Anisotropic inverse Compton emission in the radio galaxy 3C 265

We present the results from a Chandra observation of the powerful radio galaxy 3C 265. We detect X-ray emission from the nucleus, the radio hotspots and lobes. In particular, the lobe X-ray emission is well explained as anisotropic inverse Compton scattering of the nuclear photons by the relativistic electrons in the radio lobes; the comparison between radio synchrotron and IC emission yields a magnetic field strength a factor about 2 lower than that calculated under minimum energy conditions. The X-ray spectrum of the nucleus is consistent with that of a powerful, strongly absorbed quasar and the X-ray emission of the south-eastern hotspot can be successfully reproduced by a combination of synchro-self Compton and inverse Compton emission assuming a magnetic field slightly lower than equipartition.Comment: 5 pages, 6 figures, to be published as a Letter on Monthly Notices of the Royal Astronomical Societ

An unlikely radio halo in the low X-ray luminosity galaxy cluster RXC J1514.9-1523

We report the discovery of a giant radio halo in the galaxy cluster RXC J1514.9-1523 at z=0.22 with a relatively low X-ray luminosity, $L_{X \, [0.1-2.4 \rm \, kev]} \sim 7 \times 10^{44}$ erg s$^{-1}$. This faint, diffuse radio source is detected with the Giant Metrewave Radio Telescope at 327 MHz. The source is barely detected at 1.4 GHz in a NVSS pointing that we have reanalyzed. The integrated radio spectrum of the halo is quite steep, with a slope \alpha = 1.6 between 327 MHz and 1.4 GHz. While giant radio halos are common in more X-ray luminous cluster mergers, there is a less than 10% probability to detect a halo in systems with L_X \ltsim 8 \times 10^{44} erg s$^{-1}$. The detection of a new giant halo in this borderline luminosity regime can be particularly useful for discriminating between the competing theories for the origin of ultrarelativistic electrons in clusters. Furthermore, if our steep radio spectral index is confirmed by future deeper radio observations, this cluster would provide another example of the recently discovered population of ultra-steep spectrum radio halos, predicted by the model in which the cluster cosmic ray electrons are produced by turbulent reacceleration.Comment: 4 pages, 2 figures - Accepted for publication on A&A Research Note

Dynamical locality of the nonminimally coupled scalar field and enlarged algebra of Wick polynomials

We discuss dynamical locality in two locally covariant quantum field theories, the nonminimally coupled scalar field and the enlarged algebra of Wick polynomials. We calculate the relative Cauchy evolution of the enlarged algebra, before demonstrating that dynamical locality holds in the nonminimally coupled scalar field theory. We also establish dynamical locality in the enlarged algebra for the minimally coupled massive case and the conformally coupled massive case.Comment: 39p

Population ageing, household portfolios and financial asset returns: a survey of the literature

Population ageing is a recognised phenomenon affecting many countries in the world including most EU ones, Japan and US. The financial implications of this phenomenon can be manifold and some recent literature has focused in particular on the possible consequences of ageing on household portfolios and on main financial asset returns ones. Overall, the extant literature on household portfolios reports a significant effect of age on asset allocation, thereby providing evidence in favour of the standard life-cycle hypothesis. On the other hand, empirical results on the link between demographics and financial asset prices/returns are less uniform. The aim of this paper is to systematize the extant literature on these issues and to provide an overview of the main results reported so far, trying to evaluate whether the different conclusions reached depend on the approach taken in the empirical exercises rather than on the actual differences, in terms of demographic dynamics, public pension systems and financial markets, of the realities considered

Shock heating of the merging galaxy cluster A521

A521 is an interacting galaxy cluster located at z=0.247, hosting a low frequency radio halo connected to an eastern radio relic. Previous Chandra observations hinted at the presence of an X-ray brightness edge at the position of the relic, which may be a shock front. We analyze a deep observation of A521 recently performed with XMM-Newton in order to probe the cluster structure up to the outermost regions covered by the radio emission. The cluster atmosphere exhibits various brightness and temperature anisotropies. In particular, two cluster cores appear to be separated by two cold fronts. We find two shock fronts, one that was suggested by Chandra and that is propagating to the east, and another to the southwestern cluster outskirt. The two main interacting clusters appear to be separated by a shock heated region, which exhibits a spatial correlation with the radio halo. The outer edge of the radio relic coincides spatially with a shock front, suggesting this shock is responsible for the generation of cosmic ray electrons in the relic. The propagation direction and Mach number of the shock front derived from the gas density jump, M = 2.4 +/- 0.2, are consistent with expectations from the radio spectral index, under the assumption of Fermi I acceleration mechanism

