<br><div class="gmail_quote"><div class="gmail_quote"><div class="gmail_quote"><div><div><div class="gmail_quote"><div class="gmail_quote"><div class="gmail_quote"><div class="gmail_quote"><div class="gmail_quote"><div class="gmail_quote">

                   BINGHAMTON GEOMETRY/TOPOLOGY SEMINAR<br><div class="gmail_quote"><div class="gmail_quote"><div class="gmail_quote"><div class="gmail_quote">
<div class="gmail_quote">

<div class="gmail_quote">

<div class="gmail_quote">
<div class="gmail_quote">
<br><i>Date:</i>  Thursday, Nov 17, 2011<div><br>


<i>Time:</i>  2:50-3:50pm<br><i>Place:</i>  Library North 2205 followed by coffee/tea in the Anderson Reading Room.<br>

 <br>
</div><i>Speaker:</i> Tim Riley (Cornell University)<br><i>Title: </i>Hydra groups<i><br><br>Abstract:</i>  
I will describe some wild geometry that arises in an apparently benign group theoretic setting: 
I will exhibit a family of groups that are CAT(0), bi-automatic, 1-relator, and free-by-cyclic, 
and yet have free subgroups of huge (Ackermannian) distortion.   I will show how these lead to 
examples of hyperbolic groups with finite-rank free subgroups of similarly huge distortion.  The 
origin of the extreme behaviour lies in a simple computational game - a realisation of Hercules&#39; 
battle with the hydra, played out in manipulations of strings of letters.   
    </div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div>