575 research outputs found
Structure and three-body decay of Be resonances
The complex-rotated hyperspherical adiabatic method is used to study the
decay of low-lying Be resonances into one neutron and two
-particles. We investigate the six resonances above the break-up
threshold and below 6 MeV: , and . The
short-distance properties of each resonance are studied, and the different
angular momentum and parity configurations of the Be and He two-body
substructures are determined. We compute the branching ratio for sequential
decay via the Be ground state which qualitatively is consistent with
measurements. We extract the momentum distributions after decay directly into
the three-body continuum from the large-distance asymptotic structures. The
kinematically complete results are presented as Dalitz plots as well as
projections on given neutron and -energy. The distributions are
discussed and in most cases found to agree with available experimental data.Comment: 12 pages, 10 figures. To appear in Physical Review
Archimedean-type force in a cosmic dark fluid: II. Qualitative and numerical study of a multistage Universe expansion
In this (second) part of the work we present the results of numerical and
qualitative analysis, based on a new model of the Archimedean-type interaction
between dark matter and dark energy. The Archimedean-type force is linear in
the four-gradient of the dark energy pressure and plays a role of
self-regulator of the energy redistribution in a cosmic dark fluid. Because of
the Archimedean-type interaction the cosmological evolution is shown to have a
multistage character. Depending on the choice of the values of the model
guiding parameters,the Universe's expansion is shown to be perpetually
accelerated, periodic or quasiperiodic with finite number of
deceleration/acceleration epochs. We distinguished the models, which can be
definitely characterized by the inflation in the early Universe, by the
late-time accelerated expansion and nonsingular behavior in intermediate
epochs, and classified them with respect to a number of transition points.
Transition points appear, when the acceleration parameter changes the sign,
providing the natural partition of the Universe's history into epochs of
accelerated and decelerated expansion. The strategy and results of numerical
calculations are advocated by the qualitative analysis of the instantaneous
phase portraits of the dynamic system associated with the key equation for the
dark energy pressure evolution.Comment: 15 pages, 12 figures, Part II, typos corrected, Fig.4 replaced,
references correcte
Archimedean-type force in a cosmic dark fluid. III. Big rip, little rip, and cyclic solutions
We analyze the late-time evolution of the Universe in the framework of the self-consistent model, in which dark matter is influenced by the Archimedean-type force proportional to the four-gradient of the dark energy pressure. Dark energy is considered as a fluid with the equation of state of the relaxation type, which takes into account a retardation of the dark energy response to the Universe's accelerated expansion. Dark matter is guided by the Archimedean-type force, which redistributes the total energy of the dark fluid between its two constituents, dark energy and dark matter, in the course of the Universe's accelerated expansion. We focus on the constraints for the dark energy relaxation time parameter, for the dark energy equation of state parameter, and for the Archimedean-type coupling constants, which guarantee big rip avoidance. In particular, we show that the Archimedean-type coupling protects the Universe from the big rip scenario with asymptotically infinite negative dark energy pressure, and that the little rip is the fate of the Universe with the Archimedean-type interaction inside the dark fluid. © 2013 American Physical Society
Long-term variability of the optical spectra of NGC 4151: II. Evolution of the broad Ha and Hb emission-line profiles
Results of the long-term (11 years, from 1996 to 2006) H and H
line variations of the active galactic nucleus of NGC 4151 are presented. High
quality spectra (S/N>50 and R~8A) of H and H were investigated.
We analyzed line profile variations during monitoring period. Comparing the
line profiles of H and H, we studied different details (bumps,
absorption features) in the line profiles. The variations of the different
H and H line profile segments have been investigated. Also, we
analyzed the Balmer decrement for whole line and for line segments. We found
that the line profiles were strongly changing during the monitoring period,
showing blue and red asymmetries. This indicates a complex BLR geometry of NGC
4151 with, at least, three kinematically distinct regions: one that contributes
to the blue line wing, one to the line core and one to the red line wing. Such
variation can be caused by an accelerating outflow starting very close to the
black hole, where the red part may come from the region {closer to the black
hole than the blue part, which is coming} from the region having the highest
outflow velocities. Taking into account the fact that the BLR of NGC 4151 has a
complex geometry (probably affected by an outflow) and that a portion of the
broad line emission seems to have not a pure photoionization origin, one can
ask the question whether the study of the BLR by reverberation mapping may be
valid in the case of this galaxy.Comment: 24 pages, 18 figures, accepted for publications in A&
Variations of social psychology of Russian society in last 100 years
© 2015 IEEE.The study compares the dynamics of a number of important socio-demographic parameters with the frequency of the use of keywords for Russian society. We have shown that the frequency of words typical for the patriarchal way of life of Russian society in the 19th century decreases with the reduction of rural population. The paper discusses the interaction of moral values of society, its state ideology and environmental changes. Similar studies were carried out earlier for the English and Chinese languages. Our results confirm the findings of these studies partially. We also have considered the connection of these processes with the frequency of the use of emotive language. Google Books Ngram was used as a source of lexical data
Two-proton events in the 17F(p,2p)16O reaction
In a recent experimental study (Gomez del Campo et al, PRL 86, 43 (2001)) of
the reaction 17F(p,2p)16O, two-proton events were measured from excitations
near a 1-, E*=6.15 MeV state in 18Ne. We calculate by means of R-matrix theory
the resonant two-proton production cross section and branching ratios. We
conclude that it is unlikely that two-proton production via population of the
1- state is sufficient to explain the observed two-proton events. Alternative
sources of such events are discussed.Comment: 4 pages, 4 figures. Resubmission to Physical Review C (first received
6 March 2001
- …