Lecture Series on Polarisation by Prof. Rajaram Nityananda
About the lecture series:
These lectures are about the polarisation of electromagnetic radiation, with special reference to radio astronomy. The topics reflect both the intended audience, and the experience of the speaker, who has looked into these over the years. Some have connections with areas outside radio astronomy, which however gives us its own perspective. Though many topics are those practically encountered, the talks will not hesitate to stray beyond the boundaries of immediate utility. The plan is that each lecture has a distinct theme without too much mutual dependence. So this is not a course in the usual sense. People may want to pick and choose, based on the content of a given lecture.
Rajaram Nityananda obtained his PhD in physics from Bangalore University in 1977, working in areas of optics and crystallography at the Materials division of the National Aerospace Laboratory. At the Raman Research Institute, Bengaluru, he worked mainly on theoretical problems in astronomy relating to optics and dynamics until 2000. Then, for a decade, he worked at the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research (TIFR), Pune. He then taught undergraduate physics at IISER-Pune and the Azim Premji University in Bengaluru. After moving to ICTS-TIFR in 2022, he continues to work on radio imaging and gravitational lensing. He has served as the editor of Pramana Journal of Physics, Journal of Astrophysics and Astronomy, and Resonance, and has published in all of them as well.
1. Polarisation at a single frequency
December 02, 2024 5:30 PM IST (12:00 UT)
The different kinds of polarisation at a single frequency (linear, elliptic, circular). Representation by two complex amplitudes. Operations on polarised radiation - superposition, analysis, transformation - represented as 2x2 (Jones) matrices. Poincare sphere as a natural representation for all states of polarisation.
1) Slides
2. Unpolarised and partially polarised radiation:
December 04, 2024 5:30 PM IST (12:00 UT)
The need for a statistical description. Quasimonochromatic signals. The Stokes parameters. Connection with the Poincare representation. Properties of the Stokes representation. Polarised interferometry. Principles underlying calibrating the polarisation response. Closure errors coming from imperfect calibration.
1) Some links
3. Phase conventions for polarisation
December 06, 2024 5:30 PM IST (12:00 UT)
The interference of differently polarised signals. Geometric phase on the Poincare sphere. Connection with quantum theory. Need for a co-ordinate system. Polarisation over a large field of view. Problems with linearly polarised bases and their resolution.
4. Review of closure phase and closure amplitudes in single polarisation interferometry
December 09, 2024 5:30 PM IST (12:00 UT)
Generalisation to “full Stokes” interferometry. The closure traces of Broderick and Pesce (2020). General theory of calibration independent quantities constructed from Stokes visibilities. Possible applications in EHT like situations, open problems.
5. TBD/ TBA
December 11, 2024 5:30 PM IST (12:00 UT)
One is being both pessimistic – the time taken to do justice the the planned topics could be more than estimated – and optimistic – enough interest and discussions could have been generated to define the material for this concluding session. Could be both.
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