seong chan Park

• BSc, MS, PhD
• Professor at Yonsei University

We propose an explanation for the recently reported ultra-high-energy neutrino signal at KM3NeT, which lacks an identifiable astrophysical source. While decaying dark matter in the Galactic Center is a natural candidate, the observed arrival direction strongly suggests an extragalactic origin. We introduce a multicomponent dark matter scenario in w...

A bstract Non-perturbative gravitational effects induce explicit global symmetry breaking terms within axion models. These exponentially suppressed terms in the potential give a mass contribution to the axion-like particles (ALPs). In this work we investigate this scenario with a scalar field charged under a global U(1) symmetry and having a non-mi...

We examine the quasinormal modes exhibited by a massive scalar test field carrying an electric charge, oscillating in the outer region of a Reissner-Nordstr\"om de Sitter black hole. We examine the quasinormal mode effective potential throughout the black hole mass-charge phase space, finding a single-peaked barrier potential on $r_+ < r < r_c$ for...

Penrose's Strong Cosmic Censorship conjecture safeguards determinism in General Relativity. Within the initial value approach to General Relativity, proof of Strong Cosmic Censorship preservation is predicated on the unique evolution of the metric. For the Kerr-Newman family of black hole solutions, this requires the inextendability of the metric p...

In collider experiments, an event is characterized by two distinct yet mutually complementary features: the “global features” and the “local features.” Kinematic information such as the event topology of a hard process, masses, and spins of particles comprises global features spanning the entire phase space. This global feature can be inferred from...

We explore the production of gravitational waves (GW) resulting from a first-order phase transition (FOPT) in a non-minimally coupled `Dark Higgs Inflation' model. Utilizing a dark sector scalar field as the inflaton, we demonstrate how inflationary dynamics naturally set the stage for observable FOPT. These transitions, influenced by thermal and q...

Non-perturbative gravitational effects induce explicit global symmetry breaking terms within axion models. These exponentially suppressed terms in the potential give a mass contribution to the axion-like particles (ALPs). In this work we investigate this scenario with a scalar field charged under a global $U(1)$ symmetry and having a non-minimal co...

We propose a novel framework based on neural network that reformulates classical mechanics as an operator learning problem. A machine directly maps a potential function to its corresponding trajectory in phase space without solving the Hamilton equations. Most notably, while conventional methods tend to accumulate errors over time through iterative...

We study the kinetic mixing between the cosmic microwave background (CMB) photon and the birefringent dark photon. These birefringent dark photon may exist in parity-violating dark sector, for example, through the coupling to axion field. We show that the birefringence of the dark photon propagates to the CMB photon, but the resulting birefringence...

A bstract We employ the effective field theory approach to analyze the characteristics of Euclidean wormholes within axion theories. Using this approach, we obtain non-perturbative instantons in various complex scalar models with and without a non-minimal coupling to gravity, as well as models featuring the R ² term for a range of coupling values....

We introduce DeeLeMa, a deep learning-based network for the analysis of energy and momentum in high-energy particle collisions. This novel approach is specifically designed to address the challenge of analyzing collision events with multiple invisible particles, which are prevalent in many high-energy physics experiments. DeeLeMa is constructed bas...

We investigate the possibility that inflation originates from a composite field theory, in terms of an effective chiral Lagrangian involving a dilaton and pions. The walking dynamics of the theory constrain the potential in a specific way, where the anomalous dimensions of operators involving pions play a crucial role. For realistic values of the a...

We study the kinetic mixing between the cosmic microwave background (CMB) photon and the birefringent dark photon as a source of cosmic birefringence. We show that indeed the birefringence of the dark photon propagates to the CMB photon, but the resulting birefringence may not be uniform over the sky. Moreover, our investigation sheds light on the...

In axion models, the global U(1) Peccei-Quinn (PQ) symmetry is explicitly broken by nonperturbative effects of gravity, such as axionic wormholes. The gravitational violation of the PQ symmetry due to wormholes is large enough to invalidate the PQ mechanism, which is entitled as the axion quality problem. Recently, a novel solution to this quality...

