eja: rework the quadratic representation tests in terms of morphisms.

[sage.d.git] / mjo / eja / euclidean_jordan_algebra.py

diff --git a/mjo/eja/euclidean_jordan_algebra.py b/mjo/eja/euclidean_jordan_algebra.py
index b239dc7287326f95815708ca3b80fd2c64d99b1a..2b00302dc73461f089390a715bb1f12dc7aef6c1 100644 (file)
--- a/mjo/eja/euclidean_jordan_algebra.py
+++ b/mjo/eja/euclidean_jordan_algebra.py
@@ -16,8 +16,10 @@ from sage.algebras.finite_dimensional_algebras.finite_dimensional_algebra_morphi
 
 class FiniteDimensionalEuclideanJordanAlgebraMorphism(FiniteDimensionalAlgebraMorphism):
     """
 
 class FiniteDimensionalEuclideanJordanAlgebraMorphism(FiniteDimensionalAlgebraMorphism):
     """

-    A very thin wrapper around FiniteDimensionalAlgebraMorphism that
-    does only three things:
+    A linear map between two finite-dimensional EJAs.
+
+    This is a very thin wrapper around FiniteDimensionalAlgebraMorphism
+    that does only a few things:

 
       1. Avoids the ``unitary`` and ``check`` arguments to the constructor
          that will always be ``False``. This is necessary because these
 
       1. Avoids the ``unitary`` and ``check`` arguments to the constructor
          that will always be ``False``. This is necessary because these


@@ -28,33 +30,43 @@ class FiniteDimensionalEuclideanJordanAlgebraMorphism(FiniteDimensionalAlgebraMo
       2. Inputs and outputs the underlying matrix with respect to COLUMN
          vectors, unlike the parent class.
 
       2. Inputs and outputs the underlying matrix with respect to COLUMN
          vectors, unlike the parent class.
 

-      3. Allows us to add morphisms in the obvious way.
+      3. Allows us to add, subtract, negate, multiply (compose), and
+         invert morphisms in the obvious way.

 
     If this seems a bit heavyweight, it is. I would have been happy to
     use a the ring morphism that underlies the finite-dimensional
     algebra morphism, but they don't seem to be callable on elements of
 
     If this seems a bit heavyweight, it is. I would have been happy to
     use a the ring morphism that underlies the finite-dimensional
     algebra morphism, but they don't seem to be callable on elements of

-    our EJA, and you can't add them.
+    our EJA, and you can't add/multiply/etc. them.

     """
 
     def __add__(self, other):
         """
         Add two EJA morphisms in the obvious way.
 
     """
 
     def __add__(self, other):
         """
         Add two EJA morphisms in the obvious way.
 

-        EXAMPLES:
+        EXAMPLES::

 
             sage: J = RealSymmetricEJA(3)
             sage: x = J.zero()
 
             sage: J = RealSymmetricEJA(3)
             sage: x = J.zero()

-            sage: y = J.zero()
+            sage: y = J.one()

             sage: x.operator() + y.operator()
             Morphism from Euclidean Jordan algebra of degree 6 over Rational
             Field to Euclidean Jordan algebra of degree 6 over Rational Field
             given by matrix
             sage: x.operator() + y.operator()
             Morphism from Euclidean Jordan algebra of degree 6 over Rational
             Field to Euclidean Jordan algebra of degree 6 over Rational Field
             given by matrix

-            [0 0 0 0 0 0]
-            [0 0 0 0 0 0]
-            [0 0 0 0 0 0]
-            [0 0 0 0 0 0]
-            [0 0 0 0 0 0]
-            [0 0 0 0 0 0]
+            [1 0 0 0 0 0]
+            [0 1 0 0 0 0]
+            [0 0 1 0 0 0]
+            [0 0 0 1 0 0]
+            [0 0 0 0 1 0]
+            [0 0 0 0 0 1]
+
+        TESTS::
+
+            sage: set_random_seed()
+            sage: J = random_eja()
+            sage: x = J.random_element()
+            sage: y = J.random_element()
+            sage: (x.operator() + y.operator()) in J.Hom(J)
+            True

 
         """
         P = self.parent()
 
         """
         P = self.parent()


@@ -74,6 +86,112 @@ class FiniteDimensionalEuclideanJordanAlgebraMorphism(FiniteDimensionalAlgebraMo
                                                   check=False)
 
 
                                                   check=False)
 
 

