10 research outputs found
Operator Ordering in Quantum Radiative Processes
In this work we reexamine quantum electrodynamics of atomic eletrons in the
Coulomb gauge in the dipole approximation and calculate the shift of atomic
energy levels in the context of Dalibard, Dupont-Roc and Cohen-Tannoudji (DDC)
formalism by considering the variation rates of physical observables. We then
analyze the physical interpretation of the ordering of operators in the dipole
approximation interaction Hamiltonian in terms of field fluctuations and
self-reaction of atomic eletrons, discussing the arbitrariness in the
statistical functions in second order bound-state perturbation theory.Comment: Latex file, 12 pages, no figures, includes PACS numbers and minor
changes in the text with the addition of a new sectio
Hamilton-Jacobi approach to Berezinian singular systems
In this work we present a formal generalization of the Hamilton-Jacobi
formalism, recently developed for singular systems, to include the case of
Lagrangians containing variables which are elements of Berezin algebra. We
derive the Hamilton-Jacobi equation for such systems, analizing the singular
case in order to obtain the equations of motion as total differential equations
and study the integrability conditions for such equations. An example is solved
using both Hamilton-Jacobi and Dirac's Hamiltonian formalisms and the results
are compared.Comment: LaTex, 30 pages, no figure
Incised valley paleoenvironments interpreted by seismic stratigraphic approach in Patos Lagoon, Southern Brazil
<div><p>ABSTRACT: The Rio Grande do Sul (RS) coastal plain area (33,000 km 2 ) had its physiography modified several times through the Quaternary, responding to allogenic and autogenic forcings. The Patos Lagoon covers a significant area of RS coastal plain (10,000 km 2 ), where incised valleys were identified in previous works. About 1,000 km of high resolution (3.5 kHz) seismic profiles, radiocarbon datings, Standard Penetration Test (SPT) and gravity cores were analyzed to interpret the paleoenvironmental evolution as preserved in incised valley infills. Seismic facies were recognized by seismic parameters. The sediment cores were used to ground-truth the seismic interpretations and help in the paleoenvironmental identification. Key surfaces were established to detail the stratigraphical framework, and seismic facies were grouped into four seismic units, which one classified in respective system tracts within three depositional sequences. The oldest preserved deposits are predominantly fluvial and estuarine facies, representing the falling stage and lowstand system tracts. The Holocene transgressive records are dominated by muddy material, mainly represented by estuarine facies with local variations. The transgression culminated in Late Holocene deposits of Patos Lagoon, representing the highstand system tract. The depositional pattern of the vertical succession was controlled by eustatic variations, while the autogenic forcing (paleogeography and sediment supply) modulated the local facies variation.</p></div
A model for stars of interacting bosons and fermions
Consiglio Nazionale delle Ricerche (CNR). Biblioteca Centrale / CNR - Consiglio Nazionale delle RichercheSIGLEITItal