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11.
M. Gerçeklioglu 《The European Physical Journal A - Hadrons and Nuclei》2005,24(2):185-191
In this work, the effect of spin-quadrupole forces on the 0+ sates in 158Gd has been investigated. For this purpose, the model Hamiltonian including monopole pairing, quadrupole-quadrupole and spin-quadrupole forces has been diagonalized in one phonon basis. In conclusion, for the distribution of energies of the states and their collective properties, fairly good results have been obtained. 相似文献
12.
M. Combescot X. Leyronas C. Tanguy 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):17-24
The N-ground-state-exciton normalization factor, namely 〈v| B
0
N
B
0
dagN| v〉 = N!F
N, with B
0
d
ag the exact ground state exciton creation operator, differs from N! because the excitons are not perfect bosons. The quantity FN turns out to be crucial for problems dealing with interacting excitons. Indeed, the excitons feel each other not only through
the Coulomb interaction but also through Pauli exclusion between their components. A quite novel purely Pauli contribution
exists in their many-body effects, which relies directly on FN. Following procedures used in the commutation technique we recently introduced to treat interacting close-to-bosons, and
in the BCS theory of superconductivity, we rederive important relations verified by the FN's. We also give new explicit expressions of FN valid for η = Na
x
3/ small but N
2
a
x
3/ large, as FN does not read in terms of η but Nη, the exciton number N being possibly huge in macroscopic samples. Due to this superextensivity, FN does not appear alone in physical quantities, but through ratios like F
N + p/F
N. We end this work by giving the η expansion of these ratios, useful for all purely Pauli many-body effects.
Received 30 May 2002 / Received in final form 12 October 2002 Published online 27 January 2003
RID="a"
ID="a"e-mail: combescot@gps.jussieu.fr 相似文献
13.
S. Duhot R. Mélin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(3):289-296
A Cooper pair from a s-wave superconductor (S) entering a conventional charge density wave (CDW) below the Peierls gap dephases
on the Fermi wavelength while one particle states are localized on the CDW coherence length ξCDW. It is thus practically impossible to observe a Josephson current through a CDW. The paths following different sequences
of impurities interfere destructively, due to the different electron and hole densities in the CDW. The same conclusion holds
for averaging over the conduction channels in the ballistic system. We apply two microscopic approaches to this phenomenon:
(i) a Blonder, Tinkham, Klapwijk (BTK) approach for a single highly transparent S-CDW interface; and (ii) the Hamiltonian
approach for the Josephson effect in a clean CDW and a CDW with non magnetic disorder. The Josephson effect through a spin
density wave (SDW) is limited by the coherence length ξSDW, not by the Fermi wave-length. A Josephson current through a SDW might be observed in a structure with contacts on a SDW
separated by a distance ξSDW. 相似文献
14.
Björn Birnir 《Journal of statistical physics》2007,128(1-2):535-568
A system of ordinary differential equations (ODEs) is derived from a discrete system of Vicsek, Czirók et al. [Phys. Rev. Lett.
75(6):1226–1229, 1995], describing the motion of a school of fish. Classes of linear and stationary solutions of the ODEs are
found and their stability explored using equivariant bifurcation theory. The existence of periodic and toroidal solutions
is also proven under deterministic perturbations and structurally stable heteroclinic connections are found. Applications
of the model to the migration of the capelin, a pelagic fish that undertakes an extensive migration in the North Atlantic,
are discussed and simulation of the ODEs presented. 相似文献
15.
王媛 《阴山学刊(自然科学版)》2007,20(3):21-24
王先谦《庄子集解》是庄学中非常重要的书。地方也“间下己意”,标揭对庄子思想和写作艺术的见解。性质和作者等,王先谦也有独到的观点。它基本上是由郭庆藩的《庄子集释》删略辑成,有的对于庄学研究中一直存在的问题,如《庄子》一书的 相似文献
16.
We report experimental observation of Bardasis–Schrieffer-type s-symmetry collective mode in the d-wave high Tc superconductors. The mode persists above Tc in the pseudogap phase of the underdoped superconductors — direct spectroscopic evidence of the correlations in the particle–particle channel above Tc. 相似文献
17.
The full Dicke model describes a system of N identical two level-atoms coupled to a single mode quantized bosonic field. The model considers rotating and counter-rotating coupling terms between the atoms and the bosonic field, with coupling constants g1 and g2, for each one of the coupling terms, respectively. We study finite temperature properties of the model using the path integral approach and functional methods. In the thermodynamic limit, N→∞, the system exhibits phase transition from normal to superradiant phase, at some critical values of temperature and coupling constants. We distinguish between three particular cases, the first one corresponds to the case of rotating wave approximation, where g1≠0 and g2=0, the second one corresponds to the case of g1=0 and g2≠0, in these two cases the model has a continuous symmetry. The last one, corresponds to the case of g1≠0 and g2≠0, where the model has a discrete symmetry. The phase transition in each case is related to the spontaneous breaking of its respective symmetry. For each one of these three particular cases, we find the asymptotic behaviour of the partition function in the thermodynamic limit, and the collective spectrum of the system in the normal and the superradiant phase. For the case of rotating wave approximation, and also the case of g1=0 and g2≠0, in the superradiant phase, the collective spectrum has a zero energy value, corresponding to the Goldstone mode associated to the continuous symmetry breaking of the model. Our analysis and results are valid in the limit of zero temperature, β→∞, in which, the model exhibits a quantum phase transition. 相似文献
18.
19.
为达到合肥光源二期工程通用模式的设计流强,在储存环上选择垂直方向β函数比较大的位置增加一组八极磁铁。该组八极磁铁对水平方向动力学孔径影响很小,虽然垂直方向动力学孔径明显减小,但仍然大于物理孔径,不会影响束流的注入积累过程。该组八极磁铁产生的垂直方向振荡频率分散可以提供ms量级的Landau阻尼时间,将明显增强抑制垂直方向束流集体不稳定性的能力。该组八极磁铁投入运行后,合肥光源注入积累过程明显改善,注入流强从无八极磁铁时的约100 mA提高到330 mA左右。 相似文献
20.
A one-dimensional fluid with short-range repulsive interaction and one period of cosinusoidal attraction in a periodic container is transformed to a two-mode format. The system has both high-temperature single-phase regions and lowtemperature two-phase regions with a very broad spatial interface that can be stabilized by a weak external field. The case of vanishing external field brings out properties of the mode amplitude dependence which one expects to extend to more complex systems. 相似文献