A new constant behind the rotational velocity of galaxies

Abstract The present work is devoted to studying the dynamical evolution of galaxies in scalar-Gauss-Bonnet gravity and its relationship with the MOND paradigm. This study is useful for giving meaning to the presence of a new gravitational constant. The stability of dark matter is strongly dependent on matter density. We are interested in calculating the maximum rotational velocity of galaxies. We show that rotating galaxies can be described by a new parameter that depends both on the minimum value of scalar fields and on the effective mass of this field. According to observational data, we have shown that this parameter is a constant.

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Chemo-dynamical evolution of dwarf galaxies: from flat to cuspy dark matter density profiles

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310008318 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 78-78

Author(s):

S. Pasetto ◽

E. K. Grebel ◽

P. Berczik ◽

R. Spurzem

Keyword(s):

Dark Matter ◽

Dwarf Galaxies ◽

Initial Conditions ◽

Smooth Particle Hydrodynamic ◽

Dynamical Evolution ◽

Mass Range ◽

Density Profiles ◽

Hydrodynamic Approach ◽

The Stability ◽

Evolution With Time

A model of an isolated dwarf spherical galaxy (dSph) is considered in its chemo-dynamical evolution with time. The system is composed by 3 γ-model density profiles: gas, stellar and dark matter, and it is realized in a spherical symmetric equilibrium configuration. The total masses used in our simulations are covering the dwarf galaxies mass range. The stability of this configuration is first tested for the system evolving under the gravity effect alone and then evolved taking into account for the most relevant stellar astrophysical processes implemented with a Smooth Particle Hydrodynamic approach. The two different kinds of evolution are compared. The dark matter evolves naturally from a centrally cuspy density profile into a flatter one within a timescale of several Gyr. The effect manifests itself naturally, without any tuned initial conditions, as soon as few standard criteria on star formation are assumedand the SN feedback on the ISM has been adopted the prescription in (Cioffi & Shull 1991) and (Bradamante et al. 1998). This result is expected to be a possible natural explanation for the discrepancy between observations that want flatter dark matter profiles (e.g. de Block 2005), and N-body simulations that predict cuspy dark matter profiles (Navarro et al. 1997). Chemical considerations are presented as a tool to follow with observational parameters the theory predictions.

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Dark matter halo with charge in pseudo-spheroidal geometry

Modern Physics Letters A ◽

10.1142/s0217732321501789 ◽

2021 ◽

pp. 2150178

Author(s):

Mithun Ghosh

Keyword(s):

Dark Matter ◽

Equation Of State ◽

Perfect Fluid ◽

Circular Orbit ◽

Galactic Halo ◽

Rotational Velocity ◽

Dark Matter Halo ◽

Cosmological Observations ◽

The Stability ◽

Spheroidal Geometry

The concept of dark matter (DM) hypothesis comes out as a result from the input of the observed flat rotational velocity. With the assumption that the galactic halo is pseudo-spheroidal and filled with charged perfect fluid, we have obtained a solution which has inkling to a (nearly) flat universe, compatible with the modern day cosmological observations. Various other important aspects of the solution such as attractive gravity in the halo region and the stability of the circular orbit are also explored. Also, the matter in the halo region satisfies the known equation of state which indicates its non-exotic nature.

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The Z5 model of two-component dark matter

Journal of High Energy Physics ◽

10.1007/jhep09(2020)030 ◽

2020 ◽

Vol 2020 (9) ◽

Cited By ~ 1

Author(s):

Geneviève Bélanger ◽

Alexander Pukhov ◽

Carlos E. Yaguna ◽

Óscar Zapata

Keyword(s):

Dark Matter ◽

Standard Model ◽

Direct Detection ◽

Scalar Fields ◽

Matter Density ◽

Scalar Model ◽

Complex Scalar ◽

Two Component ◽

Model Features ◽

First Time

Abstract Scenarios for multi-component scalar dark matter based on a single ZN (N ≥ 4) symmetry are simple and well-motivated. In this paper we investigate, for the first time, the phenomenology of the Z5 model for two-component dark matter. This model, which can be seen as an extension of the well-known singlet scalar model, features two complex scalar fields — the dark matter particles — that are Standard Model singlets but have different charges under a Z5 symmetry. The interactions allowed by the Z5 give rise to novel processes between the dark matter particles that affect their relic densities and their detection prospects, which we study in detail. The key parameters of the model are identified and its viable regions are characterized by means of random scans. We show that, unlike the singlet scalar model, dark matter masses below the TeV are still compatible with present data. Even though the dark matter density turns out to be dominated by the lighter component, we find that current and future direct detection experiments may be sensitive to signals from both dark matter particles.

