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#include "Cleanup.hh"
#include "algorithms/expand_diracbar.hh"
#include "properties/DiracBar.hh"
#include "properties/Spinor.hh"
#include "properties/GammaMatrix.hh"
using namespace cadabra;
expand_diracbar::expand_diracbar(const Kernel& k, Ex& e)
: Algorithm(k, e)
{
}
bool expand_diracbar::can_apply(iterator it)
{
const DiracBar *db=kernel.properties.get<DiracBar>(it);
if(db) {
if(*tr.begin(it)->name=="\\prod") {
sibling_iterator ch=tr.begin(tr.begin(it));
const GammaMatrix *gam=kernel.properties.get<GammaMatrix>(ch);
if(gam) {
++ch;
const Spinor *sp=kernel.properties.get<Spinor>(ch);
if(sp && ++ch==tr.end(tr.begin(it))) return true;
}
}
}
return false;
}
Algorithm::result_t expand_diracbar::apply(iterator& it)
{
// \bar{\prod{\gamma_{a b} \epsilon}} -> \prod{\bar{\epsilon} \gamma_{a b}}
sibling_iterator prodnode=tr.begin(it);
sibling_iterator gamnode =tr.begin(prodnode);
sibling_iterator spinnode=gamnode;
++spinnode;
iterator newprod=tr.wrap(it, str_node("\\prod"));
multiply(newprod->multiplier, *prodnode->multiplier);
multiply(newprod->multiplier, *it->multiplier);
one(prodnode->multiplier);
one(it->multiplier);
tr.move_after(it, (iterator)gamnode);
tr.flatten(prodnode);
tr.erase(prodnode);
// n + (n-1) + .. 1 = 1/2 n (n+1) signs, of which the first 'n' are Minkowski.
unsigned int n=tr.number_of_children(gamnode);
if(n*(n+1)/2 % 2 != 0)
flip_sign(newprod->multiplier);
it=newprod;
cleanup_dispatch(kernel, tr, it);
return result_t::l_applied;
}
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