Line data    Source code

       1           0 : // Distributed under the MIT License.
       2             : // See LICENSE.txt for details.
       3             : 
       4             : #pragma once
       5             : 
       6             : #include <cmath>
       7             : #include <cstddef>
       8             : #include <cstdint>
       9             : #include <utility>
      10             : 
      11             : #include "DataStructures/DataBox/Prefixes.hpp"
      12             : #include "DataStructures/DataBox/Tag.hpp"
      13             : #include "DataStructures/Tensor/EagerMath/DeterminantAndInverse.hpp"
      14             : #include "DataStructures/Tensor/Tensor.hpp"
      15             : #include "DataStructures/VariablesTag.hpp"
      16             : #include "NumericalAlgorithms/LinearOperators/PartialDerivatives.hpp"
      17             : #include "PointwiseFunctions/GeneralRelativity/Tags.hpp"
      18             : #include "Utilities/ContainerHelpers.hpp"
      19             : #include "Utilities/Gsl.hpp"
      20             : #include "Utilities/TMPL.hpp"
      21             : #include "Utilities/TaggedTuple.hpp"
      22             : 
      23             : /// \ingroup GeneralRelativityGroup
      24             : /// Holds functions related to general relativity.
      25             : namespace gr {
      26             : /// @{
      27             : /*!
      28             :  * \ingroup GeneralRelativityGroup
      29             :  * \brief Compute lapse from shift and spacetime metric
      30             :  *
      31             :  * \details Computes
      32             :  * \f{align}
      33             :  *    \alpha &= \sqrt{\beta^i g_{it}-g_{tt}}
      34             :  * \f}
      35             :  * where \f$ \alpha \f$, \f$ \beta^i\f$, and \f$g_{ab}\f$ are the lapse, shift,
      36             :  * and spacetime metric.
      37             :  * This can be derived, e.g., from Eqs. 2.121--2.122 of Baumgarte & Shapiro.
      38             :  */
      39             : template <typename DataType, size_t SpatialDim, typename Frame>
      40           1 : Scalar<DataType> lapse(
      41             :     const tnsr::I<DataType, SpatialDim, Frame>& shift,
      42             :     const tnsr::aa<DataType, SpatialDim, Frame>& spacetime_metric);
      43             : 
      44             : template <typename DataType, size_t SpatialDim, typename Frame>
      45           1 : void lapse(gsl::not_null<Scalar<DataType>*> lapse,
      46             :            const tnsr::I<DataType, SpatialDim, Frame>& shift,
      47             :            const tnsr::aa<DataType, SpatialDim, Frame>& spacetime_metric);
      48             : /// @}
      49             : 
      50             : namespace Tags {
      51             : /*!
      52             :  * \brief Compute item for lapse \f$\alpha\f$ from the spacetime metric
      53             :  * \f$g_{ab}\f$ and the shift \f$\beta^i\f$.
      54             :  *
      55             :  * \details Can be retrieved using `gr::Tags::Lapse`.
      56             :  */
      57             : template <typename DataType, size_t SpatialDim, typename Frame>
      58           1 : struct LapseCompute : Lapse<DataType>, db::ComputeTag {
      59           0 :   using argument_tags =
      60             :       tmpl::list<Shift<DataType, SpatialDim, Frame>,
      61             :                  SpacetimeMetric<DataType, SpatialDim, Frame>>;
      62             : 
      63           0 :   using return_type = Scalar<DataType>;
      64             : 
      65           0 :   static constexpr auto function =
      66             :       static_cast<void (*)(const gsl::not_null<Scalar<DataType>*> lapse,
      67             :                            const tnsr::I<DataType, SpatialDim, Frame>&,
      68             :                            const tnsr::aa<DataType, SpatialDim, Frame>&)>(
      69             :           &lapse<DataType, SpatialDim, Frame>);
      70             : 
      71           0 :   using base = Lapse<DataType>;
      72             : };
      73             : }  // namespace Tags
      74             : }  // namespace gr