Journal articles: 'Singular jets'

1

Brenner, Michael P. "Jets from a singular surface." Nature 403, no. 6768 (2000): 377–78. http://dx.doi.org/10.1038/35000330.

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Müller, Livia, and Hubert Chanson. "Singular air entrapment at vertical and horizontal supported jets: plunging jets versus hydraulic jumps." Environmental Fluid Mechanics 20, no. 4 (2020): 1075–100. http://dx.doi.org/10.1007/s10652-020-09742-w.

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HEINZ, SEBASTIAN. "CLUES FOR THE COMPOSITION OF RELATIVISTIC MICROQUASAR JETS." International Journal of Modern Physics D 17, no. 10 (2008): 1947–52. http://dx.doi.org/10.1142/s0218271808013613.

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We discuss the evidence for proton loading in relativistic jets from microquasars in light of recent constraints on the jet power. We argue that, both in the case of the Cygnus X-1 jet and the entire ensemble of Galactic microquasars, the evidence points towards a significant contribution to the total kinetic energy flux from cold protons. However, as with all other methods of constraining jet composition (except for the singular case of SS 433), a number of alternative, though maybe less plausible, explanations exist. In light of this continued elusiveness of a single slam-dunk argument for proton loading, the best we can hope for is a continuing accumulation of bits of evidence such as these which will, on the whole, form a preponderance of evidence against pure pair jets.

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Papageorgiou, Demetrios T. "Analytical description of the breakup of liquid jets." Journal of Fluid Mechanics 301 (October 25, 1995): 109–32. http://dx.doi.org/10.1017/s002211209500382x.

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A viscous or inviscid cylindrical jet with surface tension in a surrounding medium of negligible density tends to pinch owing to the mechanism of capillary instability. We construct similarity solutions which describe this phenomenon as a critical time is encountered, for three distinct cases: (i) inviscid jets governed by the Euler equations, (ii) highly viscous jets governed by the Stokes equations, and (iii) viscous jets governed by the Navier-Stokes equations. We look for singular solutions of the governing equations directly rather than by analysis of simplified models arising from slender-jet theories. For Stokes jets implicitly defined closed-form solutions are constructed which allow the scaling exponents to be fixed. Navier-Stokes pinching solutions follow rationally from the Stokes ones by bringing unsteady and nonlinear terms into the momentum equations to leading order. This balance fixes a set of universal scaling functions for the phenomenon. Finally we show how the pinching solutions can be used to provide an analytical description of the dynamics beyond breakup.

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Larchenkova, Tatiana, Alexander Lutovinov, and Natalya Lyskova. "The image jets modeling of gravitationally lensed sources." Proceedings of the International Astronomical Union 6, S275 (2010): 106–7. http://dx.doi.org/10.1017/s1743921310015760.

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AbstractThe jets image modelling of gravitationally lensed sources have been performed. Several basic models of the lens mass distribution were considered, in particular, a singular isothermal ellipsoid, an isothermal ellipsoid with the core, different multi-components models with the galactic disk, halo and bulge. The obtained jet images were compared as with each other as with results of observations. A significant dependence of the Hubble constant on the model parameters was revealed for B0218+357, when the circular structure was took into account.

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HEWITT, RICHARD E., and PETER W. DUCK. "Pulsatile jets." Journal of Fluid Mechanics 670 (January 12, 2011): 240–59. http://dx.doi.org/10.1017/s0022112010005227.

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We consider the evolution of high-Reynolds-number, planar, pulsatile jets in an incompressible viscous fluid. The source of the jet flow comprises a mean-flow component with a superposed temporally periodic pulsation, and we address the spatiotemporal evolution of the resulting system. The analysis is presented for both a free symmetric jet and a wall jet. In both cases, pulsation of the source flow leads to a downstream short-wave linear instability, which triggers a breakdown of the boundary-layer structure in the nonlinear regime. We extend the work of Riley, Sánchez-Sans & Watson (J. Fluid Mech., vol. 638, 2009, p. 161) to show that the linear instability takes the form of a wave that propagates with the underlying jet flow, and may be viewed as a (spatially growing) weakly non-parallel analogue of the (temporally growing) short-wave modes identified by Cowley, Hocking & Tutty (Phys. Fluids, vol. 28, 1985, p. 441). The nonlinear evolution of the instability leads to wave steepening, and ultimately a singular breakdown of the jet is obtained at a critical downstream position. We speculate that the form of the breakdown is associated with the formation of a ‘pseudo-shock’ in the jet, indicating a failure of the (long-length scale) boundary-layer scaling. The numerical results that we present disagree with the recent results of Riley et al. (2009) in the case of a free jet, together with other previously published works in this area.

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MALAZA, E. D. "ASYMPTOTIC SCALING IN QUARK AND GLUON JET MULTIPLICITY DISTRIBUTIONS IN NEXT-TO-LEADING ORDER QCD." International Journal of Modern Physics A 04, no. 18 (1989): 4909–18. http://dx.doi.org/10.1142/s0217751x89002077.

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GOLDSTEIN, M. E., and S. J. LEIB. "The aeroacoustics of slowly diverging supersonic jets." Journal of Fluid Mechanics 600 (March 26, 2008): 291–337. http://dx.doi.org/10.1017/s0022112008000311.

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This paper is concerned with utilizing the acoustic analogy approach to predict the sound from unheated supersonic jets. Previous attempts have been unsuccessful at making such predictions over the Mach number range of practical interest. The present paper, therefore, focuses on implementing the refinements needed to accomplish this objective. The important effects influencing peak supersonic noise are found to be source convection, mean flow refraction, mean flow amplification, and source non-compactness. It appears that the last two effects have not been adequately dealt with in the literature. For the first of these this is because the usual parallel flow models produce most of the amplification in the so-called critical layer where the solution becomes singular and, therefore, causes the predicted sound field to become infinite. We deal with this by introducing a new weakly non-parallel flow analysis that eliminates the critical layer singularity. This has a strong effect on the shape of the peak noise spectrum. The last effect places severe demands on the source models at the higher Mach numbers because the retarded-time variations significantly increase the sensitivity of the radiated sound to the source structure in this case. A highly refined (non-separable) source model is, therefore, introduced in this paper.

