Microscopically-based energy density functionals for nuclei using the density matrix expansion: Implementation and pre-optimization

In a recent series of papers, Gebremariam, Bogner, and Duguet derived a microscopically based nuclear energy density functional by applying the Density Matrix Expansion (DME) to the Hartree-Fock energy obtained from chiral effective field theory (EFT) two- and three-nucleon interactions. Due to the structure of the chiral interactions, each coupling in the DME functional is given as the sum of a coupling constant arising from zero-range contact interactions and a coupling function of the density arising from the finite-range pion exchanges. Since the contact contributions have essentially the same structure as those entering empirical Skyrme functionals, a microscopically guided Skyrme phenomenology has been suggested in which the contact terms in the DME functional are released for optimization to finite-density observables to capture short-range correlation energy contributions from beyond Hartree-Fock. The present paper is the first attempt to assess the ability of the newly suggested DME functional, which has a much richer set of density dependencies than traditional Skyrme functionals, to generate sensible and stable results for nuclear applications. The results of the first proof-of-principle calculations are given, and numerous practical issues related to the implementation of the new functional in existing Skyrme codes are discussed. Using a restricted singular value decomposition (SVD) optimization procedure, it is found that the new DME functional gives numerically stable results and exhibits a small but systematic reduction of our test $\chi^2$ function compared to standard Skyrme functionals, thus justifying its suitability for future global optimizations and large-scale calculations.Comment: 17 pages, 6 figure

Community case management improves use of treatment for childhood diarrhea, malaria and pneumonia in a remote district of Ethiopia

Background: Ethiopia’s Health Extension Workers (HEW) deliver preventive interventions and treat childhood diarrhea and malaria, but not pneumonia. Most of Ethiopia’s annual estimated 4 million childhood pneumonia cases go untreated. Objective: Evaluate the performance of volunteers in providing Community Case Management (CCM) for diarrhea,fever and pneumonia – in a pre-HEW setting in Liben Woreda, Oromiya Regional State. Methods: Save the Children supported Ministry of Health and communities to deliver child survival interventions from 1997-2006. We obtained permission in 2005 to train 45 volunteers from remote kebeles in CCM. We evaluated the strategy through reviewing registers and supervision records; examining CCM workers; focus group discussions;and three household surveys. Results: The CCM workers treated 4787 cases, mainly: malaria (36%), pneumonia (26%), conjunctivitis (14%), and watery diarrhea with some dehydration (12%). They saw 2.5 times more cases of childhood fever, pneumonia, and diarrhea than all the woreda’s health facility staff combined. Quality of care was good. Conclusion: The availability, quality, demand, and use of CCM were high. These CCM workers were less educated and less trained than HEWs who perform complicated tasks (Rapid Diagnostic Tests) and dispense expensive antimalarial drugs like Coartem®. They should also treat pneumonia with inexpensive drugs like cotrimoxazole to help achieve Millennium Development Goal 4.

Instabilities in the Nuclear Energy Density Functional

In the field of Energy Density Functionals (EDF) used in nuclear structure and dynamics, one of the unsolved issues is the stability of the functional. Numerical issues aside, some EDFs are unstable with respect to particular perturbations of the nuclear ground-state density. The aim of this contribution is to raise questions about the origin and nature of these instabilities, the techniques used to diagnose and prevent them, and the domain of density functions in which one should expect a nuclear EDF to be stable.Comment: Special issue "Open Problems in Nuclear Structure Theory" of Jour.Phys.G - accepted. 7 pages, 2 figure

Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces

A recent calculation of the nuclear energy density functional from chiral two- and three-nucleon forces is extended to the isovector terms pertaining to different proton and neutron densities. An improved density-matrix expansion is adapted to the situation of small isospin-asymmetries and used to calculate in the Hartree-Fock approximation the density-dependent strength functions associated with the isovector terms. The two-body interaction comprises of long-range multi-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition, the leading order chiral three-nucleon interaction is employed with its parameters fixed in computations of nuclear few-body systems. With this input one finds for the asymmetry energy of nuclear matter the value $A(\rho_0) \simeq 26.5\,$MeV, compatible with existing semi-empirical determinations. The strength functions of the isovector surface and spin-orbit coupling terms come out much smaller than those of the analogous isoscalar coupling terms and in the relevant density range one finds agreement with phenomenological Skyrme forces. The specific isospin- and density-dependences arising from the chiral two- and three-nucleon interactions can be explored and tested in neutron-rich systems.Comment: 14 pages, 7 figures, to be published in European Physical Journal

