313 research outputs found
Relativistic spherical plasma waves
Tightly focused laser pulses as they diverge or converge in underdense plasma
can generate wake waves, having local structures that are spherical waves. Here
we report on theoretical study of relativistic spherical wake waves and their
properties, including wave breaking. These waves may be suitable as particle
injectors or as flying mirrors that both reflect and focus radiation, enabling
unique X-ray sources and nonlinear QED phenomena.Comment: 6 pages; 4 figure
Random data Cauchy theory for supercritical wave equations II : A global existence result
We prove that the subquartic wave equation on the three dimensional ball
, with Dirichlet boundary conditions admits global strong solutions for
a large set of random supercritical initial data in .
We obtain this result as a consequence of a general random data Cauchy theory
for supercritical wave equations developed in our previous work \cite{BT2} and
invariant measure considerations which allow us to obtain also precise large
time dynamical informations on our solutions
Atomic and electronic structure of a copper/graphene interface as prepared and 1.5 years after
We report the results of X-ray spectroscopy and Raman measurements of
as-prepared graphene on a high quality copper surface and the same materials
after 1.5 years under different conditions (ambient and low humidity). The
obtained results were compared with density functional theory calculations of
the formation energies and electronic structures of various structural defects
in graphene/Cu interfaces. For evaluation of the stability of the carbon cover,
we propose a two-step model. The first step is oxidation of the graphene, and
the second is perforation of graphene with the removal of carbon atoms as part
of the carbon dioxide molecule. Results of the modeling and experimental
measurements provide evidence that graphene grown on high-quality copper
substrate becomes robust and stable in time (1.5 years). However, the stability
of this interface depends on the quality of the graphene and the number of
native defects in the graphene and substrate. The effect of the presence of a
metallic substrate with defects on the stability and electronic structure of
graphene is also discussed.Comment: 18 pages, 6 figures, accepted to Appl. Surf. Sc
Behavior of a Model Dynamical System with Applications to Weak Turbulence
We experimentally explore solutions to a model Hamiltonian dynamical system
derived in Colliander et al., 2012, to study frequency cascades in the cubic
defocusing nonlinear Schr\"odinger equation on the torus. Our results include a
statistical analysis of the evolution of data with localized amplitudes and
random phases, which supports the conjecture that energy cascades are a generic
phenomenon. We also identify stationary solutions, periodic solutions in an
associated problem and find experimental evidence of hyperbolic behavior. Many
of our results rely upon reframing the dynamical system using a hydrodynamic
formulation.Comment: 22 pages, 14 figure
Topological Coherent Modes for Nonlinear Schr\"odinger Equation
Nonlinear Schr\"odinger equation, complemented by a confining potential,
possesses a discrete set of stationary solutions. These are called coherent
modes, since the nonlinear Schr\"odinger equation describes coherent states.
Such modes are also named topological because the solutions corresponding to
different spectral levels have principally different spatial dependences. The
theory of resonant excitation of these topological coherent modes is presented.
