(NOTE:  Not the usual day)

			PHYSICAL MATHEMATICS SEMINAR

TOPIC:		LOCALIZED WAVES AND TUNEABLE FRONT INTERACTION BY 
		TEMPORAL MODULATION

SPEAKER:	HERMANN RIECKE
		Engineering Sciences and Applied Mathematics
		Northwestern University

ABSTRACT:

Quite a few physical systems that undergo transitions to spatially
periodic states also exhibit localized states, which are confined to a
small part of the spatially homogeneous system.  A well-known example are
the single-peak excitations ('oscillons'), which were observed on the
surface of vertically vibrated granular media.  Localized states often can
be understood as arising from the interaction of fronts that connect the
basic state with a coexisting nonlinear state.  In electroconvection of
nematic liquid crystals, however, localized waves ('worms') have been
observed in a regime that exhibits no such bistability.  I will discuss a
weakly nonlinear model that provides an understanding of the localization
mechanism of the worms.  To probe that mechanism further, we consider the
effect of a periodic forcing and find that it provides a tuneable
interaction between fronts and can by itself stabilize localized waves.

DATE:		WEDNESDAY, MARCH 8, 2000

TIME:		2:30 PM

LOCATION:	Building 2, Room 338

Refreshments will be served at 3:30 PM in Building 2, Room 349.

					Massachusetts Institute of Technology
					Department of Mathematics
					Cambridge, MA  02139