xact-py 0.4.2

Python wrapper for xAct.jl — tensor algebra for general relativity

xact-py

Python wrapper for xAct.jl — a high-performance tensor algebra suite for general relativity.

Note: All code in this repository is generated by AI. It was built under strict engineering practices but is not warranted to be absolutely correct. See the full disclaimer.

Installation

pip install xact-py

Julia is installed automatically via juliacall.

Quick Start

import xact

xact.reset()
M = xact.Manifold("M", 4, ["a", "b", "c", "d"])
T = xact.Tensor("T", ["-a", "-b"], M, symmetry="Symmetric[{-a,-b}]")
xact.canonicalize("T[-b,-a] - T[-a,-b]")  # returns "0"

Features

• Canonicalization — Butler-Portugal algorithm for tensor index canonicalization
• Contraction & Simplification — metric contraction, iterative simplification
• Covariant Derivatives — commutation, sorting, Riemann identities
• Perturbation Theory — multinomial Leibniz expansion, curvature perturbations
• Coordinate Components (xCoba) — basis changes, Christoffel symbols, CTensor
• Riemann Invariants (xInvar) — classification and database of Riemann polynomial invariants
• Variational Calculus — Euler-Lagrange operator, integration by parts

Example: Metric and Curvature

import xact

xact.reset()
M = xact.Manifold("M", 4, ["a", "b", "c", "d", "e", "f"])
g = xact.Metric("g", ["-a", "-b"], M)

# Riemann symmetry: R_abcd + R_abdc = 0
xact.canonicalize("RiemannCD[-a,-b,-c,-d] + RiemannCD[-a,-b,-d,-c]")
# returns "0"

# Simplify a contracted Riemann expression
xact.simplify("RicciCD[-a,-b] - RiemannCD[-a,-c,-b,-d] * g[c,d]")
# returns "0"

Documentation

Full documentation at saxa.xyz/sxAct.

License

GPL-3.0 — see LICENSE.