17,766 research outputs found
Lost City meteorite: Its recovery and a comparison with other fireballs
Lost City meteoroid trajectory analysis and determination of original mas
Nonlinear Dirac equation solitary waves under a spinor force with different components
We consider the nonlinear Dirac (NLD) equation in 1+1 dimension with scalar-scalar selfinteraction
in the presence of external forces as well as damping of the form γͦf(x-t) - ιμγͦψ, where both f, {fj = rieiKjx} and ψ are two-component spinors. We develop an approximate variational
approach using collective coordinates (CC) for studying the time dependent response of the
solitary waves to these external forces. In our previous paper we assumed Kj = K, j = 1,2 which
allowed a transformation to a simplifying coordinate system, and we also assumed the "small" component
of the external force was zero. Here we include the effects of the small component and also
the case K1 ≠ K2 which dramatically modi es the behavior of the solitary wave in the presence of
these external forces.United States Department of EnergySanta Fe InstituteNational Natural Science Foundation of China (Nos. 11471025 and 11421101)Alexander von Humboldt Foundation (Germany) through Research Fellowship for Experienced Researchers SPA 1146358 STPMinisterio de Economía y Competitividad (Spain) through FIS2014-54497-PJunta de Andalucía (Spain) under Projects No. FQM207Excellent Grant P11-FQM-7276Mathematical Institute of the University of Seville (IMUS)Theoretical Division and Center for Nonlinear Studies at Los Alamos National LaboratoryPlan Propio of the University of Sevill
Photographic observations of 10 artificial meteors
Photographic observation of artificial meteo
Note on a new fundamental length scale instead of the Newtonian constant
The newly proposed entropic gravity suggests gravity as an emergent force
rather than a fundamental one. In this approach, the Newtonian constant
does not play a fundamental role any more, and a new fundamental constant is
required to replace its position. This request also arises from some
philosophical considerations to contemplate the physical foundations for the
unification of theories. We here consider the suggestion to derive from
more fundamental quantities in the presence of a new fundamental length scale
, which is suspected to originate from the structure of quantum space-time,
and can be measured directly from Lorentz-violating observations. Our results
are relevant to the fundamental understanding of physics, and more practically,
of natural units, as well as explanations of experimental constraints in
searching for Lorentz violation.Comment: 10 latex pages, final version for journal publicatio
Lost City meteorite - It's recovery and a comparison with other fireballs
Photographic and trajectory data for Lost City meteor and establishment of calibration of mass scale of other meteor
Stability of solitary waves in the nonlinear Dirac equation with arbitrary nonlinearity
We consider the nonlinear Dirac equation in 1+1 dimension with scalar-scalar
self interaction and with
mass . Using the exact analytic form for rest frame solitary waves of the
form for arbitrary , we discuss
the validity of various approaches to understanding stability that were
successful for the nonlinear Schr\"odinger equation. In particular we study the
validity of a version of Derrick's theorem, the criterion of Bogolubsky as well
as the Vakhitov-Kolokolov criterion, and find that these criteria yield
inconsistent results. Therefore, we study the stability by numerical
simulations using a recently developed 4th-order operator splitting integration
method. For different ranges of we map out the stability regimes in
. We find that all stable nonlinear Dirac solitary waves have a
one-hump profile, but not all one-hump waves are stable, while all waves with
two humps are unstable. We also find that the time , it takes for the
instability to set in, is an exponentially increasing function of and
decreases monotonically with increasing .Comment: 35 pages, 13 figure
The Effect of Transfer Printing on Pentacene Thin-Film Crystal Structure
The thermal deposition and transfer Printing method had been used to produce
pentacene thin-films on SiO2/Si and plastic substrates (PMMA and PVP),
respectively. X-ray diffraction patterns of pentacene thin films showed
reflections associated with highly ordered polycrystalline films and a
coexistence of two polymorph phases classified by their d-spacing, d(001): 14.4
and 15.4 A.The dependence of the c-axis correlation length and the phase
fraction on the film thickness and printing temperature were measured. A
transition from the 15.4 A phase towards 14.4 A phase was also observed with
increasing film thickness. An increase in the c-axis correlation length of
approximately 12% ~16% was observed for Pn films transfer printed onto a PMMA
coated PET substrate at 100~120 C as compared to as-grown Pn films on SiO2/Si
substrates. The transfer printing method is shown to be an attractive for the
fabrication of pentacene thin-film transistors on flexible substrates partly
because of the resulting improvement in the quality of the pentacene film.Comment: 5 pages, 5 figure
Rate-dependent morphology of Li2O2 growth in Li-O2 batteries
Compact solid discharge products enable energy storage devices with high
gravimetric and volumetric energy densities, but solid deposits on active
surfaces can disturb charge transport and induce mechanical stress. In this
Letter we develop a nanoscale continuum model for the growth of Li2O2 crystals
in lithium-oxygen batteries with organic electrolytes, based on a theory of
electrochemical non-equilibrium thermodynamics originally applied to Li-ion
batteries. As in the case of lithium insertion in phase-separating LiFePO4
nanoparticles, the theory predicts a transition from complex to uniform
morphologies of Li2O2 with increasing current. Discrete particle growth at low
discharge rates becomes suppressed at high rates, resulting in a film of
electronically insulating Li2O2 that limits cell performance. We predict that
the transition between these surface growth modes occurs at current densities
close to the exchange current density of the cathode reaction, consistent with
experimental observations.Comment: 8 pages, 6 fig
Decay of scalar variance in isotropic turbulence in a bounded domain
The decay of scalar variance in isotropic turbulence in a bounded domain is
investigated. Extending the study of Touil, Bertoglio and Shao (2002; Journal
of Turbulence, 03, 49) to the case of a passive scalar, the effect of the
finite size of the domain on the lengthscales of turbulent eddies and scalar
structures is studied by truncating the infrared range of the wavenumber
spectra. Analytical arguments based on a simple model for the spectral
distributions show that the decay exponent for the variance of scalar
fluctuations is proportional to the ratio of the Kolmogorov constant to the
Corrsin-Obukhov constant. This result is verified by closure calculations in
which the Corrsin-Obukhov constant is artificially varied. Large-eddy
simulations provide support to the results and give an estimation of the value
of the decay exponent and of the scalar to velocity time scale ratio
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