arXiv subjects

Mingxing Luo

Publications and source records attributed to Mingxing Luo.

At least 37 records · Page 2Linked to original sources

arXiv2010

The Goldstino Field in Linear and Nonlinear Realizations of Supersymmetry

A Goldstino field in the nonlinear realization of supersymmetry is constructed from an appropriate chiral super-multiplet of the linear theory, in general O'Raifeataigh-like models. The linear theories can thus be reformulated into their nonlinear versions, via the standard procedure. The Goldstino field disappears totally from the original Lagrangian in the process, but reemerges in the Jacobian of the transformation and covariant derivatives. Vertices with Goldstino fields carry at least one space-time derivative, as one would have expected.

hep-th↗

arXiv2010

Nonlinear Realization of Spontaneously Broken N=1 Supersymmetry Revisited

This paper revisits the nonlinear realization of spontaneously broken N=1 supersymmetry. It is shown that the constrained superfield formalism can be reinterpreted in the language of standard realization of nonlinear supersymmetry via a new and simpler route. Explicit formulas of actions are presented for general renormalizable theories with or without gauge interactions. The nonlinear Wess-Zumino gauge is discussed and relations are pointed out for different definitions of gauge fields. In addition, a general procedure is provided to deal with theories of arbitrary Kahler potentials.

hep-th↗

arXiv2009

Constrained Superfields and Standard Realization of Nonlinear Supersymmetry

A constrained superfield formalism has been proposed recently to analyze the low energy physics related to Goldstinos. We prove that this formalism can be reformulated in the language of standard realization of nonlinear supersymmetry. New relations have been uncovered in the standard realization of nonlinear supersymmetry.

hep-th↗

arXiv2009

Cross Section Evaluation by Spinor Integration I: The massless case in 4D

To get the total cross section of one interaction from its amplitude ${\cal M}$, one needs to integrate $|{\cal M}|^2$ over phase spaces of all out-going particles. Starting from this paper, we will propose a new method to perform such integrations, which is inspired by the reduced phase space integration of one-loop unitarity cut developed in the last few years. The new method reduces one constrained three-dimension momentum space integration to an one-dimensional integration, plus one possible Feynman parameter integration. There is no need to specify a reference framework in our calculation, since every step is manifestly Lorentz invariant by the new method. The current paper is the first paper of a series for the new method. Here we have exclusively focused on massless particles in 4D. There is no need to carve out a complicated integration region in the phase space for this particular simple case because the integration region is always simply $[0,1]$.

hep-ph↗

arXiv2009

Positive mass theorems for asymptotically de Sitter spacetimes

We use planar coordinates as well as hyperbolic coordinates to separate the de Sitter spacetime into two parts. These two ways of cutting the de Sitter give rise to two different spatial infinities. For spacetimes which are asymptotic to either half of the de Sitter spacetime, we are able to provide definitions of the total energy, the total linear momentum, the total angular momentum, respectively. And we prove two positive mass theorems, corresponding to these two sorts of spatial infinities, for spacelike hypersurfaces whose mean curvatures are bounded by certain constant from above.

math.DG↗

arXiv2009

Gauge Extensions of Supersymmetric Models and Hidden Valleys

Supersymmetric models with extended group structure beyond the standard model are revisited in the framework of general gauge mediation. Sum rules for sfermion masses are shown to depend genuinely on the group structure, which can serve as important probes for specific models. The left-right model and models with extra U(1) are worked out for illustrations. If the couplings of extra gauge groups are small, supersymmetric hidden valleys of the scale 10-100 GeV can be naturally constructed in companion of a TeV-scale supersymmetric visible sector.

hep-ph↗

arXiv2009

$R$-symmetric Gauge Mediation With Fayet-Iliopoulos Term

We have studied $R$-symmetrc gauge mediation models with Fayet-Iliopoulos terms. We give a concrete example of hidden sector with an $U(1)_H$ gauge theory and a Fayet-Iliopoulos term, which can induce distinctive soft terms in the visible sector, and help solving fine tuning problems in models of $R$-symmetric gauge mediation.

hep-ph↗

arXiv2008

Dielectron and Diphoton channels in 2HDM

It was observed recently by Randall and Wise that, any particle in the Standard Model cannot decay to $e^+e^-$ and $γγ$ final states with comparably measurable branching ratios. This is also true for most extensions of the Standard Model, with the Randall-Sundrum model as an outstanding exception. In this paper, we show that two-Higgs-Doublet-Models (2HDM) yield another possible exception if certain parameters are properly chosen. In addition, we have checked that this model survives the tests of low energy processes, including the anomalous magnetic moment and electric dipole moment of leptons, lepton-flavor-violating decays $μ^- \to e^- γ$ and $e^- e^+ e^-$.

