Ηλεκτρονικά Περιοδικά: επιπτώσεις στη Ανάπτυξη και Διαχείριση της Συλλογής της Βιβλιοθήκης του ΕΚΤ/ΕΙΕ

Περιέχει το πλήρες κείμενοΣτο παρόν άρθρο, αποτυπώνονται κάποιοι προβληματισμοί που αναδύθηκαν κατά την επιλογή και ένταξη επιστημονικών περιοδικών σε ηλεκτρονική μορφή στη συλλογή της βιβλιοθήκης Βιβλιοθήκη Επιστήμης και Τεχνολογίας ΕΚΤ/ΕΙΕ και πώς αυτοί ενσωματώθηκαν στην πολιτική διαμόρφωσης της συλλογής επιστημονικών περιοδικών της Βιβλιοθήκης. Δίνεται μια σύντομη εικόνα του έντυπου και ηλεκτρονικού περιεχομένου της Βιβλιοθήκης ΕΚΤ/ΕΙΕ και γίνεται αναφορά στους ποικίλους τρόπους που οι χρήστες προσεγγίζουν το περιεχόμενο αυτό, ανάλογα με το επιστημονικό τους αντικείμενο και την ηλικία τους

Why do Nilsson quantum numbers remain good at moderate deformations?

The Nilsson model is a simple microscopic model which has been extensively used over the years for the interpretation of a bulk of experimental results. The single particle orbitals in this model are labeled by quantum numbers which are good in the limit of large nuclear deformations. However, it is generally admitted that these quantum numbers remain good even at moderate deformations. We show that this fact is due to the existence of an underlying approximate symmetry, called the proxy-SU(3) symmetry. The implications of proxy-SU(3) on various aspects of nuclear structure will be discussed.Comment: 11 pages, 1 figure, to appear in Nuclear Theory '37, Proceedings of the 37th International Workshop on Nuclear Theory (Rila 2018), ed. M. Gaidarov and N. Minko

Particle-hole symmetry breaking due to Pauli blocking

Particle-hole symmetry has been used on several occasions in nuclear structure over the years. We prove that particle-hole symmetry is broken in nuclear shells possessing the proxy-SU(3) symmetry. The breaking of the symmetry is rooted in the Pauli principle and the short range nature of the nucleon-nucleon interaction. The breaking of the symmetry explains the dominance of prolate over oblate shapes in deformed nuclei and determines the regions of prolate to oblate shape transitions in the nuclear chart. Furthermore, it is related to the existence of specific regions of shape coexistence across the nuclear chart, surrounded by regions in which shape coexistence does not occur.Comment: 9 pages, 2 figures, to appear in HNPS: Advances in Nuclear Physics: Proceedings of the 27th Annual Symposium of the Hellenic Nuclear Physics Society (Athens, 2018), ed. T. Mertzimekis, G. Souliotis, and E. Styliari

Parameter-independent predictions for shape variables of heavy deformed nuclei in the proxy-SU(3) model

Using a new approximate analytic parameter-free proxy-SU(3) scheme, we make predictions of shape observables for deformed nuclei, namely beta and gamma deformation variables, and compare these with empirical data and with predictions by relativistic and non-relativistic mean-field theories.Comment: 6 pages, 11 figures, Proceedings of the 4th Workshop of the Hellenic Institute of Nuclear Physics on New Aspects and Perspectives in Nuclear Physics (HINPw4),Ioannina, Greece, 5-6 May 2017, ed. A. Pako

Magic numbers for shape coexistence

The increasing deformation in atomic nuclei leads to the change of the classical magic numbers (2,8,20,28,50,82..) which dictate the arrangement of nucleons in complete shells. The magic numbers of the three-dimensional harmonic oscillator (2,8,20,40,70...) emerge at deformations around epsilon=0.6. At lower deformations the two sets of magic numbers antagonize, leading to shape coexistence. A quantitative investigation is performed using the usual Nilsson model wave functions and the recently introduced proxy-SU(3) scheme.Comment: 9 pages, 4 figures, to appear in HNPS: Advances in Nuclear Physics: Proceedings of the 27th Annual Symposium of the Hellenic Nuclear Physics Society (Athens, 2018), ed. T. Mertzimekis, G. Souliotis, and E. Styliari

