Chiral phase transition and meson spectrum in improved soft-wall AdS/QCD

We investigate in detail the chiral thermal transition of QCD in an improved soft-wall AdS/QCD model with a simply modified 5D conformal mass of the bulk scalar field. We also present a calculation in this model for the light meson spectra and other low-energy characteristic quantities including the pion form factor, the pi-rho coupling constant and the decay constants of pi, rho, a_1, which are shown to result in a good agreement with experimental data except for the pion decay constant. The thermal behavior of chiral condensate is studied. It is found that such a simply improved soft-wall model incorporates the crossover behavior of chiral thermal transition indicated by lattice simulations. The expected chiral transition temperature can be obtained

Infrared-Improved Soft-wall AdS/QCD Model for Mesons

We construct and investigate an infrared-improved soft-wall AdS/QCD model for mesons. Both linear confinement and chiral symmetry breaking of low energy QCD are well characterized in such an infrared-improved soft-wall AdS/QCD model. The model enables us to obtain a more consistent numerical prediction for the mass spectra of resonance scalar, pseudoscalar, vector and axial-vector mesons. In particular, the predicted mass for the lightest ground state scalar meson shows a good agreement with the experimental data. The model also provides a remarkable check for the Gell-Mann-Oakes-Renner relation and a sensible result for the space-like pion form factor.Comment: 15 pages, 4 figures, 7 tables, published versio

IR-improved Soft-wall AdS/QCD Model for Baryons

We construct an infrared-improved soft-wall AdS/QCD model for baryons by considering the infrared-modified 5D conformal mass and Yukawa coupling of the bulk baryon field. The model is also built by taking into account the parity-doublet pattern for the excited baryons. When taking the bulk vacuum structure of the meson field to be the one obtained consistently in the infrared-improved soft-wall AdS/QCD model for mesons, we arrive at a consistent prediction for the baryon mass spectrum in even and odd parity. The prediction shows a remarkable agreement with the experimental data. We also perform a calculation for the $\rho(a_1)$ meson-nucleon coupling constant and obtain a consistent result in comparison with the experimental data and many other models.Comment: 12 pages, 4 tables, 1 figure, to be published in PL

Synthesizing Bismuth Telluride Nanowires in a Large Scale and Investigating the Energy Filtering Effect by Blending Bismuth Telluride Nanowires and Silver Nanoparticle in Thermoelectrics

More than 50% of the energy sources becomes “waste” energy generally dissipated to the atmosphere in the form of heat. Thermoelectric effect is a conversion of temperature difference to electric voltage and can be used to convert the wasted heat to useful work. Nanomaterials have great potentials in the field of thermoelectric effect since they have properties that can allow higher efficiency in converting this wasted heat to electricity as compared to bulk materials. The purpose of this project is to develop a method to synthesize bismuth telluride (Bi2Te3) nanowires on a large scale and incorporate nanoinclusions on the produced nanowires. The method used to synthesis of nanomaterials in the lab will hopefully lead to their actual production on an industrial scale for thermoelectric application. Firstly, nanowires are produced using a large reactor. Afterwards, silver nanoparticles are going to be synthesized and mixed with the produced Bi2Te3 nanowires. Each mixture will then be hot pressed into a small disc before we test it for the ZT value (figure of merit to assess the degree of thermoelectric effect). The experiments performed in a 1-liter batch type of reactor were successful in synthesizing Bi2Te3 nanowires in a larger scale as compared to a research lab scale. Furthermore, the research indicates that there is an improvement in ZT. These findings will eventually help in the design for mass production of nanomaterials and further fuel more investigations on the effect of nanoinclusion in nanotechnology to be one step closer to reducing the energy crisis