SMS scnews item created by Gareth White at Tue 10 Mar 2009 1708
Type: Seminar
Distribution: World
Expiry: 11 Mar 2009
Calendar1: 11 Mar 2009 1300-1400
CalLoc1: Carslaw 452

SUMS Meeting: Guo -- Farey Fractions

Hello SUMS members, Welcome to Sydney University Maths Society for 2009 !!! Thankyou to
everybody for signing up during O-Week.  Thanks especially to those people who signed up
without me having to blackmail them.  Free will is always the preferred option :) 

In the past, SUMS usually ran weekly talks, occasionally holding other events.  We still
plan on having talks, however we will likely be increasing the frequency of the "other
events" component.  These "other events" will include soccer games, cake bakes, maths
relays, debates (everyone loves maths debating, right???), puzzle days, concerts, and
anything else that the executives come up with.  In fact, if you guys have any
suggestions as to things that we can do (including topics for maths talks, or talks that
YOU want to give), feel free to email us and we might consider them for later in the

Anyway, our first meeting this year will be this Wednesday, March 11.  We will be having
a talk, however there should also be time remaining afterwards for members to greet and
chat to each other, and talk about their love of maths.  We might even do that before
the talk.  As was mentioned in O-Week, you don’t have to be good at maths or even doing
maths at uni to attend these talks, so long as you enjoy maths, you will enjoy SUMS and
the talk won’t go over your head.  Our first speaker will be PhD student extraordinaire
Ivan Guo, and he will be talking about Farey Fractions and Ford Circles.  Now usually
this is where we provide an abstract of the talk, but Ivan is to lazy to do that (thanks
Ivan), so here’s wikipedia to save the day: 

 In mathematics, a Ford Circle is a circle with centre at (p/q, 1/(2q2)) and radius
1/(2q2), where p/q is an irreducible fraction, i.e.  p and q are coprime integers.  The
Ford circle associated with the fraction p/q is denoted by C[p/q] or C[p, q].  If p/q is
between 0 and 1, the Ford circles that are tangent to C[p/q] are precisely those
associated with the fractions that are the neighbours of p/q in some Farey sequence.  

I hope to see you there! Talk: Farey Fractions Speaker: Ivan Guo Date/Time: Wednesday
March 11, 1-2pm Location: Carslaw 452 

Before I finish typing this message, I’d like to mention a few final things.  - We have
a facebook group:  Feel free to join
it.  We also have a website, but I won’t give you the link yet because it hasn’t been
updated in a while, oh the shame.  (Actually, the link is on the facebook group,
bugger.  I’ll update it this week).  We are also planning on expanding the website quite
a bit over the year.  - If you have any questions or suggestions for SUMS, feel free to
send us an email! - Future SUMS messages will be shorter than this one.  

SUMS President 

"Now what is the message there? The message is that there are known "knowns." There are
things we know that we know.  There are known unknowns.  That is to say there are things
that we now know we don’t know.  But there are also unknown unknowns.  There are things
we do not know we don’t know.  So when we do the best we can and we pull all this
information together, and we then say well that’s basically what we see as the
situation, that is really only the known knowns and the known unknowns.  And each year,
we discover a few more of those unknown unknowns." - Donald Rumsfeld

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