scholarly journals Hybrid post-Newtonian effective-one-body scheme for spin-precessing compact-binary waveforms up to merger

2021 ◽  
Vol 103 (2) ◽  
Author(s):  
Sarp Akcay ◽  
Rossella Gamba ◽  
Sebastiano Bernuzzi
Keyword(s):  
Body Scheme ◽  
Compact Binary

Physical Activity Level and Motor Aptitude: Motor Domains and Identification Capacity of Brazilian Insufficiently Active Older Adults

2020 ◽  
Vol 13 ◽  
Author(s):  
Lucia Maria Andreis ◽  
Fernando de Aguiar Lemos ◽  
Lorenna Walesca de Lima Silva ◽  
Cassiana Luiza Pistorello Garcia ◽  
Gabrielli Veras ◽  
...  
Keyword(s):  
Physical Activity ◽  
Older Adults ◽  
Physical Activity Level ◽  
Area Under The Curve ◽  
The Elderly ◽  
Activity Level ◽  
General Motor ◽  
Body Scheme ◽  
Significant Difference ◽  
Global Coordination

Background: A decrease in the physical activity level in old age is common, which results in an increase in the number of falls and chronic conditions. Associated with that occurs the decline in motor skills as a result of the deficit in the interaction of cognitive and motor processes. Physical activity level can be associated differently with each motor domains. Objective: We analyzed the relationship between physical activity level and motor aptitude, and to identify which motor domains were most sensitive to detect insufficiently active level in older adults. Methods: Participated in the study 385 elderly people of both sexes. For the evaluation of the subjects were adopted the International Questionnaire on Physical Activity and the Motor Scale for Older Adults. Results: The majority of the elderly were active. In the comparison of motor aptitude between active and insufficiently active (IAC) elders a significant difference was found in the Global Coordination, Balance, Body Scheme and General Motor Aptitude. From the analysis of the area under the curve (AUC), we verified that these domains also were the ones that presented adequate diagnostic accuracy to identify IAC elderly. Besides that active elderly have presented the General Motor Aptitude classified within normality while the IAC below the normal. Conclusion: Our data suggest that IAC older adults present lower motor aptitude than the active elderly, especially in the domains of Global Coordination, Balance, Body Scheme and General Motor Aptitude, and that these domains were sensitive to indicate IAC older adults.

Explicit symplectic-like integration with corrected map for inseparable Hamiltonian

2020 ◽  
Vol 501 (1) ◽  
pp. 1511-1519
Author(s):  
Junjie Luo ◽  
Weipeng Lin ◽  
Lili Yang
Keyword(s):  
Phase Space ◽  
Space Structure ◽  
Eighth Order ◽  
Time Step ◽  
Extended Phase ◽  
Energy Error ◽  
Phase Space Structure ◽  
Compact Binary ◽  
Three Body

ABSTRACT Symplectic algorithms are widely used for long-term integration of astrophysical problems. However, this technique can only be easily constructed for separable Hamiltonian, as preserving the phase-space structure. Recently, for inseparable Hamiltonian, the fourth-order extended phase-space explicit symplectic-like methods have been developed by using the Yoshida’s triple product with a mid-point map, where the algorithm is more effective, stable and also more accurate, compared with the sequent permutations of momenta and position coordinates, especially for some chaotic case. However, it has been found that, for the cases such as with chaotic orbits of spinning compact binary or circular restricted three-body system, it may cause secular drift in energy error and even more the computation break down. To solve this problem, we have made further improvement on the mid-point map with a momentum-scaling correction, which turns out to behave more stably in long-term evolution and have smaller energy error than previous methods. In particular, it could obtain a comparable phase-space distance as computing from the eighth-order Runge–Kutta method with the same time-step.

scholarly journals Spectral index-flux relation for investigating the origins of steep decay in γ-ray bursts

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Samuele Ronchini ◽  
Gor Oganesyan ◽  
Marica Branchesi ◽  
Stefano Ascenzi ◽  
Maria Grazia Bernardini ◽  
...  
Keyword(s):  
Spectral Index ◽  
Proton Synchrotron ◽  
Relativistic Jets ◽  
Time Resolved ◽  
X Ray ◽  
Compact Binary ◽  
Internal Dissipation ◽  
Adiabatic Cooling ◽  
Alternative Scenarios ◽  
Steep Decay

Abstractγ-ray bursts (GRBs) are short-lived transients releasing a large amount of energy (1051 − 1053 erg) in the keV-MeV energy range. GRBs are thought to originate from internal dissipation of the energy carried by ultra-relativistic jets launched by the remnant of a massive star’s death or a compact binary coalescence. While thousands of GRBs have been observed over the last thirty years, we still have an incomplete understanding of where and how the radiation is generated in the jet. Here we show a relation between the spectral index and the flux found by investigating the X-ray tails of bright GRB pulses via time-resolved spectral analysis. This relation is incompatible with the long standing scenario which invokes the delayed arrival of photons from high-latitude parts of the jet. While the alternative scenarios cannot be firmly excluded, the adiabatic cooling of the emitting particles is the most plausible explanation for the discovered relation, suggesting a proton-synchrotron origin of the GRB emission.

scholarly journals The dynamic ejecta of compact object mergers and eccentric collisions

2013 ◽  
Vol 371 (1992) ◽  
pp. 20120272 ◽  
Author(s):  
Stephan Rosswog
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Compact Object ◽  
Solar Mass ◽  
Abundance Pattern ◽  
Compact Binary ◽  
Hydrodynamical Simulations ◽  
Rich Material ◽  
R Process

Compact object mergers eject neutron-rich matter in a number of ways: by the dynamical ejection mediated by gravitational torques, as neutrino-driven winds, and probably also a good fraction of the resulting accretion disc finally becomes unbound by a combination of viscous and nuclear processes. If compact binary mergers indeed produce gamma-ray bursts, there should also be an interaction region where an ultra-relativistic outflow interacts with the neutrino-driven wind and produces moderately relativistic ejecta. Each type of ejecta has different physical properties, and therefore plays a different role for nucleosynthesis and for the electromagnetic (EM) transients that go along with compact object encounters. Here, we focus on the dynamic ejecta and present results for over 30 hydrodynamical simulations of both gravitational wave-driven mergers and parabolic encounters as they may occur in globular clusters. We find that mergers eject approximately 1 per cent of a Solar mass of extremely neutron-rich material. The exact amount, as well as the ejection velocity, depends on the involved masses with asymmetric systems ejecting more material at higher velocities. This material undergoes a robust r-process and both ejecta amount and abundance pattern are consistent with neutron star mergers being a major source of the ‘heavy’ ( A >130) r-process isotopes. Parabolic collisions, especially those between neutron stars and black holes, eject substantially larger amounts of mass, and therefore cannot occur frequently without overproducing gala- ctic r-process matter. We also discuss the EM transients that are powered by radioactive decays within the ejecta (‘macronovae’), and the radio flares that emerge when the ejecta dissipate their large kinetic energies in the ambient medium.

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