795 research outputs found
Magnetic Moment of The Pentaquark State
We have calculated the magnetic moment of the recently observed
pentaquark in the framework of the light cone QCD sum rules using the photon
distribution amplitudes. We find that ,
which is quite small. We also compare our result with predictions of other
groups.Comment: 1 eps figure, 13 page
Spin in relativistic quantum theory
We discuss the role of spin in Poincar\'e invariant formulations of quantum
mechanics.Comment: 54 page
Pair excitations and the mean field approximation of interacting Bosons, I
In our previous work \cite{GMM1},\cite{GMM2} we introduced a correction to
the mean field approximation of interacting Bosons. This correction describes
the evolution of pairs of particles that leave the condensate and subsequently
evolve on a background formed by the condensate. In \cite{GMM2} we carried out
the analysis assuming that the interactions are independent of the number of
particles . Here we consider the case of stronger interactions. We offer a
new transparent derivation for the evolution of pair excitations. Indeed, we
obtain a pair of linear equations describing their evolution. Furthermore, we
obtain apriory estimates independent of the number of particles and use these
to compare the exact with the approximate dynamics
INSIG1 influences obesity-related hypertriglyceridemia in humans
In our analysis of a quantitative trait locus (QTL) for plasma triglyceride (TG) levels [logarithm of odds (LOD) = 3.7] on human chromosome 7q36, we examined 29 single nucleotide polymorphisms (SNPs) across INSIG1, a biological candidate gene in the region. Insulin-induced genes (INSIGs) are feedback mediators of cholesterol and fatty acid synthesis in animals, but their role in human lipid regulation is unclear. In our cohort, the INSIG1 promoter SNP rs2721 was associated with TG levels (P = 2 × 10−3 in 1,560 individuals of the original linkage cohort, P = 8 × 10−4 in 920 unrelated individuals of the replication cohort, combined P = 9.9 × 10−6). Individuals homozygous for the T allele had 9% higher TG levels and 2-fold lower expression of INSIG1 in surgical liver biopsy samples when compared with individuals homozygous for the G allele. Also, the T allele showed additional binding of nuclear proteins from HepG2 liver cells in gel shift assays. Finally, the variant rs7566605 in INSIG2, the only homolog of INSIG1, enhances the effect of rs2721 (P = 0.00117). The variant rs2721 alone explains 5.4% of the observed linkage in our cohort, suggesting that additional, yet-undiscovered genes and sequence variants in the QTL interval also contribute to alterations in TG levels in humans
Identifying topological edge states in 2D optical lattices using light scattering
We recently proposed in a Letter [Physical Review Letters 108 255303] a novel
scheme to detect topological edge states in an optical lattice, based on a
generalization of Bragg spectroscopy. The scope of the present article is to
provide a more detailed and pedagogical description of the system - the
Hofstadter optical lattice - and probing method. We first show the existence of
topological edge states, in an ultra-cold gas trapped in a 2D optical lattice
and subjected to a synthetic magnetic field. The remarkable robustness of the
edge states is verified for a variety of external confining potentials. Then,
we describe a specific laser probe, made from two lasers in Laguerre-Gaussian
modes, which captures unambiguous signatures of these edge states. In
particular, the resulting Bragg spectra provide the dispersion relation of the
edge states, establishing their chiral nature. In order to make the Bragg
signal experimentally detectable, we introduce a "shelving method", which
simultaneously transfers angular momentum and changes the internal atomic
state. This scheme allows to directly visualize the selected edge states on a
dark background, offering an instructive view on topological insulating phases,
not accessible in solid-state experiments.Comment: 17 pages, 10 figures. Revised and extended version, to appear in EJP
Special Topic for the special issue on "Novel Quantum Phases and Mesoscopic
Physics in Quantum Gases". Extended version of arXiv:1203.124
How Does Pubertal Development Impact Caregiver-Adolescent Communication About Sex in Rural, African American Families? An Examination of Mediation Effects
This study examined the relationship between pubertal development and type of caregiver-adolescent communication about sex (CACS) among 441 African American caregivers participating in an intervention trial in rural North Carolina. We assessed CACS about general sexual health topics and positive aspects of sexuality. Caregivers’ attitudes and self-efficacy for CACS, and open communication style were examined as potential mediators. Caregivers engaged in low levels of communication about sex regardless of type. Among caregivers of males, pubertal development was associated with greater communication about general sexual health, which was mediated by self-efficacy for CACS. Among caregivers of females, pubertal development was associated with less communication about general and positive sexual health topics; however, there were no mediating factors. These findings highlight the predictors of CACS among young men and women after pubertal onset. Age appropriate, practical guidance for initiating CACS may be critical for ensuring caregiver talk about sex
Origin of Life
The evolution of life has been a big enigma despite rapid advancements in the
fields of biochemistry, astrobiology, and astrophysics in recent years. The
answer to this puzzle has been as mind-boggling as the riddle relating to
evolution of Universe itself. Despite the fact that panspermia has gained
considerable support as a viable explanation for origin of life on the Earth
and elsewhere in the Universe, the issue remains far from a tangible solution.
