The Single-Particle Spectral Function of 16O^{16}{\rm O}

The influence of short-range correlations on the $p$-wave single-particle spectral function in $^{16}{\rm O}$ is studied as a function of energy. This influence, which is represented by the admixture of high-momentum components, is found to be small in the $p$-shell quasihole wave functions. It is therefore unlikely that studies of quasihole momentum distributions using the $(e,e'p)$ reaction will reveal a significant contribution of high momentum components. Instead, high-momentum components become increasingly more dominant at higher excitation energy. The above observations are consistent with the energy distribution of high-momentum components in nuclear matter.Comment: 5 pages, RevTeX, 3 figure

Momentum Distribution in Nuclear Matter and Finite Nuclei

A simple method is presented to evaluate the effects of short-range correlations on the momentum distribution of nucleons in nuclear matter within the framework of the Green's function approach. The method provides a very efficient representation of the single-particle Green's function for a correlated system. The reliability of this method is established by comparing its results to those obtained in more elaborate calculations. The sensitivity of the momentum distribution on the nucleon-nucleon interaction and the nuclear density is studied. The momentum distributions of nucleons in finite nuclei are derived from those in nuclear matter using a local-density approximation. These results are compared to those obtained directly for light nuclei like $^{16}O$.Comment: 17 pages REVTeX, 10 figures ps files adde

Momentum and Energy Distributions of Nucleons in Finite Nuclei due to Short-Range Correlations

The influence of short-range correlations on the momentum and energy distribution of nucleons in nuclei is evaluated assuming a realistic meson-exchange potential for the nucleon-nucleon interaction. Using the Green-function approach the calculations are performed directly for the finite nucleus $^{16}$O avoiding the local density approximation and its reference to studies of infinite nuclear matter. The nucleon-nucleon correlations induced by the short-range and tensor components of the interaction yield an enhancement of the momentum distribution at high momenta as compared to the Hartree-Fock description. These high-momentum components should be observed mainly in nucleon knockout reactions like $(e,e'p)$ leaving the final nucleus in a state of high excitation energy. Our analysis also demonstrates that non-negligible contributions to the momentum distribution should be found in partial waves which are unoccupied in the simple shell-model. The treatment of correlations beyond the Brueckner-Hartree-Fock approximation also yields an improvement for the calculated ground-state properties.Comment: 12 pages RevTeX, 7 figures postscript files appende

Hole Spectral Function and 2p1h Response Propagator.

The fragmentation of one-nucleon knock-out strength at low energies is considered from the viewpoint of the two particle-one hole (and two hole-one particle) response propagator. The aim is to deal with particle-particle (and hole-hole) as well as particle-hole collectivity simultaneously. This is achieved on a Tamm-Dancoff level by the so-called Faddeev approximation of the 2p1h propagator. Results of this approach illustrate the relevance of this consistent treatment of both particle-particle (hole-hole) and particle-hole collectivity. A further extension, within the framework of 2p1h RPA which was sometimes applied in the past, has serious unsolved problems, some of which are discussed in detail

The changing face of the dodo (Aves: Columbidae:Raphus cucullatus): iconography of the Walghvogel of Mauritius

The dodo (Raphus cucullatus) was a large, flightless pigeon endemic to the island of Mauritius (Indian Ocean). Its unusual appearance was recorded in several 17th-century depictions of live or recently killed birds. It became extinct at the end of the 17th century, and in some subsequent accounts, it was even considered as non-existent. Dodo images became rare from the mid-17th century, but its inclusion in Lewis Carroll’s Alice’s Adventures in Wonderland initiated a change, establishing it as an icon to a much wider public. Since then, illustrations of dodos have been used in all kinds of media, arguably making it the most iconic extinct bird. Here we analyse how the dodo image evolved from 1600 to 2013, using 2D-geometric morphometrics. Our results show that in particular cartoons, animations and logos tend to put an extreme emphasis on the bulging anterior part of the beak, and that the beak is strongly hooked. The variation in dodo images has increased since 1865, culminating in an explosion of shapes during the past decades. The often exaggerated, cartoonesque depiction of the dodo is in line with the long-held but incorrect popular belief that it was a clumsy, tragic bird destined for extinction