Euler-Poisson-Newton approach in Cosmology

This lecture provides us with Newtonian approaches for the interpretation of two puzzling cosmological observations that are still discussed subject : a bulk flow and a foam like structure in the distribution of galaxies. For the first one, we model the motions describing all planar distortions from Hubble flow, in addition of two classes of planar-axial distortions with or without rotation, when spatial distribution of gravitational sources is homogenous. This provides us with an alternative to models which assume the presence of gravitational structures similar to Great Attractor as origin of a bulk flow. For the second one, the model accounts for an isotropic universe constituted by a spherical void surrounded by a uniform distribution of dust. It does not correspond to the usual embedding of a void solution into a cosmological background solution, but to a global solution of fluid mechanics. The general behavior of the void expansion shows a huge initial burst, which freezes asymptotically up to match Hubble expansion. While the corrective factor to Hubble law on the shell depends weakly on cosmological constant at early stages, it enables us to disentangle significantly cosmological models around redshift z ~ 1.7. The magnification of spherical voids increases with the density parameter and with the cosmological constant. An interesting feature is that for spatially closed Friedmann models, the empty regions are swept out, what provides us with a stability criterion.Comment: 15 pages, 1 figur

Voids in the distribution of galaxies and the Cosmological constant

With the motivation in mind to evaluate the contribution of the cosmological constant $\Lambda$ on the foam like patterns formation process in the distribution of galaxies, we investigate the Newtonian dynamics of a spherical void embedded in an uniform medium which undergoes a Hubble expansion. We use a covariant approach for deriving the evolution with time of the shell (S) acting as a boundaries condition for the inside and outside media. As a result, with the usual values for the cosmological parameters, S expands with a huge initial burst that freezes up to matching Hubble flow. With respect to Friedmann comoving frame, its magnification increases nonlinearly with $\Lambda$, with a maximal growth rate at redshift $z\sim 1.7$. The velocity field inside S shows an interesting feature which enables us to disentangle a spatially closed from open universe. Namely, the void region are swept out in the first case, what can be interpreted as a stability criterion.Comment: 4 pages, 1 figur

Spherical Voids in Newton-Friedmann Universe

We show that the cosmological constant favours significantly the growth of voids in the universe. This dynamical effect is investigated within a newtonian approach with an extension to Friedmann-Lema\^{\i}tre model.Comment: to appea

Social practices and mobilisations of kinship: an introduction

International audienceThis academic investigation into the issue of kinship is the result of several workshops entitled ‘Running risks in the family: kinship put to the test of economics and politics, from Iran to the Balkans’, that were held on February 2004, 13th (Aix-en-Provence), and May 2004, 7-8th (Istanbul). These meetings were organised by the Institut d’ethnologie méditerranéenne et comparative (IDEMEC) [Institute of Comparative and Mediterranean Ethnology] and the Institut Français d’Etudes Anatoliennes (IFEA) [French Institute of Anatolian Studies]. They were coordinated by Gilles De Rapper and Benoit Fliche

The hemşehrilik and the village: the stakes of an association of former villagers in Ankara

This article analyses the reasons behind the successes and failures of collective actions intiated by an association of former villagers. Members of this association did not adhere to all these collective actions, as these must be acceptable in semiotic terms, and must also conform to the hemşehrilik egalitarian ideal. One of the main obstacles to associative mobilisation is that the village itself is a conflictual and competitive place. This contrast between village and association shows that this is more an association of hemşehri than a village association. This difference invites us to reconsider the relationship which former villagers can (or cannot) have with their village, and to question the signification of the term hemşehri

L'oncle et le député : circuits de ressources et usages de la parenté dans un lignage sacré en Turquie

International audienceThe Çelebi/Ulusoy are supposed to be the descendants of the Anatolian saint Hacı Bektaş. This family has long controlled different kinds of resources (religious, economic) reinforcing each other, this circuit being secured by its integration in the Ottoman imperial system. The closing of the bektashi brotherhood in 1925 caused both the diminution of the resources they controlled collectively, and conflicts about the distribution of these - most importantly the spiritual leadership[mürşitlik] -- inside the family. Consequently, the strategies that appeared aiming to increase and convert these resources into other sectors (mainly politics) became individual, and were mostly initiated by persons marginalized from mürşitlik. These initiatives caused both an increase and diversification of their personal resources and, since some of them were considered illegitimate, the decrease of the value of the collective resources (family authority, reputation). In the same way that family resources determine the strategies and margins for action of each of its members, their individual initiatives also have effects on the collective resources. At the same time, these individuals aiming to come closer to the core family have built centripetal alliances, thus contributing to produce a bounded family more favourable to them during future decades. As sacred as it may be, and even if based on something as tangible as blood, family remains a social construct and the product of collective action, at the crossroads of multiple tensions

Λ\Lambda effect in the cosmological expansion of voids

The dynamical effect of the cosmological constant $\Lambda$ on a single spherical void evolving in a the universe is investigated within a non linear perturbation of Newton-Friedmann models. The void expands with a huge initial burst which freezes asymptotically with time up to matching Hubble flow. For $\Omega_{\circ}\sim 0.3$, $\Lambda$-effect on the kinematics intervenes significantly by amplifying the expansion rate at redshift $z\sim 1.7$. As a result, the size increases with the background density and with $\Lambda$, what interprets by the gravitational attraction of borders from outside regions and the gravitational repulsion of borders. The velocity flow within the void region depends solely on $\Lambda$, it reads $\vec{v}=\sqrt{\Lambda/3}\vec{r}$. Hence, the empty regions are swept out for spatially closed Friedmann models what provides us with a stability criterion.Comment: 17 pages, 7 figure

Retour sur la question de l'émigration en Turquie :: Une analyse des propositions au départ dans un village d'Anatolie centrale

International audienc

The hemşehrilik and the village: the stakes of an association of former villagers in Ankara

This article analyses the reasons behind the successes and failures of collective actions intiated by an association of former villagers. Members of this association did not adhere to all these collective actions, as these must be acceptable in semiotic terms, and must also conform to the hemşehrilik egalitarian ideal. One of the main obstacles to associative mobilisation is that the village itself is a conflictual and competitive place. This contrast between village and association shows that this is more an association of hemşehri than a village association. This difference invites us to reconsider the relationship which former villagers can (or cannot) have with their village, and to question the signification of the term hemşehri

Ghurba/gurbet : variations autour de l’exil, Institut d’études de l’islam et des sociétés du monde musulman (IISMM) et le Centre d’histoire du domaine turc (EHESS), 17 novembre 2003

D’étymologie arabe, ghurba (racine arabe, GH-R-B), ou gurbet en turc, désigne à l’origine ce qui est loin, rare et surtout ce qui est étranger, qui ne ressemble à rien (définition donnée par Pierre Lory). Associé à l’Occident entendu comme espace tant géographique que symbolique, le terme désigne une expérience « d’altérité », vécue sur un mode positif ou négatif. À la différence du muhacir (racine arabe, H-J-R) qui, originellement, quitte la terre de mécréants pour la terre sainte (de La Mec..