Laplace transform of complementary error function $operatorname{erfc}(1/sqrt{t})$- using infinite series
$begingroup$
The Laplace transform of the complementary error function $operatorname{erfc}left(frac{1}{sqrt{t}}right)$ is
$$Lleft{operatorname{erfc}left(frac{1}{sqrt{t}}right)right}=Lleft{1-operatorname{erf}left(frac{1}{sqrt{t}}right) right}$$
That is
$$begin{aligned}
Lleft{operatorname{erfc}left(frac{1}{sqrt{t}}right)right}
&=Lleft{1-frac{2}{sqrt{pi}} int_{0}^{1/sqrt{t}} e^{-x^2} dx right}\
&=Lleft{1-frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!} int_{0}^{1/sqrt{t}} x^{2n} dx right} \
&=Lleft{1-frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!(2n+1)} frac{1}{t^{n+1/2}} right} \
&=frac{1}{p} - frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!(2n+1)} Lleft{frac{1}{t^{n+1/2}} right} \
end{aligned}$$
After this step, I do not know how to proceed. Please help, if you know the procedure or if there is any mistake please point out. Thank you!
laplace-transform
$endgroup$
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$begingroup$
The Laplace transform of the complementary error function $operatorname{erfc}left(frac{1}{sqrt{t}}right)$ is
$$Lleft{operatorname{erfc}left(frac{1}{sqrt{t}}right)right}=Lleft{1-operatorname{erf}left(frac{1}{sqrt{t}}right) right}$$
That is
$$begin{aligned}
Lleft{operatorname{erfc}left(frac{1}{sqrt{t}}right)right}
&=Lleft{1-frac{2}{sqrt{pi}} int_{0}^{1/sqrt{t}} e^{-x^2} dx right}\
&=Lleft{1-frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!} int_{0}^{1/sqrt{t}} x^{2n} dx right} \
&=Lleft{1-frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!(2n+1)} frac{1}{t^{n+1/2}} right} \
&=frac{1}{p} - frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!(2n+1)} Lleft{frac{1}{t^{n+1/2}} right} \
end{aligned}$$
After this step, I do not know how to proceed. Please help, if you know the procedure or if there is any mistake please point out. Thank you!
laplace-transform
$endgroup$
add a comment |
$begingroup$
The Laplace transform of the complementary error function $operatorname{erfc}left(frac{1}{sqrt{t}}right)$ is
$$Lleft{operatorname{erfc}left(frac{1}{sqrt{t}}right)right}=Lleft{1-operatorname{erf}left(frac{1}{sqrt{t}}right) right}$$
That is
$$begin{aligned}
Lleft{operatorname{erfc}left(frac{1}{sqrt{t}}right)right}
&=Lleft{1-frac{2}{sqrt{pi}} int_{0}^{1/sqrt{t}} e^{-x^2} dx right}\
&=Lleft{1-frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!} int_{0}^{1/sqrt{t}} x^{2n} dx right} \
&=Lleft{1-frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!(2n+1)} frac{1}{t^{n+1/2}} right} \
&=frac{1}{p} - frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!(2n+1)} Lleft{frac{1}{t^{n+1/2}} right} \
end{aligned}$$
After this step, I do not know how to proceed. Please help, if you know the procedure or if there is any mistake please point out. Thank you!
laplace-transform
$endgroup$
The Laplace transform of the complementary error function $operatorname{erfc}left(frac{1}{sqrt{t}}right)$ is
$$Lleft{operatorname{erfc}left(frac{1}{sqrt{t}}right)right}=Lleft{1-operatorname{erf}left(frac{1}{sqrt{t}}right) right}$$
That is
$$begin{aligned}
Lleft{operatorname{erfc}left(frac{1}{sqrt{t}}right)right}
&=Lleft{1-frac{2}{sqrt{pi}} int_{0}^{1/sqrt{t}} e^{-x^2} dx right}\
&=Lleft{1-frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!} int_{0}^{1/sqrt{t}} x^{2n} dx right} \
&=Lleft{1-frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!(2n+1)} frac{1}{t^{n+1/2}} right} \
&=frac{1}{p} - frac{2}{sqrt{pi}} sum_{n=0}^{infty} frac{(-1)^n}{n!(2n+1)} Lleft{frac{1}{t^{n+1/2}} right} \
end{aligned}$$
After this step, I do not know how to proceed. Please help, if you know the procedure or if there is any mistake please point out. Thank you!
