X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=mjo%2Feja%2Feja_algebra.py;h=4947fe82bb981401a09a039306516b4b0631113a;hb=f911ca107b6ad2a92547a255311ef7f16978feac;hp=05dea56e6c389a25713b0f99d95663c8d2998a0d;hpb=e776b06ba3e77214bf670043bbff81148891b195;p=sage.d.git diff --git a/mjo/eja/eja_algebra.py b/mjo/eja/eja_algebra.py index 05dea56..4947fe8 100644 --- a/mjo/eja/eja_algebra.py +++ b/mjo/eja/eja_algebra.py @@ -60,6 +60,9 @@ class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule): self._rank = rank self._natural_basis = natural_basis + # TODO: HACK for the charpoly.. needs redesign badly. + self._basis_normalizers = None + if category is None: category = MagmaticAlgebras(field).FiniteDimensional() category = category.WithBasis().Unital() @@ -224,6 +227,7 @@ class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule): return V.span_of_basis(b) + @cached_method def _charpoly_coeff(self, i): """ @@ -234,6 +238,19 @@ class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule): store the trace/determinant (a_{r-1} and a_{0} respectively) separate from the entire characteristic polynomial. """ + if self._basis_normalizers is not None: + # Must be a matrix class? + # WARNING/TODO: this whole mess is mis-designed. + n = self.natural_basis_space().nrows() + field = self.base_ring().base_ring() # yeeeeaaaahhh + J = self.__class__(n, field, False) + (_,x,_,_) = J._charpoly_matrix_system() + p = J._charpoly_coeff(i) + # p might be missing some vars, have to substitute "optionally" + pairs = zip(x.base_ring().gens(), self._basis_normalizers) + substitutions = { v: v*c for (v,c) in pairs } + return p.subs(substitutions) + (A_of_x, x, xr, detA) = self._charpoly_matrix_system() R = A_of_x.base_ring() if i >= self.rank(): @@ -416,9 +433,9 @@ class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule): True """ - if (not x in self) or (not y in self): - raise TypeError("arguments must live in this algebra") - return x.trace_inner_product(y) + X = x.natural_representation() + Y = y.natural_representation() + return self.__class__.natural_inner_product(X,Y) def is_trivial(self): @@ -537,6 +554,20 @@ class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule): return self._natural_basis[0].matrix_space() + @staticmethod + def natural_inner_product(X,Y): + """ + Compute the inner product of two naturally-represented elements. + + For example in the real symmetric matrix EJA, this will compute + the trace inner-product of two n-by-n symmetric matrices. The + default should work for the real cartesian product EJA, the + Jordan spin EJA, and the real symmetric matrices. The others + will have to be overridden. + """ + return (X.conjugate_transpose()*Y).trace() + + @cached_method def one(self): """ @@ -748,7 +779,30 @@ class RealCartesianProductEJA(FiniteDimensionalEuclideanJordanAlgebra): return fdeja.__init__(field, mult_table, rank=n, **kwargs) def inner_product(self, x, y): - return _usual_ip(x,y) + """ + Faster to reimplement than to use natural representations. + + SETUP:: + + sage: from mjo.eja.eja_algebra import RealCartesianProductEJA + + TESTS: + + Ensure that this is the usual inner product for the algebras + over `R^n`:: + + sage: set_random_seed() + sage: n = ZZ.random_element(1,5) + sage: J = RealCartesianProductEJA(n) + sage: x = J.random_element() + sage: y = J.random_element() + sage: X = x.natural_representation() + sage: Y = y.natural_representation() + sage: x.inner_product(y) == J.__class__.natural_inner_product(X,Y) + True + + """ + return x.to_vector().inner_product(y.to_vector()) def random_eja(): @@ -814,7 +868,7 @@ def _real_symmetric_basis(n, field): sage: set_random_seed() sage: n = ZZ.random_element(1,5) - sage: B = _real_symmetric_basis(n, QQbar) + sage: B = _real_symmetric_basis(n, QQ) sage: all( M.is_symmetric() for M in B) True @@ -829,8 +883,6 @@ def _real_symmetric_basis(n, field): Sij = Eij else: Sij = Eij + Eij.transpose() - # Now normalize it. - Sij = Sij / _real_symmetric_matrix_ip(Sij,Sij).sqrt() S.append(Sij) return tuple(S) @@ -877,18 +929,15 @@ def _complex_hermitian_basis(n, field): Sij = _embed_complex_matrix(Eij) S.append(Sij) else: - # Beware, orthogonal but not normalized! The second one - # has a minus because it's conjugated. + # The second one has a minus because it's conjugated. Sij_real = _embed_complex_matrix(Eij + Eij.transpose()) S.append(Sij_real) Sij_imag = _embed_complex_matrix(I*Eij - I*Eij.transpose()) S.append(Sij_imag) - # Normalize these with our inner product before handing them back. - # And since we embedded them, we can drop back to the "field" that - # we started with instead of the complex extension "F". - return tuple( (s / _complex_hermitian_matrix_ip(s,s).sqrt()).change_ring(field) - for s in S ) + # Since we embedded these, we can drop back to the "field" that we + # started with instead of the complex