52,234 research outputs found
Geometrical resonance in spatiotemporal systems
We generalize the concept of geometrical resonance to perturbed sine-Gordon,
Nonlinear Schrödinger and Complex Ginzburg-Landau equations. Using this
theory we can control different dynamical patterns. For instance, we can
stabilize breathers and oscillatory patterns of large amplitudes successfully
avoiding chaos. On the other hand, this method can be used to suppress
spatiotemporal chaos and turbulence in systems where these phenomena are
already present. This method can be generalized to even more general
spatiotemporal systems.Comment: 2 .epl files. Accepted for publication in Europhysics Letter
Interplay of Coulomb and electron-phonon interactions in graphene
We consider mutual effect of the electron-phonon and strong Coulomb
interactions on each other by summing up leading logarithmic corrections via
the renormalization group approach. We find that the Coulomb interaction
enhances electron coupling to the intervalley A1 optical phonons, but not to
the intravalley E2 phonons
X-ray/gamma-ray flux correlations in the BL Lacs Mrk 421 and 501 using HAWC data
The HAWC gamma ray observatory is located at the Sierra Negra Volcano in
Puebla, Mexico, at an altitude of 4,100 meters. HAWC is a wide field of view
array of 300 water Cherenkov detectors that are continuously surveying ~ 2sr of
the sky, operating since March 2015. The large collected data sample allows
HAWC to perform an unbiased monitoring of the BL Lac Mrk 421. This is the
closest and brightest known extragalactic high-synchrotron-peaked BL Lac in the
gamma-ray/X- ray bands and is extensively monitored by the Large Area Telescope
(LAT) on-board the Fermi satellite, and the BAT and XRT instruments of the
Swift satellite. In this work, we use 25 months of HAWC data together with
Swift-XRT data to characterize potential correlations between both wavelengths.
This analysis shows that HAWC and Swift-XRT data are correlated even stronger
than expected for quasi-simultaneous observations.Comment: Presented at the 35th International Cosmic Ray Conference (ICRC2017),
Bexco, Busan, Korea. See arXiv:1708.02572 for all HAWC contribution
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
Cooper-pair propagation and superconducting correlations in graphene
We investigate the Cooper-pair propagation and the proximity effect in
graphene under conditions in which the distance L between superconducting
electrodes is much larger than the width W of the contacts. In the case of
undoped graphene, supercurrents may exist with a spatial decay proportional to
W^2/L^3. This changes upon doping into a 1/L^2 behavior, opening the
possibility to observe a supercurrent over length scales above 1 micron at
suitable doping levels. We also show that there is in general a crossover
temperature T ~ v_F/k_B L that marks the onset of the strong decay of the
supercurrent, and that corresponds to the scale below which the Cooper pairs
are not disrupted by thermal effects during their propagation.Comment: 5 pages, 2 figures; corrected discussio
Confinement of electrons in layered metals
We analyze the out of plane hopping in models of layered systems where the
in--plane properties deviate from Landau's theory of a Fermi liquid. We show
that the hopping term acquires a non trivial energy dependence, due to the
coupling to in plane excitations, and can be either relevant or irrelevant at
low energies or temperatures. The latter is always the case if the Fermi level
lies close to a saddle point in the dispersion relation.Comment: 4 pages, 1 eps figur
Coherent states on the circle
We present a possible construction of coherent states on the unit circle as
configuration space. In our approach the phase space is the product Z x S^1.
Because of the duality of canonical coordinates and momenta, i.e. the angular
variable and the integers, this formulation can also be interpreted as coherent
states over an infinite periodic chain. For the construction we use the analogy
with our quantization over a finite periodic chain where the phase space was
Z_M x Z_M. Properties of the coherent states constructed in this way are
studied and the coherent states are shown to satisfy the resolution of unity.Comment: 7 pages, presented at GROUP28 - "28th International Colloquium on
Group Theoretical Methods in Physics", Newcastle upon Tyne, July 2010.
Accepted in Journal of Physics Conference Serie
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
Non-Markovian Quantum Optics with Three-Dimensional State-Dependent Optical Lattices
Quantum emitters coupled to structured photonic reservoirs experience
unconventional individual and collective dynamics emerging from the interplay
between dimensionality and non-trivial photon energy dispersions. In this work,
we systematically study several paradigmatic three dimensional structured baths
with qualitative differences in their bath spectral density. We discover
non-Markovian individual and collective effects absent in simplified
descriptions, such as perfect subradiant states or long-range anisotropic
interactions. Furthermore, we show how to implement these models using only
cold atoms in state-dependent optical lattices and show how this unconventional
dynamics can be observed with these systems.Comment: 39 pages, 17 figures. Accepted versio
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