Weak helix submanifolds of euclidean spaces

It is shown that there exist nonstrong weak 2-helix surfaces of R

Non-Markovian dissipative dynamics of two coupled qubits in independent reservoirs: a comparison between exact solutions and master equation approaches

The reduced dynamics of two interacting qubits coupled to two independent bosonic baths is investigated. The one-excitation dynamics is derived and compared with that based on the resolution of appropriate non-Markovian master equations. The Nakajima-Zwanzig and the time-convolutionless projection operator techniques are exploited to provide a description of the non-Markovian features of the dynamics of the two-qubits system. The validity of such approximate methods and their range of validity in correspondence to different choices of the parameters describing the system are brought to light.Comment: 6 pages, 3 figures. Submitted to PR

The informal city as a different way of urban regeneration

The city is an "organism in the making", an entity in constant transformation, not a complex of immutable elements. The city represents the entire human experiential field of the world, considered as expression of a "fundamental movement of existence" in its completeness and historicity, expressed by the formative structure of tissues and building types, by the urban hierarchies, by the relations with the territory, by the social relations, and by the values and criticalities. The conference’s aim is to propose a dialectical comparison between scholars of Architecture, Urban Planning, Urban History, Restoration, Geography, on the theme of urban morphology with an interpretative perspective based on the concept of "operating history". Search for a multidisciplinary syncretism that eludes single analyzing techniques and aims to the complete reconstruction of the urban phenomenology in its totality and concrete essence, through the study of the changing and inflexible condition of ‘fluidity’ hinged on the world’s events. An integrated thought based on the critical concept of ‘making’ that constitutes, phase by phase, the signifying element of each present, explained through the relationship between the before and the after: that is the research perspective of ‘being’ that announces the notion of transformational process. Therefore, the projection in the future of the urban form is the central theme of the conference that proposes to stimulate the reflection on the issues as: recovery (not only of the historical city), re-use of existing urban spaces, regeneration, ex novo design in peripheral and peri-urban areas and natural spaces. All that, without neglecting the issue of sustainability, not considered with the strabismus of those who surrender to the "technique" pre-domain

Dissipation and entanglement dynamics for two interacting qubits coupled to independent reservoirs

We derive the master equation of a system of two coupled qubits by taking into account their interaction with two independent bosonic baths. Important features of the dynamics are brought to light, such as the structure of the stationary state at general temperatures and the behaviour of the entanglement at zero temperature, showing the phenomena of sudden death and sudden birth as well as the presence of stationary entanglement for long times. The model here presented is quite versatile and can be of interest in the study of both Josephson junction architectures and cavity-QED.Comment: 14 pages, 3 figures, submitted to Journal of Physics A: Mathematical and Theoretica

Stimulated Raman adiabatic passage in an open quantum system: Master equation approach

A master equation approach to the study of environmental effects in the adiabatic population transfer in three-state systems is presented. A systematic comparison with the non-Hermitian Hamiltonian approach [N. V. Vitanov and S. Stenholm, Phys. Rev. A {\bf 56}, 1463 (1997)] shows that in the weak coupling limit the two treatments lead to essentially the same results. Instead, in the strong damping limit the predictions are quite different: in particular the counterintuitive sequences in the STIRAP scheme turn out to be much more efficient than expected before. This point is explained in terms of quantum Zeno dynamics.Comment: 11 pages, 4 figure