Interacting Holographic Dark Energy Research Articles

Reconstructing Torsion Cosmology from Interacting Holographic Dark Energy Model

We consider a cosmological model in the framework of Einstein–Cartan theory with a single scalar torsion ϕ=ϕ(t) and reconstruct the torsion model corresponding to the holographic dark energy (HDE) density. By studying the corresponding relation between the effective energy density of torsion field ρϕ and holographic dark energy density ρHDE, we naturally obtain a kind of torsion field from the interacting holographic dark energy with interaction term Q=−2ϕρm and ρm is the energy density of matter. We analyze the reconstructed torsion model and find that the torsion field behaves like the quintessence (w>−1) or quintom (exhibiting a transition from w>−1 to w<−1) dark energy, depending on the value of the model parameter c. We then perform a stability analysis according to the squared sound speed. It is shown that the model is classically stable in the current epoch for the case of c<1. We also investigate the model from the viewpoint of statefinder parameters and it turns out that the statefinder trajectories in the r−s plane behave differently for the three cases of c and also quite distinct from those of other cosmological models. From the trajectories of the statefinder pair {q,r}, we find that, for all the three cases of c, the universe has a phase transition from deceleration to acceleration, consistently with cosmological observations. In addition, we fit the reconstructed torsion model with the recent Type Ia supernovae (SNe Ia) samples, i.e., the Pantheon sample containing 1048 SNe Ia with the redshift in the range 0.01<z<2.3 and the Pantheon+ sample with 1701 light curves of 1550 distinct SNe Ia in the range 0.001<z<2.26. The analysis results show that the limits on the present fractional energy density of matter Ωm0 are completely compatible with those of the ΛCDM model obtained from the latest Planck mission observations at 68% confidence level. The mean value of c constrained from the Pantheon sample corresponds to the quintom-like scenario (i.e., c<1) and its mean value from the Pantheon+ sample corresponds to the quintessence-like scenario (i.e., c≥1). However, both of the Pantheon and Pantheon+ samples cannot distinguish the quintom-like and quintessence-like scenarios at 68% confidence level.

Constraints on active and sterile neutrinos in an interacting dark energy cosmology

We investigate the impacts of dark energy on constraining massive (active/sterile) neutrinos in interacting dark energy (IDE) models by using the current observations. We employ two typical IDE models, the interacting $w$ cold dark matter (I$w$CDM) model and the interacting holographic dark energy (IHDE) model, to make an analysis. To avoid large-scale instability, we use the parameterized post-Friedmann approach to calculate the cosmological perturbations in the IDE models. The cosmological observational data used in this work include the Planck cosmic microwave background (CMB) anisotropies data, the baryon acoustic oscillation data, the type Ia supernovae data, the direct measurement of the Hubble constant, the weak lensing data, the redshift-space distortion data, and the CMB lensing data. We find that the dark energy properties could influence the constraint limits of active neutrino mass and sterile neutrino parameters in the IDE models. We also find that the dark energy properties could influence the constraints on the coupling strength parameter $\beta$, and a positive coupling constant, $\beta>0$, can be detected at the $2.5\sigma$ statistical significance for the IHDE+$\nu_s$ model by using the all-data combination. In addition, we also discuss the "Hubble tension" issue in these scenarios. We find that the $H_0$ tension can be effectively relieved by considering massive sterile neutrinos, and in particular in the IHDE+$\nu_s$ model the $H_0$ tension can be reduced to be at the $1.28\sigma$ level.

Exploring neutrino mass and mass hierarchy in interacting dark energy models

We investigate how the dark energy properties impact the constraints on the total neutrino mass in interacting dark energy (IDE) models. In this study, we focus on two typical interacting dynamical dark energy models, i.e., the interacting $w$ cold dark matter (I$w$CDM) model and the interacting holographic dark energy (IHDE) model. To avoid the large-scale instability problem in IDE models, we apply the parameterized post-Friedmann approach to calculate the perturbation of dark energy. We employ the Planck 2015 cosmic microwave background temperature and polarization data, combined with low-redshift measurements on baryon acoustic oscillation distance scales, type Ia supernovae, and the Hubble constant, to constrain the cosmological parameters. We find that the dark energy properties could influence the constraint limits on the total neutrino mass. Once dynamical dark energy is considered in the IDE models, the upper bounds of $\sum m_\nu$ will be changed. By considering the values of $\chi^2_{\rm min}$, we find that in these IDE models the normal hierarchy case is slightly preferred over the inverted hierarchy case; for example, $\Delta\chi^2=2.720$ is given in the IHDE+$\sum m_\nu$ model. In addition, we also find that in the I$w$CDM+$\sum m_\nu$ model $\beta=0$ is consistent with current observational data inside the 1$\sigma$ range, and in the IHDE+$\sum m_\nu$ model $\beta>0$ is favored at more than 2$\sigma$ level.

Thermodynamics and holography of tachyon cosmology

Recently, we have investigated the dynamics of the universe in tachyon cosmology with non-minimal coupling to matter (Farajollahi et al. in Mod Phys Lett A 26(15):1125–1135, 2011; Phys Lett B 711(3–4)15:225–231,2012; Phys Rev D 83:124042, 2011; JCAP 10:014, 20112011; JCAP 05:017, 2011). In particular, for the interacting holographic dark energy (IHDE), the model is studied in Farajollahi et al. (Astrophys Space Sci 336(2):461–467, 2011). In the current work, a significant observational program has been conducted to unveil the model’s thermodynamic properties. Our result shows that the IHDE version of our model better fits the observational data than $$\Lambda $$ CDM model. The first and generalized second thermodynamics laws for the universe enveloped by cosmological apparent and event horizon are revisited. From the results, both first and generalized second laws, constrained by the observational data, are satisfied on cosmological apparent horizon.In addition, the total entropy is verified with the observation only if the horizon of the universe is taken as apparent horizon. Then, due to validity of generalized second law, the current cosmic acceleration is also predicted.

Holographic dark energy in chameleon tachyon cosmology

We propose in this paper an interacting holographic dark energy (IHDE) model in chameleon--tachyon cosmology by interaction between the components of the dark sectors. In the formalism, the interaction term emerges from the scalar field coupling matter lagrangian in the model rather than being inserted into the formalism as an external source for the interaction. The correspondence between the tachyon field and the holographic dark energy (HDE) densities allows to reconstruct the tachyon scalar field and its potential in a flat FRW universe. The model can show the accelerated expansion of the universe and satisfies the observational data.

Comment on ``Interacting holographic dark energy model and generalized second law of thermodynamics in a non-flat universe", by M.R. Setare (JCAP 01 (2007) 023)

Author of ref. 1, M.R. Setare (JCAP 01 (2007) 023), by redefining the event horizon measured from the sphere ofthe horizon as the system's IR cut-off for an interactingholographic dark energy model in a non-flat universe, showed thatthe generalized second law of thermodynamics is satisfied for thespecial range of the deceleration parameter. His paper includes anerroneous calculation of the entropy of the cold dark matter. Alsothere are some missing terms and some misprints in the equations ofhis paper. Here we present that his conclusion is not true and thegeneralized second law is violated for the present timeindependently of the deceleration parameter.