordanSpinEJA, - ....: DirectSumEJA) + ....: JordanSpinEJA) - EXAMPLES:: + EXAMPLE:: + + sage: J1 = HadamardEJA(3) + sage: J2 = JordanSpinEJA(3) + sage: J = cartesian_product([J1,J2]) + sage: x1 = J1.from_vector(vector(QQ,(1,2,1))) + sage: y1 = J1.from_vector(vector(QQ,(1,0,2))) + sage: x2 = J2.from_vector(vector(QQ,(1,2,3))) + sage: y2 = J2.from_vector(vector(QQ,(1,1,1))) + sage: z1 = J.from_vector(vector(QQ,(1,2,1,1,2,3))) + sage: z2 = J.from_vector(vector(QQ,(1,0,2,1,1,1))) + sage: (x1*y1).to_vector() + (1, 0, 2) + sage: (x2*y2).to_vector() + (6, 3, 4) + sage: J.cartesian_jordan_product(z1,z2).to_vector() + (1, 0, 2, 6, 3, 4) + + """ + m = len(self.cartesian_factors()) + projections = ( self.cartesian_projection(i) for i in range(m) ) + products = ( P(x)*P(y) for P in projections ) + return self._cartesian_product_of_elements(tuple(products)) + + def cartesian_inner_product(self, x, y): + r""" + The standard componentwise Cartesian inner-product. + + We project ``x`` and ``y`` onto our factors, and add up the + inner-products from the subalgebras. This may still be useful + after (if) the default inner product in the Cartesian product + algebra is overridden. + + SETUP:: + + sage: from mjo.eja.eja_algebra import (HadamardEJA, + ....: QuaternionHermitianEJA) - sage: J1 = HadamardEJA(2, field=QQ) - sage: J2 = JordanSpinEJA(3, field=QQ) - sage: J = DirectSumEJA(J1,J2) - sage: J.cartesian_factors() - (Euclidean Jordan algebra of dimension 2 over Rational Field, - Euclidean Jordan algebra of dimension 3 over Rational Field) - - """ - return self._cartprod_algebra.cartesian_factors() - - -# def projections(self): -# r""" -# Return a pair of projections onto this algebra's factors. - -# SETUP:: - -# sage: from mjo.eja.eja_algebra import (JordanSpinEJA, -# ....: ComplexHermitianEJA, -# ....: DirectSumEJA) - -# EXAMPLES:: - -# sage: J1 = JordanSpinEJA(2) -# sage: J2 = ComplexHermitianEJA(2) -# sage: J = DirectSumEJA(J1,J2) -# sage: (pi_left, pi_right) = J.projections() -# sage: J.one().to_vector() -# (1, 0, 1, 0, 0, 1) -# sage: pi_left(J.one()).to_vector() -# (1, 0) -# sage: pi_right(J.one()).to_vector() -# (1, 0, 0, 1) - -# """ -# (J1,J2) = self.factors() -# m = J1.dimension() -# n = J2.dimension() -# V_basis = self.vector_space().basis() -# # Need to specify the dimensions explicitly so that we don't -# # wind up with a zero-by-zero matrix when we want e.g. a -# # zero-by-two matrix (important for composing things). -# P1 = matrix(self.base_ring(), m, m+n, V_basis[:m]) -# P2 = matrix(self.base_ring(), n, m+n, V_basis[m:]) -# pi_left = FiniteDimensionalEJAOperator(self,J1,P1) -# pi_right = FiniteDimensionalEJAOperator(self,J2,P2) -# return (pi_left, pi_right) - -# def inclusions(self): -# r""" -# Return the pair of inclusion maps from our factors into us. - -# SETUP:: - -# sage: from mjo.eja.eja_algebra import (random_eja, -# ....: JordanSpinEJA, -# ....: RealSymmetricEJA, -# ....: DirectSumEJA) - -# EXAMPLES:: - -# sage: J1 = JordanSpinEJA(3) -# sage: J2 = RealSymmetricEJA(2) -# sage: J = DirectSumEJA(J1,J2) -# sage: (iota_left, iota_right) = J.inclusions() -# sage: iota_left(J1.zero()) == J.zero() -# True -# sage: iota_right(J2.zero()) == J.zero() -# True -# sage: J1.one().to_vector() -# (1, 0, 0) -# sage: iota_left(J1.one()).to_vector() -# (1, 0, 0, 0, 0, 0) -# sage: J2.one().to_vector() -# (1, 0, 1) -# sage: iota_right(J2.one()).to_vector() -# (0, 0, 0, 1, 0, 1) -# sage: J.one().to_vector() -# (1, 0, 0, 1, 0, 1) - -# TESTS: - -# Composing a projection with