scholarly journals Learning Latent Jet Structure

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1167
Author(s):  
Barry M. Dillon ◽  
Darius A. Faroughy ◽  
Jernej F. Kamenik ◽  
Manuel Szewc
Keyword(s):  
Recent Work ◽  
Statistical Models ◽  
Latent Dirichlet Allocation ◽  
Formation Processes ◽  
Jet Substructure ◽  
Physical Processes ◽  
Jet Formation ◽  
Mixed Sample ◽  
Mixed Membership Models ◽  
Jet Structure

We summarize our recent work on how to infer on jet formation processes directly from substructure data using generative statistical models. We recount in detail how to cast jet substructure observables’ measurements in terms of Bayesian mixed membership models, in particular Latent Dirichlet Allocation. Using a mixed sample of QCD and boosted tt¯ jet events and focusing on the primary Lund plane observable basis for event measurements, we show how using educated priors on the latent distributions allows to infer on the underlying physical processes in a semi-supervised way.

scholarly journals The limb-brightened jet of M87 down to the 7 Schwarzschild radii scale

2018 ◽  
Vol 616 ◽  
pp. A188 ◽  
Author(s):  
J.-Y. Kim ◽  
T. P. Krichbaum ◽  
R.-S. Lu ◽  
E. Ros ◽  
U. Bach ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Angular Resolution ◽  
Magnetic Energy ◽  
Large Mass ◽  
High Angular Resolution ◽  
Data Sets ◽  
Jet Formation ◽  
Physical Conditions ◽  
Self Similar ◽  
Jet Structure

Messier 87 (M 87) is one of the nearest radio galaxies with a prominent jet extending from sub-pc to kpc scales. Because of its proximity and the large mass of its central black hole (BH), it is one of the best radio sources for the study of jet formation. We study the physical conditions near the jet base at projected separations from the BH of ~7–100 Schwarzschild radii (Rsch). Global mm-VLBI Array (GMVA) observations at 86 GHz (λ = 3.5 mm) provide an angular resolution of ~50 μas, which corresponds to a spatial resolution of only 7 Rsch and reach the small spatial scale. We use five GMVA data sets of M 87 obtained from 2004 to 2015 and present new high angular resolution VLBI maps at 86 GHz. In particular, we focus on the analysis of the brightness temperature, the jet ridge lines, and the ratio of jet to counter-jet. The imaging reveals a parabolically expanding limb-brightened jet which emanates from a resolved VLBI core of ~(8–13) Rsch in size. The observed brightness temperature of the core at any epoch is ~(1–3) × 1010 K, which is below the equipartition brightness temperature and suggests magnetic energy dominance at the jet base. We estimate the diameter of the jet at its base to be ~5 Rsch assuming a self-similar jet structure. This suggests that the sheath of the jet may be anchored in the very inner portion of the accretion disk. The image stacking reveals faint emission at the center of the edge-brightened jet on sub-pc scales. We discuss its physical implication within the context of the spine-sheath structure of the jet.

scholarly journals Theory of Dwarf Novae

1976 ◽  
Vol 73 ◽  
pp. 173-192
Author(s):  
G. T. Bath
Keyword(s):  
Mass Transfer ◽  
Steady State ◽  
Recent Work ◽  
Accretion Disc ◽  
Optical Behaviour ◽  
Dwarf Novae ◽  
Physical Processes ◽  
Dwarf Nova ◽  
Theoretical Results

Recent work on the physical processes resulting from mass transfer between the red and blue components of dwarf nova binaries is reviewed. The optical behaviour of the blue component's accretion disc suggests that it may be the infall, accretion energy which is being liberated during outbursts. Theoretical results which suggest that the red component may suffer quasi-periodic mass transfer instabilities are discussed. The resulting accretion disc properties are considered and compared with the observed optical outburst behaviour for the simplest steady state disc models. The complexity of the interaction between the two stellar components in these systems is emphasized.

Some topical issues in research on short-pulse laser-produced plasmas

1980 ◽  
Vol 298 (1439) ◽  
pp. 351-364 ◽  
Keyword(s):  
Recent Work ◽  
Pulse Laser ◽  
Short Pulse ◽  
Fast Time ◽  
Physical Processes ◽  
Time Resolved ◽  
X Ray ◽  
Short Pulse Laser ◽  
Laser Facility ◽  
Interaction Phenomena

A brief review is presented of the main physical processes in laser-produced plasmas. This is followed by illustrations taken from recent work at the S.R.C. Central Laser Facility of the use of X-ray and visible streak cameras for fast time resolved measurements of implosion and interaction phenomena in laser-produced plasmas.

scholarly journals Documentary and ecosemiotics: Frames and faces in the work of Johan van der Keuken

