请输入您要查询的百科知识:

 

词条 Gamma process
释义

  1. Properties

      Marginal distribution    Scaling    Adding independent processes    Moments    Moment generating function    Correlation  

  2. References

{{About|the stochastic process|the astrophysical nucleosynthesis process|Gamma process (astrophysics)}}{{multiple issues|{{Expert needed|Mathematics|date=November 2008}}{{Context|date=March 2010}}
}}

A gamma process is a random process with independent gamma distributed increments. Often written as , it is a pure-jump increasing Lévy process with intensity measure for positive . Thus jumps whose size lies in the interval occur as a Poisson process with intensity The parameter controls the rate of jump arrivals and the scaling parameter inversely controls the jump size. It is assumed that the process starts from a value 0 at t=0.

The gamma process is sometimes also parameterised in terms of the mean () and variance () of the increase per unit time, which is equivalent to and .

Properties

Since we use the Gamma function in these properties, we may write the process at time as to eliminate ambiguity.

Some basic properties of the gamma process are:{{citation needed|date=February 2012}}

Marginal distribution

The marginal distribution of a gamma process at time is a gamma distribution with mean and variance

That is, its density is given by

Scaling

Multiplication of a gamma process by a scalar constant is again a gamma process with different mean increase rate.

Adding independent processes

The sum of two independent gamma processes is again a gamma process.

Moments

where is the Gamma function.

Moment generating function

Correlation

, for any gamma process

The gamma process is used as the distribution for random time change in the variance gamma process.

References

  • Lévy Processes and Stochastic Calculus by David Applebaum, CUP 2004, {{ISBN|0-521-83263-2}}.
{{Stochastic processes}}{{probability-stub}}

1 : Lévy processes

随便看

 

开放百科全书收录14589846条英语、德语、日语等多语种百科知识,基本涵盖了大多数领域的百科知识,是一部内容自由、开放的电子版国际百科全书。

 

Copyright © 2023 OENC.NET All Rights Reserved
京ICP备2021023879号 更新时间:2024/9/22 21:27:51