scholarly journals Probing Dark Energy models with neutrons

2015 ◽  
Vol 30 (24) ◽  
pp. 1530048 ◽  
Author(s):  
Guillaume Pignol
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Particle Physics ◽  
Big Bang ◽  
Accelerated Expansion ◽  
Chameleon Mechanism ◽  
The Status ◽  
Light Scalar ◽  
Expansion Of The Universe ◽  
Neutron Interferometer

There is a deep connection between cosmology — the science of the infinitely large — and particle physics — the science of the infinitely small. This connection is particularly manifest in neutron particle physics. Basic properties of the neutron — its Electric Dipole Moment and its lifetime — are intertwined with baryogenesis and nucleosynthesis in the early Universe. I will cover this topic in the first part, that will also serve as an introduction (or rather a quick recap) of neutron physics and Big Bang cosmology. Then, the rest of the paper will be devoted to a new idea: using neutrons to probe models of Dark Energy. In the second part, I will present the chameleon theory: a light scalar field accounting for the late accelerated expansion of the Universe, which interacts with matter in such a way that it does not mediate a fifth force between macroscopic bodies. However, neutrons can alleviate the chameleon mechanism and reveal the presence of the scalar field with properly designed experiments. In the third part, I will describe a recent experiment performed with a neutron interferometer at the Institut Laue Langevin that sets already interesting constraints on the chameleon theory. Last, the chameleon field can be probed by measuring the quantum states of neutrons bouncing over a mirror. In the fourth part, I will present the status and prospects of the GRANIT experiment at the ILL.

scholarly journals Taxonomy of Dark Energy Models

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 163
Author(s):  
Verónica Motta ◽  
Miguel A. García-Aspeitia ◽  
Alberto Hernández-Almada ◽  
Juan Magaña ◽  
Tomás Verdugo
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Energy Component ◽  
The Past ◽  
Energy Models ◽  
The Status ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Unknown Component

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.

scholarly journals A novel teleparallel dark energy model

2016 ◽  
Vol 25 (02) ◽  
pp. 1650025 ◽  
Author(s):  
Giovanni Otalora
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Teleparallel Gravity ◽  
Accelerated Expansion ◽  
Late Time ◽  
De Sitter ◽  
Sitter Group ◽  
Current State ◽  
Expansion Of The Universe ◽  
The Universe

Although equivalent to general relativity, teleparallel gravity (TG) is conceptually speaking a completely different theory. In this theory, the gravitational field is described by torsion, not by curvature. By working in this context, a new model is proposed in which the four-derivative of a canonical scalar field representing dark energy is nonminimally coupled to the “vector torsion”. This type of coupling is motivated by the fact that a scalar field couples to torsion through its four-derivative, which is consistent with local spacetime kinematics regulated by the de Sitter group [Formula: see text]. It is found that the current state of accelerated expansion of the universe corresponds to a late-time attractor that can be (i) a dark energy-dominated de Sitter solution ([Formula: see text]), (ii) a quintessence-type solution with [Formula: see text], or (iii) a phantom-type [Formula: see text] dark energy.

scholarly journals Singularities in Inflationary Cosmological Models

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 491
Author(s):  
Leonardo Fernández-Jambrina
Keyword(s):  
Scalar Field ◽  
Field Potential ◽  
Fractional Power ◽  
Scalar Fields ◽  
Big Bang ◽  
Cosmological Models ◽  
Accelerated Expansion ◽  
Type Iv ◽  
Big Crunch ◽  
Expansion Of The Universe

Due to the accelerated expansion of the universe, the possibilities for the formation of singularities has changed from the classical Big Bang and Big Crunch singularities to include a number of new scenarios. In recent papers it has been shown that such singularities may appear in inflationary cosmological models with a fractional power scalar field potential. In this paper we enlarge the analysis of singularities in scalar field cosmological models by the use of generalised power expansions of their Hubble scalars and their scalar fields in order to describe all possible models leading to a singularity, finding other possible cases. Unless a negative scalar field potential is considered, all singularities are weak and of type IV.

