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diff --git a/doc/models.rst b/doc/models.rst new file mode 100644 index 0000000..aa80ee6 --- /dev/null +++ b/doc/models.rst @@ -0,0 +1,61 @@ + +**************** +Defining a Model +**************** + +To define your own model, you need a class for spin states, a class for spin transformations, a bond and site coupling, and a generator of transformations. + +Spin States +=========== + +.. cpp:class:: X_t + + The spin type, which we have been denoting with :cpp:class:`X_t`, only needs to have a default constructor. If your spins can take only finitely many values, consider following the instructions in :ref:`finite_states` to significantly speed the algorithm. + +Transformations +=============== + +.. cpp:class:: R_t + + The transformation type must have a default constructor, and the following member functions: + + .. cpp:function:: X_t act(const X_t&) + + The action of the transformation on a spin, returning the transformed spin. + + .. cpp:function:: R_t act(const R_t&) + + The action of the transformation on another transformation, returning the transformed transformation. + + .. cpp:function:: X_t act_inverse(const X_t&) + + The action of the inverse transformation on a spin, returning the transformed spin. + + .. cpp:function:: R_t act_inverse(const R_t&) + + The action of the inverse transformation on another transformation, returning the transformed transformation. + +Couplings +========= + +When a :cpp:class:`system` object is initialized it needs to be given a bond and field coupling, to resemble the Hamiltonian + +.. math:: + \mathcal H = -\sum_{\langle ij\rangle}Z(s_i,s_j)-\sum_iB(s_i) + +Note that building with certain compile flags will change the form that these coupling functions must take, as outlined in :ref:`compile`. + +Bond Coupling +------------- + +.. cpp:function:: double Z(const X_t&, const X_t&) + + A function that takes two spins and outputs the coupling between them. For traditional spin models, this is typically something like a dot product. + +Field Coupling +-------------- + +.. cpp:function:: double B(const X_t&) + + A function that takes one spin and outputs the coupling between it and an external field. + |