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Stevens, Martha R., and Gregory J. Hakim. "Perturbation Growth in Baroclinic Waves." Journal of the Atmospheric Sciences 62, no. 8 (2005): 2847–63. http://dx.doi.org/10.1175/jas3502.1.

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Abstract Floquet theory is applied to the stability of time-periodic, nonparallel shear flows consisting of a baroclinic jet plus a neutral wave. This configuration is chosen as an idealized representation of baroclinic waves in a storm track, and the stability analysis may be helpful for understanding generic properties of the growth of forecast errors in such regions. Two useful attributes of Floquet theory relevant to this problem are that the period-average mode growth rate is norm independent, and the t→ ∞ stability limit is determined by the stability over one period. Exponentially growing Floquet modes are found for arbitrarily small departures from parallel flows. Approximately 70% of Floquet-mode growth in energy is due to barotropic conversion, with the remainder due to zonal heat flux. Floquet-mode growth rates increase linearly with neutral wave amplitude (i.e., the “waviness” of the jet) and also increase with neutral wave wavelength. Growth rates for meridionally localized jets are approximately 40% smaller than for comparable cases with linear vertical shear (the Eady jet). Singular vectors for these flows converge to the leading Floquet mode over one basic-state period, and the leading instantaneous optimal mode closely resembles the leading Floquet mode. Initial-value problems demonstrate that the periodic basic states are absolutely unstable, with Floquet modes spreading faster than the basic-state flow both upstream and downstream of an initially localized disturbance. This behavior dominates the convective instability of parallel-flow jets when the neutral baroclinic wave amplitude exceeds a threshold value of about 8–10 K. This result suggests that forecast errors in a storm track may spread faster, and affect upstream locations, for sufficiently wavy jets.

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Marheineke, Nicole, Björn Liljegren-Sailer, Maike Lorenz, and Raimund Wegener. "Asymptotics and numerics for the upper-convected Maxwell model describing transient curved viscoelastic jets." Mathematical Models and Methods in Applied Sciences 26, no. 03 (2016): 569–600. http://dx.doi.org/10.1142/s021820251650010x.

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This work deals with the modeling and simulation of non-Newtonian jet dynamics as it occurs in fiber spinning processes. Proceeding from a three-dimensional instationary boundary value problem of upper-convected Maxwell equations, we present a strict systematic derivation of a one-dimensional viscoelastic string model by using asymptotic analysis in the slenderness ratio of the jet. The model allows for the unrestricted motion and shape of the jet’s curve, and its deduction extends the hitherto existing uniaxial asymptotic approaches. However, the system of partial differential equations with algebraic constraint has a varying character (hyperbolic, hyperbolic–elliptic, parabolic deficiency). Its applicability range turns out to be limited depending on the physical parameters and the boundary conditions (i.e. singular perturbation). Numerical results are discussed for the hyperbolic regime of gravitational inflow–outflow set-ups which become relevant in drawing and extrusion processes. The simulations are performed with a normal form total upwind scheme in space and an implicit time-integration ensuring convergence of first order.

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Clainche, Soledad Le. "Prediction of the Optimal Vortex in Synthetic Jets." Energies 12, no. 9 (2019): 1635. http://dx.doi.org/10.3390/en12091635.

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This article presents three different low-order models to predict the main flow patterns in synthetic jets. The first model provides a simple theoretical approach based on experimental solutions explaining how to artificially generate the optimal vortex, which maximizes the production of thrust and system efficiency. The second model is a data-driven method that uses higher-order dynamic mode decomposition (HODMD). To construct this model, (i) Navier–Stokes equations are solved for a very short period of time providing a transient solution, (ii) a group of spatio-temporal data are collected containing the information of the transitory of the numerical simulations, and finally (iii) HODMD decomposes the solution as a Fourier-like expansion of modes that are extrapolated in time, providing accurate predictions of the large size structures describing the general flow dynamics, with a speed-up factor of 8 . 3 in the numerical solver. The third model is an extension of the second model, which combines HODMD with a low-rank approximation of the spatial domain, which is based on singular value decomposition (SVD). This novel approach reduces the memory requirements by 70% and reduces the computational time to generate the low-order model by 3, maintaining the speed-up factor to 8 . 3 . This technique is suitable to predict the temporal flow patterns in a synthetic jet, showing that the general dynamics is driven by small amplitude variations along the streamwise direction. This new and efficient tool could also be potentially used for data forecasting or flow pattern identification in any type of big database.

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Krishna Raja, D., S. P. Das, and E. J. Hopfinger. "On standing gravity wave-depression cavity collapse and jetting." Journal of Fluid Mechanics 866 (March 5, 2019): 112–31. http://dx.doi.org/10.1017/jfm.2019.86.

