Interference of Dark Matter Solitons and Galactic Offsets

By performing numerical simulations, we discuss the collisional dynamics of stable solitary waves in the Schrodinger-Poisson equation. In the framework of a model in which part or all of dark matter is a Bose-Einstein condensate of ultralight axions, we show that these dynamics can naturally account for the relative displacement between dark and ordinary matter in the galactic cluster Abell 3827, whose recent observation is the first empirical evidence of dark matter interactions beyond gravity. The essential assumption is the existence of solitonic galactic cores in the kiloparsec scale. For this reason, we present simulations with a benchmark value of the axion mass $m_a = 2 \times 10^{-24}$ eV, which is somewhat lower than the one preferred for cosmological structure formation if the field is all of dark matter ($m_a \approx 10^{-22}$eV). We argue that future observations might bear out or falsify this coherent wave interpretation of dark matter offsets.Comment: 16 pages, 8 figures. In version 2, discussions and abstract improved, references adde

Light by light diffraction in vacuum

We show that a laser beam can be diffracted by a more concentrated light pulse due to quantum vacuum effects. We compute analytically the intensity pattern in a realistic experimental configuration, and discuss how it can be used to measure for the first time the parameters describing photon-photon scattering in vacuum. In particular, we show that the Quantum Electrodynamics prediction can be detected in a single-shot experiment at future 100 petawatt lasers such as ELI or HIPER. On the other hand, if carried out at one of the present high power facilities, such as OMEGA EP, this proposal can lead either to the discovery of non-standard physics, or to substantially improve the current PVLAS limits on the photon-photon cross section at optical wavelengths. This new example of manipulation of light by light is simpler to realize and more sensitive than existing, alternative proposals, and can also be used to test Born-Infeld theory or to search for axion-like or minicharged particles.Comment: 4 pages, 1 figur

Dynamics of vortex-antivortex pairs and rarefaction pulses in liquid light

We present a numerical study of the cubic-quintic nonlinear Schr\"odinger equation in two transverse dimensions, relevant for the propagation of light in certain exotic media. A well known feature of the model is the existence of flat-top bright solitons of fixed intensity, whose dynamics resembles the physics of a liquid. They support traveling wave solutions, consisting of rarefaction pulses and vortex-antivortex pairs. In this work, we demonstrate how the vortex-antivortex pairs can be generated in bright soliton collisions displaying destructive interference followed by a snake instability. We then discuss the collisional dynamics of the dark excitations for different initial conditions. We describe a number of distinct phenomena including vortex exchange modes, quasielastic flyby scattering, soliton-like crossing, fully inelastic collisions and rarefaction pulse merging

Coherent Cavitation in the Liquid of Light

We study the cubic- (focusing-)quintic (defocusing) nonlinear Schr\"odinger equation in two transverse dimensions. We discuss a family of stationary traveling waves, including rarefaction pulses and vortexantivortex pairs, in a background of critical amplitude. We show that these rarefaction pulses can be generated inside a flattop soliton when a smaller bright soliton collides with it. The fate of the evolution strongly depends on the relative phase of the solitons. Among several possibilities, we find that the dark pulse can reemerge as a bright soliton

Fermionic light in common optical media

Recent experiments have proved that the response to short laser pulses of common optical media, such as air or Oxygen, can be described by focusing Kerr and higher order nonlinearities of alternating signs. Such media support the propagation of steady solitary waves. We argue by both numerical and analytical computations that the low power fundamental bright solitons satisfy an equation of state which is similar to that of a degenerate gas of fermions at zero temperature. Considering in particular the propagation in both $O_2$ and air, we also find that the high power solutions behave like droplets of ordinary liquids. We then show how a grid of the fermionic light bubbles can be generated and forced to merge in a liquid droplet. This leads us to propose a set of experiments aimed at the production of both the fermionic and liquid phases of light, and at the demonstration of the transition from the former to the latter.Comment: 4 pages, 4 figure

Dripping, pressure and surface tension of self-trapped laser beams

We show that a laser beam which propagates through an optical medium with Kerr (focusing) and higher order (defocusing) nonlinearities displays pressure and surface-tension properties yielding capillarity and dripping effects totally analogous to usual liquid droplets. The system is reinterpreted in terms of a thermodynamic grand potential, allowing for the computation of the pressure and surface tension beyond the usual hydrodynamical approach based on Madelung transformation and the analogy with the Euler equation. We then show both analytically and numerically that the stationary soliton states of such a light system satisfy the Young-Laplace equation, and that the dynamical evolution through a capillary is described by the same law that governs the growth of droplets in an ordinary liquid system.Comment: 4 pages, 3 figure

Outcoupling vector solitons from a Bose-Einstein condensate with time-dependent interatomic forces

We discuss the possibility of emitting vector solitons from a two-component elongated BEC by manipulating in time the inter- or intra-species scattering lengths with Feshbach resonance tuning. We present different situations which do not have an analogue in the single species case. In particular, we show vector soliton out-coupling by tuning the interspecies forces, how the evolution in one species is controlled by tuning the dynamics of the other, and how one can implement the so-called supersolitons. The analysis is performed by numerical simulations of the one-dimensional Gross-Pitaevskii equation. Simple analytic arguments are also presented in order to give a qualitative insight

Drag force in bimodal cubic-quintic nonlinear Schr\"odinger equation

We consider a system of two cubic-quintic non-linear Schr\"odinger equations in two dimensions, coupled by repulsive cubic terms. We analyse situations in which a probe lump of one of the modes is surrounded by a fluid of the other one and analyse their interaction. We find a realization of D'Alembert's paradox for small velocities and non-trivial drag forces for larger ones. We present numerical analysis including the search of static and traveling form-preserving solutions along with simulations of the dynamical evolution in some representative examples

Coherent emission of atomic soliton pairs by Feshbach-resonance tuning

We present two simple designs of matter-wave beam splitters in a trapped Bose-Einstein Condensate (BEC). In our scheme, identical pairs of atomic solitons are produced by an adequate control --- in time and/or space --- of the scattering length. Our analysis is performed by numerical integration of the Gross-Pitaevskii equation and supported by several analytic estimates. Our results show that these devices can be implemented in the frame of current BEC experiments. The system has potential applications for the construction of a soliton interferometer

Lattice hyper-solitons in photorrefractive materials

We show a novel kind of nonlinear waves in two-dimensional photonic lattices. This waves take the form of light clusters that may fill an arbitrary number of lattice sites. We have demonstrated by numerical simulations that stable propagation can be achieved under adequate conditions and we have described the unstable patterns developed otherwise. Our results show that these new kind of nonlinear waves can be easily found in current experiments.Comment: 3 pages, 4 figures. Submitted to Optics Letter