119031869
Topological gravity, the hierarchy problem and axion physics
In the last years higher dimensional physics has won importance. Despite the Superstrings, higher dimensional effects, in measurable scales of energy (some TeV), became only possible with Randall-Sundrum's models (RS). In particular, recent studies in neutrino and axion physics have proposed new and interesting questions about neutrino mixings and new scales intermediating the Weak and Planck scales. In this work we discuss field theoretic models that in some aspects are similar to the RS models. Indeed, our models contain domain walls, solitonic-like objects that mimics the branes of the RS models. Applications are discussed ranging from topological field theories in higher dimensions until models containing D=5 space-time torsion in the RS scenario. In particular, we talk about subjects related to topological gravity, the hierarchy problem and axion physics. The topological terms studied are generalizations for $D>4$ of the axion-foton coupling in D=4. Such procedure involves naturally the Kalb-Ramond field. By dimensional reductions we obtain topological terms of the $B\wedge F$ type in D=4 Chern-Simons-like and $B\wedge\partial\phi$ type both in D=3.
118759367
Generalized axion-photon couplings and dual descriptions on brane-worlds
In this work we obtain topological and dual theories on brane-worlds in several dimensions. Our brane is a solitonic-like hypersurface embedded in a space-time with a specific dimensionality and it appears due to the breaking of a Peccei-Quinn-like symmetry. In the first part of this work, the obtained topological theories are related to a generalization of the axion-foton anomalous interaction in D=4 (in the Abelian case) and to the Wess-Zumino term (in the non-Abelian case). In the second part, we construct dual models on the brane through a mechanism of explicit Lorentz symmetry breaking. The gauge symmetries of such models are discussed within the Stuckelberg formalism.
120573076
FORM OF THE QUANTUM KINETIC-ENERGY OPERATOR WITH SPATIALLY VARYING EFFECTIVE MASS
18416827
Gauge hierarchy from a topological viewpoint
Abstract In this Letter we explore an alternative to the central point of the Randall–Sundrum brane world scenario, namely, the particular non-factorizable metric, in order to solve the hierarchy problem. From a topological viewpoint, we show that the exponential factor, crucial in the Randall–Sundrum model, appears in our approach, only due to the brane existence instead of a special metric background. Our results are based in a topological gravity theory via a non-standard interaction between scalar and non-Abelian degrees of freedom and in calculations about localized modes of matter fields on the brane. We point out that we obtain the same results of the Randall–Sundrum model using only one 3-brane, since a specific choice of a background metric is no longer required.
123618108
TOPOLOGICAL AND EQUIVALENT MODELS ON BRANE-WORLDS
In this work we obtain topological and equivalent theories on brane-worlds in several dimensions. Our brane is a solitonic-like hypersurface embedded in a spacetime with a specific dimensionality and it appears due to the breaking of a Peccei–Quinn-like symmetry. In the first part of this work, the obtained topological theories are related to a generalization of the axion–photon anomalous interaction in D = 4 (in the Abelian case) and to the Wess–Zumino term (in the non-Abelian case). In the second part, we construct equivalent models on the brane through a mechanism of explicit Lorentz symmetry breaking. The gauge symmetries of such models are discussed within the Stuckelberg formalism.
122883156
Gauge field localization on a dilatonic deformed brane
Abstract Membranes with internal structures presents several important characteristics in brane world scenarios. In this context we give new results in the study of localization of gauge vector fields in a very specific kink-like solution. We analyze, in particular, the coupling produced by the dilaton field in the space–time background. We find resonance structures in the KK spectrum revealing interesting behavior of coupling between massive states and matter localized in the membrane.
73697143
Spitzer Mid-IR Spectroscopy of Powerful 2?Jy and 3CRR Radio Galaxies. I. Evidence against a Strong Starburst-AGN Connection in Radio-loud AGN
We present deep Spitzer/Infrared Spectrograph (IRS) spectra for complete samples of 46 2 Jy radio galaxies (0.05 75%) than their more extended counterparts (≈15%-25%). We discuss this result in the context of a possible bias toward the selection of compact radio sources triggered in gas-rich environments.
