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Jihn E. Kim

Publications and source records attributed to Jihn E. Kim.

At least 55 records · Page 3Linked to original sources
arXiv2017

The anomalous U(1) global symmetry and flavors from an SU(5) x SU(5)$'$ GUT in $Z_{12-I}$ orbifold compactification

In string compactifications, frequently there appears the anomalous U(1) gauge symmetry which belonged to E8$\times$E8 of the heterotic string. This anomalous U(1) gauge boson obtains mass at the compactification scale, just below $10^{18\,}$GeV, by absorbing one pseudoscalar (corresponding to the model-independent axion) from the second rank anti-symmetric tensor field $B_{MN}$. Below the compactification scale, there results a global symmetry U(1)$_{\rm anom}$ whose charge $Q_{\rm anom}$ is the original gauge U(1) charge. This is the most natural global symmetry, realizing the "invisible" axion. This global symmetry U(1)$_{\rm anom}$ is suitable for a flavor symmetry. In the simplest compactification model with the flipped SU(5) grand unification, we calculate all the low energy parameters in terms of the vacuum expectation values of the standard model singlets.

hep-ph↗
arXiv2017

't Hooft mechanism, anomalous gauge U(1), and "invisible" axion from string

Among solutions of the strong CP problem, the "invisible" axion in the narrow axion window is argued to be the remaining possibility among natural solutions on the smallness of $\barθ$. Related to the gravity spoil of global symmetries, some prospective "invisible" axions from theory point of view are discussed. In all these discussions including the observational possibility and cosmological constraints, including a safe domain wall problem, must be included.

hep-ph↗
arXiv2017

Naturally realized two dark Z's near the electroweak scale

Chiral representations are the key in obtaining light fermions from some ultra-violet completed theories. The well-known chiral example is one family set of fifteen chiral fields in the standard model. We find a new chiral theory SU(2)$_{\rm dark}\times$U(1)$_Q$ with sixteen chiral fields, which does not have any gauge and gravitational anomalies. The group SU(2)$_{\rm dark}\times$U(1)$_Q$ may belong to the dark sector, and we present a derivation of the spectrum from the E$_8\times$E$_8'$ hetrotic string. Necessarily, there appear two degrees at low energy: two dark Z's, or a dark Z plus a dark-photon. Being chiral, there is a chance to probe this theory at TeV accelerators. Since the model belongs to the dark sector, the way to probe it is through the kinetic mixing.

hep-ph↗
arXiv2017

Gravity wave and model-independent axion

In this short comment, we notice that the model-independent axion contribution to the graviton mass at just outside the Schwarzschild radius is completely negligible in GW150914. The model-independent axion contribution to the graviton mass at the order $10^{-22}\,$eV might be possible for merger of black holes of mass of order $2\times 10^{14}\,$kg.

hep-ph↗
arXiv2017

Hairs of discrete symmetries and gravity

Gauge symmetries are known to be respected by gravity because gauge charges carry flux lines, but global charges do not carry flux lines and are not conserved by gravitational interaction. For discrete symmetries, they are spontaneously broken in the Universe, forming domain walls. Since the realization of discrete symmetries in the Universe must involve the vacuum expectation values of Higgs fields, a string-like configuration (hair) at the intersection of domain walls in the Higgs vacua can be realized. Therefore, we argue that discrete charges are also respected by gravity.

hep-th↗
arXiv2016

Type-II Leptogenesis

I will talk on our new theory on baryogenesis through type-II leptogenesis which is different from the well-known type-I leptogenesis. I will comment on the Jarlskog phases, $δ_{\rm CKM}$ and $δ_{\rm PMNS}$, in the CKM and PMNS matrices. In the type-II leptogenesis, the PMNS phase is used for Sakharov's condition on the global quantum number generation in the Universe. For this to be effective, the SU(2)$\times$U(1) gauge symmetry must be broken during the leptogenesis epoch.

hep-ph↗
arXiv2016

Grand unification and CP violation

I will talk on my recent works related to the flavor grand unification, weak CP violation, and the phases in the CKM and PMNS matrices.

