Compared to that for two-dimensional (2D) lattices, our understanding of heat conduction in 2D gases is still limited. Here we study heat conduction behavior of 2D gas systems with momentum-conserving and -nonconserving interparticle interactions by using the nonequilibrium and equilibrium molecular dynamics methods. For the momentum-conserving system, we find that when the dimensionality of the system is changed from 2D to quasi-one-dimensional (quasi-1D), the heat conductivity $\kappa$ diverges with the system size $L$ as $\kappa \sim lnL$ (the theoretical prediction for 2D systems) for a short $L$ and shows, in the thermodynamic limit, a tendency to $\kappa \sim L^{1/3}$ like that predicted in 1D fluids. This suggests that the dimensional-crossover effect of heat conduction exists in 2D systems with conserved momentum. In contrast, for the momentum-nonconserving system, as $L$ increases, finite heat conductivity independent of $L$ is observed. These findings are in agreement with the predictions given by hydrodynamic theory and thus further confirm the validity of the theory in 2D gases.

中文翻译：

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二维动量守恒和非守恒气体中的热传导

与二维（2D）晶格相比，我们对2D气体中热传导的理解仍然有限。在这里，我们通过使用非平衡和平衡分子动力学方法研究具有动量守恒和非守恒粒子间相互作用的二维气体系统的热传导行为。对于动量守恒系统，我们发现当系统的维数从2D变为准一维（准1D）时，热导率$\kappa$ 与系统大小不同 $\mathrm{大号}$ 如 $\kappa 〜ln\mathrm{大号}$ （二维系统的理论预测） $\mathrm{大号}$ 并显示出在热力学极限下的趋势 $\kappa 〜{\mathrm{大号}}^{\mathrm{1个}/3}$就像一维流体中预测的那样 这表明热传导的尺寸交叉效应存在于动量守恒的二维系统中。相反，对于动量非守恒系统，$\mathrm{大号}$ 增加，有限的热导率与 $\mathrm{大号}$被观察到。这些发现与流体力学理论给出的预测一致，因此进一步证实了该理论在二维气体中的有效性。