scholarly journals Quasi-Static and Steady-State Pictures for Collapsing Core of Type II Supernova

1988 ◽  
Vol 108 ◽  
pp. 420-421
Author(s):  
D. Sugimoto ◽  
A. Sasaki ◽  
T. Ebisuzaki
Keyword(s):  
Shock Wave ◽  
Steady State ◽  
Bound State ◽  
Negative Energy ◽  
Gravitational Energy ◽  
The Other ◽  
Positive Energy ◽  
Core Collapse ◽  
Type Ii ◽  
The Core

Explosion of type II supernova is, in principle, a difficult process: The presupernova star was in gravitationally bound state with negative energy but it has to be divided into two parts, the collapsed core of still lower (negative) energy and the ejected envelope of positive energy. This process is against nature in the sense most of the phenomena in nature proceed towards equipartition of energies. Thus, some finely tuned mechanism should be necessary for successful explosion. Two different mechanisms have been proposed; one is the prompt explosion where the gravitational energy release by the core collapse is transferred to the mantle by a shock wave, and the other is delayed explosion where it is transferred slowly by neutrinos diffusing out of the core. In what follows we shall concentrate in the case of the delayed explosion.

scholarly journals Bargmann–Wigner formulation and superradiance problem of bosons and fermions in Kerr space–time

2015 ◽  
Vol 30 (11) ◽  
pp. 1550052 ◽  
Author(s):  
Masakatsu Kenmoku ◽  
Y. M. Cho
Keyword(s):  
Negative Energy ◽  
Space Time ◽  
The Other ◽  
Positive Energy ◽  
Independent Components ◽  
Consistent Description ◽  
Other Hand ◽  
Kerr Space

The superradiance phenomena of massive bosons and fermions in the Kerr space–time are studied in the Bargmann–Wigner formulation. In case of bi-spinor, the four independent components spinors correspond to the four bosonic freedom: one scalar and three vectors uniquely. The consistent description of the Bargmann–Wigner equations between fermions and bosons shows that the superradiance of the type with positive energy (0 < ω) and negative momentum near horizon (p H < 0) is shown not to occur. On the other hand, the superradiance of the type with negative energy (ω < 0) and positive momentum near horizon (0 < p H ) is still possible for both scalar bosons and spinor fermions.

scholarly journals The origin of the two populations of blue stragglers in M30

2019 ◽  
Vol 621 ◽  
pp. L10 ◽  
Author(s):  
S. Portegies Zwart
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
The Other ◽  
Core Collapse ◽  
Blue Stragglers ◽  
The Core ◽  
Constant Rate ◽  
Blue Straggler ◽  
Binary Evolution ◽  
Two Populations

We analyze the position of the two populations of blue stragglers in the globular cluster M30 in the Hertzsprung–Russell diagram. Both populations of blue stragglers are brighter than the cluster’s turn-off, but one population, the blue blue-stragglers, aligns along the zero-age main sequence whereas the other, red population is elevated in brightness (or color) by ∼0.75 mag. Based on stellar evolution and merger simulations we argue that the red population, which composes about 40% of the blue stragglers in M 30, has formed at a constant rate of ∼2.8 blue stragglers per gigayear over the last ∼10 Gyr. The blue population on the other hand formed in a burst that started ∼3.2 Gyr ago at a peak rate of 30 blue stragglers per gigayear with an e-folding time scale of 0.93 Gyr. We speculate that the burst resulted from the core collapse of the cluster at an age of about 9.8 Gyr, whereas the constantly formed population is the result of mass transfer and mergers through binary evolution. In this scenario, about half the binaries in the cluster effectively result in a blue straggler.

Some aspects of energy metabolism of the sow during pregnancy

1971 ◽  
Vol 13 (4) ◽  
pp. 677-683 ◽  
Author(s):  
M. W. A. Verstegen ◽  
A. J. H. van Es ◽  
H. J. Nijkamp
Keyword(s):  
Energy Requirement ◽  
Live Weight ◽  
Negative Energy ◽  
The Other ◽  
Positive Energy ◽  
Dietary Energy ◽  
Respiration Chamber ◽  
Dietary Energy Intake ◽  
Energy Balances ◽  
Balance Trials

