expander.h

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// This file is part of MARTY.
//
// MARTY is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// MARTY is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with MARTY. If not, see <https://www.gnu.org/licenses/>.

#pragma once

#include "lagrangian.h"
#include "insertion.h"
#include "feynOptions.h"

namespace mty {

    class Model;
    class FeynmanDiagram;

    enum Order {
        TreeLevel,
        OneLoop
    };

    class Expander {

    public:

        Expander(
                mty::Model  const *t_model,
                FeynOptions const &t_options,
                std::vector<mty::Lagrangian::TermType> const &lagrangian,
                std::vector<mty::QuantumField>         const &t_insertions
                );

        std::vector<std::vector<size_t>> findNonZeroDiagrams();

        template<class ...Args>
        static std::vector<std::vector<size_t>> getDiagrams(
                Args &&...args
                )
        {
            Expander exp(std::forward<Args>(args)...);
            return exp.findNonZeroDiagrams();
        }

    private:

        bool contractionPossible(
                std::vector<size_t>       const &fieldPos,
                std::vector<bool>         const &insertionsPaired,
                std::vector<QuantumField> const &newFields,
                std::vector<bool>               &newPairing,
                int                              order,
                int                              maxOrder,
                size_t                           nLoops,
                size_t                           maxInteractionLegs
                );

        void addVertexCarefully(
                size_t                               iTerm,
                std::vector<size_t>           const &terms,
                std::vector<std::vector<size_t>>    &numbers,
                std::vector<std::vector<bool>>      &newPairings,
                std::vector<bool>             const &pairing,
                std::map<std::vector<size_t>, bool> &vertexMap
                );

    private:

        mty::Model  const *model;

        FeynOptions const &options;
        std::vector<mty::Lagrangian::TermType> effectiveLagrangian;
        std::vector<mty::QuantumField>         insertions;
    };

} // namespace mty