       Re: preclude mathematical meaning of OverBar etc

• To: mathgroup at smc.vnet.net
• Subject: [mg67402] Re: preclude mathematical meaning of OverBar etc
• From: Peter Pein <petsie at dordos.net>
• Date: Thu, 22 Jun 2006 06:21:17 -0400 (EDT)
• References: <e7aos7\$922\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Martin Schoenecker schrieb:
> Dear group,
>
> I would like to use OverBar, SuperStar etc. to define characteristic or
> modified values for the same, "plain" variable.  Unfortunately, as every
> expression, they become a mathematical meaning which is not what I
> intend, e.g. for a substitution:
>
> test
>
> In:=
> subsfun = u -> Function[{x, t},
>      OverHat[l]*OverTilde[u][
>        OverTilde[x][x], OverTilde[t][
>         t]]]
> subsvar = OverTilde[t] ->
>     Function[t, t/OverHat[t]]
> resubsvar = t/OverHat[t] ->
>     OverTilde[t]
>
> Out=
> u -> Function[{x, t}, OverHat[l]*
>      OverTilde[u][OverTilde[x][x],
>       OverTilde[t][t]]]
>
> Out=
> OverTilde[t] -> Function[t,
>     t/OverHat[t]]
>
> Out=
> t/OverHat[t] -> OverTilde[t]
>
> In:=
> D[u[x, t], t]
> % /. subsfun
> % /. subsvar
> % /. resubsvar
>
> Out=
> Derivative[0, 1][u][x, t]
>
> Out=
> OverHat[l]*Derivative[
>      OverTilde[t]][t]*
>    Derivative[0, 1][OverTilde[u]][
>     OverTilde[x][x], OverTilde[t][t]]
>
> Out=
> OverHat[l]*(1/OverHat[t] -
>     (t*Derivative[OverHat][t])/
>      OverHat[t]^2)*
>    Derivative[0, 1][OverTilde[u]][
>     OverTilde[x][x], t/OverHat[t]]
>
> Out=
> OverHat[l]*(1/OverHat[t] -
>     (t*Derivative[OverHat][t])/
>      OverHat[t]^2)*
>    Derivative[0, 1][OverTilde[u]][
>     OverTilde[x][x], OverTilde[t]]
>
> where I get the derivative of the OverHat term, which is not desired.
> How to overcome this?  Is there another possibility than to use
> Symbolize with Utilities`Notation`?  Thanks for any hints,
>
> Martin
>
Hi Martin,

either do a SetAttributes[#,Constant]&/@{OverHat,OverBar} before calling D[] or use Dt with option Constants:

Dt[u[x, t] /. subsfun /. subsvar, t, Constants ->
{x, OverTilde, OverHat}] /. resubsvar

(OverHat[l]*Derivative[0, 1][OverTilde[u]][OverTilde[x][x], OverTilde[t]])/OverHat[t]

```

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