Ocean of Currents: Why the Universe's Acceleration Varies with Direction ✦

Original: "Comparing Hemispheres: Anisotropy in the deceleration parameter $$q_0$$"

· Mauricio Lopez-Hernandez, Josue De-Santiago

arXiv:2605.03004v1 · 2026-05-04 · CC BY 4.0 · ⏱ 1 min · Cosmology General Relativity

Analysis of 1701 supernovae from the Pantheon+ catalog shows: the apparent anisotropy of acceleration vanishes when our motion is accounted for — it's a consequence of cosmic currents, not a violation of the cosmological principle.

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We fly through space at breathtaking speed, and this flight distorts measurements of the Universe's acceleration — as if a river's current changed the apparent slope of the bottom. Data from 1701 supernovae showed: accurately subtract your own velocity, and the anisotropy vanishes. But a mysterious "underwater flow" of galaxies remains — its nature is still unclear. Future surveys will help distinguish illusion from real cosmological asymmetry.

🎯 The Solar System races through the cosmic microwave background at 370 km/s — over 1.3 million km/h! No human-made object comes close to this speed. Until we account for this "tailwind," our cosmological map will be distorted.

🎬 In Liu Cixin's novel "The Dark Forest," the universe is full of hidden structures. Our research echoes this idea: the apparent asymmetry may be not just noise, but a key to invisible cosmic currents.

q_0 = -\frac{\ddot{a}a}{\dot{a}^2}\Big|_{t_0}

The deceleration parameter today: a negative value means the Universe's expansion is accelerating.

\Delta q_0(\hat{n}) = q_0(\hat{n}) - q_0(-\hat{n})

Measure of anisotropy: the difference in q0 between two hemispheres of the sky. A non-zero average indicates a dipole asymmetry.

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Ocean of Currents: Why the Universe's Acceleration Varies with Direction ✦