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Parametrically forced gravity waves can give rise to high-velocity surface jets via the wave-depression cavity implosion. The present results have been obtained in circular cylindrical containers of 10 and 15 cm in diameter (Bond number of order $10^{3}$) in the large fluid depth limit. First, the phase diagrams of instability threshold and wave breaking conditions are determined for the working fluid used, here water with 1 % detergent added. The collapse of the wave-depression cavity is found to be self-similar. The exponent $\unicode[STIX]{x1D6FC}$ of the variation of the cavity radius $r_{m}$ with time $\unicode[STIX]{x1D70F}$, in the form $r_{m}/R\propto \unicode[STIX]{x1D70F}^{\unicode[STIX]{x1D6FC}}$, is close to 0.5, indicative of inertial collapse, followed by a viscous cut-off of $\unicode[STIX]{x1D6FC}\approx 1$. This supports a Froude number scaling of the surface jet velocity caused by cavity collapse. The dimensionless jet velocity scales with the cavity depth that is shown to be proportional to the last stable wave amplitude. It can be expressed by a power law or in terms of finite time singularity related to a singular wave amplitude that sets the transition from a non-pinching to pinch-off cavity collapse scenario. In terms of forcing amplitude, cavity collapse and jetting are found to occur in bands of events of non-pinching and pinching of a bubble at the cavity base. At large forcing amplitudes, incomplete cavity collapse and splashing can occur and, at even larger forcing amplitudes, wave growth is again stable up to the singular wave amplitude. When the cavity is formed, an impulse model shows the importance of the singular cavity diameter that determines the strength of the impulse.

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BALMFORTH, N. J., and C. PICCOLO. "The onset of meandering in a barotropic jet." Journal of Fluid Mechanics 449 (December 10, 2001): 85–114. http://dx.doi.org/10.1017/s0022112001006127.

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This study explores the dynamics of an unstable jet of two-dimensional, incompressible fluid on the beta-plane. In the inviscid limit, standard weakly nonlinear theory fails to give a low-order description of this problem, partly because the simple shape of the unstable normal mode is insufficient to capture the structure of the forming pattern. That pattern takes the form of ‘cat's eyes’ in the vorticity distribution which develop inside the modal critical layers (slender regions to either side of the jet's axis surrounding the levels where the modal wave speed matches the mean flow). Asymptotic expansions furnish a reduced model which is a version of what is known as the single-wave model in plasma physics. The reduced model predicts that the amplitude of the unstable mode saturates at a relatively low level and is not steady. Rather, the amplitude evolves aperiodically about the saturation level, a result with implications for Lagrangian transport theories. The aperiodic amplitude ‘bounces’ are intimately connected with sporadic deformations of the vortices within the cat's eyes. The theory is compared with numerical simulations of the original governing equations. Slightly asymmetrical jets are also studied. In this case the neutral modes along the stability boundary become singular; an extension of the weakly nonlinear theory is presented for these modes.

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Gersten, Klaus. "The asymptotic downstream flow of plane turbulent wall jets without external stream." Journal of Fluid Mechanics 779 (August 17, 2015): 351–70. http://dx.doi.org/10.1017/jfm.2015.409.

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The plane turbulent wall-jet flow without externally imposed stream is considered. It is assumed that the wall jet does not emerge from a second wall perpendicular to the velocity vector of the initial wall jet. The (kinematic) momentum flux $K(x)$ of the wall jet decreases downstream owing to the shear stress at the wall. This investigation is based on the hypothesis that the total friction force on the wall is smaller than the total inflow momentum flux. In other words, the turbulent wall jet tends to a turbulent ‘half-free jet’ with a non-zero momentum flux $K_{\infty }\;(\text{m}^{3}~\text{s}^{-2})$ far downstream. The fact that the turbulent half-free jet is the asymptotic form of a turbulent wall jet is the basis for a singular perturbation method by which the wall-jet flow is determined. It turns out that the ratio between the wall distance $y_{m}$ of the maximum velocity and the wall distance $y_{0.5}$ of half the maximum velocity decreases downstream to zero. Dimensional analysis leads immediately to a universal function of the dimensionless momentum flux $K(\mathit{Re}_{x})/K_{\infty }$ that depends asymptotically only on the local Reynolds number $\mathit{Re}_{x}=\sqrt{(x-x_{0})K_{\infty }}/{\it\nu}$, where $x_{0}$ denotes the coordinate of the virtual origin. When the values $K$ and ${\it\nu}$ at the position $x-x_{0}$ are known, the asymptotic momentum flux $K_{\infty }$ can be determined. Experimental data on all turbulent plane wall jets (except those emerging from a second plane wall) collapse to a single universal curve. Comparisons between available experimental data and the analysis make the hypothesis $K_{\infty }\neq 0$ plausible. A convincing verification, however, will be possible in the future, preferably by direct numerical simulations.

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Shaabani-Ardali, Léopold, Denis Sipp, and Lutz Lesshafft. "Vortex pairing in jets as a global Floquet instability: modal and transient dynamics." Journal of Fluid Mechanics 862 (January 16, 2019): 951–89. http://dx.doi.org/10.1017/jfm.2018.977.

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The spontaneous pairing of rolled-up vortices in a laminar jet is investigated as a global secondary instability of a time-periodic spatially developing vortex street. The growth of subharmonic perturbations, associated with vortex pairing, is analysed both in terms of modal Floquet instability and in terms of transient growth dynamics. The article has the double objective to outline a toolset for the global analysis of time-periodic flows, and to leverage such an analysis for a fresh view on the vortex pairing phenomenon. Axisymmetric direct numerical simulations (DNS) of jets with single-frequency inflow forcing are performed, in order to identify combinations of the Reynolds and Strouhal numbers for which vortex pairing is naturally observed. The same DNS calculations are then repeated with an added time-delay control term, which artificially suppresses pairing, so as to obtain time-periodic unpaired base flows for linear stability analysis. It is demonstrated that the natural occurrence of vortex pairing in nonlinear DNS coincides with a linear subharmonic Floquet instability of the underlying unpaired vortex street. However, DNS results suggest that the onset of pairing involves much stronger temporal growth of subharmonic perturbations than that predicted by modal Floquet analysis, as well as a spatial distribution of these fast-growing perturbation structures that is inconsistent with the unstable Floquet mode. Singular value decomposition of the phase-shift operator (the operator that maps a given perturbation field to its state one flow period later) is performed for an analysis of optimal transient growth in the vortex street. Non-modal mechanisms near the jet inlet are thus found to provide a fast route towards the limit-cycle regime of established vortex pairing, in good agreement with DNS observations. It is concluded that modal Floquet analysis accurately predicts the parameter regime where sustained vortex pairing occurs, but that the bifurcation scenario under typical conditions is dominated by transient growth phenomena.

