共查询到20条相似文献,搜索用时 31 毫秒
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《Journal of Geometry and Physics》2007,57(1):89-100
In this paper we study a generalized Darboux Halphen system given by where , , are real variables, are real constants and We prove that, for any , this system does not admit any non-constant global first integral that can be described by a formal power series. Furthermore, restricting the values of to a full Lebesgue measure set, we prove that this system does not admit any non-constant rational or Darbouxian global first integral. This is a first step toward proving that this system is chaotic. 相似文献
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In this paper we investigate Leibniz algebras whose quotient Lie algebra is a naturally graded filiform Lie algebra . We introduce a Fock module for the algebra and provide classification of Leibniz algebras whose corresponding Lie algebra is the algebra with condition that the ideal is a Fock -module, where is the ideal generated by squares of elements from .We also consider Leibniz algebras with corresponding Lie algebra and such that the action gives rise to a minimal faithful representation of . The classification up to isomorphism of such Leibniz algebras is given for the case of . 相似文献
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The pentagram map is now known to be a discrete integrable system. We show that the integrals for the pentagram map are constant along Poncelet families. That is, if and are two polygons in the same Poncelet family, and is a monodromy invariant for the pentagram map, then . Our proof combines complex analysis with an analysis of the geometry of a degenerating sequence of Poncelet polygons. 相似文献
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Stephan Narison 《Physics letters. [Part B]》2013,718(4-5):1321-1333
Using recent values of the QCD (non-)perturbative parameters given in Table 1 and an estimate of the N3LO QCD perturbative contributions based on the geometric growth of the PT series, we re-use QCD spectral sum rules (QSSR) known to N2LO PT series and including all dimension-six NP condensate contributions in the full QCD theory, for improving the existing estimates of and from the open charm and beauty systems. We especially study the effects of the subtraction point on “different QSSR data” and use (for the first time) the Renormalization Group Invariant (RGI) scale-independent quark masses in the analysis. The estimates [rigourous model-independent upper bounds within the SVZ framework] reported in Table 8: , and , , which improve previous QSSR estimates, are in perfect agreement (in values and precisions) with some of the experimental data on and on recent lattice simulations within dynamical quarks. These remarkable agreements confirm both the success of the QSSR semi-approximate approach based on the OPE in terms of the quark and gluon condensates and of the Minimal Duality Ansatz (MDA) for parametrizing the hadronic spectral function which we have tested from the complete data of the and ? systems. The values of the running quark masses and from are in good agreement though less accurate than the ones from recent and ? sum rules. 相似文献
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《Radiation measurements》2007,42(4-5):644-647
The tetragonal : persistent luminescence materials were prepared by a solid state reaction. The UV excited and persistent luminescence was observed in the green region centred at 535 nm. Both luminescence phenomena are due to the same ion occupying the single site in the host lattice. The codoping usually reduced the persistent luminescence of :, which differs from the : and : materials. Only the ion enhanced slightly the persistent luminescence. With the aid of synchrotron radiation, the band gap energy of : was found to be about 7 eV that is very similar to those of the : materials. Thermoluminescence results suggested that the ions might act as electron traps, but only the TL peaks created by and can be found in the temperature range accessible. Lattice defects (e.g. oxygen vacancies) are also important, since the same main thermoluminescence peak was observed at about with and without codoping. 相似文献
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《Comptes Rendus Physique》2016,17(7):789-801
It is generally assumed that a condensate of paired fermions at equilibrium is characterized by a macroscopic wavefunction with a well-defined, immutable phase. In reality, all systems have a finite size and are prepared at non-zero temperature; the condensate has then a finite coherence time, even when the system is isolated in its evolution and the particle number N is fixed. The loss of phase memory is due to interactions of the condensate with the excited modes that constitute a dephasing environment. This fundamental effect, crucial for applications using the condensate of pairs' macroscopic coherence, was scarcely studied. We link the coherence time to the condensate phase dynamics, and we show with a microscopic theory that the time derivative of the condensate phase operator is proportional to a chemical potential operator that we construct including both the pair-breaking and pair-motion excitation branches. In a single realization of energy E, evolves at long times as , where is the microcanonical chemical potential; energy fluctuations from one realization to the other then lead to a ballistic spreading of the phase and to a Gaussian decay of the temporal coherence function with a characteristic time . In the absence of energy fluctuations, the coherence time scales as N due to the diffusive motion of . We propose a method to measure the coherence time with ultracold atoms, which we predict to be tens of milliseconds for the canonical ensemble unitary Fermi gas. 相似文献
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We applied the numerical renormalization group method to study the electron spin resonance (ESR) of a single-impurity Anderson model with a gap in the conduction electron density of states, centered at the Fermi level. We analyzed the relaxation rate of a magnetic probe located at a position around the Anderson impurity. It presents different behaviors for the symmetric and the asymmetric case. For the symmetric case and any , goes to a constant for (Kondo resonance). decreases monotonically to zero only for . For the asymmetric case, there is a under which decreases monotonically to zero as , and above which saturates, as occurs in the symmetric case for . This behavior indicates a quantum phase transition from the quenched to the unquenched magnetic moment in the ground state of the Anderson ion. 相似文献