Wage Bargaining and Induced Technical Change in a Linear Economy: Model and Application to the US (1963-2003)

In a simple one-sector, two-class, fixed-proportions economy, wages are set through axiomatic bargaining a la Nash [1950]. As for choice of technology, firms choose the direction of factor augmentations to maximize the rate of unit cost reduction (Kennedy [1964], and more recently Funk [2002]). The aggregate environment resulting by self-interested decisions made by economic agents is described by a two-dimensional dynamical system in the employment rate and output/capital ratio. The economy converges cyclically to a long-run equilibrium involving a Harrod-neutral prole of technical change, a constant rate of employment of labor, and constant input shares. The type of oscillations predicted by the model matches the available data on the United States (1963-2003). Finally, institutional change, as captured by variations in workers' bargaining power, has a positive effect on the rate of output growth but a negative effect on employment.Bargaining; Induced Technical Change; Factor Shares; Employment

The variable Crab Nebula

The remarkable Crab Nebula is powered by an energetic pulsar whose relativistic wind interacts with the inner parts of the Supernova Remnant SN1054. Despite low-intensity optical and X-ray variations in the inner Nebula, the Crab has been considered until now substantially stable at X-ray and gamma-ray energies. This paradigm has been shattered by the AGILE discovery in September 2010 of a very intense transient gamma-ray flare of nebular origin. For the first time, the Crab Nebula was "caught in the act" of accelerating particles up to 10^15 eV within the shortest timescale ever observed in a cosmic nebula (1 day or less). Emission between 50 MeV and a few GeV was detected with a quite hard spectrum within a short timescale. Additional analysis and recent Crab Nebula data lead to identify a total of four major flaring gamma-ray episodes detected by AGILE and Fermi during the period mid-2007/mid-2011. These observations challenge emission models of the pulsar wind interaction and particle acceleration processes. Indeed, the discovery of fast and efficient gamma-ray transient emission from the Crab leads to substantially revise current models of particle acceleration.Comment: 14 pages, 8 figures, 1 table. Proceedings of the 25th Texas Symposium on Relativistic Astrophysics - TEXAS 2010 December 06-10, 2010 Heidelberg, German

X-ray emission from the PSR B1259--63 system near apastron

The PSR B1259--63 system contains a 47 ms radio pulsar in a highly eccentric binary with a Be-star companion. Strongly time variable X-ray emission was reported from this system as the pulsar was near apastron in 1992-early 1993. The variability was primarily deduced from an apparent non-detection of the \psr system during a first pre-apastron \ros observation in February~1992. We have re-analyzed the \ros observations of the \psr system. Contrary to the results of a previous analysis, we find that the \psr system was detected by \ros during the first off-axis February~1992 observation. The intensity of the soft X-ray emission of the \psr system before and after the 1992 apastron appears to vary at most by a factor $\sim 2$. Our results sensibly constrain theoretical models of X-ray emission from the \psr system.Comment: LATEX, Accepted for publ. in ApJ

Time Resolved GRB Spectroscopy

We present the main results of a study of time-resolved spectra of 43 intense GRBs detected by BATSE. We considered the 4-parameter Band model and the Optically Thin Synchrotron Shock model (OTSSM). We find that the large majority of time-resolved spectra of GRBs are in remarkable agreement with the OTSSM. However, about 15 % of initial GRB pulses show an apparent low-energy photon suppression. This phenomenon indicates that complex radiative conditions modifying optically thin emission may occur during the initial phases of some GRBs.Comment: 5 pages, 3 figures, Paper presented at the 5th Huntsville Symposium, Huntsville (Alabama) Oct. 199

Wage Bargaining and Induced Technical Change in a Linear Economy: Model and Application to the US (1963-2003)

