We present nonsingular, homogeneous and isotropic bouncing solutions of the conformal Galileon model. show that such necessarily begin with a radiation-dominated contracting phase. This is followed by quintom scenario in which background equation state crosses cosmological constant boundary allowing for nonsingular bounce turn Galilean Genesis. analyze spectrum perturbations this background. Our results fluctuations evolve smoothly without any pathology, but adiabatic modes form blue tilted...

We study the cosmology of a Lee-Wick type scalar field theory. First, we consider homogeneous and isotropic background solutions find that they are nonsingular, leading to cosmological bounces. Next, analyze spectrum perturbations which result from this model. Unless either potential theory or initial conditions finely tuned, it is impossible obtain have sufficiently long period inflation after bounce. More interestingly, however, in generic noninflationary bouncing cosmology, created...

In this paper, we explore the nonsingular cosmology within framework of Effective Field Theory(EFT) cosmological perturbations. Due to recently proved no-go theorem, any models based on cubic Galileon suffer from pathologies. We show how EFT could help us clarify origin and offer solutions break no-go. Particularly, point out that gradient instability can be removed by using some spatial derivative operators in EFT. Based description, obtain a realistic healthy model, perturbation spectrum...

We investigate nonsingular bounce realizations in the framework of ghost-free generalized Galileon cosmology, which furthermore can be free anisotropy problem. Considering an ekpyroticlike potential we obtain a total equation state larger than 1 contracting phase, is necessary for evolution to stable against small anisotropic fluctuations. Since such large forbids field generate desired form perturbations, additionally introduce curvaton general produce observed nearly scale-invariant...

Based on the effective field theory (EFT) of cosmological perturbations, we explicitly clarify pathology in nonsingular cubic Galileon models and show how to cure it EFT with new insights into this issue. With least set operators that are capable avoid instabilities cosmologies, construct a model dubbed Genesis-inflation model, which slowly expanding phase (namely, Genesis) increasing energy density is followed by slow-roll inflation. The spectrum primordial perturbation may be simulated...

A quintom universe with an equation of state crossing the cosmological constant boundary can provide a bouncing solution dubbed bounce and thus resolve big bang singularity. In this paper, we investigate perturbations both analytically numerically. We find that fluctuations in dominant mode post-bounce expanding phase couple to growing pre-bounce contracting phase.

In this paper we study in detail the sound speed — [Formula: see text], which is directly related to classical perturbations of dynamical dark energy (DE). We consider especially case with an equation state crossing cosmological constant boundary, and show its implications for cosmic microwave background (CMB) anisotropy. With present observational data on CMB, Type Ia supernova (SNIa) galaxy clustering, perform a global analysis constrain DE, using Markov chain Monte Carlo method. find that...

We study a nonsingular bounce inflation model, which can drive the early universe from contracting phase, into an ordinary inflationary followed by reheating process. Besides that avoided Big-Bang singularity appears in standard cosmological scenario, we make use of Horndesky theory and design kinetic potential forms lagrangian, so neither two big problems bouncing cosmology, namely ghost anisotropy problems, will appear. The perturbations be generated either phase or where latter power...

It is well known that a primordial black hole (PBH) can be generated in the inflation process of early universe, especially when field has number non-trivial features could break slow-roll condition. In this study, we investigate toy model with bumpy potential, which one or several bumps. We determined potential multi-bump generate power spectra multi-peaks small-scale region, turn predict generation holes various mass ranges. also consider two possibilities PBH formation by spherical and...

$f(Q)$ gravity is an extension of the symmetric teleparallel equivalent to general relativity. We demonstrate Hamiltonian analysis with fixing coincident gauge condition. Using standard Dirac-Bergmann algorithm, we show that has 8 physical degrees freedom. This result reflects diffeomorphism symmetry completely broken due fixing. Moreover, in terms perturbations, discuss possible mode decomposition these

A primordial black hole (PBH) is interesting to people for its ability of explaining dark matter as well supermassive astrophysical objects. In the normal inflation scenario, generation PBHs usually requires an enhanced power spectrum scalar perturbation at end era, which expected when dispersion relation inflaton field gets modified. this work, we study a kind model called Dirac-Born-Infeld-inspired nonminimal kinetic coupling (DINKIC) model, where modified by square root existing in...

$f(Q)$ gravity is an extension of the symmetric teleparallel equivalent to general relativity (STEGR). This work shows that based on scalar-nonmetricity formulation, a scalar mode in has negative kinetic energy. conclusion holds regardless coincident gauge frequently used STEGR and gravity. To study mode, we further consider covariant as special class higher-order tensor (HOST) theory rewrite four fields, which play role St\"ueckelberg fields associated with diffeomorphism, by vector fields....

In this paper, we consider a model of inflationary cosmology with inflation preceded by bounce and study its primordial curvature perturbations. Our gives rise to power spectrum feature oscillation on large scales compared the nearly scale-invariant generated traditional slow-rolling model. This effect changes cosmic microwave background temperature scale structure matter spectrum. Further, detailed simulation will show that in some models signal might be detectable forthcoming observations,...

It is of great interest to connect cosmology in the early universe Standard Model particle physics. In this paper, we try construct a bounce inflation model with standard Higgs boson, where one loop correction taken into account effective potential field. model, Galileon term has been introduced eliminate ghost mode when happens. Moreover, due fact that Fermion can make part negative, naturally obtains large equation state(EoS) parameter contracting phase, which anisotropy problem. After...

We examine various entropic inflation scenarios, under the light of eternality. After describing realization and normal condition for to last at background level, we investigate conditions eternal with effect thermal fluctuations produced from standard radiation holographic screen. Furthermore, incorporate stochastic quantum through a phenomenological, Langevin analysis, studying whether they can affect In single-holographic-screen scenarios eternality be easily obtained, while in...

We show a curvaton model, in which the has nonminimal derivative coupling to gravity. Thanks such coupling, we find that scale-invariance of perturbations can be achieved for arbitrary values equation-of-state background, provided it is nearly constant. also discussed about tensor perturbations, local non-Gaussianities generated by as well adiabatic are transferred from field during decay.

In the framework of a single scalar field quintom model with higher derivative, we construct in this paper dark energy which equation state (EOS) $w$ crosses over cosmological constant boundary. Interestingly during evolution universe $w<-1$ happens just for period time distinguished feature that starts value above -1, transits into $w<-1$, then comes back to $w>-1$. This avoids Big Rip jeopardy induced by $w<-1$.

A nonminimal coupling single scalar field theory, when transformed from Jordan frame to Einstein frame, can act like a minimal one. Making use of this property, we investigate how theory with scale-invariant power spectrum could be reconstructed its counterpart, which applied in the early universe. Thanks gravity, equation state our universe for relaxed, and relation between parameters action obtained. This approach also provides means address Big-Bang puzzles anisotropy problem model within...

We investigate the non-Gaussianities of inflation driven by a single scalar field coupling non-minimally to Einstein Gravity. assume that form is very general with an arbitrary sound speed. For convenience study, we take subclass non-minimal term linear Ricci $R$. define parameter $\mu\equiv\epsilon_h/\epsilon_\theta$ where $\epsilon_h$ and $\epsilon_\theta$ are two kinds slow-roll parameters, obtain dependence shape 3-point correlation function on $\mu$. also show estimator $F_{NL}$ in...