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Some Implications of the Cosmological Constant to Fundamental Physics
In the presence of a cosmological constant, ordinary Poincare' special
relativity is no longer valid and must be replaced by a de Sitter special
relativity, in which Minkowski space is replaced by a de Sitter spacetime. In
consequence, the ordinary notions of energy and momentum change, and will
satisfy a different kinematic relation. Such a theory is a different kind of a
doubly special relativity. Since the only difference between the Poincare' and
the de Sitter groups is the replacement of translations by certain linear
combinations of translations and proper conformal transformations, the net
result of this change is ultimately the breakdown of ordinary translational
invariance. From the experimental point of view, therefore, a de Sitter special
relativity might be probed by looking for possible violations of translational
invariance. If we assume the existence of a connection between the energy scale
of an experiment and the local value of the cosmological constant, there would
be changes in the kinematics of massive particles which could hopefully be
detected in high-energy experiments. Furthermore, due to the presence of a
horizon, the usual causal structure of spacetime would be significantly
modified at the Planck scale.Comment: 15 pages, lecture presented at the "XIIth Brazilian School of
Cosmology and Gravitation", Mangaratiba, Rio de Janeiro, September 10-23,
200
Cosmological Term and Fundamental Physics
A nonvanishing cosmological term in Einstein's equations implies a
nonvanishing spacetime curvature even in 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.Comment: RevTeX, 4 pages. Selected for Honorable Mention in the Annual Essay
Competition of the Gravity Research Foundation for the year 200
Spin-glass behaviour on random lattices
The ground-state phase diagram of an Ising spin-glass model on a random graph
with an arbitrary fraction of ferromagnetic interactions is analysed in the
presence of an external field. Using the replica method, and performing an
analysis of stability of the replica-symmetric solution, it is shown that
, correponding to an unbiased spin glass, is a singular point in the
phase diagram, separating a region with a spin-glass phase () from a
region with spin-glass, ferromagnetic, mixed, and paramagnetic phases
()
Manejo integrado de pragas do algodoeiro, com enfase aos efeitos colaterais dos pesticidas e o uso de controle biologico.
Conceitos gerais; Efeitos colaterais dos pesticidas no agroecossistema algodoeiro; Seletividade de inseticidas; Resistencia de plantas a insetos e suas interacoes como controle quimico e o controle biologico; Controle biologico na agroecosistema algodoeiro; Efeito das estrategias de controle no manejo integrado de pragas.bitstream/item/33367/1/MANEJO-INTEGRADO-DE-PRAGAS-DO-ALGODOEIRO.pd
Quantization of multidimensional cat maps
In this work we study cat maps with many degrees of freedom. Classical cat
maps are classified using the Cayley parametrization of symplectic matrices and
the closely associated center and chord generating functions. Particular
attention is dedicated to loxodromic behavior, which is a new feature of
two-dimensional maps. The maps are then quantized using a recently developed
Weyl representation on the torus and the general condition on the Floquet
angles is derived for a particular map to be quantizable. The semiclassical
approximation is exact, regardless of the dimensionality or of the nature of
the fixed points.Comment: 33 pages, latex, 6 figures, Submitted to Nonlinearit
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