scholarly journals Scale-invariant dynamics of galaxies, MOND, dark matter, and the dwarf spheroidals

2019 ◽  
Vol 492 (2) ◽  
pp. 2698-2708 ◽  
Author(s):  
Andre Maeder ◽  
Vesselin G Gueorguiev
Keyword(s):  
Dark Matter ◽  
Gravitational Acceleration ◽  
Baryonic Matter ◽  
Scale Invariant ◽  
Radial Acceleration ◽  
Horizontal Asymptote ◽  
Dynamical Properties ◽  
Dwarf Spheroidals ◽  
Dynamics Of Galaxies ◽  
The Relationship

ABSTRACT The Scale-Invariant Vacuum (SIV) theory is based on Weyl’s Integrable Geometry, endowed with a gauge scalar field. The main difference between MOND and the SIV theory is that the first considers a global dilatation invariance of space and time, where the scale factor λ is a constant, while the second opens the likely possibility that λ is a function of time. The key equations of the SIV framework are used here to study the relationship between the Newtonian gravitational acceleration due to baryonic matter gbar and the observed kinematical acceleration gobs. The relationship is applied to galactic systems of the same age where the radial acceleration relation (RAR), between the gobs and gbar accelerations, can be compared with observational data. The SIV theory shows an excellent agreement with observations and with MOND for baryonic gravities gbar > 10−11.5 m s−2. Below this value, SIV still fully agrees with the observations, as well as with the horizontal asymptote of the RAR for dwarf spheroidals, while this is not the case for MOND. These results support the view that there is no need for dark matter and that the RAR and related dynamical properties of galaxies can be interpreted by a modification of gravitation.

scholarly journals The redshift-dependence of radial acceleration: Modified gravity versus particle dark matter

2018 ◽  
Vol 27 (14) ◽  
pp. 1847010 ◽  
Author(s):  
Sabine Hossenfelder ◽  
Tobias Mistele
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Free Parameter ◽  
Galactic Rotation ◽  
Gravitational Acceleration ◽  
Baryonic Matter ◽  
Interpolation Function ◽  
Rotation Curves ◽  
Radial Acceleration ◽  
Particle Dark Matter

Modified Newtonian Dynamics has one free parameter and requires an interpolation function to recover the normal Newtonian limit. We here show that this interpolation function is unnecessary in a recently proposed covariant completion of Erik Verlinde’s emergent gravity, and that Verlinde’s approach moreover fixes the function’s one free parameter. The so-derived correlation between the observed acceleration (inferred from rotation curves) and the gravitational acceleration due to merely the baryonic matter fits well with data. We then argue that the redshift-dependence of galactic rotation curves could offer a way to tell apart different versions of modified gravity from particle dark matter.

scholarly journals The weak lensing radial acceleration relation: Constraining modified gravity and cold dark matter theories with KiDS-1000

2021 ◽  
Vol 650 ◽  
pp. A113
Author(s):  
Margot M. Brouwer ◽  
Kyle A. Oman ◽  
Edwin A. Valentijn ◽  
Maciej Bilicki ◽  
Catherine Heymans ◽  
...  
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Modified Gravity ◽  
Cold Dark Matter ◽  
Weak Lensing ◽  
Mass Relation ◽  
Gravitational Acceleration ◽  
Radial Acceleration ◽  
The Galaxy ◽  
The Difference

We present measurements of the radial gravitational acceleration around isolated galaxies, comparing the expected gravitational acceleration given the baryonic matter (gbar) with the observed gravitational acceleration (gobs), using weak lensing measurements from the fourth data release of the Kilo-Degree Survey (KiDS-1000). These measurements extend the radial acceleration relation (RAR), traditionally measured using galaxy rotation curves, by 2 decades in gobs into the low-acceleration regime beyond the outskirts of the observable galaxy. We compare our RAR measurements to the predictions of two modified gravity (MG) theories: modified Newtonian dynamics and Verlinde’s emergent gravity (EG). We find that the measured relation between gobs and gbar agrees well with the MG predictions. In addition, we find a difference of at least 6σ between the RARs of early- and late-type galaxies (split by Sérsic index and u − r colour) with the same stellar mass. Current MG theories involve a gravity modification that is independent of other galaxy properties, which would be unable to explain this behaviour, although the EG theory is still limited to spherically symmetric static mass models. The difference might be explained if only the early-type galaxies have significant (Mgas ≈ M⋆) circumgalactic gaseous haloes. The observed behaviour is also expected in Λ-cold dark matter (ΛCDM) models where the galaxy-to-halo mass relation depends on the galaxy formation history. We find that MICE, a ΛCDM simulation with hybrid halo occupation distribution modelling and abundance matching, reproduces the observed RAR but significantly differs from BAHAMAS, a hydrodynamical cosmological galaxy formation simulation. Our results are sensitive to the amount of circumgalactic gas; current observational constraints indicate that the resulting corrections are likely moderate. Measurements of the lensing RAR with future cosmological surveys (such as Euclid) will be able to further distinguish between MG and ΛCDM models if systematic uncertainties in the baryonic mass distribution around galaxies are reduced.

