scholarly journals Magnetogenesis and the Cosmic Web: A Joint Challenge for Radio Observations and Numerical Simulations

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 109
Author(s):  
Franco Vazza ◽  
Nicola Locatelli ◽  
Kamlesh Rajpurohit ◽  
Serena Banfi ◽  
Paola Domínguez-Fernández ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Radio Signal ◽  
Radio Observations ◽  
Definitive Answer ◽  
Physical Connection ◽  
The Status ◽  
Radio Frequencies

The detection of the radio signal from filaments in the cosmic web is crucial to distinguish possible magnetogenesis scenarios. We review the status of the different attempts to detect the cosmic web at radio wavelengths. This is put into the context of the advanced simulations of cosmic magnetism carried out in the last few years by our MAGCOW project. While first attempts of imaging the cosmic web with the MWA and LOFAR have been encouraging and could discard some magnetogenesis models, the complexity behind such observations makes a definitive answer still uncertain. A combination of total intensity and polarimetric data at low radio frequencies that the SKA and LOFAR2.0 will achieve is key to removing the existing uncertainties related to the contribution of many possible sources of signal along deep lines of sight. This will make it possible to isolate the contribution from filaments, and expose its deep physical connection with the origin of extragalactic magnetism.

scholarly journals Numerical Simulations of Jets from Active Galactic Nuclei

Galaxies ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 24 ◽  
Author(s):  
José-María Martí
Keyword(s):  
Numerical Simulations ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Theoretical Models ◽  
The Status ◽  
Hydrodynamical Description ◽  
Jet Plasma ◽  
The Impact ◽  
Continuous Injection ◽  
Double Radio Galaxies

Numerical simulations have been playing a crucial role in the understanding of jets from active galactic nuclei (AGN) since the advent of the first theoretical models for the inflation of giant double radio galaxies by continuous injection in the late 1970s. In the almost four decades of numerical jet research, the complexity and physical detail of simulations, based mainly on a hydrodynamical/magneto-hydrodynamical description of the jet plasma, have been increasing with the pace of the advance in theoretical models, computational tools and numerical methods. The present review summarizes the status of the numerical simulations of jets from AGNs, from the formation region in the neighborhood of the supermassive central black hole up to the impact point well beyond the galactic scales. Special attention is paid to discuss the achievements of present simulations in interpreting the phenomenology of jets as well as their current limitations and challenges.

CARBON NANOTUBE FIELD-EFFECT TRANSISTORS

2006 ◽  
Vol 16 (04) ◽  
pp. 897-912 ◽  
Author(s):  
JING GUO ◽  
SIYURANGA O. KOSWATTA ◽  
NEOPHYTOS NEOPHYTOU ◽  
MARK LUNDSTROM
Keyword(s):  
Carbon Nanotube ◽  
Numerical Simulations ◽  
Field Effect ◽  
Field Effect Transistors ◽  
Device Physics ◽  
Challenges And Opportunities ◽  
The Status ◽  
Similarities And Differences ◽  
Device Technology

This paper discusses the device physics of carbon nanotube field-effect transistors (CNTFETs). After reviewing the status of device technology, we use results of our numerical simulations to discuss the physics of CNTFETs emphasizing the similarities and differences with traditional FETs. The discussion shows that our understanding of CNTFET device physics has matured to the point where experiments can be explained and device designs optimized. The paper concludes with some thoughts on challenges and opportunities for CNTFET electronics.

scholarly journals Variability and uncertainty of Track Circuit band-pass modeling for interference evaluation

ACTA IMEKO ◽  
2013 ◽  
Vol 2 (1) ◽  
pp. 32
Author(s):  
Andrea Mariscotti
Keyword(s):  
Degrees Of Freedom ◽  
Evaluation Process ◽  
Rolling Stock ◽  
Definitive Answer ◽  
Normative Approach ◽  
The Status ◽  
Track Circuits ◽  
Band Pass ◽  
Track Circuit ◽  
Added Uncertainty

When evaluating track circuits (TC) interference, the latest normative approach indicates the use of band-pass filters that emulate the TC receiver response. The rms value of the output, when compared to the interference limit, indicates whether a specific signal might create interference or not. The implementation of the filter has some degrees of freedom and needs thus to be characterized in terms of added uncertainty to the interference evaluation process. The latter is relevant to safety, strictly related to the incorrect assignment of the status of the track section monitored and protected by the TC itself. When giving a definitive answer about the immunity of a specific TC and the compatibility with the tested rolling stock, it is thus necessary to completely evaluate the uncertainty associated to the chosen model and to the related signal processing operations, even if - it is recognized - their influence may be considered of second order with respect to infrastructure and rolling stock non-idealities.

scholarly journals Comparison of Radio Observations and Numerical Simulations of the Radio Lobes of Cygnus A

2005 ◽  
Vol 620 (1) ◽  
pp. 126-144 ◽  
Author(s):  
Joel C. Carvalho ◽  
Ruth A. Daly ◽  
Matthew P. Mory ◽  
Christopher P. O’Dea
Keyword(s):  
Numerical Simulations ◽  
Radio Observations ◽  
Cygnus A

scholarly journals Binary Neutron Star and Short Gamma-Ray Burst Simulations in Light of GW170817

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 119 ◽  
Author(s):  
Antonios Nathanail
Keyword(s):  
Neutron Star ◽  
Gravitational Wave ◽  
Electromagnetic Radiation ◽  
Numerical Simulations ◽  
Gravitational Waves ◽  
Gamma Ray ◽  
Numerical Relativity ◽  
Gamma Ray Burst ◽  
Binary Neutron Star ◽  
The Status

