9,573 research outputs found
The multilevel pairing Hamiltonian versus the degenerate case
We study the pairing Hamiltonian in a set of non degenerate levels. First, we
review in the path integral framework the spontaneous breaking of the U(1)
symmetry occurring in such a system for the degenerate situation. Then the
behaviors with the coupling constant of the ground state energy in the
multilevel and in the degenerate case are compared. Next we discuss, in the
multilevel case, an exact strong coupling expansion for the ground state energy
which introduces the moments of the single particle level distribution. The
domain of validity of the expansion, which is known in the macroscopic limit,
is explored for finite systems and its implications for the energy of the
latter is discussed. Finally the seniority and Gaudin excitations of the
pairing Hamiltonian are addressed and shown to display the same gap in leading
order.Comment: 20 pages, 4 figure
On the analytic solution of the pairing problem: one pair in many levels
We search for approximate, but analytic solutions of the pairing problem for
one pair of nucleons in many levels of a potential well. For the collective
energy a general formula, independent of the details of the single particle
spectrum, is given in both the strong and weak coupling regimes. Next the
displacements of the solutions trapped in between the single particle levels
with respect to the unperturbed energies are explored: their dependence upon a
suitably defined quantum number is found to undergo a transition between two
different regimes.Comment: 30 pages, AMS Latex, 8 figures. Submitted to Phys. Rev.
Are there hadronic bound states above the QCD transition temperature?
Recent lattice QCD calculations, at physical pion masses and small lattice
spacings that approach the continuum limit, have revealed that non-diagonal
quark correlators above the critical temperature are finite up to about 2
. Since the transition from hadronic to free partonic degrees of freedom
is merely an analytic cross-over, it is likely that, in the temperature regime
between 1-2 , quark and gluon quasiparticles and pre-hadronic bound states
can coexist. The correlator values, in comparison to PNJL model calculations
beyond mean-field, indicate that at least part of the mixed phase resides in
color-neutral bound states. A similar effect was postulated for the in-medium
fragmentation process, i.e. for partons which do not thermalize with the system
and thus constitute the non-equilibrium component of the particle emission
spectrum from a deconfined plasma phase. Here, for the first time we
investigate the likelihood of forming bound states also in the equilibrated,
parton dominated phase above which is described by lattice QCD.Comment: 15 pages, 4 Figure
Indicators of Early Childhood Disaster Risk: Using Data for Strategic Improvements in Emergency Preparedness
This Power Point presentation is a tool for ranking the vulnerability of the early care and education sector to disasters
Effect of ELF e.m. fields on metalloprotein redox-active sites
The peculiarity of the distribution and geometry of metallic ions in enzymes
pushed us to set the hypothesis that metallic ions in active-site act like tiny
antennas able to pick up very feeble e.m. signals. Enzymatic activity of Cu2+,
Zn2+ Superoxide Dismutase (SOD1) and Fe2+ Xanthine Oxidase (XO) has been
studied, following in vitro generation and removal of free radicals. We
observed that Superoxide radicals generation by XO is increased by a weak field
having the Larmor frequency fL of Fe2+ while the SOD1 kinetics is sensibly
reduced by exposure to a weak field having the frequency fL of Cu2+ ion.Comment: 18 pages, 4 figure
Superscaling of non-quasielastic electron-nucleus scattering
The present study is focused on the superscaling behavior of electron-nucleus
cross sections in the region lying above the quasielastic peak, especially the
region dominated by electroexcitation of the Delta. Non-quasielastic cross
sections are obtained from all available high-quality data for Carbon 12 by
subtracting effective quasielastic cross sections based on the superscaling
hypothesis. These residuals are then compared with results obtained within a
scaling-based extension of the relativistic Fermi gas model, including an
investigation of violations of scaling of the first kind in the region above
the quasielastic peak. A way potentially to isolate effects related to
meson-exchange currents by subtracting both impulsive quasielastic and
impulsive inelastic contributions from the experimental cross sections is also
presented.Comment: RevTeX, 34 pages including 11 figure
Meson-exchange Currents and Quasielastic Neutrino Cross Sections
We illustrate and discuss the role of meson-exchange currents in quasielastic
neutrino-nucleus scattering induced by charged currents, comparing the results
with the recent MiniBooNE data for differential and integrated cross sections.Comment: 9 pages, 8 figures; Proceedings of the 30th International Workshop on
Nuclear Theory IWNT30, Rila Mountains, Bulgaria, June 27 - July 2, 201
Bosonization and even Grassmann variables
A new approach to bosonization in relativistic field theories and many-body
systems, based on the use of fermionic composites as integration variables in
the Berezin integral defining the partition function of the system, is tested.
The method is applied to the study of a simplified version of the BCS model.Comment: 20 pages, LaTe
Effects of maintenance lithium treatment on serum parathyroid hormone and calcium levels: a retrospective longitudinal naturalistic study
Objective: The aim of this retrospective longitudinal naturalistic study was to evaluate the effects of maintenance lithium treatment on parathyroid hormone (PTH) and calcium levels. Methods: A retrospective longitudinal naturalistic study design was used. Data were collected from the database of a tertiary psychiatric center covering the years 2010\u20132014. Included were bipolar patients who had never been exposed to lithium and had lithium started, and who had PTH, and total and ionized calcium levels available before and during lithium treatment. Paired t-tests were used to analyze changes in PTH and calcium levels. Linear regressions were per- formed, with mean lithium level and duration of lithium exposure as independent variables and change in PTH levels as dependent variable.
Results: A total 31 patients were included. The mean duration of lithium treatment was 18.6\ub111.4 months. PTH levels significantly increased during lithium treatment (+13.55\ub114.20 pg/mL); the rate of hyperparathyroidism was 12.9%. Neither total nor ionized calcium increased from baseline to follow-up; none of our patients developed hypercalcemia. Linear regressions analyses did not show an effect of duration of lithium exposure or mean lithium level on PTH levels. Conclusion: Lithium-associated stimulation of parathyroid function is more common than assumed to date. Among parameters to be evaluated prior to lithium implementation, calcium and PTH should be added
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