2016 ◽  
Vol 44 (1/2) ◽  
pp. 186-208
Author(s):  
Hing Tsang
Keyword(s):  
Recent Work ◽  
20Th Century ◽  
Coastal Area ◽  
Western Europe ◽  
Urban Environments ◽  
Human Beings ◽  
Physical Processes ◽  
Natural Habitats ◽  
Late 20Th Century ◽  
The Relationship

This article argues that the work of the late Johan van der Keuken offers a contribution to ecological semiotics, and that it also defines the relationship between the semiotic animal and nature in ways that avoid glottocentricism. Taking from the recent work of Kalevi Kull, Jesper Hoffmeyer, and John Deely amongst others, I will argue that van der Keuken’s documentaries offer a view of ecology that is broader than a study of bio-physical processes that might reduce ecology to a narrow political issue.In order to support this argument, I will be looking at two contrasting films from van der Keuken – Flat Jungle (1978) and Face Value (1991). The first film examines natural habitats within a confined coastal area in Western Europe, while the second film looks at human beings in the different urban environments of late-20th-century Europe. I will then argue that van der Keuken does not collapse the vital distinctions between umwelt and Lebenswelt, yet his films also succeed at reminding us of their constant interdependence.

scholarly journals Sound Symbolism in Baseball Player Names

Names ◽  
2021 ◽  
Vol 69 (1) ◽  
pp. 20-35
Author(s):  
Stephanie S. Shih ◽  
Deniz Rudin
Keyword(s):  
Recent Work ◽  
Real World ◽  
Major League Baseball ◽  
Sound Symbolism ◽  
Baseball Player ◽  
Formation Processes ◽  
Major League ◽  
Physical Attributes ◽  
Naming Practices

Recent work has argued that sound symbolism plays a much larger part in language than previously believed, given the assumption of the arbitrariness of the sign. A slate of recent papers on Pokémonastics, for example, has found sound symbolic associations to be rampant in Pokémon names cross-linguistically. In this paper, we explore a real-world dataset that parallels Pokémon, in which human players similarly have physical attributes of weight, height, and power: Major League Baseball. We investigated phonological correlations between baseball player statistics and their given first names, chosen baseball-official first names,and baseball nicknames. We found numerous sound symbolic associations in player-chosen names and nicknames, where conscious design may play a role in choosing a name that communicates an attribute. These associations were often mediated by language-specific hypocoristic formation processes. We conclude that sound symbolism occurs in real-world naming practices, but only when names are chosen in cognizance of the relevant attributes.

scholarly journals Inverse reconstruction of jet structure from off-axis gamma-ray burst afterglows

2020 ◽  
Vol 497 (1) ◽  
pp. 1217-1235
Author(s):  
Kazuya Takahashi ◽  
Kunihito Ioka
Keyword(s):  
Gamma Ray ◽  
Standard Theory ◽  
Inversion Method ◽  
Jet Formation ◽  
Gamma Ray Burst ◽  
Inverse Reconstruction ◽  
Wave Event ◽  
Novel Method ◽  
Jet Structure ◽  
High Cadence

ABSTRACT The gravitational wave event GW 170817 and the slowly rising afterglows of short gamma-ray burst (GRB) 170817A clearly suggest that the GRB jet has an angular structure. However the actual jet structure remains unclear as different authors give different structures. We formulate a novel method to inversely reconstruct the jet structure from off-axis GRB afterglows, without assuming any functional form of the structure in contrast to the previous studies. The jet structure is uniquely determined from the rising part of a light curve for a given parameter set by integrating an ordinary differential equation, which is derived from the standard theory of GRB afterglows. Applying to GRB 170817A, we discover that a non-trivial hollow-cone jet is consistent with the observed afterglows, as well as Gaussian and power-law jets within errors, which implies the Blandford–Znajek mechanism or ejecta–jet interaction. The current observations only constrain the jet core, not in principle the outer jet structure around the line of sight. More precise and high-cadence observations with our inversion method will fix the jet structure, providing a clue to the jet formation and propagation.

scholarly journals pong: fast analysis and visualization of latent clusters in population genetic data

2015 ◽  
Author(s):  
Aaron A. Behr ◽  
Katherine Z. Liu ◽  
Gracie Liu-Fang ◽  
Priyanka Nakka ◽  
Sohini Ramachandran
Keyword(s):  
Population Structure ◽  
Latent Dirichlet Allocation ◽  
Broad Class ◽  
Interactive Visualization ◽  
Multilocus Genotype ◽  
Single Nucleotide Variants ◽  
Fast Analysis ◽  
Text Corpora ◽  
Order Of Magnitude ◽  
Mixed Membership Models

