Systematic vertex corrections through iterative solution of Hedin's equations beyond the it GW approximation

We present a general procedure for obtaining progressively more accurate functional expressions for the electron self-energy by iterative solution of Hedin's coupled equations. The iterative process starting from Hartree theory, which gives rise to the GW approximation, is continued further, and an explicit formula for the vertex function from the second full cycle is given. Calculated excitation energies for a Hubbard Hamiltonian demonstrate the convergence of the iterative process and provide further strong justification for the GW approximation

Aerodynamic and acoustic behavior of a YF-12 inlet at static conditions

An aeroacoustic test program to determine the cause of YF-12 inlet noise suppression was performed with a YF-12 aircraft at ground static conditions. Data obtained over a wide range of engine speeds and inlet configurations are reported. Acoustic measurements were made in the far field and aerodynamic and acoustic measurements were made inside the inlet. The J-58 test engine was removed from the aircraft and tested separately with a bellmouth inlet. The far field noise level was significantly lower for the YF-12 inlet than for the bellmouth inlet at engine speeds above 5500 rpm. There was no evidence that noise suppression was caused by flow choking. Multiple pure tones were reduced and the spectral peak near the blade passing frequency disappeared in the region of the spike support struts at engine speeds between 6000 and 6600 rpm

Comment on "Quantum Confinement and Optical Gaps in Si Nanocrystals"

We show that the method used by Ogut, Chelikowsky and Louie (Phys. Rev. Lett. 79, 1770 (1997)) to calculate the optical gap of Si nanocrystals omits an electron-hole polarization energy. When this contribution is taken into account, the corrected optical gap is in excellent agreement with semi-empirical pseudopotential calculations.Comment: 3 pages, 1 figur

Density-Polarization Functional Theory of the response of a periodic insulating solid to an electric field.

The response of an infinite, periodic, insulating, solid to an infinitesimally small electric field is investigated in the framework of Density Functional Theory. We find that the applied perturbing potential is not a unique functional of the periodic density change~: it depends also on the change in the macroscopic {\em polarization}. Moreover, the dependence of the exchange-correlation energy on polarization induces an exchange-correlation electric field. These effects are exhibited for a model semiconductor. We also show that the scissor-operator technique is an approximate way of bypassing this polarization dependence.Comment: 11 pages, 1 Fig

Efficient total energy calculations from self-energy models

We propose a new method for calculating total energies of systems of interacting electrons, which requires little more computational resources than standard density-functional theories. The total energy is calculated within the framework of many-body perturbation theory by using an efficient model of the self-energy, that nevertheless retains the main features of the exact operator. The method shows promising performance when tested against quantum Monte Carlo results for the linear response of the homogeneous electron gas and structural properties of bulk silicon

Spectra and total energies from self-consistent many-body perturbation theory

With the aim of identifying universal trends, we compare fully self-consistent electronic spectra and total energies obtained from the GW approximation with those from an extended GW Gamma scheme that includes a nontrivial vertex function and the fundamentally distinct Bethe-Goldstone approach based on the T matrix. The self-consistent Green's function G, as derived from Dyson's equation, is used not only in the self-energy but also to construct the screened interaction W for a model system. For all approximations we observe a similar deterioration of the spectrum, which is not removed by vertex corrections. In particular, satellite peaks are systematically broadened and move closer to the chemical potential. The corresponding total energies are universally raised, independent of the system parameters. Our results, therefore, suggest that any improvement in total energy due to self-consistency, such as for the electron gas in the GW approximation, may be fortuitous. [S0163-1829 (98)05040-1]

Dynamic image potential at an Al(111) surface

We evaluate the electronic self-energy Sigma(E) at an Al(111) surface using the GW space-time method. This self-energy automatically includes the image potential V-im not present in any local-density approximation for exchange and correlation. We solve the energy-dependent quasiparticle equations and calculate the effective local potential experienced by electrons in the near-surface region. The relative contribution of exchange proves to be very different for states above the Fermi level. The image-plane position for interacting electrons is closer to the surface than for the purely electrostatic effects felt by test charges, and, like its classical counterpart, is drawn inwards by the effects of atomic structure

Undergraduate Medical Education Sex- and Gender-based Education: An Institutional Audit and Integration Project

Background: While evidence-based medicine (EBM) supports the incorporation of Sex- and Gender-based Medicine (SGBM) into patient care, a significant gap exists in its translation to current undergraduate medical education (UME). Several studies assessing medical student and resident physician knowledge regarding SGBM demonstrate suboptimal awareness, knowledge base, and clinical incorporation. There is urgent need to evaluate UME under a SGBM-focused lens, to emphasize the existing SGBM content, and to identify additional opportunities for inclusion. Method: Lectures from two pre-clinical UME modules, ‘Cardiovascular’ (CV) and ‘Musculoskeletal/ Dermatology’ (MSK/Derm), at the University of Alabama at Birmingham School of Medicine were subjected to a SGBM taskforce audit. Taskforce auditors were tasked with 1) assessing for pre-existing inclusion of SGBM as well as 2) opportunities for SGBM incorporation. Opportunities for inclusion were identified by a taskforce SGBM expert. Evidence-based SGBM material (e.g. slides) to fill the opportune gaps were subsequently created for module director consideration and ready incorporation. Post-audit follow-up of SGBM incorporation and uptake was completed for both modules. Results: Sixty-four lectures in the MSK/Derm and 23 CV lectures were reviewed by the SGBM audit taskforce. Approximately a third (36%) of all sessions included an element of pre-existing SGBM material (35% of CV; 36% MSK/Derm). Fourteen CV-specific SGBM opportunities were identified, and correlative SGBM inclusive material, was given to the CV module directors; thirteen of these were incorporated (92.8%). Nine MSK/Derm-specific SGBM opportunities were identified with correlative SGBM-inclusive material provided; two (22%) of these were incorporated. Conclusion: Inclusion of SGBM into medical school curriculum is important for comprehensive medical education and ultimately, for patient care. Identifying and collaborating on SGBM educational opportunities will be crucial for its timely uptake into the UME world. The creation of a dedicated taskforce which searches for inclusion opportunities across the curriculum is one approach to increase SGBM within UME.https://jdc.jefferson.edu/sexandgenderhealth/1031/thumbnail.jp

Optimized Effective Potential for Extended Hubbard Model

Antiferromagnetic and charge ordered Hartree-Fock solutions of the one-band Hubbard model with on-site and nearest-neighbor Coulomb repulsions are exactly mapped onto an auxiliary local Kohn-Sham (KS) problem within a density-functional theory. The mapping provides a new insight into the interpretation of the KS equations. (i) With an appropriate choice of the basic variable, there is a universal form of the KS potential, which is applicable both for the antiferromagnetic and the charge ordered solutions. (ii) The Kohn-Sham and Hartree-Fock eigenvalues are interconnected by a scaling transformation. (iii) The band-gap problem is attributed to the derivative discontinuity of the basic variable as the function of the electron number, rather than a finite discontinuity of the KS potential. (iv) It is argued that the conductivity gap and the energies of spin-wave excitations can be entirely defined by the parameters of the ground state and the KS eigenvalues.Comment: 21 page, 3 figure