Pushing the Prize Up, A Few Notes on Al-Qaeda's Reward Structure and the choice of Casualties

The article aims at suggesting possible conjectures on Al-Qaeda's logic and structure. Even if the organization's secrecy makes any empirical evidence difficult to find, some insight can be provided by economic theory of contests: in this terms, Al-Qaeda can be acknowledged like an agent rewarding a prize (membership) to its clients (cells and would-be cells). Although this principle makes the organization hardly visible and virtually impenetrable, we contend that in the long term such a logic is non-sustainableConflict, Al Qaeda, Terrorism, microeconomic theory, prize, contest

3+1D Massless Weyl spinors from bosonic scalar-tensor duality

We consider the fermionization of a bosonic free theory characterized by the 3+1D scalar - tensor duality. This duality can be interpreted as the dimensional reduction, via a planar boundary, of the 4+1D topological BF theory. In this model, adopting the Sommerfield tomographic representation of quantized bosonic fields, we explicitly build a fermionic operator and its associated Klein factor such that it satisfies the correct anticommutation relations. Interestingly, we demonstrate that this operator satisfies the massless Dirac equation and that it can be identified with a 3+1D Weyl spinor. Finally, as an explicit example, we write the integrated charge density in terms of the tomographic transformed bosonic degrees of freedom

Olami-Feder-Christensen Model on different Networks

We investigate numerically the Self Organized Criticality (SOC) properties of the dissipative Olami-Feder-Christensen model on small-world and scale-free networks. We find that the small-world OFC model exhibits self-organized criticality. Indeed, in this case we observe power law behavior of earthquakes size distribution with finite size scaling for the cut-off region. In the scale-free OFC model, instead, the strength of disorder hinders synchronization and does not allow to reach a critical state.Comment: To appear in the Proceedings of 3rd NEXT International Conference "News Expectations and Trends in Statistical Physics" (13-18 August 2005, Kolimbari - Crete, Greece), as a special issue of the European Journal of Physics B and of the Physica A, by G. Kaniadakis, A. Carbone, M. Lissi

Holography in flat spacetime: 4D theories and electromagnetic duality on the border

We consider a free topological model in 5D euclidean flat spacetime, built from two rank-2 tensor fields. Despite the fact that the bulk of the model does not have any particular physical interpretation, on its 4D planar edge nontrivial gauge field theories are recovered, whose features are entirely determined by the gauge and discrete symmetries of the bulk. In particular no 4D dynamics can be obtained without imposing a Time Reversal invariance in the bulk. Remarkably, one of the two possible edge models selected by the Time Reversal symmetries displays a true electromagnetic duality, which relates strong and weak coupling regimes. Moreover this same model, when considered on-shell, coincides with the Maxwell theory, which therefore can be thought of as a 4D boundary theory of a seemingly harmless 5D topological model.Comment: 21 pages, plain LaTeX, no figures. Version to appear on JHE

Duality and Dimensional Reduction of 5D BF Theory

A planar boundary introduced \`a la Symanzik in the 5D topological BF theory, with the only requirement of locality and power counting, allows to uniquely determine a gauge invariant, non topological 4D Lagrangian. The boundary condition on the bulk fields is interpreted as a duality relation for the boundary fields, in analogy with the fermionization duality which holds in the 3D case. This suggests that the 4D degrees of freedom might be fermionic, although starting from a bosonic bulk theory. The method we propose to dimensionally reduce a Quantum Field Theory and to identify the resulting degrees of freedom can be applied to a generic spacetime dimension.Comment: 13 pages, plain LaTeX, version to appear on EPJ

