The New Theory for Rogue Waves featured in SPIE Newsroom !


14 August 2015, SPIE Newsroom. DOI: 10.1117/2.1201507.006035


Last Updated (Wednesday, 19 August 2015 14:26)


Irreversibility of Shock Waves Explained by Nonlinear Gamow Vectors

Editors of Physical Review A have retained among their suggestions a paper published by Silvia Gentilini, Maria Chiara Braidotti, Giulia Marcucci, Eugenio Del Re and Claudio Conti about a novel theoretical approach for the description of shock waves in nonlinear nonlocal media.

The novel theory is based on ideas retained from Irreversible Quantum Mechanics, a novel formulation of quantum mechanics based on the so-called Rigged Hilbert Space that include explonential decaying wavefuctions.

The theory describes the shock and wave-breaking scenario beyond the limits of the usual hydrodynamic approach, and allows to derive closed forms for the degree of irreversibility. This approach also introduces the "nonlinear Gamow Vectors," a novel kind of nonlinear waves with many possible applications in nonlinear physics.


Last Updated (Wednesday, 05 August 2015 08:28)


Three-dimensional rogue waves by random media go through obstacles

Formerly considered a myth, the sudden formation of giant waves in a sea of low amplitude wavelets is nowadays an important subject of interdisciplinary research. These “rogue waves” (RW) are studied in different contexts, and their understanding is a challenge characterized by an intense discussion and a number of potential applications. 

It is commonly accepted that the physics underlying the generation of giant oceanic RW is different from that of usual waves and that the triggering mechanism of RWs is not unique: linear effects (such as the focusing of independent wave trains) as well as the nonlinear amplification of noise may produce RWs.

In a paper published in Applied Physics Letters, Marco Leonetti and Claudio Conti use a spatial light modulator (SLM) to explore the possible speckle configurations generated by a random medium  to generate and control a three-dimensional rogue wave.

They demonstrate that the SLM allows to select among all the possible realizations, the RW located at a user defined position in the shadow of the nearly totally reflecting obstacle. Moreover, by tuning the properties of the speckle pattern, the localization along the propagation axis can be controlled.

The picture below show the three-dimensional reconstruction of the observed rogue-wave.


Last Updated (Sunday, 19 July 2015 10:13)


Relativistic analogue in non-paraxial shock waves

Shock generation and wave-breaking are effects largely investigated in nonlinear optics. They are always occurring in extreme regimes with a variety of fundamental physical implications, and a number of applications, ranging from particle and material manipulation, to supercontinuum and X-ray generation.

In nonlinear optics, one studies shocks in space and time. Concerning the spatial case, shock waves are observed as highly irregular wave-fronts that originate upon the propagation of a smooth Gaussian beam in a strongly nonlinear medium like, for example, a thermal liquid.

So far, the analysis of spatial shock waves has been limited by the paraxial approximation. The validity of this approximation, however, is questioned by the large spatial bandwidth that is observed at the shock formation.

In a manuscript published in Optics Communications (arXiv:1412.8602) Silvia Gentilini, Eugenio Del Re and Claudio Conti study theoretically and computationally the effects of the non-paraxial regime on the shocks. The result is a predicted correction to the maximal spatial bandwidth after the shock generation, which is within experimentally measurable values, and which is also relevant for temporal shock waves.

The analysis is fascinating, as it shows that non-paraxial terms can be mapped to the relativistic corrections that occur when one considers the propagation of particles with velocity comparable with the speed of light. In other words, the mathematical treatment of the non-paraxial shock is analogue to the treatment of the relativistic particle motion. The trajectories of the particles corresponds to the so-called characteristic lines.

This problem is also relevant for mathematical investigations concerning wave-breaking in high-order nonlinear partial differential equations.

The picture below shows an example of  the calculation of the relativistic shock wave front.


Last Updated (Sunday, 19 July 2015 09:45)


Geometric explanation of Rogue Solitons featured in the Cover of Optica

The geometrical approach for explaining the origin of Rogue Solitons has been featured in the Cover of OPTICA!