Mapping the Shadow Economy: Spatial Variations in the use of High Denomination Bank Notes in Brussels

The aim of this paper is to map the spatial variations in the size of the shadow economy within Brussels. Reporting data provided by the National Bank of Belgium on the deposit of high denomination banknotes across bank branches in the 19 municipalities of the Brussels-Capital Region, the finding is that the shadow economy is concentrated in wealthier populations and not in deprived or immigrant communities. The outcome is a call to transcend the association of the shadow economy with marginalized groups and the wider adoption of this indirect method when measuring spatial variations in the shadow economy

Unstable fields in Kerr spacetimes

We show that both the interior region $r<M-\sqrt{M^2-a^2}$ of a Kerr black hole and the $a^2>M^2$ Kerr naked singularity admit unstable solutions of the Teukolsky equation for any value of the spin weight. For every harmonic number there is at least one axially symmetric mode that grows exponentially in time and decays properly in the radial directions. These can be used as Debye potentials to generate solutions for the scalar, Weyl spinor, Maxwell and linearized gravity field equations on these backgrounds, satisfying appropriate spatial boundary conditions and growing exponentially in time, as shown in detail for the Maxwell case. It is suggested that the existence of the unstable modes is related to the so called "time machine" region, where the axial Killing vector field is time-like, and the Teukolsky equation, restricted to axially symmetric fields, changes its character from hyperbolic to elliptic

SDSSJ092712.65+294344.0: a candidate massive black hole binary

In this Letter we explore the hypothesis that the quasar SDSSJ092712.65+294344.0 is hosting a massive black hole binary embedded in a circumbinary disc. The lightest, secondary black hole is active, and gas orbiting around it is responsible for the blue-shifted broad emission lines with velocity off-set of 2650 km/s, relative to the galaxy rest frame. As the tidal interaction of the binary with the outer disc is expected to excavate a gap, the blue-shifted narrow emission lines are consistent with being emitted from the low-density inhomogeneous gas of the hollow region. From the observations we infer a binary mass ratio q ~ 0.3, a mass for the primary of M1 ~ 2 billion Msun and a semi-major axis of 0.34 pc, corresponding to an orbital period of 370 years. We use the results of cosmological merger trees to estimate the likely-hood of observing SDSSJ092712.65+294344.0 as recoiling black hole or as a binary. We find that the binary hypothesis is preferred being one hundred times more probable than the ejection hypothesis. If SDSSJ092712.65+294344.0 hosts a binary, it would be the one closest massive black hole binary system ever discovered.Comment: Accepted for publication in MNRAS Letter

Two hearts and a loan? Mortgages, employment insecurity and earnings among young couples in six European countries

Homeownership is increasingly understood by policy makers and social scientists as a fundamental asset against poverty risks, especially in times of economic uncertainty. However, in several Western countries, homeownership among younger generations appears to be increasingly difficult to achieve, likely a result of growing employment instability and stringent criteria to access credit. This article uses multinomial logistic models and nationally representative EU-SILC data from six European countries to examine (a) to what extent precarious employment among young couples is linked to being a mortgage holder; (b) whether earned income can compensate for employment instability in being a mortgagee; (c) cross-national differences in the relationship between being a mortgage holder, earnings, and employment insecurity. Our results indicate that the higher the levels of employment insecurity, the lower the chances of being a mortgage holder in all countries. Moreover, we find that at a given level of employment insecurity, households with higher levels of earned income have higher chances of being mortgage holders than households with lower earned income. However, while earned income has a stronger effect in achieving a mortgage among couples who have secure employment in Italy, earnings are more important among couples with lower levels of employment security in France, the UK, Spain and Poland. These results suggest that the relationship between social inequalities and housing is partially mediated by the national context

Search of sub-parsec massive binary black holes through line diagnosis

We investigate on the spectral properties of an active black hole, member of a massive (10^7 - 10^9 Msun) sub-parsec black hole binary. We work under the hypothesis that the binary, surrounded by a circum-binary disc, has cleared a gap, and that accretion occurs onto the secondary black hole fed by material closer to the inner edge of the disc. Broad line emission clouds orbit around the active black hole and suffer erosion due to tidal truncation at the Roche Lobe surface, following gap opening and orbital decay. We consider three of the most prominent broad emission lines observed in the spectra of AGNs, i.e. CIV, MgII and H{\beta}, and compute the flux ratios between the lines of MgII and CIV (FMgII/FCIV) and those of MgII and H{\beta} (FMgII/FH{\beta}). We find that close black hole binaries have FMgII/FCIV up to one order of magnitude smaller than single black holes. By contrast FMgII/FH{\beta} may be significantly reduced only at the shortest separations. Peculiarly low values of line flux ratios together with large velocity offsets between the broad and narrow emission lines and/or periodic variability in the continuum (on timescales >= years) would identify genuine sub-pc binary candidates.Comment: 7 pages, 4 figures. Accepted for publication in MNRA