the corresponding inclusion should -# produce the identity map, and mismatching them should produce -# the zero map:: - -# sage: set_random_seed() -# sage: J1 = random_eja() -# sage: J2 = random_eja() -# sage: J = DirectSumEJA(J1,J2) -# sage: (iota_left, iota_right) = J.inclusions() -# sage: (pi_left, pi_right) = J.projections() -# sage: pi_left*iota_left == J1.one().operator() -# True -# sage: pi_right*iota_right == J2.one().operator() -# True -# sage: (pi_left*iota_right).is_zero() -# True -# sage: (pi_right*iota_left).is_zero() -# True - -# """ -# (J1,J2) = self.factors() -# m = J1.dimension() -# n = J2.dimension() -# V_basis = self.vector_space().basis() -# # Need to specify the dimensions explicitly so that we don't -# # wind up with a zero-by-zero matrix when we want e.g. a -# # two-by-zero matrix (important for composing things). -# I1 = matrix.column(self.base_ring(), m, m+n, V_basis[:m]) -# I2 = matrix.column(self.base_ring(), n, m+n, V_basis[m:]) -# iota_left = FiniteDimensionalEJAOperator(J1,self,I1) -# iota_right = FiniteDimensionalEJAOperator(J2,self,I2) -# return (iota_left, iota_right) - -# def inner_product(self, x, y): -# r""" -# The standard Cartesian inner-product. - -# We project ``x`` and ``y`` onto our factors, and add up the -# inner-products from the subalgebras. - -# SETUP:: - - -# sage: from mjo.eja.eja_algebra import (HadamardEJA, -# ....: QuaternionHermitianEJA, -# ....: DirectSumEJA) - -# EXAMPLE:: - -# sage: J1 = HadamardEJA(3,field=QQ) -# sage: J2 = QuaternionHermitianEJA(2,field=QQ,orthonormalize=False) -# sage: J = DirectSumEJA(J1,J2) -# sage: x1 = J1.one() -# sage: x2 = x1 -# sage: y1 = J2.one() -# sage: y2 = y1 -# sage: x1.inner_product(x2) -# 3 -# sage: y1.inner_product(y2) -# 2 -# sage: J.one().inner_product(J.one()) -# 5 - -# """ -# (pi_left, pi_right) = self.projections() -# x1 = pi_left(x) -# x2 = pi_right(x) -# y1 = pi_left(y) -# y2 = pi_right(y) - -# return (x1.inner_product(y1) + x2.inner_product(y2)) + EXAMPLE:: + sage: J1 = HadamardEJA(3,field=QQ) + sage: J2 = QuaternionHermitianEJA(2,field=QQ,orthonormalize=False) + sage: J = cartesian_product([J1,J2]) + sage: x1 = J1.one() + sage: x2 = x1 + sage: y1 = J2.one() + sage: y2 = y1 + sage: x1.inner_product(x2) + 3 + sage: y1.inner_product(y2) + 2 + sage: z1 = J._cartesian_product_of_elements((x1,y1)) + sage: z2 = J._cartesian_product_of_elements((x2,y2)) + sage: J.cartesian_inner_product(z1,z2) + 5 + + """ + m = len(self.cartesian_factors()) + projections = ( self.cartesian_projection(i) for i in range(m) ) + return sum( P(x).inner_product(P(y)) for P in projections ) + + + Element = FiniteDimensionalEJAElement + + +class FiniteDimensionalEJA_CartesianProduct(CartesianProductEJA): + r""" + A wrapper around the :class:`CartesianProductEJA` class that gets + used by the ``cartesian_product`` functor. Its one job is to set + ``orthonormalize=False``, since ``cartesian_product()`` can't be + made to pass that option through. And if we try to orthonormalize + over the rationals, we get conversion errors. If you want a non- + standard Jordan product or inner product, or if you want to + orthonormalize the basis, use :class:`CartesianProductEJA` + directly. + """ + def __init__(self, modules, **options): + CombinatorialFreeModule_CartesianProduct.__init__(self, + modules, + **options) + CartesianProductEJA.__init__(self, modules, orthonormalize=False) +FiniteDimensionalEJA.CartesianProduct = FiniteDimensionalEJA_CartesianProduct random_eja = ConcreteEJA.random_instance