- added Clifford contractions:

[ginac.git] / ginac / clifford.cpp

diff --git a/ginac/clifford.cpp b/ginac/clifford.cpp
index 94f434a7710da07db1625332d7fae96b8968c095..c1c069dcb0ff8d0723048f91d0bcfec601804a4c 100644 (file)
--- a/ginac/clifford.cpp
+++ b/ginac/clifford.cpp
@@ -117,15 +117,40 @@ bool diracgamma::contract_with(exvector::iterator self, exvector::iterator other
 
        if (is_ex_of_type(other->op(0), diracgamma)) {
 
+               ex dim = ex_to_idx(self->op(1)).get_dim();
+
                // gamma~mu*gamma.mu = dim*ONE
                if (other - self == 1) {
-                       *self = ex_to_idx(self->op(1)).get_dim();
+                       *self = dim;
                        *other = dirac_one();
                        return true;
 
                // gamma~mu*gamma~alpha*gamma.mu = (2-dim)*gamma~alpha
-               } else if (other - self == 2) {
-                       *self = 2 - ex_to_idx(self->op(1)).get_dim();
+               } else if (other - self == 2
+                       && is_ex_of_type(self[1], clifford)) {
+                       *self = 2 - dim;
+                       *other = _ex1();
+                       return true;
+
+               // gamma~mu*gamma~alpha*gamma~beta*gamma.mu = 4*g~alpha~beta+(dim-4)*gamam~alpha*gamma~beta
+               } else if (other - self == 3
+                       && is_ex_of_type(self[1], clifford)
+                       && is_ex_of_type(self[2], clifford)) {
+                       *self = 4 * metric_tensor(self[1].op(1), self[2].op(1)) * dirac_one() + (dim - 4) * self[1] * self[2];
+                       self[1] = _ex1();
+                       self[2] = _ex1();
+                       *other = _ex1();
+                       return true;
+
+               // gamma~mu*gamma~alpha*gamma~beta*gamma~delta*gamma.mu = -2*gamma~delta*gamma~beta*gamma~alpha+(4-dim)*gamma~alpha*gamma~beta*gamma~delta
+               } else if (other - self == 4
+                       && is_ex_of_type(self[1], clifford)
+                       && is_ex_of_type(self[2], clifford)
+                       && is_ex_of_type(self[3], clifford)) {
+                       *self = -2 * self[3] * self[2] * self[1] + (4 - dim) * self[1] * self[2] * self[3];
+                       self[1] = _ex1();
+                       self[2] = _ex1();
+                       self[3] = _ex1();
                        *other = _ex1();
                        return true;
                }