This paper examines the various prevailing hypotheses regarding origin of life
like abiogenesis, RNA World, Iron-sulphur World, and panspermia; and concludes
that delivery of life-bearing organic molecules by the comets in the early
epoch of the Earth alone possibly was not responsible for kick-starting the
process of evolution of life on our planet.Comment: 32 pages, 8 figures,invited review article, minor additio
A unified Witten-Reshetikhin-Turaev invariant for integral homology spheres
We construct an invariant J_M of integral homology spheres M with values in a
completion \hat{Z[q]} of the polynomial ring Z[q] such that the evaluation at
each root of unity \zeta gives the the SU(2) Witten-Reshetikhin-Turaev
invariant \tau_\zeta(M) of M at \zeta. Thus J_M unifies all the SU(2)
Witten-Reshetikhin-Turaev invariants of M. As a consequence, \tau_\zeta(M) is
an algebraic integer. Moreover, it follows that \tau_\zeta(M) as a function on
\zeta behaves like an ``analytic function'' defined on the set of roots of
unity. That is, the \tau_\zeta(M) for all roots of unity are determined by a
"Taylor expansion" at any root of unity, and also by the values at infinitely
many roots of unity of prime power orders. In particular, \tau_\zeta(M) for all
roots of unity are determined by the Ohtsuki series, which can be regarded as
the Taylor expansion at q=1.Comment: 66 pages, 8 figure
Competing Orders in Coupled Luttinger Liquids
We consider the problem of two coupled Luttinger liquids both at half filling
and at low doping levels, to investigate the problem of competing orders in
quasi-one-dimensional strongly correlated systems. We use bosonization and
renormalization group equations to investigate the phase diagrams, to determine
the allowed phases and to establish approximate boundaries among them. Because
of the chiral translation and reflection symmetry in the charge mode away from
half filling, orders of charge density wave (CDW) and spin-Peierls (SP)
diagonal current (DC) and -density wave (DDW) form two doublets and thus can
be at most quasi-long range ordered. At half-filling, umklapp terms break this
symmetry down to a discrete group and thus Ising-type ordered phases appear as
a result of spontaneous breaking of the residual symmetries. Quantum disordered
Haldane phases are also found, with finite amplitudes of pairing orders and
triplet counterparts of CDW, SP, DC and DDW. Relations with recent numerical
results and implications to similar problems in two dimensions are discussed.Comment: 16 pages, 5 figures, 4 tables. Revised manuscript; a misprint in Eq.
B3 has been corrected. The paper is already in print in PR
Computational Nuclear Physics and Post Hartree-Fock Methods
We present a computational approach to infinite nuclear matter employing
Hartree-Fock theory, many-body perturbation theory and coupled cluster theory.
These lectures are closely linked with those of chapters 9, 10 and 11 and serve
as input for the correlation functions employed in Monte Carlo calculations in
chapter 9, the in-medium similarity renormalization group theory of dense
fermionic systems of chapter 10 and the Green's function approach in chapter
11. We provide extensive code examples and benchmark calculations, allowing
thereby an eventual reader to start writing her/his own codes. We start with an
object-oriented serial code and end with discussions on strategies for porting
the code to present and planned high-performance computing facilities.Comment: 82 pages, to appear in Lecture Notes in Physics (Springer), "An
advanced course in computational nuclear physics: Bridging the scales from
quarks to neutron stars", M. Hjorth-Jensen, M. P. Lombardo, U. van Kolck,
Editor
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