Debt management in Brazil : evaluation of the Real Plan and challenges ahead

Brazil's domestic debt has posed two challenges to policymakers: it has grown very fast and, despite progress, remains extremely short in maturity. The authors analyze Brazil's experience with domestic public debt management, searching for policy prescriptions for the next few years. After briefly reviewing the recent history of the country's domestic debt, they decompose the large rise in federal bonded debt in 1995-98, searching for its macroeconomic causes. The main explanations: extremely high interest payments (caused by Brazil's weak fiscal stance and quasi-fixed exchange rate regime) and the accumulation of assets (especially obligations of Brazil's states). Simulations of the net debt path for the near future underscore the importance of a tighter fiscal stance to prevent the debt-to-GDP ratio from growing further. The authors'main policy advice is to foster and rely more on inflation-linked bonds--the least harmful way to lengthen debt maturity.Economic Theory&Research,Banks&Banking Reform,Public Sector Economics&Finance,Payment Systems&Infrastructure,Strategic Debt Management,Economic Theory&Research,Banks&Banking Reform,Strategic Debt Management,Public Sector Economics&Finance,Municipal Financial Management

A new signature for color octet pseudoscalars at the LHC

Color octet (pseudo)scalars, if they exist, will be copiously produced at the CERN Large Hadron Collider (LHC). However, their detection can become a very challenging task. In particular, if their decay into a pair of top quarks is kinematically forbidden, the main decay channel would be into two jets, with a very large background. In this Brief Report we explore the possibility of using anomaly-induced decays of the color octet pseudoscalars into gauge bosons to find them at the LHC.Comment: 4 pages, 2 figures. New references adde

Evidence for a chemically differentiated outflow in Mrk 231

Aims: Our goal is to study the chemical composition of the outflows of active galactic nuclei and starburst galaxies. Methods: We obtained high-resolution interferometric observations of HCN and HCO$^+$ $J=1\rightarrow0$ and $J=2\rightarrow1$ of the ultraluminous infrared galaxy Mrk~231 with the IRAM Plateau de Bure Interferometer. We also use previously published observations of HCN and HCO$^+$ $J=1\rightarrow0$ and $J=3\rightarrow2$, and HNC $J=1\rightarrow0$ in the same source. Results: In the line wings of the HCN, HCO$^+$, and HNC emission, we find that these three molecular species exhibit features at distinct velocities which differ between the species. The features are not consistent with emission lines of other molecular species. Through radiative transfer modelling of the HCN and HCO$^+$ outflow emission we find an average abundance ratio $X(\mathrm{HCN})/X(\mathrm{HCO}^+)\gtrsim1000$. Assuming a clumpy outflow, modelling of the HCN and HCO$^+$ emission produces strongly inconsistent outflow masses. Conclusions: Both the anti-correlated outflow features of HCN and HCO$^+$ and the different outflow masses calculated from the radiative transfer models of the HCN and HCO$^+$ emission suggest that the outflow is chemically differentiated. The separation between HCN and HCO$^+$ could be an indicator of shock fronts present in the outflow, since the HCN/HCO$^+$ ratio is expected to be elevated in shocked regions. Our result shows that studies of the chemistry in large-scale galactic outflows can be used to better understand the physical properties of these outflows and their effects on the interstellar medium (ISM) in the galaxy.Comment: 12 pages, 8 figures, accepted for publication in A&

Molecular gas in the northern nucleus of Mrk273: Physical and chemical properties of the disk and its outflow

