6,974 research outputs found
Binary Decay of Light Nuclear Systems
A review of the characteristic features found in fully energy-damped,
binarydecay yields from light heavy-ion reactions with is presented. The different aspects of these yields that
have been used to support models of compound-nucleus (CN) fission and
deep-inelastic dinucleus orbiting are highlighted. Cross section calculations
based on the statistical phase space at different stages of the reaction are
presented and compared to the experimental results. Although the statistical
models are found to reproduce most of the observed experimental behaviors, an
additional reaction component corresponding to a heavy-ion resonance or
orbiting mechanism is also evident in certain systems. The system dependence of
this second component is discussed. The extent to which the binary yields in
very light systems can be viewed as resulting from a
fusion-fission mechanism is explored. A number of unresolved questions, such as
whether the different observed behaviors reflect characteristically different
reaction times, are discussed.Comment: 79 pages REVTeX file, 39 ps Figures included - to be publihed in
Physics Report
Stern-Gerlach Entanglement in Spinor Bose-Einstein Condensates
Entanglement of spin and position variables produced by spatially
inhomogeneous magnetic fields of Stern-Gerlach type acting on spinor
Bose-Einstein condensates may lead to interference effects at the level of
one-boson densities. A model is worked out for these effects which is amenable
to analytical calculation for gaussian shaped condensates. The resulting
interference effects are sensitive to the spin polarization properties of the
condensate.Comment: 9 pages, 2 figure
On the Issue of the \zeta Series Convergence and Loop Corrections in the Generation of Observable Primordial Non-Gaussianity in Slow-Roll Inflation. Part II: the Trispectrum
We calculate the trispectrum T_\zeta of the primordial curvature perturbation
\zeta, generated during a {\it slow-roll} inflationary epoch by considering a
two-field quadratic model of inflation with {\it canonical} kinetic terms. We
consider loop contributions as well as tree level terms, and show that it is
possible to attain very high, {\it including observable}, values for the level
of non-gaussianity \tau_{NL} if T_\zeta is dominated by the one-loop
contribution. Special attention is paid to the claim in JCAP {\bf 0902}, 017
(2009) [arXiv:0812.0807 [astro-ph]] that, in the model studied in this paper
and for the specific inflationary trajectory we choose, the quantum
fluctuations of the fields overwhelm the classical evolution. We argue that
such a claim actually does not apply to our model, although more research is
needed in order to understand the role of quantum diffusion. We also consider
the probability that an observer in an ensemble of realizations of the density
field sees a non-gaussian distribution. In that respect, we show that the
probability associated to the chosen inflationary trajectory is non-negligible.
Finally, the levels of non-gaussianity f_{NL} and \tau_{NL} in the bispectrum
B_\zeta and trispectrum T_\zeta of \zeta, respectively, are also studied for
the case in which \zeta is not generated during inflation.Comment: LaTex File, 27 pages, 8 figures. v2: Previous Section 2 has been
removed. Two new sections (3 and 4) discussing the classicality condition
given by Byrnes, Choi, and Hall, in JCAP 0902, 017 (2009), and the
probability that an observer sees a non-gaussian distribution have been
added. v3: Version accepted for publication in Physical Review
Violation of the Ikeda sum rule and the self-consistency in the renormalized quasiparticle random phase approximation and the nuclear double-beta decay
The effect of the inclusion of ground state correlations into the QRPA
equation of motion for the two-neutrino double beta () decay
is carefully analyzed. The resulting model, called renormalized QRPA (RQRPA),
does not collapse near the physical value of the nuclear force strength in the
particle-particle channel, as happens with the ordinary QRPA. Still, the
transition amplitude is only slightly less sensitive on
this parameter in the RQRPA than that in the plain QRPA. It is argued that this
fact reveals once more that the characteristic behaviour of the
transition amplitude within the QRPA is not an artifact of
the model, but a consequence of the partial restoration of the spin-isospin
symmetry. It is shown that the price paid for bypassing the collapse in
the RQRPA is the violation of the Ikeda sum rule.Comment: 16 pages, latex, 3 postscript figure
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