scholarly journals Modified gravity or imperfect dark matter: a model-independent discrimination

2021 ◽  
Vol 2021 (02) ◽  
pp. 020-020
Author(s):  
Miguel Aparicio Resco ◽  
Antonio L. Maroto
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Model Independent

scholarly journals Dwarf galaxies without dark matter: constraints on modified gravity

2020 ◽  
Vol 501 (1) ◽  
pp. 254-260
Author(s):  
Ali Rida Khalifeh ◽  
Raul Jimenez
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Virial Theorem ◽  
Dwarf Galaxies ◽  
Strong Support ◽  
Gravity Models ◽  
Birkhoff Theorem ◽  
Astronomical Surveys ◽  
Stringent Test ◽  
Modified Gravity Models

ABSTRACT The discovery of 19 dwarf galaxies without dark matter (DM) provides, counterintuitively, strong support for the ΛCDM standard model of cosmology. Their presence is well accommodated in a scenario where the DM is in the form of cold dark particles. However, it is interesting to explore quantitatively what is needed from modified gravity models to accommodate the presence of these galaxies and what extra degree of freedom is needed in these models. To this end, we derive the dynamics at galaxy scales (Virial theorem) for a general class of modified gravity models. We distinguish between theories that satisfy the Jebsen–Birkhoff theorem, and those that do not. Our aim is to develop tests that can distinguish whether DM is part of the theory of gravity or a particle. The 19 dwarf galaxies discovered provide us with a stringent test for models of modified gravity. Our main finding is that there will always be an extra contribution to the Virial theorem coming from the modification of gravity, even if a certain galaxy shows very small, if not negligible, trace of DM, as has been reported recently. Thus, if these and more galaxies are confirmed as devoid (or negligible) of DM, while other similar galaxies have abundant DM, it seems interesting to find modifications of gravity to describe DM. Our result can be used by future astronomical surveys to put constraints on the parameters of modified gravity models at astrophysical scales where DM is described as such.

scholarly journals Does the Cosmological Expansion Change Local Dynamics?

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1417
Author(s):  
Marcelo Schiffer
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Hubble Constant ◽  
Matter Content ◽  
Matter Distribution ◽  
Present Value ◽  
Field Equations ◽  
Local Dynamics ◽  
Cosmological Expansion ◽  
Modified Gravity Theories

It is a well-known fact that the Newtonian description of dynamics within Galaxies for its known matter content is in disagreement with the observations as the acceleration approaches a0≈1.2×10−10 m/s2 (slighter larger for clusters). Both the Dark Matter scenario and Modified Gravity Theories (MGT) fail to explain the existence of such an acceleration scale. Motivated by the closeness of the acceleration scale and the Hubble constant cH0≈10−9 h m/s2, we are led to analyze whether this coincidence might have a Cosmological origin for scalar-tensor and spinor-tensor theories by performing detailed calculations for perturbations that represent the local matter distribution on the top of the cosmological background. Then, we solve the field equations for these perturbations in a power series in the present value of the Hubble constant. As we shall see, for both theories, the power expansion contains only even powers in the Hubble constant, a fact that renders the cosmological expansion irrelevant for the local dynamics.

scholarly journals Cosmological gravity on all scales. Part II. Model independent modified gravity N-body simulations

2021 ◽  
Vol 2021 (06) ◽  
pp. 016
Author(s):  
Sankarshana Srinivasan ◽  
Daniel B. Thomas ◽  
Francesco Pace ◽  
Richard Battye
Keyword(s):  
Modified Gravity ◽  
Model Independent

On Modified Gravity

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Viktor Toth ◽  
Jean-Pierre Luminet
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Modified Theories Of Gravity ◽  
Theories Of Gravity

Viktor Toth adds theoretical insights to the modified theories of gravity that aimed to solve the dark matter problem without necessitating the existence of hypothetic particles of nonbaryonic matter.

Particle dark matter in the galactic halo: recent results from DAMA/LIBRAThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at École de Physique, les Houches, France, 30 May – 4 June, 2010.

