4,477 research outputs found
Dileptons in a coarse-grained transport approach
We calculate dilepton spectra in heavy-ion collisions using a coarse-graining
approach to the simulation of the created medium with the UrQMD transport
model. This enables the use of dilepton-production rates evaluated in
equilibrium quantum-field theory at finite temperatures and chemical
potentials.Comment: 4 pages, 2 figures, contribution to the proceedings of "The 15th
International Conference on Strangeness in Quark Matter" (SQM 2015), 06-11
July in Dubna, Russi
Upper limits on the robustness of Turing models and other multiparametric dynamical systems
Traditional linear stability analysis based on matrix diagonalization is a
computationally intensive process for -dimensional systems of
differential equations, posing substantial limitations for the exploration of
Turing systems of pattern formation where an additional wave-number parameter
needs to be investigated. In this study, we introduce an efficient
technique that leverages Gershgorin's theorem to determine upper limits on
regions of parameter space and the wave number beyond which Turing
instabilities cannot occur. This method offers a streamlined avenue for
exploring the phase diagrams of other complex multiparametric models, such as
those found in systems biology
Measurement of the 187Re({\alpha},n)190Ir reaction cross section at sub-Coulomb energies using the Cologne Clover Counting Setup
Uncertainties in adopted models of particle+nucleus optical-model potentials
directly influence the accuracy in the theoretical predictions of reaction
rates as they are needed for reaction-network calculations in, for instance,
{\gamma}-process nucleosynthesis. The improvement of the {\alpha}+nucleus
optical-model potential is hampered by the lack of experimental data at
astrophysically relevant energies especially for heavier nuclei. Measuring the
Re187({\alpha},n)Ir190 reaction cross section at sub-Coulomb energies extends
the scarce experimental data available in this mass region and helps
understanding the energy dependence of the imaginary part of the
{\alpha}+nucleus optical-model potential at low energies. Applying the
activation method, after the irradiation of natural rhenium targets with
{\alpha}-particle energies of 12.4 to 14.1 MeV, the reaction yield and thus the
reaction cross section were determined via {\gamma}-ray spectroscopy by using
the Cologne Clover Counting Setup and the method of {\gamma}{\gamma}
coincidences. Cross-section values at five energies close to the
astrophysically relevant energy region were measured. Statistical model
calculations revealed discrepancies between the experimental values and
predictions based on widely used {\alpha}+nucleus optical-model potentials.
However, an excellent reproduction of the measured cross-section values could
be achieved from calculations based on the so-called Sauerwein-Rauscher
{\alpha}+nucleus optical-model potential. The results obtained indicate that
the energy dependence of the imaginary part of the {\alpha}+nucleus
optical-model potential can be described by an exponential decrease. Successful
reproductions of measured cross sections at low energies for {\alpha}-induced
reactions in the mass range 141{\leq}A{\leq}187 confirm the global character of
the Sauerwein-Rauscher potential
Comment on "Quantum Monte Carlo Evidence for Superconductivity in the Three-Band Hubbard Model in Two Dimensions"
In a recent Letter, Kuroki and Aoki [Phys. Rev. Lett. 76, 440 (1996)]
presented quantum Monte-Carlo (QMC) results for pairing correlations in the
three-band Hubbard model, which describes the Cu-d_{x^2-y^2} and O-p_{x,y}
orbitals present in the CuO_2 planes of high-T_c materials. In this comment we
argue that (i) the used parameter set is not appropriate for the description of
high-T_c materials since it does not satisfy the minimal requirement of a
charge-transfer gap at half-filling, and (ii) the observed increase in the
d_{x^2-y^2} channel is dominantly produced by the pair-field correlations
without the vertex part. Hence, the claim of evidence of ODLRO is not
justified.Comment: 1 page latex and 2 eps-figures, uses epsfig, submitted to PR
A variable neurodegenerative phenotype with polymerase gamma mutation
mtDNA replication and repair, causes mitochondrial diseases including autosomal dominant
progressive external ophthalmoplegia (PEO),1 childhood hepato-encephalopathy (Alpers–
Huttenlocher syndrome), adult-onset spinocerebellar ataxia, and sensory nerve degeneration with
dysarthria and ophthalmoparesis (SANDO)
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