537 research outputs found
Covariant Quark Model for the Baryons
A family of simply solvable covariant quark models for the baryons is
presented. With optimal parameter choices the models reproduce the empirical
spectra of the baryons in all flavor sectors to an accuracy of a few percent.
Complete spectra are obtained for all states of the strange, charm and beauty
hyperons with . The magnetic moments and axial coupling constants of
the ground state baryons correspond to those of conventional quark models. We
construct current-density operators that are consistent with empirical nucleon
form factors at low and medium energies.Comment: 32pages, LateX, 3 figures(postscript
Magnetic moments of the 3/2 resonances and their quark spin structure
We discuss magnetic moments of the baryons based on an earlier model
for the baryon magnetic moments, allowing for flavor symmetry breaking in the
quark magnetic moments as well as a general quark spin structure. From our
earlier analysis of the nucleon-hyperon magnetic moments and the measured
values of the magnetic moments of and we predict the
other magnetic moments and deduce the spin structure of the resonance
particles. We find from experiment that the total spin polarization of the
decuplet baryons, , is considerably smaller than the
non-relativistic quark model value of 3, although the data is still not good
enough to give a precise determination.Comment: 13 pages, REVTeX, 2 figures, minor clarifying change
Magnetic Moments of the Baryon Decuplet in a Relativistic Quark Model
The magnetic moments of the baryon decuplet are calculated in a relativistic
constituent quark model using the light-front formalism. Of particular interest
are the magnetic moments of the and for which new
recent experimental measurements are available. Our calculation for the
magnetic moment ratio is in excellent agreement with
the experimental ratio, while our ratio is
slightly higher than the experimental ratio.Comment: 10 pages ReVTeX, SLAC-PUB-621
Parametric interactions in the organic salt 4-N,N-dimethylamino-4′-N′- methyl-stilbazolium tosylate at telecommunication wavelengths
Magnetic Moments of Decuplet Baryons in Light Cone QCD
We calculate the magnetic moments of decuplet baryons containing strange
quarks within the framework of light cone QCD sum rules taking into account the
SU(3) flavor symmetry breaking effects. It is obtained that magnetic moments of
the neutral \sso and \xis0 baryons are mainly determined by the SU(3)
breaking terms. A comparison of our results on the magnetic moments of the
decuplet baryons with the predictions of other approaches is presented.Comment: Latex, 20 pages, 6 figure
The Singularity Problem for Space-Times with Torsion
The problem of a rigorous theory of singularities in space-times with torsion
is addressed. We define geodesics as curves whose tangent vector moves by
parallel transport. This is different from what other authors have done,
because their definition of geodesics only involves the Christoffel connection,
though studying theories with torsion. We propose a preliminary definition of
singularities which is based on timelike or null geodesic incompleteness, even
though for theories with torsion the paths of particles are not geodesics. The
study of the geodesic equation for cosmological models with torsion shows that
the definition has a physical relevance. It can also be motivated, as done in
the literature, remarking that the causal structure of a space-time with
torsion does not get changed with respect to general relativity. We then prove
how to extend Hawking's singularity theorem without causality assumptions to
the space-time of the ECSK theory. This is achieved studying the generalized
Raychaudhuri equation in the ECSK theory, the conditions for the existence of
conjugate points and properties of maximal timelike geodesics. Hawking's
theorem can be generalized, provided the torsion tensor obeys some conditions.
Thus our result can also be interpreted as a no-singularity theorem if these
additional conditions are not satisfied. In other words, it turns out that the
occurrence of singularities in closed cosmological models based on the ECSK
theory is less generic than in general relativity. Our work is to be compared
with previous papers in the literature. There are some relevant differences,
because we rely on a different definition of geodesics, we keep the field
equations of the ECSK theory in their original form rather than casting them in
a form similar to general relativity with a modified energy momentum tensor,Comment: 17 pages, plain-tex, published in Nuovo Cimento B, volume 105, pages
75-90, year 199
Impaired oxidative stress response characterizes HUWE1-promoted X-linked intellectual disability.
Mutations in the HECT, UBA and WWE domain-containing 1 (HUWE1) E3 ubiquitin ligase cause neurodevelopmental disorder X-linked intellectual disability (XLID). HUWE1 regulates essential processes such as genome integrity maintenance. Alterations in the genome integrity and accumulation of mutations have been tightly associated with the onset of neurodevelopmental disorders. Though HUWE1 mutations are clearly implicated in XLID and HUWE1 regulatory functions well explored, currently much is unknown about the molecular basis of HUWE1-promoted XLID. Here we showed that the HUWE1 expression is altered and mutation frequency increased in three different XLID individual (HUWE1 p.R2981H, p.R4187C and HUWE1 duplication) cell lines. The effect was most prominent in HUWE1 p.R4187C XLID cells and was accompanied with decreased DNA repair capacity and hypersensitivity to oxidative stress. Analysis of HUWE1 substrates revealed XLID-specific down-regulation of oxidative stress response DNA polymerase (Pol) λ caused by hyperactive HUWE1 p.R4187C. The subsequent restoration of Polλ levels counteracted the oxidative hypersensitivity. The observed alterations in the genome integrity maintenance may be particularly relevant in the cortical progenitor zones of human brain, as suggested by HUWE1 immunofluorescence analysis of cerebral organoids. These results provide evidence that impairments of the fundamental cellular processes, like genome integrity maintenance, characterize HUWE1-promoted XLID
The Decuplet Revisited in PT
The paper deals with two issues. First, we explore the quantitiative
importance of higher multiplets for properties of the decuplet in
chiral perturbation theory. In particular, it is found that the lowest order
one--loop contributions from the Roper octet to the decuplet masses and
magnetic moments are substantial. The relevance of these results to the chiral
expansion in general is discussed. The exact values of the magnetic moments
depend upon delicate cancellations involving ill--determined coupling
constants. Second, we present new relations between the magnetic moments of the
decuplet that are independent of all couplings. They are exact at the
order of the chiral expansion used in this paper.Comment: 7 pages of double column revtex, no figure
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