时间可逆性

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A mathematical or physical process is time-reversible if the dynamics of the process remain well-defined when the sequence of time-states is reversed.

A mathematical or physical process is time-reversible if the dynamics of the process remain well-defined when the sequence of time-states is reversed.

一个数学或物理过程是时间可逆的，如果过程的动力学仍然保持良好的定义时，时间状态的顺序是反向的。

A deterministic process is time-reversible if the time-reversed process satisfies the same dynamic equations as the original process; in other words, the equations are invariant or symmetrical under a change in the sign of time. A stochastic process is reversible if the statistical properties of the process are the same as the statistical properties for time-reversed data from the same process.

A deterministic process is time-reversible if the time-reversed process satisfies the same dynamic equations as the original process; in other words, the equations are invariant or symmetrical under a change in the sign of time. A stochastic process is reversible if the statistical properties of the process are the same as the statistical properties for time-reversed data from the same process.

如果时间反转过程满足与原过程相同的动力学方程，则确定性过程是时间反转的; 换句话说，方程在时间符号的变化下是不变的或对称的。如果过程的统计特性与来自同一过程的时间反演数据的统计特性相同，则随机过程是可逆的。

Mathematics

In mathematics, a dynamical system is time-reversible if the forward evolution is one-to-one, so that for every state there exists a transformation (an involution) π which gives a one-to-one mapping between the time-reversed evolution of any one state and the forward-time evolution of another corresponding state, given by the operator equation:

In mathematics, a dynamical system is time-reversible if the forward evolution is one-to-one, so that for every state there exists a transformation (an involution) π which gives a one-to-one mapping between the time-reversed evolution of any one state and the forward-time evolution of another corresponding state, given by the operator equation:

= = 数学 = = 在数学中，如果正向演化是一对一的，那么动力系统是可逆的，因此对于每一个状态，都存在一个变换(对合) π，它给出了一个一对一的映射，在任何一个状态的时间反向演化和另一个相应状态的向前时间演化之间，由算符方程给出:

[math]\displaystyle{ U_{-t} = \pi \, U_{t}\, \pi }[/math]

U_{-t} = \pi \, U_{t}\, \pi

u _ {-t } = pi，u _ { t } ，pi

Any time-independent structures (e.g. critical points or attractors) which the dynamics give rise to must therefore either be self-symmetrical or have symmetrical images under the involution π.

Any time-independent structures (e.g. critical points or attractors) which the dynamics give rise to must therefore either be self-symmetrical or have symmetrical images under the involution π.

任何与时间无关的结构(例如:。动力学所产生的临界点或吸引子)必然是自对称的，或者在卷积 π 下具有对称映象。

Physics

In physics, the laws of motion of classical mechanics exhibit time reversibility, as long as the operator π reverses the conjugate momenta of all the particles of the system, i.e. [math]\displaystyle{ \mathbf{p} \rightarrow \mathbf{-p} }[/math] (T-symmetry).

In physics, the laws of motion of classical mechanics exhibit time reversibility, as long as the operator π reverses the conjugate momenta of all the particles of the system, i.e. \mathbf{p} \rightarrow \mathbf{-p} (T-symmetry).

= = 物理学 = = 在物理学中，经典力学的运动定律具有时间可逆性，只要运算符 π 反转系统中所有粒子的共轭动量，即:。(t 对称)。

In quantum mechanical systems, however, the weak nuclear force is not invariant under T-symmetry alone; if weak interactions are present, reversible dynamics are still possible, but only if the operator π also reverses the signs of all the charges and the parity of the spatial co-ordinates (C-symmetry and P-symmetry). This reversibility of several linked properties is known as CPT symmetry.

In quantum mechanical systems, however, the weak nuclear force is not invariant under T-symmetry alone; if weak interactions are present, reversible dynamics are still possible, but only if the operator π also reverses the signs of all the charges and the parity of the spatial co-ordinates (C-symmetry and P-symmetry). This reversibility of several linked properties is known as CPT symmetry.

然而，在量子力学系统中，弱核力在 t 对称性下并不是不变的，如果存在弱相互作用，可逆动力学仍然是可能的，但是只有当算符 π 也反转所有电荷的符号和空间坐标的奇偶性(c 对称性和 p 对称性)。几个链接属性的这种可逆性称为 CPT 对称。

Thermodynamic processes can be reversible or irreversible, depending on the change in entropy during the process.

Thermodynamic processes can be reversible or irreversible, depending on the change in entropy during the process.

热力学过程可以是可逆的或不可逆的，这取决于过程中熵的变化。

Stochastic processes

A stochastic process is time-reversible if the joint probabilities of the forward and reverse state sequences are the same for all sets of time increments { τ_s }, for s = 1, ..., k for any k:

A stochastic process is time-reversible if the joint probabilities of the forward and reverse state sequences are the same for all sets of time increments { τs }, for s = 1, ..., k for any k:Tong (1990), Section 4.4

= = = 随机过程 = = = a 随机过程是时间可逆的，如果正向和反向状态序列的联合概率对于所有的时间增量集{ τs }是相同的，对于 s = 1，... ，k 对于任意 k: Tong (1990) ，第4.4节

[math]\displaystyle{ p(x_t, x_{t+\tau_1}, x_{t+\tau_2}, \ldots , x_{t+\tau_k}) = p(x_{t'}, x_{t'-\tau_1}, x_{t'-\tau_2} , \ldots , x_{t'-\tau_k}) }[/math]

p(x_t, x_{t+\tau_1}, x_{t+\tau_2}, \ldots , x_{t+\tau_k}) = p(x_{t'}, x_{t'-\tau_1}, x_{t'-\tau_2} , \ldots , x_{t'-\tau_k})

p (x _ t，x _ { t + tau _ 1} ，x _ { t + tau _ 2} ，ldots，x _ { t + tau _ k }) = p (x _ { t’} ，x _ { t’-tau _ 1} ，x _ { t’-tau _ 2} ，ldots，x _ { t’-tau _ k })

