Dark Energy fluctuation checked

Recent tests on Dark Energy pointed to possible change of its density and produced a challenge that it was evolving over time.

This has been examined and checked by, among others, Fuyu Dong and Changbom Park. The team, in their paper, has noted previous methodology was "hampered by the non-cosmological shape distortion due to peculiar velocities of galaxies", referred to as redshift-space distortion.

To bring clarity, a modified version of the Alcock & Paczynski test is administered called the "extended Alcock & Paczynski Test" (hereafter eAP). It is "to use redshift evolution of shape rather than shape itself". They have applied the tomographic AP test to SDSS data.

"An attendant benefit of the normalizing operation is that our results become independent of the overall evolution of clustering amplitude due to gravitational evolution and change of galaxy bias in observational samples." "It is important to note that these tight constraints were resulted even though only low redshift data were used, and are independent of of the cosmic microwave background (CMB) observations."

"In combination of the constraint from the eAP test with those derived from Planck CMB, SDSS_III, BAO, JTA SNe Ia and Ho from HST Cepheids. Li et al obtained Omega m = 0.301, wo= -1.042, and wa= -0.07 (68.3% CL)."

They also note that there is evidence that the cosmology constrained by CMB data tends to be inconsistent with that from low-redshift data.

An examination by the Alcock-Paczynski method, published Oct. 28, 2025, indicates no support of the dynamic evolution of Dark Energy

"Most importantly , the AP test provides no indication of a dynamical dark energy component, with the constraint on the evolution parameter wa, being consistent with zero."

"A fatal problem with the DESI BAO result is that a flat prior [-3, 2] is applied to wa. This not only affects the pdf of wa, but also the pdfs of Omega m and wo."

[Please note here that a is  standin for the symbol alpha.

A draft version by Fuyu Dong and Changbom Park is available at Arxiv.org: 2510.24089.

Happy Halloween!

In case you don't want to believe this, there is additionally a Bayesian report:

arxiv.org: 2511.10631 by Dily Duan Yi Ong

Reviews

[miriam]

This is an exceptionally well-presented and insightful summary! You explained complex cosmological concepts—like the eAP test, redshift distortions, and dark energy constraints with clarity and precision. The way you combined technical depth with readable flow is truly impressive. Excellent work!