Radio Lobes of Pictor A: an X-ray spatially resolved Study

A new XMM observation has made possible a detailed study of both lobes of the radio galaxy Pictor A. Their X-ray emission is of non thermal origin and due to Inverse Compton scattering of the microwave background photons by relativistic electrons in the lobes, as previously found. In both lobes, the equipartition magnetic field (Beq) is bigger than the Inverse Compton value (Bic), calculated from the radio and X-ray flux ratio. The Beq/Bic ratio never gets below 2, in spite of the large number of reasonable assumptions tested to calculate Beq, suggesting a lobe energetic dominated by particles. The X-ray data quality is good enough to allow a spatially resolved analysis. Our study shows that Bic varies through the lobes. It appears to increase behind the hot spots. On the contrary, a rather uniform distribution of the particles is observed. As a consequence, the radio flux density variation along the lobes appears to be mainly driven by magnetic field changes.Comment: 15 pages, 3 figures, ApJ accepte

Laplacian spectral properties of signed circular caterpillars

A circular caterpillar of girth n is a graph such that the removal of all pendant vertices yields a cycle Cn of order n. A signed graph is a pair Γ = (G, σ), where G is a simple graph and σ ∶ E(G) → {+1, −1} is the sign function defined on the set E(G) of edges of G. The signed graph Γ is said to be balanced if the number of negatively signed edges in each cycle is even, and it is said to be unbalanced otherwise. We determine some bounds for the first n Laplacian eigenvalues of any signed circular caterpillar. As an application, we prove that each signed spiked triangle (G(3; p, q, r), σ), i. e. a signed circular caterpillar of girth 3 and degree sequence πp,q,r = (p + 2, q + 2, r + 2, 1,..., 1), is determined by its Laplacian spectrum up to switching isomorphism. Moreover, in the set of signed spiked triangles of order N, we identify the extremal graphs with respect to the Laplacian spectral radius and the first two Zagreb indices. It turns out that the unbalanced spiked triangle with degree sequence πN−3,0,0 and the balanced spike triangle (G(3; p, ^ q, ^ r^), +), where each pair in {p, ^ q, ^ r^} differs at most by 1, respectively maximizes and minimizes the Laplacian spectral radius and both the Zagreb indices

Population ageing, household portfolios and financial asset returns: A survey of the literature

Population ageing is a recognised phenomenon affecting many countries in the world including most EU ones, Japan and US. The financial implications of this phenomenon can be manifold and some recent literature has focused in particular on the possible consequences of ageing on household portfolios and on main financial asset returns ones. Overall, the extant literature on household portfolios reports a significant effect of age on asset allocation, thereby providing evidence in favour of the standard life-cycle hypothesis. On the other hand, empirical results on the link between demographics and financial asset prices/returns are less uniform. The aim of this paper is to systematize the extant literature on these issues and to provide an overview of the main results reported so far, trying to evaluate whether the different conclusions reached depend on the approach taken in the empirical exercises rather than on the actual differences, in terms of demographic dynamics, public pension systems and financial markets, of the realities considered

Unbalanced signed graphs with extremal spectral radius or index

Let ˙G = (G, σ) be a signed graph, and let ρ( ˙G ) (resp. λ1( ˙G )) denote the spectral radius (resp. the index) of the adjacency matrix A( ˙G) . In this paper we detect the signed graphs achieving the minimum spectral radius m(SRn), the maximum spectral radius M(SRn), the minimum index m(In) and the maximum index M(In) in the set U_n of all unbalanced connected signed graphs with n ≥ 3 vertices. From the explicit computation of the four extremal values it turns out that the difference m(SRn)−m(In) for n ≥ 8 strictly increases with n and tends to 1, whereas M(SRn) − M(In) strictly decreases and tends to 0