arXiv subjects

Wan Il Park

Publications and source records attributed to Wan Il Park.

4 recordsLinked to original sources

arXiv2021

Axion-philic cosmological moduli

We show that string moduli have axion-philic nature owing to the model-insensitive derivative interactions arising from the Kaehler potential. The decay of a modulus into stringy axions occurs without suppression by the mass of final states. Interestingly, it turns out to hold in general not only for the scalar partner of the stringy axion but also for any other moduli. The decay into (pseudo) Nambu-Goldstone bosons (NGBs) also avoids such mass suppression if the modulus is lighter than or similar in mass to the scalar partner of the NGB. Such axion-philic nature makes string moduli a natural source of an observable amount of dark radiation in string compactifications involving ultralight stringy axions, and possibly in extensions of the Standard Model that include a cosmologically stable NGB such as the QCD axion. In the latter case, the fermionic superpartner of the NGB can also contribute to the dark matter as a feebly interacting massive particle.

hep-ph↗

arXiv2014

Implications of an axino LSP for naturalness

Both the naturalness of the electroweak symmetry breaking and the resolution of the strong CP problem may require a small Higgsino mass $μ$ generated by a realization of the DFSZ axion model. Assuming the axino is the lightest supersymmetric particle, we study its implications on $μ$ and the axion scale. Copiously produced light Higgsinos at collider (effectively only neutral NLSP pairs) eventually decay to axinos leaving prompt multi-leptons or displaced vertices which are being looked for at the LHC. We use latest LHC7+8 results to derive current limits on $μ$ and the axion scale. Various Higgsino-axino phenomenology is illustrated by comparing with a standard case without lightest axinos as well as with a more general case with additional light gauginos in the spectrum.

hep-ph↗

arXiv2011

Conformal invariance of curvature perturbation

We show that in the single component situation all perturbation variables in the comoving gauge are conformally invariant to all perturbation orders. Generally we identify a special time slicing, the uniform-conformal transformation slicing, where all perturbations are again conformally invariant to all perturbation orders. We apply this result to the delta N formalism, and show its conformal invariance.

gr-qc↗

arXiv2011

The mu-problem and axion in gauge mediation

We revisit the idea of generating the Higgs mu parameter through a spontaneously broken Peccei-Quinn (PQ) symmetry in gauge-mediated supersymmetry breaking scenario. For the messenger scale of gauge mediation higher than the PQ scale, the setup naturally generates mu ~ m_soft and the Higgs soft parameter B \leq O(m_soft) with the CP phase of B aligned to the phase of gaugino masses, while giving the PQ scale v_PQ ~ \surd (m_soft Λ), where m_soft denote the gauge-mediated gaugino or sfermion masses and Λ is the cutoff scale which can be identified as the Planck scale or the GUT scale. The PQ sector of the model results in distinctive cosmology including a late thermal inflation. We discuss the issue of dark matter and baryogenesis in the resulting thermal inflation scenario, and find that a right amount of gravitino dark matter can be produced together with a successful Affleck-Dine leptogenesis, when the gravitino mass m_{3/2} = O(100) keV.

hep-ph↗