Probing the formation history of the nuclear star cluster at the Galactic Centre with millisecond pulsars

The origin of the Nuclear Star Cluster in the centre of our Galaxy is still unknown. One possibility is that it formed after the disruption of stellar clusters that spiralled into the Galactic Centre due to dynamical friction. We trace the formation of the Nuclear Star Cluster around the central black hole, using state-of-the-art N-body simulations, and follow the dynamics of the neutron stars born in the clusters. We then estimate the number of Millisecond Pulsars (MSPs) that are released in the Nuclear Star Cluster, during its formation. The assembly and tidal dismemberment of globular clusters lead to a population of MSPs distributed over a radius of about 20 pc, with a peak near 3 pc. No clustering is found on the sub-parsec scale. We simulate the detectability of this population with future radio telescopes like the MeerKAT radio telescope and SKA1, and find that about of order ten MSPs can be observed over this large volume, with a paucity of MSPs within the central parsec. This helps discriminating this scenario from the in-situ formation model for the Nuclear Star Cluster that would predict an over abundance of MSPs closer to the black hole. We then discuss the potential contribution of our MSP population to the gamma-ray excess at the Galactic Centre.Comment: 11 pages, 8 figures, accepted for publication in MNRA

New working spaces. Policy perspectives before and after the COVID-19 pandemic

This chapter maps the debate of new working spaces (particularly CSs) on the level of European policy making. It explores how new working spaces have been interpreted by the European Commission and how this debate has evolved from its origins up to the recent COVID-19 period. For these purposes, two diferent ideas of CSs will be presented and discussed: CSs as innovation drivers boosting economic development; and as opportunities for territorial regeneration, such as brownfeld redevelopment or local hubs promoting social cohesion. Specifc attention is devoted to identifying the evolution of policies supporting these spaces with a focus on place-based and urban planning measures before and during the COVID-19 pandemic. This chapter empirically investigates this debate analyzing EU policy reports and case studies. Finally, remarks and suggestions for policy learning are presented

Axonal and dendritic endocytic pathways in cultured neurons

The endocytic pathways from the axonal and dendritic surfaces of cultured polarized hippocampal neurons were examined. The dendrites and cell body contained extensive networks of tubular early endosomes which received endocytosed markers from the somatodendritic domain. In axons early endosomes were confined to presynaptic terminals and to varicosities. The somatodendritic but not the presynaptic early endosomes were labeled by internalized transferrin. In contrast to early endosomes, late endosomes and lysosomes were shown to be predominantly located in the cell body. Video microscopy was used to follow the transport-t of internalized markers from the periphery of axons and dendrites back to the cell body. Labeled structures in both domains moved unidirectionally by retrograde fast transport. Axonally transported organelles were sectioned for EM after video microscopic observation and shown to be large multivesicular body-like structures. Similar structures accumulated at the distal side of an axonal lesion. Multivesicular bodies therefore appear to be the major structures mediating transport of endocytosed markers between the nerve terminals and the cell body. Late endocytic structures were also shown to be highly mobile and were observed moving within the cell body and proximal dendritic segments. The results show that the organization of the endosomes differs in the axons and dendrites of cultured rat hippocampal neurons and that the different compartments or stages of the endocytic pathways can be resolved spatially

Probing black hole accretion in quasar pairs at high redshift

Models and observations suggest that luminous quasar activity is triggered by mergers, so it should preferentially occur in the most massive primordial dark matter haloes, where the frequency of mergers is expected to be the highest. Since the importance of galaxy mergers increases with redshift, we identify the high-redshift Universe as the ideal laboratory for studying dual AGN. Here we present the X-ray properties of two systems of dual quasars at z=3.0-3.3 selected from the SDSS-DR6 at separations of 6-8 arcsec (43-65kpc) and observed by Chandra for 65ks each. Both members of each pair are detected with good photon statistics to allow us to constrain the column density, spectral slope and intrinsic X-ray luminosity. We also include a recently discovered dual quasar at z=5 (separation of 21 arcsec, 136kpc) for which XMM-Newton archival data allow us to detect the two components separately. Using optical spectra we derived bolometric luminosities, BH masses and Eddington ratios that were compared to those of luminous SDSS quasars in the same redshift ranges. We find that the brighter component of both pairs at z=3.0-3.3 has high luminosities compared to the distribution of SDSS quasars at similar redshift, with J1622A having an order magnitude higher luminosity than the median. This source lies at the luminous end of the z~3.3 quasar luminosity function. While we cannot conclusively state that the unusually high luminosities of our sources are related to their having a close companion, for J1622A there is only a 3% probability that it is by chance.Comment: MNRAS, in pres