Matchete`
Matchete`

DiagonalCoupling

DiagonalCoupling

is an option for the routine DefineCoupling. Its value must be a list of booleans or empty and specifies which flavor indices of the coupling should be considered as corresponding to a diagonal tensor structure.

DiagonalCoupling

is also the corresponding key in the association returned by GetCouplings[].

Details and Options

  • Allowed values are a list of booleans or an empty list. The n-th boolean specifies whether the n-th flavor index is a diagonal in flavor space. By default all flavor indices are assumed to be non-diagonal. DiagonalCoupling is also the corresponding key in the association returned by GetCouplings[].

Examples

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Basic Examples  (1)

Defining a flavor index type:

Defining a flavored scalar field:

Define a flavor non-universal but diagonal mass matrix:

In this case the dummy index resummation by RelabelIndices ignores these indices when determining all contracted indices. However, a proper relabeling is still guaranteed.

If the mass is defined without specifying the DiagonalCoupling options (default), or equivalently using DiagonalCoupling{False}, the dummy index resummation is trying to interpret relabel the indices on the coupling as regular indices and an error message is generated in the example above:

One can also obtain the information about all DiagonalCoupling definitions before using:

Scope  (1)

One can use this option also for multiple indices and each index is individually treated as either belonging to a diagonal tensor structure or not: