https://doi.org/10.1140/epjc/s10052-025-14222-w
Regular Article - Theoretical Physics
Anisotropy in Pantheon+ supernovae
1
Department of High Energy Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, 400005, Mumbai, India
2
Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Parks Road, OX1 3PU, Oxford, UK
3
Section of Astrophysics, Astronomy and Mechanics, Aristotle University of Thessaloniki, 54124, Thessaloníki, Greece
4
Clare Hall, University of Cambridge, Herschel Road, CB3 9AL, Cambridge, UK
Received:
15
November
2024
Accepted:
24
April
2025
Published online:
30
May
2025
We employ maximum likelihood estimators to examine the Pantheon+ catalogue of Type Ia supernovae for large scale anisotropies in the expansion rate of the Universe. The analyses are carried out in the heliocentric frame, the CMB frame, as well as the Local Group frame. In all frames, the Hubble expansion rate in the redshift range 
is found to have a statistically significant dipolar variation exceeding 1.5 km s
Mpc, i.e. bigger than the claimed 1% uncertainty in the SH0ES measurement of the Hubble parameter 
. The deceleration parameter too has a redshift-dependent dipolar modulation at 
significance, consistent with previous findings using the SDSSII/SNLS3 Joint Lightcurve Analysis catalogue. The inferred cosmic acceleration cannot therefore be due to a cosmological constant, but is likely a general relativistic effect due to the anomalous bulk flow in our local Universe.
© The Author(s) 2025
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