SUMMARYSixteen energy and N-balance trials with six sows were performed to study the energy requirement and protein gain of the animals during different stages in the second half of pregnancy. Energy and N-balances were measured during periods of 1 week and gaseous exchange was measured in a respiration chamber. The animals received 2·0,2·5,2·75 or 3 0 kg/day of a normal concentrate ration for sows. In one experiment, one animal had a negative energy balance on the 2 kg ration in the sixth week of pregnancy but in the other experiments the dietary energy intake was sufficient for positive energy balances until a few days before parturition. The N-balances were about 20 to 32 g/day in the second half of the gestation period. With 2·5 and 2·75 kg feed there was a negative deposition of fat at about 2 weeks before parturition. Heat production increased during pregnancy, but at a greater rate during the last 2 weeks. Until 2 to 3 weeks before parturition 2·5 to 2·75 kg of feed seemed to be adequate to meet the energy requirement of a pregnant sow of 180–200 kg live weight. During the last 2 weeks 3 kg was sufficient.

scholarly journals Effects of Hardness of Primordial Binaries on Evolution of Star Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 251-255
Author(s):  
A. Tanikawa ◽  
T. Fukushige
Keyword(s):  
Star Clusters ◽  
Equal Mass ◽  
Binding Energies ◽  
The Other ◽  
Special Treatment ◽  
Integration Scheme ◽  
Core Collapse ◽  
The Core ◽  
Double Mass

AbstractWe performed N-body simulations of star clusters with primordial binaries using a new code, GORILLA. It is based on Makino and Aarseth (1992)'s integration scheme on GRAPE, and includes a special treatment for relatively isolated binaries. Using the new code, we investigated effects of hardness of primordial binaries on whole evolution of the clusters. We simulated seven N=16384 equal-mass clusters containing 10% (in mass) primordial binaries whose binding energies are 1, 3, 10, 30, 100, 300, and 1000kT, respectively. Additionally, we also simulated a cluster without primordial binaries and that in which all binaries are replaced by stars with double mass, as references of soft and hard limits, respectively. We found that, in both soft (≤ 3kT) and hard (≥ 1000kT) limits, clusters experiences deep core collapse and shows gravothermal oscillations. On the other hands, in the intermediate hardness (10-300kT), the core collapses halt halfway due an energy releases of the primordial binaries.

scholarly journals Relativistic Brueckner-Hartree-Fock Theory in Infinite Nuclear Matter

2021 ◽  
Vol 252 ◽  
pp. 02001
Author(s):  
Peter Ring ◽  
Sibo Wang ◽  
Qiang Zhao ◽  
Jie Meng
Keyword(s):  
Nuclear Matter ◽  
Complete Solution ◽  
Negative Energy ◽  
The Other ◽  
Positive Energy ◽  
Density Functionals ◽  
Matrix Elements ◽  
Hartree Fock ◽  
Microscopic Derivation ◽  
Covariant Density

On the way of a microscopic derivation of covariant density functionals, the first complete solution of the relativistic Brueckner-Hartree-Fock (RBHF) equations is presented for symmetric nuclear matter. In most of the earlier investigations, the G-matrix is calculated only in the space of positive energy solutions. On the other side, for the solution of the relativistic Hartree-Fock (RHF) equations, also the elements of this matrix connecting positive and negative energy solutions are required. So far, in the literature, these matrix elements are derived in various approximations. We discuss solutions of the Thompson equation for the full Dirac space and compare the resulting equation of state with those of earlier attempts in this direction.

scholarly journals Quark-Hadron Hybrid Stars as Remnants of Supernovae Explosions

1999 ◽  
Vol 194 ◽  
pp. 327-329
Author(s):  
Gevorg S. Poghosyan
Keyword(s):  
Shock Wave ◽  
Phase Transitions ◽  
Time Scale ◽  
Free Fall ◽  
Central Density ◽  
Core Collapse ◽  
Hybrid Star ◽  
The Core ◽  
Hadron Phase ◽  
Hybrid Stars

It is expected that at explosion of Supernovae the mechanism of producing a shock wave is based on subatomic interactions, and the remnant of the supernovae explosion can be a hybrid quark-hadron star. Since the temperature in the centre of collapsing stars reaches of order T = 6 − 8 · 1010K and density electrons from the top of the Fermi sea can be captured and convert protons into neutrons via e− + p → n + ve. The capture of electrons results in a neutronization burst (V.S. Imshennik 1988). Core collapse of the progenitor star becomes essentially a free fall with a time scale . When the central density of the core reaches supernuclear densities the repulsive QCD forces becomes essential. This can bring about manifestations of quark-hadron phase transitions (A. Dar 1997). After the explosion, from the remaining matter is probably formed a hybrid star.

