Temporal recompression through a scattering medium via a broadband transmission matrix

The transmission matrix is a unique tool to control light through a scattering medium. A monochromatic transmission matrix does not allow temporal control of broadband light. Conversely, measuring multiple transmission matrices with spectral resolution allows fine temporal control when a pulse is temporally broadened upon multiple scattering, but requires very long measurement time. Here, we show that a single linear operator, measured for a broadband pulse with a co-propagating reference, naturally allows for spatial focusing, and interestingly generates a two-fold temporal recompression at the focus, compared with the natural temporal broadening. This is particularly relevant for non-linear imaging techniques in biological tissues.Comment: 4 pages, 3 figure

Enhanced nonlinear imaging through scattering media using transmission matrix based wavefront shaping

Despite the tremendous progresses in wavefront control through or inside complex scattering media, several limitations prevent reaching practical feasibility for nonlinear imaging in biological tissues. While the optimization of nonlinear signals might suffer from low signal to noise conditions and from possible artifacts at large penetration depths, it has nevertheless been largely used in the multiple scattering regime since it provides a guide star mechanism as well as an intrinsic compensation for spatiotemporal distortions. Here, we demonstrate the benefit of Transmission Matrix (TM) based approaches under broadband illumination conditions, to perform nonlinear imaging. Using ultrashort pulse illumination with spectral bandwidth comparable but still lower than the spectral width of the scattering medium, we show strong nonlinear enhancements of several orders of magnitude, through thicknesses of a few transport mean free paths, which corresponds to millimeters in biological tissues. Linear TM refocusing is moreover compatible with fast scanning nonlinear imaging and potentially with acoustic based methods, which paves the way for nonlinear microscopy deep inside scattering media

Revisiting Complex Moments For 2D Shape Representation and Image Normalization

When comparing 2D shapes, a key issue is their normalization. Translation and scale are easily taken care of by removing the mean and normalizing the energy. However, defining and computing the orientation of a 2D shape is not so simple. In fact, although for elongated shapes the principal axis can be used to define one of two possible orientations, there is no such tool for general shapes. As we show in the paper, previous approaches fail to compute the orientation of even noiseless observations of simple shapes. We address this problem. In the paper, we show how to uniquely define the orientation of an arbitrary 2D shape, in terms of what we call its Principal Moments. We show that a small subset of these moments suffice to represent the underlying 2D shape and propose a new method to efficiently compute the shape orientation: Principal Moment Analysis. Finally, we discuss how this method can further be applied to normalize grey-level images. Besides the theoretical proof of correctness, we describe experiments demonstrating robustness to noise and illustrating the method with real images.Comment: 69 pages, 20 figure

Universal quantum criticality at the Mott-Anderson transition

We present a large N solution of a microscopic model describing the Mott-Anderson transition on a finite-coordination Bethe lattice. Our results demonstrate that strong spatial fluctuations, due to Anderson localization effects, dramatically modify the quantum critical behavior near disordered Mott transitions. The leading critical behavior of quasiparticle wavefunctions is shown to assume a universal form in the full range from weak to strong disorder, in contrast to disorder-driven non-Fermi liquid ("electronic Griffiths phase") behavior, which is found only in the strongly correlated regime.Comment: 4 pages + references, 4 figures; v2: minor changes, accepted for publication in Phys. Rev. Let

NeXSPheRIO results on elliptic flow at RHIC and connection with thermalization

Elliptic flow at RHIC is computed event-by-event with NeXSPheRIO. Reasonable agreement with experimental results on $v_2(\eta)$ is obtained. Various effects are studied as well: reconstruction of impact parameter direction, freeze out temperature, equation of state (with or without crossover), emission mecanism.Comment: Contribution to the Proceedings of the Quark-Gluon Plasma Thermalization workshop. Content slightly increase

Chaotic and deterministic switching in a two-person game

We study robust long-term complex behaviour in the Rock-Scissors-Paper game with two players, played using reinforcement learning. The complex behaviour is connected to the existence of a heteroclinic network for the dynamics. This network is made of three heteroclinic cycles consisting of nine equilibria and the trajectories connecting them. We provide analytical proof both for the existence of chaotic switching near the heteroclinic network and for the relative asymptotic stability of at least one cycle in the network, leading to behaviour ranging from almost deterministic actions to chaotic-like dynamics. Our results are obtained by making use of the symmetry of the original problem, a new approach in the context of learning.learning process, dynamics, switching, chaos

A paisagem vegetal e o uso do território ao longo do tempo

A estabilidade macroclimática é uma ilusão transmitida pela nossa curta esperança de vida. À escala geológica, desde tempos geológicos muito remotos (cf. Briggs 1995), nos terrenos que hoje constituem o território português, o clima oscilou entre os frios glaciares e os calores tropicais, passando pelos macroclimas de tipo temperado e mediterrânico (Suc 1984). No início da época Miocénica (23,8-5,3 Ma BP*) grande parte da Península Ibérica estava submetida a um macrobioclima de tipo tropical, com chuvas bem distribuídas ao longo do ano e, à excepção das montanhas, com uma estação fria amena e sem geadas. Cobriam a Península Ibérica amplas florestas tropicais e subtropicais, entre as quais sobressaíam pela sua abundância as florestas laurifólias (laurissilva), i.e. florestas dominadas por espécies de folhas grandes, largas, por norma inteiras (não recortadas), persistentes, sem pêlos, rijas, lisas e brilhantes. A partir do Miocénico Médio a flora e a vegetação ibéricas foram profundamente marcadas por uma sucessão de convulsões geológicas e macroclimáticas, em particular pelas alterações climáticas que culminaram na transição do macrobioclima tropical para o mediterrânico no Pliocénico e pelos numerosos ciclos glaciar-interglaciar plistocénicos

A paisagem vegetal e o uso do território ao longo do tempo

A estabilidade macroclimática é uma ilusão transmitida pela nossa curta esperança de vida. À escala geológica, desde tempos geológicos muito remotos (cf. Briggs 1995), nos terrenos que hoje constituem o território português, o clima oscilou entre os frios glaciares e os calores tropicais, passando pelos macroclimas de tipo temperado e mediterrânico (Suc 1984). No início da época Miocénica (23,8-5,3 Ma BP*) grande parte da Península Ibérica estava submetida a um macrobioclima de tipo tropical, com chuvas bem distribuídas ao longo do ano e, à excepção das montanhas, com uma estação fria amena e sem geadas. Cobriam a Península Ibérica amplas florestas tropicais e subtropicais, entre as quais sobressaíam pela sua abundância as florestas laurifólias (laurissilva), i.e. florestas dominadas por espécies de folhas grandes, largas, por norma inteiras (não recortadas), persistentes, sem pêlos, rijas, lisas e brilhantes. A partir do Miocénico Médio a flora e a vegetação ibéricas foram profundamente marcadas por uma sucessão de convulsões geológicas e macroclimáticas, em particular pelas alterações climáticas que culminaram na transição do macrobioclima tropical para o mediterrânico no Pliocénico e pelos numerosos ciclos glaciar-interglaciar plistocénicos