From: Michael Orlitzky <michael@orlitzky.com>
Date: Tue, 15 Oct 2019 12:23:10 +0000 (-0400)
Subject: eja: simplify the algebra charpoly method a bit.
X-Git-Url: http://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=04f4cf9128e6cad289e78845de177e7b1f7fca6d;p=sage.d.git

eja: simplify the algebra charpoly method a bit.
---

diff --git a/mjo/eja/eja_algebra.py b/mjo/eja/eja_algebra.py
index 56be0fa..725cd71 100644
--- a/mjo/eja/eja_algebra.py
+++ b/mjo/eja/eja_algebra.py
@@ -251,7 +251,10 @@ class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule):
         """
         (A_of_x, x, xr, detA) = self._charpoly_matrix_system()
         R = A_of_x.base_ring()
-        if i >= self.rank():
+
+        if i == self.rank():
+            return R.one()
+        if i > self.rank():
             # Guaranteed by theory
             return R.zero()
 
@@ -378,8 +381,8 @@ class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule):
         r = self.rank()
         n = self.dimension()
 
-        # The list of coefficient polynomials a_1, a_2, ..., a_n.
-        a = [ self._charpoly_coeff(i) for i in range(n) ]
+        # The list of coefficient polynomials a_0, a_1, a_2, ..., a_n.
+        a = [ self._charpoly_coeff(i) for i in range(r+1) ]
 
         # We go to a bit of trouble here to reorder the
         # indeterminates, so that it's easier to evaluate the
@@ -391,17 +394,6 @@ class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule):
         S = PolynomialRing(S, R.variable_names())
         t = S(t)
 
-        # Note: all entries past the rth should be zero. The
-        # coefficient of the highest power (x^r) is 1, but it doesn't
-        # appear in the solution vector which contains coefficients
-        # for the other powers (to make them sum to x^r).
-        if (r < n):
-            a[r] = 1 # corresponds to x^r
-        else:
-            # When the rank is equal to the dimension, trying to
-            # assign a[r] goes out-of-bounds.
-            a.append(1) # corresponds to x^r
-
         return sum( a[k]*(t**k) for k in xrange(len(a)) )