We investigate the possibility that inflation originates from a composite field theory, in terms of an effective chiral Lagrangian involving a dilaton and pions. The walking dynamics of the theory constrain the potential in a specific way, where the anomalous dimensions of operators involving pions play a crucial role. For realistic values of the a...

The effects of a scalar field, known as the “assistant field,” which nonminimally couples to gravity, on single-field inflationary models are studied. The analysis provides analytical expressions for inflationary observables such as the spectral index ( n s ), the tensor-to-scalar ratio ( r ), and the local-type nonlinearity parameter ( f NL (local...

The effects of a scalar field, known as the "assistant field," which nonminimally couples to gravity, on single-field inflationary models are studied. The analysis provides analytical expressions for inflationary observables such as the spectral index ($n_s$), the tensor-to-scalar ratio ($r$), and the local-type nonlinearity parameter ($f_{\rm NL}^...

We introduce DeeLeMa, a deep learning-based network for the analysis of energy and momentum in high-energy particle collisions. This novel approach is specifically designed to address the challenge of analyzing collision events with multiple invisible particles, which are prevalent in many high-energy physics experiments. DeeLeMa is constructed bas...

We apply the Festina Lente (FL) bound on a hidden sector with U(1) gauge symmetries. Since the FL bound puts a lower bound on masses of particles charged under the U(1) gauge symmetries, it is possible to constrain the hidden sector even with a tiny coupling to the Standard Model. In particular, we focus on the phenomenological implications of the...

Recently reported anomalies in various B-meson decays and also in the anomalous magnetic moment of muon (g − 2)μ motivate us to consider a particular extension of the standard model incorporating new interactions in the lepton and quark sectors simultaneously. Our minimal choice would be the leptoquark. In particular, we take the vector leptoquark...

In axion models, the global U(1) Peccei-Quinn (PQ) symmetry is explicitly broken by non-perturbative effects of gravity such as axionic wormholes. The gravitational violation of the PQ symmetry due to wormholes is large enough to invalidate the PQ mechanism, which is entitled as the axion quality problem. Recently, a novel solution to this quality...

The running of the Higgs self coupling may lead to numerous phenomena in early universe cosmology. In this paper we introduce a scenario where the Higgs running induces turns in the trajectory passing a region with tachyonic mass, leading to a temporal tachyonic growth in the curvature power spectrum. This effect induced by the Higgs leaves phenome...

We apply the Festina Lente (FL) bound on a hidden sector with $U(1)$ gauge symmetries. Since the FL bound puts a lower bound on masses of particles charged under the $U(1)$ gauge symmetries, it is possible to constrain the hidden sector even with a tiny coupling to the Standard Model. In particular, we focus on the phenomenological implications of...

The running of the Higgs self coupling may lead to numerous phenomena in early universe cosmology. In this paper we introduce a scenario where the Higgs running induces turns in the trajectory passing a region with tachyonic mass, leading to a temporal tachyonic growth in the curvature power spectrum. This effect induced by the Higgs leaves phenome...

Conventional wisdom says that a chaotic inflation model with a power-law potential is ruled out by the recent Planck-BICEP/Keck results. We find, however, that the model can be assisted by a non-minimally coupled scalar field and still provides a successful inflation. Considering a power-law chaotic inflation model of the type $V\sim \varphi^n$ wit...

A bstract The recently suggested Festina-Lente (FL) bound provides a lower bound on the masses of U(1) charged particles in terms of the positive vacuum energy. Since the charged particle masses in the Standard Model (SM) are generated by the Higgs mechanism, the FL bound provides a testbed of consistent Higgs potentials in the current dark energy-...

We study reheating of inflationary models with general non-minimal coupling K (ϕ) R with K (ϕ) ∼ √( V (ϕ)) where R is the Ricci scalar and R is the inflaton potential. In particular, when we take the monomial potential K (ϕ) ∝ ϕ m with m ∈ℤ + , we provide general analytic expressions for cosmological observables. We consider a wide range of non-min...

The recently suggested Festina-Lente (FL) bound provides a lower bound on the masses of ${\rm U(1)}$ charged particles in terms of the positive vacuum energy. Since the charged particle masses in the Standard Model (SM) are generated by the Higgs mechanism, the FL bound provides a testbed of consistent Higgs potentials in the current dark energy-do...

