arXiv subjects

Lu-Xin Liu

Publications and source records attributed to Lu-Xin Liu.

16 recordsLinked to original sources

arXiv2013

Renormalisation running of masses and mixings in UED models

We review the Universal Extra-Dimensional Model compactified on a S1/Z2 orbifold, and the renormalisation group evolution of quark and lepton masses, mixing angles and phases both in the UED extension of the Standard Model and of the Minimal Supersymmetric Standard Model. We consider two typical scenarios: all matter fields propagating in the bulk, and matter fields constrained to the brane. The resulting renormalisation group evolution equations in these scenarios are compared with the existing results in the literature, together with their implications.

hep-ph↗

arXiv2012

Improved vacuum stability in a five dimensional model

In this paper we study the renormalization effects of the quark flavor mixings and the Higgs self- coupling in a five dimensional model where the boson fields are propagating in the bulk whilst the matter fields are localized to the brane. We first explore the evolution behaviors for the Cabibbo- Kobayashi-Maskawa matrix in this scenario. Then, in light of the recent LHC bounds on the Higgs mass, we find that the Higgs self-coupling evolution has an improved vacuum stability condition, which is in contrast with that of Standard Model and the Universal Extra Dimension scenario, where the theory has a much lower ultraviolet cut-off.

hep-ph↗

arXiv2012

Inhomogeneous longitudinal electric field-induced anomalous Hall conductivity in a ferromagnetic two-dimensional electron gas

It is known that the anomalous Hall conductivity (AHC) in a disordered two dimensional electron system with Rashba spin-orbit interaction and finite ferromagnetic spin-exchange energy is zero in the metallic weak-scattering regime because of the exact cancellation of the bare-bubble contribution by the vertex correction. We study the effect of inhomogeneous longitudinal electric field on the AHC in such a system. We predict that AHC increases from zero (at zero wavenumber), forms a peak, and then decreases as the wavenumber for the variation of electric field increases. The peak-value of AHC is as high as the bare-buble contribution. We find that the wave number, q, at which the peaks occur is the inverse of the geometric mean of the mean free path of an electron and the spin-exchange length scale. Although the Rashba energy is responsible for the peak-value of AHC, the peak position is independent of it.

cond-mat.mes-hall↗

arXiv2012

Spontaneous Broken Local Conformal Symmetry and Dark Energy Candidate

The local conformal symmetry is spontaneously broken down to the Local Lorentz invariance symmetry through the approach of nonlinear realization. The resulting effective Lagrangian, in the unitary gauge, describes a cosmological vector field non-minimally coupling to the gravitational field. As a result of the Higgs mechanism, the vector field absorbs the dilaton and becomes massive, but with an independent energy scale. The Proca type vector field can be modelled as dark energy candidate. The possibility that it further triggers Lorentz symmetry violation is also pointed out.

hep-ph↗

arXiv2012

Scaling of the CKM Matrix in the 5D MSSM

We discuss a five-dimensional Minimal Supersymmetric Standard Model compactified on a $S^1/Z_2$ orbifold, looking at, in particular, the one-loop evolution equations of the Yukawa couplings for the quark sector and various flavor observables. Different possibilities for the matter fields are discussed, that is, where they are in the bulk or localised to the brane. The two possibilities give rise to quite different behaviours. By studying the implications of the evolution with the renormalisation group of the Yukawa couplings and of the flavor observables we find that, for a theory that is valid up to the unification scale, the case where fields are localised to the brane, with a large $\tanβ$, would be more easily distinguishable from other scenarios.

hep-ph↗

arXiv2011

Dynamics of Weyl Scale Invariant non-BPS p=3 Branes

In this paper a Weyl scale invariant $p=3$ brane scenario is introduced, with the brane embedded in a higher dimensional bulk space with $N=1, 5D$ Super--Weyl symmetry. Its action, which describes its long wave oscillation modes into the ambient superspace and breaks the target symmetry down to the lower dimensional Weyl W(1,3) symmetry, is constructed by the approach of coset method.

hep-th↗

arXiv2011

Scaling of the Higgs Self-coupling and bounds on the Extra Dimension

In this paper we study the one-loop evolution equation of the Higgs quartic coupling $λ$ in the minimal Universal Extra Dimension model, and find that there are certain bounds on the extra dimension due to the singularity and vacuum stability conditions of the Higgs sector. In the range $250GeV \sim {R^{- 1}} \sim 80TeV$ of the compactification radius, we notice that for a given initial value $λ({M_Z})$, there is an upper limit on ${R^{- 1}}$ for a Higgs mass of $183GeV \sim {m_H}({M_Z}) \sim 187GeV$; where any other compactification scales beyond that have been ruled out for theories where the evolution of $λ$ does not develop a Landau pole and become divergent in the whole range (that is, from the electroweak scale to the unification scale). Likewise, in the range of the Higgs mass $152GeV \sim {m_H}({M_Z}) \sim 157GeV$, for an initial value $λ({M_Z})$, we are led to a lower limit on ${R^{- 1}}$; any other compactification scales below that will be ruled out for theories where the evolution of $λ$ does not become negative and destabilize the vacuum between the electroweak scale and the unification scale. For a Higgs mass in the range $157GeV < {m_H}({M_Z}) < 183GeV$, the evolution of $λ$ is finite and the theory is valid in the whole range (from the electroweak scale to the unification scale) for $250GeV \sim {R^{- 1}} \sim 80TeV$.

