/*
 * Redberry: symbolic tensor computations.
 *
 * Copyright (c) 2010-2015:
 *   Stanislav Poslavsky   
 *   Bolotin Dmitriy       
 *
 * This file is part of Redberry.
 *
 * Redberry 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.
 *
 * Redberry 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 Redberry. If not, see .
 */

package cc.redberry.physics.oneloopdiv;

import cc.redberry.core.indices.IndexType;
import cc.redberry.core.tensor.Expression;
import cc.redberry.core.tensor.Tensors;

/**
 * @author Dmitry Bolotin
 * @author Stanislav Poslavsky
 */
public final class OneLoopUtils {

    private OneLoopUtils() {
    }

    private static Expression[] antiDeSitterBackground = {
            Tensors.parseExpression("R_{lmab} = (1/3)*(g_{lb}*g_{ma}-g_{la}*g_{mb})*La"),
            Tensors.parseExpression("R_{lm} = -g_{lm}*La")
    };

    /**
     * This method return the definition of the anti de Sitter background,
     * with the cosmological constant denoted as {@code La}. In other words
     * it returns the following two substitutions:
     * 
     *     Tensors.parseExpression("R_{lmab} = (1/3)*(g_{lb}*g_{ma}-g_{la}*g_{mb})*La");
     *     Tensors.parseExpression("R_{lm} = -g_{lm}*La");
     * 
     *
     * @return the definition of the anti de Sitter background, with the
     * cosmological constant denoted as {@code La}.
     */
    public static Expression[] antiDeSitterBackground() {
        return antiDeSitterBackground.clone();
    }

    public static void setUpRiemannSymmetries() {
        Tensors.addSymmetry("R_lm", IndexType.LatinLower, false, new int[]{1, 0});
        Tensors.addSymmetry("R_lmab", IndexType.LatinLower, true, new int[]{0, 1, 3, 2});
        Tensors.addSymmetry("R_lmab", IndexType.LatinLower, false, new int[]{2, 3, 0, 1});


    }
}