# [Maxima] How to simplify kdelta?

Nicola Cabibbo nicola.cabibbo at roma1.infn.it
Fri Jun 13 13:53:03 CDT 2008

```Where (in which file) could I find the definition of ev?

Thanks,

Nicola Cabibbo

On Jun 12, 2008, at 1:26 PM, Viktor T. Toth wrote:

> The workings of ev() are mysterious. Basically, ev does the applying
> of
> kdelta before it evaluates lc2kdt, which is not what you want. This
> might
>
> 	ishow(apply(ev,[contract(expand(lc2kdt(expr))),kdelta]))\$
>
> By using apply(), you ensure that ev is applied only after its
> arguments
> have been evaluated.
>
> In many cases, though, it's much easier to just do the evaluation in
> two
> steps, as in
>
> 	contract(expand(lc2kdt(expr)))\$
> 	ishow(ev(%,kdelta))\$
>
>
> Viktor
>
>
> -----Original Message-----
> From: maxima-bounces at math.utexas.edu [mailto:maxima-bounces at math.utexas.edu
> ]
> On Behalf Of Nicola Cabibbo
> Sent: Thursday, June 12, 2008 7:18 AM
> To: maxima at math.utexas.edu
> Cc: Nicola Cabibbo
> Subject: Re: [Maxima] How to simplify kdelta?
>
> After more investigation, if after the commands
> 	if get('itensor, 'version)=false then load (itensor) ;
> 	idim(3);
> 	dim:3;
> 	defcon(q,q,qq);
> 	expr:'levi_civita([i,k,m],[])*'levi_civita([],[i1,k,m])*q([],
> [i])*q([i1],[])\$
> 	expr1:contract(expand(lc2kdt(expr)));
> I enter
> 	ishow(ev(expr1,kdelta));
> the result is the expected " 2qq ", while if I enter
> 	ishow(ev(contract(expand(lc2kdt(expr))),kdelta));
> the result is " 5*qq-kdelta*qq ". Why the difference?
>
> Thanks
>
>
> On Jun 12, 2008, at 1:12 PM, Nicola Cabibbo wrote:
>
>> Just trying to learn Maxima, with the commands:
>>
>> 	if get('itensor, 'version)=false then load (itensor) ;
>> 	idim(3);
>> 	dim:3;
>> 	defcon(q,q,qq);
>> 	expr:'levi_civita([i,k,m],[])*'levi_civita([],[i1,k,m])*q([],
>> [i])*q([i1],[])\$
>> 	ishow(contract(expand(lc2kdt(expr))));
>>
>> I obtain " 5*qq-kdelta*qq ". This is correct with kdelta=3, but
>> how can I directly obtain the simplified result "2 qq"?
>>
>> Thanks for the attention
>>
>> PS: my setup is (on a Mac)
>>
>> wxMaxima 0.7.5 http://wxmaxima.sourceforge.net
>> Maxima 5.15.0 http://maxima.sourceforge.net
>> Using Lisp CMU Common Lisp Snapshot 2008-03 (19E)
>>
>>
>>
>>
>>
>>
> _______________________________________________
> Maxima mailing list
> Maxima at math.utexas.edu
> http://www.math.utexas.edu/mailman/listinfo/maxima
>
```