Thermodynamics of lattice QCD with 2 flavours of colour-sextet quarks: A model of walking/conformal Technicolor

QCD with two flavours of massless colour-sextet quarks is considered as a model for conformal/walking Technicolor. If this theory possess an infrared fixed point, as indicated by 2-loop perturbation theory, it is a conformal(unparticle) field theory. If, on the other hand, a chiral condensate forms on the weak-coupling side of this would-be fixed point, the theory remains confining. The only difference between such a theory and regular QCD is that there is a range of momentum scales over which the coupling constant runs very slowly (walks). In this first analysis, we simulate the lattice version of QCD with two flavours of staggered quarks at finite temperatures on lattices of temporal extent $N_t=4$ and 6. The deconfinement and chiral-symmetry restoration couplings give us a measure of the scales associated with confinement and chiral-symmetry breaking. We find that, in contrast to what is seen with fundamental quarks, these transition couplings are very different. $\beta=6/g^2$ for each of these transitions increases significantly from $N_t=4$ and $N_t=6$ as expected for the finite temperature transitions of an asymptotically-free theory. This suggests a walking rather than a conformal behaviour, in contrast to what is observed with Wilson quarks. In contrast to what is found for fundamental quarks, the deconfined phase exhibits states in which the Polyakov loop is oriented in the directions of all three cube roots of unity. At very weak coupling the states with complex Polyakov loops undergo a transition to a state with a real, negative Polyakov loop.Comment: 21 pages, 9 figures, Revtex with postscript figures. One extra reference was added; text is unchanged. Corrected typographical erro

The analysis of barriers to bim implementation for industrialized building construction: a China study

The emerging Building Information Modeling (BIM) can better promote the development of building industrialization, with data integration between information-rich building models and business processes. However, the practical implementation of BIM still faces barriers. Existing studies have discussed these barriers extensively, but the research on the barriers to the implementation of BIM amid building industrialization in China is inadequate. In this study, 23 barriers were identified through literature review. A questionnaire survey approach was used to collect data from various parties. Factor analysis methods were used to process and rank barrier factors for BIM applications in the context of industrialized building. Based on the analysis of each factor, analytic hierarchy process was adopted to identify the key barriers to the implementation of BIM for industrialized building construction. The study concluded that the main barriers for BIM implementation for industrialized building were capital-related factors and the lack of support from owners. This study proposes that in addition to governmental policy support for BIM and multi-stakeholder engagement, companies should also organize experts to effectively evaluate the risks of applying BIM. Overall, this study provides suggestions on construction organizational transformations in the roadmap of moving towards digital-driven building industrialization

Thermodynamics of lattice QCD with 2 sextet quarks on N_t=8 lattices

We continue our lattice simulations of QCD with 2 flavours of colour-sextet quarks as a model for conformal or walking technicolor. A 2-loop perturbative calculation of the $\beta$-function which describes the evolution of this theory's running coupling constant predicts that it has a second zero at a finite coupling. This non-trivial zero would be an infrared stable fixed point, in which case the theory with massless quarks would be a conformal field theory. However, if the interaction between quarks and antiquarks becomes strong enough that a chiral condensate forms before this IR fixed point is reached, the theory is QCD-like with spontaneously broken chiral symmetry and confinement. However, the presence of the nearby IR fixed point means that there is a range of couplings for which the running coupling evolves very slowly, i.e. it 'walks'. We are simulating the lattice version of this theory with staggered quarks at finite temperature studying the changes in couplings at the deconfinement and chiral-symmetry restoring transitions as the temporal extent ($N_t$) of the lattice, measured in lattice units, is increased. Our earlier results on lattices with $N_t=4,6$ show both transitions move to weaker couplings as $N_t$ increases consistent with walking behaviour. In this paper we extend these calculations to $N_t=8$. Although both transition again move to weaker couplings the change in the coupling at the chiral transition from $N_t=6$ to $N_t=8$ is appreciably smaller than that from $N_t=4$ to $N_t=6$. This indicates that at $N_t=4,6$ we are seeing strong coupling effects and that we will need results from $N_t > 8$ to determine if the chiral-transition coupling approaches zero as $N_t \rightarrow \infty$, as needed for the theory to walk.Comment: 21 pages Latex(Revtex4) source with 4 postscript figures. v2: added 1 reference. V3: version accepted for publication, section 3 restructured and interpretation clarified. Section 4 future plans for zero temperature simulations clarifie

Asymptotic Formulas for the Zeros of the Meixner Polynomials

AbstractThe zeros of the Meixner polynomialmn(x;β,c) are real, distinct, and lie in (0,∞). Letαn,sdenote thesth zero ofmn(nα;β,c), counted from the right; and letαn,sdenote thesth zero ofmn(nα;β,c), counted from the left. For each fixeds, asymptotic formulas are obtained for bothαn,sandαn,s, asn→∞

Evidence for Antiferromagnetic Order in La2−x_{2-x}Cex_{x}CuO4_{4} from Angular Magnetoresistance Measurements

We investigated the in-plane angular magnetoresistivity (AMR) of $T^{^{\prime}}$-phase La$_{2-x}$Ce$_{x}$CuO$_{4}$ (LCCO) thin films ($x=0.06-0.15$) fabricated by a pulsed laser deposition technique. The in-plane AMR with $\mathbf{H}\parallel ab$ shows a twofold symmetry instead of the fourfold behavior found in other electron-doped cuprates such as Pr$_{2-x}$Ce$_{x}$CuO$_{4}$ and Nd$_{2-x}$Ce$_{x}$CuO$_{4}$. The twofold AMR disappears above a certain temperature, $T_{D}$. The $T_{D}(x)$ is well above $T_{c}(x)$ for $x=0.06$ ($\sim 110$ K), and decreases with increasing doping, until it is no longer observed above $T_{c}(x)$ at $x=0.15$. This twofold AMR below $T_{D}(x)$ is suggested to originate from an antiferromagnetic or spin density wave order.Comment: to be published in Phys. Rev. B, Vol. 80 (2009