- sage: from mjo.eja.eja_algebra import random_eja
-
- TESTS::
-
- sage: J1 = random_eja(field=QQ, orthonormalize=False)
- sage: J2 = random_eja(field=QQ, orthonormalize=False)
- sage: J = cartesian_product([J1,J2])
- sage: all( J.monomial(m)
- ....: ==
- ....: J.gens()[J._monomial_to_generator(m)]
- ....: for m in J.basis().keys() )
- True
-
- """
- # This works recursively so that we can handle Cartesian
- # products of Cartesian products.
- try:
- # monomial is an ordered pair
- factor = mon[0]
- except TypeError: # 'int' object is not subscriptable
- # base case where the monomials are integers
- return mon
-
- idx_in_factor = self._monomial_to_generator(mon[1])
-
- offset = sum( f.dimension()
- for f in self.cartesian_factors()[:factor] )
- return offset + idx_in_factor
-
- def product_on_basis(self, i, j):
- r"""
- Return the product of the monomials indexed by ``i`` and ``j``.
-
- This overrides the superclass method because here, both ``i``
- and ``j`` will be ordered pairs.
-
- SETUP::
-
- sage: from mjo.eja.eja_algebra import (HadamardEJA,
- ....: JordanSpinEJA,
- ....: QuaternionHermitianEJA,
- ....: RealSymmetricEJA,)
-
- EXAMPLES::
-
- sage: J1 = JordanSpinEJA(2, field=QQ)
- sage: J2 = RealSymmetricEJA(2, field=QQ, orthonormalize=False)
- sage: J3 = HadamardEJA(1, field=QQ)
- sage: K1 = cartesian_product([J1,J2])
- sage: K2 = cartesian_product([K1,J3])
- sage: list(K2.basis())
- [e(0, (0, 0)), e(0, (0, 1)), e(0, (1, 0)), e(0, (1, 1)),
- e(0, (1, 2)), e(1, 0)]
- sage: g = K2.gens()
- sage: (g[0] + 2*g[3]) * (g[1] - 4*g[2])
- e(0, (0, 1)) - 4*e(0, (1, 1))
-
- TESTS::
-
- sage: J1 = RealSymmetricEJA(1,field=QQ)
- sage: J2 = QuaternionHermitianEJA(1,field=QQ)
- sage: J = cartesian_product([J1,J2])
- sage: x = sum(J.gens())
- sage: x == J.one()
- True
- sage: x*x == x
- True
-
- """
- l = self._monomial_to_generator(i)
- m = self._monomial_to_generator(j)
- return FiniteDimensionalEJA.product_on_basis(self, l, m)