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Search Results: 1 - 10 of 452398 matches for " J. G. Pereira "
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A Study of Climate Variability in Papua New Guinea  [PDF]
F. B. Pereira, O. Renagi, J. J. Panakal, G. Anduwan
Journal of Geoscience and Environment Protection (GEP) , 2019, DOI: 10.4236/gep.2019.75005
This Papua New Guinea is nearly tropical and we get rain in almost all seasons. But over the past few decades, it was observed that climate is changing considerably. Changes in solar influx, frequent volcanic eruptions and greenhouse gas emissions aggravate this effect. In this scenario, climate variability in Papua New Guinea has been studied using atmospheric parameters like atmospheric temperature and rainfall published by Bureau of Meteorology, Australia for the period 1996-2018. In order to improve the forecast of climate variability, the data has been analyzed using wavelet methods. An increasing trend of atmospheric temperature and rainfall are observed with a yearly periodicity except 2007-2009. The night-time atmospheric temperature showed quasi-periodic variations of two-to-four years. These variations will be discussed in terms of the SOI variations, volcanic eruptions and increase in greenhouse gas emissions.
Teleparallelism: A New Insight Into Gravity
J. G. Pereira
Physics , 2013, DOI: 10.1007/978-3-642-41992-8_11
Abstract: Teleparallel gravity, a gauge theory for the translation group, turns up as fully equivalent to Einstein's general relativity. In spite of this equivalence, it provides a whole new insight into gravitation. It breaks several paradigms related to the geometric approach of general relativity, and introduces new concepts in the description of the gravitational interaction. The purpose of this chapter is to explore some of these concepts, as well as discuss possible consequences for gravitation, mainly those that could be relevant for the quantization of the gravitational field.
Gravitational waves: a foundational review
J. G. Pereira
Physics , 2013,
Abstract: The standard linear approach to the gravitational waves theory is critically reviewed. Contrary to the prevalent understanding, it is pointed out that this theory contains many conceptual and technical obscure issues that require further analysis.
In Search of the Spacetime Torsion
J. G. Pereira
Physics , 2007,
Abstract: Whether torsion plays or not a role in the description of the gravitational interaction is a problem that can only be solved by experiment. This is, however, a difficult task: since there are different possible interpretations for torsion, there is no a model-independent way to look for it. In these notes, two different possibilities will be reviewed, their consistency analyzed, and the corresponding experimental outputs briefly discussed.
Lorentz Connections and Gravitation
J. G. Pereira
Physics , 2012, DOI: 10.1063/1.4756972
Abstract: The different roles played by Lorentz connections in general relativity and in teleparallel gravity are reviewed. Some of the consequences of this difference are discussed.
Is Physics Asking for a New Kinematics?
R. Aldrovandi,J. G. Pereira
Physics , 2008, DOI: 10.1142/S0218271808013972
Abstract: It is discussed whether some of the consistency problems of present-day physics could be solved by replacing special relativity, whose underlying kinematics is ruled by the Poincare' group, by de Sitter relativity, with underlying kinematics ruled by the de Sitter group. In contrast to ordinary special relativity, which seems to fail at the Planck scale, this new relativity is "universal" in the sense that it holds at all energy scales.
The Case for a Gravitational de Sitter Gauge Theory
R. Aldrovandi,J. G. Pereira
Physics , 1996,
Abstract: With the exception of gravitation, the known fundamental interactions of Nature are mediated by gauge fields. A comparison of the candidate groups for a gauge theory possibly describing gravitation favours the Poincar\'e group as the obvious choice. This theory gives Einstein's equations in a particular case, and Newton's law in the static non-relativistic limit, being seemingly sound at the classical level. But it comes out that it is not quantizable. The usual procedure of adding counterterms to make it a consistent and renormalizable theory leads to two possible theories, one for each of the two de Sitter groups, SO(4,1) and SO(3,2). The consequences of changing from the Poincar\'e to the de Sitter group, as well as the positive aspects, perspectives and drawbacks of the resulting theory are discussed.
De Sitter Special Relativity: Effects on Cosmology
R. Aldrovandi,J. G. Pereira
Physics , 2008, DOI: 10.1134/S020228930904001X
Abstract: The main consequences of de Sitter Special Relativity to the Standard Cosmological Model of Physical Cosmology are examined. The cosmological constant Lambda appears, in this theory, as a manifestation of the proper conformal current, which must be added to the usual energy-momentum density. As that conformal current itself vanishes in absence of sources, Lambda is ultimately dependent on the matter content, and can in principle be calculated. A present-day value very close to that given by the crossed supernova/BBR data is obtained through simple and reasonable approximations. Also a primeval inflation of polynomial type is found, and the usual notion of co-moving observer is slightly modified.
de Sitter Relativity: a New Road to Quantum Gravity?
R. Aldrovandi,J. G. Pereira
Physics , 2007, DOI: 10.1007/s10701-008-9258-5
Abstract: The Poincare' group generalizes the Galilei group for high-velocity kinematics. The de Sitter group is assumed to go one step further, generalizing Poincare' as the group governing high-energy kinematics. In other words, ordinary special relativity is here replaced by de Sitter relativity. In this theory, the cosmological constant is no longer a free parameter, and can be determined in terms of other quantities. When applied to the whole universe, it is able to predict the value of the cosmological constant and to explain the cosmic coincidence. When applied to the propagation of ultra-high energy photons, it gives a good estimate of the time delay observed in extragalactic gamma-ray flares. It can, for this reason, be considered a new paradigm to approach the quantum gravity problem.
Gravitation: in search of the missing torsion
R. Aldrovandi,J. G. Pereira
Physics , 2008,
Abstract: A linear Lorentz connection has always two fundamental derived characteristics: curvature and torsion. The latter is assumed to vanish in general relativity. Three gravitational models involving non-vanishing torsion are examined: teleparallel gravity, Einstein-Cartan, and new general relativity. Their dependability is critically examined. Although a final answer can only be given by experience, it is argued that teleparallel gravity provides the most consistent approach.
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