629,409 research outputs found
Cranked Relativistic Hartree-Bogoliubov Theory: Formalism and Application to the Superdeformed Bands in the region
Cranked Relativistic Hartree-Bogoliubov theory without and with approximate
particle number projection by means of the Lipkin-Nogami method is presented in
detail as an extension of Relativistic Mean Field theory with pairing
correlations to the rotating frame. Pairing correlations are taken into account
by a finite range two-body force of Gogny type. The applicability of this
theory to the description of rotating nuclei is studied in detail on the
example of superdeformed bands in even-even nuclei of the mass
region. Different aspects such as the importance of pairing and particle number
projection, the dependence of the results on the parametrization of the RMF
Lagrangian and Gogny force etc. are investigated in detail. It is shown that
without any adjustment of new parameters the best description of experimental
data is obtained by using the well established parameter sets NL1 for the
Lagrangian and D1S for the pairing force. Contrary to previous studies at spin
zero it is found that the increase of the strength of the Gogny force is not
necessary in the framework of Relativistic Hartree-Bogoliubov theory provided
that particle number projection is performed.Comment: 34 pages, 24 figures, 3 tables, uses Revtex and epsf.sty, submitted
to Nuclear Physics
Assessing individual differences in genome-wide gene expression in human whole blood: reliability over four hours and stability over 10 months.
Studying the causes and correlates of natural variation in gene expression in healthy populations assumes that individual differences in gene expression can be reliably and stably assessed across time. However, this is yet to be established. We examined 4-hour test-retest reliability and 10 month test-retest stability of individual differences in gene expression in ten 12-year-old children. Blood was collected on four occasions: 10 a.m. and 2 p.m. on Day 1 and 10 months later at 10 a.m. and 2 p.m. Total RNA was hybridized to Affymetrix-U133 plus 2.0 arrays. For each probeset, the correlation across individuals between 10 a.m. and 2 p.m. on Day 1 estimates test-retest reliability. We identified 3,414 variable and abundantly expressed probesets whose 4-hour test-retest reliability exceeded .70, a conventionally accepted level of reliability, which we had 80% power to detect. Of the 3,414 reliable probesets, 1,752 were also significantly reliable 10 months later. We assessed the long-term stability of individual differences in gene expression by correlating the average expression level for each probe-set across the two 4-hour assessments on Day 1 with the average level of each probe-set across the two 4-hour assessments 10 months later. 1,291 (73.7%) of the 1,752 probe-sets that reliably detected individual differences across 4 hours on two occasions, 10 months apart, also stably detected individual differences across 10 months. Heritability, as estimated from the MZ twin intraclass correlations, is twice as high for the 1,752 reliable probesets versus all present probesets on the array (0.68 vs 0.34), and is even higher (0.76) for the 1,291 reliable probesets that are also stable across 10 months. The 1,291 probesets that reliably detect individual differences from a single peripheral blood collection and stably detect individual differences over 10 months are promising targets for research on the causes (e.g., eQTLs) and correlates (e.g., psychopathology) of individual differences in gene expression
Study of Superdeformation in Non-rotating States using the Skyrme-Hartree-Fock Method
The superdeformation (SD) in non-rotating states is studied with the HF+BCS
method using the Skyrme interaction. In applying the BCS theory, the seniority
pairing force is employed, of which strengths are determined in order to
reproduce the empirical pairing gap formula, MeV,
through a smooth level density obtained in the Thomas-Fermi approximation.
Properties of superdeformation are investigated by calculating potential energy
surfaces (PES) for various sets of the pairing force strengths and the Skyrme
force parameter for 194Hg and 236,238U. The best results are obtained using
both the SkM* force and the pairing force strength determined in this paper. By
making use of this set of forces, a systematic calculation of SD states is
carried out extensively for even-even nuclei for 20 <= Z <= 82. From our
calculation, the barriers preventing the decay into the normally deformed
states are about twice as high as those predicted by Krieger et al., who used
the same Skyrme interaction but a pairing force stronger than ours. The
differences of the present results from the Nilsson-Strutinsky calculation are
analyzed.Comment: 19 pages in LaTex, 11 Postscript figure
Barrier penetration and rotational damping of thermally excited superdeformed nuclei
We construct a microscopic model of thermally excited superdeformed states
that describes both the barrier penetration mechanism, leading to the decay-out
transitions to normal deformed states, and the rotational damping causing
fragmentation of rotational E2 transitions. We describe the barrier penetration
by means of a tunneling path in the two-dimensional deformation energy surface,
which is calculated with the cranked Nilsson-Strutinsky model. The individual
excited superdeformed states and associated E2 transition strengths are
calculated by the shell model diagonalization of the many-particle many-hole
excitations interacting with the delta-type residual two-body force. The effect
of the decay-out on the excited superdeformed states are discussed in detail
for Dy, Eu and Hg.Comment: 33pages, 32 figures, submitted to Nucl.Phys.
Onset of Rotational Damping in Superdeformed Nuclei
We discuss damping of the collective rotational motion in
superdeformed nuclei by means of a shell model combining the cranked Nilsson
mean-filed and the surface-delta two-body residual force. It is shown that,
because of the shell structure associated with the superdeformed mean-field,
onset energy of the rotational damping becomes MeV above yrast
line, which is much higher than in normal deformed nuclei. The mechanism of the
shell structure effect is investigated through detailed analysis of level
densities in superdeformed nuclei. It is predicted the onset of damping varies
in different supedeformed nuclei along with variation in the single-particle
structure at the Fermi surface.Comment: 24 pages, latex, 14 figures (compressed and uuencoded
Rotating nuclei at extreme conditions: Cranked Relativistic Mean Field Description
The cranked relativistic mean field (CRMF) theory is applied for the
description of superdeformed (SD) rotational bands observed in Ho. The
question of the structure of the so-called SD band in Er is also
addressed and a brief overview of applications of CRMF theory to the
description of rotating nuclei at extreme conditions is presented.Comment: 4 pages, 1 PostScript figure, LaTex, uses 'espcrc1.sty', to be
published in Proceedings of International Nuclear Physics Conference, Paris,
1998 which will appear in Nuclear Physic
The Vector-like Twin Higgs
We present a version of the twin Higgs mechanism with vector-like top
partners. In this setup all gauge anomalies automatically cancel, even without
twin leptons. The matter content of the most minimal twin sector is therefore
just two twin tops and one twin bottom. The LHC phenomenology, illustrated with
two example models, is dominated by twin glueball decays, possibly in
association with Higgs bosons. We further construct an explicit
four-dimensional UV completion and discuss a variety of UV completions relevant
for both vector-like and fraternal twin Higgs models.Comment: 39 pages; v2 published versio
Polarization Effects in Superdeformed Nuclei
A detailed theoretical investigation of polarization effects in superdeformed
nuclei is performed. In the pure harmonic oscillator potential it is shown that
when one particle (or hole) with the mass single-particle quadrupole moment
q_{nu} is added to a superdeformed core, the change of the electric quadrupole
moment can be parameterized as q_{eff}=e(bq_{nu}+a), and analytical expressions
are derived for the two parameters, and . Simple numerical expressions
for q_{eff}(q_\nu}) are obtained in the more realistic modified oscillator
model. It is also shown that quadrupole moments of nuclei with up to 10
particles removed from the superdeformed core of 152Dy can be well described by
simply subtracting effective quadrupole moments of the active single-particle
states from the quadrupole moment of the core. Tools are given for estimating
the quadrupole moment for possible configurations in the superdeformed A
150-region.Comment: 28 pages including 9 figure
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