hep-ph↗
arXiv2016

CP-Conservation in QCD and why only "invisible" Axions work

Among solutions of the strong CP problem, the "invisible" axion in the narrow axion window is argued to be the remaining possibility among natural solutions on the smallness of $\barθ$. Related to the gravity spoil of global symmetries, some prospective invisible axions from theory point of view are discussed. In all these discussions, including the observational possibility, cosmological constraints must be included.

hep-ph↗
arXiv2016

A possible relation between leptogenesis and PMNS phases

We propose a new scenario for baryogenesis through leptogenesis, where the CP phase relevant for leptogenesis is connected directly to the PMNS phase(s) in the light neutrino mixing matrix. The scenario is realized in case only one CP phase appears in the full theory, originating from the complex vacuum expextation value of a standard model singlet field. In order to realize this scheme, the electroweak symmetry is required to be broken during the leptogenesis era and a new loop diagram with an intermediate $W$ boson exchange including the low energy neutrino mixing matrix should play the dominant contribution to the CP violation for leptogenesis. In this letter, we discuss the new basic mechanism, which we call type-II leptogenesis, and give an estimate for maximally reachable baryon asymmetry depending on the PMNS phases.

hep-ph↗
arXiv2016

Axionic domain wall number related to U(1)$_{\rm anom}$ global symmetry

The QCD axion with $f_a$ at an intermediate scale, 10**9-10**12 GeV, seems in conflict with the gravity spoil of global symmetries and may face the axionic domain wall problem. We point out that the string compactifications with an anomalous U(1) gauge symmetry, allowing desirable chiral matter spectra, circumvent these two problems simultaneously.

hep-ph↗
arXiv2016

Couplings between QCD axion and photon from string compactification

The QCD axion couplings of various invisible axion models are presented. In particular, the exact global symmetry U(1)$_{\rm PQ}$ in the superpotential is possible for the anomalous U(1) from string compactification, broken only by the gauge anomalies at one loop level, and is shown to have the resultant invisible axion coupling to photon, $c_{aγγ}\ge \frac83-c_{aγγ}^{\rm ch\,br}$ where $c_{aγγ}^{\rm ch\,br}\simeq 2$. However, this bound is not applicable in approximate U(1)$_{\rm PQ}$ models with sufficiently suppressed U(1)$_{\rm PQ}$-breaking superpotential terms. We also present a simple method to obtain $c_{aγγ}^0$ which is the value obtained above the electroweak scale.

hep-ph↗
arXiv2016

Is an axizilla possible for di-photon resonance?

Heavy axion-like particles, called axizillas, are simple extensions of the standard model(SM). An axizilla is required not to couple to the quarks, leptons, and Brout-Englert-Higgs doublets of the SM, but couple to the gauge anomalies of the $W^\pm, Z$ and photon. It is possible to have its branching ratios(BRs) to two photons greater than 10% and to two $Z$'s less than 10%. To have a (production cross section)$\cdot $(BR to di-photons) at a $10^{-38}\,\textrm{cm}^2$ level, a TeV scale heavy quark $Q$ is required for the gluon--quark fusion process. The decay of $Q$ to axizilla plus quark, and the subsequent decay of the axizilla to two photons can be fitted at the required level of $10^{-38}\,\textrm{cm}^2$.

