Late time behaviors of the expanding universe in the IIB matrix model

The accelerated expansion of the large-scale universe can be explained in various ways. There are various modifications, and each of them makes an attempt to give its own explanation of the physics behind it. It is well known that modern cosmology is full of various phenomenological assumptions to obtain comprehensive results comparable with observational data. General Relativity is the main theory of gravity and proposed modifications compared to it, giving a hope to find explanations of phenomenological assumptions. f(T) theory of gravity is one of the options. In this paper, we will consider a particular example of f(T) theory and study the effects of various interactions on a cosmological model. Phase space analysis is used to have a qualitative understanding of the late-time behavior of the suggested cosmological models. During our study, we found that among phenomenological models suggested in this paper, we have cosmological models being in good agreement with the observational data. Moreover, study of the behavior of the deceleration parameter q showed a phase transition from a decelerated expanding universe to the accelerated (recent) expanding universe. On the other hand, for the parameters of the models giving the mentioned phase transition, we have estimated the present day values of statefinder parameters (r, s).

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Scale factor — Cosmic time relation and occurrences of future cosmic singularities with different redshift parametrizations of dark energy EoS-s

Modern Physics Letters A ◽

10.1142/s0217732319502286 ◽

2019 ◽

Vol 34 (28) ◽

pp. 1950228

Author(s):

Swetalina Bhowmik ◽

Ritabrata Biswas

Keyword(s):

Dark Energy ◽

Equation Of State ◽

Cosmic Time ◽

Scale Factor ◽

Late Time ◽

Expanding Universe ◽

Unknown Parameters ◽

Time Relation

While modeling our late time cosmically accelerated universe, it is popular to involve different dark energy (DE) models, the equation of state (EoS) of which can be taken as a function of the redshift and some unknown parameters. Barboza and Alcaniz have proposed one such kind of DE EoS model. We use some new parametrizations like Feng, Shen, Li, Li I and II and Polynomial parametrizations to get more accurate concepts about the fate of our expanding universe. We try to find how the hypothesis of the fate of our universe behaves in the above background of DE models. Possibilities of occurrences of future cosmic singularities are studied.

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(3+1)-DIMENSIONAL EXPANDING UNIVERSE FROM A LORENTZIAN MATRIX MODEL FOR SUPERSTRING THEORY IN (9+1)-DIMENSIONS

International Journal of Modern Physics A ◽

10.1142/s0217751x13400022 ◽

2013 ◽

Vol 28 (03n04) ◽

pp. 1340002

Author(s):

JUN NISHIMURA

Keyword(s):

Monte Carlo ◽

Real Time ◽

Matrix Model ◽

Critical Time ◽

Expanding Universe ◽

Superstring Theory ◽

The Real ◽

Time Dynamics

We study the Lorentzian version of the type IIB matrix model as a nonperturbative formulation of superstring theory in (9+1)-dimensions. Monte Carlo results show that not only space but also time emerges dynamically in this model. Furthermore, the real-time dynamics extracted from the matrices turns out to be remarkable: 3 out of 9 spatial directions start to expand at some critical time. This can be interpreted as the birth of our Universe.

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On the emergence of an expanding universe from a Lorentzian matrix model

Progress of Theoretical and Experimental Physics ◽

10.1093/ptep/ptaa128 ◽

2020 ◽

Vol 2020 (10) ◽

Author(s):

F R Klinkhamer

Keyword(s):

Matrix Model ◽

Numerical Results ◽

Expanding Universe ◽

Present Evidence ◽

Effective Metric ◽

The Universe ◽

Origin Of The Universe

Abstract We present evidence that recent numerical results from the reduced classical equations of the Lorentzian IIB matrix model can be interpreted as corresponding to the emergence of an expanding universe. In addition, we propose an effective metric to describe the emerging (3+1)D spacetime. This metric gives, at all times, finite values for the Ricci and Kretschmann curvature scalars. With these results, we are able to give a heuristic discussion of the origin of the Universe in the context of the IIB matrix model.

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