In this paper, we examine the cosmological viability of a light mass galileon field consistent wi... more In this paper, we examine the cosmological viability of a light mass galileon field consistent with local gravity constraints. The minimal, L3 = φ(∂µφ) 2 , massless galileon field requires an additional term in order to give rise to a viable ghost free late time acceleration of Universe. The desired cosmological dynamics can either be achieved by incorporating an additional terms in the action such as (L4, L5) − the higher order galileon Lagrangians or by considering a light mass fieldà la galileon field potential. We analyse the second possibility and find that: (1) The model produces a viable cosmology in the regime where the non-linear galileon field is subdominant, (2) The Vainshtein mechanism operates at small scales where the non-linear effects become important and contribution of the field potential ceases to be significant. Also the small mass of the field under consideration is protected against strong quantum corrections thereby providing quantum stability to the system.
We study the motion of a BPS D3-brane in the N S5-brane ring background. The radion field becomes... more We study the motion of a BPS D3-brane in the N S5-brane ring background. The radion field becomes tachyonic in this geometrical set up. We investigate the potential of this geometrical tachyon in the cosmological scenario for inflation as well as dark energy. We evaluate the spectra of scalar and tensor perturbations generated during tachyon inflation and show that this model is compatible with recent observations of Cosmic Microwave Background (CMB) due to an extra freedom of the number of N S5-branes. It is not possible to explain the origin of both inflation and dark energy by using a single tachyon field, since the energy density at the potential minimum is not negligibly small because of the amplitude of scalar perturbations set by CMB anisotropies. However geometrical tachyon can account for dark energy when the number of N S5-branes is large, provided that inflation is realized by another scalar field.
We investigate a string-inspired scenario associated with a rolling massive scalar field on D-bra... more We investigate a string-inspired scenario associated with a rolling massive scalar field on D-branes and discuss its cosmological implications. In particular, we discuss cosmological evolution of the massive scalar field on the ant-D3 brane of KKLT vacua. Unlike the case of tachyon field, because of the warp factor of the anti-D3 brane, it is possible to obtain the required level of the amplitude of density perturbations. We study the spectra of scalar and tensor perturbations generated during the rolling scalar inflation and show that our scenario satisfies the observational constraint coming from the Cosmic Microwave Background anisotropies and other observational data. We also implement the negative cosmological constant arising from the stabilization of the modulus fields in the KKLT vacua and find that this leads to a successful reheating in which the energy density of the scalar field effectively scales as a pressureless dust. The present dark energy can be also explained in our scenario provided that the potential energy of the massive rolling scalar does not exactly cancel with the amplitude of the negative cosmological constant at the potential minimum.
Quintessential inflation describes a scenario in which both inflation and dark energy (quintessen... more Quintessential inflation describes a scenario in which both inflation and dark energy (quintessence) are described by the same scalar field. In conventional braneworld models of quintessential inflation gravitational particle production is used to reheat the universe. This reheating mechanism is very inefficient and results in an excessive production of gravity waves which violate nucleosynthesis constraints and invalidate the model. We describe a new method of realizing quintessential inflation on the brane in which inflation is followed by 'instant preheating' (Felder, Kofman & Linde 1999). The larger reheating temperature in this model results in a smaller amplitude of relic gravity waves which is consistent with nucleosynthesis bounds. The relic gravity wave background has a 'blue' spectrum at high frequencies and is a generic byproduct of successful quintessential inflation on the brane.
We review in detail a number of approaches that have been adopted to try and explain the remarkab... more We review in detail a number of approaches that have been adopted to try and explain the remarkable observation of our accelerating universe. In particular we discuss the arguments for and recent progress made towards understanding the nature of dark energy. We review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence, tachyon, phantom and dilatonic models. The importance of cosmological scaling solutions is emphasized when studying the dynamical system of scalar fields including coupled dark energy. We study the evolution of cosmological perturbations allowing us to confront them with the observation of the Cosmic Microwave Background and Large Scale Structure and demonstrate how it is possible in principle to reconstruct the equation of state of dark energy by also using Su...
