Search results for " P.A.E.S."
showing 10 items of 309 documents
A New Look at Spitzer Primary Transit Observations of the Exoplanet HD 189733b
2014
Blind source separation techniques are used to reanalyse two exoplanetary transit lightcurves of the exoplanet HD189733b recorded with the IR camera IRAC on board the Spitzer Space Telescope at 3.6$\mu$m during the "cold" era. These observations, together with observations at other IR wavelengths, are crucial to characterise the atmosphere of the planet HD189733b. Previous analyses of the same datasets reported discrepant results, hence the necessity of the reanalyses. The method we used here is based on the Independent Component Analysis (ICA) statistical technique, which ensures a high degree of objectivity. The use of ICA to detrend single photometric observations in a self-consistent wa…
Diffractive optics for processing ultrashort light pulses
2011
In this work we combine, in principle, two disjoint optical fields, diffractive optics and ultrashort light radiation. This combination allows us to manipulate in a very unconventional manner femtosecond pulses and, on the other hand, to implement a set of novel applications. In our case we have focused our attention on material processing and biophotonics applications.
Analytical Evaluation of the Temporal Focal Shift for Arbitrary Pulse Shapes
2004
In this letter, we analyze the propagation of linearly chirped arbitrary-shaped light pulses through a parabolic dispersive medium to derive an analytical formula of assessing the location of the transverse plane where the pulse root-mean-square width is minimum. Closed form expressions for compressed pulses, which are independent of the input pulse shape, are demonstrated. In this way, we demonstrate that both the relative temporal focal shift and the minimum pulsewidth are solely determined by two factors, the temporal equivalent of the Fresnel number of the geometry and the pulse quality factor, i.e., the temporal analogue of the spatial M/sup 2/ beam quality factor. Some examples are di…
Regularized Euler-alpha motion of an infinite array of vortex sheets
2016
We consider the Euler- $$\alpha $$ regularization of the Birkhoff–Rott equation and compare its solutions with the dynamics of the non regularized vortex-sheet. For a flow induced by an infinite array of planar vortex-sheets we analyze the complex singularities of the solutions.Through the singularity tracking method we show that the regularized solution has several complex singularities that approach the real axis. We relate their presence to the formation of two high-curvature points in the vortex sheet during the roll-up phenomenon.
On the Physical Propagators of QED
1993
The true variables in QED are the transverse photon components and Dirac's physical electron, constructed out of the fermionic field and the longitudinal components of the photon. We calculate the propagators in terms of these variables to one loop and demonstrate their gauge invariance. The physical electron propagator is shown not to suffer from infrared divergences in any gauge. In general, all physical Green's functions are gauge invariant and infrared-finite.
Configurational entropy of microemulsions : The fundamental length scale
1993
Phenomenological models have been quite successful in characterizing both the various complex phases and the corresponding phase diagrams of microemulsions. In some approaches, e.g., the random mixing model (RMM), the lattice parameter is of the order of the dimension of an oil or water domain and has been used as a length scale for computing a configurational entropy, the so‐called entropy of mixing, of the microemulsion. In the central and material section of this paper (Sec. III), we show that the fundamental length scale for the calculation of the entropy of mixing is of the order of the cube root of the volume per molecule—orders of magnitude smaller than the dimension of such a domain…
Effect of coronal loop structure on wave heating through phase mixing
2020
Context. The mechanism(s) behind coronal heating still elude(s) direct observation and modelling of viable theoretical processes and the subsequent effect on coronal structures is one of the key tools available to assess possible heating mechanisms. Wave heating via the phase mixing of magnetohydrodynamic (MHD) transverse waves has been proposed as a possible way to convert magnetic energy into thermal energy, but MHD models increasingly suggest this is not an efficient enough mechanism. Aims. We modelled heating by phase mixing transverse MHD waves in various configurations in order to investigate whether certain circumstances can enhance the heating sufficiently to sustain the million deg…
Chiral unitary approach to hadron spectroscopy
2002
The s-wave meson-baryon interaction in the $S = -1$, $S= 0$ and $S= -2$ sectors is studied by means of coupled channels, using the lowest-order chiral Lagrangian and the N/D method or equivalently the Bethe-Salpeter equation to implement unitarity. This chiral approach leads to the dynamical generation of the $\Lambda (1405)$, $\Lambda(1670)$ and $\Sigma(1620)$ states for $S = -1$, the $N^*(1535)$ for $S= 0$ and the $\Xi(1620)$ for $S= -2$. We look for poles in the complex plane and extract the couplings of the resonances to the different final states. This allows identifying the $\Lambda (1405)$ and the $\Lambda(1670)$ resonances with $\bar{K}N$ and $K\Xi$ quasibound states, respectively. …
Phenomenological consequences of the seesaw mechanism in S-4 based models
2009
Reference [1] proposed a flavor model based on the symmetry group S-4, managing to describe fermion masses and mixings. The Weinberg operator has been used in order to provide the smallness of the neutrino masses, while a set of scalar fields, getting nonvanishing vacuum expectation values, spontaneously breaks down S-4 and provides the tri-bimaximal pattern as the lepton mixing matrix. Restricting to this setting, in this paper we analyze possible origins for the effective terms: the type I seesaw mechanism is the best known approach, but type II and III are also discussed. The phenomenology related to these models is various and future experiments could in principle discriminate among the…
Leptonicμandτdecays: Mass effects, polarization effects, andO(α)radiative corrections
2003
We calculate the radiative corrections to the unpolarized and the four polarized spectrum and rate functions in the leptonic decay of a polarizedinto a polarized electron. The new feature of our calculation is that we keep the mass of the final state electron finite which is mandatory if one wants to investigate the threshold region of the decay. Analytical results are given for the energy spectrum and the polar angle distribution of the final state electron whose longitudinal and transverse polarization is calculated. We also provide analytical results on the integrated spec- trum functions. We analyze the me → 0 limit of our general results and investigate the quality of the me → 0 approx…