19,702 research outputs found
Edge and bulk merons in double quantum dots with spontaneous interlayer phase coherence
We have investigated nucleation of merons in double quantum dots when a
lateral distortion with a reflection symmetry is present in the confinement
potential. We find that merons can nucleate both inside and at the edge of the
dots. In addition to these merons, our results show that electron density
modulations can be also present inside the dots. An edge meron appears to have
approximately a half integer winding number.Comment: 5 pages, 4 figures, Proceedings of 17th International Conference on
High Magnetic Fields in Semiconductor Physic
Mounting technique for pressure transducers minimizes measurement interferences
Miniaturized transducers are fabricated from commercially available four-arm semiconductor gages; transducers are connected as bridge circuit and mounted on internal face of small diaphragm. Jacket made of conductive plastic may be needed to avoid buildup or static charges
Hole maximum density droplets of an antidot in strong magnetic fields
We investigate a quantum antidot in the integer quantum Hall regime (the
filling factor is two) by using a Hartree-Fock approach and by transforming the
electron antidot into a system which confines holes via an electron-hole
transformation. We find that its ground state is the maximum density droplet of
holes in certain parameter ranges. The competition between electron-electron
interactions and the confinement potential governs the properties of the hole
droplet such as its spin configuration. The ground-state transitions between
the droplets with different spin configurations occur as magnetic field varies.
For a bell-shape antidot containing about 300 holes, the features of the
transitions are in good agreement with the predictions of a recently proposed
capacitive interaction model for antidots as well as recent experimental
observations. We show this agreement by obtaining the parameters of the
capacitive interaction model from the Hartree-Fock results. An inverse
parabolic antidot is also studied. Its ground-state transitions, however,
display different magnetic-field dependence from that of a bell-shape antidot.
Our study demonstrates that the shape of antidot potential affects its physical
properties significantly.Comment: 12 pages, 11 figure
Unified Analysis of Cosmological Perturbations in Generalized Gravity
In a class of generalized Einstein's gravity theories we derive the equations
and general asymptotic solutions describing the evolution of the perturbed
universe in unified forms. Our gravity theory considers general couplings
between the scalar field and the scalar curvature in the Lagrangian, thus
includes broad classes of generalized gravity theories resulting from recent
attempts for the unification. We analyze both the scalar-type mode and the
gravitational wave in analogous ways. For both modes the large scale evolutions
are characterized by the same conserved quantities which are valid in the
Einstein's gravity. This unified and simple treatment is possible due to our
proper choice of the gauges, or equivalently gauge invariant combinations.Comment: 4 pages, revtex, no figure
Relativistic Hydrodynamic Cosmological Perturbations
Relativistic cosmological perturbation analyses can be made based on several
different fundamental gauge conditions. In the pressureless limit the variables
in certain gauge conditions show the correct Newtonian behaviors. Considering
the general curvature () and the cosmological constant () in the
background medium, the perturbed density in the comoving gauge, and the
perturbed velocity and the perturbed potential in the zero-shear gauge show the
same behavior as the Newtonian ones in general scales. In the first part, we
elaborate these Newtonian correspondences. In the second part, using the
identified gauge-invariant variables with correct Newtonian correspondences, we
present the relativistic results with general pressures in the background and
perturbation. We present the general super-sound-horizon scale solutions of the
above mentioned variables valid for general , , and generally
evolving equation of state. We show that, for vanishing , the
super-sound-horizon scale evolution is characterised by a conserved variable
which is the perturbed three-space curvature in the comoving gauge. We also
present equations for the multi-component hydrodynamic situation and for the
rotation and gravitational wave.Comment: 16 pages, no figure, To appear in Gen. Rel. Gra
String theoretic axion coupling and the evolution of cosmic structures
We examine the effects of the axion coupling to on the evolution
of cosmic structures. It is shown that the evolutions of the scalar- and
vector-type perturbations are not affected by this axion coupling. However the
axion coupling causes an asymmetric evolution of the two polarization states of
the tensor-type perturbation, which may lead to a sizable polarization
asymmetry in the cosmological gravitational wave if inflation involves a period
in which the axion coupling is important. The polarization asymmetry produced
during inflation are conserved over the subsequent evolution as long as the
scales remain in the large-scale limit, and thus this may lead to an observable
trace in the cosmic microwave background radiation.Comment: 10 pages, REVte
Earth Pressures on Walls of a Deep Excavation
This paper reports recorded earthpressures acting on diaphragm walls during a deep excavation carried out in a soft ground and discusses factors affecting the readings. The main theme of the paper is on wall friction and its influence on vertical earthpressures. It can be demonstrated that the assumption normally adopted in the design of the retaining structures for braced excavations that the vertical earthpressures equal to the overburden pressures could be erroneous. As a result, the vertical pressures on the active side are often over- estimated and those on the passive side under-estimated. In conclusion, it is appropriate for soft to medium stiff sites to assume that the angle of wall friction equals to the angle of internal friction of soils in computing the limiting active and passive earth pressur.es for designing the retaining structures of braced excavations
Single electron control in n-type semiconductor quantum dots using non-Abelian holonomies generated by spin orbit coupling
We propose that n-type semiconductor quantum dots with the Rashba and
Dresselhaus spin orbit interactions may be used for single electron
manipulation through adiabatic transformations between degenerate states. All
the energy levels are discrete in quantum dots and possess a double degeneracy
due to time reversal symmetryin the presence of the Rashba and/or Dresselhaus
spin orbit coupling terms. We find that the presence of double degeneracy does
not necessarily give rise to a finite non-Abelian (matrix) Berry phase. We show
that a distorted two-dimensional harmonic potential may give rise to
non-Abelian Berry phases. The presence of the non-Abelian Berry phase may be
tested experimentally by measuring the optical dipole transitions.Comment: accepted in Phys. Rev.
Quantum State Discrimination with General Figures of Merit
We solve the problem of quantum state discrimination with "general
(symmetric) figures of merit" for an even number of symmetric quantum bits with
use of the no-signaling principle. It turns out that conditional probability
has the same form for any figure of merit. Optimal measurement and
corresponding conditional probability are the same for any monotonous figure of
merit.Comment: 5 pages, 2 figure
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