Aiming to characterise the properties of the molecular gas in the ultraluminous infrared galaxy Mrk273 and its outflow, we used the NOEMA interferometer to image the dense gas molecular tracers HCN, HCO+, HNC, HOC+ and HC3N at 86GHz and 256GHz with angular resolutions of 4.9x4.5 arcsec (3.7x3.4 kpc) and 0.61x0.55 arcsec (460x420 pc). We also modelled the flux of several H2O lines observed with Herschel using a radiative transfer code that includes excitation by collisions as well as by far-infrared photons. The disk of the Mrk273 north nucleus has two components with decoupled kinematics. The gas in the outer parts (1.5 kpc) rotates with a south-east to north-west direction, while in the inner disk (300 pc) follows a north-east to south-west rotation. The central 300 pc, which hosts a compact starburst region, is filled with dense and warm gas, contains a dynamical mass of (4-5)x10^9M_sun, a luminosity of L'_HCN=(3-4)x10^8 K km/s pc^2, and a dust temperature of 55 K. At the very centre, a compact core with R~50 pc has a luminosity of L_IR=4x10^11L_sun (30% of the total infrared luminosity), and a dust temperature of 95 K. The core is expanding at low velocities ~50-100 km/s, probably affected by the outflowing gas. We detect the blue-shifted component of the outflow, while the red-shifted counterpart remains undetected in our data. Its cold and dense phase reaches fast velocities up to ~1000 km/s, while the warm outflowing gas has more moderate maximum velocities of ~600 km/s. The outflow is detected as far as 460 pc from the centre in the northern direction, and has a mass of dense gas <8x10^8M_sun. The difference between the position angles of the inner disk (~70 degree) and the outflow (~10 degree) indicates that the outflow is likely powered by the AGN, and not by the starburst. Regarding the chemistry, we measure an extremely low HCO+/HOC+ ratio of 10+-5 in the inner disk of Mrk273.Comment: Accepted for publication in A&A. 21 pages, 17 figures, 7 tables, and a lot of interesting tex

Electron transport properties of sub-3-nm diameter copper nanowires

Density functional theory and density functional tight-binding are applied to model electron transport in copper nanowires of approximately 1 nm and 3 nm diameters with varying crystal orientation and surface termination. The copper nanowires studied are found to be metallic irrespective of diameter, crystal orientation and/or surface termination. Electron transmission is highly dependent on crystal orientation and surface termination. Nanowires oriented along the [110] crystallographic axis consistently exhibit the highest electron transmission while surface oxidized nanowires show significantly reduced electron transmission compared to unterminated nanowires. Transmission per unit area is calculated in each case, for a given crystal orientation we find that this value decreases with diameter for unterminated nanowires but is largely unaffected by diameter in surface oxidized nanowires for the size regime considered. Transmission pathway plots show that transmission is larger at the surface of unterminated nanowires than inside the nanowire and that transmission at the nanowire surface is significantly reduced by surface oxidation. Finally, we present a simple model which explains the transport per unit area dependence on diameter based on transmission pathways results

Chemically Distinct Nuclei and Outflowing Shocked Molecular Gas in Arp 220

We present the results of interferometric spectral line observations of Arp 220 at 3.5mm and 1.2mm from the Plateau de Bure Interferometer (PdBI), imaging the two nuclear disks in H$^{13}$CN$(1 - 0)$ and $(3 - 2)$, H$^{13}$CO$^+(1 - 0)$ and $(3 - 2)$, and HN$^{13}$C$(3 - 2)$ as well as SiO$(2 - 1)$ and $(6 - 5)$, HC$^{15}$N$(3 - 2)$, and SO$(6_6 - 5_5)$. The gas traced by SiO$(6 - 5)$ has a complex and extended kinematic signature including a prominent P Cygni profile, almost identical to previous observations of HCO$^+(3 - 2)$. Spatial offsets $0.1''$ north and south of the continuum centre in the emission and absorption of the SiO$(6 - 5)$ P Cygni profile in the western nucleus (WN) imply a bipolar outflow, delineating the northern and southern edges of its disk and suggesting a disk radius of $\sim40$ pc, consistent with that found by ALMA observations of Arp 220. We address the blending of SiO$(6 - 5)$ and H$^{13}$CO$^+(3 - 2)$ by considering two limiting cases with regards to the H$^{13}$CO$^+$ emission throughout our analysis. Large velocity gradient (LVG) modelling is used to constrain the physical conditions of the gas and to infer abundance ratios in the two nuclei. Our most conservative lower limit on the [H$^{13}$CN]/[H$^{13}$CO$^+$] abundance ratio is 11 in the WN, cf. 0.10 in the eastern nucleus (EN). Comparing these ratios to the literature we argue on chemical grounds for an energetically significant AGN in the WN driving either X-ray or shock chemistry, and a dominant starburst in the EN.Comment: 28 pages, 17 figures, accepted to Ap

