Axially deformed relativistic Hartree Bogoliubov with separable pairing force

A separable form of pairing interaction in the $^{1}S_{0}$ channel has been introduced and successfully applied in the description of both static and dynamic properties of superfluid nuclei. By adjusting the parameters to reproduce the pairing properties of the Gogny force in nuclear matter, this separable pairing force is successful in depicting the pairing properties of ground states and vibrational excitations of spherical nuclei on almost the same footing as the original Gogny force. In this article, we extend these investigations for Relativistic Hartree Bogoliubov theory in deformed nuclei with axial symmetry (RHBZ) using the same separable pairing interaction. In order to preserve translational invariance we construct one- and two-dimensional Talmi-Moshinsky brackets for the cylindrical harmonic oscillator basis. We show that the matrix elements of this force can then be expanded in a series of separable terms. The convergence of this expansion is investigated for various deformations. We observe a relatively fast convergence. This allows for a considerable reduction in computing time as compared to RHBZ-calculations with the full Gogny force in the pairing channel. As an example we solve the RHBZ equations with this separable pairing force for the ground states of the chain of Sm-isotopes. Good agreement with the experimental data as well as with other theoretical results is achieved.Comment: 8 pages, 5 figures. accepted by Phys. Rev.

Examining Avian Diversity in Acadia National Park Through Time

Ecosystems experience change due to both natural causes and anthropogenic impact such as habitat fragmentation and climate change. Avian species are used as habitat indicators to observe ecosystem integrity and have been observed to experience changes in biodiversity due to anthropogenic impact. This study examines the temporal and spatial changes of avian biodiversity in Acadia National Park. We seek to understand (1) how the alpha diversity has changed over time on Mount Desert Island and Schoodic Peninsula, (2) how beta diversity has changed over time for Mount Desert Island and Schoodic Peninsula (3) how the Schoodic Woods Campground can be used as a model for avian biodiversity change due to human impact. This study demonstrates that the avian communities of Acadia National Park have experienced change. We found that for both Mount Desert Island and Schoodic Peninsula the alpha diversity and beta diversity have increased over time. Comparing Mount Desert Island to Schoodic Peninsula over time resulted in a decrease of beta diversity. Although alpha diversity exhibited significant change surrounding the Schoodic Woods Campground, an increase in species richness closer to surface edges for trails, and campground, there was no trend for beta diversity. The observed trends could be due to biotic homogenization as well as edge effect leading to increased levels of biodiversity

Constraining the nuclear equation of state at subsaturation densities

Only one third of the nucleons in $^{208}$Pb occupy the saturation density area. Consequently nuclear observables related to average properties of nuclei, such as masses or radii, constrain the equation of state (EOS) not at saturation density but rather around the so-called crossing density, localised close to the mean value of the density of nuclei: $\rho\simeq$0.11 fm$^{-3}$. This provides an explanation for the empirical fact that several EOS quantities calculated with various functionals cross at a density significantly lower than the saturation one. The third derivative M of the energy at the crossing density is constrained by the giant monopole resonance (GMR) measurements in an isotopic chain rather than the incompressibility at saturation density. The GMR measurements provide M=1110 $\pm$ 70 MeV (6% uncertainty), whose extrapolation gives K$_\infty$=230 $\pm$ 40 MeV (17% uncertainty).Comment: 4 pages, 4 figure

Soil Compaction Effects on Root-Zone Hydrology and Vegetation in Boreal Forest Clearcuts

Soil compaction is a common consequence of forestry traffic traversing unprotected, moist soils; it decreases porosity and affects hydraulic conductivity even in coarse-textured soils. The aim here was to study root-zone hydrology and vegetation in three microsites (in, between, and beside wheel tracks) 4 to 5 yr after forwarder traffic, on stony and sandy till soils in two clearcuts in northern Sweden. Measurements of soil volumetric water content (VWC), vegetation indicators and one-dimensional hydrological modeling (Hydrus-1D) of wheel tracks and undisturbed soil were conducted. Soil VWC was monitored hourly during 2017 and 2018 in three or four plots along a slope on each site. Soil VWC was also measured once with a portable sensor in 117 plots along two slopes at each site, where the vegetation was recorded and analyzed using Ellenberg indicator indexes. Soil VWC was highest in wheel tracks and lowest between tracks; this was corroborated by the species composition in the wheel tracks (Ellenberg indicator for soil moisture). Bare soil was more frequent in wheel tracks and between tracks than in undisturbed soil. The model simulations indicated that the changed soil hydraulic properties influenced the VWC results in the wheel tracks. However, the differences in average pressure heads in the root zone were small between the microsites and only apparent during dry periods. In the wheel tracks, air-filled porosity was <0.10 m3 m-3, indicating insufficient soil aeration during 82% (Site T) and 23% (Site R) of the 2017 growing season. Insufficient aeration could be one explanation for the presence of some still unvegetated areas

