680 research outputs found
Generalized Density Matrix Revisited: Microscopic Approach to Collective Dynamics in Soft Spherical Nuclei
The generalized density matrix (GDM) method is used to calculate
microscopically the parameters of the collective Hamiltonian. Higher order
anharmonicities are obtained consistently with the lowest order results, the
mean field [Hartree-Fock-Bogoliubov (HFB) equation] and the harmonic potential
[quasiparticle random phase approximation (QRPA)]. The method is applied to
soft spherical nuclei, where the anharmonicities are essential for restoring
the stability of the system, as the harmonic potential becomes small or
negative. The approach is tested in three models of increasing complexity: the
Lipkin model, model with factorizable forces, and the quadrupole plus pairing
model.Comment: submitted to Physical Review C on 08 May, 201
New global stability estimates for monochromatic inverse acoustic scattering
We give new global stability estimates for monochromatic inverse acoustic
scattering. These estimates essentially improve estimates of [P. Hahner, T.
Hohage, SIAM J. Math. Anal., 33(3), 2001, 670-685] and can be considered as a
solution of an open problem formulated in the aforementioned work
On quantum matrix algebras satisfying the Cayley-Hamilton-Newton identities
The Cayley-Hamilton-Newton identities which generalize both the
characteristic identity and the Newton relations have been recently obtained
for the algebras of the RTT-type. We extend this result to a wider class of
algebras M(R,F) defined by a pair of compatible solutions of the Yang-Baxter
equation. This class includes the RTT-algebras as well as the Reflection
equation algebras
Operator approach to analytical evaluation of Feynman diagrams
The operator approach to analytical evaluation of multi-loop Feynman diagrams
is proposed. We show that the known analytical methods of evaluation of
massless Feynman integrals, such as the integration by parts method and the
method of "uniqueness" (which is based on the star-triangle relation), can be
drastically simplified by using this operator approach. To demonstrate the
advantages of the operator method of analytical evaluation of multi-loop
Feynman diagrams, we calculate ladder diagrams for the massless theory
(analytical results for these diagrams are expressed in terms of multiple
polylogarithms). It is shown how operator formalism can be applied to
calculation of certain massive Feynman diagrams and investigation of Lipatov
integrable chain model.Comment: 16 pages. To appear in "Physics of Atomic Nuclei" (Proceedings of
SYMPHYS-XII, Yerevan, Armenia, July 03-08, 2006
Effect of nitrogenous bases on the thermal stability of jet fuels
Fuels from naphthenic petroleums were evaluated, and it was found that they had more N bases than those paraffinic ones (0.00024 and 0.000009% N, respectively). The removal of the N bases improved significantly the thermal stability and reduced the residue formation during oxidation of the fuel. The improvement depended on both content and composition of the bases. Thus, fuels with similar content of N bases (0.00058% N) and thermal stability had oxidation residues of 17.5 and 5.6 and sol. gum of 13 and 1.5 mg/100 ml, before and after removing the N bases, respectively
External leg amputation in conformal invariant three-point function
Amputation of external legs is carried out explicitly for the conformal
invariant three-point function involving two spinors and one vector field. Our
results are consistent with the general result that amputing an external leg in
a conformal invariant Green function replaces a field by its conformal partner
in the Green function. A new star-triangle relation, involving two spinors and
one vector field, is derived and used for the calculation.Comment: 16 pages; last paragraph added in Sec. 10, presentation improved, to
appear in Eur. Phys. J.
Теплоотдача при нисходящем движении жидкости в условиях сверхкритических давлений
The paper presents some results of experimental investigations on convective heat exchange to laminar n-heptane flow under conditions of over-critical pressure. The case has been considered when directions of forced and free motion are mutually opposite.Under condition tc ≥ tm some specific heat exchange modes being peculiar for the area of over-critical pressure have been determined.On the basis of experimental data on n-heptane heat exchange recommendations for the evaluation of heat exchange intensity as for viscous so for viscous and gravitation modes have been elaborated.Изложены некоторые результаты экспериментальных исследований теплоотдачи к ламинарному потоку н-гептана в условиях сверхкритических давлений. Рассматривался случай, когда направления вынужденного и свободного движения взаимно противоположны.При условии tc ≥ tm обнаружены отдельные режимы теплоотдачи, свойственные для области сверхкритических давлений.На основании опытных данных по теплоотдаче н-гептана разработаны рекомендации для оценки интенсивности теплообмена как при вязкостном, так и вязкостно-гравитационном режимах
Lateral distribution of high energy muons in EAS of sizes Ne approximately equals 10(5) and Ne approximately equals 10(6)
Muon energy spectra and muon lateral distribution in EAS were investigated with the underground magnetic spectrometer working as a part of the extensive air showers (EAS) array. For every registered muon the data on EAS are analyzed and the following EAS parameters are obtained, size N sub e, distance r from the shower axis to muon, age parameter s. The number of muons with energy over some threshold E associated to EAS of fixed parameters are measured, I sub reg. To obtain traditional characteristics, muon flux densities as a function of the distance r and muon energy E, muon lateral distribution and energy spectra are discussed for hadron-nucleus interaction model and composition of primary cosmic rays
Bulk-boundary correspondence in three dimensional topological insulators
We discuss the relation between bulk topological invariants and the spectrum
of surface states in three dimensional non-interacting topological insulators.
By studying particular models, and considering general boundary conditions for
the electron wavefunction on the crystal surface, we demonstrate that using
experimental techniques that probe surface states, only strong topological and
trivial insulating phases can be distinguished; the latter state being
equivalent to a weak topological insulator. In a strong topological insulator,
only the {\it parity} of the number of surface states, but not the number
itself, is robust against time-reversal invariant boundary perturbations. Our
results suggest a \z definition of the bulk-boundary correspondence,
compatible with the \z classification of topological insulators.Comment: TeXLive (Unix), revtex4-1, 7 pages, 3 figure
Coadditive differential complexes on quantum groups and quantum spaces
A regular way to define an additive coproduct (or ``coaddition'') on the
q-deformed differential complexes is proposed for quantum groups and quantum
spaces related to the Hecke-type R-matrices. Several examples of braided
coadditive differential bialgebras (Hopf algebras) are presented.Comment: 9 page
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