implosive-backreaction-utac

GenesisAeon Package 98 — cosmological backreaction as a falsifiable mechanism for late-time acceleration without fundamental dark energy. Distinct from implosive-genesis (P73) and implosive-origin-utac (P33) — see DISCLAIMER.md.

What's real here

• Buchert (2000, General Relativity and Gravitation): the averaged Einstein equations for irrotational dust, and the kinematical backreaction term Q_D = variance(expansion) − 2·shear².
• Raesaenen (2004, JCAP): the wall/void two-region toy model this package implements as wall_void_backreaction().
• Wiltshire (2007, PRL): Timescape cosmology, the exact two-scale Buchert average this package's BuchertScalingModel is consistent with.
• Israel & Stewart (1979, Annals of Physics): the causal theory behind the effective-viscosity mechanism (ViscousBackreaction).
• A proven No-Go for the naive reading ("distributed matter alone accelerates the universe") — deliberately included, see DISCLAIMER.md for why this doesn't refute the actual mechanism.
• Green & Wald's (2011) counter-position — that small-scale inhomogeneities don't produce relevant backreaction — represented honestly as an open dispute, not omitted.

Quickstart

pip install implosive-backreaction-utac

from implosive_backreaction_utac import (
    naive_hypothesis_accelerates,   # the No-Go: False for realistic G_eff(a)
    wall_void_backreaction,         # Q_D from regional expansion-rate variance
    BuchertScalingModel,            # power-law closure, w_X, transition redshift
    ViscousBackreaction,            # closed-form H(a), q(a) -> -1 at late times
    compare_models,                 # q(a)/w_eff(a) side by side vs LambdaCDM
)

print(naive_hypothesis_accelerates(s=0.2))  # False -- the naive reading fails

q_d = wall_void_backreaction(f_v=0.8, h_v=1.4, h_w=0.6)
model = BuchertScalingModel(q0=q_d, n=-0.5)
print(model.w_x)  # -5/6: a dynamical, accelerating effective fluid

viscous = ViscousBackreaction(zeta=0.05, g_newton=1.0, h0=1.0)
print(viscous.q(a=100.0))  # approaches -1: late-time acceleration

Development

pip install -e ".[dev]"
pre-commit install
ruff check src tests
mypy src
pytest

Citation

See CITATION.cff and .zenodo.json.