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arXiv 2402.12910cond-mat.stat-mech
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统计力学中的时间不可逆性

Time irreversibility in Statistical Mechanics

Dominique Levesque, Nicolas Sourlas

AI总结:

本文通过分子动力学首次计算了N粒子气体的庞加莱回归时间,发现其随粒子数指数增长,验证了玻尔兹曼假说,并证明对于远小于10^23的粒子数,回归时间已超过宇宙年龄。

摘要:

统计力学中的一个重要问题是:当牛顿运动方程具有时间反演不变性时,不可逆性(时间之箭)是如何产生的。对不可逆性的一个反对意见基于庞加莱回归定理:一个受限的经典哈密顿系统经过一段时间后会回到其初始构型附近,这段时间称为庞加莱回归时间(PRT)。玻尔兹曼的回应是,对于 $N \sim 10^{23}$ 的宏观粒子数,PRT 非常大,超过了宇宙年龄。本文首次使用分子动力学计算了 $N$ 粒子气体这一现实情况下的典型回归时间 $T(N)$。我们发现 $T(N) \sim N^z \exp(y N)$,并确定了不同粒子密度和温度下的指数 $y$ 和 $z$。我们还使用玻尔兹曼假说解析计算了 $y$。我们发现与数值结果非常吻合。这种一致性验证了玻尔兹曼假说,这些假说尚未在数学上得到证明。我们确定,对于相对较少的粒子数(远小于 $10^{23}$),$T(N)$ 就超过了宇宙年龄。

英文摘要:

One of the important questions in statistical mechanics is how irreversibility (time's arrow) occurs when Newton equations of motion are time reversal invariant. One objection to irreversibility is based on Poincaré's recursion theorem: a classical hamiltonian confined system returns after some time, so-called Poincaré recurrence time (PRT), close to its initial configuration. Boltzmann's reply was that for a $N \sim 10^{23} $ macroscopic number of particles, PRT is very large and exceeds the age of the universe. In this paper we compute for the first time, using molecular dynamics, a typical recurrence time $ T(N)$ for a realistic case of a gas of $N$ particles. We find that $T(N) \sim N^z \exp (y N) $ and determine the exponents $y$ and $z$ for different values of the particle density and temperature. We also compute $y$ analytically using Boltzmann's hypotheses. We find an excellent agreement with the numerical results. This agreement validates Boltzmann's hypotheses which are not yet mathematically proven. We establish that that $T(N) $ exceeds the age of the Universe for a relatively small number of particles, much smaller than $ 10^{23} $.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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