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Limit of characteristic functions


Martingale that converges almost surely to $-infty$.Help with a random walk problem.How to show the following characteristic function is positive definiteShow $Pxi_1+dots+xi_n=1=(sum_i=1^n lambda_i)Delta + O(Delta^2)$ (Shiryaev's Probability page 44)Functions of a random walk and martingalesConsistency in the definition of cross cumulantsLevy's theorem for characteristic functions.Is the running maximum of random walk a martingale?Approximating a multinomial as $p(xi_1,ldots,xi_N)proptoexpleft(-fracn2sum_i=1^Nfrac(xi_i-p_i)^2p_iright)$Proving Chebyshev inequality













1












$begingroup$


Let $xi_1 ... , xi_n$ be iid with $E xi_i^2 < infty $
what is $$ lim _nrightarrow infty varphi_barxi$$
where $varphi$ is the caracteristic function and $barxi$ the mean of all the $xi_i$.



I don't know how to solve this, can someone help me please.



solutioin (?): $varphi_barxi(t) = varphi_xi(t/n)^n = left[ 1 + i mu fractn + O(fractn)right]^n = e^itmu$. By taylor expansion where $mu$ is the mean of $xi_i$.
Have I missed something?










share|cite|improve this question











$endgroup$











  • $begingroup$
    Do you know the central limit theorem?
    $endgroup$
    – Nate Eldredge
    Jun 14 '13 at 13:20















1












$begingroup$


Let $xi_1 ... , xi_n$ be iid with $E xi_i^2 < infty $
what is $$ lim _nrightarrow infty varphi_barxi$$
where $varphi$ is the caracteristic function and $barxi$ the mean of all the $xi_i$.



I don't know how to solve this, can someone help me please.



solutioin (?): $varphi_barxi(t) = varphi_xi(t/n)^n = left[ 1 + i mu fractn + O(fractn)right]^n = e^itmu$. By taylor expansion where $mu$ is the mean of $xi_i$.
Have I missed something?










share|cite|improve this question











$endgroup$











  • $begingroup$
    Do you know the central limit theorem?
    $endgroup$
    – Nate Eldredge
    Jun 14 '13 at 13:20













1












1








1





$begingroup$


Let $xi_1 ... , xi_n$ be iid with $E xi_i^2 < infty $
what is $$ lim _nrightarrow infty varphi_barxi$$
where $varphi$ is the caracteristic function and $barxi$ the mean of all the $xi_i$.



I don't know how to solve this, can someone help me please.



solutioin (?): $varphi_barxi(t) = varphi_xi(t/n)^n = left[ 1 + i mu fractn + O(fractn)right]^n = e^itmu$. By taylor expansion where $mu$ is the mean of $xi_i$.
Have I missed something?










share|cite|improve this question











$endgroup$




Let $xi_1 ... , xi_n$ be iid with $E xi_i^2 < infty $
what is $$ lim _nrightarrow infty varphi_barxi$$
where $varphi$ is the caracteristic function and $barxi$ the mean of all the $xi_i$.



I don't know how to solve this, can someone help me please.



solutioin (?): $varphi_barxi(t) = varphi_xi(t/n)^n = left[ 1 + i mu fractn + O(fractn)right]^n = e^itmu$. By taylor expansion where $mu$ is the mean of $xi_i$.
Have I missed something?







probability-theory characteristic-functions probability-limit-theorems






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jun 14 '13 at 21:39









Davide Giraudo

128k17156268




128k17156268










asked Jun 14 '13 at 12:18









MartaMarta

62




62











  • $begingroup$
    Do you know the central limit theorem?
    $endgroup$
    – Nate Eldredge
    Jun 14 '13 at 13:20
















  • $begingroup$
    Do you know the central limit theorem?
    $endgroup$
    – Nate Eldredge
    Jun 14 '13 at 13:20















$begingroup$
Do you know the central limit theorem?
$endgroup$
– Nate Eldredge
Jun 14 '13 at 13:20




$begingroup$
Do you know the central limit theorem?
$endgroup$
– Nate Eldredge
Jun 14 '13 at 13:20










1 Answer
1






active

oldest

votes


















0












$begingroup$

No, you didn't miss anything. What you proved is that $barxi_n$ converges in law to the constant $mu$. We can deduce from that that there is convergence in probability to this constant, which is nothing but weak law of large numbers.






share|cite|improve this answer









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    1 Answer
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    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

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    active

    oldest

    votes









    0












    $begingroup$

    No, you didn't miss anything. What you proved is that $barxi_n$ converges in law to the constant $mu$. We can deduce from that that there is convergence in probability to this constant, which is nothing but weak law of large numbers.






    share|cite|improve this answer









    $endgroup$

















      0












      $begingroup$

      No, you didn't miss anything. What you proved is that $barxi_n$ converges in law to the constant $mu$. We can deduce from that that there is convergence in probability to this constant, which is nothing but weak law of large numbers.






      share|cite|improve this answer









      $endgroup$















        0












        0








        0





        $begingroup$

        No, you didn't miss anything. What you proved is that $barxi_n$ converges in law to the constant $mu$. We can deduce from that that there is convergence in probability to this constant, which is nothing but weak law of large numbers.






        share|cite|improve this answer









        $endgroup$



        No, you didn't miss anything. What you proved is that $barxi_n$ converges in law to the constant $mu$. We can deduce from that that there is convergence in probability to this constant, which is nothing but weak law of large numbers.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jun 14 '13 at 21:38









        Davide GiraudoDavide Giraudo

        128k17156268




        128k17156268



























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