2011 ◽  
Vol 89 (1) ◽  
pp. 141-152 ◽  
Author(s):  
R. Bernabei ◽  
P. Belli ◽  
F. Montecchia ◽  
F. Nozzoli ◽  
F. Cappella ◽  
...  
Keyword(s):  
Dark Matter ◽  
First Generation ◽  
Galactic Halo ◽  
National Laboratory ◽  
Cumulative Exposure ◽  
Independent Evidence ◽  
Annual Cycles ◽  
Atomic Systems ◽  
Model Independent ◽  
Particle Dark Matter

The DAMA/LIBRA experiment has a sensitive mass of about 250 kg highly radiopure NaI(Tl). It is running at the Gran Sasso National Laboratory of the INFN in Italy and is mainly devoted to the investigation of dark matter (DM) particles in the galactic halo by exploiting the model-independent DM annual modulation signature. The present DAMA/LIBRA and the former DAMA/NaI experiments (the first generation experiment having an exposed mass of about 100 kg) have thus far cumulatively released the results of data collected over 13 annual cycles (total exposure: 1.17 t year). They give model-independent evidence of the presence of DM particles in the galactic halo on the basis of the investigated DM signature at 8.9 σ C.L. for the cumulative exposure. The main aspects of the obtained results are summarized and some comments are addressed.

scholarly journals PARTICLE DARK MATTER IN THE GALACTIC HALO: RESULTS FROM DAMA/LIBRA

2012 ◽  
Vol 12 ◽  
pp. 37-47
Author(s):  
R. BERNABEI ◽  
P. BELLI ◽  
F. MONTECCHIA ◽  
F. NOZZOLI ◽  
F. CAPPELLA ◽  
...  
Keyword(s):  
Dark Matter ◽  
First Generation ◽  
Galactic Halo ◽  
National Laboratory ◽  
Annual Modulation ◽  
Independent Evidence ◽  
Total Exposure ◽  
Annual Cycles ◽  
Model Independent ◽  
Particle Dark Matter

The DAMA/LIBRA experiment, running at the Gran Sasso National Laboratory of the I.N.F.N. in Italy, has a sensitive mass of about 250 kg highly radiopure NaI(Tl). It is mainly devoted to the investigation of Dark Matter (DM) particles in the Galactic halo by exploiting the model independent DM annual modulation signature. The present DAMA/LIBRA experiment and the former DAMA/NaI one (the first generation experiment having an exposed mass of about 100 kg) have cumulatively released so far the results obtained with the data collected over 13 annual cycles; the total exposure is 1.17 ton × yr. They give a model independent evidence of the presence of DM particles in the galactic halo at 8.9 σ C.L. on the basis of the investigated DM signature. Few aspects of the obtained results are summarized and some comments addressed.

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 Dark matter in logarithmic F(R) gravity

2019 ◽  
Vol 28 (12) ◽  
pp. 1950157 ◽  
Author(s):  
Tomohiro Inagaki ◽  
Yamato Matsuo ◽  
Hiroki Sakamoto
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Modified Gravity ◽  
Field Method ◽  
Quantum Corrections ◽  
Prototype Model ◽  
Wide Range ◽  
Modified Gravity Theories ◽  
Primordial Inflation ◽  
Cmb Fluctuations

The logarithmic [Formula: see text]-corrected [Formula: see text] gravity is investigated as a prototype model of modified gravity theories with quantum corrections. By using the auxiliary field method, the model is described by the general relativity with a scalaron field. The scalaron field can be identified as an inflaton at the primordial inflation era. It is also one of the dark matter candidates in the dark energy (DE) era. It is found that a wide range of the parameters is consistent with the current observations of CMB fluctuations, DE and dark matter.

scholarly journals Model-independent indirect detection constraints on hidden sector dark matter

2016 ◽  
Vol 2016 (06) ◽  
pp. 024-024 ◽  
Author(s):  
Gilly Elor ◽  
Nicholas L. Rodd ◽  
Tracy R. Slatyer ◽  
Wei Xue
Keyword(s):  
Dark Matter ◽  
Indirect Detection ◽  
Hidden Sector ◽  
Model Independent
Sign in / Sign up

Export Citation Format

Share Document