BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Petrean Chemistry\, Euler\, and the Bridges of Koenigsberg - Dr. R
 oger Mallion\, University of Kent
DTSTART:20190212T203000Z
DTEND:20190212T213000Z
UID:TALK117301@talks.cam.ac.uk
CONTACT:Mr Simon Thomas
DESCRIPTION:The speaker describes how\, some years ago\, he investigated t
 he history of one of Euler’s most famous and most easily understood cont
 ributions to Mathematics — namely\, the problem concerning the Bridges o
 f Königsberg — by making a ‘pilgrimage’ to the presentday Russian e
 xclave/enclave of Kaliningrad\, in order to attempt to execute a latterday
  ‘Eulerian Walk’ over the extant bridges of the modern city.\nEuler’
 s published solution to this problem (of 1736) constituted the first paper
  on what was called Analysis Situs (Analysis of Position). Euler in fact u
 sed Leibniz’s term\, Geometria Situs (Geometry of Position)\, a discipli
 ne in which all that matters is how entities are connected — in contrast
  to the more usual geometry in which it is distances and angles that are o
 f importance. Later still\, the subject became known as Graph Theory. Eule
 r’s seminal paper is thus generally regarded as having founded the moder
 n subject of Graph Theory (as well as that of Topology).\nSome 200 years l
 ater\, this idea of connectivity was fundamental to one of the first quant
 um-mechanical molecular-orbital theories — due to Hückel in the 1930s 
 — which is applicable to “aromatic” hydrocarbons and other families 
 of conjugated systems. Even though sophisticated ab initio methods of calc
 ulation are these days routinely available — and can sometimes yield rem
 arkable accuracy — their frequently complex parametrisations and their d
 ependence on the wave function on which they are based often mask chemical
  intuition and physical insight\; the graph-theoretical (topological) appr
 oaches\, by contrast\, readily give rise to what Coulson once famously des
 cribed as ‘primitive patterns of understanding.’\nThe speaker will bri
 efly allude to some recent work carried out at Peterhouse in collaboration
  with Dr Timothy Dickens on the magnetic properties of some large conjugat
 ed systems that arise from so-called ‘topological ring-currents’. 
LOCATION:The Theatre\, Peterhouse
END:VEVENT
END:VCALENDAR