1,455 research outputs found
Atomic States Entanglement in Carbon Nanotubes
The entanglement of two atoms (ions) doped into a carbon nanotube has been
investigated theoretically. Based on the photon Green function formalism for
quantizing electromagnetic field in the presence of carbon nanotubes,
small-diameter metallic nanotubes are shown to result in a high degree of the
two-qubit atomic entanglement for long times due to the strong atom-field
coupling.Comment: 4 pages, 2 figure
Bright and dark excitons in an atom--pair filled optical lattice within a cavity
We study electronic excitations of a degenerate gas of atoms trapped in pairs
in an optical lattice. Local dipole-dipole interactions produce a long lived
antisymmetric and a short lived symmetric superposition of individual atomic
excitations as the lowest internal on-site excitations. Due to the much larger
dipole moment the symmetric states couple efficiently to neighbouring lattice
sites and can be well represented by Frenkel excitons, while the antisymmetric
dark states stay localized. Within a cavity only symmetric states couple to
cavity photons inducing long range interactions to form polaritons. We
calculate their dispersion curves as well as cavity transmission and reflection
spectra to observe them. For a lattice with aspherical sites bright and dark
states get mixed and their relative excitation energies depend on photon
polarizations. The system should allow to study new types of solid state
phenomena in atom filled optical lattices
Variability of Pennsylvanian-Permian Carbonate Associations and Implications for NW Pangea Palaeogeography, East-Central British Columbia, Canada
Different stages of Pennsylvanian-Permian carbonate sedimentation in east-central British Columbia record a complex history of changing environments influenced by evolving palaeogeography and climate. Newly recognized tectonically controlled features affected the distribution and variability of carbonate associations, providing new interpretations for this portion of the west coast of Pangea. Both a heterozoan (cool water) and photozoan (warm-water) association were identified on either side of a palaeogeographic high here informally termed “Tipinahokan Peninsula”. Cool water carbonates were located outboard, or to the west of this high, an area influenced by upwelling waters. Inboard of this high, a warm, protected sea developed, here termed “Kisosowin Sea”. This configuration and palaeolatitude is similar to that of Baja California, Mexico and the Sea of Cortéz, providing a good modern analog for these deposits where warm water carbonates grow at latitudes otherwise dominated by cool water deposits. The warm sea provided a place for a photozoan association to develop during the Permian when the low latitude NW coast of Pangea was dominated by cool water carbonates
Models of Lobbying Practices in Maritime Affairs of USA and European Countries
The article is based on a comparative analysis of the most effective institutionally established models of modern lobbying practices for pursuing interests in the field of maritime activities in the developed countries of Europe and the United States. The study is carried out on several grounds: the Full Time Equivalent (FTE) of a lobbyist, the expected financial investments of organizations in lobbying activities, an assessment of the transparency of the activities of lobbying organizations. Based on the revealed correlation of FTE and expected investments, the analysis of the model’s efficiency is simplified to an estimate of the value of its total FTE of the described models. Particular emphasis is placed on the analysis of lobbying in cooperation with the European Commission. It has been determined that environmental organizations and groups of influence that are not directly related to maritime activities are particularly active in lobbying for maritime activities. When comparing the lobbying infrastructure of Western countries in the context of its effectiveness in defending national interests, there is a significant advantage of the United States over the European Union. Regarding the adoption of Western models of lobbying practices and the spread of institutionalization of lobbying on the territory of the Russian Federation, it is recognized that for Russia, its maritime policy, the most effective American model would be, based on a single legal basis, allowing taxed lobbying agents to act in concert on the domestic and global market in the interests of private companies and the nation state
Proton Wires in an Electric Field: the Impact of Grotthuss Mechanism on Charge Translocation
We present the results of the modeling of proton translocation in finite
H-bonded chains in the framework of two-stage proton transport model. We
explore the influence of reorientation motion of protons, as well as the effect
of electric field and proton correlations on system dynamics. An increase of
the reorientation energy results in the transition of proton charge from the
surrounding to the inner water molecules in the chain. Proton migration along
the chain in an external electric field has a step-like character, proceeding
with the occurrence of electric field threshold-type effects and drastic
redistribution of proton charge. Electric field applied to correlated chains
induces first a formation of ordered dipole structures for lower field
strength, and than, with a further field strength increase, a stabilization of
states with Bjerrum D-defects. We analyze the main factors responsible for the
formation/annihilation of Bjerrum defects showing the strong influence of the
complex interplay between reorientation energy, electric field and temperature
in the dynamics of proton wire.Comment: 28 pages, 9 figure
On the vibron dressing in the --helicoidal macromolecular chains
We present a study of the physical properties of the vibrational excitation
in --helicoidal macromolecular chains, caused by the interaction with
acoustical and optical phonon modes. The influence of the temperature and the
basic system parameters on the vibron dressing has been analyzed by employing
the simple mean--field approach based on the variational extension of the
Lang--Firsov unitary transformation. Applied approach predicts a region in
system parameter space where one takes place an abrupt transition from
partially dressed (light and mobile) to fully dressed (immobile) vibron states.
We found that the boundary of this region depends on system temperature and
type of bond among structural elements in the macromolecular chain.Comment: 22 pages, 12 figures, title changed, the interaction with optical
phonon modes jointly with acoustical ones added, consideration significantly
enlarged, references added, the paper develops the results of
arxiv:1210.3918, accepted for publication in Chinese Physics
Pecularities of Hall effect in GaAs/{\delta}<Mn>/GaAs/In\timesGa1-\timesAs/GaAs (\times {\approx} 0.2) heterostructures with high Mn content
Transport properties of GaAs/{\delta}/GaAs/In\timesGa1-\timesAs/GaAs
structures containing InxGa1-xAs (\times {\approx} 0.2) quantum well (QW) and
Mn delta layer (DL) with relatively high, about one Mn monolayer (ML) content,
are studied. In these structures DL is separated from QW by GaAs spacer with
the thickness ds = 2-5 nm. All structures possess a dielectric character of
conductivity and demonstrate a maximum in the resistance temperature dependence
Rxx(T) at the temperature {\approx} 46K which is usually associated with the
Curie temperature Tc of ferromagnetic (FM) transition in DL. However, it is
found that the Hall effect concentration of holes pH in QW does not decrease
below TC as one ordinary expects in similar systems. On the contrary, the
dependence pH(T) experiences a minimum at T = 80-100 K depending on the spacer
thickness, then increases at low temperatures more strongly than ds is smaller
and reaches a giant value pH = (1-2)\cdot10^13 cm^(-2). Obtained results are
interpreted in the terms of magnetic proximity effect of DL on QW, leading to
induce spin polarization of the holes in QW. Strong structural and magnetic
disorder in DL and QW, leading to the phase segregation in them is taken into
consideration. The high pH value is explained as a result of compensation of
the positive sign normal Hall effect component by the negative sign anomalous
Hall effect component.Comment: 19 pages, 6 figure
- …