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Barenboim, G., & Park, W. I. (2015). Spiral inflation. Phys. Lett. B, 741, 252–255.
Abstract: We propose a novel scenario of primordial inflation in which the inflaton goes through a spiral motion starting from around the top of a symmetry breaking potential. We show that, even though inflation takes place for a field value much smaller than Planck scale, it is possible to obtain relatively large tensor-to-scalar ratio (r similar to 0.1) without fine tuning. The inflationary observables perfectly match Planck data.
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Barenboim, G., & Vives, O. (2015). Transplanckian inflation as gravity echoes. Phys. Lett. B, 748, 336–342.
Abstract: In this work, we show that, in the presence of non-minimal coupling to gravity, it is possible to generate sizeable tensor modes in single-field models without transplanckian field values. These transplanckian field values apparently needed in Einstein gravity to accommodate the experimental results may only be due to our insistence of imposing a minimal coupling of the inflaton field to gravity in a model with non-minimal couplings. We present three simple single-field models that prove that it is possible to accommodatea large tensor-to-scalar ratio without requiring transplanckian field values within the slow-roll regime.
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Barenboim, G., & Park, W. I. (2016). Peccei-Quinn field for inflation, baryogenesis, dark matter, and much more. Phys. Lett. B, 756, 317–322.
Abstract: We propose a scenario of brane cosmology in which the Peccei-Quinn field plays the role of the inflaton and solves simultaneously many cosmological and phenomenological issues such as the generation of a heavy Majorana mass for the right-handed neutrinos needed for seesaw mechanism, MSSM mu-parameter, the right amount of baryon number asymmetry and dark matter relic density at the present universe, together with an axion solution to the strong CP problem without the domain wall obstacle. Interestingly, the scales of the soft SUSY-breaking mass parameter and those of the breaking of U(1)(PQ) symmetry are lower bounded at O(10) TeV and O(10(11)) GeV, respectively.
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Barenboim, G., & Park, W. I. (2016). Gravitational waves from first order phase transitions as a probe of an early matter domination era and its inverse problem. Phys. Lett. B, 759, 430–438.
Abstract: We investigate the gravitational wave background from a first order phase transition in a matter-dominated universe, and show that it has a unique feature from which important information about the properties of the phase transition and thermal history of the universe can be easily extracted. Also, we discuss the inverse problem of such a gravitational wave background in view of the degeneracy among macroscopic parameters governing the signal.
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Barenboim, G., & Park, W. I. (2017). Impact of CP-violation on neutrino lepton number asymmetries revisited. Phys. Lett. B, 765, 371–376.
Abstract: We revisit the effect of the (Dirac) CP-violating phase on neutrino lepton number asymmetries in both mass- and flavor-basis. We found that, even if there are sizable effects on muon- and tau-neutrino asymmetries, the effect on the asymmetry of electron-neutrinos is at most similar to the upper bound set by BBN for initial neutrino degeneracy parameters smaller than order unity. We also found that, for the asymmetries in mass-basis, the changes caused by CP-violation is of sub-% level which is unlikely to be accessible neither in the current nor in the forthcoming experiments.
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