Diverging fluctuations of the Lyapunov exponents

D. P. acknowledges support by MINECO (Spain) under a Ramón y Cajal fellowship. We acknowledge support by MINECO (Spain) under Project No. FIS2014-59462-P.Peer reviewedPublisher PD

Distributed computing and farm management with application to the search for heavy gauge bosons using the ATLAS experiment at the LHC (CERN)

The Standard Model of particle physics describes the strong, weak, and electromagnetic forces between the fundamental particles of ordinary matter. However, it presents several problems and some questions remain unanswered so it cannot be considered a complete theory of fundamental interactions. Many extensions have been proposed in order to address these problems. Some important recent extensions are the Extra Dimensions theories. In the context of some models with Extra Dimensions of size about $1 TeV^{-}1$, in particular in the ADD model with only fermions confined to a D-brane, heavy Kaluza-Klein excitations are expected, with the same properties as SM gauge bosons but more massive. In this work, three hadronic decay modes of some of such massive gauge bosons, Z* and W*, are investigated using the ATLAS experiment at the Large Hadron Collider (LHC), presently under construction at CERN. These hadronic modes are more difficult to detect than the leptonic ones, but they should allow a measurement of the couplings between heavy gauge bosons and quarks. The events were generated using the ATLAS fast simulation and reconstruction MC program Atlfast coupled to the Monte Carlo generator PYTHIA. We found that for an integrated luminosity of $3 × 10^{5} pb^{-}1$ and a heavy gauge boson mass of 2 TeV, the channels Z*->bb and Z*->tt would be difficult to detect because the signal would be very small compared with the expected backgrou nd, although the significance in the case of Z*->tt is larger. In the channel W*->tb , the decay might yield a signal separable from the background and a significance larger than 5 so we conclude that it would be possible to detect this particular mode at the LHC. The analysis was also performed for masses of 1 TeV and we conclude that the observability decreases with the mass. In particular, a significance higher than 5 may be achieved below approximately 1.4, 1.9 and 2.2 TeV for Z*->bb , Z*->tt and W*->tb respectively. The LHC will start to operate in 2008 and collect data in 2009. It will produce roughly 15 Petabytes of data per year. Access to this experimental data has to be provided for some 5,000 scientists working in 500 research institutes and universities. In addition, all data need to be available over the estimated 15-year lifetime of the LHC. The analysis of the data, including comparison with theoretical simulations, requires an enormous computing power. The computing challenges that scientists have to face are the huge amount of data, calculations to perform and collaborators. The Grid has been proposed as a solution for those challenges. The LHC Computing Grid project (LCG) is the Grid used by ATLAS and the other LHC experiments and it is analised in depth with the aim of studying the possible complementary use of it with another Grid project. That is the Berkeley Open Infrastructure for Network C omputing middle-ware (BOINC) developed for the SETI@home project, a Grid specialised in high CPU requirements and in using volunteer computing resources. Several important packages of physics software used by ATLAS and other LHC experiments have been successfully adapted/ported to be used with this platform with the aim of integrating them into the LHC@home project at CERN: Atlfast, PYTHIA, Geant4 and Garfield. The events used in our physics analysis with Atlfast were reproduced using BOINC obtaining exactly the same results. The LCG software, in particular SEAL, ROOT and the external software, was ported to the Solaris/sparc platform to study it's portability in general as well. A testbed was performed including a big number of heterogeneous hardware and software that involves a farm of 100 computers at CERN's computing center (lxboinc) together with 30 PCs from CIEMAT and 45 from schools from Extremadura (Spain). That required a preliminary study, development and creation of components of the Quattor software and configuration management tool to install and manage the lxboinc farm and it also involved the set up of a collaboration between the Spanish research centers and government and CERN. The testbed was successful and 26,597 Grid jobs were delivered, executed and received successfully. We conclude that BOINC and LCG are complementary and useful kinds of Grid that can be used by ATLAS and the other LHC experiments. LCG has very good data distribution, management and storage capabilities that BOINC does not have. In the other hand, BOINC does not need high bandwidth or Internet speed and it also can provide a huge and inexpensive amount of computing power coming from volunteers. In addition, it is possible to send jobs from LCG to BOINC and vice versa. So, possible complementary cases are to use volunteer BOINC nodes when the LCG nodes have too many jobs to do or to use BOINC for high CPU tasks like event generators or reconstructions while concentrating LCG for data analysis

