1,169 research outputs found
Topological delocalization of two-dimensional massless Dirac fermions
The beta function of a two-dimensional massless Dirac Hamiltonian subject to
a random scalar potential, which e.g., underlies the theoretical description of
graphene, is computed numerically. Although it belongs to, from a symmetry
standpoint, the two-dimensional symplectic class, the beta function
monotonically increases with decreasing . We also provide an argument based
on the spectral flows under twisting boundary conditions, which shows that none
of states of the massless Dirac Hamiltonian can be localized.Comment: 4 pages, 2 figure
Kinetic simulations of ladder climbing by electron plasma waves
The energy of plasma waves can be moved up and down the spectrum using
chirped modulations of plasma parameters, which can be driven by external
fields. Depending on whether the wave spectrum is discrete (bounded plasma) or
continuous (boundless plasma), this phenomenon is called ladder climbing (LC)
or autoresonant acceleration of plasmons. It was first proposed by Barth
\textit{et al.} [PRL \textbf{115}, 075001 (2015)] based on a linear fluid
model. In this paper, LC of electron plasma waves is investigated using fully
nonlinear Vlasov-Poisson simulations of collisionless bounded plasma. It is
shown that, in agreement with the basic theory, plasmons survive substantial
transformations of the spectrum and are destroyed only when their wave numbers
become large enough to trigger Landau damping. Since nonlinear effects decrease
the damping rate, LC is even more efficient when practiced on structures like
quasiperiodic Bernstein-Greene-Kruskal (BGK) waves rather than on Langmuir
waves \textit{per~se}
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An examination of the processes by which construal level affects the implicit evaluation of goal relevant stimuli.
Previous research has found that construal level—how abstractly or concretely people represent events—can impact implicit evaluations. Abstract high-level construal (vs. concrete low-level construal) promotes evaluative responses consistent with global (strongly held, long-term) rather than local (short-term, situational) goals. It remains unclear by what cognitive process(es) this occurs. In this paper, we examine two
possibilities. High-level construal might enhance the unintended influence of activated evaluative associations or facilitate the detection and implementation of intentional responses. To examine these possibilities, the current study applies a multinomial processing tree model to data from Fujita and Han (2009). Results suggest that high-level construal facilitates goal-consistent evaluations by increasing both the unintentional influence of activated goal-consistent positive associations and the intentional detection of and implementation of accurate responding to goal-relevant stimuli. These findings extend our understanding of how construal level promotes goal consistent
evaluations
Multi-Higgs Mass Spectrum in Gauge-Higgs Unification
We study an SU(2) supersymmetric gauge model in a framework of gauge-Higgs
unification. Multi-Higgs spectrum appears in the model at low energy. We
develop a useful perturbative approximation scheme for evaluating effective
potential to study the multi-Higgs mass spectrum. We find that both
tree-massless and massive Higgs scalars obtain mass corrections of similar size
from finite parts of the loop effects. The corrections modify multi-Higgs mass
spectrum, and hence, the loop effects are significant in view of future
verifications of the gauge-Higgs unification scenario in high-energy
experiments.Comment: 32 pages; typos corrected and a few comments added, published versio
Coating thermal noise of a finite-size cylindrical mirror
Thermal noise of a mirror is one of the limiting noise sources in the high
precision measurement such as gravitational-wave detection, and the modeling of
thermal noise has been developed and refined over a decade. In this paper, we
present a derivation of coating thermal noise of a finite-size cylindrical
mirror based on the fluctuation-dissipation theorem. The result agrees to a
previous result with an infinite-size mirror in the limit of large thickness,
and also agrees to an independent result based on the mode expansion with a
thin-mirror approximation. Our study will play an important role not only to
accurately estimate the thermal-noise level of gravitational-wave detectors but
also to help analyzing thermal noise in quantum-measurement experiments with
lighter mirrors.Comment: 13 pages, 4 figure
Quantum transport of massless Dirac fermions in graphene
Motivated by recent graphene transport experiments, we have undertaken a
numerical study of the conductivity of disordered two-dimensional massless
Dirac fermions.
Our results reveal distinct differences between the cases of short-range and
Coulomb randomly distributed scatterers.
We speculate that this behavior is related to the
Boltzmann transport theory prediction of dirty-limit behavior for Coulomb
scatterers.Comment: 4 pages, 1 figur
Two-color photoassociation spectroscopy of ytterbium atoms and the precise determinations of s-wave scattering lengths
By performing high-resolution two-color photoassociation spectroscopy, we
have successfully determined the binding energies of several of the last bound
states of the homonuclear dimers of six different isotopes of ytterbium. These
spectroscopic data are in excellent agreement with theoretical calculations
based on a simple model potential, which very precisely predicts the s-wave
scattering lengths of all 28 pairs of the seven stable isotopes. The s-wave
scattering lengths for collision of two atoms of the same isotopic species are
13.33(18) nm for ^{168}Yb, 3.38(11) nm for ^{170}Yb, -0.15(19) nm for ^{171}Yb,
-31.7(3.4) nm for ^{172}Yb, 10.55(11) nm for ^{173}Yb, 5.55(8) nm for ^{174}Yb,
and -1.28(23) nm for ^{176}Yb. The coefficient of the lead term of the
long-range van der Waals potential of the Yb_2 molecule is C_6=1932(30) atomic
units J nm^6).Comment: 9 pages, 7 figure
A clear separation of foraging areas between two neighboring colonies of Adelie Penguins observed in a year of extensive sea ice cover
The Tenth Symposium on Polar Science/Ordinary sessions : [OB] Polar Biology, Wed. 4 Dec. / Entrance Hall (1st floor) , National Institute of Polar Researc
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