scholarly journals Understanding the large inferred Einstein radii of observed low-mass galaxy clusters

2020 ◽  
Vol 494 (4) ◽  
pp. 4706-4712 ◽  
Author(s):  
Andrew Robertson ◽  
Richard Massey ◽  
Vincent Eke
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Cold Dark Matter ◽  
Baryonic Matter ◽  
Analysis Method ◽  
Critical Curves ◽  
Hydrodynamical Simulation ◽  
Low Mass ◽  
Main Effects

ABSTRACT We assess a claim that observed galaxy clusters with mass ${\sim}10^{14} \mathrm{\, M_\odot }$ are more centrally concentrated than predicted in lambda cold dark matter (ΛCDM). We generate mock strong gravitational lensing observations, taking the lenses from a cosmological hydrodynamical simulation, and analyse them in the same way as the real Universe. The observed and simulated lensing arcs are consistent with one another, with three main effects responsible for the previously claimed inconsistency. First, galaxy clusters containing baryonic matter have higher central densities than their counterparts simulated with only dark matter. Secondly, a sample of clusters selected because of the presence of pronounced gravitational lensing arcs preferentially finds centrally concentrated clusters with large Einstein radii. Thirdly, lensed arcs are usually straighter than critical curves, and the chosen image analysis method (fitting circles through the arcs) overestimates the Einstein radii. After accounting for these three effects, ΛCDM predicts that galaxy clusters should produce giant lensing arcs that match those in the observed Universe.

scholarly journals MEASURING DARK MATTER PROFILES NON-PARAMETRICALLY IN DWARF SPHEROIDALS: AN APPLICATION TO DRACO

2013 ◽  
Vol 763 (2) ◽  
pp. 91 ◽  
Author(s):  
John R. Jardel ◽  
Karl Gebhardt ◽  
Maximilian H. Fabricius ◽  
Niv Drory ◽  
Michael J. Williams
Keyword(s):  
Dark Matter ◽  
Dwarf Spheroidals

scholarly journals Dark matter reflection of particle symmetry

2017 ◽  
Vol 32 (15) ◽  
pp. 1740001 ◽  
Author(s):  
Maxim Yu. Khlopov
Keyword(s):  
Dark Matter ◽  
Phase Transitions ◽  
Symmetry Breaking ◽  
Early Universe ◽  
Topological Defects ◽  
Elementary Particles ◽  
Nonlinear Structures ◽  
The Relationship ◽  
New Particles

In the context of the relationship between physics of cosmological dark matter and symmetry of elementary particles, a wide list of dark matter candidates is possible. New symmetries provide stability of different new particles and their combination can lead to a multicomponent dark matter. The pattern of symmetry breaking involves phase transitions in the very early Universe, extending the list of candidates by topological defects and even primordial nonlinear structures.

scholarly journals Scale-invariant models with one-loop neutrino mass and dark matter candidates

2016 ◽  
Vol 94 (5) ◽  
Author(s):  
Amine Ahriche ◽  
Adrian Manning ◽  
Kristian L. McDonald ◽  
Salah Nasri
Keyword(s):  
Dark Matter ◽  
Neutrino Mass ◽  
Scale Invariant

scholarly journals Dark Matter in the Universe

BIBECHANA ◽  
1970 ◽  
Vol 6 ◽  
pp. 27-30
Author(s):  
Devendra Adhikari ◽  
Krishna Raj Adhikari
Keyword(s):  
Dark Matter ◽  
Baryonic Matter ◽  
X Ray ◽  
Physical Phenomena ◽  
The Universe

Different physical phenomena, techniques, and evidences which give the proof for the existence of dark matter have been discussed. Keywords: Baryonic matter; dark matter; Chandra x-ray ObservatoryDOI: 10.3126/bibechana.v6i0.3936BIBECHANA Vol. 6, March 2010 pp.27-30

scholarly journals On The Symmetry of The Universe

2020 ◽  
Author(s):  
Engel Roza
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Thermodynamic Equilibrium ◽  
Vacuum Energy ◽  
Quantum Mechanical ◽  
Baryonic Matter ◽  
Time Uncertainty ◽  
Matter Effect ◽  
Mechanical Interpretation ◽  
The Universe

It is shown that the Lambda component in the cosmological Lambda-CDM model can be conceived as vacuum energy, consisting of gravitational particles subject to Heisenberg’s energy-time uncertainty. These particles can be modelled as elementary polarisable Dirac-type dipoles (“darks”) in a fluidal space at thermodynamic equilibrium, with spins that are subject to the Bekenstein-Hawking entropy. Around the baryonic kernels, uniformly distributed in the universe, the spins are polarized, thereby invoking an increase of the effective gravitational strength of the kernels. It explains the dark matter effect to the extent that the numerical value of Milgrom’s acceleration constant can be assessed by theory. Non-polarized vacuum particles beyond the baryonic kernels compose the dark energy. The result is a quantum mechanical interpretation of gravity in terms of quantitatively established shares in baryonic matter, dark matter and dark energy, which correspond with the values of the Lambda-CDM model..

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