arXiv subjects

Yu-Chieh Chung

Publications and source records attributed to Yu-Chieh Chung.

8 recordsLinked to original sources

arXiv2014

Topological Inflation with Large Tensor-to-scalar Ratio

BICEP2's detection on the primordial B-mode of CMB polarization suggests that inflation occurred around GUT scale, with the tensor-to-scalar ratio r~0.2. Inspired by this discosvery, we study the topological inflation which was driven by a double/single/no well potential. We show that with proper choice of parameters, all these three types of topological inflationary models could be consistent with the constraints from current observations.

astro-ph.CO↗

arXiv2011

On Global Flipped SU(5) GUTs in F-theory

We construct an SU(4) spectral divisor and its factorization of types (3,1) and (2,2) based on the construction proposed in [1]. We calculate the chiral spectra of flipped SU(5) GUTs by using the spectral divisor construction. The results agree with those from the analysis of semi-local spectral covers. Our computations provide an example for the validity of the spectral divisor construction and suggest that the standard heterotic formulae are applicable to the case of F-theory on an elliptically fibered Calabi-Yau fourfold with no heterotic dual.

hep-th↗

arXiv2011

On F-theory E_6 GUTs

We approach the Minimum Supersymmetric Standard Model (MSSM) from an E_6 GUT by using the spectral cover construction and non-abelian gauge fluxes in F-theory. We start with an E_6 singularity unfolded from an E_8 singularity and obtain E_6 GUTs by using an SU(3) spectral cover. By turning on SU(2) X U(1)^2 gauge fluxes, we obtain a rank 5 model with the gauge group SU(3) X SU(2) X U(1)^2. Based on the well-studied geometric backgrounds in the literature, we demonstrate several models and discuss their phenomenology.

hep-th↗

arXiv2011

Flipped SU(5) GUTs from E_8 Singularities in F-theory

In this paper we construct supersymmetric flipped SU(5) GUTs from E_8 singularities in F-theory. We start from an SO(10) singularity unfolded from an E_8 singularity by using an SU(4) spectral cover. To obtain realistic models, we consider (3,1) and (2,2) factorizations of the SU(4) cover. After turning on the massless U(1)_X gauge flux, we obtain the SU(5) X U(1)_X gauge group. Based on the well-studied geometric backgrounds in the literature, we demonstrate several models and discuss their phenomenology.

hep-th↗

arXiv2010

Abelian Gauge Fluxes and Local Models in F-Theory

We analyze the Abelian gauge fluxes in local F-theory models with G_S=SU(6) and SO(10). For the case of G_S=SO(10), there is a no-go theorem which states that for an exotic-free spectrum, there are no solutions for U(1)^2 gauge fluxes. We explicitly construct the U(1)^2 gauge fluxes with an exotic-free bulk spectrum for the case of G_S=SU(6). We also analyze the conditions for the curves supporting the given field content and discuss non-minimal spectra of the MSSM with doublet-triplet splitting.

hep-th↗

arXiv2009

A Note on Local GUT Models in F-Theory

We construct non-minimal GUT local models in the F-theory configuration. The gauge group on the bulk G_S is one rank higher than the GUT gauge group. The line bundles on the curves are non-trivial to break G_S down to the GUT gauge groups. We demonstrate examples of SU(5) GUT from G_S=SU(6) and G_S=SO(10), the flipped SU(5) from G_S=SO(10), and the SO(10) GUT from G_S=SO(12) and G_S=E_6. We obtain complete GUT matter spectra and couplings, with minimum exotic matter contents. GUT gauge group breaking to MSSM is achievable by instanton configurations.

hep-th↗

arXiv2009

Supersymmetry breaking, heterotic strings and fluxes

In this paper we consider compactifications of heterotic strings in the presence of background flux. The background metric is a T^2 fibration over a K3 base times four-dimensional Minkowski space. Depending on the choice of three-form flux different amounts of supersymmetry are preserved (N=2,1,0). For supersymmetric solutions unbroken space-time supersymmetry determines all background fields except one scalar function which is related to the dilaton. The heterotic Bianchi identity gives rise to a differential equation for the dilaton which we discuss in detail for solutions preserving an N=2 supersymmetry. In this case the differential equation is of Laplace type and as a result the solvability is guaranteed.

hep-th↗

arXiv2007

Metastable Flux Configurations and de Sitter Spaces

We derive stability conditions for the critical points of the no-scale scalar potential governing the dynamics of the complex structure moduli and the axio-dilaton in compactifications of type IIB string theory on Calabi-Yau three-folds. We discuss a concrete example of a T^6 orientifold. We then consider the four-dimensional theory obtained from compactifications of type IIB string theory on non-geometric backgrounds which are mirror to rigid Calabi-Yau manifolds and show that the complex structure moduli fields can be stabilized in terms of H_{RR} only, i.e. with no need of orientifold projection. The stabilization of all the fields at weak coupling, including the axio-dilaton, may require to break supersymmetry in the presence of H_{NS} flux or corrections to the scalar potential.

hep-th↗