122316978
Low momentum scattering of the Dirac particlewith an asymmetric cusp potential
Abstract.We study the exact solutions of the bound and scattering states of the one-dimensional Dirac equation with an asymmetric cusp potential and derive the condition of the supercriticality for this quantum system. We find that the scattering properties are invariant under reflection of the potential's shape, and the supercritical value for the potential amplitude V0 varies with the degree of the potential asymmetry.
121809939
The Wigner solution of quark gap equation and chiral phase transition of QCD at finite temperature and nonzero chemical potential
By employing some modification to the normal NJL model, we discuss the Wigner solution of quark gap equation at finite temperature and chemical potential when the current quark mass m is nonzero. The discovery of the coexistence of the Nambu solution and the Wigner solution at finite temperature and chemical potential beyond the chiral limit is of great importance in the study of the chiral phase transition of QCD. Using the pressure difference between Nambu phase and Wigner phase (or in other words, the bag constant) as an order parameter for chiral phase transition, we draw a possible phase diagram based on our calculations.
53688784
Locate QCD critical end point in a continuum model study
A bstractWith a modified chemical potential dependent effective model for the gluon propagator, we try to locate the critical end point (CEP) of strongly interacting matter in the framework of Dyson-Schwinger equations (DSE). Beyond the chiral limit, we find that Nambu solution and Wigner solution could coexist in some area. Using the CornwallJackiw-Tomboulis (CJT) effective action, we show that these two phases are connected by a first order phase transition. We then locate CEP as the end point of the first order phase transition line. Meanwhile, based on CJT effective action, we give a direct calculation for the chiral susceptibility and thereby study the crossover.
121136055
The equation of state of QCD under hard-dense-loop approximation
Based on the method proposed by Zong et al., we calculate the equation of state (EOS) of QCD at zero temperature and finite quark chemical potential under the hard-dense-loop (HDL) approximation. A comparison between the EOS under HDL approximation and the cold, perturbative EOS of QCD proposed by Fraga, Pisarski and Schaffner-Bielich is made. It is found that when µ is less than 4.7 GeV, the pressure density calculated using HDL approximation is much larger than that calculated using perturbation theory. This enhancement of the obtained pressure density with respect to that of perturbation theory can be regarded as a possible explanation for the strong coupled QGP. It is also expected that the obtained EOS can be applied in the study of neutron stars.
120263943
Quark-meson vertices and pion properties at finite chemical potential
Based on the rainbow-ladder approximation of the Dyson-Schwinger equations and the assumption of the analyticity of the quark-meson vertex in the neighborhood of zero chemical potential ({mu}=0) and neglecting the {mu}-dependence of the dressed gluon propagator, we use the method of studying the dressed quark propagator at finite chemical potential given in [H. S. Zong, L. Chang, F.Y. Hou, W. M. Sun, and Y. X. Liu, Phys. Rev. C 71, 015205 (2005)] to show that the axial-vector quark-meson vertex at finite {mu} can be obtained from the corresponding one at {mu}=0 by a shift of variable: {gamma}{sub 5{nu}}{sup j}[{mu}](k, p)={gamma}{sub 5{nu}}{sup j}(k{approx}, p), where k and p are the relative and total momentum of the quark-antiquark pair, respectively, and k{approx}=(k-vector, k{sub 4}+i{mu}). Similar relations hold for any other type of quark-meson vertex. This feature would facilitate the numerical calculations of the quark-meson vertex function at finite {mu} considerably. Based on these results and using the dressed quark propagator at {mu}=0 proposed in [R. Alkofer, W. Detmold, C. S. Fischer, and P. Maris, Phys. Rev. D 70, 014014 (2004)], we calculate the pion decay constant f{sub {pi}} and the pion mass m{sub {pi}} at finite {mu} and a comparison of ourmore » results with those in the literature is made.« less
124327174
The Renormalized Equation of State and Quark Star
By means of the EOS of QCD at zero temperature and finite quark chemical potential we proposed [Phys. Rev. D 78(2008)054001] in the framework of rainbow-ladder approximation of Dyson-Schwinger approach, we investigate the structure of quark star and its property. It is found that the mass-radius relation in our model is very different from that of usual quark star models, but similar to neutron star models. The obtained mass of quark star is about 1.75M⊙ ~ 2.2M⊙. The obtained radius of quark star is 22 ~ 26 km, which is obviously larger than the results in other models. The reason for this discrepancy is analyzed.
