Generalised regression estimation given imperfectly matched auxiliary data

Generalised regression estimation allows one to make use of available auxiliary information in survey sampling. We develop three types of generalised regression estimator when the auxiliary data cannot be matched perfectly to the sample units, so that the standard estimator is inapplicable. The inference remains design-based. Consistency of the proposed estimators is either given by construction or else can be tested given the observed sample and links. Mean square errors can be estimated. A simulation study is used to explore the potentials of the proposed estimators

On valid descriptive inference from non-probability sample

We examine the conditions under which descriptive inference can be based directly on the observed distribution in a non-probability sample, under both the super-population and quasi-randomisation modelling approaches. Review of existing estimation methods reveals that the traditional formulation of these conditions may be inadequate due to potential issues of under-coverage or heterogeneous mean beyond the assumed model. We formulate unifying conditions that are applicable to both type of modelling approaches. The difficulties of empirically validating the required conditions are discussed, as well as valid inference approaches using supplementary probability sampling. The key message is that probability sampling may still be necessary in some situations, in order to ensure the validity of descriptive inference, but it can be much less resource-demanding provided the presence of a big non-probability sample

Quark number scaling of v2v_2 in transverse kinetic energy and it's implications for coalescence models

We find that a simple extension of the coalescence model is sufficient to incorporate the perfect quark number scaling behavior of the elliptic flow in transverse kinetic energy, recently discovered by the PHENIX Collaboration. The flavor dependence of the elliptic flow can be consistently described in the low and intermediate $p_T$ if the transverse kinetic energy is conserved in the $2\to1$ or $3\to1$ parton coalescence process at the hadronization. Thus suggesting the quark coalescence as a possible hadronization mechanism at low $p_T$ as well.Comment: 4 pages and 3 figures, accepted by PRC rapid comm(Added one figure

Light Induced Hall effect in semiconductors with spin-orbit coupling

We show that optically excited electrons by a circularly polarized light in a semiconductor with spin-orbit coupling subject to a weak electric field will carry a Hall current transverse to the electric field. This light induced Hall effect is a result of quantum interference of the light and the electric field, and can be viewed as a physical consequence of the spin current induced by the electric field. The light induced Hall conductance is calculated for the p-type GaAs bulk material, and the n-type and p-type quantum well structures.Comment: 5 pages, 3 figure