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SCALAR FIELDS RECONSTRUCTION OF VISCOUS GDE WITH VARYING G

International Journal of Modern Physics D ◽

10.1142/s0218271814500023 ◽

2014 ◽

Vol 23 (01) ◽

pp. 1450002 ◽

Cited By ~ 1

Author(s):

MOSTAFA SHARIFIAN ◽

AHMAD SHEYKHI

Keyword(s):

Dark Matter ◽

Dark Energy ◽

Scalar Field ◽

Gravitational Constant ◽

Scalar Fields ◽

Frw Universe ◽

Ghost Dark Energy ◽

Scalar Field Models ◽

Varying Gravitational Constant ◽

The Universe

In this paper, we first study the effects of the varying gravitational constant G as well as the bulk viscosity on the evolution of the Universe field with pressureless dark matter and ghost dark energy (GDE). Then, we establish a correspondence between viscous GDE and scalar field models of dark energy including quintessence, tachyon, K-essence and dilaton energy density in a flat FRW universe. This correspondence allows us to reconstruct the potential and dynamics of the scalar fields according to the evolution of interacting viscous GDE with varying G.

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Effective masses in a dense fermion background — Applied to neutrinos, dark matter and dark energy

International Journal of Modern Physics A ◽

10.1142/s0217751x14440102 ◽

2014 ◽

Vol 29 (21) ◽

pp. 1444010

Author(s):

Bruce H. J. McKellar ◽

T. J. Goldman ◽

G. J. Stephenson

Keyword(s):

Dark Matter ◽

Dark Energy ◽

Scalar Field ◽

Effective Mass ◽

Negative Pressure ◽

Expectation Value ◽

Effective Masses ◽

Neutrino Astrophysics

If fermions interact with a scalar field, and there are many fermions present the scalar field may develop an expectation value and generate an effective mass for the fermions. This can lead to the formation of fermion clusters, which could be relevant for neutrino astrophysics and for dark matter astrophysics. Because this system may exhibit negative pressure, it also leads to a model of dark energy.

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Dark matter candidates in a type-II radiative neutrino mass model

Journal of High Energy Physics ◽

10.1007/jhep06(2021)072 ◽

2021 ◽

Vol 2021 (6) ◽

Author(s):

Roberto A. Lineros ◽

Mathias Pierre

Keyword(s):

Dark Matter ◽

Neutral Particle ◽

Matter Density ◽

Indirect Detection ◽

Dark Matter Candidate ◽

Neutrino Masses ◽

Type Ii ◽

Mass Model ◽

Direct And Indirect Detection

Abstract We explore the connection between Dark Matter and neutrinos in a model inspired by radiative Type-II seessaw and scotogenic scenarios. In our model, we introduce new electroweakly charged states (scalars and a vector-like fermion) and impose a discrete ℤ2 symmetry. Neutrino masses are generated at the loop level and the lightest ℤ2-odd neutral particle is stable and it can play the role of a Dark Matter candidate. We perform a numerical analysis of the model showing that neutrino masses and flavour structure can be reproduced in addition to the correct dark matter density, with viable DM masses from 700 GeV to 30 TeV. We explore direct and indirect detection signatures and show interesting detection prospects by CTA, Darwin and KM3Net and highlight the complementarity between these observables.

