The phase transition in Achlioptas processes

46 mins 36 secs,  178.25 MB,  iPod Video  480x270,  29.97 fps,  44100 Hz,  522.25 kbits/sec
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Description: Riordan, O (University of Oxford)
Monday 11th July 2016 - 11:45 to 12:30
 
Created: 2016-07-19 10:28
Collection: Theoretical Foundations for Statistical Network Analysis
Publisher: Isaac Newton Institute
Copyright: Riordan, O
Language: eng (English)
Distribution: World     (downloadable)
Explicit content: No
Aspect Ratio: 16:9
Screencast: No
Bumper: UCS Default
Trailer: UCS Default
 
Abstract: The classical random graph process starts with a fixed set of n vertices and no edges. Edges are then added one-by-one, uniformly at random. One of the most interesting features of this process, established by ErdÅ‘s and Rényi more than 50 years ago, is the phase transition near n/2 edges, where a single `giant' component emerges from a sea of small components. This example serves as a starting point for understanding phase transitions in a wide variety of other contexts. Around 2000, Dimitris Achlioptas suggested an innocent-sounding variation of the model: at each stage two edges are selected at random, but only one is added, the choice depending on (typically) the sizes of the components it would connect. This may seem like a small change, but these processes do not have the key independence property that underlies our understanding of the classical process. One can ask many questions about Achlioptas processes; the most interesting concern the phase transition: does the critical value change from n/2? Is the nature of the transition the same or not? I will describe a number of results on these questions from joint work with Lutz Warnke.
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