We consider the fate of future singularities in the effective dynamics of loop quantum cosmology.... more We consider the fate of future singularities in the effective dynamics of loop quantum cosmology. Non-perturbative quantum geometric effects which lead to ρ 2 modification of the Friedmann equation at high energies result in generic resolution of singularities whenever energy density ρ diverges at future singularities of Friedmann dynamics. Such quantum effects lead to the avoidance of a Big Rip, which is followed by a recollapsing universe stable against perturbations. Resolution of sudden singularity, the case when pressure diverges but energy density approaches a finite value depends on the ratio of the latter to a critical energy density of the order of Planck. If the value of this ratio is greater than unity, the universe escapes the sudden future singularity and becomes oscillatory.
We study a dark energy scenario in the presence of a tachyon field φ with potential V (φ) and a b... more We study a dark energy scenario in the presence of a tachyon field φ with potential V (φ) and a barotropic perfect fluid. The cosmological dynamics crucially depends on the asymptotic behavior of the quantity λ = −MpV φ /V 3/2. If λ is a constant, which corresponds to an inverse square potential V (φ) ∝ φ −2 , there exists one stable critical point that gives an acceleration of the universe at late times. When λ → 0 asymptotically, we can have a viable dark energy scenario in which the system approaches an "instantaneous" critical point that dynamically changes with λ. If |λ| approaches infinity asymptotically, the universe does not exhibit an acceleration at late times. In this case, however, we find an interesting possibility that a transient acceleration occurs in a regime where |λ| is smaller than of order unity.
This review on dark energy is intended for a wider audience, beginners as well as experts. It con... more This review on dark energy is intended for a wider audience, beginners as well as experts. It contains important notes on various aspects of dark energy and its alternatives. The section on Newtonian cosmology followed by heuristic arguments to capture the pressure effects allows us to discuss the basic features of physics of cosmic acceleration without actually resorting to the framework of general theory of relativity. The brief discussion on observational aspects of dark energy is followed by a detailed exposition of underlying features of scalar field dynamic relevant to cosmology. The review includes pedagogical presentation of generic features of models of dark energy and its possible alternatives.
We review the recent attempts of unifying inflation with quintessence. It appears natural to join... more We review the recent attempts of unifying inflation with quintessence. It appears natural to join the two ends in the framework of brane world cosmology. The models of quintessential inflation belong to the class of non-oscillatory models for which the mechanism of conventional reheating does not work. Reheating through gravitational particle production is inefficient and leads to the excessive production of relic gravity waves which results in the violation of nucleosynthesis constraint. The mechanism of instant preheating is quite efficient and is suitable for brane world quintessential inflation. The model is shown to be free from the problem of excessive production of gravity waves. The prospects of Gauss-Bonnet brane world inflation are also briefly indicated.
We present a brief review of various approaches to late time acceleration of universe. The cosmol... more We present a brief review of various approaches to late time acceleration of universe. The cosmological relevance of scaling solutions is emphasized in case of scalar field models of dark energy. The underlying features of a variety of scalar field models is highlighted. Various alternatives to dark energy are discussed including the string curvature corrections to Einstein-Hilbert action, higher dimensional effects, non-locally corrected gravity and f (R) theories of gravity. The recent developments related to f (R) models with disappearing cosmological constant are reviewed. I. INTRODUCTION The accelerated expansion has played a very important role in the history of our universe. Universe is believed to have passed through inflationary phase at early epochs and there is a growing faith that it is accelerating at present. The late time acceleration of the universe, which is directly supported by supernovae observations, and indirectly, through observations of the microwave background, large scale structure and its dynamics, weak lensing and baryon oscillations, poses one of the most important challenges to modern cosmology. Einstein equations in their original form, with an energy-momentum tensor for standard matter on the right hand side, cannot account for the observed accelerated expansion of universe. The standard lore aimed at capturing this important effect is related to the introduction of the energy-momentum tensor of an exotic matter with large negative pressure dubbed dark energy in the Einstein equations. The simplest known example of dark energy (for recent reviews, see [1]) is provided by the cosmological constant Λ. It does not require adhoc assumption for its introduction, as is automatically present in the Einstein equations, by virtue of the Bianchi identities. The field theoretic understanding of Λ is far from being satisfactory. Efforts have recently been made to obtain Λ in the framework of string theory, what leads to a complicated landscape of de-Sitter vacua. It is hard to believe that we happen to live in one of the 10 500 vacua predicted by the theory. One might take the simplified view that, like G, the cosmological constant Λ is a fundamental constant of the classical general theory of relativity and that it should be determined from large scale observations. It is interesting to remark that the ΛCDM model is consistent with observations at present. Unfortunately, the non-evolving nature of Λ and its small numerical value lead to a non-acceptable fine-tuning problem. We do not know how the present scale of the cosmological constant is related to Planck's