Existence and uniqueness of solutions of Robin's problem for the anisotropic hyperbolic heat equation with non regular data

We find existence and uniqueness results about solutions of Robin's problem for the general anisotropic hyperbolic heat equation in the case of infinitely differentiable coefficients but irregular distributions data for the internal heatsources and boundary and initial conditions.

An Active Attack on a Multiparty Key Exchange Protocol

The multiparty key exchange introduced in Steiner et al.\@ and presented in more general form by the authors is known to be secure against passive attacks. In this paper, an active attack is presented assuming malicious control of the communications of the last two users for the duration of only the key exchange

Group key management based on semigroup actions

In this work we provide a suite of protocols for group key management based on general semigroup actions. Construction of the key is made in a distributed and collaborative way. Examples are provided that may in some cases enhance the security level and communication overheads of previous existing protocols. Security against passive attacks is considered and depends on the hardness of the semigroup action problem in any particular scenario.Comment: accepted for publication in Journal of algebra and its application

Metodología de cálculo de NOx en generadores de vapor que queman gas natural

Este trabajo presenta la metodología para el cálculo de emisiones de NOx en un generador de vapor de 350 ton/h quemando gas natural y se investigan los métodos de control de NOx durante la combustión. Hoy en día es uno de los principales problemas de las plantas termoeléctricas puesto que genera un alto nivel de emisiones de óxidos de nitrógeno a la atmósfera. Esta metodología consiste en la determinación de los cuatro parámetros fundamentales que intervienen en la formación de NOx y son los siguientes: coeficiente de exceso de aire en la zona de combustión activa (ZCA) ¿ZCA, la temperatura promedio de la ZCA TZCA, el flujo de calor reflejado en ZCA qrefl ZCA y el tiempo de residencia de los gases en ZCA ¿ZCA. Para poder determinar estos parámetros se tiene que considerar la composición del gas natural, la transferencia de calor en el horno, las condiciones de funcionamiento y las dimensiones del generador de vapor, entre otros factores. Los cuatro parámetros principales se sustituyen en el polinomio experimental para el combustible en cuestión y, de esta forma, se puede determinar la emisión de NOx para los métodos de combustión que se analizarán en el presente artículo: recirculación de gases, diferentes lugares de introducción de gases de recirculación, combustión a dos etapas e inyección de agua

Cryptoanalysis of a key exchange protocol based on a congruence-simple semiring action

We show that a previously introduced key exchange based on a congruence-simple semiring action is not secure by providing an attack that reveals the shared key from the distributed public information for any of such semiring

Influence of Di erent Sieving Methods on Estimation of Sand Size Parameters

Sieving is one of the most used operational methods to determine sand size parameters which are essential to analyze coastal dynamics. However, the influence of hand versus mechanical shaking methods has not yet been studied. Herein, samples were taken from inside the hopper of a trailing suction dredger and sieved by hand with sieves of 10 and 20 cm diameters on board the dredger. Afterwards, these same samples were sieved with a mechanical shaker in the laboratory on land. The results showed di erences for the main size parameters D50, standard deviation, skewness, and kurtosis. Amongst the main results, it should be noted that the highest values for D50 and kurtosis were given by the small sieves method. On the other hand, the lowest values were given by the mechanical shaker method in the laboratory. Furthermore, standard deviation and skewness did not seem to be a ected by the sieving method which means that all the grainsize distribution was shifted but the shape remained unchanged. The few samples that do not follow these patterns have a higher percentage of shells. Finally and definitely, the small sieves should be rejected as a sieving method aboard