Chapman-Kolmogorov equations, continuous time Markov chains, why do they have this solution.
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$P^'(t)=QP(t)=P(t)Q$
These are the Chapman-Kolmogorov backward and forward equations for a countable sate space continuous time Markov Chain. They have the solution,
$
P(t)=e^Qt
$
I have two questions
1) in the finite state space case, why is this a solution?
2) In the case where we have an infinite state space and the above are the infinite matrices how do we get this as a solution? I know this is a much harder question so maybe just a brief outline of an answer will help. Does the problem come from bringing the derivative inside the infinite sum?
probability stochastic-processes markov-chains
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up vote
0
down vote
favorite
$P^'(t)=QP(t)=P(t)Q$
These are the Chapman-Kolmogorov backward and forward equations for a countable sate space continuous time Markov Chain. They have the solution,
$
P(t)=e^Qt
$
I have two questions
1) in the finite state space case, why is this a solution?
2) In the case where we have an infinite state space and the above are the infinite matrices how do we get this as a solution? I know this is a much harder question so maybe just a brief outline of an answer will help. Does the problem come from bringing the derivative inside the infinite sum?
probability stochastic-processes markov-chains
add a comment |Â
up vote
0
down vote
favorite
up vote
0
down vote
favorite
$P^'(t)=QP(t)=P(t)Q$
These are the Chapman-Kolmogorov backward and forward equations for a countable sate space continuous time Markov Chain. They have the solution,
$
P(t)=e^Qt
$
I have two questions
1) in the finite state space case, why is this a solution?
2) In the case where we have an infinite state space and the above are the infinite matrices how do we get this as a solution? I know this is a much harder question so maybe just a brief outline of an answer will help. Does the problem come from bringing the derivative inside the infinite sum?
probability stochastic-processes markov-chains
$P^'(t)=QP(t)=P(t)Q$
These are the Chapman-Kolmogorov backward and forward equations for a countable sate space continuous time Markov Chain. They have the solution,
$
P(t)=e^Qt
$
I have two questions
1) in the finite state space case, why is this a solution?
2) In the case where we have an infinite state space and the above are the infinite matrices how do we get this as a solution? I know this is a much harder question so maybe just a brief outline of an answer will help. Does the problem come from bringing the derivative inside the infinite sum?
probability stochastic-processes markov-chains
edited Aug 2 at 22:19
asked Aug 2 at 18:37


Monty
15212
15212
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1) This just the solution of this ODE. You can compute it using for instance the definition of the matrix exponential:
$$e^A = sum_j=0^infty frac1j!A^j.$$
We have $$P(t) = e^tQ = sum_j=0^infty frac1j!t^jQ^j.$$
When differentiating $P(t)$ w.r.t. to $t$, you obtain $$P'(t) = sum_j=1^infty frac1j!(jt^j-1)Q^j = left(sum_j=1^infty frac1(j-1)!t^j-1Q^j-1right)Q = P(t)Q.$$
Equivalently you can bracket the single $Q$ out to the left and obtain $P'(t) = QP(t)$.
2) I think, when using the definition of the matrix exponential above, you can prove the same statement also for the infinite state space case.
add a comment |Â
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
0
down vote
1) This just the solution of this ODE. You can compute it using for instance the definition of the matrix exponential:
$$e^A = sum_j=0^infty frac1j!A^j.$$
We have $$P(t) = e^tQ = sum_j=0^infty frac1j!t^jQ^j.$$
When differentiating $P(t)$ w.r.t. to $t$, you obtain $$P'(t) = sum_j=1^infty frac1j!(jt^j-1)Q^j = left(sum_j=1^infty frac1(j-1)!t^j-1Q^j-1right)Q = P(t)Q.$$
Equivalently you can bracket the single $Q$ out to the left and obtain $P'(t) = QP(t)$.
2) I think, when using the definition of the matrix exponential above, you can prove the same statement also for the infinite state space case.
add a comment |Â
up vote
0
down vote
1) This just the solution of this ODE. You can compute it using for instance the definition of the matrix exponential:
$$e^A = sum_j=0^infty frac1j!A^j.$$
We have $$P(t) = e^tQ = sum_j=0^infty frac1j!t^jQ^j.$$
When differentiating $P(t)$ w.r.t. to $t$, you obtain $$P'(t) = sum_j=1^infty frac1j!(jt^j-1)Q^j = left(sum_j=1^infty frac1(j-1)!t^j-1Q^j-1right)Q = P(t)Q.$$
Equivalently you can bracket the single $Q$ out to the left and obtain $P'(t) = QP(t)$.
2) I think, when using the definition of the matrix exponential above, you can prove the same statement also for the infinite state space case.
add a comment |Â
up vote
0
down vote
up vote
0
down vote
1) This just the solution of this ODE. You can compute it using for instance the definition of the matrix exponential:
$$e^A = sum_j=0^infty frac1j!A^j.$$
We have $$P(t) = e^tQ = sum_j=0^infty frac1j!t^jQ^j.$$
When differentiating $P(t)$ w.r.t. to $t$, you obtain $$P'(t) = sum_j=1^infty frac1j!(jt^j-1)Q^j = left(sum_j=1^infty frac1(j-1)!t^j-1Q^j-1right)Q = P(t)Q.$$
Equivalently you can bracket the single $Q$ out to the left and obtain $P'(t) = QP(t)$.
2) I think, when using the definition of the matrix exponential above, you can prove the same statement also for the infinite state space case.
1) This just the solution of this ODE. You can compute it using for instance the definition of the matrix exponential:
$$e^A = sum_j=0^infty frac1j!A^j.$$
We have $$P(t) = e^tQ = sum_j=0^infty frac1j!t^jQ^j.$$
When differentiating $P(t)$ w.r.t. to $t$, you obtain $$P'(t) = sum_j=1^infty frac1j!(jt^j-1)Q^j = left(sum_j=1^infty frac1(j-1)!t^j-1Q^j-1right)Q = P(t)Q.$$
Equivalently you can bracket the single $Q$ out to the left and obtain $P'(t) = QP(t)$.
2) I think, when using the definition of the matrix exponential above, you can prove the same statement also for the infinite state space case.
answered Aug 2 at 18:57


Jonas
259210
259210
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