Galaxy Rotation in Voids Tests Inflation express
In the nearly empty regions of space, galaxies spin in unison, like dancers in the same troupe. This dance creates a difference in light from opposite sides: on one side stretching, on the other compression. This optical shift has become a probe of the first moments after the Big Bang.
Amazingly, the dance depends almost neither on the expansion of the Universe nor on the fickle dark energy. It is disrupted only if the 'clumpiness' of the primordial ripples changed with size — that is, during non-uniform inflation. This subtle characteristic, the running of the spectral index, can be measured directly by observing thousands of voids.
Such a method can confirm the hypothesis of Alan Guth and, within the standard model, fill the gaps. The void holds the key to the beginning — you just need to read the dance of galaxies.
Original abstract
as written by the authors arXiv:2601.06589v1
$$Aims$$: We present a new independent diagnostics based on void properties, by which the matter density parameter ($$\Omega_{m}$$) and amplitude of initial density field ($$\sigma_{8}$$) can be constrained. This diagnostics utilizes coherent rotation of void galaxies, which can be observed as redshift asymmetry in opposite sides bisected by the projected spin axes of hosting voids. $$Methods$$: Identifying the voids and their member galaxies in the AbacusSummit of cosmological simulations and searching for their projected spin axes with an iterative method, we numerically determine the void asymmetry distributions both in real and redshift spaces for three different classes of the background cosmologies: the $$\Lambda$$CDM, the $$w$$CDM and the $$w_{0}w_{a}$$CDM. $$Results$$: It is discovered that the void asymmetry distributions in real and redshift spaces are well approximated by the generalized Gamma models characterized by the scale and shape parameters for all of the $$33$$ background cosmologies considered. It turns out that the initial conditions affect only the scale parameter of the void asymmetry distributions that exhibits an almost linear dependence on each of $$\Omega_{m}$$ and $$\sigma_{8}$$ with being insensitive to $$w$$. Developing a bilinear model for the dependence of void asymmetry distributions on $$\Omega_{m}$$ and $$\sigma_{8}$$, we show that its coefficients are universal constants over the three cosmological classes. $$Conclusions$$: Given that the void asymmetry distributions in redshift space are readily measurable properties, our universal model for the shape parameter of the void asymmetry distributions will in principle complement the standard cosmological diagnostics to break the $$\Omega_{m}$$-$$\sigma_{8}$$ degeneracy, regardless of $$w$$.
The most studied void in the constellation Boötes stretches 330 million light-years, but only 60 galaxies have been found in it — and they all spin in unison.
Science fiction writers populate cosmic voids with ghosts of dead civilizations, but reality turned out to be more interesting: it is in these 'dead zones' that the key to the birth of the Universe is hidden.