or the supersymmetry breaking scale; perhaps, some deep physics is at play here that escapes our present understanding. The fine-tuning problem, associated with Λ, can be alleviated in scalar field models which do not disturb the thermal history of the universe and can successfully mimic Λ at late times. A variety of scalar fields have been investigated to this end[1]; some of them are motivated by field/string theory and the others are introduced owing to phenomenological considerations. It is quite disappointing that a scalar field description lacks predictive power; given a priori a cosmic evolution, one can always construct a field potential that would give rise to it. These models should, however, not be written off, and should be judged by the generic features which might arise from them. For instance, the tracker models have remarkable features allowing them to alleviate the fine-tuning and coincidence problems. Present data are insufficient in order to conclude whether or not the dark energy has dynamics; thus, the quest for the metamorphosis of dark energy continues[2] One can question the standard lore on fundamental grounds. We know that gravity is modified at small distance scales; it is quite possible that it is modified at large scales too where it has never been confronted with observations directly. It is therefore perfectly legitimate to investigate the possibility of late time acceleration due to modification of Einstein-Hilbert action. It is tempting to study the string curvature corrections to Einstein gravity amongst which the Gauss-Bonnet correction enjoys special status. A large number of papers are devoted to the cosmological implications of string curvature corrected gravity[3,
In this paper we analyze the cosmological dynamics of phantom field in a variety of potentials un... more In this paper we analyze the cosmological dynamics of phantom field in a variety of potentials unbounded from above. We demonstrate that the nature of future evolution generically depends upon the steepness of the phantom potential and discuss the fate of Universe accordingly.
We discuss a model in which high energy brane corrections allow a single scalar field to describe... more We discuss a model in which high energy brane corrections allow a single scalar field to describe inflation at early epochs and quintessence at late times. The reheating mechanism in the model originates from Born-Infeld matter whose energy density mimics cosmological constant at very early times and manifests itself as radiation subsequently. For most of the inflationary evolution the Born-Infeld matter remains subdominant to the the scalar field. Shortly before the end of inflation driven by the scalar field, the energy density of Born-Infeld matter starts scaling as radiation and drops by several orders of magnitudes at the epoch inflation ends. The problem of over production of gravity wave background in scenarios based upon reheating through gravitational particle production is successfully resolved by suitably fixing the initial value of radiation energy density at the end of inflation. No additional fine tuning of the parameters is required for a viable evolution.
In this paper, we carry out a study of viable cosmological models in f (R)-gravity at the backgro... more In this paper, we carry out a study of viable cosmological models in f (R)-gravity at the background level. We use observable parameters like Ω and γ to form autonomous system of equations and show that the models under consideration exhibit two different regimes in their time evolution, namely, a phantom phase followed by a quintessence like behavior. We employ statefinder parameters to emphasize a characteristic discriminative signature of these models.
... reat1 out being required in the high rate environment of a high luminosity hadron machine. Ot... more ... reat1 out being required in the high rate environment of a high luminosity hadron machine. Other crucial considerations are the extreinely wide dyii'mic range aid bandwidth requirements for tlie front-end electronics. as well ...
Physical Review D - Particles, Fields, Gravitation and Cosmology, 2013
We investigate cosmological behavior in the quasi-Dilaton non-linear massive gravity. We perform ... more We investigate cosmological behavior in the quasi-Dilaton non-linear massive gravity. We perform a detailed dynamical analysis and examine the stable late-time solutions relevant to late time cosmic acceleration. We demonstrate that a dark-energy dominated, cosmological-constant-like solution is a late attractor of the dynamics. We also analyze the evolution of the universe at intermediate times, showing that the observed epoch sequence can be easily obtained in the model under consideration. Furthermore, we study the non-singular bounce and the cosmological turnaround which can be realized for a region of the parameter space. Last but not least, we use observational data from Type Ia Supernovae (SNIa), Baryon Acoustic Oscillations (BAO) and Cosmic Microwave Background (CMB), in order to constrain the parameters of the theory. PACS numbers: 98.80.-k, 95.36.+x, 04.50.Kd
In this paper, we examine the cosmological viability of a light mass galileon field consistent wi... more In this paper, we examine the cosmological viability of a light mass galileon field consistent with local gravity constraints. The minimal, L3 = φ(∂µφ) 2 , massless galileon field requires an additional term in order to give rise to a viable ghost free late time acceleration of Universe. The desired cosmological dynamics can either be achieved by incorporating an additional terms in the action such as (L4, L5) − the higher order galileon Lagrangians or by considering a light mass fieldà la galileon field potential. We analyse the second possibility and find that: (1) The model produces a viable cosmology in the regime where the non-linear galileon field is subdominant, (2) The Vainshtein mechanism operates at small scales where the non-linear effects become important and contribution of the field potential ceases to be significant. Also the small mass of the field under consideration is protected against strong quantum corrections thereby providing quantum stability to the system.
