Theoretical macroeconomic modelling and qualitative specifications of the bond market

Macroeconomics ; Bonds

Inside the Bondi radius of M87

Chandra X-ray observations of the nearby brightest cluster galaxy M87 resolve the hot gas structure across the Bondi accretion radius of the central supermassive black hole, a measurement possible in only a handful of systems but complicated by the bright nucleus and jet emission. By stacking only short frame-time observations to limit pileup, and after subtracting the nuclear PSF, we analysed the X-ray gas properties within the Bondi radius at 0.12-0.22 kpc (1.5-2.8 arcsec), depending on the black hole mass. Within 2 kpc radius, we detect two significant temperature components, which are consistent with constant values of 2 keV and 0.9 keV down to 0.15 kpc radius. No evidence was found for the expected temperature increase within ~0.25 kpc due to the influence of the SMBH. Within the Bondi radius, the density profile is consistent with $\rho\propto r^{-1}$. The lack of a temperature increase inside the Bondi radius suggests that the hot gas structure is not dictated by the SMBH's potential and, together with the shallow density profile, shows that the classical Bondi rate may not reflect the accretion rate onto the SMBH. If this density profile extends in towards the SMBH, the mass accretion rate onto the SMBH could be at least two orders of magnitude less than the Bondi rate, which agrees with Faraday rotation measurements for M87. We discuss the evidence for outflow from the hot gas and the cold gas disk and for cold feedback, where gas cooling rapidly from the hot atmosphere could feed the cirumnuclear disk and fuel the SMBH. At 0.2 kpc radius, the cooler X-ray temperature component represents ~20% of the total X-ray gas mass and, by losing angular momentum to the hot gas component, could provide a fuel source of cold clouds within the Bondi radius.Comment: 14 pages, 8 figures, accepted by MNRA

Noise-induced dynamical transition in systems with symmetric absorbing states

We investigate the effect of noise strength on the macroscopic ordering dynamics of systems with symmetric absorbing states. Using an explicit stochastic microscopic model, we present evidence for a phase transition in the coarsening dynamics, from an Ising-like to a voter-like behavior, as the noise strength is increased past a nontrivial critical value. By mapping to a thermal diffusion process, we argue that the transition arises due to locally-absorbing states being entered more readily in the high-noise regime, which in turn prevents surface tension from driving the ordering process.Comment: v2 with improved introduction and figures, to appear in PRL. 4 pages, 4 figure

The Identification of Male-Specific Transcripts From D. melanogaster

A primary Lambda genomic library was screened with cDNA probes derived from male and female 3rd instar larval mRNA. Twenty clones which show male-specific or male-elevated expression were identified. Ten of these clones have been characterised in some detail. Two of the clones, gK14 and gK21, appear to be re-isolates of the previously identified male-specific genes mst349 and mst336 (DiBenedetto et al., 1987). These, along with five new isolates (gS4, gS8, gS9, gS10, gK33) show expression patterns on northern blots consistent with germline-specific expression. The transcripts are expressed in male larvae, pupae and adults but not in agametic males or XX individuals transformed to somatic males by the tra2 mutation (pseudomales). Two of these clones, gS8 and gS9, are non-overlapping but cross hybridise at high stringency indicating that they contain the same or very similar sequences. Partial cDNA clones identify a single band in female DNA but multiple bands in male DNA, suggesting the transcribed sequence is Y associated. Many of these male-specific bands are conserved in at least 3 different laboratory strains. Northern blots using RNA from XO and XY males show similar levels of the transcript suggesting that the non sex-specific locus can be transcribed, at least in the absence of a Y chromosome. In-situ hybridisation to polytene chromosomes with either of the genomic clones give no signal suggesting that the non sex-specific genomic location is under replicated or heterochromatic. Another of these germline-specific clones, gS4, appears to be heterochromatic. Southern blots of genomic DNA indicate the presence of several different repeats. In addition in-situ hybridisation to polytene chromosomes indicate that these repeats reside at a single genomic location: at the base of the left arm of chromosome 2. Of the three remaining clones, gS1 identifies a weakly expressed 3.0kb male-specific transcript. Although this transcript is not detected in agametic males low levels of expression during the pupal stage suggests that it may not be germline specific. The other two clones gS2 and gK15, are overlapping and map uniquely to region 61F on the polytene chromosome map. These clones identify at least 3 male-specific transcripts on northern blots as well as a non sex-specific transcript which is elevated during the embryonic and pupal stages. The pattern of expression appears to be complex, all of the transcripts are developmentally regulated. One of the male-specific transcripts is expressed in agametic males and possibly in pseudomales. This transcript is also present in the embryo although it is not known at present if it is sex-specific at this stage

The effect of the quasar H1821+643 on the surrounding intracluster medium: revealing the underlying cooling flow

We present a detailed study of the thermodynamic properties of the intracluster medium of the only low redshift galaxy cluster to contain a highly luminous quasar, H1821+643. The cluster is a highly massive, strong cool core cluster. We find that the ICM entropy around the quasar is significantly lower than that of other similarly massive strong cool core clusters within the central 80 kpc, and that the entropy lies significantly below the extrapolated baseline entropy profile from hierarchical structure formation. By comparing the scaled temperature profile with those of other strong cool core clusters of similar total mass, we see that the entropy deficiency is due to the central temperature being significantly lower. This suggests that the presence of the quasar in the core of H1821+643 has had a dramatic cooling effect on the intracluster medium around it. We find that, if the quasar was brighter in the past, Compton cooling by radiation from the quasar may have caused the low entropy and temperature levels in the ICM around the quasar. Curiously, the gradients of the steep central temperature and entropy decline are in reasonable agreement with the profiles expected for a constant pressure cooling flow. It is possible that the system has been locked into a Compton cooled feedback cycle which prevents energy release from the black hole heating the gas sufficiently to switch it off, leading to the formation of a huge (~3x10^10 solar mass) supermassive black hole.Comment: 8 pages, 10 figures. Accepted for publication in MNRA

A linear theory for control of non-linear stochastic systems

We address the role of noise and the issue of efficient computation in stochastic optimal control problems. We consider a class of non-linear control problems that can be formulated as a path integral and where the noise plays the role of temperature. The path integral displays symmetry breaking and there exist a critical noise value that separates regimes where optimal control yields qualitatively different solutions. The path integral can be computed efficiently by Monte Carlo integration or by Laplace approximation, and can therefore be used to solve high dimensional stochastic control problems.Comment: 5 pages, 3 figures. Accepted to PR

Numerical investigation of turbulence effects on boundary layer separation in axisymmetric scramjet inlets via design optimisation

Inlet aerodynamics plays a key role in the successful operation of hypersonic airbreathing systems for flexible and economical access-to-space and atmospheric flight. Flow separation, however, can critically deteriorate the engine performance particularly for internal-compression scramjets with high contraction, where the boundary layer is susceptible to adverse pressure gradients. The flow physics of an axisymmetric scramjet inlet is investigated by means of the design optimisation of transition trip wires

Semi-Classical Description of Antiproton Capture on Atomic Helium

A semi-classical, many-body atomic model incorporating a momentum-dependent Heisenberg core to stabilize atomic electrons is used to study antiproton capture on Helium. Details of the antiproton collisions leading to eventual capture are presented, including the energy and angular momentum states of incident antiprotons which result in capture via single or double electron ionization, i.e. into [He$^{++}\,\bar p$ or He$^{+}\,\bar p$], and the distribution of energy and angular momentum states following the Auger cascade. These final states are discussed in light of recently reported, anomalously long-lived antiproton states observed in liquid He.Comment: 15 pages, 9 figures may be obtained from authors, Revte