VACUUM POLARIZATION EFFECTS ON QUASINORMAL MODES IN ELECTRICALLY CHARGED BLACK HOLE SPACE-TIMES

We investigate the influence of vacuum polarization of quantum massive fields on the scalar sector of quasinormal modes in spherically symmetric black holes. We consider the evolution of a massless scalar field on the space-time corresponding to a charged semiclassical black hole, consisting of the quantum-corrected geometry of a Reissner-Nordstrom black hole dressed by a quantum massive scalar field in the large mass limit. Using a sixth order WKB approach we find a shift in the quasinormal mode frequencies due to vacuum polarization.

Gravitational field of a straight cosmic string in the framework of higher-derivative gravity

The gravitational properties of a straight cosmic string are studied in the linear approximation of higher-derivative gravity. These properties are shown to be very different from those found using linearized Einstein gravity: there exists a short range gravitational (anti-gravitational) force in the nonrelativistic limit; in addition, the derection angle of a light ray moving in a plane orthogonal to the string depends on the impact parameter.

FAST, PARALLEL AND SECURE CRYPTOGRAPHY ALGORITHM USING LORENZ`S ATTRACTOR

A novel cryptography method based on the Lorenz`s attractor chaotic system is presented. The proposed algorithm is secure and fast, making it practical for general use. We introduce the chaotic operation mode, which provides an interaction among the password, message and a chaotic system. It ensures that the algorithm yields a secure codification, even if the nature of the chaotic system is known. The algorithm has been implemented in two versions: one sequential and slow and the other, parallel and fast. Our algorithm assures the integrity of the ciphertext (we know if it has been altered, which is not assured by traditional algorithms) and consequently its authenticity. Numerical experiments are presented, discussed and show the behavior of the method in terms of security and performance. The fast version of the algorithm has a performance comparable to AES, a popular cryptography program used commercially nowadays, but it is more secure, which makes it immediately suitable for general purpose cryptography applications. An internet page has been set up, which enables the readers to test the algorithm and also to try to break into the cipher.

CALCULATION OF MAGNETODONOR STATES IN InP AND POLARON EFFECTS

Far-infrared transitions in polar semiconductors are known to be affected by the presence of shallow donor impurities, external magnetic fields and the electron-LO-phonon interaction. We calculate the magnetodonor states in indium phosphide by a diagonalization procedure, and introduce the electron-phonon interaction by the Frohlich term. The main effects of this perturbation are calculated by a multi-level version of the Wigner-Brillouin theory. We determine the transition energies, from the ground state to excited states, and find good qualitative agreement with recently reported absorption-spectroscopy measurements in the 100-800 cm(-1) range, with applied magnetic fields up to 30 T. Our calculations suggest that experimental peak splittings in the 400-450 cm(-1) range are due to the electron-phonon interaction.

On the effects of geographical constraints on task execution in complex

In the present work, the effects of spatial constraints on the efficiency of task execution in systems underlain by geographical complex networks are investigated, where the probability of connection decreases with the distance between the nodes. The investigation considers several configurations of the parameters defining the network connectivity, and the Barabasi-Albert network model is also considered for comparisons. The results show that the effect of connectivity is significant only for shorter tasks, the locality of connection simplied by the spatial constraints reduces efficiency, and the addition of edges can improve the efficiency of the execution, although with increasing locality of the connections the improvement is small.

Complex networks analysis of manual and machine translations

Complex networks have been increasingly used in text analysis, including in connection with natural language processing tools, as important text features appear to be captured by the topology and dynamics of the networks. Following previous works that apply complex networks concepts to text quality measurement, summary evaluation, and author characterization, we now focus on machine translation (MT). In this paper we assess the possible representation of texts as complex networks to evaluate cross-linguistic issues inherent in manual and machine translation. We show that different quality translations generated by NIT tools can be distinguished from their manual counterparts by means of metrics such as in-(ID) and out-degrees (OD), clustering coefficient (CC), and shortest paths (SP). For instance, we demonstrate that the average OD in networks of automatic translations consistently exceeds the values obtained for manual ones, and that the CC values of source texts are not preserved for manual translations, but are for good automatic translations. This probably reflects the text rearrangements humans perform during manual translation. We envisage that such findings could lead to better NIT tools and automatic evaluation metrics.

Active galactic nuclei: sources for ultra high energy cosmic rays

Ultra high energy cosmic ray events presently show a spectrum, which we interpret here as galactic cosmic rays due to a starburst, in the radio galaxy Cen A which is pushed up in energy by the shock of a relativistic jet. The knee feature and the particles with energy immediately higher in galactic cosmic rays then turn into the bulk of ultra high energy cosmic rays. This entails that all ultra high energy cosmic rays are heavy nuclei. This picture is viable if the majority of the observed ultra high energy events come from the radio galaxy Cen A, and are scattered by intergalactic magnetic fields across much of the sky.

EXACT AND APPROXIMATE RELATIONS FOR THE SPIN-DEPENDENCE OF THE EXCHANGE ENERGY IN HIGH MAGNETIC FIELDS

The exchange energy of an arbitrary collinear-spin many-body system in an external magnetic field is a functional of the spin-resolved charge and current densities, E(x)[n(up arrow), n(down arrow), j(up arrow), j(down arrow)]. Within the framework of density-functional theory (DFT), we show that the dependence of this functional on the four densities can be fully reconstructed from either of two extreme limits: a fully polarized system or a completely unpolarized system. Reconstruction from the limit of an unpolarized system yields a generalization of the Oliver-Perdew spin scaling relations from spin-DFT to current-DFT. Reconstruction from the limit of a fully polarized system is used to derive the high-field form of the local-spin-density approximation to current-DFT and to magnetic-field DFT.