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The Large Range of Dark Matter content in Dwarf Galaxies and its Implications

Symposium - International Astronomical Union ◽

10.1017/s0074180900233536 ◽

1996 ◽

Vol 171 ◽

pp. 435-435

Author(s):

S.A. Pustilnik ◽

V.A. Lipovetsky ◽

J.-M. Martin ◽

T.X. Thuan

Keyword(s):

Dark Matter ◽

Galaxy Formation ◽

Large Range ◽

Dwarf Galaxy ◽

Rotational Velocity ◽

Matter Content ◽

Optical Observations ◽

Strong Interactions ◽

Formation Mechanisms ◽

Mass Ratio

We present the analysis of a new set of radio and optical observations of a large sample of Byurakan Blue Compact Galaxies. HI spectra were obtained with the Nançay 300-m and Green Bank 43-m radio telescopes. CCD-images were taken with the KPNO 0.9-m and Whipple Observatory 1.2-m telescopes. Dark Matter (DM) to luminous mass ratios in these BCGs were found to vary from about less than 0.5 up to 14. Recent data taken from the literature indicate this same range. This result has important consequences on models of dwarf galaxy formation, indicating possibly different formation mechanisms. The standard CDM model of dwarfs formation requires large DM halos. However the formation of dwarfs as tidal debris resulting from strong interactions of massive spirals leads naturally to dwarfs with low content of DM. On Fig.1 we show DM to luminous mass ratio versus rotational velocity for our BCGs and some other galaxies.

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Direct detection of atomic dark matter in white dwarfs

Journal of High Energy Physics ◽

10.1007/jhep03(2021)166 ◽

2021 ◽

Vol 2021 (3) ◽

Author(s):

David Curtin ◽

Jack Setford

Keyword(s):

Dark Matter ◽

Energy Loss ◽

Cooling Rate ◽

White Dwarf ◽

White Dwarfs ◽

Luminosity Function ◽

Direct Detection ◽

Matter Density ◽

Mixing Parameter ◽

First Time

Abstract Dark matter could have a dissipative asymmetric subcomponent in the form of atomic dark matter (aDM). This arises in many scenarios of dark complexity, and is a prediction of neutral naturalness, such as the Mirror Twin Higgs model. We show for the first time how White Dwarf cooling provides strong bounds on aDM. In the presence of a small kinetic mixing between the dark and SM photon, stars are expected to accumulate atomic dark matter in their cores, which then radiates away energy in the form of dark photons. In the case of white dwarfs, this energy loss can have a detectable impact on their cooling rate. We use measurements of the white dwarf luminosity function to tightly constrain the kinetic mixing parameter between the dark and visible photons, for DM masses in the range 10−5–105 GeV, down to values of ϵ ∼ 10−12. Using this method we can constrain scenarios in which aDM constitutes fractions as small as 10−3 of the total dark matter density. Our methods are highly complementary to other methods of probing aDM, especially in scenarios where the aDM is arranged in a dark disk, which can make direct detection extremely difficult but actually slightly enhances our cooling constraints.

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FERMIONIC AND SCALAR FIELDS AS SOURCES OF INTERACTING DARK MATTER–DARK ENERGY

International Journal of Modern Physics D ◽

10.1142/s0218271811020500 ◽

2011 ◽

Vol 20 (13) ◽

pp. 2543-2558 ◽

Cited By ~ 2

Author(s):

SAMUEL LEPE ◽

JAVIER LORCA ◽

FRANCISCO PEÑA ◽

YERKO VÁSQUEZ

Keyword(s):

Dark Matter ◽

Dark Energy ◽

Scalar Field ◽

Analytical Solution ◽

Scalar Fields ◽

Nonminimal Coupling ◽

Field Equations ◽

Fermionic Field ◽

Minimal Coupling ◽

Constant Type

From a variational action with nonminimal coupling with a scalar field and classical scalar and fermionic interaction, cosmological field equations can be obtained. Imposing a Friedmann–Lemaître–Robertson–Walker (FLRW) metric, the equations lead directly to a cosmological model consisting of two interacting fluids, where the scalar field fluid is interpreted as dark energy and the fermionic field fluid is interpreted as dark matter. Several cases were studied analytically and numerically. An important feature of the non-minimal coupling is that it allows crossing the barrier from a quintessence to phantom behavior. The insensitivity of the solutions to one of the parameters of the model permits it to find an almost analytical solution for the cosmological constant type of universe.

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