arXiv subjects

Jihn E. Kim

Publications and source records attributed to Jihn E. Kim.

At least 73 records · Page 4Linked to original sources

arXiv2015

Axions, strong and weak CP, and KNP inflation

I review the ideas leading to the QCD axion and also comment on the Jarlskog determinant describing the observed weak CP violation, and the axion-related Kim-Nilles-Peloso inflation. All of these use pseudoscalars, and the underlying principle is the discrete gauge symmetry either in the bottom-up or top-down approaches. Here, the effects of gravity are required to be unimportant in the low energy effective theory. String compactification is safe from the gravity spoil of global symmetries and some examples from string compactification are commented.

hep-ph↗

arXiv2015

Perspective on completing natural inflation

We present a perspective on the inflation paths in 2-, 3-,,, N-flation models based on the ultraviolet completion in heterotic string theory, where a number of grand unification scale axions are used. The number of non-Abelian gauge groups for a natural inflation is restricted in string compactification, and we argue that the most plausible completion of natural inflation from a theory perspective is the 2-flation.

hep-th↗

arXiv2015

Calculation of axion-photon-photon coupling in string theory

The axion search experiments invite a plausible estimation of the axion--photon--photon coupling constant $\overline{c}_{aγγ}$ in string models with phenomenologically acceptable visible sectors. We present the calculation of $\overline{c}_{aγγ}$ with an exact Peccei-Quinn symmetry. In the Huh-Kim-Kyae $\Z_{12-I}$ orbifold compactification, we obtain $\overline{c}_{aγγ} =\frac{8}{3}$ even with a lot of singlets at the GUT scale, and the low-temperature axion search experiments will probe the QCD corrected coupling, $ {c}_{aγγ} \simeq \overline{c}_{aγγ}-1.98\simeq 0.69$.

hep-ph↗

arXiv2014

Numerical calcultaion of e-fold number from hilltop with two inflatons

We consider a cosmological inflation with two inflatons, $ϕ$ and $X$. The inflation potential is a hilltop form in the $ϕ$ space and $X$ is a sideway down-fall field in the region $ϕ\ge m$. In this model, we calculate the $e$-fold number numerically starting from the intitial point which is in the vicinity of the hilltop point. Firstly, by varying parameters and initial conditions the inflaton path field $φ$ for the BICEP2 point, $φ_{\rm BCP2}$, is found to give $ n_s\simeq 0.96$ and $r\simeq 0.16$. Next, from the point $φ_{\rm BCP2}$ to the end of inflation the e-fold number is obtained. We find a reasonable set of parameters allowing the e-fold number in the range 50-60.

hep-ph↗

arXiv2014

New confining force solution of QCD axion domain wall problem

The serious cosmological problems created by the axion-string/axion-domain-wall system in standard axion models are alleviated by positing the existence of a new confining force. The instantons of this force can generate an axion potential that erases the axion strings long before QCD effects become important, thus preventing QCD-generated axion walls from ever appearing. Axion walls generated by the new confining force would decay so early as not to contribute significantly to the energy in axion dark matter.

hep-ph↗

arXiv2014

Dark matter production in the early Universe: beyond the thermal WIMP paradigm

Increasingly stringent limits from LHC searches for new physics, coupled with lack of convincing signals of weakly interacting massive particle (WIMP) in dark matter searches, have tightly constrained many realizations of the standard paradigm of thermally produced WIMPs as cold dark matter. In this article, we review more generally both thermally and non-thermally produced dark matter (DM). One may classify DM models into two broad categories: one involving bosonic coherent motion (BCM) and the other involving WIMPs. BCM and WIMP candidates need, respectively, some approximate global symmetries and almost exact discrete symmetries. Supersymmetric axion models are highly motivated since they emerge from compelling and elegant solutions to the two fine-tuning problems of the Standard Model: the strong CP problem and the gauge hierarchy problem. We review here non-thermal relics in a general setup, but we also pay particular attention to the rich cosmological properties of various aspects of mixed SUSY/axion dark matter candidates which can involve both WIMPs and BCM in an interwoven manner. We also review briefly a panoply of alternative thermal and non-thermal DM candidates.

hep-ph↗

arXiv2014

Dark energy, QCD axion, BICEP2, and trans-Planckian decay constant

Discrete symmetries allowed in string compactification are the mother of all global symmetries which are broken at some level. We discuss the resulting pseudo-Goldstone bosons, in particular the QCD axion and a temporary cosmological constant, and inflatons. We also comment on some implications of the recent BICEP2 data.

hep-ph↗

arXiv2014

Bosonic Coherent Motions in the Universe

We mini-review the role of fundamental spin-0 bosons as bosonic coherent motion (BCM) in the Universe. The fundamental spin-0 bosons have the potential to account for the baryon number generation, cold dark matter (CDM) via BCM, dark energy, and inflation. Among these, here we focus on the CDM possibility because it can be experimentally tested with the current experimental techniques. We also comment briefly on the panoply of the other roles of spin-0 bosons.

hep-ph↗

arXiv2014

QCD Axion and Dark Energy

String allowed discrete symmetry is the mother of acceptable effective global symmetries at low energy. With this philosophy, we discuss dark energy, QCD axion, and inflation, and speculate some implications of the recent BICEP2 data.

astro-ph.CO↗

arXiv2014

High scale inflation, model-independent string axion, and QCD axion with domain wall number one

The recent BICEP2 result shows that the Universe once has gone through the vacuum with the GUT scale energy density. The implied high scale inflation nullifies the dilution idea of topological defects, strings and domain walls, of the axionic system. In particular, domain walls are disastrous if the domain wall problem with domain-wall number greater than 1 is present. We argue that the model-independent axion in string compactification with the anomalous U(1) gauge symmetry resolves the domain wall problem naturally with a symmetry principle.

