发表机构
A. P. C. Roy Government College; Maulana Azad College; University of Calcutta; Murshidabad Maharaja Krishnanath University（A.P.C.罗伊政府学院; 莫拉纳阿扎德学院; 加尔各答大学; 穆尔希达巴德马哈拉贾克里希纳纳特大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文研究临界点附近引入慢非平衡模式（OEM）对动态密度涨落功率谱的影响，发现OEM使瑞利峰和布里渊峰宽度减小、高度不等，并揭示广延性条件对耦合的约束，表明涨落衰减变慢的临界特征。
AI 中文摘要
我们研究了为扩展临界点附近流体动力学有效性范围而引入的慢非平衡模式（OEM）如何从根本上重塑动态密度涨落的功率谱。我们利用慢模式的运动方程，针对热力学的广延性质不因引入OEM而改变的情形进行了分析。我们发现，广延性条件对OEM与速度的四散度之间的耦合施加了额外约束。在不存在OEM的情况下，动态结构因子呈现三个洛伦兹峰：一个位于零频率（$\omega$）处，称为瑞利峰；另外两个关于$\omega=0$对称分布，称为布里渊峰。当系统远离临界点时，OEM的引入保持了分布的对称性，但所有峰的宽度均减小，且布里渊峰呈现不等的高度。无论OEM的值如何（零或非零），布里渊峰在临界点附近都会消失。在存在OEM时，瑞利峰的宽度显著减小。这些宽度在存在OEM时的减小表明涨落衰减率降低，从而导致涨落衰减变慢，这是临界点的一个显著特征。
英文摘要
We investigate how slow out-of-equilibrium modes (OEM), introduced to extend the regime of validity of hydrodynamics near the critical point, fundamentally reshape the power spectrum of dynamical density fluctuations. We have used the equation of motion of slow modes for the situation when the extensive nature of thermodynamics is not altered due to the introduction of OEM. We find that the extensivity condition puts an extra constraint on the coupling of OEM with the four divergence of velocity. In the absence of OEM, the dynamic structure factor exhibits three Lorentzian peaks, one at zero frequency ($ω$), called Rayleigh peak and the other two called Brillouin peaks located symmetrically about $ω=0$. When the system is away from the critical point the inclusion of the OEM preserves the symmetry of the distributions but all the peaks acquire reduced widths and the Brillouin peaks adopt unequal heights. Irrespective of the value of OEM (zero or nonzero) the Brillouin peaks vanish near the critical point. The width of the Rayleigh peak substantially reduced in presence of OEM. Such reductions of the widths in presence of the OEM indicates the reduction in the decay rate of the fluctuation which leads to slowing down of decay of the fluctuations, a distinctive feature of the critical point.
Comments23 pages, 13 figures