extension "F". + return tuple( s.change_ring(field) for s in S ) @@ -1204,10 +1253,6 @@ def _unembed_quaternion_matrix(M): return matrix(Q, n/4, elements) -# The usual inner product on R^n. -def _usual_ip(x,y): - 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 # algebra uses the same inner product, except divided by 2. @@ -1216,15 +1261,6 @@ def _matrix_ip(X,Y): Y_mat = Y.natural_representation() return (X_mat*Y_mat).trace() -def _real_symmetric_matrix_ip(X,Y): - return (X*Y).trace() - -def _complex_hermitian_matrix_ip(X,Y): - # This takes EMBEDDED matrices. - Xu = _unembed_complex_matrix(X) - Yu = _unembed_complex_matrix(Y) - # The trace need not be real; consider Xu = (i*I) and Yu = I. - return ((Xu*Yu).trace()).vector()[0] # real part, I guess class RealSymmetricEJA(FiniteDimensionalEuclideanJordanAlgebra): """ @@ -1307,8 +1343,10 @@ class RealSymmetricEJA(FiniteDimensionalEuclideanJordanAlgebra): True """ - def __init__(self, n, field=QQ, **kwargs): - if n > 1: + def __init__(self, n, field=QQ, normalize_basis=True, **kwargs): + S = _real_symmetric_basis(n, field) + + if n > 1 and normalize_basis: # We'll need sqrt(2) to normalize the basis, and this # winds up in the multiplication table, so the whole # algebra needs to be over the field extension. @@ -1317,8 +1355,12 @@ class RealSymmetricEJA(FiniteDimensionalEuclideanJordanAlgebra): p = z**2 - 2 if p.is_irreducible(): field = NumberField(p, 'sqrt2', embedding=RLF(2).sqrt()) + S = [ s.change_ring(field) for s in S ] + self._basis_normalizers = tuple( + ~(self.__class__.natural_inner_product(s,s).sqrt()) + for s in S ) + S = tuple( s*c for (s,c) in zip(S,self._basis_normalizers) ) - S = _real_symmetric_basis(n, field) Qs = _multiplication_table_from_matrix_basis(S) fdeja = super(RealSymmetricEJA, self) @@ -1328,10 +1370,6 @@ class RealSymmetricEJA(FiniteDimensionalEuclideanJordanAlgebra): natural_basis=S, **kwargs) - def inner_product(self, x, y): - X = x.natural_representation() - Y = y.natural_representation() - return _real_symmetric_matrix_ip(X,Y) class ComplexHermitianEJA(FiniteDimensionalEuclideanJordanAlgebra): @@ -1405,8 +1443,10 @@ class ComplexHermitianEJA(FiniteDimensionalEuclideanJordanAlgebra): True """ - def __init__(self, n, field=QQ, **kwargs): - if n > 1: + def __init__(self, n, field=QQ, normalize_basis=True, **kwargs): + S = _complex_hermitian_basis(n, field) + + if n > 1 and normalize_basis: # We'll need sqrt(2) to normalize the basis, and this # winds up in the multiplication table, so the whole # algebra needs to be over the field extension. @@ -1415,8 +1455,12 @@ class ComplexHermitianEJA(FiniteDimensionalEuclideanJordanAlgebra): p = z**2 - 2 if p.is_irreducible(): field = NumberField(p, 'sqrt2', embedding=RLF(2).sqrt()) + S = [ s.change_ring(field) for s in S ] + self._basis_normalizers = tuple( + ~(self.__class__.natural_inner_product(s,s).sqrt()) + for s in S ) + S = tuple( s*c for (s,c) in zip(S,self._basis_normalizers) ) - S = _complex_hermitian_basis(n, field) Qs = _multiplication_table_from_matrix_basis(S) fdeja = super(ComplexHermitianEJA, self) @@ -1427,11 +1471,12 @@ class ComplexHermitianEJA(FiniteDimensionalEuclideanJordanAlgebra): **kwargs) - def inner_product(self, x, y): - X = x.natural_representation() - Y = y.natural_representation() - return _complex_hermitian_matrix_ip(X,Y) - + @staticmethod + def natural_inner_product(X,Y): + Xu = _unembed_complex_matrix(X) + Yu = _unembed_complex_matrix(Y) + # The trace need not be real; consider Xu = (i*I) and Yu = I. + return ((Xu*Yu).trace()).vector()[0] # real part, I guess class QuaternionHermitianEJA(FiniteDimensionalEuclideanJordanAlgebra): """ @@ -1487,8 +1532,8 @@ class QuaternionHermitianEJA(FiniteDimensionalEuclideanJordanAlgebra): True """ - def __init__(self, n, field=QQ, **kwargs): - S = _quaternion_hermitian_basis(n, field) + def __init__(self, n, field=QQ, normalize_basis=True, **kwargs): + S = _quaternion_hermitian_basis(n, field, normalize_basis) Qs = _multiplication_table_from_matrix_basis(S) fdeja = super(QuaternionHermitianEJA, self) @@ -1584,4 +1629,27 @@ class JordanSpinEJA(FiniteDimensionalEuclideanJordanAlgebra): return fdeja.__init__(field, mult_table, rank=min(n,2), **kwargs) def inner_product(self, x, y): - return _usual_ip(x,y) + """ + Faster to reimplement than to use natural representations. + + SETUP:: + + sage: from mjo.eja.eja_algebra import JordanSpinEJA + + TESTS: + + Ensure that this is the usual inner product for the algebras + over `R^n`:: + + sage: set_random_seed() + sage: n = ZZ.random_element(1,5) + sage: J = JordanSpinEJA(n) + sage: x = J.random_element() + sage: y = J.random_element() + sage: X = x.natural_representation() + sage: Y = y.natural_representation() + sage: x.inner_product(y) == J.__class__.natural_inner_product(X,Y) + True + + """ + return x.to_vector().inner_product(y.to_vector())