Nuclear Theory·nucl-th

Thursday·October 6, 2016

10 papers—5 primary·5 cross-listed

06
[Submitted on 5 Oct 2016] (cross-list from hep-lat)
Time evolution of linearized gauge field fluctuations on a real-time lattice
Aleksi Kurkela🇨🇭 · Tuomas Lappi🇫🇮 · Jarkko Peuron🇫🇮
Classical real-time lattice simulations play an important role in understanding non-equilibrium phenomena in gauge theories and are used in particular to model the prethermal evolution of heavy-ion collisions. Due to instabilities, small quantum fluctuations on top of the classical background may significantly affect the dynamics of the system. In this paper we argue for the need for a numerical calculation of a system of classical gauge fields and small linearized fluctuations in a way that keeps the separation between the two manifest. We derive and test an explicit algorithm to solve these equations on the lattice, maintaining gauge invariance and Gauss's law.
Comments:
8 pages, 4 figures, v2: typos corrected, references added
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1610.01355 [pdf]
EPJC(2016)·24 citations
07
[Submitted on 5 Oct 2016] (cross-list from physics.ins-det)
FMEA Based Risk Assessment of Component Failure Modes in Industrial Radiography
Alok Pandey · Meghraj Singh · A. U. Sonawane · Prashant S. Rawat
Industrial radiography has its inimitable role in non-destructive examinations. Industrial radiography devices, consisting of significantly high activity of the radioisotopes, are operated manually by remotely held control unit. Malfunctioning of these devices may cause potential exposure to the operator and nearby public, and thus should be practiced under a systematic risk control. To ensure the radiation safety, proactive risk assessment should be implemented. Risk assessment in industrial radiography using the Failure Modes & Effect Analysis (FMEA) for the design and operation of industrial radiography exposure devices has been carried out in this study. Total 56 component failure modes were identified and Risk Priority Numbers (RPNs) were assigned by the FMEA expert team, based on the field experience and reported failure data of various components. Results shows all the identified failure modes have RPN in the range of 04 to 216 and most of the higher RPN are due to low detectability and high severity levels. Assessment reveals that increasing failure detectability is a practical and feasible approach to reduce the risk in most of the failure modes of industrial radiography devices. Actions for reducing RPN for each failure mode have been suggested. Feasibility of FMEA for risk assessment in industrial radiography has been established by this study
Subjects:
Instrumentation and Detectors (physics.ins-det); Nuclear Theory (nucl-th); physics.med-ph (physics.med-ph)
arXiv:
1610.01364 [pdf]
0 citations
08
[Submitted on 5 Oct 2016] (cross-list from hep-lat)
Pion-nucleon scattering in the Roper channel from lattice QCD
C. B. Lang🇦🇹 · L. Leskovec🇺🇸 · M. Padmanath🇩🇪 · S. Prelovsek🇺🇸
We present a lattice QCD study of $N π$ scattering in the positive-parity nucleon channel, where the puzzling Roper resonance $N^{*} (1440)$ resides in experiment. The study is based on the PACS-CS ensemble of gauge configurations with $N_{f} = 2 + 1$ Wilson-clover dynamical fermions, $m_{π} ≃ 156$ MeV and $L ≃ 2.9$ fm. In addition to a number of $q q q$ interpolating fields, we implement operators for $N π$ in $p$ -wave and $N σ$ in $s$ -wave. In the center-of-momentum frame we find three eigenstates below 1.65 GeV. They are dominated by $N (0)$ , $N (0) π (0) π (0)$ (mixed with $N (0) σ (0)$ ) and $N (p) π (- p)$ with $p ≃ 2 π / L$ , where momenta are given in parentheses. This is the first simulation where the expected multi-hadron states are found in this channel. The experimental $N π$ phase-shift would -- in the approximation of purely elastic $N π$ scattering -- imply an additional eigenstate near the Roper mass $m_{R} ≃ 1.43$ GeV for our lattice size. We do not observe any such additional eigenstate, which indicates that $N π$ elastic scattering alone does not render a low-lying Roper. Coupling with other channels, most notably with $N π π$ , seems to be important for generating the Roper resonance, reinforcing the notion that this state could be a dynamically generated resonance. Our results are in line with most of previous lattice studies based just on $q q q$ interpolators, that did not find a Roper eigenstate below $1.65$ GeV. The study of the coupled-channel scattering including a three-particle decay $N π π$ remains a challenge.
