Owen -

  An interesting paper on some of these issues (you may recognize the author 
:-) :

  http://eprints.kfupm.edu.sa/36302/1/36302.pdf

  But, possibly more fun:

  
http://books.google.com/books?id=XW7fICYtkg8C&pg=PA223&lpg=PA223&dq=spaghetti+dewdney&source=bl&ots=fXNU7klBKJ&sig=z3hibL7KkO-WG1ewPLzfNn9HmxU&hl=en&ei=7wqrS9-oNIT6sgPsj_TPDQ&sa=X&oi=book_result&ct=result&resnum=2&ved=0CAkQ6AEwAQ#v=onepage&q=&f=false

   (if that link is too messy, google  spaghetti dewdney , and click the google 
books link for The (new) Turing omnibus)

  Some exercises:

  1.)  Design a device to find the maximum of a set of real numbers in 1 step.  
(hint:  spaghetti)

  2.)  Find the maximum length path in a tree in 2 steps.

  3.)  Evaluate the validity of this algorithm for finding the maximum (no 
loops) path between two given vertices in a connected graph:

        a.  Make the graph out of string/wire (see Dewdney . . .)

        b.  Hold the two vertices, one in each hand, and pull taut.  Cut one 
(taut) link that doesn't separate the graph.

        c.  Repeat step b. until there are no more links that can be cut 
without separating the graph.

        d.  The remaining taut line between the two vertices is the desired 
path.   (or is it???)

        Note:  How can you make sure that cutting a particular link doesn't 
separate the graph?  (hint:   wire . . . :-)



  For the more philosophically inclined:

  http://homepages.ipact.nl/~lokhorst/hypercomputationUCL.pdf

  And, a reference link for the future:

  http://www.mdpi.com/journal/computers/special_issues/analogcomp

tom

On Mar 24, 2010, at 9:25 PM, Owen Densmore wrote:

> In our Mathematical Thinking seminar (on computer science) today, the topic 
> of Analog computing came up.
> 
> Do we have a good foundational approach to analog computing?  For example, 
> analog automata, computational theory on decidability for analog computers, a 
> notion of analog computational complexity?
> 
>    -- Owen
> 
> 
> 
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