scholarly journals Superheavy dark matter in $$R+R^2$$ cosmology with conformal anomaly

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
E. V. Arbuzova ◽  
A. D. Dolgov ◽  
R. S. Singh
Keyword(s):  
Dark Matter ◽  
Coupling Strength ◽  
Modified Gravity ◽  
Particle Creation ◽  
Cosmological Evolution ◽  
Particle Mass ◽  
Conformal Anomaly ◽  
Gauge Bosons ◽  
Superheavy Dark Matter

AbstractCosmological evolution and particle creation in $$R^2$$ R 2 -modified gravity are considered for the case of the dominant decay of the scalaron into a pair of gauge bosons due to conformal anomaly. It is shown that in the process of thermalization superheavy dark matter with the coupling strength typical for the GUT SUSY can be created. Such dark matter would have the proper cosmological density if the particle mass is close to $$10^{12}$$ 10 12 GeV.

scholarly journals R2-Cosmology and New Windows for Superheavy Dark Matter

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 877
Author(s):  
Elena Arbuzova ◽  
Alexander Dolgov ◽  
Rajnish Singh
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Modified Gravity ◽  
Gauge Bosons ◽  
Decay Channels ◽  
Decay Modes ◽  
The Masses ◽  
Superheavy Dark Matter ◽  
The Universe

Evolution and heating of the universe in R2-modified gravity are considered. It is shown that the universe’s history can be separated into four different epochs: (1) inflation, (2) heating due to curvature oscillations (scalaron decay), (3) transition to matter dominated period, and (4) conventional cosmology governed by General Relativity. Cosmological density of dark matter (DM) particles for different decay channels of the scalaron is calculated. The bounds on the masses of DM particles are derived for the following dominant decay modes: to minimally coupled scalars, to massive fermions, and to gauge bosons.

scholarly journals Superheavy dark matter in R2-cosmology

2021 ◽  
pp. 2140002
Author(s):  
E. V. Arbuzova
Keyword(s):  
Dark Matter ◽  
Coupling Strength ◽  
Interaction Strength ◽  
Particle Creation ◽  
Inflationary Model ◽  
Decay Channels ◽  
Cosmological Expansion ◽  
Stable Particles ◽  
Superheavy Dark Matter

The conventional Friedmann cosmology is known to be in tension with the existence of stable particles having interaction strength typical for supersymmetry and heavier than several TeV. A possible way to save life of such particles may be a modification of the standard cosmological expansion law in such a way that the density of these heavy relics would be significantly reduced. We study particle creation in the Starobinsky inflationary model for different decay channels of the scalaron. It is shown that the process of thermalization superheavy stable particles with the coupling strength typical for the GUT SUSY could be created with the density equal to the observed density of dark matter.

scholarly journals Vector dark matter from split SU(2) gauge bosons

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Zexi Hu ◽  
Chengfeng Cai ◽  
Yi-Lei Tang ◽  
Zhao-Huan Yu ◽  
Hong-Hao Zhang
Keyword(s):  
Dark Matter ◽  
Gauge Group ◽  
Measurement Data ◽  
Indirect Detection ◽  
Gauge Bosons ◽  
Dark Matter Relic Density ◽  
Matter Model ◽  
Direct And Indirect Detection ◽  
Numerous Parameter ◽  
Dark Matter Model

Abstract We propose a vector dark matter model with an exotic dark SU(2) gauge group. Two Higgs triplets are introduced to spontaneously break the symmetry. All of the dark gauge bosons become massive, and the lightest one is a viable vector DM candidate. Its stability is guaranteed by a remaining Z2 symmetry. We study the parameter space constrained by the Higgs measurement data, the dark matter relic density, and direct and indirect detection experiments. We find numerous parameter points satisfying all the constraints, and they could be further tested in future experiments. Similar methodology can be used to construct vector dark matter models from an arbitrary SO(N) gauge group.

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.

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.

scholarly journals Superheavy dark matter and parametric resonance

1999 ◽  
Vol 449 (3-4) ◽  
pp. 230-236 ◽  
Author(s):  
Masato Arai ◽  
Hideaki Hiro-Oka ◽  
Nobuchika Okada ◽  
Shin Sasaki
Keyword(s):  
Dark Matter ◽  
Parametric Resonance ◽  
Superheavy 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.

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