scholarly journals Soft radiation from scattering amplitudes revisited

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
A. Manu ◽  
Debodirna Ghosh ◽  
Alok Laddha ◽  
P. V. Athira
Keyword(s):  
Scattering Amplitudes ◽  
Gravitational Radiation ◽  
Classical Limit ◽  
Low Frequency ◽  
Soft Photon ◽  
Leading Order ◽  
Gravitational Fields ◽  
Electro Magnetic ◽  
Soft Radiation ◽  
The Way

Abstract We apply the recently developed formalism by Kosower, Maybee and O’Connell (KMOC) [12] to analyse the soft electromagnetic and soft gravitational radiation emitted by particles without spin in D ≥ 4 dimensions. We use this formalism in conjunction with quantum soft theorems to derive radiative electro-magnetic and gravitational fields in low frequency expansion and upto next to leading order in the coupling. We show that in all dimensions, the classical limit of sub-leading soft (photon and graviton) theorems is consistent with the classical soft theorems proved by Sen et al. in a series of papers. In particular in [11] Saha, Sahoo and Sen proved classical soft theorems for electro-magnetic and gravitational radiation in D = 4 dimensions. For the class of scattering processes that can be analyzed using KMOC formalism, we show that the classical limit of quantum soft theorems is consistent with the D = 4 classical soft theorems, paving the way for their proof from scattering amplitudes.

scholarly journals Spurious poles in the scattering of electric and magnetic charges

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
John Terning ◽  
Christopher B. Verhaaren
Keyword(s):  
Perturbation Theory ◽  
Scattering Amplitudes ◽  
Pair Production ◽  
Magnetic Particles ◽  
Single Photon ◽  
Low Energy ◽  
Magnetic Interactions ◽  
Parity Conservation ◽  
Non Local ◽  
The Way

Abstract Theories with both electric and magnetic charges (“mutually non-local” theories) have several major obstacles to calculating scattering amplitudes. Even when the interaction arises through the kinetic mixing of two, otherwise independent, U(1)’s, so that all low-energy interactions are perturbative, difficulties remain: using a self-dual, local formalism leads to spurious poles at any finite order in perturbation theory. Correct calculations must show how the spurious poles cancel in observable scattering amplitudes. Consistency requires that one type of charge is confined as a result of one of the U(1)’s being broken. Here we show how the constraints of confinement and parity conservation on observable processes manages to cancel the spurious poles in scattering and pair production amplitudes, paving the way for systematic studies of the experimental signatures of “dark” electric-magnetic processes. Along the way we demonstrate some novel effects in electric-magnetic interactions, including that the amplitude for single photon production of magnetic particles by electric particles vanishes.

scholarly journals The perturbation of electromagnetic fields at distances that are large compared with the object's size

2014 ◽  
Vol 80 (3) ◽  
pp. 865-892 ◽  
Author(s):  
Paul D Ledger ◽  
William R B Lionheart
Keyword(s):  
Magnetic Fields ◽  
Electromagnetic Fields ◽  
Asymptotic Expansions ◽  
Low Frequency ◽  
Perfect Conductor ◽  
Small Object ◽  
Leading Order ◽  
Material Parameters ◽  
Electric And Magnetic Fields

Abstract We rigorously derive the leading-order terms in asymptotic expansions for the scattered electric and magnetic fields in the presence of a small object at distances that are large compared with its size. Our expansions hold for fixed wavenumber when the scatterer is a (lossy) homogeneous dielectric object with constant material parameters or a perfect conductor. We also derive the corresponding leading-order terms in expansions for the fields for a low-frequency problem when the scatterer is a non-lossy homogeneous dielectric object with constant material parameters or a perfect conductor. In each case, we express our results in terms of polarization tensors.

The Effect of Electromagnetic Vibration on the Structure Control of A356 Alloy

2007 ◽  
Vol 539-543 ◽  
pp. 329-332 ◽  
Author(s):  
Jung Pyung Choi ◽  
Tae Woon Nam ◽  
Eui Pak Yoon
Keyword(s):  
Structural Control ◽  
Eutectic Silicon ◽  
A356 Alloy ◽  
Low Frequency ◽  
Primary Aluminum ◽  
Magnetic Flux Density ◽  
Structure Control ◽  
Electromagnetic Vibration ◽  
Fine Fiber ◽  
Electro Magnetic

