7,203 research outputs found
Weak decays of the B_c meson to charmonium and D mesons in the relativistic quark model
Semileptonic and nonleptonic decays of the B_c meson to charmonium and D
mesons are studied in the framework of the relativistic quark model. The decay
form factors are explicitly expressed through the overlap integrals of the
meson wave functions in the whole accessible kinematical range. The
relativistic meson wave functions are used for the calculation of the decay
rates. The obtained results are compared with the predictions of other
approaches.Comment: 27 pages, 17 figures, 1 figure and 1 reference added, version to
appear in Phys. Rev.
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Processing of Silicon Carbide by Laser Micro Sintering
Silicon carbide – a solid with covalent bonds - is conventionally synthesized via the Acheson
process. Usually solid bodies of silicon carbide with definite shapes are generated from the
grained material via hot isostatic pressing or liquid phase sintering. Both processes are
conducted under well-controlled temperature regimes. Applying the freeform fabrication
technique “Laser Micro Sintering” poses a big challenge to experimental skill due to the nonequilibrium conditions that are characteristic features of laser material processing.
Successive layers SiC layers with a thickness of 1μm were processed with coherent
radiation of 1064 nm. The specific behavior of two different silicon carbide powders - one of
them blended with additives - are reported along with interpretational approaches.Mechanical Engineerin
DevOps in Practice -- A preliminary Analysis of two Multinational Companies
DevOps is a cultural movement that aims the collaboration of all the
stakeholders involved in the development, deployment and operation of soft-ware
to deliver a quality product or service in the shortest possible time. DevOps
is relatively recent, and companies have developed their DevOps prac-tices
largely from scratch. Our research aims to conduct an analysis on practic-ing
DevOps in +20 software-intensive companies to provide patterns of DevOps
practices and identify their benefits and barriers. This paper presents the
preliminary analysis of an exploratory case study based on the interviews to
relevant stakeholders of two (multinational) companies. The results show the
benefits (software delivery performance) and barriers that these companies are
dealing with, as well as DevOps team topology they approached during their
DevOps transformation. This study aims to help practitioners and researchers to
better understand DevOps transformations and the contexts where the practices
worked. This, hopefully, will contribute to strengthening the evidence
regarding DevOps and supporting practitioners in making better informed
decisions about the return of investment when adopting DevOps.Comment: 8 pages, 1 figure, 2 tables, conferenc
Cooper pairing and finite-size effects in a NJL-type four-fermion model
Starting from a NJL-type model with N fermion species fermion and difermion
condensates and their associated phase structures are considered at nonzero
chemical potential and zero temperature in spaces with nontrivial
topology of the form and . Special
attention is devoted to the generation of the superconducting phase. In
particular, for the cases of antiperiodic and periodic boundary conditions we
have found that the critical curve of the phase transitions between the chiral
symmetry breaking and superconducting phases as well as the corresponding
condensates and particle densities strongly oscillate vs ,
where is the length of the circumference . Moreover, it is shown that
at some finite values of the superconducting phase transition is shifted to
smaller values both of and particle density in comparison with the case
of .Comment: 13 pages, 13 figures; minor changes; new references added; version
accepted to PR
A moving boundary model motivated by electric breakdown: II. Initial value problem
An interfacial approximation of the streamer stage in the evolution of sparks
and lightning can be formulated as a Laplacian growth model regularized by a
'kinetic undercooling' boundary condition. Using this model we study both the
linearized and the full nonlinear evolution of small perturbations of a
uniformly translating circle. Within the linear approximation analytical and
numerical results show that perturbations are advected to the back of the
circle, where they decay. An initially analytic interface stays analytic for
all finite times, but singularities from outside the physical region approach
the interface for , which results in some anomalous relaxation at
the back of the circle. For the nonlinear evolution numerical results indicate
that the circle is the asymptotic attractor for small perturbations, but larger
perturbations may lead to branching. We also present results for more general
initial shapes, which demonstrate that regularization by kinetic undercooling
cannot guarantee smooth interfaces globally in time.Comment: 44 pages, 18 figures, paper submitted to Physica
Observation and theoretical description of the pure Fano-effect in the valence-band photo-emission of ferromagnets
The pure Fano-effect in angle-integrated valence-band photo-emission of
ferromagnets has been observed for the first time. A contribution of the
intrinsic spin polarization to the spin polarization of the photo-electrons has
been avoided by an appropriate choice of the experimental parameters. The
theoretical description of the resulting spectra reveals a complete analogy to
the Fano-effect observed before for paramagnetic transition metals. While the
theoretical photo-current and spin difference spectra are found in good
quantitative agreement with experiment in the case of Fe and Co only a
qualitative agreement could be achieved in the case of Ni by calculations on
the basis of plain local spin density approximation (LSDA). Agreement with
experimental data could be improved in this case in a very substantial way by a
treatment of correlation effects on the basis of dynamical mean field theory
(DMFT).Comment: 11 pages, 3 figures accepted by PR
Massive quark propagator and competition between chiral and diquark condensate
The Green-function approach has been extended to the moderate baryon density
region in the framework of an extended Nambu--Jona-Lasinio model, and the
thermodynamic potential with both chiral and diquark condensates has been
evaluated by using the massive quark propagator. The phase structure along the
chemical potential direction has been investigated and the strong competition
between the chiral and diquark condensate has been analyzed by investigating
the influence of the diquark condensate on the sharp Fermi surface. The
influence of the diquark condensate on the quark properties has been
investigated, even though the quarks in the color breaking phase are very
different from that in the chiral breaking phase, the difference between quarks
in different colors is very small.Comment: Revtex, 34 pages, 7 figures, section V revised, accepted by PR
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