2,641 research outputs found
B\"acklund-Darboux Transformations and Discretizations of Super KdV Equation
For a generalized super KdV equation, three Darboux transformations and the
corresponding B\"acklund transformations are constructed. The compatibility of
these Darboux transformations leads to three discrete systems and their Lax
representations. The reduction of one of the B\"acklund-Darboux transformations
and the corresponding discrete system are considered for Kupershmidt's super
KdV equation. When all the odd variables vanish, a nonlinear superposition
formula is obtained for Levi's B\"acklund transformation for the KdV equation
A Possibility of Search for New Physics at LHCb
It is interesting to search for new physics beyond the standard model at
LHCb. We suggest that weak decays of doubly charmed baryon such as
to charmless final states would be a possible
signal for new physics. In this work, we consider two models, i.e. the
unparticle and as examples to study such possibilities. We also discuss
the cases for which have not been observed yet, but
one can expect to find them when LHCb begins running. Our numerical results
show that these two models cannot result in sufficiently large decay widths,
therefore if such modes are observed at LHCb, there must be a new physics other
than the unparticle or models.Comment: 7 pages, 3 figures, 1 table. More references and discussion adde
The weak decays of in the light-front quark model
Without contamination from the final state interactions, the calculation of
the branching ratios of semileptonic decays may
provide us more information about the inner structure of charmed baryons.
Moreover, by studying those processes, one can better determine the form
factors of which can be further applied to relevant estimates. In
this work, we use the light-front quark model to carry out the computations
where the three-body vertex functions for and are employed. To
fit the new data of the Belle II, we re-adjust the model parameters and obtain
GeV which is 2.9 times larger than
GeV. This value may imply that the pair in constitutes a more
compact subsystem. Furthermore, we also investigate the non-leptonic decays of
which will be experimentally measured soon, so our model
would be tested by consistency with the new data.Comment: 10 pages, 3 figures and 6 tables. arXiv admin note: text overlap with
arXiv:1912.0143
Observation of forbidden phonons and dark excitons by resonance Raman scattering in few-layer WS
The optical properties of the two-dimensional (2D) crystals are dominated by
tightly bound electron-hole pairs (excitons) and lattice vibration modes
(phonons). The exciton-phonon interaction is fundamentally important to
understand the optical properties of 2D materials and thus help develop
emerging 2D crystal based optoelectronic devices. Here, we presented the
excitonic resonant Raman scattering (RRS) spectra of few-layer WS excited
by 11 lasers lines covered all of A, B and C exciton transition energies at
different sample temperatures from 4 to 300 K. As a result, we are not only
able to probe the forbidden phonon modes unobserved in ordinary Raman
scattering, but also can determine the bright and dark state fine structures of
1s A exciton. In particular, we also observed the quantum interference between
low-energy discrete phonon and exciton continuum under resonant excitation. Our
works pave a way to understand the exciton-phonon coupling and many-body
effects in 2D materials.Comment: 14 pages, 11 figure
Axial Force Analysis and Roll Contour Configuration of Four-High CVC Mill
In order to analyze the influence of technical parameters on work roll axial force of four-high continuous variable crown (CVC) mill, the deformation analyzing model with top roll system and strip was established based on influence function method. Then a CVC work roll curve designing scheme was proposed and it was carried out on some cold rolling mill considering the requirement of comprehensive work roll axial force minimization. The status of comprehensive work roll axial force is improved considering the rolling schedule that is beneficial to the roller bearing. Corresponding to the newly designed work roll contour, the backup roll end chamfer was designed considering comprehensive performance of interroll stress concentration, comprehensive work roll axial force, and strip shape control ability. The distribution of roll wear with newly designed backup roll contour is more even according to the field application data. The newly established roll configuration scheme is beneficial to four-high CVC mill
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