Effective action and density functional theory

The effective action for the charge density and the photon field is proposed as a generalization of the density functional. A simple definition is given for the density functional, as the functional Legendre transform of the generator functional of connected Green functions for the density and the photon field, offering systematic approximation schemes. The leading order of the perturbation expansion reproduces the Hartree-Fock equation. A renormalization group motivated method is introduced to turn on the Coulomb interaction gradually and to find corrections to the Hartree-Fock and the Kohn-Sham schemes.Comment: New references and a numerical algorithm added, to appear in Phys. Rev. B. 30 pages, no figure

Gaussian quantum operator representation for bosons

We introduce a Gaussian quantum operator representation, using the most general possible multimode Gaussian operator basis. The representation unifies and substantially extends existing phase-space representations of density matrices for Bose systems and also includes generalized squeezed-state and thermal bases. It enables first-principles dynamical or equilibrium calculations in quantum many-body systems, with quantum uncertainties appearing as dynamical objects. Any quadratic Liouville equation for the density operator results in a purely deterministic time evolution. Any cubic or quartic master equation can be treated using stochastic methods

The diabetes risk phenotype of young women with recent gestational diabetes.

Context: The pathogenesis of type 2 diabetes (T2D) is still incompletely understood. In-depth phenotyping of young individuals at risk for T2D can contribute to the understanding of this process. Objective: To metabolically characterize women with recent gestational diabetes (GDM), an at-risk cohort for T2D. Study participants: 147 consecutively recruited women 3-16 months after pregnancy, women who had GDM and women after a normoglycemic pregnancy (controls) in a 2:1 ratio Design: Mono-center cross-sectional analysis (PPS-Diab study) Methods: 5-point OGTT with calculation of insulin sensitivity (ISI) and disposition index (DI; validation by euglycemic clamp and IVGTT), anthropometrics, medical and family history, clinical chemistry and biomarkers, statistical modelling, MRI/MRS substudy (body fat distribution, liver and muscle fat; n=66) Results: Compared to control subjects, women post GDM had a reduced DI, higher levels of plasma fetuin-A and a lower ISI. A low ISI was also the major determinant of pathologic glucose tolerance after GDM. The factors most strongly predictive of low insulin sensitivity were high plasma leptin, BMI, triglycerides, and waist circumference. Ectopic lipids showed no BMI-independent associations with having had GDM or low insulin sensitivity in an MRI substudy. Conclusions: We found that beta cell function is already impaired in women with recent GDM, a young at-risk cohort for T2D. Additionally, our data suggest that fetuin-A and leptin signaling may be important early contributors to the pathogenesis of T2D, at this disease stage equally or more relevant than ectopic lipids and low-grade inflammation

Fluid-dynamical description of the gap fluctuations of two trapped fermion species

We apply a recent generalisation of the fluid-dynamical scheme developed for two trapped fermion species with pairing interactions to examine the fluctuations of the gap density coupled to the particle transition density at low energy. The dynamical scheme satisfies Kohn's theorem for both the particle density and the pairing gap. We analyse the form of the gap fluctuations in a spherical trap in terms of their multipolarity and the interaction strength, and find that coupling to the particle density produces considerable stiffness of the gap transition density together with compression towards the centre of the trap