Age

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These are questions asked by Age

Hi,

I've noticed there are settings to set the type of index for spinors or gauge index in the physics package. i.e Setup(spinorindices=lowercaselatin). I also notice there is a setting for specifying the form of tetrads. 

I cannot find any further documention or examples on how to use these functions. Could anyone point me in the direction of a text or help function as to how these are implemented. 

Simple examples of things I am trying to do:

> with(Physics); Setup(spinorindices=lowercaselatin, metric = <some_line_element>)

> tetrad[`mu`,`~a`] = Matrix(<some tetrad matrix>) 

> Define(%)

I recieve the following error: invalid input: unknown uses a 2nd argument, a, which is missing.

I am hoping for a tensor that uses the metric to raise/lower the `mu` component and the minkowskian metric to raise/lower the `a` component. 

If there is further documentation that I am missing, I'm happy to check that out instead of asking lots of questions here. 

Thanks again.

Hi,

This may be just my lack of maple syntax, however I cannot seem to find a way to add upper indicies in tensors (without first converting them to some other object, array, matrix etc)

In the physics package an example is just the metric tensor. 

I am trying to do something like this:

 

with(Physics);

add(g_[~mu,2], mu=1..2) 

Is there an easy way of summing upper indicies? Obviously lower indicies work, because the add/sum command recognizes the variable to iterate. 

Thanks in advance,

Age

 

Hi, 

I'm trying to set up the dirac algebra using the Physics package in maple 18. There are dirac gamma matricies (Dgamma) already specified, but I can't seem to manipulate their commutation relations. 

So I've tried building my own: 

restart;
with(Physics);

Setup(noncommutativeprefix = {gamma});

g[1] := gamma[1]; g[2] := gamma[2]; g[3] := gamma[3]; g[4] := gamma[0];

InverseMetric := rhs(g_[`~mu`, `~nu`, matrix])

Algebra :=  (a, b) -> %AntiCommutator(g[a], g[b]) = 2*InverseMetric[a, b];

Rules := Matrix(4, 4, Algebra);

Setup(algebrarules = Rules);

Error, (in Physics:-Setup) unable to set AntiCommutator(gamma[0], gamma[1]) = 0 because, taking into account {AntiCommutator(gamma[0], gamma[0]) = 2}, we would have gamma[0] and gamma[0] anticommutative and AntiCommutator(gamma[0], gamma[0]) <> 0

It seems like Maple can't handle the Dirac Algebra? Or have I done something obviously wrong?

Any help is appreciated. 

Thanks

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