We study reheating of inflationary models with general non-minimal coupling $K(\phi)R$ with $K(\phi)\sim \sqrt{V(\phi)}$ where $R$ is the Ricci scalar and $V$ is the inflaton potential. In particular, when we take the monomial potential $K(\phi) \propto \phi^m$ with $m \in \mathbb{Z}_+$, we provide general analytic expressions for cosmological obse...

Semiclassical processes such as production and decay of electroweak sphaleron in the Standard Model and also microscopic black hole in low scale gravity scenario typically involve large number of particles in final states. These large multiplicities can be distinctively seen in collisions of ultra-high-energy (UHE) neutrinos with Eν≳109 GeV and nuc...

Recently reported anomalies in various $B$ meson decays and also in the anomalous magnetic moment of muon $(g-2)$ motivate us to consider a particular extension of the standard model incorporating new interactions in lepton and quark sectors simultaneously. Our minimal choice would be leptoquark. In particular, we take vector leptoquark ($U_1$) and...

A bstract We investigate various search strategies for light vector boson X in $$ \mathcal{O} $$ O (10) MeV mass range using J/ Ψ associated channels at BESIII and Belle II: (i) J/ Ψ → η c X with 10 ¹⁰ J/ Ψs at BESIII, (ii) J/ Ψ( η c + X ) + $$ \mathrm{\ell}\overline{\mathrm{\ell}} $$ ℓ ℓ ¯ production at Belle II, and (iii) J/ Ψ + X with the displa...

A bstract We propose a scenario of spontaneous leptogenesis in Higgs inflation with help from two additional operators: the Weinberg operator (Dim 5) and the derivative coupling of the Higgs field and the current of lepton number (Dim 6). The former is responsible for lepton number violation and the latter induces chemical potential for lepton numb...

We review the recent progress in Higgs inflation focusing on Higgs-$R^2$ inflation, primordial black hole production and the $R^3$ term.

We review the recent progress in Higgs inflation focusing on Higgs-\(R^2\) inflation, primordial black hole production and the \(R^3\) term.

A novel mechanism of boosting dark matter by cosmic neutrinos is proposed. The new mechanism is so significant that the arriving flux of dark matter in the mass window $1~{\rm keV} \lesssim m_{\rm DM} \lesssim 1~{\rm MeV}$ on Earth can be enhanced by two to four orders of magnitude compared to one only by cosmic electrons. Thereby we firstly derive...

Primordial black holes are produced in a minimal UV extension to the Higgs inflation with an included R² term. We show that for parameters consistent with Standard Model measurements and Planck observation results lead to MPBH ∈ (10⁻¹⁶, 10⁻¹⁵)M☉ primordial black holes with significant abundance, which may consist the majority of dark matter.

We investigate various search strategies for light vector boson $X$ in $\mathcal{O}(10)~{\rm MeV}$ mass range using $J/\Psi$ associated channels at BESIII and Belle II: (i) $J/\Psi \to \eta_c X$ with $10^{10} J/\Psi$s at BESIII, (ii) $J/\Psi (\eta_c +X) +\ell \bar{\ell}$ production at Belle~II, and (iii) $J/\Psi +X$ with the displaced vertex in $X\...

The recently reported excess in XENON1T is explained by new leptonic forces, which are free from gauge anomalies. We focus on two scenarios with and without dark matter. In Scenario #1, the gauge boson of gauged lepton number U(1)Le−Lj, j=μ or τ provides non-standard interaction between solar neutrino and electron that enhances the number of electr...

We propose a scenario of spontaneous leptogenesis in Higgs inflation with help from two additional operators: the Weinberg operator (Dim 5) and the derivative coupling of the Higgs field and the current of lepton number (Dim 6). The former is responsible for lepton number violation and the latter induces chemical potential for lepton number. The pe...

We investigate features of the sterile neutrinos in the presence of a light gauge boson $X^\mu$ that couples to the neutrino sector. The novel bounds on the active-sterile neutrino mixings $| U_{\ell 4} |^2$, especially for tau flavor ($l = \tau$), from various collider and fixed target experiments are explored. Also, taking into account the additi...

