42,006 research outputs found
Soliton tunneling with sub-barrier kinetic energies
We investigate (theoretically and numerically) the dynamics of a soliton
moving in an asymmetrical potential well with a finite barrier. For large
values of the width of the well, the width of the barrier and/or the height of
the barrier, the soliton behaves classically. On the other hand, we obtain the
conditions for the existence of soliton tunneling with sub-barrier kinetic
energies. We apply these results to the study of soliton propagation in
disordered systems.Comment: 6 eps figures. To appear in Physical Review E (Rapid Communications
Spectral analysis of Markarian 421 and Markarian 501 with HAWC
The Hight Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory monitors the
gamma-ray sky in the energy range from 100 GeV to 100 TeV and has detected two
very high energy (VHE) blazars: Markarian 421 (Mrk 421) and Markarian 501 (Mrk
501) in 1.5 years of observations. In this work, we present the spectral
analysis above 1 TeV of both sources using a maximum likelihood method and an
artificial neural network as an energy estimator. The main objectives are to
constrain the spectral curvature of Mrk 421 and Mrk 501 at 5 TeV using
the EBL models from Gilmore et al. (2012) and Franceschini et al. (2008).Comment: Presented at the 35th International Cosmic Ray Conference (ICRC2017),
Bexco, Busan, Korea. See arXiv:1708.02572 for all HAWC contribution
Quasi Exactly Solvable NxN-Matrix Schroedinger Operators
New examples of matrix quasi exactly solvable Schroedinger operators are
constructed. One of them constitutes a matrix generalization of the quasi
exactly solvable anharmonic oscillator, the corresponding invariant vector
space is constructed explicitely. Also investigated are matrix generalizations
of the Lame equation.Comment: 16 latex pages, new results adde
Making Sustainable Agriculture Real in CAP 2020: The Role of Conservation Agriculture
Europe is about to redefine its Common Agriculture Policy (CAP) for the near future. The question is whether this redefinition is more a fine-tuning of the existing CAP or whether thorough changes can be expected. Looking back to the last revision of CAP the most notable change is, undoubtedly, the concern about EU and global food security. The revival of the interest in agricultural production already became evident during the Health Check as a consequence of climbing commodity prices in 2007/08. It is therefore no surprise that “rising concerns regarding both EU and global food security” is the first topic to appear in the list of justifications for the need for a CAP reform. Other challenges mentioned in this list such as sustainable management of natural resources, climate change and its mitigation, improvement of competitiveness to withstand globalization and rising price volatility, etc., while not new are considered worthwhile enough to be maintained and reappraised
Fast-to-Alfv\'en mode conversion mediated by Hall current. II Application to the solar atmosphere
Coupling between fast magneto-acoustic and Alfv\'en waves can be observe in
fully ionized plasmas mediated by stratification and 3D geometrical effects. In
Paper I, Cally & Khomenko (2015) have shown that in a weakly ionized plasma,
such as the solar photosphere and chromosphere, the Hall current introduces a
new coupling mechanism. The present study extends the results from Paper I to
the case of warm plasma. We report on numerical experiments where mode
transformation is studied using quasi-realistic stratification in thermodynamic
parameters resembling the solar atmosphere. This redresses the limitation of
the cold plasma approximation assumed in Paper I, in particular allowing the
complete process of coupling between fast and slow magneto-acoustic modes and
subsequent coupling of the fast mode to the Alfv\'en mode through the Hall
current. Our results confirm the efficacy of the mechanism proposed in Paper I
for the solar case. We observe that the efficiency of the transformation is a
sensitive function of the angle between the wave propagation direction and the
magnetic field, and of the wave frequency. The efficiency increases when the
field direction and the wave direction are aligned for increasing wave
frequencies. After scaling our results to typical solar values, the maximum
amplitude of the transformed Alfv\'en waves, for a frequency of 1 Hz,
corresponds to an energy flux (measured above the height of peak Hall coupling)
of , based on an amplitude of 500 at
, which is sufficient to play a major role in both quiet and active
region coronal heating
Marginal Fermi liquid behavior from 2d Coulomb interaction
A full, nonperturbative renormalization group analysis of interacting
electrons in a graphite layer is performed, in order to investigate the
deviations from Fermi liquid theory that have been observed in the experimental
measures of a linear quasiparticle decay rate in graphite. The electrons are
coupled through Coulomb interactions, which remain unscreened due to the
semimetallic character of the layer. We show that the model flows towards the
noninteracting fixed-point for the whole range of couplings, with logarithmic
corrections which signal the marginal character of the interaction separating
Fermi liquid and non-Fermi liquid regimes.Comment: 7 pages, 2 Postscript figure
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