Re: asymptotics
- To: mathgroup at smc.vnet.net
- Subject: [mg76692] Re: asymptotics
- From: dimitris <dimmechan at yahoo.com>
- Date: Sat, 26 May 2007 04:22:00 -0400 (EDT)
- References: <f33qsc$mc6$1@smc.vnet.net>
Andrzej and Jens thanks a lot for assistance!
Dimitris
/ dimitris :
> Sorry fellas if I ask something trivial
> but currently I can't find anything!
>
> In another CAS I took
>
> f:=asympt(exp(-y*sqrt(1+m^2*u^2)/m),u,5);
>
> / 2 1/2 2 2 1/2 2 2
> | y (m ) y y (m ) (-6 m + y )
> f := |1 - --------- + ------- - ----------------------
> | 3 4 2 7 3
> \ 2 m u 8 m u 48 m u
>
> 2 2 2 \ 2 1/2
> y (-24 m + y ) 1 | / y (m ) u
> + ---------------- + O(----)| / exp(-----------)
> 8 4 5 | / m
> 384 m u u /
>
> ff:=simplify(convert(f,polynom)) assuming m>0;
> ff := 1/384*exp(-
> y*u)*(384*m^8*u^4-192*y*m^6*u^3+48*y^2*m^4*u^2+48*y*m^4*u-8*y^3*m^2*u-24*y^2*m^2+y^4)/
> m^8/u^4
>
> In Mathematica I can't get the expansion in infinity
>
> In[113]:= Series[Exp[(-y)*(Sqrt[1 + m^2*u^2]/m)], {u, Infinity, 10}]
> Out[113]= E^(-((Sqrt[1 + m^2*u^2]*y)/m))
>
> What do I miss here?
>
> Thanks
> Dimitris