Fokker-Planck P(y,t): Understanding the Derivation

  • Thread starter Thread starter Abigale
  • Start date Start date
AI Thread Summary
The discussion centers on the derivation and equivalence of the Fokker-Planck equation (FPE) from the master equation. The participant expresses confusion regarding the conditions under which two forms of the FPE are considered equal, specifically questioning the assumption that the derivative of P with respect to y is zero. They seek clarification on why this condition holds, implying it may only be valid when P is constant. The conversation also touches on the identity of the book's author, indicating a desire for further context or reference. Overall, the focus is on understanding the mathematical foundations and implications of the FPE in stochastic processes.
Abigale
Messages
53
Reaction score
0
I am Reading in a Book of Stochastic Processes.

I understood the Derivation of the Fokker-Planck equation from the master equation.
The Result is (the FPE):
$$
\frac{\partial P(y,t)}{\partial t}
=
- \frac{\partial}{\partial y}
{ \lbrace {a_{1}(y)P} \rbrace }
+
\frac{1}{2}
\frac{\partial ^{2} }{\partial ^{2} y}
{\lbrace {a_{2}(y)P} \rbrace}
$$

Than the author recommits to the FPE, which he introduced at the beginning of the chapter.
He says, both are equal.

$$
\frac{\partial P(y,t)}{\partial t}
=
- \frac{\partial}{\partial y}
A(y)P
+
\frac{1}{2}
\frac{\partial ^{2} y}{\partial ^{2}}
B(y)P
$$

I don't understand why they should be equal.
I think that they are just equal, wenn \frac{\partial P(y,t)}{\partial y} = 0. But why sould it be zero/ P=const ?
 
Physics news on Phys.org
I know this is an old post, but what is the author of the book you are reading?

I am not sure if I can answer your question.
 
I know this is an old post, but what is the author of the book you are reading?

I am not sure if I can answer your question.
 
Hello! Let's say I have a cavity resonant at 10 GHz with a Q factor of 1000. Given the Lorentzian shape of the cavity, I can also drive the cavity at, say 100 MHz. Of course the response will be very very weak, but non-zero given that the Loretzian shape never really reaches zero. I am trying to understand how are the magnetic and electric field distributions of the field at 100 MHz relative to the ones at 10 GHz? In particular, if inside the cavity I have some structure, such as 2 plates...
Back
Top