Update box matrix normalization and decouple K matrix model from BoxQuantization #2
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added 4 commits
April 18, 2018 16:04
Previously the K matrix model was intertwined with the BoxQuantizationclass, e.g. fit parameters were accessed through BoxQuantization. Instead, the BoxQuantization class should not care about how a K Matrix model is implemented as long as it provides the two functions calculate(..) isZero(..) now defined pure virtual in the new KtildeMatrixBase base class. A K-matrix model is implemented by subclassing KtildeMatrixBase and providing these functions. Model parameters are handled exclusively by the K matrix model provided by the user. A BoxQuantization object is now constructed by passing in an object derived from KtildeMatrixBase and a boolean indicating whether this is a model for Ktilde or KtildeInverse. The example driver routines have been updated to reflect the changes in interface.
This change in normalization induces a change in the normalization of the Ktilde matrix to make it more natural. The difference is most easily seen by comparing eq. (2.9) of https://arxiv.org/abs/1802.03100v1 (new convention) eq. (46) of https://arxiv.org/abs/1707.05817v1 (old convention) In the old normalization, the K matrix depended on m_ref L, i.e. a finite-volume quantity. Using the new normalization, the K matrix does not pick up a dependence on any finite-volume quantity, and the Breit-Wigner parametrization takes its canonical form.
cjmorningstar10
approved these changes
Aug 30, 2018
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The commits do two things:
Decouple the implementation of a K matrix model from the BoxQuantization class, i.e. whoever wants to implement a K matrix model writes a class subclassing KtildeMatrixBase, and takes care of handling the model parameters there. BoxQuantization does not any longer loop fit parameters through to the K Matrix.
Change of normalization of the box matrix elements such that the K matrix does not depend on any finite-volume quantity anymore. Previously, the K matrix needed factors of k0 in it to make contact with the standard expressions for effective range, Breit-Wigner etc.
Some more detail on each change is provided in the commit messages.