How Do We See the Nuclear Region (r < 0.1 pc) of Narrow-Line Seyfert 1 Galaxies?

We propose two statistical tests to investigate how we see the nuclear region (r < 0.1 pc) of Narrow-Line Seyfert 1 galaxies (NLS1s). 1) The high-ionization nuclear emission-line region (HINER) test: Seyfert 1 galaxies (S1s) have systematically higher flux ratios of [Fe VII] lambda 6087 to [O III] lambda 5007 than Seyfert 2 galaxies (S2s). This is interpreted in that a significant part of the [Fe VII] lambda 6087 emission arises from the inner walls of dusty tori that cannot be seen in S2s (Murayama & Taniguchi 1998a,b). 2) The mid-infrared test: S1s have systematically higher flux ratios of the L band (3.5 micrometer) to the IRAS 25 micrometer band than S2s. This is also interpreted in that a significant part of the L band emission arises from the inner walls of dusty tori, because the tori are optically thick enough to absorb the L band emission if the tori are viewed nearly edge on (Murayama et al. 2000). Applying these tests to a sample of NLS1s, we have found that the NLS1s possibly have nearly the same properties as S1s.Comment: Contributed talk presented at the Joint MPE,AIP,ESO workshop on NLS1s, Bad Honnef, Dec. 1999, to appear in New Astronomy Reviews; also available at http://wave.xray.mpe.mpg.de/conferences/nls1-worksho

Slow-Roll Suppression of Adiabatic Instabilities in Coupled Scalar Field-Dark Matter Models

We study the evolution of linear density perturbations in the context of interacting scalar field-dark matter cosmologies, where the presence of the coupling acts as a stabilization mechanism for the runaway behavior of the scalar self-interaction potential as in the case of the Chameleon model. We show that in the "adiabatic" background regime of the system the rise of unstable growing modes of the perturbations is suppressed by the slow-roll dynamics of the field. Furthermore the coupled system behaves as an inhomogeneous adiabatic fluid. In contrast instabilities may develop for large values of the coupling constant, or along non-adiabatic solutions, characterized by a period of high-frequency dumped oscillations of the scalar field. In the latter case the dynamical instabilities of the field fluctuations, which are typical of oscillatory scalar field regimes, are amplified and transmitted by the coupling to dark matter perturbations.Comment: 6 pages, 3 figures; minor changes, corrected figure 2, added references, matches PRD published versio

Hydrogen bonding characterization in water and small molecules

The prototypical Hydrogen bond in water dimer and Hydrogen bonds in the protonated water dimer, in other small molecules, in water cyclic clusters, and in ice, covering a wide range of bond strengths, are theoretically investigated by first-principles calculations based on the Density Functional Theory, considering a standard Generalized Gradient Approximation functional but also, for the water dimer, hybrid and van-der-Waals corrected functionals. We compute structural, energetic, and electrostatic (induced molecular dipole moments) properties. In particular, Hydrogen bonds are characterized in terms of differential electron densities distributions and profiles, and of the shifts of the centres of Maximally localized Wannier Functions. The information from the latter quantities can be conveyed into a single geometric bonding parameter that appears to be correlated to the Mayer bond order parameter and can be taken as an estimate of the covalent contribution to the Hydrogen bond. By considering the cyclic water hexamer and the hexagonal phase of ice we also elucidate the importance of cooperative/anticooperative effects in Hydrogen-bonding formation.Comment: 11 figure

The innocuousness of adiabatic instabilities in coupled scalar field-dark matter models

Non-minimally coupled scalar field models suffer of unstable growing modes at the linear perturbation level. The nature of these instabilities depends on the dynamical state of the scalar field. In particular in systems which admit adiabatic solutions, large scale instabilities are suppressed by the slow-roll dynamics of the field. Here we review these results and present a preliminary likelihood data analysis suggesting that along adiabatic solutions coupled models with coupling of order of gravitational strength can provide viable cosmological scenarios satisfying constraints from SN Ia, CMB and large scale structure data.Comment: 6 pages, 4 figures; to be published in the AIP proceedings of the 'Invisible Universe International Conference', UNESCO-Paris, June 29-July 3, 200

Dijet Angular Distributions at the ATLAS Experiment

Dijet angular distributions from the first proton-proton collisions at 7 TeV have been measured with the ATLAS detector at the LHC. The dataset used corresponds to a total integrated luminosity of 61 $\pm$ 7 nb$^{-1}$. Comparing the distributions with Monte Carlo based QCD predictions shows good agreement between data and QCD. The distributions are used to set limits on the existence of quark compositeness.Comment: on behalf of the ATLAS Collaboration HCP 2010, Toront