  We probe the pure Einstein's gravity contributions to the second-order
density power spectrum. In the small-scale, we discover that the Einstein's
gravity contribution is negligibly small. This guarantees that Newton's gravity
is sufficient to handle the baryon acoustic oscillation scale. In the large
scale, however, we discover that the Einstein's gravity contribution to the
second-order power spectrum dominates the linear-order power spectrum. Thus,
pure Einstein gravity contribution appearing in the third-order perturbation
leads to an infrared divergence in the power spectrum.