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Dhang, Prasun, Abhijit Bendre, Prateek Sharma, and Kandaswamy Subramanian. "Characterizing the dynamo in a radiatively inefficient accretion flow." Monthly Notices of the Royal Astronomical Society 494, no. 4 (2020): 4854–66. http://dx.doi.org/10.1093/mnras/staa996.

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ABSTRACT We explore the magneto-rotational instability (MRI)-driven dynamo in a radiatively inefficient accretion flow (RIAF) using the mean field dynamo paradigm. Using singular value decomposition (SVD) we obtain the least-squares fitting dynamo coefficients α and γ by comparing the time series of the turbulent electromotive force and the mean magnetic field. Our study is the first one to show the poloidal distribution of these dynamo coefficients in global accretion flow simulations. Surprisingly, we obtain a high value of the turbulent pumping coefficient γ, which transports the mean magnetic flux radially outwards. This would have implications for the launching of magnetized jets that are produced efficiently in presence a large-scale poloidal magnetic field close to the compact object. We present a scenario of a truncated disc beyond the RIAF where a large-scale dynamo-generated poloidal magnetic field can aid jet launching close to the black hole. Magnitude of all the calculated coefficients decreases with radius. Meridional variations of αϕϕ, responsible for toroidal to poloidal field conversion, is very similar to that found in shearing box simulations using the ‘test field’ (TF) method. By estimating the relative importance of α-effect and shear, we conclude that the MRI-driven large-scale dynamo, which operates at high latitudes beyond a disc scale height, is essentially of the α − Ω type.

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Spalart, Philippe R. "On the flow field induced by a hovering rotor or a static jet." Journal of Fluid Mechanics 701 (May 10, 2012): 473–81. http://dx.doi.org/10.1017/jfm.2012.188.

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AbstractThe flow in the far field of an isolated static momentum source is considered, taking into account the entrainment of fluid by the turbulent jet which develops far downstream irrespective of the type of device. The result is a simple analytical model for the irrotational region, which depends only on the thrust applied. This equation is implied by Stewart (J. Fluid Mech., vol. 1, 1956, pp. 593–606) for a jet. For a rotor, the model is radically different from the classical one derived from an actuator disk without turbulence or mixing in the wake, which led to a sink flow in the far field. The velocities decay like $1/ r$ rather than $1/ {r}^{2} $, where $r$ is the radius, and are everywhere directed in the direction opposite to the thrust, rather than pointing towards the origin. The momentum source drives a co-flow which converges towards the turbulent region, thus supplying the entrained fluid. This flow pattern supports the assumption that the fluid surrounding the turbulent region is irrotational, better than the sink-flow model would. The model depends only on one empirical constant, a measure of the entrainment in a fully developed jet, for which a range of values is determined from the experimental literature. If the rotor is climbing, the sink flow is recovered; however, the limit of that equation as the climb velocity tends to zero, leading to hover, is singular. For both jets and rotors, this model used in a boundary condition should eliminate extraneous parameters and reduce the computational cost of numerical simulations, and may guide the design of chambers used for experiments, following Ricou & Spalding (J. Fluid Mech., vol. 11, 1960, pp. 21–32).

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Shu, Frank H., Susana Lizano, and Fred C. Adams. "Star Formation in Molecular Cloud Cores." Symposium - International Astronomical Union 115 (1987): 417–34. http://dx.doi.org/10.1017/s0074180900096121.

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The problem of gravitational collapse and star formation is entirely different when the ratio of the mass of a molecular cloud Mcl to its magnetic flux Φ is high than when it is low. Magnetically-diluted overall collapse of a large dense core and the formation of an OB association or a bound cluster are the likely outcomes in the former case; quasi-static contraction of many small cores and their ultimate collapse to form a T association, in the latter. In our picture, the birth of a T association in a dark cloud like Taurus proceeds by ambipolar diffusion on a time-scale of ∼ 107 years. As magnetic and turbulent support is gradually lost from a small condensing core, it approaches a state resembling a slowly rotating singular isothermal sphere which, when it passes the brink of instability, collapses from “inside-out,” building up a central protostar and nebular disk. The emergent spectral energy distributions of theoretical models in this stage of protostellar evolution resemble closely those of recently found sources with steep spectra in the infrared. The protostellar phase is ended by the reversal of the infall by an intense stellar wind, whose ultimate source of energy derived from the differential rotation of the star. We argue that the initial breakout is likely to occur along the rotational poles, leading to collimated jets and bipolar outflows. The stellar jet eventually widens to sweep out gas in nearly all 4π steradian, revealing at the center a T Tauri star and a remnant nebular disk. We give rough scaling relations which must apply if an analogous process is to succeed for producing high mass stars.

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Streltsova, Irina. "Classification of curves on de Sitter plane." Proceedings of the International Geometry Center 13, no. 1 (2020): 1–8. http://dx.doi.org/10.15673/tmgc.v13i1.1683.

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In 1917, de Sitter used the modified Einstein equation and proposed a model of the Universe without physical matter, but with a cosmological constant. De Sitter geometry, as well as Minkowski geometry, is maximally symmetrical. However, de Sitter geometry is better suited to describe gravitational fields. It is believed that the real Universe was described by the de Sitter model in the very early stages of expansion (inflationary model of the Universe). This article is devoted to the problem of classification of regular curves on the de Sitter space. As a model of the de Sitter plane, the upper half-plane on which the metric is given is chosen. For this purpose, an algebra of differential invariants of curves with respect to the motions of the de Sitter plane is constructed. As it turned out, this algebra is generated by one second-order differential invariant (we call it by de Sitter curvature) and two invariant differentiations. Thus, when passing to the next jets, the dimension of the algebra of differential invariants increases by one. The concept of regular curves is introduced. Namely, a curve is called regular if the restriction of de Sitter curvature to it can be considered as parameterization of the curve. A theorem on the equivalence of regular curves with respect to the motions of the de Sitter plane is proved. The singular orbits of the group of proper motions are described.