hep-ph↗

arXiv2008

E2 Instanton Effects and Higgs Physics In Intersecting Brane Models

String instanton effects in Higgs physics are discussed through a type IIA model based on T^{6}/(Z^{2}\times Z^{'2}) orentifold compactifaction. By inclusion of rigid E2-branes, the model exhibits a MSSM-like spectrum, as well as extra mu and quartic Higgs couplings. These extra couplings are induced via E2 instantons non-perturbatively. Setting the string scale at 10^{18} GeV, one gets interesting TeV Higgs physics. In particlular, the tree-level Higgs mass can be uplifted substantially.

hep-th↗

arXiv2008

Some Phenomenologies of Unparticle Physics

Fermionic unparticles are introduced and their basic properties are discussed. Some phenomenologies related are exploited, such as their effects on charged Higgs boson decays and anomalous magnetic moments of leptons. Also, it has been found that measurements of $B^0-\bar B^0$ mixing could yield interesting constraints on couplings between unparticle operators and standard model fields.

hep-ph↗

arXiv2008

Unparticle Physics and A_{FB}^b on the Z pole

An attempt has been made to address the 3σanomaly of the forward-backward asymmetry of b quark in LEP data via an unparticle sector. For most part of the parameter space except certain particular regions, the anomaly could not be explained away plausibly, when constraints from other LEP observables are taken into account.

hep-ph↗

arXiv2007

Unitarity Constraints on effective interaction in $πN$ scattering

Positivity constraints are derived on pion-nucleon scattering amplitudes and their even-order derivatives inside the Mandelstam Triangle with the help of dispersion relations. Fairly interesting constraints are obtained on some of the low energy constants, by a combination of the chiral perturbation theory for heavy baryons and existing fitting results from available pion-nucleon phase shifts at intermediate energies.

hep-ph↗

arXiv2006

Black Holes in the Presence of Cosmological Constant and Large N Brane World

Analytic form has been obtained for four-dimensional black holes with a minimal Hawking temperature in a theory with cosmological constant, dilaton and gauge fields. In general dimensions, black hole solutions are shown to exist and their asymptotic behaviors are obtained. In theories of ten dimension, N coincident D3-branes as the boundary of an $AdS_5$ space are constructed by embedding black D3-branes, with a five-dimensional compactified space of negligible size if N is large, which provide natural realizations of the Randall-Sundrum scenario. For this $AdS_{5}$ background, the cosmological constant is a higher order perturbation and its effect on the spectra of standard model fields on the branes can be calculated.

hep-th↗

arXiv2005

Fitting Non-Minimally Coupled Scalar Models to Gold SnIa Dataset

Non-minimally coupled theories of special potentials are analyzed numerically. Such theories yield equations of state $ω<-1$ and oscillations of the cosmological expansion, which are favored by the recent analysis of observations. Fitting these theories to the Gold SnIa dataset, we obtain results comparable with other models. A potential of the form $V(ϕ)=V_0e^{a_1ϕ^2}$ yields $χ^2_{min}=170.127$. Similar results are obtained for potentials of the form $V(ϕ)=V_0+a_1ϕ^n$.

astro-ph↗

arXiv2005

Recursion Relations for Tree Amplitudes in Super Gauge Theories

Using newly proposed BCF/BCFW recursion relations, compact formulas are obtained for tree-level n-gluon amplitudes of helicity structure --++...+. We then make an extension of these recursion relations to include fermions of multi-flavors, from which MHV and \bar{MHV} amplitudes are reproduced. We also calculate non-MHV amplitudes of processes with two fermions and four gluons. Results thus obtained are equivalent to those obtained by extended CSW prescriptions, and those by conventional field theory calculations.

hep-th↗

arXiv2005

Compact Formulas for Tree Amplitudes of Six Partons

Compact results are obtained for tree-level non-MHV amplitudes of six fermions and of four fermions and two gluons, by using extended BCF/BCFW rules. Combining with previous results, complete set of tree amplitudes of six partons are now available in compact forms.

hep-th↗

arXiv2005

Systematics of One-Loop Scattering Amplitudes in N=4 Super Yang-Mills Theories

One-loop scattering amplitudes in N=4 super Yang-Mills (SYM) theories are analyzed in the paradigm of maximal helicity violating Feynman diagrams. There are very limited number of loop integrals to be evaluated. For a process with n external particles, there are only [n/2]-1 generically independent integrals. Furthermore, the relations between leading N_c amplitudes A_{n;1} and sub-leading amplitudes A_{n;c} are found to be identical to those obtained from conventional field theory calculations, which can be interpreted as an indirect support for the paradigm.

hep-th↗

arXiv2004

One-Loop Maximal Helicity Violating Amplitudes in N=4 Super Yang-Mills Theories

One-loop maximal helicity violating (MHV) amplitudes in N=4 super Yang-Mills (SYM) theories are analyzed, using the prescription of Cachazo, Svrcek, and Witten (CSW). The relations between leading N_c amplitudes A_{n;1} and sub-leading amplitudes A_{n;c} obtained by the CSW prescription are found to be identical to those obtained from conventional field theory calculations. Combining with existing results, this establishes the validity of the CSW prescription to one-loop in the calculation of MHV amplitudes in N=4 SYM theories of finite N_c.

hep-th↗