Abstract
Based on the effective field theory (EFT) of cosmological perturbations, we explicitly clarify the pathology in nonsingular cubic Galileon models and show how to cure it in EFT with new insights into this issue. With the least set of EFT operators that are capable to avoid instabilities in nonsingular cosmologies, we construct a nonsingular model dubbed the Genesis-inflation model, in which a slowly expanding phase (namely, Genesis) with increasing energy density is followed by slow-roll inflation. The spectrum of the primordial perturbation may be simulated numerically, which shows itself a large-scale cutoff, as the large-scale anomalies in CMB might be a hint for.
Highlights
Prior to LMR’s work, studies were made along other lines
In this paper, we explore the nonsingular cosmology within the framework of the Effective Field Theory (EFT) of cosmological perturbations
We have reformulated the LMR no-go theorem [33] for the cubic Galileon in the framework of EFT, which indicates the pathologies in nonsingular cosmological models based on the cubic Galileon are inevitable
Summary
Where N and N i are the lapse function and shift vector, and hij is the 3-dimentional spatial metric. All the coefficients are allowed to vary with t, with the dimension [mi] = 1, [λi] = 0, so as to make the action dimensionless. In this action we define δKμν = Kμν − HHμν, δK = K − 3H, with the induced metric Hμν ≡ gμν + nμnν and the normal vector is defined as nμ ≡ (−N, 0, 0, 0). Varying the first line of action eq (2.2) with respect to N and a, one can get the two equations: 3Mp2[f (t)H2 + f(t)H] = c(t) + Λ(t) , −Mp2[2f (t)H + 3f (t)H2 + 2f(t)H + f(t)] = c(t) − Λ(t). For the case with non-minimal coupling, f (t) is nontrivial, a more complicated constraint will be imposed on c(t) and Λ(t)
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