共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Zumsande A. K. Hartmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(4):619-627
General conservation equations are derived for 2D dense
granular flows from the Euler equation within the Boussinesq
approximation. In steady flows, the 2D fields of granular
temperature, vorticity and stream function are shown to be encoded
in two scalar functions only. We checked such prediction on steady
surface flows in a rotating drum simulated through the Non-Smooth
Contact Dynamics method even though granular flows are dissipative
and therefore not necessarily compatible with Euler equation.
Finally, we briefly discuss some possible ways to predict
theoretically these two functions using statistical mechanics. 相似文献
2.
Salkola MI 《Physical review. B, Condensed matter》1994,49(6):4407-4410
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G. Uimin Y. Kudasov P. Fulde A. Ovchinnikov 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):241-244
We discuss the effects of an applied magnetic field on the low-energy excitations in the low temperature phase of Yb4As3. We show also why the magnetic interaction of the Yb3+ ions is nearly of an isotropic Heisenberg spin-1/2 type. A small anisotropy due to an intrachain dipolar interaction leads
to the opening of a gap when a magnetic field is applied. The model agrees with available experimental data. Simple experiments
are suggested in order to further test the present theory.
Received 3 February 1999 相似文献
7.
V. A. Ryzhov 《Physics of the Solid State》2002,44(12):2336-2340
The infrared (IR) and Raman spectra of vitreous poly(methyl methacrylate) (PMMA) are measured and investigated in the frequency range 10–150 cm?1. A comparison of the results obtained from IR and Raman spectroscopic measurements permits the assignment of the low-frequency anomaly (boson peak) observed in the spectra to librational vibrations occurring in a segment of the main chain that is comparable in length to the statistical chain segment. It is demonstrated that coherent librational excitations are associated with the relaxation processes proceeding in the polymers. 相似文献
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Duda LC Schmitt T Nordgren J Kuiper P Dhalenne G Revcolevschi A 《Physical review letters》2004,93(16):169701; author reply 169702
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Shi-liang Li Dao-xin Yao Yi-ming Qiu Hye Jung Kang E. W. Carlson Jiang-ping Hu Gen-fu Chen Nan-lin Wang Peng-cheng Dai 《Frontiers of Physics in China》2010,5(2):161-165
We use inelastic neutron scattering to study the low-energy spin excitations of polycrystalline samples of nonsuperconducting
CeFeAsO and superconducting CeFeAsO0.84F0.16. Two sharp dispersionless modes are found at 0.85 and 1.16 meV in CeFeAsO below the Ce antiferromagnetic (AF) ordering temperature
of T
N
Ce ˜ 4 K. On warming to above T
N
Ce ˜ 4 K, these two modes become one broad dispersionless mode that disappears just above the Fe ordering temperature T
N
Fe ˜ 140 K. For superconducting CeFeAsO0.84F0.16, where Fe static AF order is suppressed, we find a weakly dispersive mode center at 0.4 meV that may arise from short-range
Ce-Ce exchange interactions. Using a Heisenberg model, we simulate powder-averaged Ce spin wave excitations. Our results show
that we need both Ce spin wave and crystal electric field excitations to account for the whole spectra of low-energy spin
excitations. 相似文献
15.
K. A. Kikoin A. de Visser K. Bakker T. Takabatake 《Zeitschrift für Physik B Condensed Matter》1994,94(1-2):79-85
The thermal expansion of a single crystal of the intermetallic compound CeNiSn has been measured at low temperatures 0.3 K<T<12 K and in a magnetic field up to 8 T. A large anisotropy of the linear expansion is observed which is strongly influenced by the magnetic field. These data are interpreted within the theory explaining the origin of the quasigap in the heavy fermion spectrum of CeNiSn by the interplay between the heavy fermions and low-energy excitations in non-cubic Kondo lattices. 相似文献
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Leszek Szybisz 《Zeitschrift für Physik B Condensed Matter》1994,96(2):235-251
It is known that low-energy elementary excitations of symmetric films of liquid4He atT=0 K are characterized by a momentum q parallel to the surface and may be described by bound states. We have evaluated wave functions and energies of these states for both best short-ranged and optimal long-ranged correlations. Quantities of physical interest may be expressed in terms of these eigenstates and, in particular, for very small momenta (q<0.2 Å–1) they are mainly determined by the contribution due to the lowest-lying one. We propose analytic expressions for the lowest-lying excitations and fluctuations in the long-wavelength limit. It is proved that in this limiting case, the excitation energy LW(q) and the averaged static structure functionS
LW(q) should go linearly to zero asq0, whereas the averaged direct correlationX
LW
Dg
(q) should diverge at the origin as 1/q. It is shown that numerical solutions exhibit the expected long-wavelength behavior provided that optimal correlations are used. All these results are displayed in a series of figures and are discussed in detail. 相似文献
18.
Cai YQ Chow PC Restrepo OD Takano Y Togano K Kito H Ishii H Chen CC Liang KS Chen CT Tsuda S Shin S Kao CC Ku W Eguiluz AG 《Physical review letters》2006,97(17):176402
A sharp feature in the charge-density excitation spectra of single-crystal MgB2, displaying a remarkable cosinelike, periodic energy dispersion with momentum transfer (q) along the c* axis, has been observed for the first time by high-resolution nonresonant inelastic x-ray scattering (NIXS). Time-dependent density-functional theory calculations show that the physics underlying the NIXS data is strong coupling between single-particle and collective degrees of freedom, mediated by large crystal local-field effects. As a result, the small-q collective mode residing in the single-particle excitation gap of the B pi bands reappears periodically in higher Brillouin zones. The NIXS data thus embody a novel signature of the layered electronic structure of MgB2. 相似文献
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G. Kh. Panova M. G. Zemlyanov P. P. Parshin A. A. Shikov R. A. Brand 《Physics of the Solid State》2010,52(4):771-775
The specific heat of decagonal Al71.3Ni24.0Fe4.7 and icosahedral Al62Cu25.5Fe12.5 quasicrystals and the Al55.0Si7.0Cu25.5Fe12.5 cubic phase approximating the structure of the icosahedral alloy has been studied in the temperature range 4.2–40.0 K. All
the three compounds exhibit low coefficients of the electronic heat capacity and pronounced deviations of the low-temperature
lattice heat capacity from a cubic temperature law in the range 5–10 K. The results obtained by the thermodynamic method and
inelastic neutron scattering have been compared and analyzed. It has been established that, at energies ɛ < 14 meV, the spectral
density of thermal vibrations in the icosahedral quasicrystal is substantially higher than those in the cubic approximant
and in decagonal quasicrystal. 相似文献
20.
The unambiguously determined bases of the finite dimensional irreducible representation of the unitary and orthogonal groups are constructed. It is shown that the bases can be successfully applied in finding decomposition coefficients when the system of physical particles is divided into two subsystems. The general forms for some of these coefficients are presented.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985. 相似文献