Two forthcoming seminars

[CM ICTP - Trieste]

JOINT ICTP/SISSA STATISTICAL PHYSICS SEMINAR



Thursday, 22 May    -    2:30 p.m.



Lecture Room 'D' - SISSA Main Building


M. BERRY   ( Bristol University )



Series of lectures on: 'Singularities and asymptotics'


Second lecture

" Conical diffraction: Imaging Hamilton's diabolical point "



Abstract

The transformation of a narrow beam into a hollow cone when incident 
along the optic axis of a biaxial crystal, predicted by Hamilton in 
1832, created a sensation when observed by Lloyd soon afterwards. It 
was possibly the first prediction of a qualitatively new phenomenon 
using mathematics, the first application of the concept of phase space, 
and the prototype of the conical intersections now popular in quantum 
chemistry. But the fine structure of the light cone contains many 
subtle features, slowly revealed by experiment, whose definitive 
explanation, involving new mathematical asymptotics, has been achieved 
only recently, along with definitive experimental test of the theory. 
Radically different phenomena, being intensively studied now, arise 
when chirality and absorption are incorporated in addition to 
biaxiality.
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JOINT ICTP/SISSA STATISTICAL PHYSICS SEMINAR



Tuesday, 27 May    -    11:00 a.m.




Lecture Room 'B' - terrace level- ICTP Leonardo Building




M. BERRY  ( Bristol University )



Series of lectures on: 'Singularities and asymptotics'


Third lecture

" Polarization fingerprints in the clear blue sky "



Abstract

Daylight is polarized, the strength being greatest at points in the sky 
at right angles to the sun, and zero at four points: above and below 
the sun and anti-sun. The zero-polarization points are ‘fingerprint’ 
singularities, around which the polarization direction makes a 
half-turn. Using elementary singularity theory, the polarization 
pattern across the whole sky can be described in a way that fits recent 
observations with an accuracy comparable to that of conventional 
elaborate multiple-scattering calculations. This recent work is a 
contribution to a story that started in 1817 and has been central to 
our understanding of polarized light.