8,255 research outputs found
Effect of band filling in the Kondo lattice: A mean-field approach
The usual Kondo-lattice, including an antiferromagnetic exchange interaction
between nearest-neighboring localized spins, is treated here in a mean-field
scheme that introduces two mean-field parameters: one associated with the local
Kondo effect, and the other related to the magnetic correlations between
localized spins. Phases with short-range magnetic correlations or coexistence
between those and the Kondo effect are obtained. By varying the number of
electrons in the conduction band, we notice that the Kondo effect tends to be
suppressed away from half filling, while magnetic correlations can survive if
the Heisenberg coupling is strong enough. An enhanced linear coefficient of the
specific heat is obtained at low temperatures in the metallic state.Comment: 7 pages, ReVTeX two-column, 7 figure
An explanation for the curious mass loss history of massive stars: from OB stars, through Luminous Blue Variables to Wolf-Rayet stars
The stellar winds of massive stars show large changes in mass-loss rates and
terminal velocities during their evolution from O-star through the Luminous
Blue Variable phase to the Wolf-Rayet phase. The luminosity remains
approximately unchanged during these phases. These large changes in wind
properties are explained in the context of the radiation driven wind theory, of
which we consider four different models. They are due to the evolutionary
changes in radius, gravity and surface composition and to the change from
optically thin (in continuum) line driven winds to optically thick radiation
driven winds.Comment: Accepted for publication in Astronomy and Astrophysics (Letter to the
Editor
Tap For Battle: Perancangan Casual Game pada Smartphone Android
Smartphones have become a necessity. Almost everyone uses a smartphone in a variety of activities. Both young and old are sure to utilize this technology, for a wide range of activities such as doing the work, doing school work or enjoying entertainment. The purpose of this research is to build a casual-action game with war theme. The game is built for Android smartphone that has multi touch screen capability. The research methods used in this research are data collection and analysis method including user analysis with questionnaire. Furthermore, IMSDD method is implemented for game design and development phase including system requirement analysis, system design, system implementation, finally system evaluation. In this research, we conclude that 83.9% participants enjoyed the game with touch-screen as the game control
Gravity on de-Sitter 3-Brane, Induced Einstein-Hilbert Term and Massless Gravitons
We study the extensions of DGP model which are described by five-dimensional
Einstein gravity coupled covariantly to 3-brane with induced gravity term and
consider warped D=4 de Sitter background field solutions on the brane. The case
with included D=5 AdS cosmological term is also considered. Following
background field method we obtain the field equations described by the
Lagrangean terms bilinear in gravitational field. In such a linear field
approximation on curved dS background we calculate explicitly the
five-dimensional massive terms as well as the mass-like ones on the brane. We
investigate the eigenvalue problem of Schr\"{o}dinger-like equation in fifth
dimension for graviton masses and discuss the existence of massless as well as
massive graviton modes in the bulk and on the brane without and with induced
gravity.Comment: LaTeX 26 pages, the version which appears in Class. Quant. Gra
Origin of the reduced exchange bias in epitaxial FeNi(111)/CoO(111) bilayer
We have employed Soft and Hard X-ray Resonant Magnetic Scattering and
Polarised Neutron Diffraction to study the magnetic interface and the bulk
antiferromagnetic domain state of the archetypal epitaxial
NiFe(111)/CoO(111) exchange biased bilayer. The combination of
these scattering tools provides unprecedented detailed insights into the still
incomplete understanding of some key manifestations of the exchange bias
effect. We show that the several orders of magnitude difference between the
expected and measured value of exchange bias field is caused by an almost
anisotropic in-plane orientation of antiferromagnetic domains. Irreversible
changes of their configuration lead to a training effect. This is directly seen
as a change in the magnetic half order Bragg peaks after magnetization
reversal. A 30 nm size of antiferromagnetic domains is extracted from the width
the (1/2 1/2 1/2) antiferromagnetic magnetic peak measured both by neutron and
x-ray scattering. A reduced blocking temperature as compared to the measured
antiferromagnetic ordering temperature clearly corresponds to the blocking of
antiferromagnetic domains. Moreover, an excellent correlation between the size
of the antiferromagnetic domains, exchange bias field and frozen-in spin ratio
is found, providing a comprehensive understanding of the origin of exchange
bias in epitaxial systems.Comment: 8 pages, 5 figures, submitte
Van Kampen's expansion approach in an opinion formation model
We analyze a simple opinion formation model consisting of two parties, A and
B, and a group I, of undecided agents. We assume that the supporters of parties
A and B do not interact among them, but only interact through the group I, and
that there is a nonzero probability of a spontaneous change of opinion (A->I,
B->I). From the master equation, and via van Kampen's Omega-expansion approach,
we have obtained the "macroscopic" evolution equation, as well as the
Fokker-Planck equation governing the fluctuations around the deterministic
behavior. Within the same approach, we have also obtained information about the
typical relaxation behavior of small perturbations.Comment: 17 pages, 6 figures, submited to Europ.Phys.J.
