I am tyring to simulate the intensity autocorrelation of a femtosecond laser pulse.   The pulse intensity is set up as a 4096 point Vector of real values using a sech function for the pulse shape (see below). 

Being that it's the intensity, not the complex field, of the laser pulse, it is always real-valued and positive.    Therefore, the autocorrelation of the pulse intensity should be positive at all points in time.   But in fact, when I use the AutoCorrelation command on this Vector, it results many negative-valued points (see below).

What is going on?   Why am I getting negative values?

Thanks!

-Gregg-

I have a series of 5681 points that lie on the unit sphere.  These were generated by a simulation in another software package (I plat to use Maple for this in the future).  But anyway, I'm stuck on plotting right now.    The pointplot3d  command plots them all at once.   I want to slow this down and see them plotted sequentially in time, adding a new point at each time increment.    It would be like watching a zipper or a string of yarn being wound onto a ball.   It doesn't seem like the usual animation controls allow me to do this.  Hope that description makes sense.

Ball_of_yarn.mw

Ball_of_yarn.mw

Ball_of_yarn.mw

I am doing the first interactive plot in Tutorial 9:  Dynamic Applications.    The first part is Exploration Assistant.   This is mostly going OK but I don't want to have it rescale the y-axis to the data extents.   So I uncheck the box and type in my min & max values as shown below.    But when I drag the slider for coefficient a or b, the plot reverts back to using data extents.   How do I override this so that the axis range stays fixed when I drag the sliders?

I work with polarization in optical fibers.  I want to (theoretically) scramble the polarization and cover the entire Poincare sphere with several thousand points using a sequence of two variable retarders.   So looking at the Mueller matrices in the attached image, as I vary the arguments of the sin & cosines, I’d like to see the polarization states traced out on the Poincare sphere.    Has this already been done in Maple, as in some kind of canned routine or add-on module?

Thanks!