scholarly journals Observational constraints on complex quintessence with attractive self-interaction

2021 ◽  
Vol 503 (3) ◽  
pp. 4008-4015
Author(s):  
Belen Carvente ◽  
Víctor Jaramillo ◽  
Celia Escamilla-Rivera ◽  
Darío Núñez
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Early Time ◽  
Mass Term ◽  
Scalar Fields ◽  
Einstein Condensate ◽  
Late Time ◽  
Complex Scalar ◽  
Time Dynamics ◽  
Complex Scalar Field

ABSTRACT In this paper, we consider that dark energy could be described solely by a complex scalar field with a Bose–Einstein condensate-like potential (denoted as CSFDE), that is, with a self-interaction and a mass term. In particular, we analyse a solution that in a fast oscillation regime at late times behaves as a cosmological constant. Our proposal adequately describes the standard homogeneous and flat Fridman dynamics. Furthermore, in this quintessence–complex scalar field scenario, it is possible to mimic the dynamics related to dark energy. However, when the precision cosmological tests are implemented in this landscape, the generic equation of state derived for this model in a restricted regime of ai (which corresponds to the scale factor at which the scalar field turns on) cannot be constrained by late-time current observations, since the analysis constraints solely the scalar field parameters within values ruled out by the theoretical model. This result is a clear hint to consider future CSFDE models with, for instance, two scalar fields in order to study the early-time dynamics of the Universe.

scholarly journals ON THE TRANSITION FROM COMPLEX TO REAL SCALAR FIELDS IN MODERN COSMOLOGY

2011 ◽  
Vol 08 (08) ◽  
pp. 1815-1832 ◽  
Author(s):  
GIAMPIERO ESPOSITO ◽  
RAJU ROYCHOWDHURY ◽  
CLAUDIO RUBANO ◽  
PAOLO SCUDELLARO
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Scalar Fields ◽  
Complex Nature ◽  
Complex Scalar ◽  
Real Scalar ◽  
Symmetry Approach ◽  
Modern Cosmology ◽  
Complex Scalar Field ◽  
The Universe

We study some problems arising from the introduction of a complex scalar field in cosmology, modeling its possible behaviors in both the inflationary and dark energy stages of the universe. Such examples contribute to show that, while the complex nature of the scalar field can be indeed important during inflation, it loses its meaning in the later dark-energy dominated era of cosmology, when the phase of the complex field is practically constant, and there is indeed a transition from complex to real scalar field. In our considerations, the Noether symmetry approach turns out to be a useful tool once again. We arrive eventually at a potential containing the sixth and fourth powers of the scalar field, and the resulting semiclassical quantum cosmology is studied to gain a better understanding of the inflationary stage.

scholarly journals DARK ENERGY FROM SCALAR FIELD WITH GAUSS–BONNET AND NON-MINIMAL KINETIC COUPLING

2012 ◽  
Vol 27 (04) ◽  
pp. 1250018 ◽  
Author(s):  
L. N. GRANDA
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Power Law ◽  
Dynamical Equation ◽  
Early Time ◽  
Scalar Fields ◽  
Late Time ◽  
Kinetic Coupling ◽  
Energy Behavior ◽  
Phantom Phase

We consider a model of scalar field with non-minimal kinetic couplings to the curvature, and additional coupling to the Gauss–Bonnet four-dimensional invariant. The model presents rich cosmological dynamics and some of its solutions are analyzed. A variety of scalar fields and potentials giving rise to power-law expansion have been found. Two solutions with dynamical equation of state are considered. The first solution unifies early time power-law behavior with late time cosmological constant dominance. The second solution is able to describe a universe in the phantom phase, and depending on the parameters may describe essentially dark energy behavior, or may contain the decelerated and accelerated phases.

scholarly journals A General Method for Transforming Nonphysical Configurations in BPS States