We study the motion of a BPS D3-brane in the N S5-brane ring background. The radion field becomes... more We study the motion of a BPS D3-brane in the N S5-brane ring background. The radion field becomes tachyonic in this geometrical set up. We investigate the potential of this geometrical tachyon in the cosmological scenario for inflation as well as dark energy. We evaluate the spectra of scalar and tensor perturbations generated during tachyon inflation and show that this model is compatible with recent observations of Cosmic Microwave Background (CMB) due to an extra freedom of the number of N S5-branes. It is not possible to explain the origin of both inflation and dark energy by using a single tachyon field, since the energy density at the potential minimum is not negligibly small because of the amplitude of scalar perturbations set by CMB anisotropies. However geometrical tachyon can account for dark energy when the number of N S5-branes is large, provided that inflation is realized by another scalar field.
We investigate a string-inspired scenario associated with a rolling massive scalar field on D-bra... more We investigate a string-inspired scenario associated with a rolling massive scalar field on D-branes and discuss its cosmological implications. In particular, we discuss cosmological evolution of the massive scalar field on the ant-D3 brane of KKLT vacua. Unlike the case of tachyon field, because of the warp factor of the anti-D3 brane, it is possible to obtain the required level of the amplitude of density perturbations. We study the spectra of scalar and tensor perturbations generated during the rolling scalar inflation and show that our scenario satisfies the observational constraint coming from the Cosmic Microwave Background anisotropies and other observational data. We also implement the negative cosmological constant arising from the stabilization of the modulus fields in the KKLT vacua and find that this leads to a successful reheating in which the energy density of the scalar field effectively scales as a pressureless dust. The present dark energy can be also explained in our scenario provided that the potential energy of the massive rolling scalar does not exactly cancel with the amplitude of the negative cosmological constant at the potential minimum.
Quintessential inflation describes a scenario in which both inflation and dark energy (quintessen... more Quintessential inflation describes a scenario in which both inflation and dark energy (quintessence) are described by the same scalar field. In conventional braneworld models of quintessential inflation gravitational particle production is used to reheat the universe. This reheating mechanism is very inefficient and results in an excessive production of gravity waves which violate nucleosynthesis constraints and invalidate the model. We describe a new method of realizing quintessential inflation on the brane in which inflation is followed by 'instant preheating' (Felder, Kofman & Linde 1999). The larger reheating temperature in this model results in a smaller amplitude of relic gravity waves which is consistent with nucleosynthesis bounds. The relic gravity wave background has a 'blue' spectrum at high frequencies and is a generic byproduct of successful quintessential inflation on the brane.
We review in detail a number of approaches that have been adopted to try and explain the remarkab... more We review in detail a number of approaches that have been adopted to try and explain the remarkable observation of our accelerating universe. In particular we discuss the arguments for and recent progress made towards understanding the nature of dark energy. We review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence, tachyon, phantom and dilatonic models. The importance of cosmological scaling solutions is emphasized when studying the dynamical system of scalar fields including coupled dark energy. We study the evolution of cosmological perturbations allowing us to confront them with the observation of the Cosmic Microwave Background and Large Scale Structure and demonstrate how it is possible in principle to reconstruct the equation of state of dark energy by also using Su...