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Shu, Frank H., and Fred C. Adams. "Star formation and the circumstellar matter of young stellar objects." Symposium - International Astronomical Union 122 (1987): 7–22. http://dx.doi.org/10.1017/s0074180900155871.

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We propose that the formation of low mass stars in molecular clouds takes place in four stages. The first stage is the formation of slowly rotating cloud cores through the slow leakage of magnetic (and turbulent) support by ambipolar diffusion. These cores asymptotically approach quasistatic states resembling singular isothermal spheres, but such end states cannot actually be reached because they are unstable. The second phase begins when a condensing cloud core passes the brink of instability and collapses dynamically from “inside-out,” building up a central protostar and nebular disk. The emergent spectral energy distributions of theoretical models in the infall stage are in close agreement with those of recently found infrared sources with steep spectra. As the rotating protostar gains mass, deuterium will eventually ignite in the central regions and drive the star nearly completely convective if its mass is less than about 2 M⊙. This initiates the next step of evolution - the bipolar outflow phase - in which a stellar wind pushes outward and breaks through the infalling envelope. The initial breakout is likely to occur along the rotational poles, leading to collimated jets and bipolar outflows. The intense stellar wind eventually widens to sweep out gas in nearly all 4π steradian, revealing the fourth stage - a T Tauri star with a surrounding remnant nebular disk. Radiation from a disk adds an infrared excess to the expected spectral energy distribution of the revealed source. The detailed shape of this infrared excess depends on whether the disk is largely passive and merely reprocesses stellar photons, or is relatively massive and actively accreting. Both extremes of spectral shapes are observed in T Tauri stars; the amount of circumstellar material in the form of disks around nearly formed stars may be related to the dual issues of the origins of binary-star and planetary systems.

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Ariznabarreta, Gerardo, Juan C. García-Ardila, Manuel Mañas, and Francisco Marcellán. "Matrix biorthogonal polynomials on the real line: Geronimus transformations." Bulletin of Mathematical Sciences 09, no. 02 (2019): 1950007. http://dx.doi.org/10.1142/s1664360719500073.

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In this paper, Geronimus transformations for matrix orthogonal polynomials in the real line are studied. The orthogonality is understood in a broad sense, and is given in terms of a nondegenerate continuous sesquilinear form, which in turn is determined by a quasi-definite matrix of bivariate generalized functions with a well-defined support. The discussion of the orthogonality for such a sesquilinear form includes, among others, matrix Hankel cases with linear functionals, general matrix Sobolev orthogonality and discrete orthogonal polynomials with an infinite support. The results are mainly concerned with the derivation of Christoffel-type formulas, which allow to express the perturbed matrix biorthogonal polynomials and its norms in terms of the original ones. The basic tool is the Gauss–Borel factorization of the Gram matrix, and particular attention is paid to the non-associative character, in general, of the product of semi-infinite matrices. The Geronimus transformation in which a right multiplication by the inverse of a matrix polynomial and an addition of adequate masses are performed, is considered. The resolvent matrix and connection formulas are given. Two different methods are developed. A spectral one, based on the spectral properties of the perturbing polynomial, and constructed in terms of the second kind functions. This approach requires the perturbing matrix polynomial to have a nonsingular leading term. Then, using spectral techniques and spectral jets, Christoffel–Geronimus formulas for the transformed polynomials and norms are presented. For this type of transformations, the paper also proposes an alternative method, which does not require of spectral techniques, that is valid also for singular leading coefficients. When the leading term is nonsingular, a comparison of between both methods is presented. The nonspectral method is applied to unimodular Christoffel perturbations, and a simple example for a degree one massless Geronimus perturbation is given.

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Mendelson, Shahar, and Grigoris Paouris. "On the singular values of random matrices." Journal of the European Mathematical Society 16, no. 4 (2014): 823–34. http://dx.doi.org/10.4171/jems/448.

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Tío Sáenz, Marta. "The lemmatization of Old English Verbs from the second weak class on a lexical database." Journal of English Studies 13 (December 15, 2015): 135. http://dx.doi.org/10.18172/jes.2861.

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This article compiles a list of lemmas of the second class weak verbs of Old English by using the latest version of the lexical database Nerthus, which incorporates the texts of the Dictionary of Old English Corpus. Out of all the inflecional endings, the most distinctive have been selected for lemmatization: the infinitive, the inflected infinitive, the present participle, the past participle, the second person present indicative singular, the present indicative plural, the present subjunctive singular, the first and third person of preterite indicative singular, the second person of the preterite indicative singular, the preterite indicative plural and the preterite subjunctive plural. When it is necessary to regularize, normalization is restricted to correspondences based on dialectal and diachronic variation. The analysis turns out a total of 1,064 lemmas of weak verbs from the second class.

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Calsamiglia, Gabriel, Bertrand Deroin, Sidney Frankel, and Adolfo Guillot. "Singular sets of holonomy maps for algebraic foliations." Journal of the European Mathematical Society 15, no. 3 (2013): 1067–99. http://dx.doi.org/10.4171/jems/386.

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Naber, Aaron, and Daniele Valtorta. "The singular structure and regularity of stationary varifolds." Journal of the European Mathematical Society 22, no. 10 (2020): 3305–82. http://dx.doi.org/10.4171/jems/987.