Nucleon numbers for nuclei with shape coexistence

We consider two competing sets of nuclear magic numbers, namely the harmonic oscillator (HO) set (2, 8, 20, 40, 70, 112, 168, 240,...) and the set corresponding to the proxy-SU(3) scheme, possessing shells 0-2, 2-4, 6-12, 14-26, 28-48, 50-80, 82-124, 126-182, 184-256... The two sets provide 0+ bands with different deformation and band-head energies. We show that for proton (neutron) numbers starting from the regions where the quadrupole-quadrupole interaction, as derived by the HO, becomes weaker than the one obtained in the proxy-SU(3) scheme, to the regions of HO shell closure, the shape coexistence phenomenon may emerge. Our analysis suggests that the possibility for appearance of shape coexistence has to be investigated in the following regions of proton (neutron) numbers: 8, 18-20, 34-40, 60-70, 96-112, 146-168, 210-240,...Comment: 8 pages, 1 figure, to appear in HNPS: Advances in Nuclear Physics: Proceedings of the 27th Annual Symposium of the Hellenic Nuclear Physics Society (Athens, 2018), ed. T. Mertzimekis, G. Souliotis, and E. Styliari

Parameter free predictions within the proxy-SU(3) model

Using a new approximate analytic parameter-free proxy-SU(3) scheme, we make predictions of shape observables for deformed nuclei, namely beta and gamma deformation variables, and compare them with empirical data and with predictions by relativistic and non-relativistic mean-field theories. Furthermore, analytic expressions are derived for B(E2) ratios within the proxy-SU(3) model, free of any free parameters, and/or scaling factors. The predicted B(E2) ratios are in good agreement with the experimental data for deformed rare earth nuclides.Comment: 12 pages, 5 figures, to appear in the proceedings of the Workshop on Shapes and Dynamics of Atomic Nuclei: Contemporary Aspects (SDANCA17, Sofia 2017), ed. N. Minko

Prolate dominance and prolate-oblate shape transition in the proxy-SU(3) model

Using a new approximate analytic parameter-free proxy-SU(3) scheme, we make simple predictions for the global feature of prolate dominance in deformed nuclei and the locus of the prolate-oblate shape transition and compare these with empirical data.Comment: 5 pages, 1 figure, 3 tables, Proceedings of the 4th Workshop of the Hellenic Institute of Nuclear Physics on New Aspects and Perspectives in Nuclear Physics (HINPw4), Ioannina, Greece, 5-6 May 2017, ed. A. Pako

Proxy-SU(3) symmetry in heavy nuclei: Prolate dominance and prolate-oblate shape transition

Using a new approximate analytic parameter-free proxy-SU(3) scheme, simple predictions for the global feature of prolate dominance and for the locus of the prolate-oblate shape transition have been made and compared with empirical data. Emphasis is placed on the mechanism leading to the breaking of the particle-hole symmetry, which is instrumental in shaping up these predictions. It turns out that this mechanism is based on the SU(3) symmetry and the Pauli principle alone, without reference to any specific Hamiltonian.Comment: 10 pages, 4 tables, to appear in the proceedings of the Workshop on Shapes and Dynamics of Atomic Nuclei: Contemporary Aspects (SDANCA17, Sofia 2017), ed. N. Minko

Parameter-independent predictions for nuclear shapes and B(E2) transition rates in the proxy-SU(3) model

Using a new approximate analytic parameter-free proxy-SU(3) scheme, we make predictions of shape observables for actinides and superheavy elements, namely beta and gamma deformation variables, and compare these with predictions by relativistic and non-relativistic mean-field theories. Furthermore, we make predictions for B(E2) transition rates of deformed nuclei and compare these with existing data and predictions of other theoretical approaches.Comment: 6 pages, 3 figures, to appear in the proceedings of the 26th Annual Symposium of the Hellenic Nuclear Physics Society (HNPS2017), Anavyssos, Greece, 9-10 June 2017, ed. Ch. Tsabaris, R. Vlastou, M. Kokkoris, and D. Patiris. arXiv admin note: text overlap with arXiv:1711.09201, arXiv:1711.0859