ATTENUATION OF NON-PHYSICAL OSCILLATIONS IN SUPERNOVA SHOCK WAVES

2007 ◽  
Vol 16 (02n03) ◽  
pp. 515-520
Author(s):  
S. B. DUARTE ◽  
H. RODRIGUES ◽  
D. PORTES
Keyword(s):  
Shock Wave ◽  
Shock Front ◽  
Current Problem ◽  
Artificial Viscosity ◽  
Numerical Code ◽  
Plane Shock ◽  
Core Collapse ◽  
Type Ii ◽  
Von Neumann ◽  
A Current

Artificial viscosity is widely used in numerical calculations of stellar core collapse. The failure or success of the prompt mechanism explosion of type-II supernovae is strongly dependent on the numerical code, and the study of a suitable and efficient method of capturing the shock front is a current problem. We present a novel one-term artificial viscosity which is dependent on the velocity field along the shock front. We show that this form of artificial viscosity is able to capture the profile of a plane shock wave, removing the non-physical oscillations originated by the artificial viscosity of von Neumann and Richtmyer type.

The Bakerian Lecture, 1993 - Mechanism of supernovae

1994 ◽  
Vol 346 (1680) ◽  
pp. 251-258 ◽  
Keyword(s):  
Massive Stars ◽  
Neutrino Energy ◽  
Gravitational Energy ◽  
Central Core ◽  
The Sun ◽  
Type Ii ◽  
The Core

Supernovae of type II happen at the end of the evolution of massive stars, 10 times the mass of the Sun, M ⨀, or more. To begin with, the central core, of mass about 1.5M ⨀, collapses; the large gravitational energy remains for a while in the core. It is then released in the form of neutrinos. A small fraction, 1 or 2% , of the neutrino energy is absorbed in the mantle of the star, i.e. the region 100 or 500 km from the centre; this drives the shock. It is essential that vigorous convection occurs in the shocked material. With reasonable assumptions, one can estimate the energy in the shock to be of the order 10 51 erg, in agreement with observation. The argument is based on observation and analytical calculations, with a minimum of help from elaborate computations.

scholarly journals Polymer quantization, stability and higher-order time derivative terms

2016 ◽  
Vol 31 (09) ◽  
pp. 1650040 ◽  
Author(s):  
Patricio Cumsille ◽  
Carlos M. Reyes ◽  
Sebastian Ossandon ◽  
Camilo Reyes
Keyword(s):  
Field Theory ◽  
Stability Problem ◽  
Time Derivative ◽  
Negative Energy ◽  
Higher Order ◽  
The Other ◽  
Harmonic Oscillators ◽  
Positive Energy ◽  
Quantum Field ◽  
The Stability

The possibility that fundamental discreteness implicit in a quantum gravity theory may act as a natural regulator for ultraviolet singularities arising in quantum field theory has been intensively studied. Here, along the same expectations, we investigate whether a nonstandard representation called polymer representation can smooth away the large amount of negative energy that afflicts the Hamiltonians of higher-order time derivative theories, rendering the theory unstable when interactions come into play. We focus on the fourth-order Pais–Uhlenbeck model which can be reexpressed as the sum of two decoupled harmonic oscillators one producing positive energy and the other negative energy. As expected, the Schrödinger quantization of such model leads to the stability problem or to negative norm states called ghosts. Within the framework of polymer quantization we show the existence of new regions where the Hamiltonian can be defined well bounded from below.

scholarly journals Supernova 1987A: Light Curves and their Intepretation

1989 ◽  
Vol 8 ◽  
pp. 185-192 ◽  
Author(s):  
R M Catchpole
Keyword(s):  
Shock Wave ◽  
New Zealand ◽  
Detailed Comparison ◽  
Light Curves ◽  
Stellar Surface ◽  
Core Collapse ◽  
Type Ii ◽  
Supernova 1987A ◽  
Photometric Observations ◽  
Objective Prism

The Type II supernova SN1987A which occurred in the LMC is the brightest and most completely observed supernova ever recorded. Objective prism and UBV observations were made of the blue supergiant progenitor Sanduleak −69°202 and indicate that the visual absorption lies in the range 0.4<AV<0.6. Furthermore, the distance to the LMC is known in absolute units with a precision of about ± 15% (m-M = 18.45, Feast 1988) which combined with the above data and subseguent photometric observations permits detailed comparison with theory.Within 107 minutes of the Kamiokande 1MB neutrino event the region of the supernova was being observed by Albert Jones, although it was not until 0.8 days after the event that the supernova was officially discovered by Shelton. The first photoelectric observation was made at 1.1 days, by William Allen (1988) a New Zealand amateur. Other observations made during the first two days, have been conveniently tabulated by Arnett (1988). During this time the supernova steadily brightened in V, although theory predicts that it was rapidly fading bolometrically and cooling, after the intense heating that occurred when the shock wave reached the stellar surface about 3 hours after core collapse.

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