The method of multiscale averaging is employed in deriving the evolution
equations for resonant guiding centers. A rigorous qualitative analysis for
these nonlinear differential equations is given. Temporal behaviour of
fractional populations is illustrated by numerical solutions.Comment: 14 pages, Latex, no figure
On the design of experiments to study extreme field limits
We propose experiments on the collision of high intensity electromagnetic
pulses with electron bunches and on the collision of multiple electromagnetic
pulses for studying extreme field limits in the nonlinear interaction of
electromagnetic waves. The effects of nonlinear QED will be revealed in these
laser plasma experiments.Comment: 7 pages, 3 figures, 1 table; 15th Advanced Accelerator Concepts
Workshop (AAC 2012), Austin, Texas, 10-15 June, 201
High-Energy and High-Power-Density Potassium Ion Batteries Using Dihydrophenazine-Based Polymer as Active Cathode Material
Polymeric aromatic amines were shown to be very promising cathodes for lithium-ion batteries. Surprisingly, these materials are scarcely used for designing post-lithium batteries. In this Letter, we investigate the application of the high-voltage poly(N-phenyl-5,10-dihydrophenazine) (p-DPPZ) cathodes for K-ion batteries. The designed batteries demonstrate an impressive specific capacity of 162 mAh g-1 at the current density of 200 mA g-1, operate efficiently at high current densities of 2-10 A g-1, enabling charge and discharge within ∼1-4 min, and deliver the specific capacity of 125-145 mAh g-1 with a retention of 96 and 79% after 100 and 1000 charge-discharge cycles, respectively. Finally, these K-ion batteries with polymeric p-DPPZ cathodes showed rather outstanding specific power of >3 × 104 W kg-1, thus paving a way to the design of ultrafast and durable high-capacity metal-ion batteries matching the increasing demand for high power and high energy density electrochemical energy storage devices. © 2019 American Chemical Society.Government Council on Grants, Russian Federation: 02.Russian Science Foundation, RSF: 16-13-00111This work was supported by Russian Science Foundation, project 16-13-00111. We acknowledge the support of Dr. A. Mumyatov with FTIR spectroscopy measurements. The XPS measurements were supported by the Government of Russian Federation (Act 211, Agreement No. 02.A03.21.0006) and Theme “Electron” (no. AAAA-A18-118020190098-5)
Resonant Generation of Topological Modes in Trapped Bose Gases
Trapped Bose atoms cooled down to temperatures below the Bose-Einstein
condensation temperature are considered. Stationary solutions to the
Gross-Pitaevskii equation (GPE) define the topological coherent modes,
representing nonground-state Bose-Einstein condensates. These modes can be
generated by means of alternating fields whose frequencies are in resonance
with the transition frequencies between two collective energy levels
corresponding to two different topological modes. The theory of resonant
generation of these modes is generalized in several aspects: Multiple-mode
formation is described; a shape-conservation criterion is derived, imposing
restrictions on the admissible spatial dependence of resonant fields; evolution
equations for the case of three coherent modes are investigated; the complete
stability analysis is accomplished; the effects of harmonic generation and
parametric conversion for the topological coherent modes are predicted. All
considerations are realized both by employing approximate analytical methods as
well as by numerically solving the GPE. Numerical solutions confirm all
conclusions following from analytical methods.Comment: One reference modifie
Properties of electrons scattered on a strong plane electromagnetic wave with a linear polarization: classical treatment
The relations among the components of the exit momenta of ultrarelativistic
electrons scattered on a strong electromagnetic wave of a low (optical)
frequency and linear polarization are established using the exact solutions to
the equations of motion with radiation reaction included (the Landau-Lifshitz
equation). It is found that the momentum components of the electrons traversed
the electromagnetic wave depend weakly on the initial values of the momenta.
These electrons are mostly scattered at the small angles to the direction of
propagation of the electromagnetic wave. The maximum Lorentz factor of the
electrons crossed the electromagnetic wave is proportional to the work done by
the electromagnetic field and is independent of the initial momenta. The
momentum component parallel to the electric field strength vector of the
electromagnetic wave is determined only by the diameter of the laser beam
measured in the units of the classical electron radius. As for the reflected
electrons, they for the most part lose the energy, but remain relativistic.
There is a reflection law for these electrons that relates the incident and the
reflection angles and is independent of any parameters.Comment: 12 pp, 3 fig
Test determinations of paleointensity in historical lavas of Kamchatka
© 2017, Pleiades Publishing, Ltd.The reliability of the Thellier method for determining the paleointensity of a geomagnetic field is explored on recent igneous rocks of Kamchatka. The main magnetic mineral in the studied rocks is titanomagnetite with different degree of oxidation. It is obtained that the reliability of the results can be assessed based on the deviations of the check points of the partial thermoremanent magnetization (pTRM) during the Thellier experiment. Besides, for different rocks, it is found that the stability of titanomagnetites to heating during the experiments can be insufficient for validating the reliability of the results of paleointensity determination; however, at the same time, the reliability may depend on the initial (oxidation) state of the magnetic minerals of the studied rocks
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