A univariate stationary Gaussian process is time-reversible. Markov processes can only be reversible if their stationary distributions have the property of detailed balance:

[math]\displaystyle{ p(x_t=i,x_{t+1}=j) = \,p(x_t=j,x_{t+1}=i) }[/math]

A univariate stationary Gaussian process is time-reversible. Markov processes can only be reversible if their stationary distributions have the property of detailed balance:

p(x_t=i,x_{t+1}=j) = \,p(x_t=j,x_{t+1}=i)

单变量平稳高斯过程是时间可逆的。马尔可夫过程只有在其平稳分布具有详细平衡性时才可逆: p (x _ t = i，x _ { t + 1} = j) = ，p (x _ t = j，x _ { t + 1} = i)

Kolmogorov's criterion defines the condition for a Markov chain or continuous-time Markov chain to be time-reversible.

Kolmogorov's criterion defines the condition for a Markov chain or continuous-time Markov chain to be time-reversible.

的标准定义了马氏链或连续时间马尔可夫过程是时间可逆的条件。

Time reversal of numerous classes of stochastic processes has been studied, including Lévy processes, stochastic networks (Kelly's lemma), birth and death processes, Markov chains, and piecewise deterministic Markov processes.

Time reversal of numerous classes of stochastic processes has been studied, including Lévy processes, stochastic networks (Kelly's lemma), birth and death processes, Markov chains, and piecewise deterministic Markov processes.

研究了多类随机过程的时间反转问题，包括 Lévy 过程、随机网络(Kelly 引理)、生灭过程、马尔可夫链和分段确定马尔可夫过程。

Waves and optics

Time reversal method works based on the linear reciprocity of the wave equation, which states that the time reversed solution of a wave equation is also a solution to the wave equation since standard wave equations only contain even derivatives of the unknown variables. Thus, the wave equation is symmetrical under time reversal, so the time reversal of any valid solution is also a solution. This means that a wave's path through space is valid when travelled in either direction.

Time reversal method works based on the linear reciprocity of the wave equation, which states that the time reversed solution of a wave equation is also a solution to the wave equation since standard wave equations only contain even derivatives of the unknown variables. Thus, the wave equation is symmetrical under time reversal, so the time reversal of any valid solution is also a solution. This means that a wave's path through space is valid when travelled in either direction.

时间反演法是基于波动方程的线性互易原理，即波动方程的时间反演解也是波动方程的解，因为标准波动方程只包含未知变量的偶数导数。因此，波动方程在时间反转下是对称的，所以任何有效解的时间反转也是一种解。这意味着当波向任何一个方向传播时，波在空间中的路径是有效的。

Time reversal signal processing is a process in which this property is used to reverse a received signal; this signal is then re-emitted and a temporal compression occurs, resulting in a reverse of the initial excitation waveform being played at the initial source.

Time reversal signal processingAnderson, B. E., M. Griffa, C. Larmat, T.J. Ulrich, and P.A. Johnson, “Time reversal,” Acoust. Today, 4 (1), 5-16 (2008). https://acousticstoday.org/time-reversal-brian-e-anderson/ is a process in which this property is used to reverse a received signal; this signal is then re-emitted and a temporal compression occurs, resulting in a reverse of the initial excitation waveform being played at the initial source.

时间反转信号处理安德森，B.e. ，m. 格里法，c. 拉马特，t. j. 乌尔里希和 p.a. 。约翰逊，《时间逆转》 ，艾克斯特。今天，4(1) ，5-16(2008)。Https://acousticstoday.org/time-reversal-brian-e-anderson/是一个过程，其中这个性质是用来逆转接收到的信号，这个信号然后重新发射和时间压缩发生，导致逆转最初的激发波形正在播放在最初的源。

See also

• T-symmetry
• Memorylessness
• Markov property
• Reversible computing

• T-symmetry
• Memorylessness
• Markov property
• Reversible computing

= = =

• t 对称
• 无记忆
• 马尔可夫性
• 可逆计算

= 参考文献 =

• Isham, V. (1991) "Modelling stochastic phenomena". In: Stochastic Theory and Modelling, Hinkley, DV., Reid, N., Snell, E.J. (Eds). Chapman and Hall. .

  • Tong, H. (1990) Non-linear Time Series: A Dynamical System Approach. Oxford UP.

    • Isham, V. (1991) "Modelling stochastic phenomena". In: Stochastic Theory and Modelling, Hinkley, DV., Reid, N., Snell, E.J. (Eds). Chapman and Hall. .
    • Tong, H. (1990) Non-linear Time Series: A Dynamical System Approach. Oxford UP.

    
    

    • 伊沙姆(1991)“建模随机现象”。发表于: 《随机理论与建模》 ，欣克利，德国，里德，新泽西，斯内尔，e.j。(Eds).查普曼和霍尔。.:
    • Tong，h. (1990)非线性时间序列: 一个动力系统的方法。牛津大学。

    Category:Dynamical systems Category:Time series Category:Symmetry

    范畴: 动力系统范畴: 时间序列范畴: 对称性

    
    

    This page was moved from wikipedia:en:Time reversibility. Its edit history can be viewed at 时间可逆性/edithistory