Thu, 10 Jan 2008
10:30
L3

Profinite completion and MacNeille completion can coincide on modal algebras

Jacob Vosmaer
(Amsterdam)
Abstract

We show that the profinite completion (a universal algebraic

construction) and the MacNeille completion (an order-theoretic

construction) of a modal algebra $A$ coincide, precisely when the congruences of finite index of $A$ correspond to principal order filters. Examples of such modal algebras are the free K4-algebra and the free PDL-algebra on finitely many generators.

Wed, 06 Jun 2007
12:00
L3

Constructing Gauge Theory Amplitudes

Ruth Britto
(Amsterdam)
Abstract
 
Gauge theory amplitudes lie at the meeting ground of perturbative QCD and twistor string theory.  The past three years have seen dramatic developments in the analytic computation of amplitudes and their interpretation in twistor space geometry.  I will discuss applications to collider experiments and describe direct, systematic procedures for deriving one-loop amplitudes from tree amplitudes, using new insights regarding unitarity.

 
 
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