We consider the fate of future singularities in the effective dynamics of loop quantum cosmology.... more We consider the fate of future singularities in the effective dynamics of loop quantum cosmology. Non-perturbative quantum geometric effects which lead to ρ 2 modification of the Friedmann equation at high energies result in generic resolution of singularities whenever energy density ρ diverges at future singularities of Friedmann dynamics. Such quantum effects lead to the avoidance of a Big Rip, which is followed by a recollapsing universe stable against perturbations. Resolution of sudden singularity, the case when pressure diverges but energy density approaches a finite value depends on the ratio of the latter to a critical energy density of the order of Planck. If the value of this ratio is greater than unity, the universe escapes the sudden future singularity and becomes oscillatory.
We study a dark energy scenario in the presence of a tachyon field φ with potential V (φ) and a b... more We study a dark energy scenario in the presence of a tachyon field φ with potential V (φ) and a barotropic perfect fluid. The cosmological dynamics crucially depends on the asymptotic behavior of the quantity λ = −MpV φ /V 3/2. If λ is a constant, which corresponds to an inverse square potential V (φ) ∝ φ −2 , there exists one stable critical point that gives an acceleration of the universe at late times. When λ → 0 asymptotically, we can have a viable dark energy scenario in which the system approaches an "instantaneous" critical point that dynamically changes with λ. If |λ| approaches infinity asymptotically, the universe does not exhibit an acceleration at late times. In this case, however, we find an interesting possibility that a transient acceleration occurs in a regime where |λ| is smaller than of order unity.
This review on dark energy is intended for a wider audience, beginners as well as experts. It con... more This review on dark energy is intended for a wider audience, beginners as well as experts. It contains important notes on various aspects of dark energy and its alternatives. The section on Newtonian cosmology followed by heuristic arguments to capture the pressure effects allows us to discuss the basic features of physics of cosmic acceleration without actually resorting to the framework of general theory of relativity. The brief discussion on observational aspects of dark energy is followed by a detailed exposition of underlying features of scalar field dynamic relevant to cosmology. The review includes pedagogical presentation of generic features of models of dark energy and its possible alternatives.
We review the recent attempts of unifying inflation with quintessence. It appears natural to join... more We review the recent attempts of unifying inflation with quintessence. It appears natural to join the two ends in the framework of brane world cosmology. The models of quintessential inflation belong to the class of non-oscillatory models for which the mechanism of conventional reheating does not work. Reheating through gravitational particle production is inefficient and leads to the excessive production of relic gravity waves which results in the violation of nucleosynthesis constraint. The mechanism of instant preheating is quite efficient and is suitable for brane world quintessential inflation. The model is shown to be free from the problem of excessive production of gravity waves. The prospects of Gauss-Bonnet brane world inflation are also briefly indicated.
We present a brief review of various approaches to late time acceleration of universe. The cosmol... more We present a brief review of various approaches to late time acceleration of universe. The cosmological relevance of scaling solutions is emphasized in case of scalar field models of dark energy. The underlying features of a variety of scalar field models is highlighted. Various alternatives to dark energy are discussed including the string curvature corrections to Einstein-Hilbert action, higher dimensional effects, non-locally corrected gravity and f (R) theories of gravity. The recent developments related to f (R) models with disappearing cosmological constant are reviewed. I. INTRODUCTION The accelerated expansion has played a very important role in the history of our universe. Universe is believed to have passed through inflationary phase at early epochs and there is a growing faith that it is accelerating at present. The late time acceleration of the universe, which is directly supported by supernovae observations, and indirectly, through observations of the microwave background, large scale structure and its dynamics, weak lensing and baryon oscillations, poses one of the most important challenges to modern cosmology. Einstein equations in their original form, with an energy-momentum tensor for standard matter on the right hand side, cannot account for the observed accelerated expansion of universe. The standard lore aimed at capturing this important effect is related to the introduction of the energy-momentum tensor of an exotic matter with large negative pressure dubbed dark energy in the Einstein equations. The simplest known example of dark energy (for recent reviews, see [1]) is provided by the cosmological constant Λ. It does not require adhoc assumption for its introduction, as is automatically present in the Einstein equations, by virtue of the Bianchi identities. The field theoretic understanding of Λ is far from being satisfactory. Efforts have recently been made to obtain Λ in the framework of string theory, what leads to a complicated landscape of de-Sitter vacua. It is hard to believe that we happen to live in one of the 10 500 vacua predicted by the