BRANS-DICKE COSMOLOGY WITH FERMIONS AND CHAMELEON MECHANISM

2012 ◽  
Vol 07 ◽  
pp. 174-183
Author(s):  
DAO-JUN LIU ◽  
BIN YANG ◽  
XING-HUA JIN
Keyword(s):  
Scalar Field ◽  
Interaction Potential ◽  
The Self ◽  
Accelerated Expansion ◽  
Late Time ◽  
Fermion Field ◽  
Chameleon Mechanism ◽  
Expansion Of The Universe ◽  
Stable Solutions ◽  
The Universe

We study the cosmological dynamics of Brans-Dicke theory in which there are fermions with a coupling to BD scalar field as well as a self-interaction potential. The conditions that there exists a solution which is stable and represents a late-time accelerated expansion of the universe are found. It is shown that the late-time acceleration depends completely on the self-interaction of the fermion field if our investigation is restricted to the theory with positive BD parameter ω. Provided a negative ω is allowed, there will be another two class of stable solutions describing late-time accelerated expansion of the universe. Besides, we find that chameleon mechanism will be possessed in our theory when a suitable self-interaction of fermion field is considered.

DYNAMICS OF DARK ENERGY

2006 ◽  
Vol 15 (11) ◽  
pp. 1753-1935 ◽  
Author(s):  
EDMUND J. COPELAND ◽  
M. SAMI ◽  
SHINJI TSUJIKAWA
Keyword(s):  
Dark Energy ◽  
Particle Physics ◽  
Large Scale ◽  
Scalar Fields ◽  
Accelerated Expansion ◽  
Accelerating Universe ◽  
Late Time ◽  
Microwave Background ◽  
Energy Models ◽  
Expansion Of The Universe

We review in detail a number of approaches that have been adopted to try and explain the remarkable observation of our accelerating universe. In particular we discuss the arguments for and recent progress made towards understanding the nature of dark energy. We review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence, tachyon, phantom and dilatonic models. The importance of cosmological scaling solutions is emphasized when studying the dynamical system of scalar fields including coupled dark energy. We study the evolution of cosmological perturbations allowing us to confront them with the observation of the Cosmic Microwave Background and Large Scale Structure and demonstrate how it is possible in principle to reconstruct the equation of state of dark energy by also using Supernovae Ia observational data. We also discuss in detail the nature of tracking solutions in cosmology, particle physics and braneworld models of dark energy, the nature of possible future singularities, the effect of higher order curvature terms to avoid a Big Rip singularity, and approaches to modifying gravity which leads to a late-time accelerated expansion without recourse to a new form of dark energy.

scholarly journals RECONSTRUCTION OF NEW HOLOGRAPHIC SCALAR FIELD MODELS OF DARK ENERGY IN BRANS–DICKE UNIVERSE

2011 ◽  
Vol 26 (03) ◽  
pp. 191-204 ◽  
Author(s):  
WEI-QIANG YANG ◽  
YA-BO WU ◽  
LI-MIN SONG ◽  
YANG-YANG SU ◽  
JIAN LI ◽  
...  
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Chaplygin Gas ◽  
Energy Model ◽  
Accelerated Expansion ◽  
Holographic Dark Energy Model ◽  
Special Cases ◽  
Expansion Of The Universe

Motivated by the work: K. Karami and J. Fehri, Phys. Lett. B684, 61 (2010) and A. Sheykhi, Phys. Lett. B681, 205 (2009), we generalize their work to the new holographic dark energy model with [Formula: see text] in the framework of Brans–Dicke cosmology. Concretely, we study the correspondence between the quintessence, tachyon, K-essence, dilaton scalar field and Chaplygin gas model with the new holographic dark energy model in the non-flat Brans–Dicke universe. Furthermore, we reconstruct the potentials and dynamics for these models. By analysis we can show that for new holographic quintessence and Chaplygin gas models, if the related parameters to the potentials satisfy some constraints, the accelerated expansion can be achieved in Brans–Dicke cosmology. In particular, the counterparts of fields and potentials in general relativity can describe accelerated expansion of the universe. It is worth stressing that not only can we give some new results in the framework of Brans–Dicke cosmology, but also the previous results of the new holographic dark energy in Einstein gravity can be included as special cases given by us.

