Tensions in the ΛCDM and vacuum dynamics

2018 ◽  
Vol 33 (31) ◽  
pp. 1844009 ◽  
Author(s):  
Joan Solà Peracaula
Keyword(s):  
Dark Energy ◽  
Structure Formation ◽  
Hubble Parameter ◽  
Point Of View ◽  
Vacuum Model ◽  
Local Measurements ◽  
Cosmological Data ◽  
Dynamical Dark Energy ◽  
Phenomenological Point ◽  
Better Than

Recent analyses of modern cosmological data show that the [Formula: see text] hypothesis, despite being the canonical framework, might well not be the most favored one from the phenomenological point of view. A number of persisting tensions with the observations (particularly with the data on structure formation and the local measurements of the Hubble parameter) indicate that the concordance or [Formula: see text]CDM model of cosmology might be in trouble. The combined fit to SNIa+BAO+H(z)+LSS+BBN+CMB observables shows that the performance of the [Formula: see text]CDM is not as good as could be expected, and in fact it may lag behind the fitting outcome from dynamical dark energy (DDE) models. A simple XCDM parameterization seems to perform better than the [Formula: see text]CDM. Furthermore, the running vacuum model (RVM) could also be superior in fitting the overall data and in smoothing out some of the mentioned tensions.

scholarly journals Dynamical dark energy: Scalar fields and running vacuum

2017 ◽  
Vol 32 (09) ◽  
pp. 1750054 ◽  
Author(s):  
Joan Solà ◽  
Adrià Gómez-Valent ◽  
Javier de Cruz Pérez
Keyword(s):  
Dark Energy ◽  
Scalar Fields ◽  
Cosmic Acceleration ◽  
Field Approach ◽  
Hubble Rate ◽  
Representative Model ◽  
Cosmological Data ◽  
Energy Scalar ◽  
Dynamical Dark Energy ◽  
Better Than

Recent analyses in the literature suggest that the concordance [Formula: see text]CDM model with rigid cosmological term, [Formula: see text] may not be the best description of the cosmic acceleration. The class of “running vacuum models”, in which [Formula: see text] evolves with the Hubble rate, has been shown to fit the string of SNIa + BAO + H(z) + LSS + CMB data significantly better than the [Formula: see text]CDM. Here, we provide further evidence on the time-evolving nature of the dark energy (DE) by fitting the same cosmological data in terms of scalar fields. As a representative model, we use the original Peebles and Ratra potential, [Formula: see text]. We find clear signs of dynamical DE at [Formula: see text] c.l., thus reconfirming through a nontrivial scalar field approach the strong hints formerly found with other models and parametrizations.

scholarly journals Large-scale structure formation with massive neutrinos and dynamical dark energy

2014 ◽  
Vol 89 (10) ◽  
Author(s):  
Amol Upadhye ◽  
Rahul Biswas ◽  
Adrian Pope ◽  
Katrin Heitmann ◽  
Salman Habib ◽  
...  
Keyword(s):  
Dark Energy ◽  
Structure Formation ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Massive Neutrinos ◽  
Dynamical Dark Energy ◽  
Large Scale Structure Formation

scholarly journals Cosmological test on viscous bulk models using Hubble parameter measurements and type Ia supernovae data

2019 ◽  
Vol 79 (9) ◽  
Author(s):  
A. Hernández-Almada
Keyword(s):  
Hubble Parameter ◽  
Point Of View ◽  
Type Ia Supernovae ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Type Ia ◽  
Free Parameters ◽  
Ia Supernovae ◽  
The Universe ◽  
Phenomenological Point

Abstract From a phenomenological point of view, we analyze the dynamics of the Universe at late times by introducing a polynomial and hyperbolic bulk viscosity into the Einstein field equations respectively. We constrain their free parameters using the observational Hubble parameter data and the Type Ia Supernovae dataset to reconstruct the deceleration q and the jerk j parameters within the redshift region $$0<z<2.5$$0<z<2.5. At current epochs, we obtain $$q_0 = -\,0.680^{+0.085}_{-0.102}$$q0=-0.680-0.102+0.085 and $$j_0 = 2.782^{+1.198}_{-0.741}$$j0=2.782-0.741+1.198 for the polynomial model and $$q_0 = -\,0.539^{+0.040}_{-0.038}$$q0=-0.539-0.038+0.040 ($$-\,0.594^{+0.056}_{-0.056}$$-0.594-0.056+0.056) and $$j_0 = 0.297^{+0.051}_{-0.050}$$j0=0.297-0.050+0.051 ($$1.124^{+0.196}_{-0.178}$$1.124-0.178+0.196) for the tanh (cosh) model. Furthermore, we explore the statefinder diagnostic that gives us evident differences with respect to the concordance model (LCDM). According to our results this kind of models is not supported by the data over LCDM.

scholarly journals Constraints on Dynamical Dark Energy with Precision Cosmological Data

