4,372 research outputs found
A Universal Lifetime Distribution for Multi-Species Systems
Lifetime distributions of social entities, such as enterprises, products, and
media contents, are one of the fundamental statistics characterizing the social
dynamics. To investigate the lifetime distribution of mutually interacting
systems, simple models having a rule for additions and deletions of entities
are investigated. We found a quite universal lifetime distribution for various
kinds of inter-entity interactions, and it is well fitted by a
stretched-exponential function with an exponent close to 1/2. We propose a
"modified Red-Queen" hypothesis to explain this distribution. We also review
empirical studies on the lifetime distribution of social entities, and
discussed the applicability of the model.Comment: 10 pages, 6 figures, Proceedings of Social Modeling and Simulations +
Econophysics Colloquium 201
Interminiband Rabi oscillations in biased semiconductor superlattices
Carrier dynamics at energy level anticrossings in biased semiconductor
superlattices, was studied in the time domain by solving the time-dependent
Schroedinger equation. The resonant nature of interminiband Rabi oscillations
has been explicitly demonstrated to arise from interference of intrawell and
Bloch oscillations. We also report a simulation of direct Rabi oscillations
across three minibands, in the high field regime, due to interaction between
three strongly coupled minibands.Comment: 13 pages, 16 figure
Strong correlation and massive spectral-weight redistribution induced spin density wave in a-Fe1.06Te
The electronic structure of a-Fe1.06Te is studied with angle-resolved
photoemission spectroscopy. We show that there is substantial spectral weight
around Gamma and X, and lineshapes are intrinsically incoherent in the
paramagnetic state. The magnetic transition is characterized by a massive
spectral-weight transfer over an energy range as large as the band width, which
even exhibits a hysteresis loop that marks the strong first order transition.
Coherent quasiparticles emerge in the magnetically ordered state due to
decreased spin fluctuations, which account for the change of transport
properties from insulating behavior to metallic behavior. Our observation
demonstrates that Fe1.06Te distinguishes itself from other iron-based systems
with more local characters and much stronger interactions among different
degrees of freedom, and how a spin density wave is formed in the presence of
strong correlation.Comment: 5 pages, 4 figure
Superstructure-induced splitting of Dirac cones in silicene
Atomic scale engineering of two-dimensional materials could create devices
with rich physical and chemical properties. External periodic potentials can
enable the manipulation of the electronic band structures of materials. A
prototypical system is 3x3-silicene/Ag(111), which has substrate-induced
periodic modulations. Recent angle-resolved photoemission spectroscopy
measurements revealed six Dirac cone pairs at the Brillouin zone boundary of
Ag(111), but their origin remains unclear [Proc. Natl. Acad. Sci. USA 113,
14656 (2016)]. We used linear dichroism angle-resolved photoemission
spectroscopy, the tight-binding model, and first-principles calculations to
reveal that these Dirac cones mainly derive from the original cones at the K
(K') points of free-standing silicene. The Dirac cones of free-standing
silicene are split by external periodic potentials that originate from the
substrate-overlayer interaction. Our results not only confirm the origin of the
Dirac cones in the 3x3-silicene/Ag(111) system, but also provide a powerful
route to manipulate the electronic structures of two-dimensional materials.Comment: 6 pages, 3 figure
Nonlinear stochastic discrete drift-diffusion theory of charge fluctuations and domain relocation times in semiconductor superlattices
A stochastic discrete drift-diffusion model is proposed to account for the
effects of shot noise in weakly coupled, highly doped semiconductor
superlattices. Their current-voltage characteristics consist of a number stable
multistable branches corresponding to electric field profiles displaying two
domains separated by a domain wall. If the initial state corresponds to a
voltage on the middle of a stable branch and a sudden voltage is switched so
that the final voltage corresponds to the next branch, the domains relocate
after a certain delay time. Shot noise causes the distribution of delay times
to change from a Gaussian to a first passage time distribution as the final
voltage approaches that of the end of the first current branch. These results
agree qualitatively with experiments by Rogozia {\it et al} (Phys. Rev. B {\bf
64}, 041308(R) (2001)).Comment: 9 pages, 12 figures, 2 column forma
Electronic structure reconstruction: the driving force behind the magnetic and structural transitions in NaFeAs
The electronic structure of NaFeAs is studied with angle resolved
photoemission spectroscopy on high quality single crystals. Large portions of
the band structure start to shift around the structural transition temperature,
and smoothly evolve as the temperature lowers through the spin density wave
transition. Moreover, band folding due to magnetic order emerges around
structural transition. Our observation provides direct evidence that the
structural and magnetic transitions share the same origin, and are both driven
by the electronic structure reconstruction in Fe-based superconductors, instead
of Fermi surface nesting.Comment: 5 pages, 5 figure
Design and User Satisfaction of Interactive Maps for Visually Impaired People
Multimodal interactive maps are a solution for presenting spatial information
to visually impaired people. In this paper, we present an interactive
multimodal map prototype that is based on a tactile paper map, a multi-touch
screen and audio output. We first describe the different steps for designing an
interactive map: drawing and printing the tactile paper map, choice of
multi-touch technology, interaction technologies and the software architecture.
Then we describe the method used to assess user satisfaction. We provide data
showing that an interactive map - although based on a unique, elementary,
double tap interaction - has been met with a high level of user satisfaction.
Interestingly, satisfaction is independent of a user's age, previous visual
experience or Braille experience. This prototype will be used as a platform to
design advanced interactions for spatial learning
Periodicity Manifestations in the Turbulent Regime of Globally Coupled Map Lattice
We revisit the globally coupled map lattice (GCML). We show that in the so
called turbulent regime various periodic cluster attractor states are formed
even though the coupling between the maps are very small relative to the
non-linearity in the element maps.
Most outstanding is a maximally symmetric three cluster attractor in period
three motion (MSCA) due to the foliation of the period three window of the
element logistic maps. An analytic approach is proposed which explains
successfully the systematics of various periodicity manifestations in the
turbulent regime. The linear stability of the period three cluster attractors
is investigated.Comment: 34 pages, 8 Postscript figures, all in GCML-MSCA.Zi
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