+    def __invert__(self):
+        """
+        EXAMPLES::
+
+            sage: J = RealSymmetricEJA(2)
+            sage: x = J.linear_combination(zip(range(len(J.gens())), J.gens()))
+            sage: x.is_invertible()
+            True
+            sage: ~x.operator()
+            Morphism from Euclidean Jordan algebra of degree 3 over Rational
+            Field to Euclidean Jordan algebra of degree 3 over Rational Field
+            given by matrix
+            [-3/2    2 -1/2]
+            [   1    0    0]
+            [-1/2    0  1/2]
+            sage: x.operator_matrix().inverse()
+            [-3/2    2 -1/2]
+            [   1    0    0]
+            [-1/2    0  1/2]
+
+        TESTS::
+
+            sage: set_random_seed()
+            sage: J = random_eja()
+            sage: x = J.random_element()
+            sage: not x.is_invertible() or (
+            ....:   (~x.operator()).matrix() == x.operator_matrix().inverse() )
+            True
+
+        """
+        A = self.matrix()
+        if not A.is_invertible():
+            raise ValueError("morphism is not invertible")
+
+        P = self.parent()
+        return FiniteDimensionalEuclideanJordanAlgebraMorphism(self.parent(),
+                                                                A.inverse())
+
+    def __mul__(self, other):
+        """
+        Compose two EJA morphisms using multiplicative notation.
+
+        EXAMPLES::
+
+            sage: J = RealSymmetricEJA(3)
+            sage: x = J.zero()
+            sage: y = J.one()
+            sage: x.operator() * y.operator()
+            Morphism from Euclidean Jordan algebra of degree 6 over Rational
+            Field to Euclidean Jordan algebra of degree 6 over Rational Field
+            given by matrix
+            [0 0 0 0 0 0]
+            [0 0 0 0 0 0]
+            [0 0 0 0 0 0]
+            [0 0 0 0 0 0]
+            [0 0 0 0 0 0]
+            [0 0 0 0 0 0]
+
+        TESTS::
+
+            sage: set_random_seed()
+            sage: J = random_eja()
+            sage: x = J.random_element()
+            sage: y = J.random_element()
+            sage: (x.operator() * y.operator()) in J.Hom(J)
+            True
+
+        """
+        if not other.codomain() is self.domain():
+            raise ValueError("(co)domains must agree for composition")
+
+        return FiniteDimensionalEuclideanJordanAlgebraMorphism(
+                  self.parent(),
+                  self.matrix()*other.matrix() )
+
+
+    def __neg__(self):
+        """
+        Negate this morphism.
+
+        EXAMPLES::
+
+            sage: J = RealSymmetricEJA(2)
+            sage: x = J.one()
+            sage: -x.operator()
+            Morphism from Euclidean Jordan algebra of degree 3 over Rational
+            Field to Euclidean Jordan algebra of degree 3 over Rational Field
+            given by matrix
+            [-1  0  0]
+            [ 0 -1  0]
+            [ 0  0 -1]
+
+        TESTS::
+
+            sage: set_random_seed()
+            sage: J = random_eja()
+            sage: x = J.random_element()
+            sage: -x.operator() in J.Hom(J)
+            True
+
+        """
+        return FiniteDimensionalEuclideanJordanAlgebraMorphism(
+                  self.parent(),
+                  -self.matrix() )
+
+

     def _repr_(self):
         """
         We override only the representation that is shown to the user,
     def _repr_(self):
         """
         We override only the representation that is shown to the user,


@@ -108,6 +226,36 @@ class FiniteDimensionalEuclideanJordanAlgebraMorphism(FiniteDimensionalAlgebraMo
         return "Morphism from {} to {} given by matrix\n{}".format(
             self.domain(), self.codomain(), self.matrix())
 
         return "Morphism from {} to {} given by matrix\n{}".format(
             self.domain(), self.codomain(), self.matrix())
 

+
+    def __sub__(self, other):
+        """
+        Subtract one morphism from another using addition and negation.
+
+        EXAMPLES::
+
+            sage: J = RealSymmetricEJA(2)
+            sage: L1 = J.one().operator()
+            sage: L1 - L1
+            Morphism from Euclidean Jordan algebra of degree 3 over Rational
+            Field to Euclidean Jordan algebra of degree 3 over Rational
+            Field given by matrix
+            [0 0 0]
+            [0 0 0]
+            [0 0 0]
+
+        TESTS::
+
+            sage: set_random_seed()
+            sage: J = random_eja()
+            sage: x = J.random_element()
+            sage: y = J.random_element()
+            sage: x.operator() - y.operator() in J.Hom(J)
+            True
+
+        """
+        return self + (-other)
+
+

     def matrix(self):
         """
         Return the matrix of this morphism with respect to a left-action
     def matrix(self):
         """
         Return the matrix of this morphism with respect to a left-action


