905 research outputs found
Structure, dynamics and bifurcations of discrete solitons in trapped ion crystals
We study discrete solitons (kinks) accessible in state-of-the-art trapped ion
experiments, considering zigzag crystals and quasi-3D configurations, both
theoretically and experimentally. We first extend the theoretical understanding
of different phenomena predicted and recently experimentally observed in the
structure and dynamics of these topological excitations. Employing tools from
topological degree theory, we analyze bifurcations of crystal configurations in
dependence on the trapping parameters, and investigate the formation of kink
configurations and the transformations of kinks between different structures.
This allows us to accurately define and calculate the effective potential
experienced by solitons within the Wigner crystal, and study how this
(so-called Peierls-Nabarro) potential gets modified to a nonperiodic globally
trapping potential in certain parameter regimes. The kinks' rest mass (energy)
and spectrum of modes are computed and the dynamics of linear and nonlinear
kink oscillations are analyzed. We also present novel, experimentally observed,
configurations of kinks incorporating a large-mass defect realized by an
embedded molecular ion, and of pairs of interacting kinks stable for long
times, offering the perspective for exploring and exploiting complex collective
nonlinear excitations, controllable on the quantum level.Comment: 25 pages, 10 figures, v2 corrects Fig. 2 and adds some text and
reference
Photoemission kinks and phonons in cuprates
One of the possible mechanisms of high Tc superconductivity is Cooper pairing
with the help of bosons, which change the slope of the electronic dispersion as
observed by photoemission. Giustino et al. calculated that in the high
temperature superconductor La1.85Sr0.15CuO4 crystal lattice vibrations
(phonons) should have a negligible effect on photoemission spectra and
concluded that phonons do not play an important role. We show that the
calculations employed by Giustino et al. fail to reproduce huge influence of
electron-phonon coupling on important phonons observed in experiments. Thus one
would expect these calculations to similarly fail in explaining the role of
electron-phonon coupling for the electronic dispersion.Comment: To appear in Nature as a Brief Communiction Arisin
Factors Affecting Capture Rates of Insect Taxa by Retail Electrocutors and Eliminators in Northern Lower Michigan
We compare the abundance and types of insects captured at several locations, with and without a chemical attractant and in varying weather conditions using two different devices advertised to kill biting insects. Using both an insect electrocutor that uses ultraviolet light as an attractant, with and without octenol as an added attractant, and an insect eliminator that uses carbon dioxide, heat and octenol as attractants, more non-biting than biting insects were captured. Numerous harmless and beneficial insects were killed with electrocutors. Although eliminators were more target-specific, they captured fewer insects overall compared to electrocutors. The numbers and types of insects captured also varied by location and temperature conditions. More insects were killed by electrocutors located next to a lake compared to those located in an inland forested area and more were killed at lower compared to higher heights above the ground. More insects were also killed by electrocutors on warmer than on cooler nights. More non-biting insects were killed with electrocutors baited with octenol than without octenol
Quantum Mechanical Realization of a Popescu-Rohrlich Box
We consider quantum ensembles which are determined by pre- and
post-selection. Unlike the case of only pre-selected ensembles, we show that in
this case the probabilities for measurement outcomes at intermediate times
satisfy causality only rarely; such ensembles can in general be used to signal
between causally disconnected regions. We show that under restrictive
conditions, there are certain non-trivial bi-partite ensembles which do satisfy
causality. These ensembles give rise to a violation of the CHSH inequality,
which exceeds the maximal quantum violation given by Tsirelson's bound, , and obtains the Popescu-Rohrlich bound for the maximal
violation, . This may be regarded as an a posteriori
realization of super-correlations, which have recently been termed
Popescu-Rohrlich boxes.Comment: 5 page
Origin of the Thermal Radiation in a Solid-State Analog of a Black-Hole
An effective black-hole-like horizon occurs, for electromagnetic waves in
matter, at a surface of singular electric and magnetic permeabilities. In a
physical dispersive medium this horizon disappears for wave numbers with
. Nevertheless, it is shown that Hawking radiation is still emitted if
free field modes with are in their ground state.Comment: 13 Pages, 3 figures, Revtex with epsf macro
Trans-Planckian Tail in a Theory with a Cutoff
Trans-planckian frequencies can be mimicked outside a black-hole horizon as a
tail of an exponentially large amplitude wave that is mostly hidden behind the
horizon. The present proposal requires implementing a final state condition.
This condition involves only frequencies below the cutoff scale. It may be
interpreted as a condition on the singularity. Despite the introduction of the
cutoff, the Hawking radiation is restored for static observers. Freely falling
observers see empty space outside the horizon, but are "heated" as they cross
the horizon.Comment: 17 pages, RevTe
THE INFLUENCE OF THE DIGITAL ECONOMY ON THE DEVELOPMENT OF THE DOMESTIC ECONOMY
The article examines the problems and prospects for the development of the digital economy in Ukraine. The current trends of new technological solutions and opportunities are identified, because global informatization intensifies this process. The effective use of digital economy tools, the means of which is to ensure information security and stability in the country, is described.The article examines the problems and prospects for the development of the digital economy in Ukraine. The current trends of new technological solutions and opportunities are identified, because global informatization intensifies this process. The effective use of digital economy tools, the means of which is to ensure information security and stability in the country, is described
Dispersion of Magnetic Excitations in Superconducting Optimally Doped YBa_2Cu_3O_6.95
Detailed neutron scattering measurements of YBa_2Cu_3O_6.95 found that the
resonance peak and incommensurate magnetic scattering induced by
superconductivity represent the same physical phenomenon: two dispersive
branches that converge near 41 meV and the in-plane wave-vector q_af=(pi/a,
pi/a) to form the resonance peak. One branch has a circular symmetry around
q_af and quadratic downward dispersion from ~41 meV to the spin gap of
33+-1meV. The other, of lower intensity, disperses from ~41 meV to at least 55
meV. Our results exclude a quartet of vertical incommensurate rods in q-w space
expected from spin waves produced by dynamical charge stripes as an origin of
the observed incommensurate scattering in optimally-doped YBCO.Comment: Version 3: Author change. Changes made throughout the text and minor
changes in figures, Model parameters slightly changed after a small error in
the calculation was discovere
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