Fast Escape from Quantum Mazes in Integrated Photonics

Escaping from a complex maze, by exploring different paths with several decision-making branches in order to reach the exit, has always been a very challenging and fascinating task. Wave field and quantum objects may explore a complex structure in parallel by interference effects, but without necessarily leading to more efficient transport. Here, inspired by recent observations in biological energy transport phenomena, we demonstrate how a quantum walker can efficiently reach the output of a maze by partially suppressing the presence of interference. In particular, we show theoretically an unprecedented improvement in transport efficiency for increasing maze size with respect to purely quantum and classical approaches. In addition, we investigate experimentally these hybrid transport phenomena, by mapping the maze problem in an integrated waveguide array, probed by coherent light, hence successfully testing our theoretical results. These achievements may lead towards future bio-inspired photonics technologies for more efficient transport and computation.Comment: 13 pages, 10 figure

Extensive nonadditive entropy in quantum spin chains

We present details on a physical realization, in a many-body Hamiltonian system, of the abstract probabilistic structure recently exhibited by Gell-Mann, Sato and one of us (C.T.), that the nonadditive entropy $S_q=k [1- Tr \hat{\rho}^q]/[q-1]$ ($\hat{\rho}\equiv$ density matrix; $S_1=-k Tr \hat{\rho} \ln \hat{\rho}$) can conform, for an anomalous value of q (i.e., q not equal to 1), to the classical thermodynamical requirement for the entropy to be extensive. Moreover, we find that the entropic index q provides a tool to characterize both universal and nonuniversal aspects in quantum phase transitions (e.g., for a L-sized block of the Ising ferromagnetic chain at its T=0 critical transverse field, we obtain $\lim_{L\to\infty}S_{\sqrt{37}-6}(L)/L=3.56 \pm 0.03$). The present results suggest a new and powerful approach to measure entanglement in quantum many-body systems. At the light of these results, and similar ones for a d=2 Bosonic system discussed by us elsewhere, we conjecture that, for blocks of linear size L of a large class of Fermionic and Bosonic d-dimensional many-body Hamiltonians with short-range interaction at T=0, we have that the additive entropy $S_1(L) \propto [L^{d-1}-1]/(d-1)$ (i.e., $\ln L$ for $d=1$, and $L^{d-1}$ for d>1), hence it is not extensive, whereas, for anomalous values of the index q, we have that the nonadditive entropy $S_q(L)\propto L^d$ ($\forall d$), i.e., it is extensive. The present discussion neatly illustrates that entropic additivity and entropic extensivity are quite different properties, even if they essentially coincide in the presence of short-range correlations.Comment: 9 pages, 4 figures, Invited Paper presented at the international conference CTNEXT07, satellite of STATPHYS23, 1-5 July 2007, Catania, Ital

Self-Organized Criticality and earthquakes

We discuss recent results on a new analysis regarding models showing Self-Organized Criticality (SOC), and in particular on the OFC one. We show that Probability Density Functions (PDFs) for the avalanche size differences at different times have fat tails with a q-Gaussian shape. This behavior does not depend on the time interval adopted and it is also found when considering energy differences between real earthquakes.Comment: 4 pages, Paper presented at the international conference CTNEXT07, satellite of STATPHYS23, 1-5 july 2007, Catania, Italy http://www.ct.infn.it/ctnext07

Ottimizzazione di Traiettorie Interplanetarie con Manovre Impulsive

In questa Tesi viene presentato un procedimento di ottimizzazione di traiettorie interplanetarie di veicoli spaziali nel caso di alcune missioni spaziali. Viene mostrato un modello che, a partire da un set di parametri che definiscono univocamente la traiettoria del veicolo, permette di calcolare la variazione totale di velocita' ottenuta dalla sonda che e' legata al consumo di propellente necessario a eseguire tutte le manovre della missione spaziale. La sonda puo' eseguire manovre impulsive e puo' sfruttare l'azione gravitazionale dei pianeti del Sistema Solare per effettuare manovre di fionda gravitazionale. Il problema di ottimizzazione viene risolto utilizzando l'Algoritmo Genetico e MultiStart di MATLAB. Vengono affrontati problemi bidimensionali e tridimensionali che fanno uso delle effemeridi planetarie. I risultati sono comparati con le soluzioni ottime gia' note in letteratura