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M. V. Berry

Publications and source records attributed to M. V. Berry.

4 recordsLinked to original sources
arXiv2026

Wave chirality reversal without passing achirality

Chiral connectedness describes chiral structures that transform smoothly into their mirror images while never being achiral. The phenomenon is illustrated with a two-parameter family of complex vector fields E representing paraxial optical Gaussian beams. E is chiral everywhere in the parameter plane except the origin. During a circuit of the origin, E reverses chirality twice without being achiral. Different aspects of chirality are associated with the vector and scalar nature of E; natural measures of each, and their combinations, change sign at parameter values where E is chiral. The analysis is simpler for planar fields E, but their chiralities are essentially the same when the subtleties of three dimensions are included.

physics.optics↗
arXiv2015

Note on the helicity decomposition of spin and orbital optical currents

In the helicity representation, the Poynting vector (current) for a monochromatic optical field, when calculated using either the electric or the magnetic field, separates into right-handed and left-handed contributions, with no cross-helicity contributions. Cross-helicity terms do appear in the orbital and spin contributions to the current. But when the electric and magnetic formulas are averaged ('electric-magnetic democracy'), these terms cancel, restoring the separation into right-handed and left-handed currents for orbital and spin separately.

physics.optics↗
arXiv2005

Reflectionless Potentials and PT Symmetry

Large families of Hamiltonians that are non-Hermitian in the conventional sense have been found to have all eigenvalues real, a fact attributed to an unbroken PT symmetry. The corresponding quantum theories possess an unconventional scalar product. The eigenvalues are determined by differential equations with boundary conditions imposed in wedges in the complex plane. For a special class of such systems, it is possible to impose the PT-symmetric boundary conditions on the real axis, which lies on the edges of the wedges. The PT-symmetric spectrum can then be obtained by imposing the more transparent requirement that the potential be reflectionless.

quant-ph↗