Hawking radiation and classical tunneling: A ray phase space approach

Acoustic waves in fluids undergoing the transition from sub-to supersonic flow satisfy governing equations similar to those for light waves in the immediate vicinity of a black hole event horizon. This acoustic analogy has been used by Unruh and others as a conceptual model for Hawking radiation. Here, we use variational methods, originally introduced by Brizard for the study of linearized MHD, and ray phase space methods, to analyze linearized acoustics in the presence of background flows. The variational formulation endows the evolution equations with natural Hermitian and symplectic structures that prove useful for later analysis. We derive a 2 x 2 normal form governing the wave evolution in the vicinity of the event horizon. This shows that the acoustic model can be reduced locally (in ray phase space) to a standard (scalar) tunneling process weakly coupled to a unidirectional non-dispersive wave (the incoming wave ). Given the normal form, the Hawking thermal spectrum can be derived by invoking standard tunneling theory, but only by ignoring the coupling to the incoming wave. Deriving the normal form requires a novel extension of the modular ray-based theory used previously to study tunneling and mode conversion in plasmas. We also discuss how ray phase space methods can be used to change representation, which brings the problem into a form where the wave functions are less singular than in the usual formulation, a fact that might prove useful in numerical studies. (C) 2016 AIP Publishing LLC

Unfolding of differential energy spectra in the MAGIC experiment

The paper describes the different methods, used in the MAGIC experiment, to unfold experimental energy distributions of cosmic ray particles (gamma-rays). Questions and problems related to the unfolding are discussed. Various procedures are proposed which can help to make the unfolding robust and reliable. The different methods and procedures are implemented in the MAGIC software and are used in most of the analyses.Comment: Submitted to NIM

Near-IR resonant response of Ge microparticles fabricated by femtosecond laser printing

Recently introduced femtosecond laser printing approach was applied for the controlled fabrication of single germanium microparticles (MPs). The characterization of MPs was performed by scanning electron microscopy and near-IR optical spectroscopy. The size of obtained MPs is about 1-1.5 μm while their shape is close to spherical. Theoretical calculations of MP scattering cross section were performed on the basis of Mie theory. It is shown that extinction spectra of Ge MPs possess sharp resonances in near IR spectral region, which are identified by means of multipole decomposition analysis.</p