Model 1: A Hypothetical Rotational Mechanism for Cosmic Acceleration Following a Primordial Inter-Universe Collision

The accelerated expansion of the Universe is a central result of modern observational cosmology. Within the standard ΛCDM framework, late-time acceleration is represented by a cosmological constant or a dark-energy component, although the underlying physical interpretation of dark energy remains unresolved. This paper presents Model 1, a speculative and falsifiable hypothesis in which the observable Universe is assumed to be part of an eternal cosmological setting and may have acquired a weak global rotational component through an ancient off-center interaction with another universe or cosmological domain. The model asks whether such an interaction could transfer angular momentum and whether the resulting rotation could contribute to the observed expansion dynamics. A phenomenological rotational term is introduced only as an illustrative parameterization; it is not claimed here to be a derivation from the Einstein field equations. The Boötes Void is treated as a focused observational test case because its very large, strongly underdense character, together with features reported around the depleted redshift interval in the original discovery data, is qualitatively compatible with a generic matter-redistribution picture. That resemblance is not treated as evidence for a collision, because standard gravitational void evolution can also evacuate matter from underdense regions and build surrounding walls and filaments. The principal tests of the model are therefore quantitative: a relativistic derivation of the rotational dynamics, compatibility with strong observational limits on cosmic anisotropy and vorticity, reproduction of the observed expansion history, and numerical predictions that can be distinguished from standard structure formation. At its present stage, Model 1 should be regarded as a conceptual research hypothesis rather than an established alternative to ΛCDM.