From Seed to Impact: Building the Foundations for a High-Impact Social Entrepreneurship Ecosystem

In this paper GSEN has collaborated with its global network of intermediary organisations to conduct one of the first dedicated investigations into support for early-stage social entrepreneurs. It draws on the data and experiences of 33 GSEN members to uncover the methodologies they use, as well as the opportunities and benefits of joining forces within a network

Deflection of jets induced by jet-cloud & jet-galaxy interactions

The model first introduced by Raga & Canto (1996) in which astrophysical jets are deflected on passing through an isothermal high density region is generalised by taking into account gravitational effects on the motion of the jet as it crosses the high density cloud. The problem is also generalised for relativistic jets in which gravitational effects induced by the cloud are neglected. Two further cases, classical and relativistic, are discussed for the cases in which the jet is deflected on passing through the interstellar gas of a galaxy in which a dark matter halo dominates the gravitational potential. The criteria for the stability of jets due to the formation of internal shocks are discussed.Comment: 8 pages, 5 figures, Accepted for publication in MNRA

Synchrotron Radiation from the Galactic Center in Decaying Dark Matter Scenario

We discuss the synchrotron radiation flux from the Galactic center in unstable dark matter scenario. Motivated by the anomalous excess of the positron fraction recently reported by the PAMELA collaboration, we consider the case that the dark matter particle is unstable (and long-lived), and that energetic electron and positron are produced by the decay of dark matter. Then, the emitted electron and positron becomes the source of the synchrotron radiation. We calculate the synchrotron radiation flux for models of decaying dark matter, which can explain the PAMELA positron excess. Taking the lifetime of the dark matter of O(10^26 sec), which is the suggested value to explain the PAMELA anomaly, the synchrotron radiation flux is found to be O(1 kJy/str) or smaller, depending on the particle-physics and cosmological parameters.Comment: 20 pages, 6 figure

Is space really expanding? A counterexample

In all Friedman models, the cosmological redshift is widely interpreted as a consequence of the general-relativistic phenomenon of EXPANSION OF SPACE. Other commonly believed consequences of this phenomenon are superluminal recession velocities of distant galaxies and the distance to the particle horizon greater than c*t (where t is the age of the Universe), in apparent conflict with special relativity. Here, we study a particular Friedman model: empty universe. This model exhibits both cosmological redshift, superluminal velocities and infinite distance to the horizon. However, we show that the cosmological redshift is there simply a relativistic Doppler shift. Moreover, apparently superluminal velocities and `acausal' distance to the horizon are in fact a direct consequence of special-relativistic phenomenon of time dilation, as well as of the adopted definition of distance in cosmology. There is no conflict with special relativity, whatsoever. In particular, INERTIAL recession velocities are subluminal. Since in the real Universe, sufficiently distant galaxies recede with relativistic velocities, these special-relativistic effects must be at least partly responsible for the cosmological redshift and the aforementioned `superluminalities', commonly attributed to the expansion of space. Let us finish with a question resembling a Buddhism-Zen `koan': in an empty universe, what is expanding?Comment: 12 pages, no figures; added Appendix with a calculation of the cosmological redshift in `private space

Unjustly dismissing an alternative : a case of epistemic injustice among epistemic frameworks

The concept of epistemic injustice has become a useful tool for understanding some of the wrongs and harms that result from the interplay of identity and knowledge. However, this paper proposes that analysis of epistemic injustice needs to consider not only the level of individual or institutional epistemic transactions, but also the level of epistemic frameworks. Drawing on Gaile Pohlhaus Jr. and Rajeev Bhargava, I examine the Cuban health care system and the epistemic framework it is based on as a case study of how prejudice that leads to the dismissal, discrediting and marginalization of such an epistemic framework can be an epistemic injustice.Le concept d'injustice épistémique est devenu un outil utile pour comprendre certains des torts et des inconvénients résultant de l'interaction de l'identité et du savoir. Cependant, cet article défend que l'analyse de l'injustice épistémique doit prendre en compte non seulement le niveau des transactions épistémiques individuelles ou institutionnelles, mais également le niveau des cadres épistémiques. En m'appuyant sur Gaile Pohlhaus Jr. et Rajeev Bhargava, j'examine le système de santé cubain et le cadre épistémique sur lequel il est basé, en tant qu'étude de cas sur la manière dont les préjugés qui entraînent la démission, le discrédit et la marginalisation d'un tel cadre épistémique peuvent être une injustice épistémique

Radio constraints on dark matter annihilation in the galactic halo and its substructures

Annihilation of Dark Matter usually produces together with gamma rays comparable amounts of electrons and positrons. The e+e- gyrating in the galactic magnetic field then produce secondary synchrotron radiation which thus provides an indirect mean to constrain the DM signal itself. To this purpose, we calculate the radio emission from the galactic halo as well as from its expected substructures and we then compare it with the measured diffuse radio background. We employ a multi-frequency approach using data in the relevant frequency range 100 MHz-100 GHz, as well as the WMAP Haze data at 23 GHz. The derived constraints are of the order =10^{-24} cm3 s^{-1} for a DM mass m_chi=100 GeV sensibly depending however on the astrophysical uncertainties, in particular on the assumption on the galactic magnetic field model. The signal from single bright clumps is instead largely attenuated by diffusion effects and offers only poor detection perspectives.Comment: 12 pages, 7 figures; v2: some references added, some discussions enlarged; matches journal versio

Visions of the global: the classical and the eclectic in colonial East African architecture

This article discusses the use of the classical language of architecture in the early colonial urban landscape in East Africa and assesses the stylistic choices by British colonial architects in Zanzibar and Nairobi. It focuses upon the buildings of John Sinclair, administrator-architect in Zanzibar from the early 1900s to 1923 and his later work in Nairobi. It highlights the various competing factors which informed decisions made by architects in the colonial world

A jet-cloud interaction in 3C34 at redshift z = 0.69

We report the detection of a strong jet-cloud interaction at a distance of 120 kpc from the nucleus of the radio galaxy 3C34, which has redshift z=0.69. Hubble Space Telescope images of the radio galaxy show a long narrow region of blue emission orientated along the radio axis and directed towards a radio hotspot. The William Herschel Telescope has been used to provide long-slit spectroscopic data of this object, and infrared observations made with the United Kingdom InfraRed Telescope have enabled its spectral energy distribution to be modelled. We propose that the aligned emission is associated with a region of massive star-formation, induced by the passage of the radio jet through a galaxy within the cluster surrounding 3C34. A star-formation rate of about 100 solar masses per year is required, similar to the values necessary to produce the alignment effect in high-redshift radio galaxies. The consequences of this result for models of star formation in distant radio galaxies are discussed.Comment: 12 pages including 11 figures, LaTeX. To appear in MNRA