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In this paper, we study a cosmological model governed by a generalized scalar field nonminimally coupled to scalar torsion in the framework of teleparallel gravity. By applying the Noether symmetry approach, we attempt to explore the explicit forms of the coupling function and the scalar field potential in the Friedmann–Lemaitre–Robertson–Walker (FLRW) flat spacetime. The existence of such symmetry permits the equations of motion to take a simpler form and provides an exponential form cosmological solution for both the scale factor and scalar field. It is shown that the tachyon field behaves as the origin of inflation and contributes significantly to the accelerating expansion of the universe in the early times. While, in the late times, gravitational sources are a pressureless matter field together with the tachyon field, which plays the essential role of dark energy and is the origin of deceleration-acceleration phase transition. Later on, it is also shown that the present model contains a cosmological degeneracy in the sense that different coupling parameters and tachyonic potentials can contribute to the same cosmological behaviors such as the cosmic acceleration, age, equation of state and mean Hubble of FLRW universe. [ABSTRACT FROM AUTHOR]

In this paper, a generalized tachyonic dark energy scenario is presented in the framework of a homogeneous and isotropic Friedmann–Lemaître–Robertson–Walker (FLRW) flat universe, in which a noncanonical scalar field is coupled to gravity nonminimally. By utilizing the Noether symmetry method, we found the explicit form of both potential density and coupling function, as a function of the scalar field. It is found that the tachyon field acts as the source of inflation and accelerates the evolution of the universe in the early times considerably. While, in the late times, gravitational sources are a pressureless matter field together with the tachyon field, which is the nature of dark energy and plays an essential role in the deceleration-acceleration phase transition of the universe. Further, the role of the coefficient function of tachyon potential, alongside the potential, is considered in the evolution of the universe. It is shown that this model involves a cosmological degeneracy in the sense that different coupling parameters and tachyonic potentials may be equivalent to the same cosmological standards such as the cosmic acceleration, age, equation of state and mean Hubble of the FLRW universe. The physical characteristics of the main cosmological observables are studied in detail, which suggests that the generalized tachyon field is a remarkable dark energy candidate. [ABSTRACT FROM AUTHOR]

One of the most important issues in modern cosmology is understanding the origin of the accelerated expansion of the universe, known as "dark energy". The scalar–tensor model is one of the most interesting candidates for describing dark energy. In this paper, we investigate the non-canonical scalar model, which is written in the framework of Chameleon models. In this model, the scalar field is coupled to a mass density ρ m under an arbitrary g (ϕ) coupling function. We study the cosmological aspect of this model according to its Chameleon state and we conclude that for high densities, the mass of the Chameleon field becomes larger, so its effect will not be seen in high-density areas. We also examine the dynamical behavior of this model for different coupling functions and potentials. According to the dynamic behavior of the model, we can conclude that using this model can explain the accelerated expansion of the universe. Finally, we investigate the tensor perturbations in this model and show that the mass of the gravitational waves obtained in the framework of this model can be in good agreement with the observations. [ABSTRACT FROM AUTHOR]