Toroidal Vortices in Resistive Magnetohydrodynamic Equilibria

Resistive steady states in toroidal magnetohydrodynamics (MHD), where Ohm's law must be taken into account, differ considerably from ideal ones. Only for special (and probably unphysical) resistivity profiles can the Lorentz force, in the static force-balance equation, be expressed as the gradient of a scalar and thus cancel the gradient of a scalar pressure. In general, the Lorentz force has a curl directed so as to generate toroidal vorticity. Here, we calculate, for a collisional, highly viscous magnetofluid, the flows that are required for an axisymmetric toroidal steady state, assuming uniform scalar resistivity and viscosity. The flows originate from paired toroidal vortices (in what might be called a ``double smoke ring'' configuration), and are thought likely to be ubiquitous in the interior of toroidally driven magnetofluids of this type. The existence of such vortices is conjectured to characterize magnetofluids beyond the high-viscosity limit in which they are readily calculable.Comment: 17 pages, 4 figure

Online Public Denunciation: A Preliminary Inquiry on the Experience of those who Call-Out on Social Media

Online public denunciations, colloquially referred to as call-outs, have become a prevalent way to expose perceived moral and social wrongdoing in our society. Posting a denunciation online welcomes debate on the in situ incident, the participants, preferred outcomes, and the morality of exposure - creating additional issues and embroiling the poster. Research on this phenomenon has focused on public figures, celebrities, or otherwise viral incidents, and despite the prevalence of social media call-outs, little is known about the experiences of those who initiate them. This preliminary study uses a phenomenological lens to understand the desires, experience, and outcomes for those who post initial denunciations of community members online. Believing that call-outs happen because of some kind of in situ conflict, where disparate values, norms, ideas, experiences or perceptions about a situation shape the trajectory of the outcome, a conflict theory lens is used to examine this phenomenon. The experience of eight Minneapolis and St. Paul residents who posted initial denunciations that called-out community members is explored. Findings indicate the proximity to the in situ incident impacts the experience of the person who posted the call-out. Other salient findings include the participants’ needs not being met, surprise with the way the call-out played out, and that social media was not a platform that supported reconciliation or healing. The implication of this study is greater depth of understanding of online public denunciation as a tool for conflict intervention from the perspective of those who initiate call-outs

Small scale structures in three-dimensional magnetohydrodynamic turbulence

We investigate using direct numerical simulations with grids up to 1536^3 points, the rate at which small scales develop in a decaying three-dimensional MHD flow both for deterministic and random initial conditions. Parallel current and vorticity sheets form at the same spatial locations, and further destabilize and fold or roll-up after an initial exponential phase. At high Reynolds numbers, a self-similar evolution of the current and vorticity maxima is found, in which they grow as a cubic power of time; the flow then reaches a finite dissipation rate independent of Reynolds number.Comment: 4 pages, 3 figure

Spontaneous creation of non-zero angular momentum modes in tunnel-coupled two-dimensional degenerate Bose gases

We investigate the dynamics of two tunnel-coupled two-dimensional degenerate Bose gases. The reduced dimensionality of the clouds enables us to excite specific angular momentum modes by tuning the coupling strength, thereby creating striking patterns in the atom density profile. The extreme sensitivity of the system to the coupling and initial phase difference results in a rich variety of subsequent dynamics, including vortex production, complex oscillations in relative atom number and chiral symmetry breaking due to counter-rotation of the two clouds.Comment: 7 pages, 5 figure

Generalized XY Model

The methods of Lie algebras are used to construct and solve a generalization of the XY model

Navifacial temperature and salinity along the track from Samoa to Hawaii, 1957–1965

The nine years of data used in the present study are the result of collaboration between the U.S. Bureau of Commercial Fisheries, Honolulu, and officers of MARIPOSA and MONTEREY of Matson Navigation Company…

Global periodicity conditions for maps and recurrences via Normal Forms

We face the problem of characterizing the periodic cases in parametric families of (real or complex) rational diffeomorphisms having a fixed point. Our approach relies on the Normal Form Theory, to obtain necessary conditions for the existence of a formal linearization of the map, and on the introduction of a suitable rational parametrization of the parameters of the family. Using these tools we can find a finite set of values p for which the map can be p-periodic, reducing the problem of finding the parameters for which the periodic cases appear to simple computations. We apply our results to several two and three dimensional classes of polynomial or rational maps. In particular we find the global periodic cases for several Lyness type recurrences.Comment: 25 page

Multiple noncommutative tori and Hopf algebras

We derive the Kac-Paljutkin finite-dimensional Hopf algebras as finite fibrations of the quantum double torus and generalize the construction for quantum multiple tori.Comment: 18 pages; AMSLaTeX (major revision, the construction of dual rewritten using approach of multiplier Hopf algebras, references added

Receipt from Geo. I. Roberts & Bros.

https://digitalcommons.salve.edu/goelet-new-york/1219/thumbnail.jp