Distributional Modes for Scalar Field Quantization

We propose a mode-sum formalism for the quantization of the scalar field based on distributional modes, which are naturally associated with a slight modification of the standard plane-wave modes. We show that this formalism leads to the standard Rindler temperature result, and that these modes can be canonically defined on any Cauchy surface.Comment: 15 pages, RevTe

High-excitation OH and H_2O lines in Markarian 231: the molecular signatures of compact far-infrared continuum sources

The ISO/LWS far-infrared spectrum of the ultraluminous galaxy Mkn 231 shows OH and H_2O lines in absorption from energy levels up to 300 K above the ground state, and emission in the [O I] 63 micron and [C II] 158 micron lines. Our analysis shows that OH and H_2O are radiatively pumped by the far-infrared continuum emission of the galaxy. The absorptions in the high-excitation lines require high far-infrared radiation densities, allowing us to constrain the properties of the underlying continuum source. The bulk of the far-infrared continuum arises from a warm (T_dust=70-100 K), optically thick (tau_100micron=1-2) medium of effective diameter 200-400 pc. In our best-fit model of total luminosity L_IR, the observed OH and H2O high-lying lines arise from a luminous (L/L_IR~0.56) region with radius ~100 pc. The high surface brightness of this component suggests that its infrared emission is dominated by the AGN. The derived column densities N(OH)>~10^{17} cm^{-2} and N(H_2O)>~6x10^{16} cm^{-2} may indicate XDR chemistry, although significant starburst chemistry cannot be ruled out. The lower-lying OH, [C II] 158 micron, and [O I] 63 micron lines arise from a more extended (~350 pc) starburst region. We show that the [C II] deficit in Mkn 231 is compatible with a high average abundance of C+ because of an extreme overall luminosity to gas mass ratio. Therefore, a [C II] deficit may indicate a significant contribution to the luminosity by an AGN, and/or by extremely efficient star formation.Comment: 16 pages, 6 figures, accepted for publication in The Astrophysical Journa

The Dense Molecular Gas and Nuclear Activity in the ULIRG IRAS 13120-5453

We present new ALMA Band 7 ($\sim340$ GHz) observations of the dense gas tracers HCN, HCO$^+$, and CS in the local, single-nucleus, ultraluminous infrared galaxy IRAS 13120-5453. We find centrally enhanced HCN (4-3) emission, relative to HCO$^+$ (4-3), but do not find evidence for radiative pumping of HCN. Considering the size of the starburst (0.5 kpc) and the estimated supernovae rate of $\sim1.2$ yr$^{-1}$, the high HCN/HCO$^+$ ratio can be explained by an enhanced HCN abundance as a result of mechanical heating by the supernovae, though the active galactic nucleus and winds may also contribute additional mechanical heating. The starburst size implies a high $\Sigma_{IR}$ of $4.7\times10^{12}$ $L_{\odot}$ kpc$^{-2}$, slightly below predictions of radiation-pressure limited starbursts. The HCN line profile has low-level wings, which we tentatively interpret as evidence for outflowing dense molecular gas. However, the dense molecular outflow seen in the HCN line wings is unlikely to escape the galaxy and is destined to return to the nucleus and fuel future star formation. We also present modeling of Herschel observations of the H$_2$O lines and find a nuclear dust temperature of $\sim40$ K. IRAS 13120-5453 has a lower dust temperature and $\Sigma_{IR}$ than is inferred for the systems termed "compact obscured nuclei" (such as Arp 220 and Mrk 231). If IRAS 13120-5453 has undergone a compact obscured nucleus phase, we are likely witnessing it at a time when the feedback has already inflated the nuclear ISM and diluted star formation in the starburst/AGN core.Comment: accepted for publication in ApJ, 21 pages, 11 figure