118672738
From spin vertex to string vertex
A bstractIn the recent publication [1] the spin vertex was introduced as a new approach for computing three-point functions in N=4$$ \mathcal{N}=4 $$ SYM. In this note we consider the BMN limit of the spin vertex for scalar excitations and show that it reproduces the string vertex in the light-cone string field theory which describes the string interactions in the pp-wave background at the leading order of λ′ expansion. This is achieved by introducing a polynomial representation for the spin vertex. We derive the Neumann coefficients from the spin vertex at weak coupling and show they match with the Neumann coefficients from the string field theory.
119738846
Two-beam detuned-cavity electron accelerator structure
Progress has been made in the theory, development, cavity design and optimization, beam dynamics study, beam transport design, and hardware construction for studies of a detuned two-beam electron accelerator structure.
118329440
Virtual signed Euler characteristics
Roughly speaking, to any space $M$ with perfect obstruction theory we associate a space $N$ with symmetric perfect obstruction theory. It is a cone over $M$ given by the dual of the obstruction sheaf of $M$, and contains $M$ as its zero section. It is locally the critical locus of a function. 
More precisely, in the language of derived algebraic geometry, to any quasi-smooth space $M$ we associate its $(-1)$-shifted cotangent bundle $N$. 
By localising from $N$ to its $\mathbb C^*$-fixed locus $M$ this gives five notions of virtual signed Euler characteristic of $M$: 
(1) The Ciocan-Fontanine-Kapranov/Fantechi-G\"ottsche signed virtual Euler characteristic of $M$ defined using its own obstruction theory, 
(2) Graber-Pandharipande's virtual Atiyah-Bott localisation of the virtual cycle of $N$ to $M$, 
(3) Behrend's Kai-weighted Euler characteristic localisation of the virtual cycle of $N$ to $M$, 
(4) Kiem-Li's cosection localisation of the virtual cycle of $N$ to $M$, 
(5) $(-1)^{vd}$ times by the topological Euler characteristic of $M$. 
Our main result is that (1)=(2) and (3)=(4)=(5). The first two are deformation invariant while the last three are not.
117931252
The Properties of $D^{*}_{s1}(2700)^{+}$
The new particle $D^{*}_{s1}(2700)^{+}$ has stimulated many attentions. There are different assignments of its inherent properties. It may be a $2^3S_1$, $1^3D_1$ or the mixture of $2^3S_1-1^3D_1$ $c\bar s$ $1^-$ state. By considering its mass, decay modes, full width, production rate, and comparing with current experimental data, we point out that there is another more reasonable assignment: $D^{*}_{s1}(2700)^{+}$ could be identified as two resonances, one of which is a $2^3S_1$ state, another is a 1D state, and both are $c\bar s$ $1^-$ states. The two states have very close masses, which are around 2700 MeV, and both have broad decay widths. So in experiments, the overlapping of $DK$ or $D^*K$ invariant mass distribution coming from their decays is found, but the current experiments could not distinguish these two resonances and reported one particle.
119484972
Multi-harmonic test setup for RF breakdown studies
A multi-harmonic asymmetric cavity is predicted to obtain lower RF breakdown probability than a conventional pillbox cavity, when driven by two or more external RF harmonic sources. Experimental efforts are underway to study RF breakdown in a bimodal asymmetric cavity powered by dual frequency test stand. Details of design of the test stand are described.