Improved lower bounds for the ground-state energy of many-body systems

New lower bounds for the binding energy of a quantum-mechanical system of interacting particles are presented. The new bounds are expressed in terms of two-particle quantities and improve the conventional bounds of the Hall-Post type. They are constructed by considering not only the energy in the two-particle system, but also the structure of the pair wave function. We apply the formal results to various numerical examples, and show that in some cases dramatic improvement over the existing bounds is reached.Comment: 29 pages, 5 figures, to be published in Phys. Rev.

In medium T-matrix for superfluid nuclear matter

We study a generalized ladder resummation in the superfluid phase of the nuclear matter. The approach is based on a conserving generalization of the usual T-matrix approximation including also anomalous self-energies and propagators. The approximation here discussed is a generalization of the usual mean-field BCS approach and of the in medium T-matrix approximation in the normal phase. The numerical results in this work are obtained in the quasi-particle approximation. Properties of the resulting self-energy, superfluid gap and spectral functions are studied.Comment: 38 pages, 19 figures, Introduction rewritten, Refs. adde

Self-consistent Green's function approaches

We present the fundamental techniques and working equations of many-body Green's function theory for calculating ground state properties and the spectral strength. Green's function methods closely relate to other polynomial scaling approaches discussed in chapters 8 and 10. However, here we aim directly at a global view of the many-fermion structure. We derive the working equations for calculating many-body propagators, using both the Algebraic Diagrammatic Construction technique and the self-consistent formalism at finite temperature. Their implementation is discussed, as well as the inclusion of three-nucleon interactions. The self-consistency feature is essential to guarantee thermodynamic consistency. The pairing and neutron matter models introduced in previous chapters are solved and compared with the other methods in this book.Comment: 58 pages, 14 figures, Submitted to Lect. Notes Phys., "An advanced course in computational nuclear physics: Bridging the scales from quarks to neutron stars", M. Hjorth-Jensen, M. P. Lombardo, U. van Kolck, Editor

Evolution des contraintes résiduelles de l'acier à roulements EZ100CD17 en fonction des conditions d'élaboration, en fatigue de contact : mesures par diffraction X

Les paramètres microstructuraux, les contraintes résiduelles initiales influent sur la caractéristiques mécaniques, la tenue en fatigue de l'acier à roulements cryotechnique EZ100CD17. Pour faire varier la microstructure, plusieurs traitements thermiques sont réalisés. Les fractions volumiques de phases, les caractéristiques mécaniques, par exemple, sont modifiées. Les influences des traitements thermiques, des conditions d'usinage sur l'état de contraintes résiduelles seront étudiées. Nous mettrons ensuite en évidence l'influence de la microstructure sur l'évolution des contraintes résiduelles après sollicitation mécanique en fatigue de contact, à la température de l'azote liquide. Les contraintes résiduelles du premier ordre et du second ordre, mesurées en diffraction X pour les plans {211} de la martensite, seront considérées. Nous montrerons ainsi que les traitements thermiques et les essais mécaniques influencent à la fois les contraintes résiduelles macroscopiques et microscopiques.Microstructural parameters, residual stresses have a large influence on mechanical properties, fatigue behaviour in the EZ100CD17 ball bearing steel. Various thermal treatments were realized in order to change the microstructure. The volume fractions of phases and mechanical characteristics, for example, are modified. The influences of heat treatments, conditions of grinding will be studied. The influence of microstructure on the evolution of residual stresses after mechanical testing in loading contact fatigue will then be shown. The residual stresses of fïrst et second order for the {211} planes of martensite will be considered, measured by X-ray difraction. The macroscopic and microscopic residual stresses are influenced by the thermal treatments and by mechanical testing

Open versus robotic-assisted laparoscopic posterior component separation in complex abdominal wall repair

In this retrospective European multicentre study evaluating surgical treatment of 169 patients with a complex ventral incisional hernia, robotic-assisted laparoscopic transversus abdominis release results in a significant decrease in duration of postoperative hospital stay, and short-term postoperative complications when compared with open transversus abdominis release.Background Transversus abdominis release (TAR) is a surgical technique used in the treatment of complex ventral hernias. The aim of this study was to compare outcomes of open (oTAR) versus robotic-assisted (rTAR) posterior component separation by TAR. Methods Consecutive patients at two European hernia centres who underwent bilateral TAR were included. The primary endpoint was the duration of postoperative hospital stay. Results Data from 90 rTAR and 79 oTAR operations were evaluated. Patient demographics were similar between groups in terms of age, sex, BMI, and co-morbidities. There were more smokers, and hernias were larger in the oTAR group (width 8.7 cm versus 10.0 cm; P = 0.031, length 11.6 cm versus 14.1 cm; P = 0.005). Duration of postoperative hospital stay was significantly shorter in the rTAR group (3.4 days versus 6.9 days; P 0.009) were similar. Conclusion Patients with ventral incisional hernias who undergo bilateral rTAR had significantly shorter postoperative hospital stays and fewer short-term complications compared with patients undergoing bilateral oTAR

Open versus robotic-assisted laparoscopic posterior component separation in complex abdominal wall repair

In this retrospective European multicentre study evaluating surgical treatment of 169 patients with a complex ventral incisional hernia, robotic-assisted laparoscopic transversus abdominis release results in a significant decrease in duration of postoperative hospital stay, and short-term postoperative complications when compared with open transversus abdominis release.Background Transversus abdominis release (TAR) is a surgical technique used in the treatment of complex ventral hernias. The aim of this study was to compare outcomes of open (oTAR) versus robotic-assisted (rTAR) posterior component separation by TAR. Methods Consecutive patients at two European hernia centres who underwent bilateral TAR were included. The primary endpoint was the duration of postoperative hospital stay. Results Data from 90 rTAR and 79 oTAR operations were evaluated. Patient demographics were similar between groups in terms of age, sex, BMI, and co-morbidities. There were more smokers, and hernias were larger in the oTAR group (width 8.7 cm versus 10.0 cm; P = 0.031, length 11.6 cm versus 14.1 cm; P = 0.005). Duration of postoperative hospital stay was significantly shorter in the rTAR group (3.4 days versus 6.9 days; P 0.009) were similar. Conclusion Patients with ventral incisional hernias who undergo bilateral rTAR had significantly shorter postoperative hospital stays and fewer short-term complications compared with patients undergoing bilateral oTAR