8,162 research outputs found
Enhanced graphene nonlinear response through geometrical plasmon focusing
We propose a simple approach to couple light into graphene plasmons and focus these excitations at
focal spots of a size determined by the plasmon wavelength, thus producing high optical field
enhancement that boosts the nonlinear response of the material. More precisely, we consider a
graphene structure in which incident light is coupled to its plasmons at the carbon edges and
subsequently focused on a spot of size comparable to the plasmon wavelength. We observe large
confinement of graphene plasmons, materializing in small, intense focal spots, in which the
extraordinary nonlinear response of this material leads to relatively intense harmonic generation.
This result shows the potential of plasmon focusing in suitably edged graphene structures to produce
large field confinement and nonlinear response without involving elaborated nanostructuring.Peer ReviewedPostprint (published version
Measure of the size of CP violation in extended models
In this letter we introduce a possible measure of the size of CP violation in
the Standard Model and its extensions, based on quantities invariant under the
change of weak quark basis. We also introduce a measure of the ``average size''
of CP violation in a model, which can be used to compare the size of CP
violation in models involving extra sequential or vector-like quarks, or
left-right symmetry.Comment: LaTeX, 7 pages, no figure
Interference and complementarity for two-photon hybrid entangled states
In this work we generate two-photon hybrid entangled states (HES), where the
polarization of one photon is entangled with the transverse spatial degree of
freedom of the second photon. The photon pair is created by parametric
down-conversion in a polarization-entangled state. A birefringent double-slit
couples the polarization and spatial degrees of freedom of these photons and
finally, suitable spatial and polarization projections generate the HES. We
investigate some interesting aspects of the two-photon hybrid interference, and
present this study in the context of the complementarity relation that exists
between the visibilities of the one- and two-photon interference patterns.Comment: 10 pages, 4 figures. Accepted in Physical Review
Efecto de la composición del gas de refinería sobre las características del proceso de combustión
En este artículo de investigación científica se analiza el efecto del cambio de la composición del gas combustible (Gas de Refinería (GR) por Gas Natural (GN)) sobre las características del proceso combustión en hornos de la industria de refinación del petróleo; se evaluó el poder calorífico, el índice de Wobbe (IW) y exceso de oxígeno, para mezclas combustibles de composición variable. Mediante simulación computacional del proceso de combustión se calculó la temperatura adiabática de lama, eficiencia y la composición de los productos de combustión. Se evaluaron mezclas de gases combustibles con poderes caloríficos entre 800-2500 Btu/pie3 y se compararon con la combustión de gas natural. Se registró variabilidad en la temperatura adiabática y la eficiencia en función de la composición del gas y el exceso de oxígeno, lo que genera inestabilidad en el horno y mayor impacto ambiental
Quantum process reconstruction based on mutually unbiased basis
We study a quantum process reconstruction based on the use of mutually
unbiased projectors (MUB-projectors) as input states for a D-dimensional
quantum system, with D being a power of a prime number. This approach connects
the results of quantum-state tomography using mutually unbiased bases (MUB)
with the coefficients of a quantum process, expanded in terms of
MUB-projectors. We also study the performance of the reconstruction scheme
against random errors when measuring probabilities at the MUB-projectors.Comment: 6 pages, 1 figur
Pinning down top dipole moments with ultra-boosted tops
We investigate existing and future hadron-collider constraints on the top
dipole chromomagnetic and chromoelectric moments, two quantities that are
expected to be modified in the presence of new physics. We focus first on
recent measurements of the inclusive top pair production cross section at the
Tevatron and at the Large Hadron Collider. We then analyse the role of
top-antitop events produced at very large invariant masses, in the context of
the forthcoming 13-14 TeV runs of the LHC, and at a future 100 TeV
proton-proton collider. In this latter case, the selection of semileptonic
decays to hard muons allows to tag top quarks boosted to the multi-TeV regime,
strongly reducing the QCD backgrounds and leading to a significant improvement
in the sensitivity to anomalous top couplings.Comment: LaTeX 8 pages, 7 figures. Enlarged version to appear in PR
Warps and correlations with intrinsic parameters of galaxies in the visible and radio
From a comparison of the different parameters of warped galaxies in the
radio, and especially in the visible, we find that: a) No large galaxy (large
mass or radius) has been found to have high amplitude in the warp, and there is
no correlation of size/mass with the degree of asymmetry of the warp. b) The
disc density and the ratio of dark to luminous mass show an opposing trend:
smaller values give more asymmetric warps in the inner radii (optical warps)
but show no correlation with the amplitude of the warp; however, in the
external radii neither is there any correlation with the asymmetry. c) A third
anticorrelation arises from a comparison of the amplitude and degree of
asymmetry in the warped galaxies. Hence, it seems that very massive dark matter
haloes have nothing to do with the formation of warps but only with the degree
of symmetry in the inner radii, and are unrelated to the warp shape for the
outermost radii. Denser discs show up the same dependence.Comment: 13 pages, 2 figures, accepted to be published in A&
Hypothalamic Integration of Metabolic, Endocrine, and Circadian Signals in Fish: Involvement in the Control of Food Intake
The regulation of food intake in fish is a complex process carried out through several different mechanisms in the central nervous system (CNS) with hypothalamus being the main regulatory center. As in mammals, a complex hypothalamic circuit including two populations of neurons: one co-expressing neuropeptide Y (NPY) and Agouti-related peptide (AgRP) and the second one population co-expressing pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) is involved in the integration of information relating to food intake control. The production and release of these peptides control food intake, and the production results from the integration of information of different nature such as levels of nutrients and hormones as well as circadian signals. The present review summarizes the knowledge and recent findings about the presence and functioning of these mechanisms in fish and their differences vs. the known mammalian model
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