X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=mjo%2Feja%2Feja_algebra.py;h=9ba146bc6e8fd6dc97dcf1f7d70058cd046528a4;hb=3baadd6fb5c765caab2bd57d1d6ed764b03d53b3;hp=a4208519268cf204cfe43b80dddf882f9638fcd1;hpb=d0792efbb64cc79d920275b9a9e5dbbadbea3b4c;p=sage.d.git diff --git a/mjo/eja/eja_algebra.py b/mjo/eja/eja_algebra.py index a420851..9ba146b 100644 --- a/mjo/eja/eja_algebra.py +++ b/mjo/eja/eja_algebra.py @@ -119,11 +119,12 @@ class FiniteDimensionalEJA(CombinatorialFreeModule): # Call the superclass constructor so that we can use its from_vector() # method to build our multiplication table. n = len(basis) - super().__init__(field, - range(n), - prefix=prefix, - category=category, - bracket=False) + CombinatorialFreeModule.__init__(self, + field, + range(n), + prefix=prefix, + category=category, + bracket=False) # Now comes all of the hard work. We'll be constructing an # ambient vector space V that our (vectorized) basis lives in, @@ -305,22 +306,32 @@ class FiniteDimensionalEJA(CombinatorialFreeModule): sage: y = J.random_element() sage: (n == 1) or (x.inner_product(y) == (x*y).trace()/2) True + """ B = self._inner_product_matrix return (B*x.to_vector()).inner_product(y.to_vector()) - def _is_commutative(self): + def is_associative(self): r""" - Whether or not this algebra's multiplication table is commutative. + Return whether or not this algebra's Jordan product is associative. + + SETUP:: + + sage: from mjo.eja.eja_algebra import ComplexHermitianEJA + + EXAMPLES:: + + sage: J = ComplexHermitianEJA(3, field=QQ, orthonormalize=False) + sage: J.is_associative() + False + sage: x = sum(J.gens()) + sage: A = x.subalgebra_generated_by(orthonormalize=False) + sage: A.is_associative() + True - This method should of course always return ``True``, unless - this algebra was constructed with ``check_axioms=False`` and - passed an invalid multiplication table. """ - return all( self.product_on_basis(i,j) == self.product_on_basis(i,j) - for i in range(self.dimension()) - for j in range(self.dimension()) ) + return "Associative" in self.category().axioms() def _is_jordanian(self): r""" @@ -329,7 +340,7 @@ class FiniteDimensionalEJA(CombinatorialFreeModule): We only check one arrangement of `x` and `y`, so for a ``True`` result to be truly true, you should also check - :meth:`_is_commutative`. This method should of course always + :meth:`is_commutative`. This method should of course always return ``True``, unless this algebra was constructed with ``check_axioms=False`` and passed an invalid multiplication table. """ @@ -1019,14 +1030,12 @@ class FiniteDimensionalEJA(CombinatorialFreeModule): if not c.is_idempotent(): raise ValueError("element is not idempotent: %s" % c) - from mjo.eja.eja_subalgebra import FiniteDimensionalEJASubalgebra - # Default these to what they should be if they turn out to be # trivial, because eigenspaces_left() won't return eigenvalues # corresponding to trivial spaces (e.g. it returns only the # eigenspace corresponding to lambda=1 if you take the # decomposition relative to the identity element). - trivial = FiniteDimensionalEJASubalgebra(self, ()) + trivial = self.subalgebra(()) J0 = trivial # eigenvalue zero J5 = VectorSpace(self.base_ring(), 0) # eigenvalue one-half J1 = trivial # eigenvalue one @@ -1036,9 +1045,7 @@ class FiniteDimensionalEJA(CombinatorialFreeModule): J5 = eigspace else: gens = tuple( self.from_vector(b) for b in eigspace.basis() ) - subalg = FiniteDimensionalEJASubalgebra(self, - gens, - check_axioms=False) + subalg = self.subalgebra(gens, check_axioms=False) if eigval == 0: J0 = subalg elif eigval == 1: @@ -1257,6 +1264,17 @@ class FiniteDimensionalEJA(CombinatorialFreeModule): return len(self._charpoly_coefficients()) + def subalgebra(self, basis, **kwargs): + r""" + Create a subalgebra of this algebra from the given basis. + + This is a simple wrapper around a subalgebra class constructor + that can be overridden in subclasses. + """ + from mjo.eja.eja_subalgebra import FiniteDimensionalEJASubalgebra + return FiniteDimensionalEJASubalgebra(self, basis, **kwargs) + + def vector_space(self): """ Return the vector space that underlies this algebra. @@ -2384,7 +2402,11 @@ class HadamardEJA(ConcreteEJA): if "check_axioms" not in kwargs: kwargs["check_axioms"] = False column_basis = tuple( b.column() for b in FreeModule(ZZ, n).basis() ) - super().