NONPERTURBATIVE HQET AT ORDER 1/m

We summarize the first results for masses and decay constants of bottom-strange (pseudo-scalar and vector) mesons from nonperturbatively renormalized heavy-quark effective theory (HQET), using lattice-QCD simulations in the quenched approximation.

SPECTRUM OF SCREENING MASSES FOR SU(2) GAUGE THEORY: UNIVERSALITY CLASS

In this work we study the spectrum of the lowest screening masses for Yang-Mills theories on the lattice. We used the SU(2) gauge group in (3 + 1) dmensions. We adopted the multiple exponential method and the so-called ""variational"" method, in order to detect possible excited states. The calculations were done near the critical temperature of the confinement-deconfinement phase transition. We obtained values for the ratios of the screening masses consistent with predictions from universality arguments. A Monte Carlo evolution of the screening masses in the gauge theory confirms the validity of the predictions.

ON AMINO ACID AND CODON ASSIGNMENT IN ALGEBRAIC MODELS FOR THE GENETIC CODE

We give a list of all possible schemes for performing amino acid and codon assignments in algebraic models for the genetic code, which are consistent with a few simple symmetry principles, in accordance with the spirit of the algebraic approach to the evolution of the genetic code proposed by Hornos and Hornos. Our results are complete in the sense of covering all the algebraic models that arise within this approach, whether based on Lie groups/Lie algebras, on Lie superalgebras or on finite groups.

La noción de lo esencial en la enseñanza de lenguas modernas según los profesores. : Entrevistas con cinco profesores sobre la norma "Todo lo esencial de la enseñanza debe realizarse en la lengua meta" de Gy11.

La tesina investiga cómo cinco profesores interpretan la norma de Gy11 que indica que todo lo esencial de la enseñanza de lenguas modernas debe realizarse en la lengua meta. Las entrevistas semiestructuradas indican que los profesores interpretan la norma de maneras parecidas, es decir, que los profesores deben usar la lengua meta lo máximo posible en la enseñanza. La mayoría de los profesores están de acuerdo con la norma, sin embargo, tienen varias críticas contra Skolverket y la formulación de la norma. Ninguno de los profesores ha cambiado su uso de la lengua meta en el aula debido a la norma.

A doorway to Borromean halo nuclei: the Samba configuration

We exploit the possibility of new configurations in three-body halo nuclei, Samba type (the neutron-core form a bound system) as a doorway to Borromean systems. The nuclei Be-12, B-15, N-23 and F-27 are of such nature, in particular N-23 with a half-life of 37.7 s and a halo radius of 6.07 fm is an excellent example of Samba-halo configuration. The fusion below the barrier of the Samba halo nuclei with heavy targets could reveal the so far elusive enhancement and a dominance of one-neutron over two-neutron transfers, in contrast to what was found recently for the Borromean halo nucleus He-6 + U-238.

Adelle de Oliveira: trajetória de vida e prática Pedagógica (1900-1940)

This work analyses pedagogical practices of Adelle Sobral de Oliveira, from 1900 to 1940, in order to notice how her performance as educator and administrator took place in Externato Angelo Varela in the Rio Grande do Norte city of Ceará-Mirim within a time in which the public teaching started to be considered modern in the State. Adelle was a self learner who developed an important role as a mentality mentor of a generation in the region. As the research corpus we have taken the five Reading Books written by Felisberto de Carvalho used by Adelle in her Externato, interviews with her ex-students and researches in the newspapers of her time, in the Public Archives and in the Historical and Geographic Institute of Rio Grande do Norte, and also in the governors messages, Education Department documents such as laws, and government decrees and acts. It was also taken as a research font the Publich Archives of Ceará-Mirim. The aim of this PhD thesis is understand the primary instruction spreading and modernization in the countryside of Rio Grande do Norte, which began with her teaching pedagogical practices. The research results show Adele Oliveira used practical and experimental modern methodological teaching methods in the subjects she taught. Due to this, in her scholar routine, she avoided physical punishment and mechanical teaching and learning strategies

Ensino de Entropia: um enfoque histórico e epistemológico.

The rational construction necessary to systematize scientific knowledge in physics, introduces difficulties of understanding in some of its concepts. One of these concepts which exemplify properly this difficulty in learning or teaching is entropy. This thesis propose the construction of a didactic route which constitute itself a historical and epistemological course to entropy, intending to contribute for teaching this concept as well as other physics concepts. The basic assumption to build this route is that through the historical review of the development of this concept in the way suggested by Bachelard s (1884-1962) epistemology it is possible to make subjects, to be taught and learned, more meaningful. Initially I composed a brief biographical note to give the reader an idea about the issues, interests and reflections, related to science, and how I dealt with them in my private and professional life, as well as the role they played to lead me to write this thesis. The strategy to construct the route to entropy was to split the usual contents of basic thermodynamics in three moments in a way they can constitute epistemological units , which can be identified by the way of thinking in the corresponding moments of scientific knowledge production: a technical and empiricist moment, a rationalist and positivist moment and a post-positivist rationalist one. The transition between each moment is characterized by a rupture with the former way of thinking; however the progress in the construction of knowledge in the area is evident. As the final part of this work I present an analysis based on elements of Bachelard s epistemology that are present in each moment. This analysis is the basic component of the didactic route that I propose myself to build. The way I made this route guide to entropy could contribute to the construction of other didactic routes in physics and other sciences, in a way to unveil hidden meanings and as a tool to humanize scientific knowledge.