theory. One might take the simplified view that, like G, the cosmological constant Λ is a fundamental constant of the classical general theory of relativity and that it should be determined from large scale observations. It is interesting to remark that the ΛCDM model is consistent with observations at present. Unfortunately, the non-evolving nature of Λ and its small numerical value lead to a non-acceptable fine-tuning problem. We do not know how the present scale of the cosmological constant is related to Planck's or the supersymmetry breaking scale; perhaps, some deep physics is at play here that escapes our present understanding. The fine-tuning problem, associated with Λ, can be alleviated in scalar field models which do not disturb the thermal history of the universe and can successfully mimic Λ at late times. A variety of scalar fields have been investigated to this end[1]; some of them are motivated by field/string theory and the others are introduced owing to phenomenological considerations. It is quite disappointing that a scalar field description lacks predictive power; given a priori a cosmic evolution, one can always construct a field potential that would give rise to it. These models should, however, not be written off, and should be judged by the generic features which might arise from them. For instance, the tracker models have remarkable features allowing them to alleviate the fine-tuning and coincidence problems. Present data are insufficient in order to conclude whether or not the dark energy has dynamics; thus, the quest for the metamorphosis of dark energy continues[2] One can question the standard lore on fundamental grounds. We know that gravity is modified at small distance scales; it is quite possible that it is modified at large scales too where it has never been confronted with observations directly. It is therefore perfectly legitimate to investigate the possibility of late time acceleration due to modification of Einstein-Hilbert action. It is tempting to study the string curvature corrections to Einstein gravity amongst which the Gauss-Bonnet correction enjoys special status. A large number of papers are devoted to the cosmological implications of string curvature corrected gravity[3,
In this paper we analyze the cosmological dynamics of phantom field in a variety of potentials un... more In this paper we analyze the cosmological dynamics of phantom field in a variety of potentials unbounded from above. We demonstrate that the nature of future evolution generically depends upon the steepness of the phantom potential and discuss the fate of Universe accordingly.
We discuss a model in which high energy brane corrections allow a single scalar field to describe... more We discuss a model in which high energy brane corrections allow a single scalar field to describe inflation at early epochs and quintessence at late times. The reheating mechanism in the model originates from Born-Infeld matter whose energy density mimics cosmological constant at very early times and manifests itself as radiation subsequently. For most of the inflationary evolution the Born-Infeld matter remains subdominant to the the scalar field. Shortly before the end of inflation driven by the scalar field, the energy density of Born-Infeld matter starts scaling as radiation and drops by several orders of magnitudes at the epoch inflation ends. The problem of over production of gravity wave background in scenarios based upon reheating through gravitational particle production is successfully resolved by suitably fixing the initial value of radiation energy density at the end of inflation. No additional fine tuning of the parameters is required for a viable evolution.
In this paper, we carry out a study of viable cosmological models in f (R)-gravity at the backgro... more In this paper, we carry out a study of viable cosmological models in f (R)-gravity at the background level. We use observable parameters like Ω and γ to form autonomous system of equations and show that the models under consideration exhibit two different regimes in their time evolution, namely, a phantom phase followed by a quintessence like behavior. We employ statefinder parameters to emphasize a characteristic discriminative signature of these models.
... reat1 out being required in the high rate environment of a high luminosity hadron machine. Ot... more ... reat1 out being required in the high rate environment of a high luminosity hadron machine. Other crucial considerations are the extreinely wide dyii'mic range aid bandwidth requirements for tlie front-end electronics. as well ...
Physical Review D - Particles, Fields, Gravitation and Cosmology, 2013
We investigate cosmological behavior in the quasi-Dilaton non-linear massive gravity. We perform ... more We investigate cosmological behavior in the quasi-Dilaton non-linear massive gravity. We perform a detailed dynamical analysis and examine the stable late-time solutions relevant to late time cosmic acceleration. We demonstrate that a dark-energy dominated, cosmological-constant-like solution is a late attractor of the dynamics. We also analyze the evolution of the universe at intermediate times, showing that the observed epoch sequence can be easily obtained in the model under consideration. Furthermore, we study the non-singular bounce and the cosmological turnaround which can be realized for a region of the parameter space. Last but not least, we use observational data from Type Ia Supernovae (SNIa), Baryon Acoustic Oscillations (BAO) and Cosmic Microwave Background (CMB), in order to constrain the parameters of the theory. PACS numbers: 98.80.-k, 95.36.+x, 04.50.Kd
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Papers by M. Sami