2,064 research outputs found
Response function beyond mean field of neutron-rich nuclei
The damping of single-particle and collective motion in exotic isotopes is a
new topic and its study may shed light on basic problems of nuclear dynamics.
For instance, it is known that nuclear structure calculations are not able, as
a rule, to account completely for the empirical single-particle damping. In
this contribution, we present calculations of the single-particle self-energy
in the case of the neutron-rich light nucleus O, by taking proper care
of the continuum, and we show that there are important differences with the
case of nuclei along the valley of stability.Comment: 9 pages, 4 figures. To appear in: Proceedings of the Topical
Conference on Giant Resonances, Varenna, May 11-16, 1997 (Nucl. Phys. A, to
be published
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The impact of aerosol hygroscopic growth on the single-scattering albedo and its application on the NO2 photolysis rate coefficient
Hygroscopic growth of aerosol particles can significantly affect their single-scattering albedo (ω), and consequently alters the aerosol effect on tropospheric photochemistry. In this study, the impact of aerosol hygroscopic growth on ω and its application to the NO2 photolysis rate coefficient (JNO2) are investigated for a typical aerosol particle population in the North China Plain (NCP). The variations of aerosol optical properties with relative humidity (RH) are calculated using a Mie theory aerosol optical model, on the basis of field measurements of number–size distribution and hygroscopic growth factor (at RH values above 90%) from the 2009 HaChi (Haze in China) project. Results demonstrate that ambient ω has pronouncedly different diurnal patterns from ω measured at dry state, and is highly sensitive to the ambient RHs. Ambient ω in the NCP can be described by a dry state ω value of 0.863, increasing with the RH following a characteristic RH dependence curve. A Monte Carlo simulation shows that the uncertainty of ω from the propagation of uncertainties in the input parameters decreases from 0.03 (at dry state) to 0.015 (RHs > 90%). The impact of hygroscopic growth on ω is further applied in the calculation of the radiative transfer process. Hygroscopic growth of the studied aerosol particle population generally inhibits the photolysis of NO2 at the ground level, whereas accelerates it above the moist planetary boundary layer. Compared with dry state, the calculated JNO2 at RH of 98% at the height of 1 km increases by 30.4%, because of the enhancement of ultraviolet radiation by the humidified scattering-dominant aerosol particles. The increase of JNO2 due to the aerosol hygroscopic growth above the upper boundary layer may affect the tropospheric photochemical processes and this needs to be taken into account in the atmospheric chemical models
Spin-orbit splitting and the tensor component of the Skyrme interaction
We study the role of the tensor term of the Skyrme effective interactions on
the spin-orbit splittings in the N=82 isotones and Z=50 isotopes. The different
role of the triplet-even and triplet-odd tensor forces is pointed out by
analyzing the spin-orbit splittings in these nuclei. The experimental isospin
dependence of these splittings cannot be described by Hartree-Fock calculations
employing the usual Skyrme parametrizations, but is very well accounted for
when the tensor interaction is introduced. The capability of the Skyrme forces
to reproduce binding energies and charge radii in heavy nuclei is not destroyed
by the introduction of the tensor term. Finally, we also discuss the effect of
the tensor force on the centroid of the Gamow-Teller states.Comment: Submitted to Phys. Lett.
Supersymmetry for Fermion Masses
It is proposed that supersymmetry (SUSY) maybe used to understand fermion
mass hierarchies. A family symmetry Z_{3L} is introduced, which is the cyclic
symmetry among the three generation SU(2) doublets. SUSY breaks at a high
energy scale ~ 10^{11} GeV. The electroweak energy scale ~ 100 GeV is
unnaturally small. No additional global symmetry, like the R-parity, is
imposed. The Yukawa couplings and R-parity violating couplings all take their
natural values which are about (10^0-10^{-2}). Under the family symmetry, only
the third generation charged fermions get their masses. This family symmetry is
broken in the soft SUSY breaking terms which result in a hierarchical pattern
of the fermion masses. It turns out that for the charged leptons, the tau mass
is from the Higgs vacuum expectation value (VEV) and the sneutrino VEVs, the
muon mass is due to the sneutrino VEVs, and the electron gains its mass due to
both Z_{3L} and SUSY breaking. The large neutrino mixing are produced with
neutralinos playing the partial role of right-handed neutrinos. |V_{e3}| which
is for nu_e-nu_{tau} mixing is expected to be about 0.1. For the quarks, the
third generation masses are from the Higgs VEVs, the second generation masses
are from quantum corrections, and the down quark mass due to the sneutrino
VEVs. It explains m_c/m_s, m_s/m_e, m_d > m_u and so on. Other aspects of the
model are discussed.Comment: 25 pages, 3 figures, revtex4; neutrino oscillation and many
discussions added, smallness of the electron mass due to supersymmetry
pointed out; v3: numerical errors correcte
On localization in holomorphic equivariant cohomology
We prove a localization formula for a "holomorphic equivariant cohomology"
attached to the Atiyah algebroid of an equivariant holomorphic vector bundle.