Comments:
14 pages, 9 figures, version published in Phys. Rev. D plus additional footnote and reference
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1610.01422 [pdf]
PRD(2017)·128 citations
09
[Submitted on 5 Oct 2016] (cross-list from hep-th)
Critical behavior of non-hydrodynamic quasinormal modes in a strongly coupled plasma
Stefano I. Finazzo (Sao Paulo, IFT)🇧🇷 · Romulo Rougemont (Sao Paulo U.)🇧🇷 · Maicon Zaniboni (Sao Paulo U.)🇧🇷 · Renato Critelli (Sao Paulo U.)🇧🇷 · Jorge Noronha (Sao Paulo U.)🇧🇷
We study the behavior of quasinormal modes in a top-down holographic dual corresponding to a strongly coupled $N = 4$ super Yang-Mills plasma charged under a $U (1)$ subgroup of the global $S U (4)$ R-symmetry. In particular, we analyze the spectra of quasinormal modes in the external scalar and vector diffusion channels near the critical point and obtain the behavior of the characteristic equilibration times of the plasma as the system evolves towards the critical point of its phase diagram. Except close to the critical point, we observe that by increasing the chemical potential one generally increases the damping rate of the quasinormal modes, which leads to a reduction of the characteristic equilibration times in the dual strongly coupled plasma. However, as one approaches the critical point the typical equilibration time (as estimated from the lowest non-hydrodynamic quasinormal mode frequency) increases, although remaining finite, while its derivative with respect to the chemical potential diverges with exponent -1/2. We also find a purely imaginary non-hydrodynamical mode in the vector diffusion channel at nonzero chemical potential which dictates the equilibration time in this channel near the critical point.
Comments:
31 pages, 15 figures, version accepted for publication in JHEP
Subjects:
High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1610.01519 [pdf]
JHEP(2017)·46 citations
10
[Submitted on 5 Oct 2016] (cross-list from nucl-ex)
Unexpected distribution of $ν 1 f_{7/2}$ strength in the calcium isotopes at $N$ =30
H. L. Crawford🇺🇸 · A. O. Macchiavelli🇺🇸 · P. Fallon🇺🇸 · M. Albers🇺🇸 · V. M. Bader🇺🇸 · D. Bazin🇺🇸 · C. M. Campbell🇺🇸 · R. M. Clark🇺🇸 · M. Cromaz🇺🇸 · J. Dilling🇨🇦 · A. Gade🇺🇸 · A. T. Gallant🇨🇦 and 21 other authors
The calcium isotopes have emerged as an important testing ground for new microscopically derived shell-model interactions, and a great deal of focus has been directed toward this region. We investigate the relative spectroscopic strengths associated with $1 f_{7/2}$ neutron hole states in $^{47, 49}$ Ca following one-neutron knockout reactions from $^{48, 50}$ Ca. The observed reduction of strength populating the lowest 7/2 $_{1}^{-}$ state in $^{49}$ Ca, as compared to $^{47}$ Ca, is consistent with the description given by shell-model calculations based on two- and three-nucleon forces in the neutron $p f$ model space, implying a fragmentation of the $l$ =3 strength to higher-lying states. The experimental result is inconsistent with both the GXPF1 interaction routinely used in this region of the nuclear chart and with microscopic calculations in an extended model space including the $ν 1 g_{9/2}$ orbital.
Comments:
6 pages, 2 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1610.01575 [pdf]
PRC(2017)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE

Time evolution of linearized gauge field fluctuations on a real-time lattice

FMEA Based Risk Assessment of Component Failure Modes in Industrial Radiography

Pion-nucleon scattering in the Roper channel from lattice QCD

Critical behavior of non-hydrodynamic quasinormal modes in a strongly coupled plasma

Unexpected distribution of ν1f7/2​ strength in the calcium isotopes at N=30

Affiliations

Unexpected distribution of $ν 1 f_{7/2}$ strength in the calcium isotopes at $N$ =30