The structural control of A356 alloy, which was not studied among various electromagnetic processing of materials, was considered applying the alternating current and direct current magnetic flux density. The main aim of the present study is to investigate the effects of electromagnetic vibration on the macro and microstructure of A356 alloy in order to develop a new process of structural control in A356 alloy. When the electromagnetic vibration is conducted for changing the shape of primary aluminum, at low frequency (≤60Hz), the shape of dendrite is changed speroidal shape. When the electromagnetic vibration is conducted for changing the shape of eutectic silicon, a morphological change of the eutectic silicon from coarse platelet flakes to fine fiber shape is observed with EMV (Electro Magnetic Vibration) process at high frequency (≥500Hz).

scholarly journals CLUSTER–STAFF search coil magnetometer calibration – comparisons with FGM

2014 ◽  
Vol 3 (2) ◽  
pp. 153-177 ◽  
Author(s):  
P. Robert ◽  
N. Cornilleau-Wehrlin ◽  
R. Piberne ◽  
Y. de Conchy ◽  
C. Lacombe ◽  
...  
Keyword(s):  
Transfer Functions ◽  
Low Frequency ◽  
Temporal Analysis ◽  
Fluxgate Magnetometer ◽  
Data Sets ◽  
Spectral Matrix ◽  
Spatio Temporal ◽  
Cross Calibration ◽  
The Waves ◽  
The Way

Abstract. The main part of the Cluster Spatio-Temporal Analysis of Field Fluctuations (STAFF) experiment consists of triaxial search coils allowing the measurements of the three magnetic components of the waves from 0.1 Hz up to 4 kHz. Two sets of data are produced, one by a module to filter and transmit the corresponding waveform up to either 10 or 180 Hz (STAFF-SC), and the second by the onboard Spectrum Analyser (STAFF-SA) to compute the elements of the spectral matrix for five components of the waves, 3 × B and 2 × E (from the EFW experiment), in the frequency range 8 Hz to 4 kHz. In order to understand the way the output signals of the search coils are calibrated, the transfer functions of the different parts of the instrument are described as well as the way to transform telemetry data into physical units across various coordinate systems from the spinning sensors to a fixed and known frame. The instrument sensitivity is discussed. Cross-calibration inside STAFF (SC and SA) is presented. Results of cross-calibration between the STAFF search coils and the Cluster Fluxgate Magnetometer (FGM) data are discussed. It is shown that these cross-calibrations lead to an agreement between both data sets at low frequency within a 2% error. By means of statistics done over 10 yr, it is shown that the functionalities and characteristics of both instruments have not changed during this period.

Searches for low-frequency bursts of gravitational radiation

1985 ◽  
Vol 28 (10) ◽  
pp. 938-939 ◽  
Author(s):  
Vladimir B Braginskiĭ ◽  
A V Gusev ◽  
V P Mitrofanov ◽  
V N Rudenko ◽  
V N Yakimov
Keyword(s):  
Gravitational Radiation ◽  
Low Frequency

Toward High-Resolution Mechanical Spectroscopy HRMS - Logarithmic Decrement

2012 ◽  
Vol 184 ◽  
pp. 467-472 ◽  
Author(s):  
Leszek B. Magalas ◽  
M. Majewski
Keyword(s):  
High Resolution ◽  
Low Frequency ◽  
Logarithmic Decrement ◽  
Frequency Resolution ◽  
Mechanical Spectroscopy ◽  
Spectral Leakage ◽  
Experimental Noise ◽  
Relative Errors ◽  
The Way

In this work, we present the comparison between different methods used to compute the logarithmic decrement,δ. The parametric OMI method and interpolated DFT (IpDFT) methods are used to compute theδfrom free decaying oscillations embedded in an experimental noise typical for low-frequency mechanical spectrometers. The results are reported forδ= 5×10-4, = 1.12345 Hz and different sampling frequencies, = 1 kHz and 4 kHz. A new YM algorithm yields the smallest dispersion in experimental points of the logarithmic decrement and the smallest relative errors among all investigated IpDFT methods. In general, however, the IpDFT methods suffer from spectral leakage and frequency resolution. Therefore it is demonstrated that the performance of different methods to compute theδcan be listed in the following order: (1) OMI, (2) YM, (3) YMC, and (4) the Yoshida method, Y. For short free decays the order of the best performers is different: (1) OMI and (2) YMC. It is important to emphasize that IpDFT methods (including the Yoshida method, Y) are discouraged for signals that are too short. In conclusion, the best methods to compute the logarithmic decrement are the OMI and the YM. These methods will pave the way toward high-resolution mechanical spectroscopy HRMS.

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