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Avelin, Benny, Ugo Gianazza, and Sandro Salsa. "Boundary estimates for certain degenerate and singular parabolic equations." Journal of the European Mathematical Society 18, no. 2 (2016): 381–424. http://dx.doi.org/10.4171/jems/593.

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Putra, Adi. "THE SINGLE AND PLURAL PHRASES IN MATTHEW 4:16 AND THEIR MEANINGS." MAHABBAH: Journal of Religion and Education 2, no. 1 (2021): 17–33. http://dx.doi.org/10.47135/mahabbah.v2i1.20.

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Matthew 4:16 finds both singular and plural phrases. This phrase is very interesting to study because the context of this verse is in Galilee, a place where Jesus spent most of his time serving. Through qualitative research with an exegetical study approach, the researcher found that the results and conclusions were that the purpose of singular and plural phrases in these verses was: a singular phrase for Jews and a plural phrase for other nations. Thus, it can provide the theological understanding that Jesus' mission in Galilee was not only for the Jews who were there, but also for other nations who had long settled there even before the time of Jesus.

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28

Geisser, Thomas, and Alexander Schmidt. "Tame class field theory for singular varieties over finite fields." Journal of the European Mathematical Society 19, no. 11 (2017): 3467–88. http://dx.doi.org/10.4171/jems/744.

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Liao, Lingmin, Ronggang Shi, Omri Solan, and Nattalie Tamam. "Hausdorff dimension of weighted singular vectors in $\mathbb R^2$." Journal of the European Mathematical Society 22, no. 3 (2019): 833–75. http://dx.doi.org/10.4171/jems/934.

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30

Boccato, Chiara, Christian Brennecke, Serena Cenatiempo, and Benjamin Schlein. "The excitation spectrum of Bose gases interacting through singular potentials." Journal of the European Mathematical Society 22, no. 7 (2020): 2331–403. http://dx.doi.org/10.4171/jems/966.

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Backelin, Erik, and Kobi Kremnitzer. "Singular localization of $\mathfrak{g}$-modules and applications to representation theory." Journal of the European Mathematical Society 17, no. 11 (2015): 2763–87. http://dx.doi.org/10.4171/jems/570.

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32

Park, Jinyeong, David Poyato, and Juan Soler. "Filippov trajectories and clustering in the Kuramoto model with singular couplings." Journal of the European Mathematical Society 23, no. 10 (2021): 3193–278. http://dx.doi.org/10.4171/jems/1081.

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Guédon, Olivier, Alexander Litvak, Alain Pajor, and Nicole Tomczak-Jaegermann. "On the interval of fluctuation of the singular values of random matrices." Journal of the European Mathematical Society 19, no. 5 (2017): 1469–505. http://dx.doi.org/10.4171/jems/697.

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34

Ekeland, Ivar, and Éric Séré. "A surjection theorem for maps with singular perturbation and loss of derivatives." Journal of the European Mathematical Society 23, no. 10 (2021): 3323–49. http://dx.doi.org/10.4171/jems/1086.

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35

Germinet, François, and Abel Klein. "A comprehensive proof of localization for continuous Anderson models with singular random potentials." Journal of the European Mathematical Society 15, no. 1 (2013): 53–143. http://dx.doi.org/10.4171/jems/356.

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36

Langermann, Y. Tzvi. "Three singular treatises from Yemeni manuscripts." Bulletin of the School of Oriental and African Studies 54, no. 3 (1991): 568–71. http://dx.doi.org/10.1017/s0041977x00000902.

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I should like to discuss briefly three Arabic treatises that are quite different from one another with regard to content, authorship, and provenance. They do, however, share one interesting feature. Each one survives in just two manuscript copies, both in a Yemeni hand, the one in Arabic script, the other also in the Arabic language but written in Hebrew characters. The circumstances of their survival are instructive concerning the intellectual histories of both Jews and Muslims in the Yemen, and especially with regard to the relationships that obtained between these two communities. We may also add that none of these treatises, each of which is of some interest to its respective field, has been the subject of even a cursory study.

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GRÀCIA, XAVIER, and RUBÉN MARTÍN. "GEOMETRIC ASPECTS OF TIME-DEPENDENT SINGULAR DIFFERENTIAL EQUATIONS." International Journal of Geometric Methods in Modern Physics 02, no. 04 (2005): 597–618. http://dx.doi.org/10.1142/s0219887805000697.

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A geometric framework for describing and solving time-dependent implicit differential equations F(t,x,x′) = 0 is studied, paying special attention to the linearly singular case, where F is affine in the velocities: A(t,x)x′ = b(t,x). This framework is based on the jet bundle of a time-dependent configuration space, and is an extension of the geometric framework of the autonomous case. When A is a singular matrix, the solutions can be obtained by means of constraint algorithms, either directly or through an equivalent autonomous system that can be constructed using the vector hull functor of affine spaces. As applications, we consider the jet bundle description of time-dependent lagrangian systems and the Skinner–Rusk formulation of time-dependent mechanics.

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Enciso, Alberto, Arick Shao, and Bruno Vergara. "Carleman estimates with sharp weights and boundary observability for wave operators with critically singular potentials." Journal of the European Mathematical Society 23, no. 10 (2021): 3459–95. http://dx.doi.org/10.4171/jems/1105.

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39

Kraemer, Ross S. "On the Meaning of the Term “Jew” in Greco-Roman Inscriptions." Harvard Theological Review 82, no. 1 (1989): 35–53. http://dx.doi.org/10.1017/s0017816000016011.

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The Greek terms Ἰουδαῖος/Ἰουδαία and their Latin equivalents Iudaeus/Iudaea have rarely posed serious translation problems for scholars. Whether in masculine or feminine form, singular or plural, regardless of declension, these terms have usually been taken as straightforward indicators of Jews, at least when applied to individual persons. Only recently A. T. Kraabel has suggested that these terms, uniformly translated “Jew” or “Jews,” might have other significance, in particular as indicators of geographic origin, that is, “Judaean(s).”