Nuclear energy density functional from chiral two- and three-nucleon interactions

An improved density-matrix expansion is used to calculate the nuclear energy density functional from chiral two- and three-nucleon interactions. The two-body interaction comprises long-range one- and two-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition we employ the leading order chiral three-nucleon interaction with its parameters $c_E, c_D$ and $c_{1,3,4}$ fixed in calculations of nuclear few-body systems. With this input the nuclear energy density functional is derived to first order in the two- and three-nucleon interaction. We find that the strength functions $F_\nabla(\rho)$ and $F_{so}(\rho)$ of the surface and spin-orbit terms compare in the relevant density range reasonably with results of phenomenological Skyrme forces. However, an improved description requires (at least) the treatment of the two-body interaction to second order. This observation is in line with the deficiencies in the nuclear matter equation of state $\bar E(\rho)$ that remain in the Hartree-Fock approximation with low-momentum two- and three-nucleon interactions.Comment: 16 pages, 12 figures, submitted to Eur. Phys. J.

Using the Wigner-Ibach Surmise to Analyze Terrace-Width Distributions: History, User's Guide, and Advances

A history is given of the applications of the simple expression generalized from the surmise by Wigner and also by Ibach to extract the strength of the interaction between steps on a vicinal surface, via the terrace width distribution (TWD). A concise guide for use with experiments and a summary of some recent extensions are provided.Comment: 11 pages, 4 figures, reformatted (with revtex) version of refereed paper for special issue of Applied Physics A entitled "From Surface Science to Device Physics", in honor of the retirements of Prof. H. Ibach and Prof. H. L\"ut

Academic careers in global pulmonary and critical care medicine: perspectives from experts in the field

Academic global pulmonary/critical care medicine (PCCM) remains a relatively novel concept not fully embraced by all training programs, so PCCM early-career professionals may have little guidance in building successful careers in this field. To highlight various approaches used by current PCCM faculty to incorporate global health into their academic careers, speakers from a global health careers mini symposia held at the 2017 and 2018 American Thoracic Society International Conferences were invited to submit perspectives reflecting on academic PCCM and global health. The collection of essays was collated into a single manuscript. Eight current global PCCM faculty from diverse geographic and professional backgrounds provide experiential guidance for early-career professionals interested in global academic PCCM. Trainees and junior faculty interested in academic global PCCM will find innumerable obstacles to developing this non-traditional career pathway, but there exist diverse pathways to success

The nuclear energy density functional formalism

The present document focuses on the theoretical foundations of the nuclear energy density functional (EDF) method. As such, it does not aim at reviewing the status of the field, at covering all possible ramifications of the approach or at presenting recent achievements and applications. The objective is to provide a modern account of the nuclear EDF formalism that is at variance with traditional presentations that rely, at one point or another, on a {\it Hamiltonian-based} picture. The latter is not general enough to encompass what the nuclear EDF method represents as of today. Specifically, the traditional Hamiltonian-based picture does not allow one to grasp the difficulties associated with the fact that currently available parametrizations of the energy kernel $E[g',g]$ at play in the method do not derive from a genuine Hamilton operator, would the latter be effective. The method is formulated from the outset through the most general multi-reference, i.e. beyond mean-field, implementation such that the single-reference, i.e. "mean-field", derives as a particular case. As such, a key point of the presentation provided here is to demonstrate that the multi-reference EDF method can indeed be formulated in a {\it mathematically} meaningful fashion even if $E[g',g]$ does {\it not} derive from a genuine Hamilton operator. In particular, the restoration of symmetries can be entirely formulated without making {\it any} reference to a projected state, i.e. within a genuine EDF framework. However, and as is illustrated in the present document, a mathematically meaningful formulation does not guarantee that the formalism is sound from a {\it physical} standpoint. The price at which the latter can be enforced as well in the future is eventually alluded to.Comment: 64 pages, 8 figures, submitted to Euroschool Lecture Notes in Physics Vol.IV, Christoph Scheidenberger and Marek Pfutzner editor