In the dawn of the multi-messenger era of gravitational wave astronomy, which was marked by the first ever coincident detection of gravitational waves and electromagnetic radiation, it is important to take a step back and consider our current established knowledge. Numerical simulations of binary neutron star mergers and simulations of short GRB jets must combine efforts to understand such complicated and phenomenologically rich explosions. We review the status of numerical relativity simulations with respect to any jet or magnetized outflow produced after merger. We compare what is known from such simulations with what is used and obtained from short GRB jet simulations propagating through the BNS ejecta. We then review the established facts on this topic, as well as discuss things that need to be revised and further clarified.

scholarly journals Radio Observations of the γ-Ray Blazar 0528+134

1996 ◽  
Vol 175 ◽  
pp. 14-16
Author(s):  
M. Pohl ◽  
W. Reich ◽  
T. P. Krichbaum ◽  
K. Standke ◽  
S. Britzen ◽  
...  
Keyword(s):  
Energy Range ◽  
Radio Observations ◽  
The Status ◽  
Γ Ray ◽  
Lower Frequencies

We report multifrequency observations of the γ-ray blazar 0528+134 with the Effelsberg 100-m telescope, the IRAM 30-m telescope at Pico Veleta and the NRL Green Bank Interferometer. The observing methods are described elsewhere (Reich et al., 1993; Pohl et al., 1995). The radio lightcurves are given in Fig.1 in comparison to the status of 0528+134 in the EGRET energy range. The uncertainties in the flux densities quoted there are less than 5% at 10.55 GHz and lower frequencies, while slightly exceeding this value at 32 GHz and 86 GHz.

Radio Observations of Clusters of Galaxies

1967 ◽  
Vol 1 (1) ◽  
pp. 24-24
Author(s):  
B. Y. Mills ◽  
R. R. Shobbrook
Keyword(s):  
High Resolution ◽  
Luminosity Function ◽  
Radio Galaxies ◽  
Detailed Examination ◽  
Statistical Information ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Radio Observations ◽  
Radio Frequencies

High resolution studies of clusters of galaxies at radio frequencies may contribute substantially to our knowledge of the properties of radio galaxies, their evolution and their luminosity function. A considerable amount of statistical information is already available on the correspondence of radio sources and clusters; the present investigation is aimed rather at a detailed examination of the sources and their identification with actual galaxies or other objects.

scholarly journals Contribution of solar hydrogen Lyα line emission in total ionization rate in ionospheric D-region during the maximum of solar X-flare

2015 ◽  
pp. 51-57 ◽  
Author(s):  
A. Nina ◽  
V.M. Cadez ◽  
J. Bajcetic
Keyword(s):  
Numerical Simulations ◽  
Radio Signal ◽  
Line Emission ◽  
Ionization Rate ◽  
Solar Hydrogen ◽  
Total Ionization ◽  
D Region ◽  
Ionization Processes ◽  
Using Data ◽  
Analytical Expressions

The solar Ly? line emission can be considered as the dominant source of ionization processes in the ionospheric D-region at altitudes above 70 km during unperturbed conditions. However, large sudden impacts of radiation in some other energy domains can also significantly influence the ionization rate and, in this paper, we present a study on the contribution of Ly? radiation to the ionization rate when the ionosphere is disturbed by solar X-flares. We give relevant analytical expressions and make calculations and numerical simulations for the low ionosphere using data collected by the VLF receiver located in Serbia for the VLF radio signal emitted by the DHO transmitter in Germany.

Mr. Truman's War: A Debate and Its Aftermath

1969 ◽  
Vol 31 (2) ◽  
pp. 223-241
Author(s):  
Charles A. Lofgren
Keyword(s):  
United States Supreme Court ◽  
Federal District ◽  
The United States ◽  
State Courts ◽  
The Political ◽  
Definitive Answer ◽  
The People ◽  
The Status ◽  
Lower Courts ◽  
Technical Sense

“WeDoubt very much if there is any question in the minds of the majority of the people of this country that the conflict now raging in Korea can be anything but war,” wrote Federal District Judge Harry C. Westover in the spring of 1953. “Certainly those who have been called upon to suffer injury and maiming, or to sacrifice their lives,” he continued, “would be unanimous in their opinion that this is war — war in all of its horrible aspects.” What common sense dictated, the judge didnot deny. Yet, although federal and state courts in this and several other instances touched tangentially on the question of whether the Korean conflict was a war in a legal and technical sense, on balance they produced no definitive answer. The United States Supreme Court, moreover, refused to hear any of the cases in question. But the lower courts ofthe nation were not alone in their diversity of opinion regarding the status of the war. The political branches of the Federal Government similarly displayed little agreement on the parallel issue of what the legal basis was for American participation in the Korean venture.

VARIATIONS IN METEORIC RADIO SIGNAL DECAY RATES

1963 ◽  
Vol 41 (4) ◽  
pp. 679-690 ◽  
Author(s):  
D. W. Rice ◽  
P. A. Forsyth
Keyword(s):  
Radio Signal ◽  
Decay Rates ◽  
Simple Function ◽  
Large Scatter ◽  
Forward Scatter ◽  
Signal Decay ◽  
Meteor Trail ◽  
Rate Of Decay ◽  
Radio Frequencies

The rate of decay of the radio signal reflected from an underdense meteor trail is usually considered to be a simple function of trail height. In fact a large scatter is found in decay rates measured by means of radar or backscatter observations and this dispersion persists for forward-scatter measurements, where the decay rates can be measured with greater precision. The scatter persists even for measurements made at different radio frequencies on the same trail. The results of calculations are presented which indicate that the observed degree of variation in decay rates could result from nonuniformities in the trail ionization.

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