laplace-transform
laplace-transform
edited Aug 22 '16 at 1:29
Bungo
13.7k22148
13.7k22148
asked Aug 22 '16 at 1:08
Venkatesan MurugesanVenkatesan Murugesan
913
913
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1 Answer
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$begingroup$
It looks fine. Now you just have to exploit
$$mathcal{L}(1)=frac{1}{s},qquad mathcal{L}left(frac{1}{t^{n+1/2}}right) = s^{n-frac{1}{2}}Gammaleft(frac{1}{2}-nright)=s^{n-frac{1}{2}}(-1)^nfrac{2^nsqrt{pi}}{(2n-1)!!}. $$
Anyway, It would have been faster to exploit the properties of the Laplace transform. $text{Erfc}$ is defined by an integral, and through a change of variable it is not difficult to check that
$$ mathcal{L}left(text{Erfc}left(frac{1}{sqrt{t}}right)right) = color{red}{frac{e^{-2sqrt{s}}}{s}}. $$
$endgroup$
1
$begingroup$
Sir, I have obtained the result by exploiting the properties of the Laplace transform. However, my interest is to get the Laplace transform using infinite series of $operatorname{erfc}left(frac{1}{sqrt{t}}right)$. I have used the result as suggested by you. But I didn't get the required result. Please help if possible. –
$endgroup$
– Venkatesan Murugesan
Aug 22 '16 at 15:52
add a comment |
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$begingroup$
It looks fine. Now you just have to exploit
$$mathcal{L}(1)=frac{1}{s},qquad mathcal{L}left(frac{1}{t^{n+1/2}}right) = s^{n-frac{1}{2}}Gammaleft(frac{1}{2}-nright)=s^{n-frac{1}{2}}(-1)^nfrac{2^nsqrt{pi}}{(2n-1)!!}. $$
Anyway, It would have been faster to exploit the properties of the Laplace transform. $text{Erfc}$ is defined by an integral, and through a change of variable it is not difficult to check that
$$ mathcal{L}left(text{Erfc}left(frac{1}{sqrt{t}}right)right) = color{red}{frac{e^{-2sqrt{s}}}{s}}. $$
$endgroup$
1
$begingroup$
Sir, I have obtained the result by exploiting the properties of the Laplace transform. However, my interest is to get the Laplace transform using infinite series of $operatorname{erfc}left(frac{1}{sqrt{t}}right)$. I have used the result as suggested by you. But I didn't get the required result. Please help if possible. –
$endgroup$
– Venkatesan Murugesan
Aug 22 '16 at 15:52
add a comment |
$begingroup$
It looks fine. Now you just have to exploit
$$mathcal{L}(1)=frac{1}{s},qquad mathcal{L}left(frac{1}{t^{n+1/2}}right) = s^{n-frac{1}{2}}Gammaleft(frac{1}{2}-nright)=s^{n-frac{1}{2}}(-1)^nfrac{2^nsqrt{pi}}{(2n-1)!!}. $$
Anyway, It would have been faster to exploit the properties of the Laplace transform. $text{Erfc}$ is defined by an integral, and through a change of variable it is not difficult to check that
$$ mathcal{L}left(text{Erfc}left(frac{1}{sqrt{t}}right)right) = color{red}{frac{e^{-2sqrt{s}}}{s}}. $$
$endgroup$
1
$begingroup$
Sir, I have obtained the result by exploiting the properties of the Laplace transform. However, my interest is to get the Laplace transform using infinite series of $operatorname{erfc}left(frac{1}{sqrt{t}}right)$. I have used the result as suggested by you. But I didn't get the required result. Please help if possible. –
$endgroup$
– Venkatesan Murugesan
Aug 22 '16 at 15:52
add a comment |
$begingroup$
It looks fine. Now you just have to exploit
$$mathcal{L}(1)=frac{1}{s},qquad mathcal{L}left(frac{1}{t^{n+1/2}}right) = s^{n-frac{1}{2}}Gammaleft(frac{1}{2}-nright)=s^{n-frac{1}{2}}(-1)^nfrac{2^nsqrt{pi}}{(2n-1)!!}. $$
Anyway, It would have been faster to exploit the properties of the Laplace transform. $text{Erfc}$ is defined by an integral, and through a change of variable it is not difficult to check that
$$ mathcal{L}left(text{Erfc}left(frac{1}{sqrt{t}}right)right) = color{red}{frac{e^{-2sqrt{s}}}{s}}. $$
$endgroup$
It looks fine. Now you just have to exploit
$$mathcal{L}(1)=frac{1}{s},qquad mathcal{L}left(frac{1}{t^{n+1/2}}right) = s^{n-frac{1}{2}}Gammaleft(frac{1}{2}-nright)=s^{n-frac{1}{2}}(-1)^nfrac{2^nsqrt{pi}}{(2n-1)!!}. $$
Anyway, It would have been faster to exploit the properties of the Laplace transform. $text{Erfc}$ is defined by an integral, and through a change of variable it is not difficult to check that
$$ mathcal{L}left(text{Erfc}left(frac{1}{sqrt{t}}right)right) = color{red}{frac{e^{-2sqrt{s}}}{s}}. $$
answered Aug 22 '16 at 1:26
Jack D'AurizioJack D'Aurizio
290k33282662
290k33282662
1
$begingroup$
Sir, I have obtained the result by exploiting the properties of the Laplace transform. However, my interest is to get the Laplace transform using infinite series of $operatorname{erfc}left(frac{1}{sqrt{t}}right)$. I have used the result as suggested by you. But I didn't get the required result. Please help if possible. –
$endgroup$
– Venkatesan Murugesan
Aug 22 '16 at 15:52
add a comment |
1
$begingroup$
Sir, I have obtained the result by exploiting the properties of the Laplace transform. However, my interest is to get the Laplace transform using infinite series of $operatorname{erfc}left(frac{1}{sqrt{t}}right)$. I have used the result as suggested by you. But I didn't get the required result. Please help if possible. –
$endgroup$
– Venkatesan Murugesan
Aug 22 '16 at 15:52
1
1
$begingroup$
Sir, I have obtained the result by exploiting the properties of the Laplace transform. However, my interest is to get the Laplace transform using infinite series of $operatorname{erfc}left(frac{1}{sqrt{t}}right)$. I have used the result as suggested by you. But I didn't get the required result. Please help if possible. –
$endgroup$
– Venkatesan Murugesan
Aug 22 '16 at 15:52
$begingroup$
Sir, I have obtained the result by exploiting the properties of the Laplace transform. However, my interest is to get the Laplace transform using infinite series of $operatorname{erfc}left(frac{1}{sqrt{t}}right)$. I have used the result as suggested by you. But I didn't get the required result. Please help if possible. –
$endgroup$
– Venkatesan Murugesan
Aug 22 '16 at 15:52
add a comment |
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