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Bozorgi, Mehdi. "A Mode-Matching Solution for TE-Backscattering from an Arbitrary 2D Rectangular Groove in a PEC." Journal of Electromagnetic Engineering and Science 20, no. 3 (2020): 159–63. http://dx.doi.org/10.26866/jees.2020.20.3.159.

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In this paper, the simple yet effective mode-matching technique is utilized to compute TE-backscattering from a 2D filled rectangular groove in an infinite perfect electric conductor (PEC). The tangential magnetic fields inside and outside of the groove are represented as the sums of infinite series of cosine harmonics (half-range Fourier cosine series). By applying the continuity of the tangential magnetic field, these modes are matched on the groove to obtain the series coefficients by solving a system of linear equations. For this purpose, some oscillatory logarithmic singular integrals involving Hankel and trigonometric functions are solved numerically, starting by removing the logarithmic singularity via integration by parts. In the following, the new well-behaved highly oscillatory integrals are computed using efficient methods, and several comparisons are made to demonstrate the validity and ability of the presented procedure.

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Larkoski, Andrew, Ian Moult, and Duff Neill. "Measuring Two Angularities on a Single Jet." International Journal of Modern Physics: Conference Series 37 (January 2015): 1560046. http://dx.doi.org/10.1142/s2010194515600460.

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We present an analysis of the complete singular phase space of a jet when multiple measurements have been made about the jet structure. Using Soft-Collinear Effective Field Theory, strict factorization theorems are found only for the boundaries of physical phase space in these multi-differential cross-sections. These theorems have incompatible evolution equations, but nonetheless, a resummation ansazt can be found that interpolates between the boundaries. While logarithmic accuracy cannot be guaranteed in the bulk of phase space, the ansazt reproduces the correct resummation exactly at any boundary. Aside from jet physics, applications to more exclusive PDF's and Drell-Yan event shapes are indicated.

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Ben-Zvi, David, David Nadler, and Anatoly Preygel. "A spectral incarnation of affine character sheaves." Compositio Mathematica 153, no. 9 (2017): 1908–44. http://dx.doi.org/10.1112/s0010437x17007278.

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We present a Langlands dual realization of the putative category of affine character sheaves. Namely, we calculate the categorical center and trace (also known as the Drinfeld center and trace, or categorical Hochschild cohomology and homology) of the affine Hecke category starting from its spectral presentation. The resulting categories comprise coherent sheaves on the commuting stack of local systems on the two-torus satisfying prescribed support conditions, in particular singular support conditions, which appear in recent advances in the geometric Langlands program. The key technical tools in our arguments are a new descent theory for coherent sheaves or ${\mathcal{D}}$-modules with prescribed singular support and the theory of integral transforms for coherent sheaves developed in the companion paper by Ben-Zvi et al. [Integral transforms for coherent sheaves, J. Eur. Math. Soc. (JEMS), to appear].

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Liu, Bin, Hua Zhang, Li-Bin Fu, et al. "Ion jet generation in the ultraintense laser interactions with rear-side concave target." Laser and Particle Beams 28, no. 2 (2010): 351–59. http://dx.doi.org/10.1017/s0263034610000303.

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AbstractIn this paper, the ion jet generation from the interaction of an ultraintense laser pulse and a rear-side concave target is investigated analytically using a simple fluid model. We find that the ion expanding surface at the rear-side is distorted due to a strong charge-separation field, and that this distortion becomes dramatic with a singular cusp shown on the central axis at a critical time. The variation of the transverse ion velocity and the relative ion density diverge on the cusp, signaling the emergence of an on-axis ion jet. We have obtained analytical expressions for the critical time and the maximum velocity of the ion jet, and suggested an optimum shape for generating a collimated energetic ion jet. The above theoretical analysis has been verified by particle-in-cell (PIC) numerical simulations.

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Aziz, 'Aqilah. "‘Me inda nampak’ – Pronoun Use in Malay-English Codemixed Social Media Texts." J-Lalite: Journal of English Studies 1, no. 2 (2020): 94. http://dx.doi.org/10.20884/1.jes.2020.1.2.3482.

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This paper investigates the use of English the first-person singular object pronoun ‘me’ as a subject in conversation on WhatsApp and Telegram between university students in their twenties. It was found that the feature occurs more when interlocutors are code switching, especially in paired chats when ‘me’ often replaces the Malay pronoun aku or saya. This paper explores reasons for this, and how this feature has come to be used in synchronous electronically mediated conversations between young Bruneians. The findings show that using ‘me’ serves as a polite speech marker which is perceived as a softer expression than Malay aku in conversations, depending on the interlocutors.

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DZIERŻON, GINTER. "Nieskuteczność aktu administracyjnego (kan. 38 KPK)." Prawo Kanoniczne 59, no. 3 (2017): 19. http://dx.doi.org/10.21697/pk.2016.59.3.02.

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W zaprezentowanym opracowaniu Autor dokonał szczegółowej interpretacji kan. 38 KPK. Z przeprowadzonych analiz wynika, iż w kan. 38 KPK określono zasady dotyczące nieskuteczności poszczególnego aktu administracyjnego tylko z jednej perspektywy, jaką jest zawartość aktu. Przyjęte w tej regulacji rozwiązania pozostają w ścisłym związku z zasadą legalności. Według Autora, ustawodawca kościelny jest daleki od pozytywistycznego legalizmu. Stwarza on bowiem możliwość dołączenia klauzuli derogacyjnej odnoszącej się do konkretnego przypadku. Stoi on na stanowisku, że takie rozwiązania jest konieczne, gdyż ustawa nie może stać się jedynym punktem odniesienia w wykonywaniu władzy. Sytuacje bowiem mające miejsce w przypadku sprawowania władzy administracyjnej niejednokrotnie charakteryzują się szczególnością. Wprowadzenie zatem tego typu klauzul należy uznać za „normae singulares”.

