scholarly journals NEUTRINO ENERGIES IN A NEUTRINOSPHERE

2013 ◽  
Vol 28 (34) ◽  
pp. 1350153 ◽  
Author(s):  
LEONARD S. KISSLINGER
Keyword(s):  
Effective Mass ◽  
Gravitational Collapse ◽  
Massive Star ◽  
Dense Matter ◽  
Energy Eigenvalues ◽  
Effective Masses

The energies of neutrinos in a neutrinosphere, the dense matter created after the gravitational collapse of a massive star are estimated. Cubic equations for energy eigenvalues of neutrinos are used with the effective masses found by taking the neutrinos at rest in neutrinosphere matter. Large differences in the effective mass of some neutrino species in a neutrinosphere compared to vacuum are found.

Effective masses in a dense fermion background — Applied to neutrinos, dark matter and dark energy

2014 ◽  
Vol 29 (21) ◽  
pp. 1444010
Author(s):  
Bruce H. J. McKellar ◽  
T. J. Goldman ◽  
G. J. Stephenson
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Effective Mass ◽  
Negative Pressure ◽  
Expectation Value ◽  
Effective Masses ◽  
Neutrino Astrophysics

If fermions interact with a scalar field, and there are many fermions present the scalar field may develop an expectation value and generate an effective mass for the fermions. This can lead to the formation of fermion clusters, which could be relevant for neutrino astrophysics and for dark matter astrophysics. Because this system may exhibit negative pressure, it also leads to a model of dark energy.

Direct evaluation of hole effective mass of SnS–SnSe solid solutions with ARPES measurement

2021 ◽  
Author(s):  
Issei Suzuki ◽  
Zexin Lin ◽  
Sakiko Kawanishi ◽  
Kiyohisa Tanaka ◽  
Yoshitaro Nose ◽  
...  
Keyword(s):  
Effective Mass ◽  
Valence Band ◽  
Thermoelectric Properties ◽  
Solid Solutions ◽  
Photoemission Spectroscopy ◽  
Direct Evaluation ◽  
Hole Effective Mass ◽  
Single Crystalline ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Effective Masses

Valence band dispersions of single-crystalline SnS1-xSex solid solutions were observed by angle-resolved photoemission spectroscopy (ARPES). The hole effective masses, crucial factors in determining thermoelectric properties, were directly evaluated. They decrease...

scholarly journals GRAVITATIONAL COLLAPSE AND WEAK INTERACTIONS

1966 ◽  
Vol 44 (11) ◽  
pp. 2553-2594 ◽  
Author(s):  
W. David Arnett
Keyword(s):  
General Relativity ◽  
Energy Transfer ◽  
Equation Of State ◽  
Gravitational Collapse ◽  
Massive Star ◽  
Weak Interactions ◽  
Approximation Procedure ◽  
The Core ◽  
Numerical Hydrodynamics ◽  
Subsequent Behavior

The behavior of a massive star during its final catastrophic stages of evolution has been investigated theoretically, with particular emphasis upon the effect of electron-type neutrino interactions. The methods of numerical hydrodynamics, with coupled energy transfer in the diffusion approximation, were used. In this respect, this investigation differs from the work of Colgate and White (1964) in which a "neutrino deposition" approximation procedure was used. Gravitational collapse initiated by electron capture and by thermal disintegration of nuclei in the stellar center is examined, and the subsequent behavior does not depend sensitively upon which process causes the collapse.As the density and temperature of the collapsing stellar core increase, the material becomes opaque to electron-type neutrinos and energy is transferred by these neutrinos to regions of the star less tightly bound by gravity. Ejection of the outer layers of the star can result. This phenomenon has been identified with supernovae.Uncertainty concerning the equation of state of a hot, dense nucleon gas causes uncertainty in the temperature of the collapsing matter. This affects the rate of energy transfer by electron-type neutrinos and the rate of energy lost to the star by muon-type neutrinos.The effects of general relativity do not appear to become important in the core until after the ejection of the outer layers.

GRAVITATIONAL COLLAPSE OF MASSIVE STARS AS A PROBE INTO HOT DENSE MATTER

2008 ◽  
Vol 23 (27n30) ◽  
pp. 2443-2450 ◽  
Author(s):  
SHOICHI YAMADA
Keyword(s):  
Equation Of State ◽  
Gravitational Collapse ◽  
Nuclear Physics ◽  
Massive Stars ◽  
Dense Matter ◽  
High Energy ◽  
Compact Objects ◽  
Core Collapse ◽  
Accretion Shock ◽  
Very High

Nuclear physics is an indispensable input for the investigation of high energy astrophysical phenomena involving compact objects. In this paper I take a gravitational collapse of massive stars as an example and show how the macroscopic dynamics is influenced by the properties of nuclei and nuclear matter. I will discuss two topics that are rather independent of each other. The first one is the interplay of neutrino-nuclei inelastic scatterings and the standing accretion shock instability in the core of core collapse supernovae and the second is concerning the neutrino emissions from black hole formations and their dependence on the equation of state at very high densities. In the latter, I will also demonstrate that future astronomical observations might provide us with valuable information on the equation of state of hot dense matter.

