Inequality for exponential sum

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I'm currently trying to figure out the following inequality. It looks like an inequality for the exponential sum, but I can't verify it or find a source explaining it any further. Most likely it has to do with the remainder I guess...
$$|E[exp(itX_n,k)|F_n,k-1]-1-frac12t^2E[X_n,k^2|F_n,k-1]|\
leq frac16|t|^3E[|X_n,k|^3mathrm1_leq epsilonbigF_n,k-1]+t^2E[X_n,k^21_X_n,k>epsilon|F_n,k-1]$$



Where $E[X_n,k|F_n,k-1]=0$ for all $k,n in mathbbN$



Especially this is taken from
Dvoretzky, 1972, ASYMPTOTIC NORMALITY FOR SUMS OF DEPENDENT RANDOM VARIABLES
and can be found in the proof of theorem 2.1 equality (4.4). Thanks in advance.







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  • It looks like $e^itX_n,k$ has been expanded into a power series in $t$, and the error term after $t^2$ term is used.
    – herb steinberg
    Jul 23 at 21:49











  • Yeah but how does one obtain the Indicators?
    – DrShredz
    Jul 24 at 12:03










  • Please define what you mean by "indicators".
    – herb steinberg
    Jul 24 at 16:17










  • I meant the conditioning of both expectations on $leq epsilon $ respectively $$
    – DrShredz
    Jul 24 at 19:24















up vote
0
down vote

favorite












I'm currently trying to figure out the following inequality. It looks like an inequality for the exponential sum, but I can't verify it or find a source explaining it any further. Most likely it has to do with the remainder I guess...
$$|E[exp(itX_n,k)|F_n,k-1]-1-frac12t^2E[X_n,k^2|F_n,k-1]|\
leq frac16|t|^3E[|X_n,k|^3mathrm1_leq epsilonbigF_n,k-1]+t^2E[X_n,k^21_X_n,k>epsilon|F_n,k-1]$$



Where $E[X_n,k|F_n,k-1]=0$ for all $k,n in mathbbN$



Especially this is taken from
Dvoretzky, 1972, ASYMPTOTIC NORMALITY FOR SUMS OF DEPENDENT RANDOM VARIABLES
and can be found in the proof of theorem 2.1 equality (4.4). Thanks in advance.







share|cite|improve this question



















  • It looks like $e^itX_n,k$ has been expanded into a power series in $t$, and the error term after $t^2$ term is used.
    – herb steinberg
    Jul 23 at 21:49











  • Yeah but how does one obtain the Indicators?
    – DrShredz
    Jul 24 at 12:03










  • Please define what you mean by "indicators".
    – herb steinberg
    Jul 24 at 16:17










  • I meant the conditioning of both expectations on $leq epsilon $ respectively $$
    – DrShredz
    Jul 24 at 19:24













up vote
0
down vote

favorite









up vote
0
down vote

favorite











I'm currently trying to figure out the following inequality. It looks like an inequality for the exponential sum, but I can't verify it or find a source explaining it any further. Most likely it has to do with the remainder I guess...
$$|E[exp(itX_n,k)|F_n,k-1]-1-frac12t^2E[X_n,k^2|F_n,k-1]|\
leq frac16|t|^3E[|X_n,k|^3mathrm1_leq epsilonbigF_n,k-1]+t^2E[X_n,k^21_X_n,k>epsilon|F_n,k-1]$$



Where $E[X_n,k|F_n,k-1]=0$ for all $k,n in mathbbN$



Especially this is taken from
Dvoretzky, 1972, ASYMPTOTIC NORMALITY FOR SUMS OF DEPENDENT RANDOM VARIABLES
and can be found in the proof of theorem 2.1 equality (4.4). Thanks in advance.







share|cite|improve this question











I'm currently trying to figure out the following inequality. It looks like an inequality for the exponential sum, but I can't verify it or find a source explaining it any further. Most likely it has to do with the remainder I guess...
$$|E[exp(itX_n,k)|F_n,k-1]-1-frac12t^2E[X_n,k^2|F_n,k-1]|\
leq frac16|t|^3E[|X_n,k|^3mathrm1_leq epsilonbigF_n,k-1]+t^2E[X_n,k^21_X_n,k>epsilon|F_n,k-1]$$



Where $E[X_n,k|F_n,k-1]=0$ for all $k,n in mathbbN$



Especially this is taken from
Dvoretzky, 1972, ASYMPTOTIC NORMALITY FOR SUMS OF DEPENDENT RANDOM VARIABLES
and can be found in the proof of theorem 2.1 equality (4.4). Thanks in advance.









share|cite|improve this question










share|cite|improve this question




share|cite|improve this question









asked Jul 23 at 14:41









DrShredz

82




82











  • It looks like $e^itX_n,k$ has been expanded into a power series in $t$, and the error term after $t^2$ term is used.
    – herb steinberg
    Jul 23 at 21:49











  • Yeah but how does one obtain the Indicators?
    – DrShredz
    Jul 24 at 12:03










  • Please define what you mean by "indicators".
    – herb steinberg
    Jul 24 at 16:17










  • I meant the conditioning of both expectations on $leq epsilon $ respectively $$
    – DrShredz
    Jul 24 at 19:24

















  • It looks like $e^itX_n,k$ has been expanded into a power series in $t$, and the error term after $t^2$ term is used.
    – herb steinberg
    Jul 23 at 21:49











  • Yeah but how does one obtain the Indicators?
    – DrShredz
    Jul 24 at 12:03










  • Please define what you mean by "indicators".
    – herb steinberg
    Jul 24 at 16:17










  • I meant the conditioning of both expectations on $leq epsilon $ respectively $$
    – DrShredz
    Jul 24 at 19:24
















It looks like $e^itX_n,k$ has been expanded into a power series in $t$, and the error term after $t^2$ term is used.
– herb steinberg
Jul 23 at 21:49





It looks like $e^itX_n,k$ has been expanded into a power series in $t$, and the error term after $t^2$ term is used.
– herb steinberg
Jul 23 at 21:49













Yeah but how does one obtain the Indicators?
– DrShredz
Jul 24 at 12:03




Yeah but how does one obtain the Indicators?
– DrShredz
Jul 24 at 12:03












Please define what you mean by "indicators".
– herb steinberg
Jul 24 at 16:17




Please define what you mean by "indicators".
– herb steinberg
Jul 24 at 16:17












I meant the conditioning of both expectations on $leq epsilon $ respectively $$
– DrShredz
Jul 24 at 19:24





I meant the conditioning of both expectations on $leq epsilon $ respectively $$
– DrShredz
Jul 24 at 19:24











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Somebody on MO just pointed out to me that the inequality, especially the first term in the second line comes from the remainder in integral form of the corresponding Taylor series.






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    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    0
    down vote













    Somebody on MO just pointed out to me that the inequality, especially the first term in the second line comes from the remainder in integral form of the corresponding Taylor series.






    share|cite|improve this answer

























      up vote
      0
      down vote













      Somebody on MO just pointed out to me that the inequality, especially the first term in the second line comes from the remainder in integral form of the corresponding Taylor series.






      share|cite|improve this answer























        up vote
        0
        down vote










        up vote
        0
        down vote









        Somebody on MO just pointed out to me that the inequality, especially the first term in the second line comes from the remainder in integral form of the corresponding Taylor series.






        share|cite|improve this answer













        Somebody on MO just pointed out to me that the inequality, especially the first term in the second line comes from the remainder in integral form of the corresponding Taylor series.







        share|cite|improve this answer













        share|cite|improve this answer



        share|cite|improve this answer











        answered Jul 24 at 19:29









        DrShredz

        82




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