Friedmann cosmology on codimension 2 brane with time dependent tension

A solution of codimension 2 brane is found for which 4 dimensional Friedmann cosmology is recovered on the brane with time dependent tension, in the Einstein frame. The effective parameter $p/\rho$ of equation of state on the brane can be quintessence like, de Sitter like or phantom like, depending on integration constants of the solution.Comment: 6 pages, 4 figure

Stable Fulde-Ferrell-Larkin-Ovchinnikov pairing states in 2D and 3D optical lattices

We present the study of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing states in the $p$-orbital bands in both two and three-dimensional optical lattices. Due to the quasi one-dimensional band structure which arises from the unidirectional hopping of the orthogonal $p$-orbitals, the pairing phase space is not affected by spin imbalance. Furthermore, interactions build up high dimensional phase coherence which stabilizes the FFLO states in 2D and 3D optical lattices in a large parameter regime in phase diagram. These FFLO phases are stable with imposing the inhomogeneous trapping potential. Their entropies are comparable to those of the normal states at finite temperatures.Comment: 5 page

Numerical Investigation on Flow Separation Control of Low Reynolds Number Sinusoidal Aerofoils

The paper presents a computational analysis of the characteristics of a NACA 634- 021 aerofoil incorporated with sinusoidal leading-edge protuberances at Re = 14,000. The protuberances are characterized by an amplitude and wavelength of 12% and 50% of the aerofoil chord length respectively. An unsteady Reynolds Average Navier Stokes (RANS) analysis of the full-span aerofoils was carried out using Transition SST (Shear Stress Transport) turbulence model across five different angles-of-attack (AOA). Comparisons with previous experimental results reported good qualitative agreements in terms of flow separation when the aerofoils are pitched at higher AOAs. Results presented here comprised of near-wall flow visualizations of the flow separation bubble at the peaks and troughs of the protuberances. Additionally, results indicate that the aerofoil with leading-edge protuberances displayed distinctive wall shear streamline and iso-contour characteristics at different span-wise positions. This implies that even at a low Reynolds number, implementations of these leading-edge protuberances could have positive or adverse effects on flow separation

Weak productions of new charmonium in semi-leptonic decays of B_c

We study the weak productions of novel heavy mesons, such as $\eta_c^{\prime}$, $h_c$, $h_c^{\prime}$, $\chi_{c0}^{\prime}$, X(3940), Y(3940), X(3872), and Y(4260), in the semi-leptonic $B_c$ decays. Since there is still no definite answer for the components of X(3940), Y(3940), X(3872), Y(4260) so far, we will assign them as excited charmonium states with the possible quantum numbers constrained by the current experiments. As for the weak transition form factors, we calculate them in the framework of light-cone QCD sum rules approach, which is proved to be a powerful tool to deal with the non-perturbative hadronic matrix element. Our results indicate that different interpretations of X(3940) can result in remarkable discrepancy of the production rate in the $B_c$ decays, which would help to clarify the inner structure of the X(3940) with the forthcoming LHC-b experiments. Besides, the predicted large weak production rates of X(3872) and Y(3940) in $B_c$ decays and the small semi-leptonic decay rate for $B_c \to Y(4260)$ all depend on their quantum number $J^{PC}$ assignments. Moreover, the $S-D$ mixing of various vector charmonium states in the weak decay of $B_c$ is also discussed in this work. The future experimental measurements of these decays will test the inner structures of these particles, according to our predictions here.Comment: 26 pages, with 7 figures, revTex

The double charm decays of BcB_c Meson in the Perturbative QCD Approach

We make a systematic investigation on the double charm decays of $B_c$ meson, by employing the perturbative QCD approach based on $k_T$ factorization. It is found that the non-factorizable emission diagrams are not negligible in these channels. We predict the branching ratios of these $B_c$ decays and also the transverse polarization fractions of $B_c\rightarrow D_{(s)}^{*+}\bar D^{*0}, D_{(s)}^{*+}D^{*0}$ decays, % where V denote the vector $D^*_{(s)}$ meson. We find that the magnitudes of the branching ratios of the decays $B_c\rightarrow D_s\bar{D}^0$ and $B_c\rightarrow D_sD^0$ are very close to each other, which are well suited to extract the Cabibbo-Kobayashi-Maskawa angle $\gamma$ through the amplitude relations. In addition, a large transverse polarization contribution that can reach $50$ is predicted in some of the $B_c$ meson decay to two vector charmed mesons.Comment: 22 pages, 5 tables, to appear at PRD. arXiv admin note: text overlap with arXiv:1112.125

Thermodynamic of the Ghost Dark Energy Universe

Recently, the vacuum energy of the QCD ghost in a time-dependent background is proposed as a kind of dark energy candidate to explain the acceleration of the Universe. In this model, the energy density of the dark energy is proportional to the Hubble parameter $H$, which is the Hawking temperature on the Hubble horizon of the Friedmann-Robertson-Walker (FRW) Universe. In this paper, we generalized this model and choice the Hawking temperature on the so-called trapping horizon, which will coincides with the Hubble temperature in the context of flat FRW Universe dominated by the dark energy component. We study the thermodynamics of Universe with this kind of dark energy and find that the entropy-area relation is modified, namely, there is an another new term besides the area term.Comment: 8 pages, no figure

Recommendatory system for supermarket online shopping

With the recent rise of online purchasing, many companies have focused on developing recommendation systems, where customers are suggested different options for complementing their purchases. This thesis will introduce and test four different approaches for a recommendation system for online shopping at supermarkets, based on the historical of previous customers. The four proposed algorithms are based on successful recommendation systems, which include a histogram-based approach, a graph theory-based approach, an embedding-based approach and finally a support-vector machine-based approach