Wave radiation from a truncated cylinder of arbitrary cross section
In this paper, a semi-analytical model for solving wave radiation from a truncated cylinder of arbitrary cross section is presented based on linear potential flow theory. The water domain is divided into the interior domain beneath the cylinder and the exterior domain outside the vertical cylinder column. Radiated spatial potentials in these subdomains are expressed as a series expansion of eigen-functions using the method of separation of variables. The continuity conditions for pressure and velocity are satisfied at the interface of the two domains, where the Fourier series expansion method is employed to deal with the radius function associated terms. Therefore, the unknown coefficients in the radiated potential expressions are determined by means of the eigen-function matching method. Hydrodynamic coefficients of the truncated cylinder are evaluated directly based on the radiated spatial potentials. Case studies on wave radiation from a truncated cylinder with “cosine” and “circular” cross sections show a good agreement between the semi-analytical results of added-mass/radiation damping and numerical ones/published data. The validated semi-analytical model is then adopted to study the hydrodynamic characteristics of truncated cylinders with “circular”, “cosine”, “elliptical” and “quasi-elliptical” sections. For the latter case, the influence of draft on wave radiation is also investigated
Identification of HCCC as a diffuse interstellar band carrier
We present strong evidence that the broad, diffuse interstellar bands (DIBs)
at 4881 and 5450\,\AA are caused by the
B\,^1B\,\,X\,^1A transition of HCCC (l-CH).
The large widths of the bands are due to the short lifetime of the B\,^1B
electronic state. The bands are predicted from absorption measurements in a
neon matrix and observed by cavity ring-down in the gas phase and show exact
matches to the profiles and wavelengths of the two broad DIBs. The strength of
the 5450\,\AA DIB leads to a l-CH column density of
cm towards HD\,183143 and
\,cm to HD\,206267. Despite similar values of
(), the 4881 and 5450\,\AA DIBs in HD\,204827 are less than one third
their strength in HD\,183143, while the column density of interstellar C is
unusually high for HD\,204827 but undetectable for HD\,183143. This can be
understood if C has been depleted by hydrogenation to species such as
l-CH towards HD\,183143. There are also three rotationally resolved
sets of triplets of l-CH in the 61506330\,\AA region. Simulations,
based on the derived spectroscopic constants and convolved with the expected
instrumental and interstellar line broadening, show credible coincidences with
sharp, weak DIBs for the two observable sets of triplets. The region of the
third set is too obscured by the -band of telluric O.Comment: 22 pages, 9 figure
Jacobi structures revisited
Jacobi algebroids, that is graded Lie brackets on the Grassmann algebra
associated with a vector bundle which satisfy a property similar to that of the
Jacobi brackets, are introduced. They turn out to be equivalent to generalized
Lie algebroids in the sense of Iglesias and Marrero and can be viewed also as
odd Jacobi brackets on the supermanifolds associated with the vector bundles.
Jacobi bialgebroids are defined in the same manner. A lifting procedure of
elements of this Grassmann algebra to multivector fields on the total space of
the vector bundle which preserves the corresponding brackets is developed. This
gives the possibility of associating canonically a Lie algebroid with any local
Lie algebra in the sense of Kirillov.Comment: 20 page
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