In a simple one-sector, two-class, fixed-proportions economy, wages are set through axiomatic bargaining a`la Nash (1950). As for choice of technology, firms choose the direction of factor augmentations to maximize the rate of unit cost reduction (Kennedy 1964, and more recently Funk 2002). The ag-gregate environment resulting by self-interested decisions made by economic agents is described by a two-dimensional dynamical system in the employment rate and output/capital ratio. The economy converges cyclically to a long-run equilibrium involving a Harrod-neutral profile of technical change, a constant rate of employment of labor, and constant input shares. The type of oscillations predicted by the model matches the available data on the United States (1963-2003). Finally, institutional change, as captured by variations in workers’ bargaining power, has a positive effect on the rate of output growth but a negative effect on employment.Bargaining, Induced Technical Change, Factor Shares, Employment.

Gamma rays from hidden millisecond pulsars

The properties were studied of a new class of gamma ray sources consisting of millisecond pulsars totally or partially surrounded by evaporating material from irradiated companion stars. Hidden millisecond pulsars offer a unique possibility to study gamma ray, optical and radio emission from vaporizing binaries. The relevance of this class of binaries for GRO observations and interpretation of COS-B data is emphasized

First-passage phenomena in hierarchical networks

In this paper we study Markov processes and related first passage problems on a class of weighted, modular graphs which generalize the Dyson hierarchical model. In these networks, the coupling strength between two nodes depends on their distance and is modulated by a parameter $\sigma$. We find that, in the thermodynamic limit, ergodicity is lost and the "distant" nodes can not be reached. Moreover, for finite-sized systems, there exists a threshold value for $\sigma$ such that, when $\sigma$ is relatively large, the inhomogeneity of the coupling pattern prevails and "distant" nodes are hardly reached. The same analysis is carried on also for generic hierarchical graphs, where interactions are meant to involve $p$-plets ($p>2$) of nodes, finding that ergodicity is still broken in the thermodynamic limit, but no threshold value for $\sigma$ is evidenced, ultimately due to a slow growth of the network diameter with the size

Theory of Gamma-Ray Burst Emission in Light of BSAX Results

We briefly discuss the theoretical implications of recent detections of gamma-ray bursts (GRBs) by BSAX. Relativistic shock wave theories of fireball expansion are challenged by the wealth of X-ray, optical and radio data obtained after the discovery of the first X-ray GRB afterglow. BSAX data contribute to address several issues concerning the initial and afterglow GRB emission. The observations also raise many questions that are still unsolved. The synchrotron shock model is in very good agreement with time-resolved broad-band spectra (2-500 keV) for the majority of GRBs detected by BSAX.Comment: 8 pages, LATEX text plus two postscript figures included. To appear in the Proceedings of the Accademia dei Lincei Symposium: "The Active X-ray Sky: Results from Beppo-SAX and Rossi-XTE", Nuclear Physics B Proceedings Supplement, eds. L. Scarsi et a

Modelling the Kinked Jet of the Crab Nebula

We investigate the dynamical propagation of the South-East jet from the Crab pulsar interacting with supernova ejecta by means of three-dimensional relativistic MHD numerical simulations with the PLUTO code. The initial jet structure is set up from the inner regions of the Crab Nebula. We study the evolution of hot, relativistic hollow outflows initially carrying a purely azimuthal magnetic field. Our jet models are characterized by different choices of the outflow magnetization ($\sigma$ parameter) and the bulk Lorentz factor ($\gamma_{j}$). We show that the jet is heavily affected by the growth of current-driven kink instabilities causing considerable deflection throughout its propagation length. This behavior is partially stabilized by the combined action of larger flow velocities and/or reduced magnetic field strengths. We find that our best jet models are characterized by relatively large values of $\sigma$ ($\gtrsim 1$) and small values of $\gamma_{j}\simeq 2$. Our results are in good agreement with the recent X-ray (\textit{Chandra}) data of the Crab Nebula South-East jet indicating that the jet changes direction of propagation on a time scale of the order of few years. The 3D models presented here may have important implications in the investigation of particle acceleration in relativistic outflows.Comment: 15 pages, 20 figure