1,206 research outputs found
Mean field loops versus quantum anti-crossing nets in trapped Bose-Einstein condensates
We study a Bose-Einstein condensate trapped in an asymmetric double well
potential. Solutions of the time-independent Gross-Pitaevskii equation reveal
intrinsic loops in the energy (or chemical potential) level behavior when the
shape of the potential is varied. We investigate the corresponding behavior of
the quantum (many-body) energy levels. Applying the two-mode approximation to
the bosonic field operators, we show that the quantum energy levels create an
anti-crossing net inside the region bounded by the loop of the mean field
solution.Comment: 4 pages, 6 figures, version accepted for publication in European
Physical Journal
Dark soliton in a disorder potential
We consider dark soliton in a Bose-Einstein condensate in the presence of a
weak disorder potential. Deformation of the soliton shape is analyzed within
the Bogoliubov approach and by employing expansion in eigenstates of the
P\"oschl-Teller Hamiltonian. Comparison of the results with the numerical
simulations indicates that the linear response analysis reveals good agreement
even if the strength of the disorder is of the order of the chemical potential
of the system. In the second part of the paper we concentrate on quantum nature
of the dark soliton and demonstrate that the soliton may reveal Anderson
localization in the presence of a disorder. The Anderson localized soliton may
decay due to quasi-particle excitations induced by the disorder. However, we
show that the corresponding lifetime is much longer than condensate lifetime in
a typical experiment.Comment: 10 pages, 3 figures, version accepted for publication in Phys. Rev.
PENGARUH TATA KELOLA PERUSAHAAN INTERNAL TERHADAP PRAKTIK MANAJEMEN LABA (Studi Kasus Pada Perusahaan Di Bursa Efek Indonesia Tahun 2013 – 2015)
Internal corporate governance has a very important role in controlling, coordinating and controlling the performance of company employees in order to build a healthy company. The purpose of this study is to analyze the practice of earnings management as measured by discretionary accrual, can be influenced by the characteristics of internal corporate governance, namely the size of the board of commissioners, the composition of the board of commissioners, the size of the audit committee, the composition of the audit committee and the size of the company.
The data used in this research is secondary data that is the annual financial statements of companies in the year 2013-2015 listed on the Stock Exchange (www.idx.co.id) sample used is a company that reports the audit committee. Data processing method used is multiple linear regression analysis.
The results showed that firm size has significant effect with earnings management with positive direction. Meanwhile, other internal corporate governance variables such as board size, board composition, audit committee size and audit committee composition have no effect on earnings management practices
Driven Rydberg atoms reveal quartic level repulsion
The dynamics of Rydberg states of a hydrogen atom subject simultaneously to
uniform static electric field and two microwave fields with commensurate
frequencies is considered in the range of small fields amplitudes. In the
certain range of the parameters of the system the classical secular motion of
the electronic ellipse reveals chaotic behavior. Quantum mechanically, when the
fine structure of the atom is taken into account, the energy level statistics
obey predictions appropriate for the symplectic Gaussian random matrix
ensemble.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev. Let
From solar to stellar corona: the role of wind, rotation and magnetism
Observations of surface magnetic fields are now within reach for many stellar
types thanks to the development of Zeeman-Doppler Imaging. These observations
are extremely useful for constraining rotational evolution models of stars, as
well as for characterizing the generation of magnetic field. We recently
demonstrated that the impact of coronal magnetic field topology on the
rotational braking of a star can be parametrized with a scalar parameter: the
open magnetic flux. However, without running costly numerical simulations of
the stellar wind, reconstructing the coronal structure of the large scale
magnetic field is not trivial. An alternative -broadly used in solar physics-
is to extrapolate the surface magnetic field assuming a potential field in the
corona, to describe the opening of the field lines by the magnetized wind. This
technique relies on the definition of a so-called source surface radius, which
is often fixed to the canonical value of 2.5Rsun. However this value likely
varies from star to star. To resolve this issue, we use our extended set of
2.5D wind simulations published in 2015, to provide a criteria for the opening
of field lines as well as a simple tool to assess the source surface radius and
the open magnetic flux. This allows us to derive the magnetic torque applied to
the star by the wind from any spectropolarimetric observation. We conclude by
discussing some estimations of spin-down time scales made using our technique,
and compare them to observational requirements.Comment: Accepted for publication in the Astrophysical Journa
Magnetic Wreaths and Cycles in Convective Dynamos
Solar-type stars exhibit a rich variety of magnetic activity. Seeking to
explore the convective origins of this activity, we have carried out a series
of global 3D magnetohydrodynamic (MHD) simulations with the anelastic spherical
harmonic (ASH) code. Here we report on the dynamo mechanisms achieved as the
effects of artificial diffusion are systematically decreased. The simulations
are carried out at a nominal rotation rate of three times the solar value
(3), but similar dynamics may also apply to the Sun. Our previous
simulations demonstrated that convective dynamos can build persistent toroidal
flux structures (magnetic wreaths) in the midst of a turbulent convection zone
and that high rotation rates promote the cyclic reversal of these wreaths. Here
we demonstrate that magnetic cycles can also be achieved by reducing the
diffusion, thus increasing the Reynolds and magnetic Reynolds numbers. In these
more turbulent models, diffusive processes no longer play a significant role in
the key dynamical balances that establish and maintain the differential
rotation and magnetic wreaths. Magnetic reversals are attributed to an
imbalance in the poloidal magnetic induction by convective motions that is
stabilized at higher diffusion levels. Additionally, the enhanced levels of
turbulence lead to greater intermittency in the toroidal magnetic wreaths,
promoting the generation of buoyant magnetic loops that rise from the deep
interior to the upper regions of our simulated domain. The implications of such
turbulence-induced magnetic buoyancy for solar and stellar flux emergence are
also discussed.Comment: 21 pages, 16 figures, accepted for publication in Ap
Root anatomical traits contribute to deeper rooting of maize under compacted field conditions
© The Author(s) 2020. To better understand the role of root anatomy in regulating plant adaptation to soil mechanical impedance, 12 maize lines were evaluated in two soils with and without compaction treatments under field conditions. Penetrometer resistance was 1–2 MPa greater in the surface 30 cm of the compacted plots at a water content of 17–20% (v/v). Root thickening in response to compaction varied among genotypes and was negatively associated with rooting depth at one field site under non-compacted plots. Thickening was not associated with rooting depth on compacted plots. Genotypic variation in root anatomy was related to rooting depth. Deeper-rooting plants were associated with reduced cortical cell file number in combination with greater mid cortical cell area for node 3 roots. For node 4, roots with increased aerenchyma were deeper roots. A greater influence of anatomy on rooting depth was observed for the thinner root classes. We found no evidence that root thickening is related to deeper rooting in compacted soil; however, anatomical traits are important, especially for thinner root classes
Global-scale wreath-building dynamos in stellar convection zones
When stars like our Sun are young they rotate rapidly and are very
magnetically active. We explore dynamo action in rapidly rotating suns with the
3-D MHD anelastic spherical harmonic (ASH) code. The magnetic fields built in
these dynamos are organized on global-scales into wreath-like structures that
span the convection zone. Wreath-building dynamos can undergo quasi-cyclic
reversals of polarity and such behavior is common in the parameter space we
have been able to explore. These dynamos do not appear to require tachoclines
to achieve their spatial or temporal organization. Wreath-building dynamos are
present to some degree at all rotation rates, but are most evident in the more
rapidly rotating simulations.Comment: 8 pages, 4 figures. To appear in IAU 271: "Astrophysical Dynamics:
from Stars to Galaxies
- …