Strong Coupling Theory of Two Level Atoms in Periodic Fields

We present a new convergent strong coupling expansion for two-level atoms in external periodic fields, free of secular terms. As a first application, we show that the coherent destruction of tunnelling is a third-order effect. We also present an exact treatment of the high-frequency region, and compare it with the theory of averaging. The qualitative frequency spectrum of the transition probability amplitude contains an effective Rabi frequency.Comment: 4 pages with 3 figure

Urbanização e gestão do litoral centro-sul do estado de Santa Catarina

Thirty six municipalities form the littoral of Santa Catarina State. These municipalities are divided in five sectors: north, center-north, center, center–south and south. Six municipalities belong to the center-south littoral and in this sector is located the bigger coastal lagoon chain of the State. Laguna is the faster growing municipality in this region and has the highest number of inhabitants. The rapid and non-organized urbanization of this area has been causing remarkable environmental impacts such as water pollution, sand dune erosion, loss of coastal vegetation and biodiversity. Activities such as prawn farms, agriculture, tourism and urbanization are the most impacting activities. For a sustainable development of the region some actions should be taken, such as: sewage treatment, urban planning,aquiculture zoning, coastal ecosystems preservation, development and implementation of management plan for conservation areas, environmental laws enforcement

Virtual Compton scattering off the nucleon at low energies

We investigate the low-energy behavior of the four-point Green's function $\Gamma^{\mu\nu}$ describing virtual Compton scattering off the nucleon. Using Lorentz invariance, gauge invariance, and crossing symmetry, we derive the leading terms of an expansion of the operator in the four-momenta $q$ and $q'$ of the initial and final photon, respectively. The model-independent result is expressed in terms of the electromagnetic form factors of the free nucleon, i.e., on-shell information which one obtains from electron-nucleon scattering experiments. Model-dependent terms appear in the operator at $O(q_\alpha q'_\beta)$, whereas the orders $O(q_\alpha q_\beta)$ and $O(q'_\alpha q'_\beta)$ are contained in the low-energy theorem for $\Gamma^{\mu\nu}$, i.e., no new parameters appear. We discuss the leading terms of the matrix element and comment on the use of on-shell equivalent electromagnetic vertices in the calculation of ``Born terms'' for virtual Compton scattering.Comment: 26 pages, RevTex, to appear in Phys. Rev.

Universality of the rho-meson coupling in effective field theory

It is shown that both the universal coupling of the rho-meson and the Kawarabayashi-Suzuki-Riadzuddin-Fayyazuddin expression for the magnitude of its coupling constant follow from the requirement that chiral perturbation theory of pions, nucleons, and rho-mesons is a consistent effective field theory. The prerequisite of the derivation is that all ultraviolet divergences can be absorbed in the redefinition of fields and the available parameters of the most general effective Lagrangian.Comment: 4 pages, 2 figures, REVTeX 4, accepted for publication in PR

A Robust Semidefinite Programming Approach to the Separability Problem

We express the optimization of entanglement witnesses for arbitrary bipartite states in terms of a class of convex optimization problems known as Robust Semidefinite Programs (RSDP). We propose, using well known properties of RSDP, several new sufficient tests for the separability of mixed states. Our results are then generalized to multipartite density operators.Comment: Revised version (minor spell corrections) . 6 pages; submitted to Physical Review