![]() (a–c) The background represents a speckle pattern generated by a circular aperture (λ = 1064 nm, speckle grain 490 nm) the white scale bar corresponds to 2 μm. Subdiffusion in a static speckle pattern. ![]() For example, in non-equilibrium statistical physics, the dynamics of a Brownian particle in a moving periodic potential can be described as a straightforward generalization of the dynamics of a Brownian particle in static not out-of-equilibrium potentials, while this is no longer the case for random potentials for which a full out-of-equilibrium description is still required 20. It is not a priori obvious that the same phenomena that have been observed with periodic potentials can also arise with random potentials, as the statistical properties of random potentials fundamentally differ from those of periodic potentials. In fact, similar and even more complex effects have been extensively studied using periodic potentials rather than random potentials: these studies include the observation of giant diffusion induced by an oscillating periodic potential 13 and the demonstration of guiding and sorting particles using either moving periodic potentials 14, 15, 16 or static periodic potentials in microfluidic flows 17, 18, 19. However, apart from these previous studies, there is little understanding of the interaction of Brownian motion with random light potentials and the intrinsic randomness of speckle patterns is largely considered a nuisance to be minimized for most purposes, e.g., in optical manipulation 11, 12. Earlier experimental works showed the possibility of trapping particles in high-intensity speckle light fields 6, 7, 8, 9, the simplest optical manipulation task and the emergence of superdiffusion in an active media constituted by a dense solution of microparticles that generates a time-varying speckle field 10. This latter example is particularly suited to work as a model system because its parameters (e.g., particle size and material, illumination light) are easily controllable and its dynamics are easily accessible by standard optical microscopy techniques 5. Another example of this kind of phenomena is given by the motion of a Brownian particle in a random optical potential generated by a speckle pattern, i.e., the random light field resulting from complex light scattering in optically complex media, such as biological tissues, turbid liquids and rough surfaces (see background in Figure 1a–c) 3, 4. Examples range from the nanoscopic world of molecules undergoing anomalous diffusion within the cytoplasm of a cell 1 to the Brownian motion of stars within galaxies 2. Reference: Oxford Press Dictonary of Economics, 5th edt.Various phenomena rely on particles performing stochastic motion in random potentials. The name is used both for this phenomenon and for the mathematical model that describes it the latter is also known as the Wiener process. ![]() It is named after Robert Brown (1773-1858), a botanist who in 1827 first observed under a microscope the random movement of pollen or dust particles floating in water. ![]() Read more about how we make money >Ī Gaussian process with independent non-overlapping increments. The order in which products and services appear on Invezz does not represent an endorsement from us, and please be aware that there may be other platforms available to you than the products and services that appear on our website. ![]() While our reviews and assessments of each product on the site are independent and unbiased, brands may pay to appear higher up our table rankings or place ads in specific areas of the site. In order to fund our work, we partner with advertisers who compensate us for users that Invezz refers to their services. Invezz is an independent platform with the goal of helping users achieve financial freedom. ![]()
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