We single out the Starobinsky model and its extensions among generic f(R) gravity as attractors at large field values for chaotic inflation. Treating a R3 curvature term as a perturbation of the Starobinsky model, we impose the phenomenological bounds on the additional term satisfying the successful inflationary predictions. We find that the scalar...

We investigate the sensitivity of Higgs(-like) inflation to higher dimensional operators in the nonminimal couplings and in the potential, both in the metric and Palatini formalisms. We find that, while inflationary predictions are relatively stable against the higher dimensional operators around the attractor point in the metric formalism, they ar...

A bstract A long-standing kinematic challenge in data analysis at hadron colliders is the determination of the masses of invisible particles. This issue is particularly relevant in searches for evidence of dark matter production, which remains one of the prominent targets of future collider experiments. In this paper, we show that the additional in...

We analyze, in a fully model-independent manner, the effects of new physics on a few semihadronic three-body meson decays of the type Pi→Pff1f2, where Pi, Pf are well chosen pseudoscalar mesons and f1,2 denote fermions out of which at least one gets detected in experiments. We find that the angular distribution of events of these decays can probe m...

A bstract We study scalar perturbations of the five-dimensional rotating black holes and find an exact solution giving exact description of the Hawking radiation. Mathematically, the full solution for this spin-zero field is expressed in terms of the prolate spheroidal wave function with complex parameters. By using the spheroidal joining factor, w...

We suggest a clockwork mechanism for a Higgs-like inflation with the non-minimal coupling term \(\xi \phi ^2 R\). The seemingly unnatural ratio of parameters, \(\lambda /\xi ^2 \sim 10^{-10}\) of the self quartic coupling of the inflaton, \(\lambda \), and the non-minimal coupling, \(\xi \), is understood by exponential suppression of \(\lambda \)...

We investigate the sensitivity of Higgs(-like) inflation to higher dimensional operators in the nonminimal couplings and in the potential, both in the metric and Palatini formalisms. We find that, while inflationary predictions are relatively stable against the higher dimensional operators around the attractor point in the metric formalism, they ar...

A long standing problem in kinematics at the hadron colliders is to determine the mass of invisible particles. This issue is particularly important for the signals of dark matter, which becomes one of the prominent targets of future collider experiments. In this paper, we show that the additional information from the precise timing measurement, whi...

A new setup of cosmic inflation with a periodic inflaton potential and conformal factor is discussed in the metric and Palatini formulations of gravity. As a concrete example, we focus on a natural-inflation-like inflaton potential, and show that the inflationary predictions fall into the allowed region of cosmic microwave background observations i...

It has been argued that the mixed Higgs-R ² model acts as the UV extension of the Higgs inflation, pushing up its cut-off scale in the vacuum close up to the Planck scale. In this letter, we study the inflaton oscillation stage after inflation, focusing on the effective mass of the phase direction of the Higgs field, which can cause a violent prehe...

A new setup of cosmic inflation with a periodic inflaton potential and conformal factor is discussed in the metric and Palatini formulations of gravity. As a concrete example, we focus on a natural-inflation-like inflaton potential, and show that the inflationary predictions fall into the allowed region of cosmic microwave background observations i...

We propose new mechanisms for small neutrino masses based on clockwork mechanism. The Standard Model neutrinos and lepton number violating operators communicate through the zero mode of clockwork gears, one of the two couplings of the zero mode is exponentially suppressed by clockwork mechanism. Including all known examples for the clockwork realiz...

In models with universal extra dimensions (UED), the lightest Kaluza-Klein excitation of neutral electroweak gauge bosons is a stable, weakly interacting massive particle and thus is a candidate for dark matter thanks to Kaluza-Klein parity. We examine concrete model realizations of such dark matter in the context of non-minimal UED extensions. The...

In models with universal extra dimensions (UED), the lightest Kaluza-Klein excitation of neutral electroweak gauge bosons is a stable, weakly interacting massive particle and thus is a candidate for dark matter thanks to Kaluza-Klein parity. We examine concrete model realizations of such dark matter in the context of non-minimal UED extensions. The...