Fission barriers in covariant density functional theory: extrapolation to superheavy nuclei

Systematic calculations of fission barriers allowing for triaxial deformation are performed for even-even superheavy nuclei with charge number $Z=112-120$ using three classes of covariant density functional models. The softness of nuclei in the triaxial plane leads to an emergence of several competing fission pathes in the region of the inner fission barrier in some of these nuclei. The outer fission barriers are considerably affected by triaxiality and octupole deformation. General trends of the evolution of the inner and the outer fission barrier heights are discussed as a function of the particle numbers.Comment: 24 pages, 8 tables, 12 figure

Nuclear incompressibility in the quasilocal density functional theory

We explore the ability of the recently established quasilocal density functional theory for describing the isoscalar giant monopole resonance. Within this theory we use the scaling approach and perform constrained calculations for obtaining the cubic and inverse energy weighted moments (sum rules) of the RPA strength. The meaning of the sum rule approach in this case is discussed. Numerical calculations are carried out using Gogny forces and an excellent agreement is found with HF + RPA results previously reported in literature. The nuclear matter compression modulus predicted in our model lies in the range 210-230 MeV which agrees with earlier findings. The information provided by the sum rule approach in the case of nuclei near the neutron drip line is also discussed.Comment: 10 pages, LaTe

Relativistic Continuum Quasiparticle Random Phase Approximation in Spherical Nuclei

We have calculated the strength distributions of the dipole response in spherical nuclei, ranging all over the periodic table. The calculations were performed within two microscopic models: the discretized quasiparticle random phase approximation (QRPA) and the quasiparticle continuum RPA, which takes into account the coupling of the single-particle continuum in an exact way. Pairing correlations are treated with the BCS model. In the calculations, two density functionals were used, namely the functional PC-F1 and the functional DD-PC1. Both are based on relativistic point coupling Lagrangians. It is explicitly shown that this model is capable of reproducing the giant as well as the pygmy dipole resonance for open-shell nuclei in a high level of quantitative agreement with the available experimental observations.Comment: 9 pages, 6 figures, accepted for publication in Phys. Pev.

Relativistic quasiparticle time blocking approximation. Dipole response of open-shell nuclei

The self-consistent Relativistic Quasiparticle Random Phase Approximation (RQRPA) is extended by the quasiparticle-phonon coupling (QPC) model using the Quasiparticle Time Blocking Approximation (QTBA). The method is formulated in terms of the Bethe-Salpeter equation (BSE) in the two-quasiparticle space with an energy-dependent two-quasiparticle residual interaction. This equation is solved either in the basis of Dirac states forming the self-consistent solution of the ground state or in the momentum representation. Pairing correlations are treated within the Bardeen-Cooper-Schrieffer (BCS) model with a monopole-monopole interaction. The same NL3 set of the coupling constants generates the Dirac-Hartree-BCS single-quasiparticle spectrum, the static part of the residual two-quasiparticle interaction and the quasiparticle-phonon coupling amplitudes. A quantitative description of electric dipole excitations in the chain of tin isotopes (Z=50) with the mass numbers A = 100, 106, 114, 116, 120, and 130 and in the chain of isotones with (N=50) 88-Sr, 90-Zr, 92-Mo is performed within this framework. The RQRPA extended by the coupling to collective vibrations generates spectra with a multitude of '2q+phonon' (two quasiparticles plus phonon) states providing a noticeable fragmentation of the giant dipole resonance as well as of the soft dipole mode (pygmy resonance) in the nuclei under investigation. The results obtained for the photo absorption cross sections and for the integrated contributions of the low-lying strength to the calculated dipole spectra agree very well with the available experimental data.Comment: 43 pages, 3 figure