Chiral Loops and Ghost States in the Quenched Scalar Propagator

The scalar, isovector meson propagator is analyzed in quenched QCD, using the MQA pole-shifting ansatz to study the chiral limit. In addition to the expected short-range exponential falloff characteristic of a heavy scalar meson, the propagator also exhibits a longer-range, negative metric contribution which becomes pronounced for smaller quark masses. We show that this is a quenched chiral loop effect associated with the anomalous structure of the $\eta '$ propagator in quenched QCD. Both the time dependence and the quark mass dependence of this effect are well-described by a chiral loop diagram corresponding to an $\eta '- \pi$ intermediate state, which is light and effectively of negative norm in the quenched approximation. The relevant parameters of the effective Lagrangian describing the scalar sector of the quenched theory are determined.Comment: 29 pages, 10 figures, Late

A Critical Review of New Mobility Services for Urban Transport

The growing pressure on urban passenger transport systems has increased the demand for new and innovative solutions to increase its efficiency. One approach to tackle this challenge has been the slow but steady shift towards shared mobility services (car-, bike-sharing etc.). Building on these new modes and the developments in information and communication technologies, the concept of “Mobility as a Service” (MaaS) has recently come to light and offers convenient door-to-door transport without the need to own a private vehicle. The term Mobility as a Service (MaaS) stands for buying mobility services based on consumer needs instead of buying the means of mobility. In recent years, various MaaS schemes have been arisen around the world. The objective of this paper is to review these newly existing mobility services and develop an index to evaluate the level of mobility integration for each based on the assumption that higher level of integration is more appealing to travellers. The review presented in this paper allows a comparison among the schemes and provides the background and the key points of MaaS systems that the research community could use for designing surveys. It also provides significant insights to transport operators and authorities on the elements they should take into account to apply an attractive MaaS scheme that could effectively shift demand away from private vehicles

The Ginzburg-Landau Free Energy Functional of Color Superconductivity at Weak Coupling

We derive the Ginzburg-Landau free energy functional of color superconductivity in terms of the thermal diagrams of QCD in its perturbative region. The zero mode of the quadratic term coefficient yields the same transition temperature, including the pre-exponential factor, as the one obtained previously from the Fredholm determinant of the two quark scattering amplitude. All coefficients of the free energy can be made identical to those of a BCS model by setting the Fermi velocity of the latter equal to the speed of light. We also calculate the induced symmetric color condensate near $T_c$ and find that it scales as the cubic power of the dominant antisymmetric color component. We show that in the presence of an inhomogeneity and a nonzero gauge potential, while the color-flavor locked condensate dominates in the bulk, the unlocked condensate, the octet, emerges as a result of a simultaneous color-flavor rotation in the core region of a vortex filament or at the junction of super and normal phases.Comment: 32 pages, Plain Tex, 3 figure

Feasibility Study for “Mobility as a Service” concept in London

Novel mobility services that heavily rely on technological advances could contribute to seamless mobility. Mobility as a Service (MaaS) is such a concept. The objective of the FS-MaaS project is to propose the design of a MaaS concept for London, the MaaS-London, and examine its feasibility. To work towards the concept of MaaS-London, first, the supply and the demand sides of the London transport market are analysed. There are a variety of mobility services supplied in London such as car clubs (car sharing), ride sharing, bike sharing, public transport, rail and taxi which altogether make London an ideal ground to exploit MaaS-London. The MaaS-London is an integrated platform that includes registration and package selection, intermodal journey planning, booking, smart ticketing and payment functions so that the entire chain of transport can be managed in this centralised platform. The most outstanding feature of MaaS-London is the provision of mobility packages, which consist of tailored bundles of mobility services customised to individual needs. The feasibility study indicates that the introduction of MaaS-London will benefit both the supply and the demand side. Transport operators will benefit by creating a larger market via the integrated platform. Travellers will also welcome the concept due to travel expense and time reduction, and better service experience. MaaS-London is a feasible product that can well serve London transport market and contribute to London’s 2020 vision

Comparison of techniques for handling missing covariate data within prognostic modelling studies: a simulation study

Background: There is no consensus on the most appropriate approach to handle missing covariate data within prognostic modelling studies. Therefore a simulation study was performed to assess the effects of different missing data techniques on the performance of a prognostic model. Methods: Datasets were generated to resemble the skewed distributions seen in a motivating breast cancer example. Multivariate missing data were imposed on four covariates using four different mechanisms; missing completely at random (MCAR), missing at random (MAR), missing not at random (MNAR) and a combination of all three mechanisms. Five amounts of incomplete cases from 5% to 75% were considered. Complete case analysis (CC), single imputation (SI) and five multiple imputation (MI) techniques available within the R statistical software were investigated: a) data augmentation (DA) approach assuming a multivariate normal distribution, b) DA assuming a general location model, c) regression switching imputation, d) regression switching with predictive mean matching (MICE-PMM) and e) flexible additive imputation models. A Cox proportional hazards model was fitted and appropriate estimates for the regression coefficients and model performance measures were obtained. Results: Performing a CC analysis produced unbiased regression estimates, but inflated standard errors, which affected the significance of the covariates in the model with 25% or more missingness. Using SI, underestimated the variability; resulting in poor coverage even with 10% missingness. Of the MI approaches, applying MICE-PMM produced, in general, the least biased estimates and better coverage for the incomplete covariates and better model performance for all mechanisms. However, this MI approach still produced biased regression coefficient estimates for the incomplete skewed continuous covariates when 50% or more cases had missing data imposed with a MCAR, MAR or combined mechanism. When the missingness depended on the incomplete covariates, i.e. MNAR, estimates were biased with more than 10% incomplete cases for all MI approaches. Conclusion: The results from this simulation study suggest that performing MICE-PMM may be the preferred MI approach provided that less than 50% of the cases have missing data and the missing data are not MNAR

Transverse momentum distributions inside the nucleon from lattice QCD

We study transverse momentum dependent parton distribution functions (TMDs) with non-local operators in lattice QCD, using MILC/LHPC lattices. Results obtained with a simplified operator geometry show visible dipole deformations of spin-dependent quark momentum densities.United States. Dept. of Energy (grant DE-FG02-94ER40818

Transverse momentum dependent quark densities from Lattice QCD

We study transverse momentum dependent parton distribution functions (TMDs) with non‐local operators in lattice QCD, using MILC∕LHPC lattices. We discuss the basic concepts of the method, including renormalization of the gauge link. Results obtained with a simplified operator geometry show visible dipole deformations of spin‐dependent quark momentum densities.United States. Dept. of Energy (grant DEFG02- 94ER40818

Diquark Condensates and Compact Star Cooling

The effect of color superconductivity on the cooling of quark stars and neutron stars with large quark cores is investigated. Various known and new quark-neutrino processes are studied. As a result, stars being in the color flavor locked (CFL) color superconducting phase cool down extremely fast. Quark stars with no crust cool down too rapidly in disagreement with X-ray data. The cooling of stars being in the N_f =2 color superconducting (2SC) phase with a crust is compatible with existing X-ray data. Also the cooling history of stars with hypothetic pion condensate nuclei and a crust does not contradict the data.Comment: 10 pages, 5 figures, accepted for publication in Ap