## Robert Harlander

 phone: +49-241-80-27045 fax: +49-241-80-22187 harlander(at)physik.rwth-aachen.de Büro: 28A414, Campus Melaten

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[Up: aximate]

## Feynman diagrams

 A Feynman diagram describes a reaction of elementary particles. For example, two electrons scattering by exchanging a photon. The new feature required here is that the aximation is not continuous, but splits into different parts: two electrons coming in, one emitting a photon, the other absorbing it, two electrons going out. This division of the aximation can be achieved with the interval option as follows: the movie is always 100 time units (let's call them axoseconds) long. interval specifies in which time slot an object should evolve from its start to its end, the so-called active interval. The scattering reaction mentioned above can then be represented as follows:  $plu = point({"type" => "empty", "coordinates" => [[-100,-50]]});$plo = point({"type" => "empty", "coordinates" => [[-100,50]]}); $p1 = point({"type" => "empty", "coordinates" => [[-20,20]]});$p2 = point({"type" => "empty", "coordinates" => [[20,-20]]}); $pro = point({"type" => "empty", "coordinates" => [[100,50]]});$pru = point({"type" => "empty", "coordinates" => [[100,-50]]}); line({"foot" => [${$plo}{"coordinates"}], "head" => [${$plo}{"coordinates"},${$p1}{"coordinates"}], "text" => "\$e^-\$", "textpos" => [[.5,15]], "color" => "Blue", "staythere" => 1, "interval" => [0,40]}); line({"foot" => [${$plu}{"coordinates"}], "head" => [${$plu}{"coordinates"},${$p2}{"coordinates"}], "textpos" => [[.5,15]], "text" => '$e^-$', "color" => "Green", "staythere" => 1, "interval" => [0,60]}); line({"foot" => [${$p2}{"coordinates"}], "head" => [${$p2}{"coordinates"},${$pru}{"coordinates"}], "staythere" => 1, "fixedwiggles" => 0, "text" => '$e^-$', "textpos" => [[.5,15]], "wiggles" => 25, "color" => "Green", "interval" => [60,100]}); line({"foot" => [${$p1}{"coordinates"}], "staythere" => 1, "text" => '$e^-$', "textpos" => [[.5,15]], "color" => "Blue", "head" => [${$p1}{"coordinates"},${$pro}{"coordinates"}], "interval" => [40,100]}); photon({"foot" => [${$p1}{"coordinates"}], "head" => [${$p1}{"coordinates"},${$p2}{"coordinates"}], "color" => "Red", "fixedwiggles" => 0, "text" => '$\gamma$', "textpos" => [[.5,20]], "wiggles" => 25, "staythere" => 1, "interval" => [40,60]}); point({"coordinates" => [${$plo}{"coordinates"}, ${$p1}{"coordinates"}], "type" => "ccirc", "interval" => [0,40]}); point({"coordinates" => [${$plu}{"coordinates"}, ${$p2}{"coordinates"}], "type" => "ccirc", "interval" => [0,60]}); point({"coordinates" => [${$p1}{"coordinates"}, ${$p2}{"coordinates"}], "type" => "ccirc", "interval" => [40,60]}); point({"coordinates" => [${$p1}{"coordinates"}, ${$pro}{"coordinates"}], "type" => "ccirc", "interval" => [40,100]}); point({"coordinates" => [${$p2}{"coordinates"}, ${$pru}{"coordinates"}], "type" => "ccirc", "interval" => [60,100]});  Note also the options bethere/staythere which determine whether the object is already visible before/after its active interval or not (0 or 1). main
aximate:feynman (Robert Harlander)