We study a class of models in which the Higgs pair production is enhanced at hadron colliders by an extra neutral scalar. The scalar particle is produced by the gluon fusion via a loop of new colored particles, and decays into di-Higgs through its mixing with the Standard Model Higgs. Such a colored particle can be the top/bottom partner, such as i...

We study a class of models in which the Higgs pair production is enhanced at hadron colliders by an extra neutral scalar. The scalar particle is produced by the gluon fusion via a loop of new colored particles, and decays into di-Higgs through its mixing with the Standard Model Higgs. Such a colored particle can be the top/bottom partner, such as i...

We study the jet activity that accompanies the production by gluon fusion of a new physics scalar particle decaying into photons at the LHC. In the considered scenarios, both the production and decay mechanisms are governed by loop-induced interactions involving a heavy colored state. We show that the presence of large new physics contributions to...

We investigate a possibility for explaining the recently announced 750 GeV diphoton excess by the ATLAS and the CMS experiments at the CERN LHC in a model with multiple doubly-charged particles, which was originally suggested for explaining tiny neutrino masses through a three-loop effect in a natural way. The enhanced radiatively generated effecti...

Motivated by the recently reported diphoton resonance at 750 GeV, we study a new axion-like bosonic portal model of dark matter physics. When the resonance particle is identified as the pseudo-scalar mediator, via which the standard model sector would interact with the dark matter sector, the data from collider physics would provide profound implic...

We study the search of new charged gauge boson W′ in the split universal extra dimension model by considering pp → W′ → lve with √s = 14 TeV at the Large Hadron Collider. The interference between the W′ and the W boson of the Standard Model can be used to probe W′ from the distribution shape of the transverse mass between the lepton and the neutrin...

We study the collider implication of a neutral resonance which decays to several diboson final states such as $W^+W^-$, $ZZ$, and $Z\gamma$ via a minimal set of effective operators. We consider both CP-even and CP-odd bosonic states with spin 0, 1, or 2. The production cross sections for the bosonic resonance states are obtained with the effective...

The recently observed excess in gamma-ray signal near the Galactic center suggests that dark matter particles may annihilate into charged fermions that produce gamma-ray to be observed. In this paper, we consider a leptonic dark matter, which annihilates into the standard model leptons, $\mu^+ \mu^-$ and $\tau^+ \tau^-$, by the interaction of the g...

We investigate the collider phenomenology of a color-singlet vector resonance, which couples to the heaviest quarks, the top quarks, but very weakly to the rest of the fermions in the Standard Model. We find that the dominant production of such a resonance does not appear at the tree level -- it rather occurs at the one-loop level in association wi...

Superheavy dark matter can satisfy the observed dark matter abundance if the stability condition is fulfilled. Here, we propose a new Abelian gauge symmetry ${\rm U(1)}_H$ for the stability of superheavy dark matter as the electromagnetic gauge symmetry to the electron. The new gauge boson associated with ${\rm U(1)}_H$ contributes to the effective...

The recently reported X-ray line signal at \(E_\gamma \simeq 3.5~\mathrm{keV}\) from a stacked spectrum of various galaxy clusters and the Andromeda galaxy may be originating from a decaying dark matter particle of the mass \(2 E_\gamma \). A light axion-like scalar is suggested as a natural candidate for dark matter and its production mechanisms a...

Superheavy dark matter may show its presence in high energy neutrino signals detected on earth. From the latest results of IceCube, we could set the strongest lower bound on the lifetime of dark matter beyond 100 TeV around $10^{28} {\rm sec}$. The excess around a PeV is noticed and may be interpreted as the first signal of DM even though further c...

The observed Higgs mass $M_H=125.9\pm0.4$GeV leads to the criticality of the Standard Model, that is, the Higgs potential becomes flat around the scale $10^{17\text{--}18}$GeV for the top mass $171.3$GeV. Earlier we have proposed a Higgs inflation scenario in which this criticality plays a crucial role. In this paper, we investigate detailed cosmol...

Considering a third-generation squark as the lightest supersymmetric particle (LSP), we investigate R-parity violating collider signatures with bilinear LH or trilinear LQD operators that may contribute to observed neutrino masses and mixings. Reinterpreting the LHC 7+8 TeV results of SUSY and leptoquark searches, we find that third-generation squa...

