Half-bare positron in the inner gap of a pulsar

The pulsed radiation from the Crab Pulsar consists of the main pulse (MP) and inter pulse (IP), as well as of the extra pulse components appearing at certain frequencies. One of the mysteries of these data, found by Moffett and Hankins twenty years ago, is the shift of the IP at high radio frequencies compared to lower ones and return to its previous position in the higher-frequency optical and X-ray range. In previous paper we proposed the explanation of these mysterious changes with the frequency, applying the idea of the reflection of curvature radiation by relativistic positrons from the stellar surface. Presently we focus on the additional contribution of transition radiation, emitted when positron hits the surface, to the total pulse produced by the particle. It is shown that due to the 'half-bare' state of positron in the polar gap the considered contribution is significantly suppressed comparing to the one of reflected curvature radiation.

Strong interaction between plants induces circular barren patches: fairy circles

Fairy circles consist of isolated or randomly distributed circular areas devoid of any vegetation. They are observed in vast territories in southern Angola, Namibia and South Africa. We report on the formation of fairy circles, and we interpret them as localized structures with a varying plateau size as a function of the aridity. Their stabilization mechanism is attributed to a combined influence of the bistability between the bare state and the uniformly vegetation state, and Lorentzian-like non-local coupling that models the competition between plants. We show how a circular shape is formed, and how the aridity level influences the size of fairy circles. Finally, we show that the proposed mechanism is model-independent.

Reflection and Diffraction of Atomic de Broglie Waves by Evanescent Laser Waves - Bare-state Method

We present two results in an investigation of reflection and diffraction of atoms by gratings formed either by standing or travelling evanescent laser waves. Both results use the bare-state rather than dressed-state picture. One is based on the Born series, whereas the other is based on the Laplace transformation of the coupled differential equations. The two solutions yield the same theoretical expressions for reflected and diffracted atomic waves in the whole space, including the interaction and the asymptotic regions.