hep-ph↗
arXiv2016

An ultralight pseudoscalar boson

Using a fundamental discrete symmetry, $\mathbb{Z}_N$, we construct a two-axion model with the QCD axion solving the strong-$CP$ problem, and an ultralight axion (ULA) with $m_{\rm ULA}\approx 10^{-22}\text{ eV}$ providing the dominant form of dark matter (DM). The ULA is light enough to be detectable in cosmology from its imprints on structure formation, and may resolve the small-scale problems of cold DM. The necessary relative DM abundances occur without fine tuning in constructions with decay constants $f_{\rm ULA}\sim 10^{17}\text{ GeV}$, and $f_{\rm QCD}\sim 10^{11}\text{ GeV}$. An example model achieving this has $N=24$, and we construct a range of other possibilities. We compute the ULA couplings to the Standard Model, and discuss prospects for direct detection. The QCD axion may be detectable in standard experiments through the $\vec{E}\cdot\vec{B}$ and $G\tilde{G}$ couplings. In the simplest models, however, the ULA has identically zero coupling to both $G\tilde{G}$ of QCD and $\vec{E}\cdot\vec{B}$ of electromagnetism due to vanishing electromagnetic and color anomalies. The ULA couples to fermions with strength $g\propto 1/f_{\rm ULA}$. This coupling causes spin precession of nucleons and electrons with respect to the DM wind with period $t\sim$months. Current limits do not exclude the predicted coupling strength, and our model is within reach of the CASPEr-Wind experiment, using nuclear magnetic resonance.

hep-ph↗
arXiv2015

Unifying CP violations of quark and lepton sectors

A preliminary determination of the Dirac phase in the PMNS matrix is $\dell\approx -\fracπ{2}$. A rather accurately determined Jarlskog invariant $J$ in the CKM matrix is close to the maximum. Since the phases in the CKM and PMNS matrices will be accurately determined in the future, it is an interesting problem to relate these two phases. This can be achieved in a families-unified grand unification if the weak CP violation is introduced spontaneously {\it à la} Froggatt and Nielsen at a high energy scale, where only one meaningful Dirac CP phase appears.

hep-ph↗
arXiv2015

Towards unification of GUT families

I discuss the mere 5 % of atoms in the cosmic energy pie. It is basically the chiral matter problem. Then, I review the chiral matter problem from a grand unification (GUT) point of view, and point out that anti-SU(N), easily implementable in string compactification, is a possibility. Here `anti-' means that the GUT group breaking is through the anti-symmetric tensor field(s), e.g. <Φ^{[AB]}>= <Φ_{[AB]}>. We argued for an anti-SU(7) [= SU(7) x U(1)] families-unification model from a Z(12-I) orbifold compactification. The Z(12-I) orbifold is briefly discussed and the multiplicity 2 in the T3 twisted sector is the key obtaining three chiral families. Yukawa coupling structure is shown to be promising. A numerical study shows that the anti-SU(7) model satisfies the CKM fit. It is shown that the doublet-triplet splitting is obtained naturally, where the dominant process for proton decay is by the exchange of GUT scale gauge bosons such that proton to pi-zero plus positron is the dominant channel.

hep-ph↗
arXiv2015

The CKM matrix from anti-SU(7) unification of GUT families

We estimate the CKM matrix elements in the recently proposed minimal model, anti-SU(7) GUT for the family unification, $[\,3\,]+2\,[\,2\,]+8\,[\,\bar{1}\,]$+\,(singlets). It is shown that the real angles of the right-handed unitary matrix diagonalizing the mass matrix can be determined to fit the Particle Data Group data. However, the phase in the right-handed unitary matrix is not constrained very much. We also includes an argument about allocating the Jarlskog phase in the CKM matrix. Phenomenologically, there are three classes of possible parametrizations, $\delq=α,β,$ or $γ$ of the unitarity triangle. For the choice of $\delq=α$, the phase is close to a maximal one.

hep-ph↗
arXiv2015

Towards unity of families: anti-SU(7) from Z(12-I) orbifold compactification

The problem of families, "Why are there three families of fermions?", is a long awaited question to be answered within a reasonable framework. We propose anti-SU($N$) groups for the unification of families in grand unification (GUT) groups, where the separation of color and weak gauge groups in the GUT is achieved by antisymmetric tensor Brout-Englert-Higgs boson instead of an adjoint representation. Theories of anti-SU($N$)'s are proposed for the unification of families. The minimal model is found as \antiSD \, GUT with the fermion representation [3]+2[2]+8[\bar-1]. We present an example in a Z(12-I) orbifold compactification, where the missing partner mechanism is also realized.

hep-ph↗