__init__(column_basis, jordan_product, inner_product, **kwargs) + super().__init__(column_basis, + jordan_product, + inner_product, + associative=True, + **kwargs) self.rank.set_cache(n) if n == 0: @@ -2779,6 +2801,25 @@ class CartesianProductEJA(CombinatorialFreeModule_CartesianProduct, sage: J.rank() == J1.rank() + J2.rank() True + The product algebra will be associative if and only if all of its + components are associative:: + + sage: J1 = HadamardEJA(2) + sage: J1.is_associative() + True + sage: J2 = HadamardEJA(3) + sage: J2.is_associative() + True + sage: J3 = RealSymmetricEJA(3) + sage: J3.is_associative() + False + sage: CP1 = cartesian_product([J1,J2]) + sage: CP1.is_associative() + True + sage: CP2 = cartesian_product([J1,J3]) + sage: CP2.is_associative() + False + TESTS: All factors must share the same base field:: @@ -2790,19 +2831,6 @@ class CartesianProductEJA(CombinatorialFreeModule_CartesianProduct, ... ValueError: all factors must share the same base field - The "cached" Jordan and inner products are the componentwise - ones:: - - sage: set_random_seed() - sage: J1 = random_eja() - sage: J2 = random_eja() - sage: J = cartesian_product([J1,J2]) - sage: x,y = J.random_elements(2) - sage: x*y == J.cartesian_jordan_product(x,y) - True - sage: x.inner_product(y) == J.cartesian_inner_product(x,y) - True - The cached unit element is the same one that would be computed:: sage: set_random_seed() # long time @@ -2816,14 +2844,16 @@ class CartesianProductEJA(CombinatorialFreeModule_CartesianProduct, True """ - def __init__(self, modules, **kwargs): + def __init__(self, algebras, **kwargs): CombinatorialFreeModule_CartesianProduct.__init__(self, - modules, + algebras, **kwargs) - field = modules[0].base_ring() - if not all( J.base_ring() == field for J in modules ): + field = algebras[0].base_ring() + if not all( J.base_ring() == field for J in algebras ): raise ValueError("all factors must share the same base field") + associative = all( m.is_associative() for m in algebras ) + # The definition of matrix_space() and self.basis() relies # only on the stuff in the CFM_CartesianProduct class, which # we've already initialized. @@ -2859,13 +2889,14 @@ class CartesianProductEJA(CombinatorialFreeModule_CartesianProduct, inner_product, field=field, orthonormalize=False, + associative=associative, cartesian_product=True, check_field=False, check_axioms=False) - ones = tuple(J.one() for J in modules) + ones = tuple(J.one() for J in algebras) self.one.set_cache(self._cartesian_product_of_elements(ones)) - self.rank.set_cache(sum(J.rank() for J in modules)) + self.rank.set_cache(sum(J.rank() for J in algebras)) def matrix_space(self): r""" @@ -3076,82 +3107,6 @@ class CartesianProductEJA(CombinatorialFreeModule_CartesianProduct, return FiniteDimensionalEJAOperator(Ji,self,Ei.matrix()) - def cartesian_jordan_product(self, x, y): - r""" - 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) - - 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) - - 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 ) - - def _element_constructor_(self, elt): r""" Construct an element of this algebra from an ordered tuple. @@ -3180,6 +3135,16 @@ class CartesianProductEJA(CombinatorialFreeModule_CartesianProduct, except: raise ValueError("not an element of this algebra") + def subalgebra(self, basis, **kwargs): + r""" + Create a subalgebra of this algebra from the given basis. + + This overrides the superclass method to use a special class + for Cartesian products. + """ + from mjo.eja.eja_subalgebra import CartesianProductEJASubalgebra + return CartesianProductEJASubalgebra(self, basis, **kwargs) + Element = CartesianProductEJAElement