hep-ph↗

arXiv2011

Scaling of Yukawa Couplings and Quark Flavor Mixings in the UED Model

The evolution properties of Yukawa couplings and quark mixings are performed for the one-loop renormalization group equations in the Universal Extra Dimension (UED) model. It is found that the UED model has a substantial effect on the scaling of the fermion masses, including both quark and lepton sectors, whilst the radiative effects on the unitarity triangle is not a sensitive test in this model. Also, for this model, the renormalization invariants $R_{13}$ and $R_{23}$ describe the correlation between the mixing angles and mass ratios to a good approximation, with a variation of the order of $λ^4$ and $λ^5$ under energy scaling respectively.

hep-ph↗

arXiv2011

Evolution of the CKM Matrix in the Universal Extra Dimension Model

The evolution of the Cabibbo-Kobayashi-Maskawa matrix and the quark Yukawa couplings is performed for the one-loop renormalization group equations in the universal extra dimension model. It is found that the evolution of mixing angles and the CP violation measure J may rapidly vary in the presence of the Kaluza-Klein modes, and this variation becomes dramatic as the energy approaches the unification scale.

hep-ph↗

arXiv2010

Renormalization Invariants and Quark Flavor Mixings

A set of renormalization invariants is constructed using approximate, two-flavor, analytic solutions for RGEs. These invariants exhibit explicitly the correlation between quark flavor mixings and mass ratios in the context of the SM, DHM and MSSM of electroweak interaction. The well known empirical relations $θ_{23}\propto m_s /m_b $, $θ_{13}\propto m_d /m_b$ can thus be understood as the result of renormalization evolution toward the infrared point. The validity of this approximation is evaluated by comparing the numerical solutions with the analytical approach. It is found that the scale dependence of these quantities for general three flavoring mixing follows closely these invariants up to the GUT scale.

hep-ph↗

arXiv2010

Neutrino mixing in matter

Three-neutrino mixing in matter is studied through a set of evolution equations which are based on a rephasing invariant parametrization. Making use of the known properties of measured neutrino parameters, analytic, approximate, solutions are obtained. Their accuracy is confirmed by comparison with numerical integration of these equations. The results, when expressed in the elements squared of the mixing matrix, exhibit striking patterns as the matter density varies.

hep-ph↗

arXiv2009

Non-Abelian Vortex-String Dynamics from Nonlinear Realization

The dynamics of the non-Abelian vortex-string, which describes its low energy oscillations into the target $D=3+1$ spacetime as well as its orientations in the internal space, is derived by the approach of nonlinear realization. The resulting action correlating these two sectors is found to have an invariant synthesis form of the Nambu-Goto-${\bf C}P^{N-1}$ model actions. Higher order corrections to the vortex actions are presented up to the order of quartic derivatives. General $p$-brane dynamics in terms of the internal symmetry breaking is also discussed.

hep-th↗

arXiv2008

String Dynamics, Spontaneous Breaking of Supersymmetry and Dual Scalar Field Theory

The dynamics of a vortex string, which describes the Nambu-Goldtone modes of the spontaneous breakdown of the target space D=4, N=1 supersymmetry and internal $U(1)_R$ symmetry to the world sheet ISO(1,1) symmetry, is constructed by using the approach of nonlinear realization. The resulting action describing the low energy oscillations of the string into the covolume (super)space is found to have an invariant synthesis form of the Akulov-Volkov and Nambu-Goto actions. Its dual scalar field action is obtained by means of introducing two vectorial Lagrangian multipliers into the action of the string

hep-th↗

arXiv2008

Nonlinear Realization of N=2 Superconformal Symmetry and Brane Effective Actions

Due to the incompatibility of the nonlinear realization of superconformal symmetry and dilatation symmetry with the dilaton as the compensator field, in the present paper it shows an alternative mechanism of spontaneous breaking the N=2 superconformal symmetry to the N=0 case. By using the approach of nonlinear transformations it is found that it leads to a space-filling brane theory with Weyl scale W(1,3) symmetry. The dynamics of the resulting Weyl scale invariant brane, along with that of other Nambu-Goldstone fields, is derived in terms of the building blocks of the vierbein and the covariant derivative from the Maurer-Cartan oneforms. A general coupling of the matter fields localized on the brane world volume to these NG fields is also constructed.

hep-th↗

arXiv2006

Nonlinear Realization and Weyl Scale Invariant p=2 Brane

The action of Weyl scale invariant p=2 brane which breaks the target super Weyl scale symmetry in the N=1, D=4 superspace down to the lower dimensional Weyl symmetry W(1,2) is derived by the approach of nonlinear realization. The dual form action for the Weyl scale invariant supersymmetric D2 brane is also constructed. The interactions of localized matter fields on the brane with the Nambu-Goldstone fields associated with the breaking of the symmetries in the superspace and one spatial translation directions are obtained through the Cartan one-forms of the Coset structures. The covariant derivatives for the localized matter fields are also obtained by introducing Weyl gauge field as the compensating field corresponding to the local scale transformation on the brane world volume.

hep-th↗

arXiv2005

Rephasing Invariance and Hierarchy of the CKM Matrix

We identified a set of four rephasing invariant parameters of the CKM matrix. They are found to exhibit hierarchies in powers of $λ^2$, from $λ^2$ to $λ^8$. It is shown that, at the present level of accuracy, only the first three parameters are needed to fit all available data on flavor physics.

hep-ph↗