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
J. R. L. Santos ◽  
A. de Souza Dutra ◽  
O. C. Winter ◽  
R. A. C. Correa
Keyword(s):  
Scalar Field ◽  
Condensed Matter ◽  
Equations Of Motion ◽  
Cosmological Parameters ◽  
Topological Defects ◽  
Scalar Fields ◽  
Complex Scalar ◽  
Complex Scalar Field ◽  
Bps States ◽  
General Method

In this work, we apply the so-called BPS method in order to obtain topological defects for a complex scalar field Lagrangian introduced by Trullinger and Subbaswamy. The BPS approach led us to compute new analytical solutions for this model. In our investigation, we found analytical configurations which satisfy the BPS first-order differential equations but do not obey the equations of motion of the model. Such defects were named nonphysical ones. In order to recover the physical meaning of these defects, we proposed a procedure which can transform them into BPS states of new scalar field models. The new models here founded were applied in the context of hybrid cosmological scenarios, where we derived cosmological parameters compatible with the observed Universe. Such a methodology opens a new window to connect different two scalar fields systems and can be implemented in several distinct applications such as Bloch Branes, Lorentz and Symmetry Breaking Scenarios, Q-Balls, Oscillons, Cosmological Contexts, and Condensed Matter Systems.

THE ORDER PARAMETER FIELD FOR COSMIC STRING, INFLATION AND DARK ENERGY

2003 ◽  
Vol 18 (36) ◽  
pp. 2587-2597 ◽  
Author(s):  
PENG-MING ZHANG ◽  
YI-SHI DUAN ◽  
LI-MING CAO
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Early Universe ◽  
Cosmic String ◽  
Order Parameter ◽  
Cosmic Strings ◽  
Complex Scalar ◽  
Parameter Field ◽  
Complex Scalar Field

We present a whole frame for the cosmic strings, inflation and dark energy with the complex scalar field which can be regarded as the order parameter of our universe. One can find that the comic strings emerge in the zeros of the complex scalar field in the early universe. And with the evolution of complex scalar field, inflation and dark energy can be understood in this frame.

scholarly journals COMPLEX SCALAR FIELD DARK MATTER ON GALACTIC SCALES

2014 ◽  
Vol 29 (02) ◽  
pp. 1430002 ◽  
Author(s):  
TANJA RINDLER-DALLER ◽  
PAUL R. SHAPIRO
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Early Universe ◽  
Einstein Condensate ◽  
Model Parameters ◽  
Galactic Halos ◽  
Complex Scalar ◽  
Bose Einstein Condensate ◽  
Complex Scalar Field ◽  
Bose Einstein

The nature of the cosmological dark matter (DM) remains elusive. Recent studies have advocated the possibility that DM could be composed of ultra-light, self-interacting bosons, forming a Bose–Einstein condensate (BEC) in the very early Universe. We consider models which are charged under a global U(1)-symmetry such that the DM number is conserved. It can then be described as a classical complex scalar field which evolves in an expanding Universe. We present a brief review on the bounds on the model parameters from cosmological and galactic observations, along with the properties of galactic halos which result from such a DM candidate.

A cosmological exact solution of generalized Brans-Dicke theory with complex scalar field and its phenomenological implications

Open Physics ◽  
2011 ◽  
Vol 9 (6) ◽  
Author(s):  
Metin Arık ◽  
Mehmet Çalık ◽  
Nihan Katırcı
Keyword(s):  
Exact Solution ◽  
Dark Energy ◽  
Scalar Field ◽  
Friedmann Equation ◽  
Constant Term ◽  
Scale Factor ◽  
Complex Scalar ◽  
Complex Scalar Field

AbstractWhen the Brans-Dicke theory is formulated in terms of the Jordan scalar field φ, the amount of dark energy is related to the mass of this field. We investigate a solution which is relevant to the late universe. We show that if φ is taken to be a complex scalar field, then an exact solution to the vacuum equations requires that the Friedmann equation possesses both a constant term and one which is proportional to the inverse sixth power of the scale factor. Possible interpretations and phenomenological implications of this result are discussed.

