Fluctuating Forces Induced by Nonequilibrium and Coherent Light Flow.

We show that mesoscopic coherent fluctuations of light propagating in random media induce fluctuating radiation forces. A hydrodynamic Langevin approach is used to describe the coherent light fluctuations, whose noise term accounts for mesoscopic coherent effects. This description-generalizable to other quantum or classical wave problems-allows us to understand coherent fluctuations as a nonequilibrium light flow, characterized by the diffusion coefficient D and the mobility σ, otherwise related by a Einstein relation. The strength of these fluctuating forces is determined by a single dimensionless and tunable parameter, the conductance g_{L}. Orders of magnitude of these fluctuation forces are offered that show experimental feasibility.

Numerical study of continuous and discontinuous dynamical phase transitions for boundary-driven systems.

The existence and search for thermodynamic phase transitions is of unfading interest. In this paper, we present numerical evidence of dynamical phase transitions occurring in boundary-driven systems with a constrained integrated current. It is shown that certain models exhibit a discontinuous transition between two different density profiles and a continuous transition between a time-independent and a time-dependent profile. We also verified that the Kipnis-Marchioro-Presutti model exhibits no phase transitions in a range much larger than previously explored.

Ramsey fringes and time-domain multiple-slit interference from vacuum.

Sequences of alternating-sign time-dependent electric field pulses lead to coherent interference effects in Schwinger vacuum pair production, producing a Ramsey interferometer, an all-optical time-domain realization of the multiple-slit interference effect, directly from the quantum vacuum. The interference, obeying fermionic quantum statistics, is manifest in the momentum dependence of the number of produced electrons and positrons along the linearly polarized electric field. The central value grows like N(2) for N pulses [i.e., N "slits"], and the functional form is well described by a coherent multiple-slit expression. This behavior is generic for many driven quantum systems.

Spatial log-periodic oscillations of first-passage observables in fractals.

For transport processes in geometrically restricted domains, the mean first-passage time (MFPT) admits a general scaling dependence on space parameters for diffusion, anomalous diffusion, and diffusion in disordered or fractal media. For transport in self-similar fractal structures, we obtain an expression for the source-target distance dependence of the MFPT that exhibits both the leading power-law behavior, depending on the Hausdorff and spectral dimension of the fractal, as well as small log-periodic oscillations that are a clear and definitive signal of the underlying fractal structure. We also present refined numerical results for the Sierpinski gasket that confirm this oscillatory behavior.

Thermodynamics of photons on fractals.

A thermodynamical treatment of a massless scalar field (a photon) confined to a fractal spatial manifold leads to an equation of state relating pressure to internal energy, PV(s) = U/d(s), where d(s) is the spectral dimension and V(s) defines the "spectral volume." For regular manifolds, V(s) coincides with the usual geometric spatial volume, but on a fractal this is not necessarily the case. This is further evidence that on a fractal, momentum space can have a different dimension than position space. Our analysis also provides a natural definition of the vacuum (Casimir) energy of a fractal. We suggest ways that these unusual properties might be probed experimentally.