Production of exotic charmonium in γγ\gamma \gamma interactions at hadronic colliders

In this paper we investigate the Exotic Charmonium (EC) production in $\gamma \gamma$ interactions present in proton-proton, proton-nucleus and nucleus-nucleus collisions at the CERN Large Hadron Collider (LHC) energies as well as for the proposed energies of the Future Circular Collider (FCC). Our results demonstrate that the experimental study of these processes is feasible and can be used to constrain the theoretical decay widths and shed some light on the configuration of the considered multiquark states.Comment: 7 pages, 2 figures, 3 tables. v2: Revised version published in Physical Review

Dynamical reentrance and geometry imposed quantization effects in Nb-AlOx-Nb Josephson junction arrays

In this paper, we report on different phenomena related to the magnetic properties of artificially prepared highly ordered (periodic) two-dimensional Josephson junction arrays (2D-JJA) of both shunted and unshunted Nb-AlOx-Nb tunnel junctions. By employing mutual-inductance measurements and using a high-sensitive bridge, we have thoroughly investigated (both experimentally and theoretically) the temperature and magnetic field dependence of complex AC susceptibility of 2D-JJA. We also demonstrate the use of the scanning SQUID microscope for imaging the local flux distribution within our unshunted arrays

String-like brane splitting in the context of f(T,B)f(T,B) gravity

In this work, the influence of the boundary term $B$ is analyzed in a string-like thick brane scenario in the gravity context $f(T, B)$. For that, three models of $f(T, B)$ are proposed, i.e., $f_1(T, B)=T+k{B}^{n}$, $f_2(T, B)=T+k(-T+B)^{n}$ and $f_3(T, B)=T+k_1T^2+k_2{B}^2$, where $n$, $k$ and $k_{1,2}$ are parameters that control the deviation from the usual teleparallelism. The first relevant result obtained was the appearance of a super-located tower in the core for energy density. Furthermore, the greater the influence of the boundary term, the new maximums and minimums appear in the energy density. All this indicates the emergence of capable structures from split to the brane. The second relevant result was obtained by analyzing the gravitational perturbations, where the effective potential presents the supersymmetric form of quantum mechanics, leading to well-localized massless modes.Comment: 18 pages, 7 captioned figure

Comparação dos níveis de ácido cianídrico (HCN) entre etnovariedades de mandiocas bravas e mansas.

Disponível também on-line. Publicado também no Anais do XII Congresso Brasileiro da Mandioca, Paranavaí, 2007

A Hamiltonian approach for explosive percolation

We introduce a cluster growth process that provides a clear connection between equilibrium statistical mechanics and an explosive percolation model similar to the one recently proposed by Achlioptas et al. [Science 323, 1453 (2009)]. We show that the following two ingredients are essential for obtaining an abrupt (first-order) transition in the fraction of the system occupied by the largest cluster: (i) the size of all growing clusters should be kept approximately the same, and (ii) the inclusion of merging bonds (i.e., bonds connecting vertices in different clusters) should dominate with respect to the redundant bonds (i.e., bonds connecting vertices in the same cluster). Moreover, in the extreme limit where only merging bonds are present, a complete enumeration scheme based on tree-like graphs can be used to obtain an exact solution of our model that displays a first-order transition. Finally, the proposed mechanism can be viewed as a generalization of standard percolation that discloses an entirely new family of models with potential application in growth and fragmentation processes of real network systems.Comment: 4 pages, 4 figure

Universal reduction of pressure between charged surfaces by long-wavelength surface charge modulation

We predict theoretically that long-wavelength surface charge modulations universally reduce the pressure between the charged surfaces with counterions compared with the case of uniformly charged surfaces with the same average surface charge density. The physical origin of this effect is the fact that surface charge modulations always lead to enhanced counterion localization near the surfaces, and hence, fewer charges at the midplane. We confirm the last prediction with Monte Carlo simulations.Comment: 8 pages 1 figure, Europhys. Lett., in pres

Morphological transition between diffusion-limited and ballistic aggregation growth patterns

In this work, the transition between diffusion-limited and ballistic aggregation models was revisited using a model in which biased random walks simulate the particle trajectories. The bias is controlled by a parameter $\lambda$, which assumes the value $\lambda=0$ (1) for ballistic (diffusion-limited) aggregation model. Patterns growing from a single seed were considered. In order to simulate large clusters, a new efficient algorithm was developed. For $\lambda \ne 0$, the patterns are fractal on the small length scales, but homogeneous on the large ones. We evaluated the mean density of particles $\bar{\rho}$ in the region defined by a circle of radius $r$ centered at the initial seed. As a function of $r$, $\bar{\rho}$ reaches the asymptotic value $\rho_0(\lambda)$ following a power law $\bar{\rho}=\rho_0+Ar^{-\gamma}$ with a universal exponent $\gamma=0.46(2)$, independent of $\lambda$. The asymptotic value has the behavior $\rho_0\sim|1-\lambda|^\beta$, where $\beta= 0.26(1)$. The characteristic crossover length that determines the transition from DLA- to BA-like scaling regimes is given by $\xi\sim|1-\lambda|^{-\nu}$, where $\nu=0.61(1)$, while the cluster mass at the crossover follows a power law $M_\xi\sim|1 -\lambda|^{-\alpha}$, where $\alpha=0.97(2)$. We deduce the scaling relations \beta=\n u\gamma and $\beta=2\nu-\alpha$ between these exponents.Comment: 7 pages, 8 figure

Vacuum polarization on the spinning circle

Vacuum polarization of a massive scalar field in the background of a two-dimensional version of a spinning cosmic string is investigated. It is shown that when the `radius of the universe' is such that spacetime is globally hyperbolic the vacuum fluctuations are well behaved, diverging though on the `chronology horizon'. Naive use of the formulae when spacetime is nonglobally hyperbolic leads to unphysical results. It is also pointed out that the set of normal modes used previously in the literature to address the problem gives rise to two-point functions which do not have a Hadamard form, and therefore are not physically acceptable. Such normal modes correspond to a locally (but not globally) Minkowski time, which appears to be at first sight a natural choice of time to implement quantization.Comment: 3 pages, no figures, REVTeX4, published versio