ANISOTROPIC UNIVERSE WITH HESSENCE DARK ENERGY

2010 ◽  
Vol 19 (13) ◽  
pp. 2071-2078 ◽  
Author(s):  
SHUVENDU CHAKRABORTY ◽  
UJJAL DEBNATH
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Anisotropic Universe ◽  
Field Equations ◽  
Complex Scalar ◽  
New Approach ◽  
Bianchi I ◽  
Scale Factors ◽  
Complex Scalar Field

In this work, we have considered a noncanonical complex scalar field named hessence to play the role of quintom in anisotropic universe (particularly in the Bianchi I model) as a new approach to look into the unknown mysterious world of dark energy. We have solved the field equations by considering the power-law form of scale factors and found the potential function in terms of ϕ with some restrictions. We also show here that hessence can avoid the Q-ball formation in anisotropic universe.

scholarly journals Unruh-DeWitt detector responses for complex scalar fields in de Sitter spacetime

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Md Sabir Ali ◽  
Sourav Bhattacharya ◽  
Kinjalk Lochan
Keyword(s):  
Scalar Field ◽  
Response Function ◽  
Scalar Fields ◽  
Detector Response ◽  
Massless Scalar Field ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Complex Scalar ◽  
Sitter Spacetime ◽  
Complex Scalar Field

Abstract We derive the response function for a comoving, pointlike Unruh-DeWitt particle detector coupled to a complex scalar field ϕ, in the (3 + 1)-dimensional cosmological de Sitter spacetime. The field-detector coupling is taken to be proportional to ϕ†ϕ. We address both conformally invariant and massless minimally coupled scalar field theories, respectively in the conformal and the Bunch-Davies vacuum. The response function integral for the massless minimal complex scalar, not surprisingly, shows divergences and accordingly we use suitable regularisation scheme to find out well behaved results. The regularised result also contains a de Sitter symmetry breaking logarithm, growing with the cosmological time. Possibility of extension of these results with the so called de Sitter α-vacua is discussed. While we find no apparent problem in computing the response function for a real scalar in these vacua, a complex scalar field is shown to contain some possible ambiguities in the detector response. The case of the minimal and nearly massless scalar field theory is also briefly discussed.

Coexistence of early-time inflation and late-time acceleration with scalar fields in theory of F(G,T) gravity

2018 ◽  
Vol 27 (08) ◽  
pp. 1850078 ◽  
Author(s):  
A. I. Keskin
Keyword(s):  
Scalar Field ◽  
Source Term ◽  
Friedmann Equation ◽  
Early Time ◽  
Scalar Fields ◽  
Momentum Tensor ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Late Time Acceleration ◽  
The Universe

In this study, we discuss coexistence of the early-time inflation and the late-time acceleration of the universe in the context of the theory of [Formula: see text] gravity with scalar field which is minimally coupled with the gravity, where [Formula: see text] is the gauss bonnet invariant and [Formula: see text] is the trace of energy–momentum tensor (EMT). We reconstruct the Friedmann equation (FE) and then search for the real value of a particular model [Formula: see text], where [Formula: see text] and [Formula: see text] are real constants. A Gauss–Bonnet system (GBS) for viable cosmologies arising from the matter-source term [Formula: see text] and the scalar field, is obtained. We find that the case [Formula: see text] together with [Formula: see text] in the system gives the late-time cosmic acceleration while the source term [Formula: see text] acts as a quintessence type of dark energy. On the other hand, the general entropy expression of the universe is obtained by making use of the first law of thermodynamics (FLT) method. After theoretically analyzing the inflation in the entropy frame, we find a new condition [Formula: see text] with [Formula: see text] in the system. Then, from the observational analysis of inflation, the spectral index parameter and the scalar-tensor ratio are calculated under the new condition. In brief, we obtain a viable cosmological system arising from some modifications such as the scalar field and the source term, which can unify the early inflation and the late-time cosmic acceleration besides the deceleration regions of the universe.

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