Abstract1MotivationA series of methods in population genetics use multilocus genotype data to assign individuals membership in latent clusters. These methods belong to a broad class of mixed-membership models, such as latent Dirichlet allocation used to analyze text corpora. Inference from mixed-membership models can produce different output matrices when repeatedly applied to the same inputs, and the number of latent clusters is a parameter that is often varied in the analysis pipeline. For these reasons, quantifying, visualizing, and annotating the output from mixed-membership models are bottlenecks for investigators across multiple disciplines from ecology to text data mining.2ResultsWe introduce pong, a network-graphical approach for analyzing and visualizing membership in latent clusters with a native D3.js interactive visualization. pong leverages efficient algorithms for solving the Assignment Problem to dramatically reduce runtime while increasing accuracy compared to other methods that process output from mixed-membership models. We apply pong to 225,705 unlinked genome-wide single-nucleotide variants from 2,426 unrelated individuals in the 1000 Genomes Project, and identify previously overlooked aspects of global human population structure. We show that pong outpaces current solutions by more than an order of magnitude in runtime while providing a customizable and interactive visualization of population structure that is more accurate than those produced by current tools.3Availabilitypong is freely available and can be installed using the Python package management system pip. pong’s source code is available at https://github.com/abehr/[email protected],[email protected]

scholarly journals FORMATION AND COLLIMATION OF RELATIVISTIC MHD JETS — SIMULATIONS AND RADIO MAPS

2014 ◽  
Vol 28 ◽  
pp. 1460190 ◽  
Author(s):  
CHRISTIAN FENDT ◽  
OLIVER PORTH ◽  
SOMAYEH SHEIKHNEZAMI
Keyword(s):  
Accretion Rate ◽  
The Self ◽  
High Mass ◽  
Jet Formation ◽  
Mhd Simulations ◽  
Mass Fluxes ◽  
Magnetic Diffusivity ◽  
High Degree ◽  
Jet Structure ◽  
First Time

We present results of magnetohydrodynamic (MHD) simulations of jet formation and propagation, discussing a variety of astrophysical setups. In the first approach we consider simulations of relativistic MHD jet formation, considering jets launched from the surface of a Keplerian disk, demonstrating numerically — for the first time — the self-collimating ability of relativistic MHD jets. We obtain Lorentz factors up to ≃ 10 while acquiring a high degree of collimation of about 1 degree. We then present synchrotron maps calculated from the intrinsic jet structure derived from the MHD jet formation simulation. We finally present (non-relativistic) MHD simulations of jet lauching, treating the transition between accretion and ejection. These setups include a physical magnetic diffusivity which is essential for loading the accretion material onto the outflow. We find relatively high mass fluxes in the outflow, of the order of 20-40% of the accretion rate.

scholarly journals The Early Evolution of Massive Black Holes

2009 ◽  
Vol 5 (S267) ◽  
pp. 26-33 ◽  
Author(s):  
Marta Volonteri
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Velocity Dispersion ◽  
Host Galaxy ◽  
Formation Processes ◽  
Hole Formation ◽  
Physical Processes ◽  
Massive Black Hole ◽  
Potential Wells ◽  
Massive Black Holes

AbstractMassive black holes (MBHs) are nowadays believed to reside in most local galaxies. Studies have also established a number of relations between the MBH mass and properties of the host galaxy such as bulge mass and velocity dispersion. These results suggest that central MBHs, while much less massive than their hosts (~ 0.1%), are linked to the evolution of galactic structure. When did it all start? In hierarchical cosmologies, a single big galaxy today can be traced back to the stage when it was split up in hundreds of smaller components. Did MBH seeds form with the same efficiency in small proto-galaxies, or did their formation have to await the buildup of substantial galaxies with deeper potential wells? I briefly review here some of the physical processes that are conducive to the evolution of the massive black hole population. I will discuss black hole formation processes for “seed” black holes that are likely to take place at early cosmic epochs, and possible observational tests of these scenarios.

Shocks in Molecular Clouds

1996 ◽  
Vol 13 (3) ◽  
pp. 268-271
Author(s):  
Peter W. J. L. Brand
Keyword(s):  
Numerical Modelling ◽  
Statistical Models ◽  
Molecular Clouds ◽  
Gas Flow ◽  
Molecular Gas ◽  
Physical Processes ◽  
Star Forming ◽  
Nonlinear Growth ◽  
Star Forming Regions ◽  
Shock Dynamics

AbstractA one-day workshop discussed the properties of shocks in star-forming regions. It also reviewed other physical processes in star-forming molecular gas, and the progress in numerical modelling of such physics. Discussion concentrated on the complexity which instabilities in the gas flow bring to the analysis of shocks. The consensus was that progress will be made as the spatial/spectral resolution of shock measurements improves, and as numerical modelling of the nonlinear growth of instabilities becomes possible, potentially leading to statistical models of shock dynamics.

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