PropagatorMapping

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

PropagatorMapping

class PropagatorMapping

A formal propagator permutation determined from Symanzik polynomials.

Unlike a momentum mapping, this supplies no tensor-numerator substitution or check of integration prescriptions. Signed propagator powers can be reordered; scalar numerators must first be expressed in family coordinates.

Examples

from symbolica import S, E
from symbolica.community import hepkit as hep
D, k, p, s = S("D", "k", "p", "s")
d1, d2, x1, x2 = S("d1", "d2", "x1", "x2")
kin = hep.Kinematics(D, momenta=[k, p]).with_scalar_product(p, p, s)
denominators = [kin.scalar_product(k, k), kin.scalar_product(k-p, k-p)]
family = hep.IntegralFamily([k], [p], denominators, kinematics=kin)
m2 = S("m2")
denominators = [denominators[0] - m2, denominators[1]]
source = hep.IntegralFamily([k], [p], denominators, kinematics=kin)
target = hep.IntegralFamily([k], [p], list(reversed(denominators)), kinematics=kin)
mapping = source.parametric_mapping(target, [x1, x2])
assert mapping is not None
target_powers = mapping.map_powers([1, 2])
assert target_powers == [2, 1]

Attributes

Name	Description
denominator_map	Zero-based target denominator index for each source denominator.

denominator_map

PropagatorMapping.denominator_map: builtins.list[builtins.int]

Zero-based target denominator index for each source denominator.

Examples

Using the setup in the PropagatorMapping class example:

slot_map = mapping.denominator_map
mapped_powers = mapping.map_powers([1, 2])

Methods

Name	Description
map_powers	Reorder signed propagator powers into target-family order.

map_powers

PropagatorMapping.map_powers(powers: typing.Sequence[builtins.int]) -> builtins.list[builtins.int]

Reorder signed propagator powers into target-family order.

Examples

Using the setup in the PropagatorMapping class example:

reordered = mapping.map_powers([1, -2])

Parameters

• powers (list[int]) One signed power per source denominator.