This generalizes Feng-Ma, Carrell-Liebermann, Baum-Bott and K. Liu's
localization formulas.Comment: 16 pages. Completely rewritten, new title. v3: Minor changes in the
exposition. v4: final version to appear in Centr. Eur. J. Mat
Parity-violating neutron spin rotation in hydrogen and deuterium
We calculate the (parity-violating) spin rotation angle of a polarized
neutron beam through hydrogen and deuterium targets, using pionless effective
field theory up to next-to-leading order. Our result is part of a program to
obtain the five leading independent low-energy parameters that characterize
hadronic parity-violation from few-body observables in one systematic and
consistent framework. The two spin-rotation angles provide independent
constraints on these parameters. Using naive dimensional analysis to estimate
the typical size of the couplings, we expect the signal for standard target
densities to be 10^-7 to 10^-6 rad/m for both hydrogen and deuterium targets.
We find no indication that the nd observable is enhanced compared to the np
one. All results are properly renormalized. An estimate of the numerical and
systematic uncertainties of our calculations indicates excellent convergence.
An appendix contains the relevant partial-wave projectors of the three-nucleon
system.Comment: 44 pages, 17 figures; minor corrections; to be published in EPJ
Elliptic flow at SPS and RHIC: from kinetic transport to hydrodynamics
Anisotropic transverse flow is studied in Pb+Pb and Au+Au collisions at SPS
and RHIC energies. The centrality and transverse momentum dependence at
midrapidity of the elliptic flow coefficient v_2 is calculated in the
hydrodynamic and low density limits. Hydrodynamics is found to agree well with
the RHIC data for semicentral collisions up to transverse momenta of 1-1.5
GeV/c, but it considerably overestimates the measured elliptic flow at SPS
energies. The low density limit LDL is inconsistent with the measured magnitude
of v_2 at RHIC energies and with the shape of its p_t-dependence at both RHIC
and SPS energies. The success of the hydrodynamic model points to very rapid
thermalization in Au+Au collisions at RHIC and provides a serious challenge for
kinetic approaches based on classical scattering of on-shell particles.Comment: 7 pages incl. 5 figures; submitted to Physics Letters B; Ref. 4 and a
few typos corrected; no changes in content
Interaction of suppressor of cytokine signalling 3 with cavin-1 links SOCS3 function and cavin-1 stability
YesEffective suppression of JAK–STAT signalling by the inducible inhibitor “suppressor of
cytokine signalling 3” (SOCS3) is essential for limiting signalling from cytokine receptors.
Here we show that cavin-1, a component of caveolae, is a functionally significant SOCS3-
interacting protein. Biochemical and confocal imaging demonstrate that SOCS3 localisation to
the plasma membrane requires cavin-1. SOCS3 is also critical for cavin-1 stabilisation, such
that deletion of SOCS3 reduces the expression of cavin-1 and caveolin-1 proteins, thereby
reducing caveola abundance in endothelial cells. Moreover, the interaction of cavin-1 and
SOCS3 is essential for SOCS3 function, as loss of cavin-1 enhances cytokine-stimulated
STAT3 phosphorylation and abolishes SOCS3-dependent inhibition of IL-6 signalling by cyclic
AMP. Together, these findings reveal a new functionally important mechanism linking
SOCS3-mediated inhibition of cytokine signalling to localisation at the plasma membrane via
interaction with and stabilisation of cavin-1.This work was supported by project grants to T.M.P. from the Chief Scientist Office (ETM/226), British Heart Foundation (PG12/1/ 29276, PG 14/32/30812), and a National Health Service Greater Glasgow and Clyde Research Endowment Fund (2011REFCH08). P.F.P. was supported by the National Institutes of Health grant DK097708. J.J.L.W. was supported by a doctoral training studentship from the Biotechnology and Biological Sciences Research Council Doctoral Training Programme in Biochemistry and Molecular Biology at the University of Glasgow (BB/F016735/1). N.A. was supported by a Saudi Government PhD Scholarship. This work was also supported in part by equipment grants to T.M.P. from Diabetes UK (BDA 11/0004309) and Alzheimer’s Research UK (ARUK-EG2016A-3)
Supergravity and the jet quenching parameter in the presence of R-charge densities
Following a recent proposal, we employ the AdS/CFT correspondence to compute
the jet quenching parameter for N=4 Yang-Mills theory at nonzero R-charge
densities. Using as dual supergravity backgrounds non-extremal rotating branes,
we find that the presence of the R-charges generically enhances the jet
quenching phenomenon. However, at fixed temperature, this enhancement might or
might not be a monotonically increasing function of the R-charge density and
depends on the number of independent angular momenta describing the solution.
We perform our analysis for the canonical as well as for the grand canonical
ensemble which give qualitatively similar results.Comment: 18 pages, 2 figures; v3: clarifying comments added, references added,
version to appear in JHE
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