1,224 research outputs found
The colour yellow and its immortal and mortal beauty
In this paper, another in a series of papers dealing with colour terms and their etymologies (greys, reds, blues and purples having been researched previously), the author focuses on yellows: the pigments/dyes used through history, their origins, manufacture and stories that have become inextricably linked to them; the associations that specific colours seem to evoke both on personal and collective levels (culturally and socially induced colour associations); yellow colour terms and their etymologies. The colour yellow has always held a great fascination for humans throughout history as well as serving to perpetuate various social memes, some of which are of particular significance to art history studies. The relevant etymologies and the stories they tell shed light on the history of yellow pigments and dyes, and the role they have played in our civilization, whilst providing an interesting example of a language - art history interface
Superfluid drag of two-species Bose-Einstein condensates in optical lattices
We study two-species Bose-Einstein condensates in quasi two-dimensional
optical lattices of varying geometry and potential depth. Based on the
numerically exact Bloch and Wannier functions obtained using the plane-wave
expansion method, we quantify the drag (entrainment coupling) between the
condensate components. This drag originates from the (short range)
inter-species interaction and increases with the kinetic energy. As a result of
the interplay between interaction and kinetic energy effects, the
superfluid-drag coefficient shows a non-monotonic dependence on the lattice
depth. To make contact with future experiments, we quantitatively investigate
the drag for mass ratios corresponding to relevant atomic species.Comment: 6 pages, 4 figures. Accepted in its original form but minor changes
have been don
Strategy for implementing stabilizer-based codes on solid-state qubits
We present a method for implementing stabilizer-based codes with encoding
schemes of the operator quantum error correction paradigm, e.g., the "standard"
five-qubit and CSS codes, on solid-state qubits with Ising or XY-type
interactions. Using pulse sequences, we show how to induce the effective
dynamics of the stabilizer Hamiltonian, the sum of an appropriate set of
stabilizer operators for a given code. Within this approach, the encoded states
(ground states of the stabilizer Hamiltonian) can be prepared without
measurements and preserved against both the time evolution governed by the
original qubit Hamiltonian, and energy-nonconserving errors caused by the
environment.Comment: 5 pages, 1 figur
Preserving universal resources for one-way quantum computing
The common spin Hamiltonians such as the Ising, XY, or Heisenberg model do
not have ground states that are the graph states needed in measurement-based
quantum computation. Various highly-entangled many-body states have been
suggested as a universal resource for this type of computation, however, it is
not easy to preserve these states in solid-state systems due to their short
coherence times. Here we propose a scheme for generating a Hamiltonian that has
a cluster state as ground state. Our approach employs a series of pulse
sequences inspired by established NMR techniques and holds promise for
applications in many areas of quantum information processing.Comment: 5 pages, 2 figure
Neutral edge modes in a superconductor -- topological-insulator hybrid structure in a perpendicular magnetic field
We study the low-energy edge states of a superconductor -- 3D
topological-insulator hybrid structure (NS junction) in the presence of a
perpendicular magnetic field. The hybridization of electron-like and hole-like
Landau levels due to Andreev reflection gives rise to chiral edge states within
each Landau level. We show that by changing the chemical potential of the
superconductor, this junction can be placed in a regime where the sign of the
effective charge of the edge state within the zeroth Landau level changes more
than once resulting in neutral edge modes with a finite value of the
guiding-center coordinate. We find that the appearance of these neutral edge
modes is related to the level repulsion between the zeroth and the first Landau
levels in the spectra. We also find that these neutral edge modes come in
pairs, one in the zeroth Landau level and its corresponding pair in the first.Comment: 5 page
Electron-phonon coupling in crystalline organic semiconductors: Microscopic evidence for nonpolaronic charge carriers
We consider electron(hole)-phonon coupling in crystalline organic
semiconductors, using naphthalene for our case study. Employing a
first-principles approach, we compute the changes in the self-consistent
Kohn-Sham potential corresponding to different phonon modes and go on to obtain
the carrier-phonon coupling matrix elements (vertex functions). We then
evaluate perturbatively the quasiparticle spectral residues for electrons at
the bottom of the lowest-unoccupied- (LUMO) and holes at the top of the
highest-occupied (HOMO) band, respectively obtaining and
. Along with the widely accepted notion that the
carrier-phonon coupling strengths in polyacenes decrease with increasing
molecular size, our results provide a strong microscopic evidence for the
previously conjectured nonpolaronic nature of band-like carriers in these
systems.Comment: final, published versio
Nano-friction in cavity quantum electrodynamics
The dynamics of cold trapped ions in a high-finesse resonator results from
the interplay between the long-range Coulomb repulsion and the cavity-induced
interactions. The latter are due to multiple scatterings of laser photons