We report on the current status of non-minimal universal extra dimension (UED) models. Our emphasis is on the possible extension of the minimal UED model by allowing bulk masses and boundary localized terms. We take into account the data from the Large Hadron Collider as well as direct and indirect searches of dark matter and electroweak precision...

Motivated by the recent 'Higgs-inflation' scenario based on a single inflaton field, we consider more generic two-field inflation with non-minimal (NM) coupling term. The generic analytic expressions are derived for cosmological observables with the product-separable as well as additive-separable potentials when the NM coupling term is dominated by...

The observed value of the Higgs boson mass indicates that the Higgs potential becomes small and flat at the scale around ${10}^{17}\text{ }\text{ }\mathrm{GeV}$. Having this fact in mind, we reconsider the Higgs inflation scenario proposed by Bezrukov and Shaposhnikov. It turns out that the nonminimal coupling $$\xi${}$ of the Higgs squared to the...

Recently a weak X-ray emission around E-gamma similar or equal to 3.5 keV was detected in the Andromeda galaxy and various galaxy clusters including the Perseus galaxy cluster but its source has been unidentified. Axino, the superpartner of axion, with a mass 2E(gamma) is suggested as a possible origin of the line with R-parity violating decay into...

The recently reported X-ray line signal at $E_\gamma \simeq 3.5 {\rm keV}$ from a stacked spectrum of various galaxy clusters and Andromeda galaxy may be originated from a decaying dark matter particle of the mass $2 E_\gamma$. A light axion-like scalar is suggested as a natural candidate for dark matter and its production mechanisms are closely ex...

Updated LHC data on the new 126 GeV boson during the 7 and 8 TeV runnings strengthen the standard model Higgs boson interpretation further. Through global χ 2 fit analysis, we investigate whether the new particle could be one of the scalar particles in two Higgs doublet models. Four types of the model (I, II, X and Y) are comprehensively studied. C...

Discovery of a Higgs boson and precise measurements of its properties open a new window to test physics beyond the standard model. Models with Universal Extra Dimensions are not exception. Kaluza-Klein excitations of the standard model particles contribute to the production and decay of the Higgs boson. In particular, the parameters associated with...

As the electromagnetic gauge symmetry makes the electron stable, a new abelian gauge symmetry may be responsible for the stability of superheavy dark matter. The gauge boson associated with the new gauge symmetry naturally plays the role of dark radiation and contributes to the effective number of `neutrino species', which has been recently measure...

We present a generalized universal extra dimensional model with KK-parity in the presence of the fermion-bulk masses and boundary-localized kinetic terms, which are generally allowed by symmetries of five dimensional gauge theory.

We present a general model with universal extra dimensions in the presence of the bulk fermion masses and boundary localized kinetic terms, which are generically allowed by symmetries of five dimensional gauge theory. We provide a comprehensive analysis for a general UED model, including Kaluza-Klein mass spectra, their interactions with the SM par...

We study the signature of dilepton and a hard jet ($\ell^+\ell^-j$) via heavy new gauge boson production in split universal extra dimension scenario where the Kaluza-Klein parity is conserved but the Kaluza-Klein number is not. A hard cut to the jet energy effectively removes virtually all possible backgrounds and provides a handle to search of new...

We consider a model of inflation with non-minimal coupling with two inflaton fields. It is noticed that a large class of inflaton potentials in product form as well as additively separable form can generate large non-Gaussianities especially when non-minimal coupling term is introduced. A potentially realistic hybrid inflationary model with a poten...

Physics in curved spacetime describes a multitude of phenomena, ranging from astrophysics to high energy physics. The last few years have witnessed further progress on several fronts, including the accurate numerical evolution of the gravitational field equations, which now allows highly nonlinear phenomena to be tamed. Numerical relativity simulat...

A new boson of mass roughly 125 GeV has been recently reported by the ATLAS and CMS collaborations. Although its signals in various decay modes resemble those of the standard model (SM) Higgs boson, observed are the combinations of entangled information about the production, decay rates and total decay width of the new boson. In addition, some deca...

