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61.
62.
基于三维旋量Gross-Pitaevskii(GP)方程研究在含时周期性外磁场作用下玻色-爱因斯坦凝聚体的动力学行为.结果显示,在含时周期外磁场的作用下,铁磁态自旋为1的玻色-爱因斯坦凝聚体将发生拓扑形变.当磁场的两个零点进入凝聚体后,自旋向上态的密度布居图在z轴上分别形成向上和向下的凸起.随着磁场的两个零点在凝聚体内逐渐重合,向上和向下的凸起被拉长,最终自旋向上态在z轴上呈线状分布,这与理论分析预测得到的孤立狄拉克弦相对应.最后,通过计算凝聚体的超流涡度给出磁单极的表征图.结果显示,凝聚体在磁场的两个零点处形成正、负磁单极对,分别对应着自旋向上态在z轴上向上和向下的凸起.随着磁场的两个零点重合,正、负磁单极对中的两条狄拉克弦逐渐靠近,之后大约经5 ms,它们完全相连,最终形成孤立的狄拉克弦. 相似文献
63.
本文运用拉格朗日理论研究了物质波孤子在外势作用下的运动情况,主要讨论了初速度为零的孤子在势井和势垒中所表现出的不同行为,结果显示势垒能排斥孤子,势井能吸引孤子,并用数值模拟的方法使其得到了验证. 相似文献
64.
We consider the dynamics and formation of vortices from ring dark solitons in a two-dimensional Bose–Einstein condensate with the Rashba spin–orbit coupling based on the time-dependent coupled Gross–Pitaevskii equation. Compared with previous results, the system exhibits complex dynamical behaviors in the presence of the spin–orbit coupling. With the modulation of the spin–orbit coupling, not only the lifetime of ring dark solitons is greatly prolonged, but also their attenuation kinetics is significantly affected. For two shallow ring dark solitons with the equal strength of the spin–orbit coupling, the radius of ring dark solitons increases to a maximum value over time and then shrinks into a minimum value. Due to the effect of the snake instability, ring dark solitons split into a series of ring-like clusters of vortex pairs, which perform complex oscillations. This indicates that the system is strongly dependent on the presence of the spin–orbit coupling. Furthermore, the effect of different initial modulation depths on the dynamics of ring dark solitons is investigated. 相似文献
65.
研究了玻色-爱因斯坦凝聚体中非线性相互作用对量子共振棘流的影响.满足量子共振条件的周期驱动使得波包在动量空间出现弹道扩散,当波包扩散具有特定方向时,系统就出现定向的动量流.弱非线性相互作用下的冷原子分成两簇,它们分别受到方向相反的稳定周期驱动力,以各自恒定的加速度沿相反方向运动.波包在动量空间的扩散表现为两个稳定的沿相反方向运动的峰.非线性相互作用的增强使得正方向运动的冷原子减少,负方向运动的冷原子增加,从而系统的动量流减弱甚至反转.当非线性相互作用足够强时,动量空间中的波包只有一个稳定的峰,且峰值对应的动量不随时间变化.此时冷原子受的周期驱动力为零,定向的动量流消失. 相似文献
66.
In the present paper we study Anderson localization of Bose-Einstein condensate with a weakly positive nonlinearity under the influence of chaotic potentials. We investigate the one-dimensional Gross-Pitaevskii equation numerically, in order to unveil the influence of the parameters that describe the potential and nonlinearity on the localization of the condensate. The results show that matter localization is possible, in certain regions in parameter space. Similarities to chaotically disordered photonic lattices suggest that the results are of direct interest to such photonic lattices as well. 相似文献
67.
ZHOU Li-Juan GU Yun-Ting MA Wei-Xing MENG Cheng-Ju PAN Ji-Huan 《理论物理通讯》2008,49(1):181-188
Based on the Global Color Symmetry Model, the non-perturbative Q, CD vacuum is investigated in the parameterized fully dressed quark propagator. Our theoretical predictions for various quantities characterized the QCD vacuum are in agreement with those predicted by many other phenomenologieal QCD inspired models. The successful predictions clearly indicate the extensive validity of our parameterized quark propagator used here. A detailed discussion on the arbitrariness in determining the integration cut-off parameter ofμ in calculating QCD vacuum condensates and a good method, which avoided the dependence of calculating results on the cut-off parameter is also strongly recommended to readers. 相似文献
68.
工业中大量生产的端羟基聚醚 ,由于羟基的反应活性不够 ,不能直接用于增韧胺类固化的环氧树脂 .Bu2 SnO Bu3PO4 缩合物能催化羟基对环氧基的加成反应 .本文研究在Bu2 SnO Bu3PO4 缩合物Sn P6 70 0的存在下以端羟基聚四氢呋喃 (PTMG)增韧芳香胺 4,4′ 二氨基二苯砜 (DDS)固化的环氧树脂 .PTMG首先与环氧树脂反应生成嵌段共聚物 ,在固化时发生微相分离 .分散相的尺寸在有利于增韧的范围内 .PTMG在分子量与浓度适当时 ,能使树脂的断裂韧性大大提高 ;抗弯强度也有显著提高 ,而Tg 和模量略有降低 . 相似文献
69.
ZONG Hong-Shi SUN Wei-Min 《理论物理通讯》2006,46(5):901-904
By differentiating the inverse dressed quark propagator at finite chemical potential μ with respect to μ, the linear response of the dressed quark propagato r to the chemical potential can be obtained, From this we extract a modelindependent formula for the linear chemical potential dependence of the in-medium two-quark condensate and show by two independent methods (explicit calculation and Lorentz covariance arguments) that the first-order contribution in μ to the in-medium two-quark condensate vanishes identically. Therefore if one wants to study the in-medium two-quark condensate one should expand to at/east the second order in the chemical potential μ. 相似文献
70.
Effects of periodic optical lattice potential on dark solitons in a Bose Einstein condensate 下载免费PDF全文
This paper investigates the dynamics of dark solitons in a
Bose--Einstein condensate with a magnetic trap and an optical
lattice (OL) trap, and analyses the effects of the periodic OL
potential on the dynamics by applying the variational approach based
on the renormalized integrals of motion. The results show that the
dark soliton becomes only a standing-wave and free propagation
of the dark soliton is not possible when the periodic length of the
OL potential is approximately equal to the effective width of the
dark soliton. When the periodic length is very small or very large,
the effects of the OL potential on the dark soliton will be sharply
reduced. Finally, the numerical results confirm these theoretical
findings. 相似文献