inside the cavity and become relevant when the laser pump is sufficiently
strong to overcome photon decay. We study the stationary states of ions coupled
with a mode of a standing-wave cavity as a function of the cavity and laser
parameters, when the typical length scales of the two self-organizing
processes, Coulomb crystallization and photon-mediated interactions, are
incommensurate. The dynamics are frustrated and in specific limiting cases can
be cast in terms of the Frenkel-Kontorova model, which reproduces features of
friction in one dimension. We numerically recover the sliding and pinned
phases. For strong cavity nonlinearities, they are in general separated by
bistable regions where superlubric and stick-slip dynamics coexist. The cavity,
moreover, acts as a thermal reservoir and can cool the chain vibrations to
temperatures controlled by the cavity parameters and by the ions phase. These
features are imprinted in the radiation emitted by the cavity, which is readily
measurable in state-of-art setups of cavity quantum electrodynamics.Comment: 9 pages, 7 figure
Incommensurate superfluidity of bosons in a double-well optical lattice
We study bosons in the first excited Bloch band of a double-well optical
lattice, recently realized at NIST. By calculating the relevant parameters from
a realistic nonseparable lattice potential, we find that in the most favorable
cases the boson lifetime in the first excited band can be several orders of
magnitude longer than the typical nearest-neighbor tunnelling timescales, in
contrast to that of a simple single-well lattice. In addition, for sufficiently
small lattice depths the excited band has minima at nonzero momenta
incommensurate with the lattice period, which opens a possibility to realize an
exotic superfluid state that spontaneously breaks the time-reversal,
rotational, and translational symmetries. We discuss possible experimental
signatures of this novel state.Comment: 4 pages, 5 figures
Thermal mass impact on energy performance of a low, medium and heavy mass building in Belgrade
Heavy mass materials used in building structures and architecture can significantly affect building energy performance and occupant comfort. The purpose of this study was to investigate if thermal mass can improve the internal environment of a building, resulting in lower energy requirements from the mechanical systems. The study was focused on passive building energy performance and compared annual space heating and cooling energy requirements for an office building in Belgrade with several different applications of thermal mass. A three-dimensional building model was generated to represent a typical office building. Building shape, orientation, glazing to wall ratio, envelope insulation thickness, and indoor design conditions were held constant while location and thickness of building mass (concrete) was varied between cases in a series of energy simulations. The results were compared and discussed in terms of the building space heating and cooling energy and demand affected by thermal mass. The simulation results indicated that with addition of thermal mass to the building envelope and structure: 100% of all simulated cases experienced reduced annual space heating energy requirements, 67% of all simulated cases experienced reduced annual space cooling energy requirements, 83% of all simulated cases experienced reduced peak space heating demand and 50% of all simulated cases experienced reduced peak space cooling demand. The study demonstrated that there exists a potential for reducing space heating and cooling energy requirements with heavy mass construction in the analyzed climate region (Belgrade, Serbia)
Radiographic cephalometry assessment of the linear and angular parameters on cranial base in children with skeletal class III
Background/Aim. In malocclusion of skeletal class III, mandible is located in front of maxilla in sagital plain, which is manifested by a lower value of the sagital inter-jaw angle than in skeletal class I, where the jaw sagital relation is normal. Apart from the deformities on mandible and/or maxilla, in skeletal class III deformities are also frequent on the cranial base. The aim of this research was to find the differences in the parameter values on the cranial base among the children with skeletal class III and the children with skeletal class I in the period of mixed dentition. Methods. After clinical examination and orthopan-tomography, profile radiography of the head was analyzed in 60 examinees, aged from 6−12 years. The examinees were divided into two groups: group 1 - the children with skeletal class III; group 2 - the children with skeletal class I. Both linear and angular parameters on the cranial base were measured, as well as the angles of maxillary and mandible prognatism and the angle of sagital inter-jaw relation. The level of difference in the parameter values between the groups was estimated and the degree of correlation of the main angle of the cranial base with the angles of sagital position of the jaws in each of the two groups was established. Results. A significant difference between the groups was found only in the average values of the angles of maxillary prognatism and sagital interjaw relation. In the group 1, the main angle of the cranial base was in a significant correlation with the angles of sagital positions of the jaws, while in the group 2, such significance was not found. Conclusion. There were no significant differences in the parameter values on the cranial base between the groups. There was a significant correlation of the main angle of the cranial base with the angles of sagital position of the jaws in the group 1 only.
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