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Plane wave density functional theory codes generally assume periodicity in all three dimensions. This causes difficulties when studying charged systems, for instance energies per unit cell become infinite, and, even after being renormalised…
Structured light, when strongly focused, generates highly confined vectorial electromagnetic field distributions which may feature a polarization component along the optical axis. Manipulating and detecting such 3D light fields is…
For photonic crystal slab (PCS) structures, bound states in the continuum (BICs) and circularly polarized states (dubbed C-points) are important topological polarization singularities in momentum-space and have attracted burgeoning…
We study the propagation and scattering of electromagnetic waves by random arrays of dipolar cylinders in a uniform medium. A set of self-consistent equations, incorporating all orders of multiple scattering of the electromagnetic waves, is…
We derive a simple expression for the photon helicity and polarisation-flip probabilities in arbitrary background fields, in the low energy regime. Taking the background to model a focused laser beam, we study the impact of pulse shape and…
Multiply connected space sections of the universe on a scale smaller than the horizon size can leave an imprint on cosmic microwave background polarization maps, in such a way that the so-called ``circles-in-the-sky'' method can be used to…
A beam of rotating dipolar particles (molecules or clusters) will broaden when passed through an electric or magnetic field gradient region. This broadening, which is a common experimental observable, can be expressed in terms of the…
Weyl points are the simplest topologically-protected degeneracy in a three-dimensional dispersion relation. The realization of Weyl semimetals in photonic crystals has allowed these singularities and their consequences to be explored with…
We have experimentally and theoretically shown that the circularly polarized beam bearing singly charged optical vortex propagating through a uniaxial crystal can be split after focusing into the radially and azimuthally polarized beams in…
Singular Mueller matrices play an important role in polarization algebra and have peculiar properties that stem from the fact that either the medium exhibits maximum diattenuation and/or polarizance, or because its associated canonical…
Topological structures reveal the hidden secrets and beauty in nature, such as the double helix in DNA, whilst, the manipula-tion of which in physical fields, especially in ultrafast struc-tured light, draw booming attention. Here we…
We study the possible singularities of isotropic cosmological models that have a varying speed of light as well as a varying gravitational constant. The field equations typically reduce to two dimensional systems which are then analyzed…
Some bright cD galaxies in cluster cooling flows have Thomson optical depths exceeding 0.01. A few percent of their luminosity is scattered and appears as diffuse polarized emission. We calculate the scattering process for different…
The two-fold singularity has played a significant role in our understanding of uniqueness and stability in piecewise smooth dynamical systems. When a vector field is discontinuous at some hypersurface, it can become tangent to that surface…
The symmetric peak observed in linear polarization in the core of the solar sodium D$_1$ line at 5896 \AA\ has remained enigmatic since its discovery nearly two decades ago. One reason is that the theory of polarized scattering has not been…
We consider scattering of elastic waves on parallel wedge dislocations in the geometric theory of defects or, equivalently, scattering of point particles and light rays on cosmic strings. Dislocations are described as torsion singularities…
The recent PVLAS experiment observed the rotation of polarization and the ellipticity when a linearly polarized laser beam passes through a transverse magnetic field. The phenomenon cannot be explained in the conventional QED. We attempt to…
We study four--dimensional simplicial gravity through numerical simulation with special attention to the existence of singular vertices, in the strong coupling phase, that are shared by abnormally large numbers of four--simplices. The…
Vortex, the winding of a vector field in two dimensions, has its core the field singularity and its topological charge defined by the quantized winding angle of the vector field. Vortices are one of the most fundamental topological…
We study linear polarization due to scattering of light on a cloudlet of particles, taking into account the radiation drag and the gravitational pull exerted on them by a central body. Effects of special and general relativity are included…