On the late-time cosmology of a condensed scalar field

2016 ◽  
Vol 31 (12) ◽  
pp. 1650078
Author(s):  
Amir Ghalee
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Condensed Phase ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Kinetic Term ◽  
Late Time ◽  
Gradient Instability

We study the late-time cosmology of a scalar field with a kinetic term non-minimally coupled to gravity. It is demonstrated that the scalar field dominate the radiation matter and the cold dark matter (CDM). Moreover, we show that eventually the scalar field will be condensed and results in an accelerated expansion. The metric perturbations around the condensed phase of the scalar field are investigated and it has been shown that the ghost instability and gradient instability do not exist.

scholarly journals Scalar Field Models for an Accelerating Universe

2005 ◽  
Vol 201 ◽  
pp. 260-263
Author(s):  
Varun. Sahni
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Accelerating Universe ◽  
Late Time ◽  
Luminosity Distance ◽  
New Class ◽  
Scalar Field Models ◽  
Model Independent

I describe a new class of quintessence+CDM models in which late time scalar field oscillations can give rise to both quintessence and cold dark matter. Additionally, a versatile ansatz for the luminosity distance is used to reconstruct the quintessence equation of state in amodel independentmanner from observations of high redshift supernovae.

scholarly journals Viscous cold dark matter in agreement with observations

2014 ◽  
Vol 11 (02) ◽  
pp. 1460013 ◽  
Author(s):  
Hermano Velten
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Small Scale ◽  
Late Time ◽  
Viscous Effects ◽  
Cosmological Observations ◽  
Bulk Viscous ◽  
Standard Cosmological Model ◽  
Viscous Pressure

We discuss bulk viscous cosmological models. Since the bulk viscous pressure is negative, viable viscous cosmological scenarios with late time accelerated expansion can in principle be constructed. After discussing some alternative models based on bulk viscous effects we will focus on a model very similar to the standard ΛvCDM. We argue that a ΛvCDM model, where we assign a very small (albeit perceptible) bulk viscosity to dark matter is in agreement with available cosmological observations. Hence, we work with the concept of viscous Cold Dark Matter (vCDM). At the level of the perturbations, the growth of vCDM structures is slightly suppressed when compared with the standard CDM ones. Having in mind that the small scale problems of the ΛCDM model are related to an excess of clustering, our proposal seems to indicate a possible direction for solving the serious drawbacks of the CDM paradigm within the standard cosmological model.

scholarly journals Smooth Crossing ofwΛ=−1Line in a Single Scalar Field Model

2009 ◽  
Vol 2009 ◽  
pp. 1-14 ◽  
Author(s):  
Abhik Kumar Sanyal
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Cosmological Model ◽  
Simple Form ◽  
Cold Dark Matter ◽  
Field Model ◽  
Late Time ◽  
Transient Phenomenon ◽  
Phantom Divide ◽  
Phantom Divide Line

Smooth double crossing of the phantom divide linewΛ=−1has been found possible with a single minimally coupled scalar field for the most simple form of generalizedk-essence cosmological model, in the presence of background cold dark matter. Such crossing is a sufficiently late time transient phenomenon and does not have any pathological behaviour.

scholarly journals Intermediate Inflation or Late Time Acceleration?

2008 ◽  
Vol 2008 ◽  
pp. 1-16 ◽  
Author(s):  
Abhik Kumar Sanyal
Keyword(s):  
Scalar Field ◽  
Power Law ◽  
Cosmological Evolution ◽  
Expansion Rate ◽  
Accelerated Expansion ◽  
Kinetic Term ◽  
Late Time ◽  
Late Time Acceleration ◽  
Cosmic Evolution ◽  
Scaling Solution

The expansion rate of “intermediate inflation” lies between the exponential and power law expansion but corresponding accelerated expansion does not start at the onset of cosmological evolution. Present study of “intermediate inflation” reveals that it admits scaling solution and has got a natural exit form it at a later epoch of cosmic evolution, leading to late time acceleration. The corresponding scalar field responsible for such feature is also found to behave as a tracker field for gravity with canonical kinetic term.

scholarly journals Connecting cosmological simulations to the real world

2003 ◽  
Vol 208 ◽  
pp. 245-260
Author(s):  
C.S. Frenk
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Big Bang ◽  
Accelerated Expansion ◽  
Astronomical Data ◽  
Cosmic Evolution ◽  
Small Quantum ◽  
The Big Bang ◽  
Current Paradigm ◽  
Coherent Picture

A timely combination of new theoretical ideas and observational discoveries has brought about significant advances in our understanding of cosmic evolution. Computer simulations have played a key role in these developments by providing the means to interpret astronomical data in the context of physical and cosmological theory. In the current paradigm, our Universe has a flat geometry, is undergoing accelerated expansion and is gravitationaly dominated by elementary particles that make up cold dark matter. Within this framework, it is possible to simulate in a computer the emergence of galaxies and other structures from small quantum fluctuations imprinted during an epoch of inflationary expansion shortly after the Big Bang. The simulations must take into account the evolution of the dark matter as well as the gaseous processes involved in the formation of stars and other visible components. Although many unresolved questions remain, a coherent picture for the formation of cosmic structure in now beginning to emerge.

Pilgrim dark energy models in fractal universe

2016 ◽  
Vol 26 (06) ◽  
pp. 1750049 ◽  
Author(s):  
Abdul Jawad ◽  
Shamaila Rani ◽  
Ines G. Salako ◽  
Faiza Gulshan
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Freezing And Thawing ◽  
Eos Parameter ◽  
Pilgrim Dark Energy ◽  
Energy Models ◽  
Expansion Behavior ◽  
The Universe

We discuss the cosmological implications of interacting pilgrim dark energy (PDE) models (with Hubble, Granda–Oliveros and generalized ghost cutoffs) with cold dark matter ([Formula: see text]CDM) in fractal cosmology by assuming the flat universe. We observe that the Hubble parameter lies within observational suggested ranges while deceleration parameter represents the accelerated expansion behavior of the universe. The equation of state (EoS) parameter ([Formula: see text]) corresponds to the quintessence region and phantom region for different cases of [Formula: see text]. Further, we can see that [Formula: see text]–[Formula: see text] (where prime indicates the derivative with respect to natural logarithmic of scale factor) plane describes the freezing and thawing regions and also corresponds to [Formula: see text] limit for some cases of [Formula: see text] (PDE parameter). It is also noted that the [Formula: see text]–[Formula: see text] (state-finder parameters) plane corresponds to [Formula: see text] limit and also shows the Chaplygin as well as phantom/quintessence behavior. It is observed that pilgrim dark energy models in fractal cosmology expressed the consistent behavior with recent observational schemes.

scholarly journals CAN BRANS–DICKE SCALAR FIELD ACCOUNT FOR DARK ENERGY AND DARK MATTER?

2006 ◽  
Vol 21 (15) ◽  
pp. 1241-1248 ◽  
Author(s):  
M. ARIK ◽  
M. C. ÇALIK
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Energy Density ◽  
Late Time ◽  
Energy Contribution ◽  
Time Solution ◽  
The Universe

By using a linearized non-vacuum late time solution in Brans–Dicke cosmology, we account for the 75% dark energy contribution but not for approximately 23% dark matter contribution to the present day energy density of the universe.

scholarly journals Brief History of Ultra-light Scalar Dark Matter Models

2018 ◽  
Vol 168 ◽  
pp. 06005 ◽  
Author(s):  
Jae-Weon Lee
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Cold Dark Matter ◽  
Einstein Condensate ◽  
Matter Wave ◽  
Small Scale ◽  
Matter Model ◽  
Light Scalar ◽  
History Of ◽  
Dark Matter Model

This is a review on the brief history of the scalar field dark matter model also known as fuzzy dark matter, BEC dark matter, wave dark matter, or ultra-light axion. In this model ultra-light scalar dark matter particles with mass m = O(10-22)eV condense in a single Bose-Einstein condensate state and behave collectively like a classical wave. Galactic dark matter halos can be described as a self-gravitating coherent scalar field configuration called boson stars. At the scale larger than galaxies the dark matter acts like cold dark matter, while below the scale quantum pressure from the uncertainty principle suppresses the smaller structure formation so that it can resolve the small scale crisis of the conventional cold dark matter model.

scholarly journals CONSTRAINING TEVES GRAVITY AS EFFECTIVE DARK MATTER AND DARK ENERGY

2007 ◽  
Vol 16 (12a) ◽  
pp. 2055-2063 ◽  
Author(s):  
HONGSHENG ZHAO
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Gravitational Lensing ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Elliptical Galaxies ◽  
Dual Roles ◽  
Acceleration Of The Universe ◽  
The Universe

The phenomena customarily described with the standard ΛCDM model are broadly reproduced by an extremely simple model in TeVeS, Bekenstein's1 modification of general relativity motivated by galaxy phenomenology. Our model can account for the acceleration of the Universe seen at SNeIa distances without a cosmological constant, and the accelerations seen in rotation curves of nearby spiral galaxies and gravitational lensing of high-redshift elliptical galaxies without cold dark matter. The model is consistent with BBN and the neutrino mass between 0.05 eV to 2 eV. The TeVeS scalar field is shown to play the effective dual roles of dark matter and dark energy, with the amplitudes of the effects controlled by a μ function of the scalar field, called the μ essence here. We also discuss outliers to the theory's predictions on multiimaged galaxy lenses and outliers on the subgalaxy scale.

scholarly journals NEW PHYSICS AT LOW ENERGIES AND DARK MATTER-DARK ENERGY TRANSMUTATION

2005 ◽  
Vol 20 (06) ◽  
pp. 1140-1147 ◽  
Author(s):  
E. I. GUENDELMAN ◽  
A. B. KAGANOVICH
Keyword(s):  
Field Theory ◽  
Dark Matter ◽  
Dark Energy ◽  
Energy Density ◽  
Cold Dark Matter ◽  
Late Time ◽  
Frw Universe ◽  
Dark Energy Density ◽  
Total Energy Density ◽  
Fermion Fields

A field theory is proposed where the regular fermionic matter and the dark fermionic matter can be different states of the same "primordial" fermion fields. In regime of the fermion densities typical for normal particle physics, the primordial fermions split into three families identified with regular fermions. When fermion energy density becomes comparable with dark energy density, the theory allows transition to new type of states. The possibility of such Cosmo-Low Energy Physics (CLEP) states is demonstrated by means of solutions of the field theory equations describing FRW universe filled with homogeneous scalar field and uniformly distributed nonrelativistic neutrinos. Neutrinos in CLEP state are drawn into cosmological expansion by means of dynamically changing their own parameters. One of the features of the fermions in CLEP state is that in the late time universe their masses increase as a3/2 (a=a(t) is the scale factor). The energy density of the cold dark matter consisting of neutrinos in CLEP state scales as a sort of dark energy; this cold dark matter possesses negative pressure and for the late time universe its equation of state approaches that of the cosmological constant. The total energy density of such universe is less than it would be in the universe free of fermionic matter at all.

Sign in / Sign up

Export Citation Format

Share Document