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46

STANSBY, P. K., A. CHEGINI, and T. C. D. BARNES. "The initial stages of dam-break flow." Journal of Fluid Mechanics 374 (November 10, 1998): 407–24. http://dx.doi.org/10.1017/s0022112098001918.

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Experiments have been undertaken to investigate dam-break flows where a thin plate separating water at different levels is withdrawn impulsively in a vertically upwards direction. Depth ratios of 0, 0.1 and 0.45 were investigated for two larger depth values of 10 cm and 36 cm. The resulting sequence of surface profiles is shown to satisfy approximately Froude scaling. For the dry-bed case a horizontal jet forms at small times and for the other cases a vertical, mushroom-like jet occurs, none of which have been observed previously. We analyse the initial-release problem in which the plate is instantaneously removed or dissolved. Although this shows singular behaviour, jet-like formations are predicted. Artificially smoothing out the singularity enables a fully nonlinear, potential-flow computation to follow the jet formation for small times. There is qualitative agreement between theory and experiment.In the experiments, after a bore has developed downstream as a result of highly complex flow interactions, the surface profiles agree remarkably well with exact solutions of the shallow-water equations which assume hydrostatic pressure and uniform velocity over depth.

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47

STANSBY, P. K., A. CHEGINI, and T. C. D. BARNES. "The initial stages of dam-break flow." Journal of Fluid Mechanics 374 (November 10, 1998): 407–24. http://dx.doi.org/10.1017/s0022112098009975.

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Experiments have been undertaken to investigate dam-break flows where a thin plate separating water at different levels is withdrawn impulsively in a vertically upwards direction. Depth ratios of 0, 0.1 and 0.45 were investigated for two larger depth values of 10 cm and 36 cm. The resulting sequence of surface profiles is shown to satisfy approximately Froude scaling. For the dry-bed case a horizontal jet forms at small times and for the other cases a vertical, mushroom-like jet occurs, none of which have been observed previously. We analyse the initial-release problem in which the plate is instantaneously removed or dissolved. Although this shows singular behaviour, jet-like formations are predicted. Artificially smoothing out the singularity enables a fully nonlinear, potential-flow computation to follow the jet formation for small times. There is qualitative agreement between theory and experiment.In the experiments, after a bore has developed downstream as a result of highly complex flow interactions, the surface profiles agree remarkably well with exact solutions of the shallow-water equations which assume hydrostatic pressure and uniform velocity over depth.

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48

Norwood, Stephen H., and Eunice G. Pollack. "White Devils, Satanic Jews: The Nation of Islam From Fard to Farrakhan." Modern Judaism - A Journal of Jewish Ideas and Experience 40, no. 2 (2020): 137–68. http://dx.doi.org/10.1093/mj/kjaa006.

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Abstract This article explores how the American white far right—including the Christian Front, Christian Mobilizers, and Gerald L. K. Smith—helped shape the Nation of Islam’s (NOI) antisemitism during the 1930s and 1940s. It also examines the strong influence of Harlem’s pro-Axis Black Fuehrers on the NOI during World War II. Nation of Islam and white far-right propaganda were remarkably similar. Both embraced the Protocols of the Learned Elders of Zion, denied or minimized the Holocaust, and were virulently anti-Zionist. After elaborating on the context within which the Nation of Islam created its ideology, the article explores how the NOI, which originally identified whites, Christians and Jews as devils, adopted an almost singular emphasis on Jews as agents of Satan, the Star of David replacing the cross as the symbol of iniquity. Jews were not victims, but Blacks’ major victimizers; never slaves, but dominant enslavers; not progressives, but those who impeded Blacks’ advance. Instead of giving the world Hebrew Scripture, they converted it into the “Poison Book,” from the beginning crafting a “dirty religion,” which blessed the subjugation of black people, and denied God’s promise to the “Real Children of Israel.” These “imposter Jews” concealed that the Hebrew Bible was a prophecy about “the so-called Negroes of America”—the true “Chosen of God”—who would be in bondage for 400 years, strangers in a strange land.

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Schlesinger, Juliana Portenoy. "DENATURALIZING CULTURE: SAYED KASHUA'S NEWSPAPER COLUMNS ON THE TOPIC OF PREJUDICE." Sociologia & Antropologia 5, no. 3 (2015): 911–33. http://dx.doi.org/10.1590/2238-38752015v5311.

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Abstract Discrimination is a recurrent topic in the work of the Israeli-Arab writer Sayed Kashua. In the last couple of years, Sayed Kashua has moved away from writing about the prejudice expressed by his own Israeli Muslim community towards the Israeli Jewish population to focus his attention instead on the prejudice shown by Jews against Arabs in Israel. Self-criticism has always been a hallmark of Sayed Kashua's work so this shift indicates a significant change in the columnist's perception of his own society. Based on a survey of various issues relating to Israeli society, such as the law, the educational system and language, as well as a theoretical review of authors who observe a mutual alienation of Arabs and Jews in Israel, this article analyses several of Sayed Kashua's recent columns in the Israeli newspaper Haaretz. It also investigates how the author understands prejudice and, in a singular and surprising way, expresses his concerns and solutions to this problem.

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FREEMAN, JULIAN. "A SINGULAR VISION FIFTY YEARS OF PAINTING AT THE PORTAL GALLERY BY LAURA GASCOIGNE AND JESS WILDER." Art Book 16, no. 4 (2009): 75–76. http://dx.doi.org/10.1111/j.1467-8357.2009.01068_1.x.

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Journal articles on the topic 'Singular jets'

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