4,539 research outputs found

    Finite-volume effects on octet-baryon masses in covariant baryon chiral perturbation theory

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    We study finite-volume effects on the masses of the ground-state octet baryons using covariant baryon chiral perturbation theory (ChPT) up to next-to-leading order by analyzing the latest nf=2+1n_f=2+1 lattice Quantum ChromoDynamics (LQCD) results from the NPLQCD collaboration. Contributions of virtual decuplet baryons are taken into account using the "consistent" coupling scheme. We compare our results with those obtained from heavy baryon ChPT and show that, although both approaches can describe well the lattice data, the underlying physics is different: In HBChPT, virtual decuplet baryons play a more important role than they do in covariant ChPT. This is because the virtual octet baryon contributions to finite-volume corrections are larger in covariant ChPT than in HBChPT, while the contributions of intermediate decuplet baryons are smaller, because of relativistic effects. We observe that for the octet baryon masses, at fixed mπLm_\pi L (1\gg1) finite-volume corrections decrease as mπm_\pi approaches its physical value, provided that the strange quark mass is at or close to its physical value, as in most LQCD setups.Comment: 15 pages, 5 figure

    Theory of Interfacial Plasmon-Phonon Scattering in Supported Graphene

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    One of the factors limiting electron mobility in supported graphene is remote phonon scattering. We formulate the theory of the coupling between graphene plasmon and substrate surface polar phonon (SPP) modes, and find that it leads to the formation of interfacial plasmon-phonon (IPP) modes, from which the phenomena of dynamic anti-screening and screening of remote phonons emerge. The remote phonon-limited mobilities for SiO2_{2}, HfO2_{2}, h-BN and Al2_{2}O3_{3} substrates are computed using our theory. We find that h-BN yields the highest peak mobility, but in the practically useful high-density range the mobility in HfO2_{2}-supported graphene is high, despite the fact that HfO2_{2} is a high-κ\kappa dielectric with low-frequency modes. Our theory predicts that the strong temperature dependence of the total mobility effectively vanishes at very high carrier concentrations. The effects of polycrystallinity on IPP scattering are also discussed.Comment: 33 pages, 7 figure

    Grain boundary ferromagnetism in vanadium-doped In2_2O3_3 thin films

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    Room temperature ferromagnetism was observed in In2_2O3thinfilmsdopedwith5at.temperaturesrangingfrom300to600_3 thin films doped with 5 at.% vanadium, prepared by pulsed laser deposition at substrate temperatures ranging from 300 to 600 \,^{\circ}{\rm C}.XrayabsorptionfinestructuremeasurementindicatedthatvanadiumwassubstitutionallydissolvedintheIn. X-ray absorption fine structure measurement indicated that vanadium was substitutionally dissolved in the In_2OO_3$ host lattice, thus excluding the existence of secondary phases of vanadium compounds. Magnetic measurements based on SQUID magnetometry and magnetic circular dichroism confirm that the magnetism is at grain boundaries and also in the grains. The overall magnetization originates from the competing effects between grains and grain boundaries.Comment: 12 pages, 7 figures, 1 table, accepted by Europhysics Letter

    Neutrino oscillations in de Sitter space-time

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    We try to understand flavor oscillations and to develop the formulae for describing neutrino oscillations in de Sitter space-time. First, the covariant Dirac equation is investigated under the conformally flat coordinates of de Sitter geometry. Then, we obtain the exact solutions of the Dirac equation and indicate the explicit form of the phase of wave function. Next, the concise formulae for calculating the neutrino oscillation probabilities in de Sitter space-time are given. Finally, The difference between our formulae and the standard result in Minkowski space-time is pointed out.Comment: 13 pages, no figure

    Optimization of a fed-batch bioreactor for 1,3-propanediol production using hybrid nonlinear optimal control

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    A nonlinear hybrid system was proposed to describe the fed-batch bioconversion of glycerol to 1,3-propanediol with substrate open loop inputs and pH logic control in previous work [47]. The current work concerns the optimal control of this fed-batch process. We slightly modify the hybrid system to provide a more convenient mathematical description for the optimal control of the fed-batch culture. Taking the feeding instants and the terminal time as decision variables, we formulate an optimal control model with the productivity of 1,3-propanediol as the performance index. Inequality path constraints involved in the optimal control problem are transformed into a group of end-point constraints by introducing an auxiliary hybrid system. The original optimal control problem is associated with a family of approximation problems. The gradients of the cost functional and the end-point constraint functions are derived from the parametric sensitivity system. On this basis, we construct a gradient-based algorithm to solve the approximation problems. Numerical results show that the productivity of 1,3-propanediol can be increased considerably by employing our optimal control policy
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