Holographic Dark Energy and Dark Matter Interaction in Anisotropic Bianchi Type-V Universe

In this study, we consider an holographic dark energy and dark matter interacting model in the Bianchi Type-V universe with a stretched exponential scale factor. We obtain the Hubble, shear, deceleration, and equation of state parameters based on the presented model and give the numerical solutions. We show that the anisotropy in the early universe plays an important role in the time evolution of the universe. Furthermore, we show that an interacting anisotropic model with stretched exponential scale factors can explain all epochs of the universe.

Κοσμολογία στη Θεωρία Einstein - Aether

Στην διατριβή αυτή παρουσιάζουμε αρχικά τον χώρο λύσεων των εξισώσεων πεδίου της θεωρίας Eistein-Aether για την περίπτωση του χωρόχρονου FLRW καθώς και για την περίπτωση του χωρόχρονου Locally Rotationally Symmetric (LRS) Bianchi Type III . Στην περίπτωση του FLRW βρίσκουμε ανηγμένες Λαγκρανζιανές που αναπαράγουν σωστά τις εξισώσεις κίνησης. Οι εξισώσεις αυτές δεν επιδέχονται λύσεις για όλο τον χώρο των αρχικών παραμέτρων. Οι ανηγμένες Λαγκρανζιανές συνάγονται μέσω ολοκλήρωσης των μη ουσιωδών συντεταγμένων στην ολική δράση και περιγράφουν σωστά την δυναμική οποτεδήποτε υπάρχουν λύσεις των εξισώσεων. Τελικά στην FLRW περίπτωση υπάρχει μια ανωμαλία καμπυλότητας, ενώ στην περίπτωση του Bianchi Type III υπάρχουν επιλογές του εύρους των παραμέτρων για τις οποίες δεν υπάρχει ανωμαλία καμπυλότητας. Στην συνέχεια παρουσιάζουμε τον χώρο λύσεων για τις εξισώσεις πεδίου της θεωρίας Eistein-Aether για την περίπτωση του χωρόχρονου vacuum Bianchi Type V . Βρίσκουμε τμήματα του πεδίου ορισμού των αρχικών παραμέτρων για τα οποία οι ανηγμένες εξισώσεις πεδίου δεν επιδέχονται καμία λύση. Οποτεδήποτε υπάρχουν λύσεις εξετάζεται η φυσική τους ερμηνεία μέσα απο την συμπεριφορά των βαθμωτών Ricci και Kretschmann, καθώς επίσης και η ταυτοποίηση του τελεστή ενέργειας-ορμής σε σχέση με ένα ιδανικό ρευστό. Υπάρχουν περιπτώσεις όπου δεν παρατηρείται καμία ανωμαλία και άλλες όπου το ενεργό ρευστό είναι ισοτροπικό.

Interacting holographic dark energy in Bianchi type-V and IX universes with variable deceleration parameter

In this paper, we study spatially homogeneous and anisotropic Bianchi type-V and IX universes filled with interacting dark matter and holographic dark energy. We obtained the solution of the field equations by using the variable deceleration parameter in the form [Formula: see text]. The cosmological parameters of the models like deceleration and equation of state are obtained. We observe that the deceleration parameter tends to [Formula: see text] which shows an accelerated universe, and the equation of state tends to [Formula: see text] which belongs to [Formula: see text]CDM model. Moreover, we establish the correspondence between holographic dark energy model and quintessence scalar field.

Some Bianchi type-V accelerating cosmological models in f(R,T) = f1(R) + f2(T) formalism

In this paper, we have studied the transition and physical behavior of Bianchi type-V cosmological models within the formalism of [Formula: see text] gravity. To obtain the solution of field equations and phase transition of universe consistent with recent cosmological observations, time varying deceleration parameters are considered. In this paper, we used two different scale factors of the form (i) [Formula: see text], where [Formula: see text] are constants. Here, for [Formula: see text] the universe shows transition with accelerated expansion. (ii) [Formula: see text], where [Formula: see text] and [Formula: see text] are constants. For [Formula: see text], the universe achieves a phase transition from early decelerating to current accelerating phase. The model I initially starts with quintessence scenario ([Formula: see text]) and ends up with ([Formula: see text]) as a model with cosmological constant ([Formula: see text]) as [Formula: see text]. Model II, for [Formula: see text] indicates the phantom energy scenario and for [Formula: see text], the model starts with quintessence [Formula: see text] and ends with vacuum energy scenario. A point type singularity has been observed in the derived model I. Some physical and geometrical properties of the models have been established and discussed to derive the validity of models with respect to recent astrophysical observations.

Interactions in the dark sector within the scope of Bianchi type-V model

We are building a cosmological model that has small anisotropy and curvature. For this purpose, the Bianchi type-V (BV) model with dark matter (DM) and anisotropic dark energy (DE) is considered. Assuming a law for deviation from the equation of state (Eos) of DE is linear, we study the transition from decelerated to late accelerated expansion of the Universe. In the proposed model, the linear interaction of the two components alleviates the coincidence problem of the present Universe. Examples of model parameter values compatible with observational data are given.

Probing kinematics and fate of Bianchi type V Universe

In this paper, we have constrained the cosmological parameters of Bianchi type V universe by bounding the model under consideration with recent observational [Formula: see text] and Pantheon data. It is assumed that the energy conservation law holds separately for barotropic fluid and dark energy fluid i.e. dark energy component does not interact with barotropic matter. We obtain the present value of deceleration parameter and age of universe as [Formula: see text] and 13.329 Gyrs respectively. The analysis of [Formula: see text] and jerk parameters concur that the derived model approaches [Formula: see text]CDM universe at late time. We find that estimated values of Hubble’s constant and energy density parameters have pretty consistency with their corresponding values, obtained by recent observations of WMAP and PLANCK collaborations. It is also observed that the universe shows signature flipping from decelerating to accelerating phase for transitional red-shift value [Formula: see text] in past.