Integral as: martingale or local martingale












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$begingroup$


I wonder when a stochastic integral is a martingale or a local martingale. Let's assume that we have a process:



$X_t = X_0 + int_{0}^{t} a_s ds + int_0^t b_s dW_s$



Is this kind of integral a martingale or local martingale. Is this connected with the integral $int_{0}^{t} a_s ds$? (if it is present, the process is a martigale and in the opposite situation it is a local martingale?). What would happen if we have some proces $Y_t$ and our $X_t$ looks like that:



$X_t = X_0 + int_{0}^{t} f(Y_s) ds + int_0^t f(Y_s) dW_s$



I would love to read something more about those properties. I will appreciate any link/paper related to this topic.










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$endgroup$












  • $begingroup$
    What if $a_s=s$?
    $endgroup$
    – d.k.o.
    Jan 31 at 22:42












  • $begingroup$
    Your "first" process $X_t$ is a martingale iff $a:=0$.
    $endgroup$
    – saz
    Feb 1 at 7:10
















0












$begingroup$


I wonder when a stochastic integral is a martingale or a local martingale. Let's assume that we have a process:



$X_t = X_0 + int_{0}^{t} a_s ds + int_0^t b_s dW_s$



Is this kind of integral a martingale or local martingale. Is this connected with the integral $int_{0}^{t} a_s ds$? (if it is present, the process is a martigale and in the opposite situation it is a local martingale?). What would happen if we have some proces $Y_t$ and our $X_t$ looks like that:



$X_t = X_0 + int_{0}^{t} f(Y_s) ds + int_0^t f(Y_s) dW_s$



I would love to read something more about those properties. I will appreciate any link/paper related to this topic.










share|cite|improve this question









$endgroup$












  • $begingroup$
    What if $a_s=s$?
    $endgroup$
    – d.k.o.
    Jan 31 at 22:42












  • $begingroup$
    Your "first" process $X_t$ is a martingale iff $a:=0$.
    $endgroup$
    – saz
    Feb 1 at 7:10














0












0








0





$begingroup$


I wonder when a stochastic integral is a martingale or a local martingale. Let's assume that we have a process:



$X_t = X_0 + int_{0}^{t} a_s ds + int_0^t b_s dW_s$



Is this kind of integral a martingale or local martingale. Is this connected with the integral $int_{0}^{t} a_s ds$? (if it is present, the process is a martigale and in the opposite situation it is a local martingale?). What would happen if we have some proces $Y_t$ and our $X_t$ looks like that:



$X_t = X_0 + int_{0}^{t} f(Y_s) ds + int_0^t f(Y_s) dW_s$



I would love to read something more about those properties. I will appreciate any link/paper related to this topic.










share|cite|improve this question









$endgroup$




I wonder when a stochastic integral is a martingale or a local martingale. Let's assume that we have a process:



$X_t = X_0 + int_{0}^{t} a_s ds + int_0^t b_s dW_s$



Is this kind of integral a martingale or local martingale. Is this connected with the integral $int_{0}^{t} a_s ds$? (if it is present, the process is a martigale and in the opposite situation it is a local martingale?). What would happen if we have some proces $Y_t$ and our $X_t$ looks like that:



$X_t = X_0 + int_{0}^{t} f(Y_s) ds + int_0^t f(Y_s) dW_s$



I would love to read something more about those properties. I will appreciate any link/paper related to this topic.







probability stochastic-processes stochastic-calculus martingales stochastic-integrals






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share|cite|improve this question











share|cite|improve this question




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asked Jan 31 at 22:00









FNTEFNTE

1276




1276












  • $begingroup$
    What if $a_s=s$?
    $endgroup$
    – d.k.o.
    Jan 31 at 22:42












  • $begingroup$
    Your "first" process $X_t$ is a martingale iff $a:=0$.
    $endgroup$
    – saz
    Feb 1 at 7:10


















  • $begingroup$
    What if $a_s=s$?
    $endgroup$
    – d.k.o.
    Jan 31 at 22:42












  • $begingroup$
    Your "first" process $X_t$ is a martingale iff $a:=0$.
    $endgroup$
    – saz
    Feb 1 at 7:10
















$begingroup$
What if $a_s=s$?
$endgroup$
– d.k.o.
Jan 31 at 22:42






$begingroup$
What if $a_s=s$?
$endgroup$
– d.k.o.
Jan 31 at 22:42














$begingroup$
Your "first" process $X_t$ is a martingale iff $a:=0$.
$endgroup$
– saz
Feb 1 at 7:10




$begingroup$
Your "first" process $X_t$ is a martingale iff $a:=0$.
$endgroup$
– saz
Feb 1 at 7:10










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