Irregular orbits generate higher harmonics

The spectrum of higher harmonics in atoms calculated with a uniformized semiclassical propagator is presented and it is shown that higher harmonic generation is an interference phenomenon which can be described semiclassically. This can be concluded from the good agreement with the quantum spectrum. Moreover, the formation of a plateau in the spectrum is specifically due to the interference of irregular, time delayed, trajectories with regular orbits without a time-delay. This is proven by the absence of the plateau in an artificial semiclassical spectrum generated from a sample of trajectories from which the irregular trajectories (only a few percent) have been discarded

Semiclassical description of multiphoton processes

We analyze strong field atomic dynamics semiclassically, based on a full time-dependent description with the Hermann-Kluk propagator. From the properties of the exact classical trajectories, in particular the accumulation of action in time, the prominent features of above threshold ionization (ATI) and higher harmonic generation (HHG) are proven to be interference phenomena. They are reproduced quantitatively in the semiclassical approximation. Moreover, the behavior of the action of the classical trajectories supports the so called strong field approximation which has been devised and postulated for strong field dynamics.Comment: 10 pages, 11 figure

Shallow Dark Matter Cusps in Galaxy Clusters

We study the evolution of the stellar and dark matter components in a galaxy cluster of $10^{15} \, \rm{M_{\odot}}$ from $z=3$ to the present epoch using the high-resolution collisionless simulations of Ruszkowski & Springel (2009). At $z=3$ the dominant progenitor halos were populated with spherical model galaxies with and without accounting for adiabatic contraction. We apply a weighting scheme which allows us to change the relative amount of dark and stellar material assigned to each simulation particle in order to produce luminous properties which agree better with abundance matching arguments and observed bulge sizes at $z=3$. This permits the study of the effect of initial compactness on the evolution of the mass-size relation. We find that for more compact initial stellar distributions the size of the final Brightest Cluster Galaxy grows with mass according to $r\propto M^{2}$, whereas for more extended initial distributions, $r\propto M$. Our results show that collisionless mergers in a cosmological context can reduce the strength of inner dark matter cusps with changes in logarithmic slope of 0.3 to 0.5 at fixed radius. Shallow cusps such as those found recently in several strong lensing clusters thus do not necessarily conflict with CDM, but may rather reflect on the initial structure of the progenitor galaxies, which was shaped at high redshift by their formation process.Comment: 8 pages, 4 figures, submitted to MNRA

Evolution of the Red Sequence Giant to Dwarf Ratio in Galaxy Clusters out to z ~ 0.5

We analyze deep g' and r' band data of 97 galaxy clusters imaged with MegaCam on the Canada-France-Hawaii telescope. We compute the number of luminous (giant) and faint (dwarf) galaxies using criteria based on the definitions of de Lucia et al. (2007). Due to excellent image quality and uniformity of the data and analysis, we probe the giant-to-dwarf ratio (GDR) out to z ~ 0.55. With X-ray temperature (Tx) information for the majority of our clusters, we constrain, for the first time, the Tx-corrected giant and dwarf evolution separately. Our measurements support an evolving GDR over the redshift range 0.05 < z < 0.55. We show that modifying the (g'-r'), m_r' and K-correction used to define dwarf and giant selection do not alter the conclusion regarding the presence of evolution. We parameterize the GDR evolution using a linear function of redshift (GDR = alpha * z + beta) with a best fit slope of alpha = 0.88 +/- 0.15 and normalization beta = 0.44 +/- 0.03. Contrary to claims of a large intrinsic scatter, we find that the GDR data can be fully accounted for using observational errors alone. Consistently, we find no evidence for a correlation between GDR and cluster mass (via Tx or weak lensing). Lastly, the data suggest that the evolution of the GDR at z < 0.2 is driven primarily by dry merging of the massive giant galaxies, which when considered with previous results at higher redshift, suggests a change in the dominant mechanism that mediates the GDR.Comment: 20 pages, 15 figures. Accepted to MNRA

Semiclassical time--dependent propagation in three dimensions: How accurate is it for a Coulomb potential?

A unified semiclassical time propagator is used to calculate the semiclassical time-correlation function in three cartesian dimensions for a particle moving in an attractive Coulomb potential. It is demonstrated that under these conditions the singularity of the potential does not cause any difficulties and the Coulomb interaction can be treated as any other non-singular potential. Moreover, by virtue of our three-dimensional calculation, we can explain the discrepancies between previous semiclassical and quantum results obtained for the one-dimensional radial Coulomb problem.Comment: 8 pages, 4 figures (EPS

Galactic cannibalism and CDM density profiles

Using N-body simulations we show that the process of formation of the brightest cluster galaxy through dissipationless galactic cannibalism can affect the inner cluster dark matter density profile. In particular, we use as realistic test case the dynamical evolution of the galaxy cluster C0337-2522 at redshift z=0.59, hosting in its centre a group of five elliptical galaxies which are likely to be the progenitor of a central giant elliptical. After the formation of the brightest cluster galaxy, the inner cluster dark matter density profile is significantly flatter (logarithmic slope 0.49<beta<0.90) than the original cusp (beta=1), as a consequence of dynamical friction heating of the massive galaxies against the diffuse cluster dark matter. In our simulations we have assumed that the cluster galaxies are made of stars only. We also show that the presence of galactic dark matter haloes can steepen the cluster central density profile. We conclude that galactic cannibalism could be a viable physical mechanism to reconcile - at least at the cluster scale - the flat dark matter haloes inferred observationally in some galaxy clusters with the steep haloes predicted by cosmological simulations.Comment: 6 pages with 3 figures. Version accepted for publication in MNRAS. Longer than first version, with results from additional simulations. Conclusions unchange

