Nuclear collective dynamics within Vlasov approach

We discuss, in an investigation based on Vlasov equation, the properties of the isovector modes in nuclear matter and atomic nuclei in relation with the symmetry energy. We obtain numerically the dipole response and determine the strength function for various systems, including a chain of Sn isotopes. We consider for the symmetry energy three parametrizations with density providing similar values at saturation but which manifest very different slopes around this point. In this way we can explore how the slope affects the collective response of finite nuclear systems. We focus first on the dipole polarizability and show that while the model is able to describe the expected mass dependence, A^{5/3}, it also demonstrates that this quantity is sensitive to the slope parameter of the symmetry energy. Then, by considering the Sn isotopic chain, we investigate the emergence of a collective mode, the Pygmy Dipole Resonance (PDR), when the number of neutrons in excess increases. We show that the total energy-weighted sum rule exhausted by this mode has a linear dependence with the square of isospin I=(N-Z)/A, again sensitive to the slope of the symmetry energy with density. Therefore the polarization effects in the isovector density have to play an important role in the dynamics of PDR. These results provide additional hints in the investigations aiming to extract the properties of symmetry energy below saturation.Comment: 7 pages, 6 figure

INFLUENCE OF TEMPERATURE IN DORMANCY PERIOD IN YEARS 2016-2017 ON PEACH AND APRICOT SPECIES OFF SANDY SOILS

The resistance to frost of the varieties studied depends on the species from which it originates and the place of origin, the duration of dormancy and winter temperatures, and, in addition to the genetic determinant of the variety, a different influence from year to year, also had the climatic conditions. During the biological dormancy, the trees of the stone species can withstand minimum temperatures from -26°C to -28°C (apricot), -23°C to -24°C (peach). At these temperatures resist only trees that had good condition of vegetations, and have accumulated many spare substances. According to the climatic data recorded at CCDCPN Dăbuleni and following the observations made, it was pointed out that the temperature oscillations,especially the low temperatures, had a negative impact on the fruit trees in the winter 2015/2016, reaching at frosbite flower buds at apricot and peach species more than 90 %. The winter 2016/2017 was favorable for dormancy period of the fruit tree species, the minimum temperatures did not occur suddenly, and the late frosts did not cause any damage to the fruit species due to the preventive measures

Atypical BCS-BEC crossover induced by quantum-size effects

Quantum-size oscillations of the basic physical characteristics of a confined fermionic condensate are a well-known phenomenon. Its conventional understanding is based on the single-particle physics, whereby the oscillations follow the size-dependent changes in the single-particle density of states. Here we present a study of a cigar-shaped ultracold superfluid Fermi gas, which demonstrates an important many-body aspect of the quantum-size effects, overlooked previously. The many-body physics is revealed in the atypical crossover from the Bardeen-Cooper-Schrieffer (BCS) superfluid to the Bose-Einstein condensate (BEC) induced by the size quantization of the particle motion. Quantized perpendicular spectrum results in the formation of single-particle subbands (shells) so that the aggregate fermionic condensate becomes a coherent mixture of subband condensates. Each time when the lower edge of a subband crosses the chemical potential, the BCS-BEC crossover is approached in this subband, and the aggregate condensate contains both the BCS and BEC-like components.Comment: 7 pages, 5 figure