Line data Source code
1 0 : // Distributed under the MIT License.
2 : // See LICENSE.txt for details.
3 :
4 : #pragma once
5 :
6 : #include <limits>
7 : #include <pup.h>
8 :
9 : #include "DataStructures/DataVector.hpp"
10 : #include "DataStructures/Tensor/Tensor.hpp"
11 : #include "Options/String.hpp"
12 : #include "PointwiseFunctions/ScalarTensor/ScalarGaussBonnet/CouplingFunctions/CouplingFunction.hpp"
13 : #include "Utilities/Gsl.hpp"
14 : #include "Utilities/Serialization/CharmPupable.hpp"
15 : #include "Utilities/TMPL.hpp"
16 :
17 : namespace ScalarTensor::sgb::CouplingFunctions {
18 :
19 : /*!
20 : * \brief Coupling function of polynomial type with degree up to four:
21 : * \f$F[\Psi] = \sum_{i = 1}^4 a_i \Psi^i\f$.
22 : *
23 : * \details This expression can be used to model the weak-field limit of a
24 : * generic coupling. Also, by appropriately setting the values of the
25 : * coefficients \f$a_i\f$ it can be used to study different phenomenological
26 : * scenario. For example, the theory admits the Kerr metric with vanishing
27 : * scalar field as a stationary solution in the case \f$a_1 = 0\f$, and can
28 : * feature spontanous scalarization for sufficiently large values of \f$a_2\f$.
29 : * Furthermore, if \f$a_2 = 0\f$, the theory can feature nonlinear
30 : * scalarization. See \cite Doneva:2022ewd for a review on spontanous
31 : * scalarization.
32 : */
33 1 : class QuarticPolynomial : public CouplingFunction {
34 : public:
35 0 : static constexpr Options::String help = {
36 : "Coupling function of polynomial type with degree up to four"};
37 :
38 0 : struct Linear {
39 0 : using type = double;
40 0 : static constexpr Options::String help = {
41 : "Coefficient of the linear term in the scalar field"};
42 : };
43 :
44 0 : struct Quadratic {
45 0 : using type = double;
46 0 : static constexpr Options::String help = {
47 : "Coefficient of the quadratic term in the scalar field"};
48 : };
49 :
50 0 : struct Cubic {
51 0 : using type = double;
52 0 : static constexpr Options::String help = {
53 : "Coefficient of the cubic term in the scalar field"};
54 : };
55 :
56 0 : struct Quartic {
57 0 : using type = double;
58 0 : static constexpr Options::String help = {
59 : "Coefficient of the quartic term in the scalar field"};
60 : };
61 :
62 0 : using options = tmpl::list<Linear, Quadratic, Cubic, Quartic>;
63 :
64 0 : QuarticPolynomial() = default;
65 0 : QuarticPolynomial(double linear, double quadratic, double cubic,
66 : double quartic);
67 0 : QuarticPolynomial(const QuarticPolynomial&) = default;
68 0 : QuarticPolynomial& operator=(const QuarticPolynomial&) = default;
69 0 : QuarticPolynomial(QuarticPolynomial&&) = default;
70 0 : QuarticPolynomial& operator=(QuarticPolynomial&&) = default;
71 0 : ~QuarticPolynomial() override = default;
72 :
73 0 : explicit QuarticPolynomial(CkMigrateMessage* m) : CouplingFunction(m) {}
74 0 : WRAPPED_PUPable_decl_template(QuarticPolynomial);
75 0 : void pup(PUP::er& p) override;
76 :
77 0 : double get_linear() const { return linear_; }
78 0 : double get_quadratic() const { return quadratic_; }
79 0 : double get_cubic() const { return cubic_; }
80 0 : double get_quartic() const { return quartic_; }
81 :
82 : protected:
83 : /*!
84 : * \brief Specialization of the function that evaluates the coupling function
85 : * on a scalar field profile.
86 : *
87 : * It returns the profile
88 : * \f$F[\Psi] = a_1 \Psi + a_2 \Psi^2 + a_3 \Psi^3 + a_4 \Psi^4\f$.
89 : */
90 1 : void coupling_function_impl(
91 : gsl::not_null<Scalar<DataVector>*> function_values,
92 : const Scalar<DataVector>& scalar_field) const override;
93 :
94 : /*!
95 : * \brief Specialization of the function that evaluates the first functional
96 : * derivative of the coupling function on a scalar field profile.
97 : *
98 : * It returns the profile
99 : * \f$\frac{\delta F[\Psi]}{\delta \Psi} = a_1 + 2 a_2 \Psi + 3 a_3 \Psi^2
100 : * + 4 a_4 \Psi^3\f$.
101 : */
102 1 : void coupling_function_prime_impl(
103 : gsl::not_null<Scalar<DataVector>*> function_values,
104 : const Scalar<DataVector>& scalar_field) const override;
105 :
106 : /*!
107 : * \brief Specialization of the function that evaluates the second functional
108 : * derivative of the coupling function on a scalar field profile.
109 : *
110 : * It returns the profile
111 : * \f$\frac{\delta^2 F[\Psi]}{\delta \Psi^2} = 2 a_2 + 6 a_3 \Psi
112 : * + 12 a_4 \Psi^2\f$.
113 : */
114 1 : void coupling_function_prime_prime_impl(
115 : gsl::not_null<Scalar<DataVector>*> function_values,
116 : const Scalar<DataVector>& scalar_field) const override;
117 :
118 : private:
119 : /*!
120 : * \brief Coefficient of the term linear in the scalar field, \f$a_1\f$.
121 : */
122 1 : double linear_{std::numeric_limits<double>::signaling_NaN()};
123 :
124 : /*!
125 : * \brief Coefficient of the term quadratic in the scalar field, \f$a_2\f$.
126 : */
127 1 : double quadratic_{std::numeric_limits<double>::signaling_NaN()};
128 :
129 : /*!
130 : * \brief Coefficient of the term cubic in the scalar field, \f$a_3\f$.
131 : */
132 1 : double cubic_{std::numeric_limits<double>::signaling_NaN()};
133 :
134 : /*!
135 : * \brief Coefficient of the term quartic in the scalar field, \f$a_4\f$.
136 : */
137 1 : double quartic_{std::numeric_limits<double>::signaling_NaN()};
138 : };
139 :
140 : } // namespace ScalarTensor::sgb::CouplingFunctions
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