2018 ◽  
Vol 09 (02) ◽  
pp. 302-313
Author(s):  
Erick Almaraz ◽  
Axel de la Macorra
Keyword(s):  
Dark Energy ◽  
Cosmological Data ◽  
Dynamical Dark Energy

scholarly journals Dynamical dark energy after Planck CMB final release and H0 tension

2020 ◽  
Author(s):  
Weiqiang Yang ◽  
Eleonora Di Valentino ◽  
Supriya Pan ◽  
Yabo Wu ◽  
Jianbo Lu
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Hubble Space Telescope ◽  
Acoustic Oscillations ◽  
Energy Models ◽  
Bayesian Evidence ◽  
Local Measurements ◽  
Evidence Analysis ◽  
Baryon Acoustic Oscillations ◽  
Dynamical Dark Energy

Abstract In this article we compare a variety of well known dynamical dark energy models using the cosmic microwave background measurements from the 2018 Planck legacy and 2015 Planck data releases, the baryon acoustic oscillations measurements and the local measurements of H0 obtained by the SH0ES (Supernovae, H0, for the Equation of State of Dark energy) collaboration analysing the Hubble Space Telescope data. We discuss the alleviation of H0 tension, that is obtained at the price of a phantom-like dark energy equation of state. We perform a Bayesian evidence analysis to quantify the improvement of the fit, finding that all the dark energy models considered in this work are preferred against the ΛCDM scenario. Finally, among all the possibilities analyzed, the CPL model is the best one in fitting the data and solving the H0 tension at the same time. However, unfortunately, this dynamical dark energy solution is not supported by the baryon acoustic oscillations (BAO) data, and the tension is restored when BAO data are included for all the models.

scholarly journals IS DARK ENERGY FROM COSMIC HAWKING RADIATION?

2010 ◽  
Vol 25 (04) ◽  
pp. 257-267 ◽  
Author(s):  
JAE-WEON LEE ◽  
HYEONG-CHAN KIM ◽  
JUNGJAI LEE
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Hawking Radiation ◽  
Hubble Parameter ◽  
Planck Scale ◽  
Hawking Temperature ◽  
Cosmological Data

It is suggested that dark energy is the energy of the Hawking radiation from a cosmic horizon. Despite its extremely low Gibbons–Hawking temperature, this radiation could have the appropriate magnitude [Formula: see text]and the equation of state to explain the observed cosmological data if there is a Planck scale UV-cutoff, where H is the Hubble parameter.

scholarly journals Stringy-running-vacuum-model inflation: from primordial gravitational waves and stiff axion matter to dynamical dark energy

2021 ◽  
Author(s):  
Nick E. Mavromatos ◽  
Joan Solà Peracaula
Keyword(s):  
Dark Energy ◽  
Degrees Of Freedom ◽  
Domain Walls ◽  
Basic Structure ◽  
Vacuum Model ◽  
Living Fossils ◽  
Primordial Gravitational Waves ◽  
The Universe ◽  
Dynamical Dark Energy ◽  
Effective Description

AbstractIn previous works, we have derived a Running Vacuum Model (RVM) for a string Universe, which provides an effective description of the evolution of 4-dimensional string-inspired cosmologies from inflation till the present epoch. In the context of this “stringy RVM” version, it is assumed that the early Universe is characterised by purely gravitational degrees of freedom, from the massless gravitational string multiplet, including the antisymmetric tensor field. The latter plays an important role, since its dual gives rise to a ‘stiff’ gravitational axion “matter”, which in turn couples to the gravitational anomaly terms, assumed to be non-trivial at early epochs. In the presence of primordial gravitational wave (GW) perturbations, such anomalous couplings lead to an RVM-like dynamical inflation, without external inflatons. We review here this framework and discuss potential scenarios for the generation of such primordial GW, among which the formation of unstable domain walls, which eventually collapse in a non-spherical-symmetric manner, giving rise to GW. We also remark that the same type of “stiff” axionic matter could provide, upon the generation of appropriate potentials during the post-inflationary eras, (part of) the Dark Matter (DM) in the Universe, which could well be ultralight, depending on the parameters of the string-inspired model. All in all, the new (stringy) mechanism for RVM inflation preserves the basic structure of the original (and more phenomenological) RVM, as well as its main advantages: namely, a mechanism for graceful exit and for generating a huge amount of entropy capable of explaining the horizon problem. It also predicts axionic DM and the existence of mild dynamical Dark Energy (DE) of quintessence type in the present universe, both being “living fossils” of the inflationary stages of the cosmic evolution. Altogether the modern RVM appears to be a theoretically sound (string-based) approach to cosmology with a variety of phenomenologically testable consequences.

scholarly journals Direct reconstruction of dynamical dark energy from observational Hubble parameter data

2016 ◽  
Vol 14 ◽  
pp. 21-28 ◽  
Author(s):  
Zhi-E Liu ◽  
Hao-Ran Yu ◽  
Tong-Jie Zhang ◽  
Yan-Ke Tang
Keyword(s):  
Dark Energy ◽  
Hubble Parameter ◽  
Dynamical Dark Energy
Sign in / Sign up

Export Citation Format

Share Document