Diagram To Expression

Feynman Builder

Build standard Feynman diagram topologies, label their momenta and couplings, and convert the picture into the corresponding symbolic amplitude structure.

What This Tool Does

All diagram construction tools are available to every learner, including custom topologies and symbolic amplitude generation.

Builder Controls

Choose a preset or switch to custom mode to build your own diagram.

Topology / mode

A four-point contact diagram for a scalar theory with a quartic interaction.

Coupling symbol

Incoming 1

Incoming 2

Outgoing 1

Outgoing 2

Channel / internal label

Loop momentum

This builder generates standard symbolic amplitude skeletons for common pedagogical topologies.

Scalar

Scalar Contact Interaction

Tree-level 2 → 2 scattering through a single quartic vertex

Topology: contact

Generated Expression

Symbolic amplitude skeleton in LaTeX form

i\lambda

Mapping

How the picture becomes algebra

Each vertex contributes a coupling factor, such as \lambda.
Each internal line contributes a propagator denominator built from the internal momentum label.
External legs determine which spinors, polarization vectors, or scalar wavefunctions would multiply the core expression.
Loop topologies introduce momentum integrals and, in fermion loops, traces over gamma-matrix structure.
Hover a vertex or propagator in the diagram to see its local algebraic contribution.