HCSOT: Hu's Cosmic Space Origin Theory — A Unified Cosmological Framework with a Falsifiable Weak Lensing Prediction for Euclid DR1 (October 2026)

This deposit contains the definitive pre-publication version (V5.4) of Hu's Cosmic Space Origin Theory (HCSOT) — a unified cosmological framework in which the single dynamical degree of freedom is the local energy density of the spacetime substrate. Core theoretical elements locked in this version: - Four fundamental axioms (spacetime energy field, critical equilibrium density, energy-momentum conservation, cosmic relaxation) - Scalar-tensor action and field equations - Effective gravitational coupling G_eff(z) = G_N [1 + α(1 - ρ(z)/ρ_0)] - Gravitational response parameter α = 0.087 ± 0.029, calibrated from local H_0 - Quantum tunneling mechanism for primordial singularity and Big Bang onset - Planck-scale cutoff and singularity regularization - Cosmological perturbation equations and modified growth rate - Systematic comparison with ΛCDM, MOND, and quintessence frameworks Flagship falsifiable prediction: - Euclid DR1 (October 2026): +8% ± 3% (1σ) enhancement in the weak lensing matter power spectrum at k = 0.1 h/Mpc relative to ΛCDM - Validated via 10,000 Monte Carlo realizations: 99.24% strict success rate, 5.8σ statistical significance Secondary predictions: - Cluster outskirts M_dyn/M_lens systematic offset: 0.92–0.96 - Matter power spectrum slope enhancement at k = 0.05 h/Mpc: ~4–6% - Evolution of dark energy equation of state w(z) crossing w = −1 (consistent with DESI DR2) Known limitations are explicitly documented in Section 6.1, including phenomenological α, unspecified V(φ), absence of full CMB Boltzmann implementation, and strong-field/nonlinear regimes. This framework is supported by fourteen companion papers, all independently archived with Zenodo timestamps prior to the Euclid DR1 data release. This deposit is part of a pre-registered scientific forecast. The theory and core predictions contained herein were finalized and timestamped prior to the Euclid DR1 data release (October 2026). No modifications to the core predictions will be made after this date. The author will maintain public silence on this work until the Euclid DR1 results are publicly available, to ensure the integrity of the blind test. The complete executable prediction code is archived separately at Zenodo (DOI: 10.5281/zenodo.20104919). All content is licensed under CC BY 4.0.