Search results for "Vortex"
showing 10 items of 244 documents
Intensity spiral patterns in a semiconductor microresonator
2005
Spiral waves appear frequently in nature. They have been studied, e.g., in hydrodynamic systems, chemical reactions, and in a large variety of biological and physical systems [Grill et al., Phys. Rev. Lett. 75, 3368 (1995); Goryachev and Kapral, Phys. Rev. Lett. 76, 1619 (1996)]. In contrast to chemical and hydrodynamic processes where the field amplitude exhibits the spiral patterns (intensity spirals), in optics the spiral structures relate generally to the phase structure of the optical field (so-called 'optical vortices' [Lugiato et al., Adv. At., Mol., Opt. Phys. 40, 229 (1999); Arecchi et al., Phys. Rep. 318, 1 (1999); Weiss et al., Appl. Phys. B:Lasers Opt. B68, 151 (1999)]). Thus th…
Zero‐Energy Rotating Accretion Flows near a Black Hole
1996
We characterize the nature of thin, axisymmetric, inviscid, accretion flows of cold adiabatic gas with zero specific energy in the vicinity of a black hole by the specific angular momentum. Using two-dimensional hydrodynamic simulations in cylindrical geometry, we present various regimes in which the accretion flows behave distinctly differently. When the flow has a small angular momentum $(\lambda\lsim\lambda_b)$, most of the material is accreted into the black hole forming a quasi-spherical flow or a simple disk-like structure around it. When the flow has a large angular momentum (typically, larger than the marginally bound value, $\lambda\gsim\lambda_{mb}$), almost no accretion into the …
Stadnik and Flambaum Reply:
2016
In the comment of Avelino, Sousa and Lobo [arXiv:1506.06028], it is argued, by comparing the kinetic energy of a topological defect with the overall energy of a pulsar, that the origin of the pulsar glitch phenomenon due to the passage of networks of topological defects through pulsars is faced with serious difficulties. Here, we point out that topological defects may trigger pulsar glitches within traditional scenarios, such as vortex unpinning. If the energy transfer from a topological defect exceeds the activation energy for a single pinned vortex, this may lead to an avalanche of unpinning of vortices and consequently a pulsar glitch, and therefore the source of angular momentum and ene…
Excitation of E1-forbidden Atomic Transitions with Electric, Magnetic or Mixed Multipolarity in Light Fields Carrying Orbital and Spin Angular Moment…
2019
Photons carrying a well-defined orbital angular momentum have been proven to modify spectroscopic selection rules in atomic matter. Excitation profiles of electric quadrupole transitions have been measured with single trapped $^{40}$Ca$^+$ ions for varying polarizations. We further develop the photo-absorption formalism to study the case of arbitrary alignment of the beam's optical axis with respect to the ion's quantization axis and mixed multipolarity. Thus, predictions for M1-dominated $^{40}Ar^{13+}$, E3-driven $^{171}Yb^+$ and $^{172}Yb^+$, and B-like $^{20}Ne^{5+}$ are presented. The latter case displays novel effects, coming from the presence of a strong photon -- magnetic dipole cou…
The Dynamics of Eye Formation and Maintenance in Axisymmetric Diabatic Vortices
2009
Abstract This paper investigates the occurrence, formation, and maintenance of eyes in idealized axisymmetric balanced vortices with diabatic forcing. Two key elements of the model setup are temperature relaxation toward a specified equilibrium temperature Te and Ekman pumping from a turbulent boundary layer. Furthermore, the flow is assumed to be almost inviscid in the interior. The model does not attempt any closure for moist convection. Previous work by the authors has shown that there is a continuous transition from monsoonlike vortices to hurricane-like vortices. This transition is governed by the ratio ℱ = αT /cD, where αT is the thermal relaxation rate and cD the surface drag coeffic…
Bistable phase locking of a nonlinear optical cavity via rocking: Transmuting vortices into phase patterns.
2006
We report experimental observation of the conversion of a phase-invariant nonlinear system into a phase-locked one via the mechanism of rocking [G. J. de Valcarcel and K. Staliunas, Phys. Rev. E 67, 026604 (2003)]. This conversion results in that vortices of the phase-invariant system are being replaced by phase patterns such as domain walls. The experiment is carried out on a photorefractive oscillator in two-wave mixing configuration.A model for the experimental device is given that reproduces the observed behavior.
Bistable phase locking in a low fresnel number nondegenerate optical oscillator with injected signal
2011
Degenerate four-wave mixing oscillators are phase-bistable cavities. In such systems, above the oscillation threshold, two equivalent states, of equal intensities but opposite phases are generated. This phase bistability extends over the whole range of stable emission, unlike the intensity bistability (in, e.g. a saturable absorber cavity) that exits in a limited range of injection. When the cavity Fresnel number is large different patches of the beam transverse section can have different phases and a pattern forms. Basic patterns here are phase fronts (or domain walls), which are 1D structures separating regions with opposite phase that manifest as dark lines (as the phase jumps by p acros…
All-optical discrete vortex switch
2011
We introduce discrete vortex solitons and vortex breathers in circular arrays of nonlinear waveguides. The simplest vortex breather in a four-waveguide coupler is a nonlinear dynamic state changing its topological charge between $+1$ and $\ensuremath{-}1$ periodically during propagation. We find the stability domain for this solution and suggest an all-optical vortex switching scheme.
Switching the Magnetic Vortex Core in a Single Nanoparticle.
2016
Imaging and manipulating the spin structure of nano- and mesoscale magnetic systems is a challenging topic in magnetism, yielding a wide range of spin phenomena such as skyrmions, hedgehog-like spin structures, or vortices. A key example has been provided by the vortex spin texture, which can be addressed in four independent states of magnetization, enabling the development of multibit magnetic storage media. Most of the works devoted to the study of the magnetization reversal mechanisms of the magnetic vortices have been focused on micrometer-size magnetic platelets. Here we report the experimental observation of the vortex state formation and annihilation in individual 25 nm molecular-bas…
Topological charge selection rule for phase singularities
2009
We present a study of the dynamics and decay pattern of phase singularities due to the action of a system with a discrete rotational symmetry of finite order. A topological charge conservation rule is identified. The role played by the underlying symmetry is emphasized. An effective model describing the short range dynamics of the vortex clusters has been designed. A method to engineer any desired configuration of clusters of phase singularities is proposed. Its flexibility to create and control clusters of vortices is discussed.