One new paper finds a new form of significant tension between astronomy observations and the ΛCDM model.
We present the first measurement of the Weyl potential at four redshifts bins using data from the first three years of observations of the Dark Energy Survey (DES). The Weyl potential, which is the sum of the spatial and temporal distortions of the Universe's geometry, provides a direct way of testing the theory of gravity and the validity of the ΛCDM model. We find that the measured Weyl potential is 2.3σ, respectively 3.1σ, below the ΛCDM predictions in the two lowest redshift bins. We show that these low values of the Weyl potential are at the origin of the σ8 tension between Cosmic Microwave Background (CMB) measurements and weak lensing measurements. Interestingly, we find that the tension remains if no information from the CMB is used. DES data on their own prefer a high value of the primordial fluctuations, followed by a slow evolution of the Weyl potential. A remarkable feature of our method is that the measurements of the Weyl potential are model-independent and can therefore be confronted with any theory of gravity, allowing efficient tests of models beyond General Relativity.
Isaac Tutusaus, Camille Bonvin, Nastassia Grimm, "First measurement of the Weyl potential evolution from the Year 3 Dark Energy Survey data: Localising the σ8 tension" arXiv:2312.06434 (December 11, 2023).
The other new paper proposes a new gravitational theory to explain dark matter phenomena, by emphasizing Mach's principle, which is the idea that inertia is due to the cumulative gravitational pull of everything in the universe on massive objects.
The general theory of relativity (GR) has excelled in explaining gravitational phenomena at the scale of the solar system with remarkable precision. However, when extended to the galactic or cosmological scale, it requires dark matter and dark energy to explain observations. In our previous article arXiv:2308.04503, we've formulated a gravity theory based in Mach's principle, known as Machian gravity. We demonstrated that the theory successfully explains galactic velocity profiles without requiring additional dark matter components. In previous studies, for a selected set of galaxy clusters, we also showed its ability to explain the velocity dispersion in the clusters without extra unseen matter components. This paper primarily explores the mass profiles of galaxy clusters. We test the Machian Gravity acceleration law on two distinct sets comprising approximately 150 galaxy clusters sourced from various studies. We fitted the dynamic mass profiles using the Machian gravity model. The outcomes of our study show exceptional agreement between the theory and observational results.
Santanu Das, "Aspects of Machian Gravity (III): Testing Theory against Galaxy Cluster mass" arXiv:2312.06312 (December 11, 2023).
Somewhat concerning that the Machian Gravity III paper (and I and II as well) are not cited by any other papers. That said, the use of Mach's principle is intriguing.
ReplyDeletearXiv:2312.08811 (gr-qc)
ReplyDelete[Submitted on 14 Dec 2023]
Theoretically motivated dark electromagnetism as the origin of relativistic MOND
Felix Finster, J. M. Isidro, Claudio F. Paganini, Tejinder P. Singh
The present paper is a modest attempt to initiate the research program outlined in this abstract. We propose that general relativity and relativistic MOND (RelMOND) are analogues of the broken electroweak symmetry. That is, SU(2)R×U(1)YDEM→U(1)DEM (DEM stands for dark electromagnetism), and GR is assumed to arise from the broken SU(2)R symmetry, and is analogous to the weak force. RelMOND is identified with dark electromagnetism U(1)DEM, which is the remaining unbroken symmetry after spontaneous symmetry breaking of the darkelectro-grav sector SU(2)R×U(1)YDEM. This sector, as well as the electroweak sector, arise from the breaking of an E8×E8 symmetry, in a recently proposed model of unification of the standard model with pre-gravitation, this latter being an SU(2)R gauge theory. The source charge for the dark electromagnetic force is square-root of mass, motivated by the experimental fact that the square-roots of the masses of the electron, up quark, and down quark, are in the ratio 1:2:3, which is a flip of their electric charge ratios 3:2:1 The introduction of the dark electromagnetic force helps understand the weird mass ratios of the second and third generation of charged fermions. We also note that in the deep MOND regime, acceleration is proportional to square-root of mass, which motivates us to propose the relativistic U(1)DEM gauge symmetry as the origin of MOND. We explain why the dark electromagnetic force falls inversely with distance, as in MOND, and not as the inverse square of distance. We conclude that dark electromagnetism is a good mimicker of cold dark matter, and the two are essentially indistinguishable in those cosmological situations where CDM is successful in explaining observations, such as CMB anisotropies, and gravitational lensing.
Comments: 44 pages
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph)
Cite as: arXiv:2312.08811 [gr-qc]
@neo I saw it and wasn't very excited.
ReplyDelete