Cosmological term and fundamental physics

A nonvanishing cosmological term in Einstein's equations implies a nonvanishing spacetime curvature even in the absence of any kind of matter. It would, in consequence, affect many of the underlying kinematic tenets of physical theory. The usual commutative spacetime translations of the Poincare group would be replaced by the mixed conformal translations of the de Sitter group, leading to obvious alterations in elementary concepts such as time, energy and momentum. Although negligible at small scales, such modifications may come to have important consequences both in the large and for the inflationary picture of the early Universe. A qualitative discussion is presented, which suggests deep changes in Hamiltonian, Quantum and Statistical Mechanics. In the primeval universe as described by the standard cosmological model, in particular, the equations of state of the matter sources could be quite different from those usually introduced.

IS PHYSICS ASKING FOR A NEW KINEMATICS?

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Performance of an operating high energy physics data grid: DOSAR-Grid

The DO experiment at Fermilab's Tevatron will record several petabytes of data over the next five years in pursuing the goals of understanding nature and searching for the origin of mass. Computing resources required to analyze these data far exceed capabilities of any one institution. Moreover, the widely scattered geographical distribution of DO collaborators poses further serious difficulties for optimal use of human and computing resources. These difficulties will exacerbate in future high energy physics experiments, like the LHC. The computing grid has long been recognized as a solution to these problems. This technology is being made a more immediate reality to end users in DO by developing a grid in the DO Southern Analysis Region (DOSAR), DOSAR-Grid, using a available resources within it and a home-grown local task manager, McFarm. We will present the architecture in which the DOSAR-Grid is implemented, the use of technology and the functionality of the grid, and the experience from operating the grid in simulation, reprocessing and data analyses for a currently running HEP experiment.

Flavor physics in warped space

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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.

A diversidade de interpretações como fator constituinte da formação docente: leitura e observação

Neste artigo apresentamos a análise de interpretações de estudantes em trabalhos desenvolvidos em duas disciplinas de cursos de Licenciatura em Física, nas quais realizamos atividades bastante distintas, uma envolvendo a leitura e outra a observação pelos licenciandos. Buscamos compreender falas escritas pelos estudantes como parte dessas atividades, e procuramos evidenciar a diversidade de interpretações e a relevância desse trabalho para a formação inicial. O apoio teórico em que nos sustentamos foi a análise de discurso na vertente originada na França por Michel Pêcheux. A consideração da não transparência da linguagem, e as noções de condições de produção, memória discursiva e repetição, bem como alguns aportes sobre possíveis papéis da observação na construção científica, contribuíram para a compreensão de discursos escritos pelos estudantes. Mostramos a diversidade de interpretações dos licenciados: ao opinarem sobre a possibilidade ou não de se trabalhar a física moderna e contemporânea no ensino médio, depois de lerem um texto envolvendo esse tema, e ao redigirem um texto sobre a observação na pesquisa científica.

BOUND HYDROGENIC STATES IN A MAGNETIC FIELD: A FINITE-DIFFERENCE APPROACH

A finite-difference scheme is used to calculate bound electronic states of an electron in a hydrogen atom subject to a magnetic field. The numerical results are in good agreement with exact results, in the absence of the magnetic field, and with a two-parameters variational calculation, when the magnetic field is applied.

Civilização, sexualidade e entropia no pensamento de Freud

This article intends to offer, in an introductory way, a reflection in order to build an interpretation of the Sigmund Freud's thought, orchestrating notions such as the ones of progress of civilization, which would be his philosophy of history; an investigation on his conceptions about "human nature"; culminating in a brief reflection on some points of philosophy of nature that underlies his thought. We anticipate that we recognize in the latter, characteristics assimilated by analogy to the entropy concept of modern physics. Among other features, such as compared and methodological reference with some of Kant's theses about the same notions, we also present in a short way two metapsychological aspects of Freudian theory on human sexuality, the biological and physiological, both aiming to give support to the reflections on the sense of finality.

Effects of a mixed vector-scalar screened coulomb potential for spinless particles

The problem of a spinless particle subject to a general mixing of vector and scalar screened Coulomb potentials in a two-dimensional world is analyzed and its bounded solutions are found. Some unusual results, including the existence of a bona fide solitary zero-eigenmode solution, are revealed for the Klein-Gordon equation. The cases of pure vector and scalar potentials, already analyzed in previous works, are obtained as particular cases.

Unified treatment of mixed vector-scalar screened Coulomb potentials for fermions

The problem of a fermion subject to a general mixing of vector and scalar screened Coulomb potentials in a two-dimensional world is analyzed and quantization conditions are found.

The Jacobi identity for Dirac-like brackets

For redundant second-class constraints the Dirac brackets cannot be defined and new brackets must be introduced. We prove here that the Jacobi identity for the new brackets must hold on the surface of the second-class constraints. In order to illustrate our proof we work out explicitly the cases of a fractional spin particle in 2 + 1 dimensions and the original Brink-Schwarz massless superparticle in D = 10 dimensions in a Lorentz-covariant constraints separation.

The peremptory influence of a uniform background for trapping neutral fermions with an inversely linear potential

The problem of neutral fermions subject to an inversely linear potential is revisited. It is shown that an infinite set of bound-state solutions can be found on the condition that the fermion is embedded in an additional uniform background potential. An apparent paradox concerning the uncertainty principle is solved by introducing the concept of effective Compton wavelength.

Relativistic effects of mixed vector-scalar-pseudoscalar potentials for fermions in 1+1 dimensions

The problem of fermions in the presence of a pseudoscalar plus a mixing of vector and scalar potentials which have equal or opposite signs is investigated. We explore all the possible signs of the potentials and discuss their bound-state solutions for fermions and antifermions. The cases of mixed vector and scalar Poschl-Teller-like and pseudoscalar kink-like potentials, already analyzed in previous works, are obtained as particular cases.

IMPEDANCE CHARACTERISTICS of La3/2Bi3/2Fe5O12 CERAMICS

Polycrystalline La3/2Bi3/2Fe5O12 (LBIO) compound was prepared by a high-temperature solid-state reaction technique. The complex impedance of LBIO was measured over a wide temperature (i.e., room temperature to 500 C) and frequencies (i.e., 10(2)-10(6) Hz) ranges. This study takes advantage of plotting ac data simultaneously in the form of impedance and modulus spectroscopic plots and obey non-Debye type of relaxation process. The Nyquist's plot showed the presence of grain effects in the material at high temperature. The ac conductivity spectrum was found to obey Jonscher's universal power law. The dc conductivity was found to increase with rise in temperature. The activation energy of the compound was found to be 0.24 and 0.51 eV in the low and high-temperature region, respectively, for conduction process.

PHYSICAL PROPERTIES of TELLURITE GLASSES PREPARED UNDER DIFFERENT THERMAL HISTORIES

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)