Burkholder's inequality on $[s,t]$











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Let $T>0$, $F$ be an adapted squared-integrable process and $pge 2$, then the Burkholder's inequality implies
$$
Ebigg(bigg|int_0^T F(s)dB(s)bigg|^pbigg)le C(p) Ebigg[bigg(int_0^T F^2(s)dsbigg)^{p/2}bigg],
$$

for some constant $C(p)$.



I was wondering why most textbooks present the inequality from $[0,T]$, instead of any subinterval $[s,t]subset[0,T]$. I follow the proof and I didn't notice any technical difficulty to extend the result to the integral on $[s,t]$:
$$
Ebigg(bigg|int_s^t F(r)dB(r)bigg|^pbigg)le C(p) Ebigg[bigg(int_s^t F^2(r)drbigg)^{p/2}bigg].
$$

Did I overlook anything? Or the result on $[s,t]$ is a simple consequence of the result on $[0,t]$?



Similarly, I was wondering whether the $L^p$ estimate of Levy integral:
$$Ebigg(bigg|int_0^Tint_E F(s)dtilde{N}(ds,de)bigg|^pbigg),$$
the so-called Kunita's inequality, works on arbitrary fixed finite interval $[s,t]$.










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  • 1




    The inequality for subintervals $[s,t]$ is indeed a direct and simple consequence of the result on $[0,T]$; simply apply the inequality on $[0,T]$ to the truncated function $tilde{F}(r) := F(r) 1_{[s,t]}(r)$.
    – saz
    Nov 14 at 15:25










  • @saz Thank you very much. How stupid of I!
    – John
    Nov 14 at 15:34















up vote
0
down vote

favorite












Let $T>0$, $F$ be an adapted squared-integrable process and $pge 2$, then the Burkholder's inequality implies
$$
Ebigg(bigg|int_0^T F(s)dB(s)bigg|^pbigg)le C(p) Ebigg[bigg(int_0^T F^2(s)dsbigg)^{p/2}bigg],
$$

for some constant $C(p)$.



I was wondering why most textbooks present the inequality from $[0,T]$, instead of any subinterval $[s,t]subset[0,T]$. I follow the proof and I didn't notice any technical difficulty to extend the result to the integral on $[s,t]$:
$$
Ebigg(bigg|int_s^t F(r)dB(r)bigg|^pbigg)le C(p) Ebigg[bigg(int_s^t F^2(r)drbigg)^{p/2}bigg].
$$

Did I overlook anything? Or the result on $[s,t]$ is a simple consequence of the result on $[0,t]$?



Similarly, I was wondering whether the $L^p$ estimate of Levy integral:
$$Ebigg(bigg|int_0^Tint_E F(s)dtilde{N}(ds,de)bigg|^pbigg),$$
the so-called Kunita's inequality, works on arbitrary fixed finite interval $[s,t]$.










share|cite|improve this question




















  • 1




    The inequality for subintervals $[s,t]$ is indeed a direct and simple consequence of the result on $[0,T]$; simply apply the inequality on $[0,T]$ to the truncated function $tilde{F}(r) := F(r) 1_{[s,t]}(r)$.
    – saz
    Nov 14 at 15:25










  • @saz Thank you very much. How stupid of I!
    – John
    Nov 14 at 15:34













up vote
0
down vote

favorite









up vote
0
down vote

favorite











Let $T>0$, $F$ be an adapted squared-integrable process and $pge 2$, then the Burkholder's inequality implies
$$
Ebigg(bigg|int_0^T F(s)dB(s)bigg|^pbigg)le C(p) Ebigg[bigg(int_0^T F^2(s)dsbigg)^{p/2}bigg],
$$

for some constant $C(p)$.



I was wondering why most textbooks present the inequality from $[0,T]$, instead of any subinterval $[s,t]subset[0,T]$. I follow the proof and I didn't notice any technical difficulty to extend the result to the integral on $[s,t]$:
$$
Ebigg(bigg|int_s^t F(r)dB(r)bigg|^pbigg)le C(p) Ebigg[bigg(int_s^t F^2(r)drbigg)^{p/2}bigg].
$$

Did I overlook anything? Or the result on $[s,t]$ is a simple consequence of the result on $[0,t]$?



Similarly, I was wondering whether the $L^p$ estimate of Levy integral:
$$Ebigg(bigg|int_0^Tint_E F(s)dtilde{N}(ds,de)bigg|^pbigg),$$
the so-called Kunita's inequality, works on arbitrary fixed finite interval $[s,t]$.










share|cite|improve this question















Let $T>0$, $F$ be an adapted squared-integrable process and $pge 2$, then the Burkholder's inequality implies
$$
Ebigg(bigg|int_0^T F(s)dB(s)bigg|^pbigg)le C(p) Ebigg[bigg(int_0^T F^2(s)dsbigg)^{p/2}bigg],
$$

for some constant $C(p)$.



I was wondering why most textbooks present the inequality from $[0,T]$, instead of any subinterval $[s,t]subset[0,T]$. I follow the proof and I didn't notice any technical difficulty to extend the result to the integral on $[s,t]$:
$$
Ebigg(bigg|int_s^t F(r)dB(r)bigg|^pbigg)le C(p) Ebigg[bigg(int_s^t F^2(r)drbigg)^{p/2}bigg].
$$

Did I overlook anything? Or the result on $[s,t]$ is a simple consequence of the result on $[0,t]$?



Similarly, I was wondering whether the $L^p$ estimate of Levy integral:
$$Ebigg(bigg|int_0^Tint_E F(s)dtilde{N}(ds,de)bigg|^pbigg),$$
the so-called Kunita's inequality, works on arbitrary fixed finite interval $[s,t]$.







stochastic-calculus stochastic-integrals stochastic-analysis quadratic-variation






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edited Nov 14 at 15:22

























asked Nov 14 at 15:06









John

9,41411334




9,41411334








  • 1




    The inequality for subintervals $[s,t]$ is indeed a direct and simple consequence of the result on $[0,T]$; simply apply the inequality on $[0,T]$ to the truncated function $tilde{F}(r) := F(r) 1_{[s,t]}(r)$.
    – saz
    Nov 14 at 15:25










  • @saz Thank you very much. How stupid of I!
    – John
    Nov 14 at 15:34














  • 1




    The inequality for subintervals $[s,t]$ is indeed a direct and simple consequence of the result on $[0,T]$; simply apply the inequality on $[0,T]$ to the truncated function $tilde{F}(r) := F(r) 1_{[s,t]}(r)$.
    – saz
    Nov 14 at 15:25










  • @saz Thank you very much. How stupid of I!
    – John
    Nov 14 at 15:34








1




1




The inequality for subintervals $[s,t]$ is indeed a direct and simple consequence of the result on $[0,T]$; simply apply the inequality on $[0,T]$ to the truncated function $tilde{F}(r) := F(r) 1_{[s,t]}(r)$.
– saz
Nov 14 at 15:25




The inequality for subintervals $[s,t]$ is indeed a direct and simple consequence of the result on $[0,T]$; simply apply the inequality on $[0,T]$ to the truncated function $tilde{F}(r) := F(r) 1_{[s,t]}(r)$.
– saz
Nov 14 at 15:25












@saz Thank you very much. How stupid of I!
– John
Nov 14 at 15:34




@saz Thank you very much. How stupid of I!
– John
Nov 14 at 15:34















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