@@ -1220,7 +1368,7 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra):
                 sage: D = (x0^2 - x_bar.inner_product(x_bar))*D
                 sage: D = D + 2*x_bar.tensor_product(x_bar)
                 sage: Q = block_matrix(2,2,[A,B,C,D])
                 sage: D = (x0^2 - x_bar.inner_product(x_bar))*D
                 sage: D = D + 2*x_bar.tensor_product(x_bar)
                 sage: Q = block_matrix(2,2,[A,B,C,D])

-                sage: Q == x.quadratic_representation()
+                sage: Q == x.quadratic_representation().operator_matrix()

                 True
 
             Test all of the properties from Theorem 11.2 in Alizadeh::
                 True
 
             Test all of the properties from Theorem 11.2 in Alizadeh::


@@ -1229,8 +1377,8 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra):
                 sage: J = random_eja()
                 sage: x = J.random_element()
                 sage: y = J.random_element()
                 sage: J = random_eja()
                 sage: x = J.random_element()
                 sage: y = J.random_element()

-                sage: Lx = x.operator_matrix()
-                sage: Lxx = (x*x).operator_matrix()
+                sage: Lx = x.operator()
+                sage: Lxx = (x*x).operator()

                 sage: Qx = x.quadratic_representation()
                 sage: Qy = y.quadratic_representation()
                 sage: Qxy = x.quadratic_representation(y)
                 sage: Qx = x.quadratic_representation()
                 sage: Qy = y.quadratic_representation()
                 sage: Qxy = x.quadratic_representation(y)


@@ -1251,17 +1399,16 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra):
 
             Property 3:
 
 
             Property 3:
 

-                sage: not x.is_invertible() or (
-                ....:     Qx*x.inverse().vector() == x.vector() )
+                sage: not x.is_invertible() or ( Qx(x.inverse()) == x )

                 True
 
                 sage: not x.is_invertible() or (
                 True
 
                 sage: not x.is_invertible() or (

-                ....:   Qx.inverse()
+                ....:   ~Qx

                 ....:   ==
                 ....:   x.inverse().quadratic_representation() )
                 True
 
                 ....:   ==
                 ....:   x.inverse().quadratic_representation() )
                 True
 

-                sage: Qxy*(J.one().vector()) == (x*y).vector()
+                sage: Qxy(J.one()) == x*y

                 True
 
             Property 4:
                 True
 
             Property 4:


@@ -1274,15 +1421,15 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra):
                 sage: not x.is_invertible() or (
                 ....:   x.quadratic_representation(x.inverse())*Qx
                 ....:   ==
                 sage: not x.is_invertible() or (
                 ....:   x.quadratic_representation(x.inverse())*Qx
                 ....:   ==

-                ....:   2*x.operator_matrix()*Qex - Qx )
+                ....:   2*x.operator()*Qex - Qx )

                 True
 
                 True
 

-                sage: 2*x.operator_matrix()*Qex - Qx == Lxx
+                sage: 2*x.operator()*Qex - Qx == Lxx

                 True
 
             Property 5:
 
                 True
 
             Property 5:
 

-                sage: J(Qy*x.vector()).quadratic_representation() == Qy*Qx*Qy
+                sage: Qy(x).quadratic_representation() == Qy*Qx*Qy

                 True
 
             Property 6:
                 True
 
             Property 6:


@@ -1293,13 +1440,13 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra):
             Property 7:
 
                 sage: not x.is_invertible() or (
             Property 7:
 
                 sage: not x.is_invertible() or (

-                ....:   Qx*x.inverse().operator_matrix() == Lx )
+                ....:   Qx*x.inverse().operator() == Lx )

                 True
 
             Property 8:
 
                 sage: not x.operator_commutes_with(y) or (
                 True
 
             Property 8:
 
                 sage: not x.operator_commutes_with(y) or (

-                ....:   J(Qx*y.vector())^n == J(Qxn*(y^n).vector()) )
+                ....:   Qx(y)^n == Qxn(y^n) )

                 True
 
             """
                 True
 
             """


@@ -1308,9 +1455,9 @@ class FiniteDimensionalEuclideanJordanAlgebra(FiniteDimensionalAlgebra):
             elif not other in self.parent():
                 raise TypeError("'other' must live in the same algebra")
 
             elif not other in self.parent():
                 raise TypeError("'other' must live in the same algebra")
 

-            L = self.operator_matrix()
-            M = other.operator_matrix()
-            return ( L*M + M*L - (self*other).operator_matrix() )
+            L = self.operator()
+            M = other.operator()
+            return ( L*M + M*L - (self*other).operator() )

 
 
         def span_of_powers(self):
 
 
         def span_of_powers(self):