scholarly journals CAN A HYPERBOLIC PHASE OF THE BRANS–DICKE FIELD ACCOUNT FOR DARK MATTER?

2009 ◽  
Vol 18 (04) ◽  
pp. 587-597 ◽  
Author(s):  
M. ARIK ◽  
M. ÇALIK ◽  
F. ÇIFTER
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Hubble Parameter ◽  
Cosmological Solution ◽  
Rate Of Change ◽  
Fractional Rate

We show that the introduction of a hyperbolic phase of the Brans–Dicke (BD) field results in a flat vacuum cosmological solution of the Hubble parameter H and a fractional rate of change of the BD scalar field F, which asymptotically approach constant values. At later stages, the hyperbolic phase of the BD field behaves like dark matter.

scholarly journals Hubble parameter and the potential of the cosmological scalar field

2020 ◽  
pp. 15-19
Author(s):  
V. Zhdanov ◽  
A. Alexandrov ◽  
O. Stashko
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Hubble Parameter ◽  
Three Dimensional ◽  
Approximation Error ◽  
Field Potential ◽  
Matter Content ◽  
Order Equation ◽  
The Other ◽  
Cold Matter

We consider a homogeneous isotropic Universe filled with cold matter (with zero pressure) and dynamic dark energy in a form of a scalar field. For known scalar field potential V(φ), the Friedmann equations are reduced to a system of the first order equation for the Hubble parameter H(z) and the second order equation for the scalar field as functions of the redshift z. On the other hand, knowledge of H(z) allows us to get the scalar field potential in a parametric form for a known cold matter content and three dimensional curvature parameter. We analyze when the accepted model mimics the dependence H(z) derived in the framework of the other models, e.g., hydrodynamic ones. Two examples of this mimicry are considered. The first one deals with the case when H2(z)~ Ωm(1+z)3+ΩΛ, but Ωm parameter overestimates the input of the cold matter (dark matter+baryons). The resulting scalar field potential is V(φ)=a+bsinh2(cφ), where the constants a,b,c depend on the Ω – parameters of the problem. In the other example we assume that some part of the dark matter has a non-zero equation of state p=wε, -1<w<1. In this case H2(z)~ Ωdm1(1+z)3(1+w)+ Ωb+Ωdm2)(1+z)3+ΩΛ. The corresponding potentials are defined for positive values of φ. For both signs of w potential V(φ) is a monotonically increasing function with typically an asymptotically exponential behavior; though for some choice of parameters we may have a singularity of V(φ)on a finite interval. Then we consider fitting of the potential for w from the interval [-0.2,0.2] for three different values of Ωdm2 by means of a simple formula Vfit(φ)=p0+p1exp(p2 φ). The dependencies pi(w) are presented and the approximation error is estimated.

FIVE-DIMENSIONAL COSMOLOGICAL SCALING SOLUTION

2005 ◽  
Vol 20 (12) ◽  
pp. 923-928 ◽  
Author(s):  
BAORONG CHANG ◽  
HONGYA LIU ◽  
HUANYING LIU ◽  
LIXIN XU
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Phase Plane ◽  
Cosmological Solution ◽  
Phase Plane Analysis ◽  
Late Time ◽  
Plane Analysis ◽  
Scaling Solution ◽  
Frw Models ◽  
The Universe

A five-dimensional Ricci-flat cosmological solution is studied by assuming that the induced 4D matter contains two components: the usual fluid for dark matter as well as baryons and a scalar field with an exponential potential for dark energy. With use of the phase-plane analysis it is shown that there exist two late-time attractors one of which corresponds to a universe dominated by the scalar field alone and the other is a scaling solution in which the energy density of the scalar field remains proportional to that of the dark matter. It is furthermore shown that for this 5D scaling solution the universe expands with the same rate as in the 4D FRW models and not relies on which 4D hypersurface the universe is located in the 5D manifold.

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

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.

Bose-Einstein condensates from scalar field dark matter

2010 ◽  
Author(s):  
L. Arturo Ureña-López ◽  
Alfredo Macias ◽  
Marco Maceda
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Bose Einstein

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

2011 ◽  
Vol 20 (13) ◽  
pp. 2543-2558 ◽  
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.

Black hole in balance with dark matter

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040050
Author(s):  
Boris E. Meierovich
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Phase Equilibrium ◽  
Vector Field ◽  
Scalar Field ◽  
Total Mass ◽  
Metric Tensor ◽  
Static Solutions ◽  
Tensor Formula ◽  
Galaxy Rotation Curves

Equilibrium of a gravitating scalar field inside a black hole compressed to the state of a boson matter, in balance with a longitudinal vector field (dark matter) from outside is considered. Analytical consideration, confirmed numerically, shows that there exist static solutions of Einstein’s equations with arbitrary high total mass of a black hole, where the component of the metric tensor [Formula: see text] changes its sign twice. The balance of the energy-momentum tensors of the scalar field and the longitudinal vector field at the interface ensures the equilibrium of these phases. Considering a gravitating scalar field as an example, the internal structure of a black hole is revealed. Its phase equilibrium with the longitudinal vector field, describing dark matter on the periphery of a galaxy, determines the dependence of the velocity on the plateau of galaxy rotation curves on the mass of a black hole, located in the center of a galaxy.

Self-interacting complex scalar field as dark matter

2011 ◽  
Author(s):  
F. Briscese ◽  
Luis Arturo Ureña-López ◽  
Hugo Aurelio Morales-Técotl ◽  
Román Linares-Romero ◽  
Elí Santos-Rodríguez ◽  
...  
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Complex Scalar ◽  
Complex Scalar Field

scholarly journals Modern Topics in Scalar Field Cosmology

2020 ◽  
Author(s):  
◽  
Cari Powell
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Mass Range ◽  
Distant Future ◽  
Field System ◽  
Stochastic Background ◽  
Scalar Field Cosmology

The aim of this research is to use modern techniques in scalar field Cosmol-ogy to produce methods of detecting gravitational waves and apply them to current gravitational waves experiments and those that will be producing results in the not too distant future. In the first chapter we discuss dark matter and some of its candidates, specifically, the axion. We then address its relationship with gravitational waves. We also discuss inflation and how it can be used to detect gravitational waves. Chapter 2 concentrates on constructing a multi field system of axions in order to increase the mass range of the ultralight axion, putting it into the observation range of pul-sar timing arrays. Chapter 3 discusses non-attractor inflation which is able to enhance stochastic background gravitational waves at scales that allows them to be measured by gravitational wave experiments. Chapter 4 uses a similar method to chapter 3 and applies it to 3-point overlap functions for tensor, scalar and a combination of the two polarisations.

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