EQUATION OF STATE OF DENSE MATTER FOR CORE-COLLAPSE SUPERNOVAE AND NEUTRINO BURSTS

2008 ◽  
Vol 23 (27n30) ◽  
pp. 2451-2454
Author(s):  
KOHSUKE SUMIYOSHI
Keyword(s):  
Black Hole ◽  
Equation Of State ◽  
Numerical Simulations ◽  
Gravitational Collapse ◽  
Massive Stars ◽  
Dense Matter ◽  
Core Collapse ◽  
Many Body ◽  
Recent Developments ◽  
Supernova Explosions

We report the recent developments on the tables of equation of state for dense matter and their influence on core-collapse supernovae and associated neutrino emissions. We study the gravitational collapse of massive stars by the numerical simulations with the tables of equation of state recently developed in relativistic many body frameworks. I discuss whether the equation of state of dense matter can be probed by the properties of neutrino signals from black hole forming supernovae, being different from ordinary neutrino bursts from supernova explosions.

Electronic Structure of Si/InAs Composite Channels

2007 ◽  
Vol 995 ◽  
Author(s):  
Marta Prada ◽  
Neerav Kharche ◽  
Gerhard Klimeck
Keyword(s):  
Electronic Structure ◽  
Quantum Well ◽  
Effective Mass ◽  
Tight Binding ◽  
Localized States ◽  
Equivalent Thickness ◽  
Binding Model ◽  
Direct Bandgap ◽  
Effective Masses ◽  
Composite Channels

AbstractElectronic structure calculations on composite channels, consisting of indium arsenide grown on the technologically relevant (001), (011) and (112)-orientated silicon surfaces are reported. The calculations are performed with NEMO 3-D, where atoms are represented explicitly in the sp3d5s* tight-binding model. The Valence Force Field (VFF) method is employed to minimize the strain. NEMO 3-D enables the calculation of localized states in the quantum well (QW) and their dispersion in the quantum well plane. From this dispersion, the bandgap, its direct or indirect in character, and the associated effective masses of the valence and conduction band can be determined. Such composite bandstructure calculations are demonstrated here for the first time. The numerical results presented here can then be included in empirical device models to estimate device performance. Pure InAs QWs create a direct bandgap material, with a relatively small gap and effective masses of about one order of magnitude smaller than for pure Si QW of equivalent thickness. Si, on the other hand, has a larger bandgap, superior thermal and mechanical properties, and a heavily invested industry. Thus heteroepitaxy of both components is expected to yield a highly optimized overall system. For samples grown along the (001) direction, Si is a direct bandgap material, and deposition of an InAs 3nm layer reduces substantially the hole effective mass and slightly the electronic mass, decreasing the magnitude of the gap. Along the (011) and (112)-growth direction, Si QWs are indirect bandgap material, and deposition of a few InAs layers suffies to make the new material a direct-bandgap heterostructure, decreasing significantly the electronic effective mass. (011) and (112) are the experimentally most relevant growth directions since they prevent heterointerface dipoles.

Design of Heterostructures for High Efficiency Thermionic Emission

2005 ◽  
Vol 886 ◽  
Author(s):  
Zhixi Bian ◽  
Ali Shakouri
Keyword(s):  
Effective Mass ◽  
High Efficiency ◽  
Thermionic Emission ◽  
Vertical Direction ◽  
Mean Free Path ◽  
Energy Conversion Efficiency ◽  
Potential Barriers ◽  
Effective Masses ◽  
Barrier Region ◽  
Electron Mean Free Path

ABSTRACTWe use two heterostructure designs to improve the energy conversion efficiency of solid-state thermionic devices. The first method is to use a non-planar heterostructure with roughness in order of electron mean free path. This has some combined benefits of increased effective interface area, and reduced total internal reflection for the electron trajectories arriving at the interface. Monte Carlo simulations of various geometries show that the electrical conductivity and thermoelectric figure of merit can be improved for non-planar barrier compared to the planar counterpart. The second method is to use planar high barrier heterostructures with different effective masses for charge carriers in emitter and barrier regions. When an electron passes from a lower effective mass emitter and arrives at a barrier with higher effective mass, since both the lateral momentum and total energy are conserved, part of the lateral energy is coupled to the vertical direction and the electron gains momentum in the direction perpendicular to the interface to enter the barrier region. For high potential barriers, the improvement of thermionic current is about the same as the ratio of the effective masses of the two materials, which can be a factor of 5-10 for typical heterostructure material systems.

EFFECTIVE MASSES FOR DONOR BINDING ENERGIES IN QUANTUM WELL SYSTEMS

2006 ◽  
Vol 20 (24) ◽  
pp. 1529-1541 ◽  
Author(s):  
S. RAJASHABALA ◽  
K. NAVANEETHAKRISHNAN
Keyword(s):  
Quantum Well ◽  
Effective Mass ◽  
Binding Energies ◽  
Bohr Radius ◽  
Mass Variation ◽  
Effective Masses ◽  
Approximate Form ◽  
Finite Barrier ◽  
Infinite Barrier ◽  
Barrier Model

The donor ionization energies in a quantum well and quantum dot with finite and infinite barriers are estimated for different well dimensions. Using the effective mass (EM) approximation, calculations are presented with constant effective mass and position dependent effective masses that are different for finite and infinite cases. Our results reduce to an approximate form used by X. H. Qi et al., Phys. Rev. B58 (1998) 10578 in the finite barrier model and that of L. E. Oliveira and L. M. Falicov, Phys. Rev. B34 (1986) 8676 in the infinite barrier case. Results are presented by taking the GaAs quantum well as an example. The use of constant effective mass of 0.067m0 is justified for well dimensions ≥a* where a* is an effective Bohr radius which is about 100 Å. While Qi et al. found a maximum of 22% variation in the binding energies due to mass variation, we obtained nearly 100% variation when mass variations are included correctly.

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