1,869 research outputs found
Neutron Stars with Hyperons subject to Strong Magnetic Field
Neutron stars are one of the most exotic objects in the universe and a unique
laboratory to study the nuclear matter above the nuclear saturation density. In
this work, we study the equation of state of the nuclear matter within a
relativistic model subjected to a strong magnetic field. We then apply this EoS
to study and describe some of the physical characteristics of neutron star,
especially the mass-radius relation and chemical compositions. To study the
influence of a the magnetic field and the hyperons in the stellar interior, we
consider altogether four solutions: two different values of magnetic field to
obtain a weak and a strong influence, and two configurations: a family of
neutron stars formed only by protons, electrons and neutrons and a family
formed by protons, electrons, neutrons, muons and hyperons. The limit and the
validity of the results found are discussed with some care. In all cases the
particles that constitute the neutron star are in equilibrium and zero
total net charge. Our work indicates that the effect of a strong magnetic field
has to be taken into account in the description of magnetars, mainly if we
believe that there are hyperons in their interior, in which case, the influence
of the magnetic field can increase the mass by more than 10%. We have also seen
that although a magnetar can reach 2.48, a natural explanation of
why we do not know pulsars with masses above 2.0 arises. We also
discuss how the magnetic field affects the strangeness fraction in some
standard neutron star masses and, to conclude our paper, we revisit the direct
URCA process related to the cooling of the neutron stars and show how it is
affected by the hyperons and the magnetic field.Comment: 16 pages, 8 figure
Non-Markovian Dynamics of Quantum Discord
We evaluate the quantum discord dynamics of two qubits in independent and
common non-Markovian environments. We compare the dynamics of entanglement with
that of quantum discord. For independent reservoirs the quantum discord
vanishes only at discrete instants whereas the entanglement can disappear
during a finite time interval. For a common reservoir, quantum discord and
entanglement can behave very differently with sudden birth of the former but
not of the latter. Furthermore, in this case the quantum discord dynamics
presents sudden changes in the derivative of its time evolution which is
evidenced by the presence of kinks in its behavior at discrete instants of
time.Comment: 6 pages, 4 figure
How much time does a measurement take?
We consider the problem of measurement using the Lindblad equation, which
allows the introduction of time in the interaction between the measured system
and the measurement apparatus. We use analytic results, valid for weak
system-environment coupling, obtained for a two-level system in contact with a
measurer (Markovian interaction) and a thermal bath (non-Markovian
interaction), where the measured observable may or may not commute with the
system-environment interaction. Analysing the behavior of the coherence, which
tends to a value asymptotically close to zero, we obtain an expression for the
time of measurement which depends only on the system-measurer coupling, and
which does not depend on whether the observable commutes with the system-bath
interaction. The behavior of the coherences in the case of strong
system-environment coupling, found numerically, indicates that an increase in
this coupling decreases the measurement time, thus allowing our expression to
be considered the upper limit for the duration of the process.Comment: REVISED VERSION: 17 pages, 2 figure
Epitaxial-tau(Mn,Ni)Al/(Al,Ga)As heterostructures: Magnetic and magneto-optic properties
Ferromagnetic Perpendicularly magnetized epitaxial thin films of tau (Mn,Ni)AI have been successfully grown on AlAs/GaAs heterostructures by molecular beam epitaxy. We have investigated the polar Kerr rotation and magnetization of tau MnAl and (Mn,Ni) Al as a function of Mn and Ni concentration. The largest polar Kerr rotation and remnant magnetization were obtained for Mn0.5Al0.5 thin films with values of 0.16-degrees and 224 emu/cm3, respectively. We observed that the Kerr rotation and magnetization remained constant with Ni additions up to about 12 at. % and subsequently decreased with further Ni additions. We discuss these results and one possible method of enhancing the Kerr rotation
Electric field inversion asymmetry: Rashba and Stark effects for holes in resonant tunneling devices
We report experimental evidence of excitonic spin-splitting, in addition to
the conventional Zeeman effect, produced by a combination of the Rashba
spin-orbit interaction, Stark shift and charge screening. The
electric-field-induced modulation of the spin-splitting are studied during the
charging and discharging processes of p-type GaAs/AlAs double barrier resonant
tunneling diodes (RTD) under applied bias and magnetic field. The abrupt
changes in the photoluminescence, with the applied bias, provide information of
the charge accumulation effects on the device.Comment: 4 pages, 2 figure
Elastic Constitutive Laws and Stability Analyses
In this paper, the influence of several elastic constitutive laws upon the stability analyses of plane trusses is discussed. The chosen laws are connected to the engineering strain, Green’s strain and logarithmic strain concepts. A geometrically exact nonlinear formulation for a truss bar element is developed for each of them and the correspondent tangent stiffness matrices are obtained. The stability analyses of some sample plane trusses are performed by finding the conditions when the determinant of their respective global tangent stiffness matrices is found to be zero. The first example is a symmetric two-bar structure and both limit loads and buckling loads are plotted for the full range of possible initial inclination angles of the bars for the three chosen constitutive laws. A similar truss with an extra vertical bar is studied to discuss possible material instability if Green’s strain concept is adopted
Cobertura morta de leguminosas no controle de ervas invasoras em sistema de cultivo em faixas (Alley cropping).
bitstream/item/32692/1/CPATU-BP137.pd
Índices de saturação por bases do solo na eficiência de fosfatos reativos associada à produção de milho.
Fertbio 2014
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