In light of the recent observation of the Fermi-LAT 130 GeV gamma-ray line, we suggest a model of scalar dark matter in hidden sector, which can decay into two (hidden) photons. The process is radiatively induced by a GUT scale fermion in the loop, which is charged under a hidden sector U(1), and the kinetic mixing ($\sim \epsilon F^{\mu\nu}F'_{\mu...

In models with extra dimensions, vectorlike Dirac masses for fermion fields are generically allowed. These masses are independent of electroweak symmetry breaking and do not contribute to the known masses for the quarks and leptons. They control the profile of the bulk wave functions, the mass spectra of Kaluza-Klein modes, and interactions that co...

In low-scale gravity models, a particle collider with trans-Planckian collision energies can be an ideal place for producing black holes because a large amount of energy can be concentrated at the collision point, which can ultimately lead to black hole formation. In this article, the theoretical foundation for microscopic higher dimensional black...

We propose a scenario of cosmological inflation, called "hyperbolic inflation", based on compact hyperbolic extra dimensions and a non-minimal coupling term (ξϕ2 R) with a simple inflaton potential (λϕ4) in Ref. 1. The non-minimal coupling term ensures the presence of the slow-roll inflation potential and the large compact hyperbolic extra dimensio...

We study the new heavy charged gauge boson W' in various models including Left-Right symmetric, Little Higgs, Randall-Sundrum and universal extra dimension model considering pp \rightarrow W' \rightarrow lepton + neutrino with the 7 TeV and 14 TeV CM energies at the LHC. Of particular, we show that the universal extra dimension model is highly cons...

Recently the CMS collaboration at the LHC reported "the first direct limit on black hole production at a particle accelerator" using a data sample corresponding to an integrated luminosity of 35/pb of pp-collision at a center of mass energy of 7 TeV. Even though the result has a strong impact on future searches, the interpretation lacks enough theo...

Motivated by the recent MINOS observation, , we study CPT violation in neutrino sector caused by ghost condensation. As a concrete model, we consider an extra dimension model with two branes, which are spatially separated and communicate only through singlet ‘messenger’ fermion fields which contain right-handed neutrinos in the bulk. Assuming ghost...

We study a mechanism where tiny neutrino masses arise only from radiative contribution in a supersymmetric model. In each generation, the tree-level light neutrino mass is rotated away by introducing a second SM singlet $s_{L}$ that forms a Dirac mass term with the right-handed neutrino $n_{R}$. Even with non-zero Majorana neutrino mass for the rig...

We propose a natural scenario for the cosmological inflation with the non-minimal coupling term invoking compact hyperbolic extra dimensions. Thanks to the unique mathematical properties of compact hyperbolic space, the large volume of extra dimensions, which provides a natural understanding of the proper size of couplings, does not necessarily acc...

We consider CPT violation in neutrino sector, which is induced by ghost condensation. A model with extra dimension is suggested where ghost condensation occurs at a distant location separated from the SM brane. Right handed neutrinos in the bulk, which are originally introduced to explain small Yukawa couplings, play the role of messenger fields co...

We propose a gauged $U(1)_{H}$ horizontal symmetry around TeV scale that is a subgroup of a $SU(3)_{H}$ horizontal gauge symmetry broken at ${\cal O}(10^{14}) \GeV$. The breaking generates right-handed Majorana neutrino masses through a $SU(3)_H$ sextet scalar. A particular Majorana right-handed neutrino mass matrix explicitly determines the remnan...

5D UED is not automatically minimally flavor violating. This is due to flavor asymmetric counter-terms required on the branes. Additionally, there are likely to be higher dimensional operators which directly contribute to flavor observables. We document a mostly unsuccessful attempt at utilizing localization in a flat extra dimension to resolve the...

We study M-theory solutions involving compact hyperbolic spaces. The combination of a gap à la Randall-Sundrum and the topology of an internal Riemann surface allows a geometrical solution to the hierarchy problem that does not require light Kaluza-Klein modes. We comment on the consequences of such a compactification for lhc physics. KeywordsStri...

Split-UED allows for the possibility that the lowest lying KK excitations of the Standard Model fermions can be much lighter than the corresponding gauge or Higgs KK states. This can happen provided the fermion bulk masses are chosen to be large, in units of the inverse compactification radius, 1/R, and negative. In this setup, all of the other KK...