Inelastic semiclassical Coulomb scattering

We present a semiclassical S-matrix study of inelastic collinear electron-hydrogen scattering. A simple way to extract all necessary information from the deflection function alone without having to compute the stability matrix is described. This includes the determination of the relevant Maslov indices. Results of singlet and triplet cross sections for excitation and ionization are reported. The different levels of approximation -- classical, semiclassical, and uniform semiclassical -- are compared among each other and to the full quantum result.Comment: 9 figure

Stars and dark matter in the spiral gravitational lens 2237+0305

We construct a mass model for the spiral lens galaxy 2237+0305, at redshift z_l=0.04, based on gravitational-lensing constraints, HI rotation, and new stellar-kinematic information, based on data taken with the ESI spectrograph on the 10m Keck-II Telescope. High resolution rotation curves and velocity dispersion profiles along two perpendicular directions, close to the major and minor axes of the lens galaxy, were obtained by fitting the Mgb-Fe absorption line region. The stellar rotation curve rises slowly and flattens at r~1.5" (~1.1 kpc). The velocity dispersion profile is approximately flat. A combination of photometric, kinematic and lensing information is used to construct a mass model for the four major mass components of the system -- the dark matter halo, disc, bulge, and bar. The best-fitting solution has a dark matter halo with a logarithmic inner density slope of gamma=0.9+/-0.3 for rho_DM propto r^-gamma, a bulge with M/L_B=6.6+/-0.3 Upsilon_odot, and a disc with M/L_B =1.2+/-0.3 Upsilon_odot, in agreement with measurements of late-type spirals. The bulge dominates support in the inner regions where the multiple images are located and is therefore tightly constrained by the observations. The disc is sub-maximal and contributes 45+/-11 per cent of the rotational support of the galaxy at 2.2r_d. The halo mass is (2.0+/-0.6) x 10^12 M_odot, and the stellar to virial mass ratio is 7.0+/-2.3 per cent, consistent with typical galaxies of the same mass.Comment: 14 pages, 6 figures, MNRAS, in pres

Avaliação da atividade antimicrobiana de extrato aquoso e etanólico de Acanthospermum australe.

As plantas medicinais têm sido amplamente empregadas na terapia de diversas patologias, constituindo parte das ferramentas terapêuticas utilizadas no controle das mais variadas moléstias humanas. A atividade antibacteriana dos extratos aquoso e etanólico de Acanthospermum australe (Loefl.) O. Kuntze foi avaliada frente às bactérias Staphylococcus aureus (ATCC 6538P) e Escherichia coli (ATCC 25922), pelo método de difusão em Agar. Foi observada a inibição de crescimento destes microrganismos por ambos os extratos, nas concentrações testadas. Paralelamente, foi realizada a análise fitoquímica dos extratos aquoso e hidroetanólico para a determinação de compostos fenólicos (taninos, flavonoides, ácidos fenólicos e antraquinonas), alcaloides e compostos terpênicos. Os extratos apresentaram perfis qualitativamente semelhantes, apresentando taninos, flavonoides, ácidos fenólicos e compostos terpênicos

Disentangling Baryons and Dark Matter in the Spiral Gravitational Lens B1933+503

Measuring the relative mass contributions of luminous and dark matter in spiral galaxies is important for understanding their formation and evolution. The combination of a galaxy rotation curve and strong lensing is a powerful way to break the disk-halo degeneracy that is inherent in each of the methods individually. We present an analysis of the 10-image radio spiral lens B1933+503 at z_l=0.755, incorporating (1) new global VLBI observations, (2) new adaptive-optics assisted K-band imaging, (3) new spectroscopic observations for the lens galaxy rotation curve and the source redshift. We construct a three-dimensionally axisymmetric mass distribution with 3 components: an exponential profile for the disk, a point mass for the bulge, and an NFW profile for the halo. The mass model is simultaneously fitted to the kinematics and the lensing data. The NFW halo needs to be oblate with a flattening of a/c=0.33^{+0.07}_{-0.05} to be consistent with the radio data. This suggests that baryons are effective at making the halos oblate near the center. The lensing and kinematics analysis probe the inner ~10 kpc of the galaxy, and we obtain a lower limit on the halo scale radius of 16 kpc (95% CI). The dark matter mass fraction inside a sphere with a radius of 2.2 disk scale lengths is f_{DM,2.2}=0.43^{+0.10}_{-0.09}. The contribution of the disk to the total circular velocity at 2.2 disk scale lengths is 0.76^{+0.05}_{-0.06}, suggesting that the disk is marginally submaximal. The stellar mass of the disk from our modeling is log_{10}(M_{*}/M_{sun}) = 11.06^{+0.09}_{-0.11} assuming that the cold gas contributes ~20% to the total disk mass. In comparison to the stellar masses estimated from stellar population synthesis models, the stellar initial mass function of Chabrier is preferred to that of Salpeter by a probability factor of 7.2.Comment: 16 pages, 13 figures, minor revisions based on referee's comments, accepted for publication in Ap