hep-th↗

arXiv2014

The inflation point in U(1)$_{de}$ hilltop potential assisted by chaoton, BICEP2 data, and trans-Planckian decay constant

The recent BICEP2 report on the CMB B-mode polarization hints an early Universe energy density at the GUT scale. We add a new 'chaoton' term to our recently proposed hilltop potential to have a large tensor mode fluctuation. The chaoton field slides down from the hilltop when the inflaton field value is small so that an enough e-folding is possible. We also comment how the trans-Planckian decay constant is obtained from some discrete symmetries of ultra-violet completed models.

hep-ph↗

arXiv2014

Calculations of resonance enhancement factor in axion-search tube-experiments

It is pointed out that oscillating current density, produced due to the coupling between an external magnetic field and the cosmic axion field, can excite the TM resonant modes inside an open-ended cavity (tube). By systematically solving the field equations of axion-electrodynamics we obtain explicit expressions for the oscillating fields induced inside a cylindrical tube. We calculate the enhancement factor when a resonance condition is met. While the power obtained for TM modes replicates the previous result, we emphasize that the knowledge of explicit field configurations inside a tube opens up new ways to design axion experiments including a recent proposal to detect the induced fields using a superconducting LC circuit. In addition, as an example, we estimate the induced fields in a cylindrical tube in the presence of a static uniform magnetic field applied only to a part of its volume.

hep-ph↗

arXiv2014

Final state interaction phases using data from CP asymmetries

Evidence of physics beyond the Standard Model (SM) of particle physics might be revealed through CP violation. Experimental results from BaBar, Belle, and most recently from LHCb are very interesting in this respect. It is important to calculate various CP violation parameters within the SM. In this Letter, the final state interaction (FSI) phases with the CKM matrix are calculated using the recent experimental results from LHCb on CP violation in B0 and Bs0 meson decays. To obtain the allowed regions of the FSI phases, a simplified form of the Jarlskog determinant of the CKM matrix is used and the CP phase delta close to the maximal value of pi/2 is found. Then, the asymmetry data on B0 and Bs0 from LHCb is used to explore graphically the allowed regions of the FSI phases.

hep-ph↗

arXiv2014

Dark energy from approximate U(1)_{de} symmetry

The PLANCK observation strengthens the argument that the observed acceleration of the Universe is dominated by the invisible component of dark energy. We address how this extremely small DE density can be obtained in an ultraviolet completed theory. From two mass scales, the grand unification scale M_G and the Higgs boson mass, we parametrize this dark energy(DE). To naturally generate an extremely small DE term, we introduce an almost flat DE potential of a pseudo-Goldstone boson of an approximate global symmetry U(1)_{de} from some discrete symmetries allowed in an ultraviolet completed theory. For the DE potential to be extremely shallow, the pseudo-Goldstone boson is required not to couple to the QCD anomaly. This fixes uniquely the nonrenormalizable term generating the potential suppressed by M_G^7 in supergravity models.

hep-ph↗

arXiv2014

Modeling small dark energy scale with quintessential pseudoscalar boson

Democracy among the same type of particles is a useful paradigm in studying masses and interactions of particles with supersymmetry(SUSY) or without SUSY. This simple idea predicts the presence of massless particles. We attempt to use one of these massless pseudoscalar particles as generating the cosmological dark energy(DE) potential. To achieve the extremely shallow potential of DE, the pseudoscalar boson is required not to couple to the QCD anomaly. So, we consider two pseudoscalars, one coupling to the QCD anomaly (i.e. QCD axion) and the other not coupling to the QCD anomaly. To obtain these two pseudoscalars, we introduce two approximate global U(1) symmetries to realize them as the pseudo-Goldstone bosons of the spontaneously broken U(1)'s. These global symmetries are dictated by a gravity respected discrete symmetry. Specifically, we consider an S2(L) X S2(R) X Z(10R) example, and attempt to obtain the DE scale in terms of two observed fundamental mass scales, the grand unification scale M(G) and the electroweak scale v(ew).

hep-ph↗

arXiv2013

Abelian discrete symmetries Z_{N} and Z_{nR} from string orbifolds

We show that Abelian discrete symmetries Z_{N} and Z_{nR} from string orbifolds result by assigning vacuum expectation values(VEVs) only to specified singlets. These singlets obtaining VEVs carry the gauge charges (of the covering U(1) gauge group) as multiples of N for Z_N and n for Z_{nR}. We explicitly show this realization in a Z_{12-I} orbifold model.

hep-th↗

arXiv2013

Review of axino dark matter

We review the status of axino dark matter. Two hierarchy problems, the strong CP problem and the gauge hierarchy problem, have led to introducing into particle physics a spontaneously broken global Peccei-Quinn symmetry and a softly broken supersymmetry, respectively. Combining them implies the presence of not only an axion, but also of its scalar component, saxion, and their fermionic partner, axino. Among these, the axion and the axino are attractive dark matter candidates. Various possibilities for the axino as dark matter are discussed.

astro-ph.CO↗

arXiv2013

Natural Higgs-flavor-democracy solution of the mu problem of supersymmetry and the QCD axion

We show that the hierarchically small mu term in supersymmetric theories is a consequence of two identical pairs of Higgs doublets taking a democratic form for their mass matrix. We briefly discuss the discrete symmetry S2xS2 toward the democratic mass matrix. Then, we show that there results an approximate Peccei-Quinn symmetry and hence the value mu is related to the axion decay constant.

hep-ph↗