118514386
The Mid-Infrared Emission of Seyfert Galaxies: A New Analysis of ISOCAM Data
We present mid-infrared data of a sample of 57 AGNs obtained with the instrument ISOCAM on board the Infrared Space Observatory (ISO) satellite. The images were obtained through the LW2 (6.75 μm) and LW7 (9.62 μm) filters. This is a new analysis of the Clavel et al. galaxy sample, which is divided into 26 type 1 (≤1.5) and 28 type 2 (>1.5) Seyfert galaxies, plus three QSOs. The spatial resolution of the images allows us to separate the nuclear and the extended contributions to the total emission after decomposing the brightness profiles into different morphological components. The most common components are a central point source (identified as the active nucleus) and an exponential disk. In some cases a bulge, a bar, or a ring are needed. The relative contribution of the nucleus to the total emission appears larger in Seyfert 1 than in Seyfert 2 types. This result confirms that both types of Seyfert galaxies are different in the mid-infrared wavelength range and supports the existence of a structure which produces anisotropic emission in this wavelength range. We have also explored correlations between the mid-infrared and the radio and X-ray wavelength ranges. The well-established radio/infrared correlation is maintained in our sample for the global emission of the galaxies. If only the nuclear infrared emission is considered, then a nonlinear correlation is apparent in the luminosity-luminosity scatter diagram. The ratio between the intrinsic hard X-ray and the nuclear mid-infrared emission presents large scatter and slightly larger values for type 2 Seyfert galaxies. These results seem to be consistent with the presence of a clumpy dusty torus surrounding the active nucleus.
14220887
The Narrow-Line Region of the Seyfert 2 Galaxy Mrk 78: An Infrared View
We report near-infrared spectroscopic data for the Seyfert 2 galaxy Mrk 78, taken with the LIRIS near-infrared camera/spectrometer at the William Herschel Telescope (WHT). The long-slit spectra clearly show extended emission. The resolution and depth of the near-infrared spectra allow the examination of its morphology and ionization regions, and a direct comparison with similarly deep visible spectra. The emission-line ratios obtained are used to derive the extinction toward the nucleus. The detection of strong features such as [Fe II], H2, hydrogen recombination lines, and the coronal [Si VI] λ1.962 line is used to study the kinematics and excitation mechanisms occurring in Mrk 78, revealing that despite the strong radio-jet interaction present in this object, photoionization from the active nucleus dominates the narrow-line region emission, while UV fluorescence is the source of the H2 emission. Lines with extended emission yield velocity distributions with an amplitude of about 600 km s-1, the consequence of an eastern lobe moving away from us plus a western lobe with the opposite contribution. We used the photoionization code CLOUDY to recreate a typical narrow-line region, to derive the ionization parameter, and to compare our spectral data with diagnostic diagrams.
85559795
The Nuclear Infrared Emission of Low-Luminosity AGN
We have obtained high-resolution mid-infrared (MIR) imaging, nuclear spectral energy distributions (SEDs) and archival Spitzer spectra for 22 low-luminosity active galactic nuclei (LLAGN; Lbol < 5 × 1042 erg s−1). Infrared (IR) observations may advance our understanding of the accretion ows in LLAGN, the fate of the obscuring torus at low accretion rates, and, perhaps, the star formation histories of these objects. However, while comprehensively studied in higher-luminosity Seyferts and quasars, the nuclear IR properties of LLAGN have not yet been well-determined. In these proceedings we summarise the results for the LLAGN at the relatively high-luminosity, high-Eddington ratio end of the sample. Strong, compact nuclear sources are visible in the MIR images of these objects, with luminosities consistent with or slightly in execss of that predicted by the standard MIR/X-ray relation. Their broadband nuclear SEDs are diverse; some resemble typical Seyfert nuclei, while others possess less of a well-defined MIR "dust bump". Strong silicate emission is present in many of these objects. We speculate that this, together with high ratios of silicate strength to hydrogen column density, could suggest optically thin dust and low dust-to-gas ratios, in accordance with model predictions that LLAGN do not host a Seyfert-like obscuring torus.