Kantowski–Sachs universe with dark energy fluid and massive scalar field

2020 ◽  
Vol 98 (11) ◽  
pp. 993-998
Author(s):  
K. Deniel Raju ◽  
M.P.V.V. Bhaskara Rao ◽  
Y. Aditya ◽  
T. Vinutha ◽  
D.R.K. Reddy
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Massive Scalar ◽  
Field Equations ◽  
Massive Scalar Field ◽  
Anisotropic Dark Energy ◽  
Expansion Of The Universe ◽  
The Universe

This study is mainly concerned with a spatially homogeneous and anisotropic Kantowski–Sachs cosmological model with anisotropic dark energy fluid and massive scalar field. We solve the field equations using (i) the shear scalar proportionality to the expansion scalar and (ii) a mathematical condition that is a consequence of the power law between the scalar field and the average scale factor of the universe, and the corresponding dark energy model is presented. The cosmological parameters of the model are computed and discussed, as well as the relevance of its dynamical aspects to the recent scenario of the accelerated expansion of the universe.

scholarly journals Reconstructing the evolution of dark energy with variations of fundamental parameters

2009 ◽  
Vol 5 (H15) ◽  
pp. 303-303
Author(s):  
N. J. Nunes ◽  
T. Dent ◽  
C. J. A. P. Martins ◽  
G. Robbers
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Structure Constant ◽  
Dynamical Evolution ◽  
Accelerated Expansion ◽  
Fine Structure Constant ◽  
Quasar Absorption Lines ◽  
Fundamental Parameters ◽  
Expansion Of The Universe ◽  
The Universe

A popular candidate of dark energy, currently driving an accelerated expansion of the universe, is a slowly rolling scalar field or quintessence. A scalar field, however, must couple with other sources of matter. Consequently, its dynamical evolution can result in extra interactions between standard particles, which are mediated by the field, and to a variation in the fundamental parameters. Curiously, it has been reported that observations of a number of quasar absorption lines suggest that the fine structure constant was smaller in the past, at redshifts in the range z=1-3 (Murphy et al. (2003), Murphy et al. (2004), but see also Srianand et al. (2007)). Could this indeed be the signature of a slowly evolving scalar field?

scholarly journals Ghost Chaplygin scalar field model of dark energy

2013 ◽  
Vol 91 (1) ◽  
pp. 54-59 ◽  
Author(s):  
F. Adabi ◽  
K. Karami ◽  
M. Mousivand
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Field Model ◽  
Accelerated Expansion ◽  
Scalar Field Model ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Friedmann Robertson Walker

We investigate the correspondence between the ghost and Chaplygin scalar field dark energy models in the framework of Einstein gravity. We consider a spatially nonflat Friedmann–Robertson–Walker universe containing dark energy that interacts with dark matter. We reconstruct the potential and the dynamics for the Chaplygin scalar field model according to the evolutionary behavior of ghost dark energy, which can describe the phantomic accelerated expansion of the universe.

scholarly journals Quantum Space and the Evolution of the Dark Universe

2017 ◽  
Author(s):  
Carlos A. Melendres
Keyword(s):  
Phase Diagram ◽  
Dark Matter ◽  
Dark Energy ◽  
State Parameter ◽  
Big Bang ◽  
Accelerated Expansion ◽  
Quantum Space ◽  
Fundamental Particles ◽  
Expansion Of The Universe ◽  
The Universe

We present a model of space that considers it to be a quantized dynamical entity which is a component of the universe along with matter and radiation. The theory is used together with  thermodynamic data  to provide a new view of cosmic  evolution  and an insight into the nature of dark energy and dark matter.           Space is made up of energy quanta. The universe started from an atomic size volume at very high  temperature and pressure near the Planck epoch. Upon expansion  and  cooling, phase transitions occurred  resulting in the formation of radiation,  fundamental particles, and matter. These  nucleate and grow into stars, galaxies, and clusters. From a phase diagram of cosmic  composition,  we  obtained  a correlation between   dark energy  and the energy of space. Using  the Friedmann  equations, data from WMAP studies of  the composition of the universe  at 3.0 x 105 (a=5.25 x 10-2) years  and at present (a=1), are well fitted by our  model with an equation of state parameter, w= -0.7.  The accelerated expansion of the universe, starting at about 7  billion years, determined by  BOSS measurements,  also correlates well with the dominance of dark energy  at 7.25 x 109 years ( a= 0.65). The expansion  can be  attributed to Quintessence with a  space force  arising from a quantum space field.  From our phase diagram, we also find a correlation suggesting  that  dark matter is a plasma form of matter similar to that  which existed during the photon epoch  immediately prior to recombination.         Our Quantum Space  Model leads to a  universe which  is  homogeneous and isotropic without the need for inflation. The thermodynamics of expansion is consistent with  BOSS data  that  show the process  to be  adiabatic and the rate of expansion  decelerating  during  the first  6  billion years after the Big Bang.  However, it  became non-adiabatic and accelerating thereafter. This  implies  an influx  of energy from a source outside the universe; it warrants consideration as a possible factor  in  the accelerated expansion of the universe.  

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