A zero-nonmetricity branch supporting positive-pressure plane-symmetric slabs in quadratic f(Q) gravity A numerical construction with shell-free vacuum matching

This preprint examines the zero-nonmetricity vacuum branch of static, plane-symmetric, constant-density slabs in quadratic symmetric teleparallel gravity, (f(Q)=Q+\alpha Q^2).

For positive quadratic coupling, an existing exclusion argument applies to the nonzero vacuum root (Q_0=-1/(3\alpha)). We construct a finite positive-pressure slab using the alternative root (Q_0=0).

At (\alpha=0.1), the numerical solution has thickness approximately 0.82546098 and maximum pressure approximately 0.04921746, in the stated dimensionless units. The interior matches Taub and Rindler vacuum exteriors under the examined shell-free junction conditions.

The accompanying archive provides source code, independent numerical cross-checks, a self-contained Google Colab notebook, and reproducibility outputs.

This is a theoretical numerical construction, not observational evidence or a peer-reviewed discovery. Exhaustive literature priority has not been established.

AI-assisted research disclosure: Generative AI tools, including ChatGPT, Claude and Gemini, assisted substantially with mathematical derivations, code development, literature analysis, manuscript drafting, and technical review. The named human author directed the investigation and executed the reproduction notebook in Google Colab. Responsibility for the deposited work rests with the author.