Coupling

Symbolica documentation for getting started, symbolic expressions, numerical evaluation, pattern matching, and APIs in Python and Rust.

`Coupling`

class Coupling

A coupling coefficient associated with interaction vertices.

Couplings retain their symbolic expression, perturbative coupling orders, and evaluated complex value when the model has been numerically resolved.

Examples

from symbolica import S, E
from symbolica.community import hepkit as hep
model = hep.Model.standard_model()
coupling = model.couplings[0]
orders = coupling.orders
formula = coupling.expression

Attributes

Name	Description
`expression`	Return the expression defining the coupling.
`name`	Return the coupling name.
`orders`	Return the coupling-order powers keyed by order name.
`symbol`	Return the symbolic reference used by this model’s expressions
`value`	Return the evaluated coupling as a native Python complex number

`expression`

Coupling.expression: Expression

Return the expression defining the coupling.

Examples

Using the setup in the Coupling class example:

formula = coupling.expression

`name`

Coupling.name: builtins.str

Return the coupling name.

Examples

Using the setup in the Coupling class example:

coupling_by_name = {item.name: item.expression for item in model.couplings}

`orders`

Coupling.orders: builtins.dict[builtins.str, builtins.int]

Return the coupling-order powers keyed by order name.

Examples

Using the setup in the Coupling class example:

qed_couplings = [c for c in model.couplings if c.orders.get("QED", 0) > 0]

`symbol`

Coupling.symbol: Expression

Return the symbolic reference used by this model’s expressions. This preserves the parameter or function identity without substituting its defining expression or numerical value.

Examples

from symbolica.community import hepkit as hep
model = hep.Model.standard_model()
reference = model.couplings[0].symbol

`value`

Coupling.value: complex

Return the evaluated coupling as a native Python complex number.

Raises :class:ModelError when this coupling has not been evaluated.

Examples

Using the setup in the Coupling class example:

coupling_value = model.couplings[0].value
print("coupling:", coupling_value.real, coupling_value.imag)

Methods

Name	Description
`__repr__`	Summarize the defining data as well as the coupling name.
`_repr_html_`	Display the model member’s physical data and defining expressions.
`_repr_pretty_`	Write the complete text summary to an IPython pretty printer.

`repr`

Coupling.__repr__() -> builtins.str

Summarize the defining data as well as the coupling name.

Examples

Using the setup in the Coupling class example:

print(next(c for c in model.couplings if c.orders.get("QED", 0) > 0))

`_repr_html_`

Coupling._repr_html_() -> builtins.str

Display the model member’s physical data and defining expressions.

Examples

Using the setup in the Coupling class example:

from IPython.display import display
display(coupling)

`_repr_pretty_`

Coupling._repr_pretty_(pretty: typing.Any, cycle: builtins.bool) -> None

Write the complete text summary to an IPython pretty printer.

Examples

Using the setup in the Coupling class example:

from IPython.lib.pretty import pretty
text = pretty(coupling)

Parameters

pretty (object) IPython pretty printer receiving the text.
cycle (bool) Whether the object occurs recursively in the current display.