Abstract
We examine observational constraints on single-field inflation in which the inflaton is a composite field stemming from a four-dimensional strongly interacting field theory. We confront the predictions with the Planck and very recent BICEP2 data. In the large non-minimal coupling regions, we discover for the minimal composite inflationary model that the predictions lie well inside the joint 68% CL for thePlanck data, but is in tension with the recent BICEP2 observations.In the case of the glueball inflationary model, the predictions satisfy the Planck results. However, this model can produce a large tensor-to-scalar ratio consistent with the recent BICEP2 observationsif the number of e-foldings is slightly smaller than the range commonly used. For a super Yang-Mills paradigm, we discover that the predictions satisfy the Planck data,and surprisingly a large tensor-to-scalar ratio consistent with the BICEP2 results can also be producedfor an acceptable range of the number of e-foldings and of the confining scale. In the small non-minimal coupling regions, all of the models can satisfy the BICEP2 results.However, the predictions of the glueball and superglueball inflationary models cannot satisfy the observational bound on the amplitude of the curvature perturbation launched by Planck,and the techni-inflaton self-coupling in the minimal composite inflationary model is constrained to be extremely small.
Highlights
Other relevant parameters are the running of scalar spectral index α ≡ dns/d ln k and the spectral index for tensor perturbations nT
The general action for composite inflation in the Jordan frame takes the form for scalar-tensor theory of gravity as 1
We write the general action for the composite inflation in the form of scalar-tensor theory of gravity in which the inflaton non-minimally couples to gravity
Summary
It has already been shown that cosmic inflation can be driven by four-dimensional strongly interacting theories non-minimally coupled to gravity [17, 18, 19]. The general action for composite inflation in the Jordan frame takes the form for scalar-tensor theory of gravity as 1. Where D is the mass dimension of the composite field Φ, G0 is a constant and 1/D2 is introduced for later simplification. We write the potential in the following form: V(Φ) = Φ4/D f (Φ) with Φ ≡ φD ,. The non-minimal coupling to gravity is signified by the dimensionless coupling ξ. We write the general action for the composite inflation in the form of scalar-tensor theory of gravity in which the inflaton non-minimally couples to gravity. According to the above action, the Friedmann equation and the evolution equations for the background field are respectively given by
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