A Study of the Di-Hadron Angular Correlation Function in Event by Event Ideal Hydrodynamics

The di-hadron angular correlation function is computed within boost invariant, ideal hydrodynamics for Au+Au collisions at $\sqrt{s}_{NN}=200$ GeV using Monte Carlo Glauber fluctuating initial conditions. When $0<p_T< 3$ GeV, the intensity of the flow components and their phases, $\left\{v_n, \Psi_n \right \}$ ($n=2,3$), are found to be correlated on an event by event basis to the initial condition geometrical parameters $\left\{\varepsilon_{2,n}, \Phi_{2,n} \right \}$, respectively. Moreover, the fluctuation of the relative phase between trigger and associated particles, $\Delta_n =\Psi_n^t - \Psi_n^a$, is found to affect the di-hadron angular correlation function when different intervals of transverse momentum are used to define the trigger and the associated hadrons.Comment: 15 pages, 10 figures; typos fixed, added reference

Analytical approach to directed sandpile models on the Apollonian network

We investigate a set of directed sandpile models on the Apollonian network, which are inspired on the work by Dhar and Ramaswamy (PRL \textbf{63}, 1659 (1989)) for Euclidian lattices. They are characterized by a single parameter $q$, that restricts the number of neighbors receiving grains from a toppling node. Due to the geometry of the network, two and three point correlation functions are amenable to exact treatment, leading to analytical results for the avalanche distributions in the limit of an infinite system, for $q=1,2$. The exact recurrence expressions for the correlation functions are numerically iterated to obtain results for finite size systems, when larger values of $q$ are considered. Finally, a detailed description of the local flux properties is provided by a multifractal scaling analysis.Comment: 7 pages in two-column format, 10 illustrations, 5 figure

Eccentricity fluctuations in an integrated hybrid approach: Influence on elliptic flow

The effects of initial state fluctuations on elliptic flow are investigated within a (3+1)d Boltzmann + hydrodynamics transport approach. The spatial eccentricity ($\epsilon_{\rm RP}$ and $\epsilon_{\rm part}$) is calculated for initial conditions generated by a hadronic transport approach (UrQMD). Elliptic flow results as a function of impact parameter, beam energy and transverse momentum for two different equations of state and for averaged initial conditions or a full event-by-event setup are presented. These investigations allow the conclusion that in mid-central ($b=5-9$ fm) heavy ion collisions the final elliptic flow is independent of the initial state fluctuations and the equation of state. Furthermore, it is demonstrated that most of the $v_2$ is build up during the hydrodynamic stage of the evolution. Therefore, the use of averaged initial profiles does not contribute to the uncertainties of the extraction of transport properties of hot and dense QCD matter based on viscous hydrodynamic calculations.Comment: 7 pages, 7 figures, minor revision of figures and conclusion, as published in PR

Directed flow in ultrarelativistic heavy-ion collisions

We study the generation of directed flow in the hydrodynamic expansion of the hot matter formed in ultrarelativistic heavy-ion collisions at 200GeV. The experimentally observed negative directed flow in a wide range of central pseudorapidities isreproduced assuming that the fireball is tilted away from the collision axis. The tilt of the source is consistent with a preferential emission in the forward/backward hemisphere from forward/backward participating nucleons. The model reproduces the experimentally observed scaling of the directed flow when going from Au-Au to Cu-Cu systems.Comment: figure adde

Fluctuation of the Initial Conditions and Its Consequences on Some Observables

We show effects of the event-by-event fluctuation of the initial conditions (IC) in hydrodynamic description of high-energy nuclear collisions on some observables. Such IC produce not only fluctuations in observables but, due to their bumpy structure, several non-trivial effects appear. They enhance production of isotropically distributed high-pT particles, making v2 smaller there. Also, they reduce v2 in the forward and backward regions where the global matter density is smaller, so where such effects become more efficacious. They may also produce the so-called ridge effect in the two large-pT particle correlation.Comment: 6 pages, 6 figures, presented at the IV Workshop on Particle Correlations and Femtoscopy (WPCF2008), Krakow, Poland, 11-14 Sep 200

Notes on <i>Chersodromia</i> from Portugal, Spain and France with the description of a new brachypterous species (Diptera, Hybotidae, Tachydromiinae)

Chersodromia squamata sp. nov. is described from Portugal and Spain. A key is given to the four known species of the Ch. curtipennis subgroup in the Ch. incana group. In addition Ch. incana Walker is re-illustrated and the species is recorded for the first time from France and Portugal. Chersodromia alata (Walker) (= Ch. difficilis Lundbeck) is also recorded for the first time from France and Spain

Gravitation and Duality Symmetry

By generalizing the Hodge dual operator to the case of soldered bundles, and working in the context of the teleparallel equivalent of general relativity, an analysis of the duality symmetry in gravitation is performed. Although the basic conclusion is that, at least in the general case, gravitation is not dual symmetric, there is a particular theory in which this symmetry shows up. It is a self dual (or anti-self dual) teleparallel gravity in which, due to the fact that it does not contribute to the interaction of fermions with gravitation, the purely tensor part of torsion is assumed to vanish. The ensuing fermionic gravitational interaction is found to be chiral. Since duality is intimately related to renormalizability, this theory may eventually be more amenable to renormalization than teleparallel gravity or general relativity.Comment: 7 pages, no figures. Version 2: minor presentation changes, references added. Accepted for publication in Int. J. Mod. Phys.