Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Near Field Speckles The Optical Theorem Revisited   The zero angle scattered wave plays an essential role in the celebrated
Optical Theorem that relates the total extinction cross section (including both
scattering and absorption) to the complex amplitude of the scattered wave. In
an authoritative paper where the possibilities of an experimental verification
of Optical Theorem were discussed, it was pointed out that a proof could hardly
come from an optics experiment. One must agree to this statement if one
receives the scattering intensity from an assembly of particles as a Bragg
reflection from a three dimensional random grating. Accordingly, scattered
waves at any angle then behave as a circular Gaussian process, and phases are
equally distributed in the interval (-{\pi}, +{\pi}), therefore giving no cue
on the behaviour of the wave scattered at exactly zero angle. So a proof of the
Optical Theorem would require of telling apart an incoming wave from its weak
replica, and gauge the phase in between. In my PhD thesis, near field
scattering method is exploited for the determination of this elusive phase of
the scattered wave. Having determined the phase of the scattered wave, the
experimental verification of Optical Theorem can also be attempted. In
addition, the method can generate dynamic scattering data as well; it provides
an elegant and efficient way to filter out stray multiple scattering artefacts
and thus the method can be used even when multiple scattering is rampant.

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The categories of this paper are: cmp-lg
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-th
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The categories of this paper are: math-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: eess
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: nlin
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The categories of this paper are: adap-org
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The categories of this paper are: econ
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The categories of this paper are: quant-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin