Search results for "casi"

A microscopic approach to Casimir forces between metal bodies

2014

We consider the Casimir interaction between macroscopic metallic objects in terms of the dispersion interactions (Casimir-Polder and van der Waals) between their constituents. Expressions for two- and three-body dispersion interactions between the microscopic parts of a metal are obtained, both in the retarded and non-retarded limits. They are then used to evaluate two- and three-body contributions of the Casimir force between two flat ideal metallic slabs. Our results show the non-applicability of the Hamaker approximation in this geometry. It is further seen that the three-body contributions give an overall repulsive contribution to the force, which is of the same order of magnitude as th…

Il vuoto: da Galileo al XXI secolo

2009

Electromagnetic field fluctuations near a point-like and an extended field source

2014

We investigate the field fluctuations near a point-like and an extended field source, such as an atom or a polarisable body, and discuss the problem of their singular behaviour at the position of the source. We consider a point-like source interacting with the electromagnetic field, in its dressed ground-state and investigate the local and global properties of the electric and magnetic energy densities in the space around the point-like source, after that the zero-point energy has been subtracted. We show that the assumption of a point-like source leads to a divergence of the renormalized electric and magnetic energy densities at the position of the source. We investigate in detail the math…

Casimir Energies in a One-Dimensional Cavity with a Fluctuating Boundary

2013

We consider a massless scalar field in a one-dimensional cavity with one fixed and one mobile wall. We assume that the mobile wall is also subjected to a harmonic potential, and its mechanical degrees of freedom are treated quantum-mechanically. The wall's position has thus quantum fluctuations around the equilibrium position. The possible motion of the wall makes the cavity length variable, and this gives rise to a wall-field interaction and an effective interaction between the modes of the cavity. We use an effective Hamiltonian, originally introduced by C. K. Law, to describe our system in terms of field modes relative to the equilibrium position of the mobile wall. We obtain by perturba…

Dynamical Casimir-Polder forces between an atom and a conducting wall

2008

Electromagnetic field fluctuations near a dielectric half-space and appearance of surface divergences in the ideal conductor limit

2012

The electromagnetic field fluctuations in the vacuum state are considered in the region external to a half-space filled with a homogeneous non-dissipative dielectric. We discuss the appropriate limits to a real and an ideal metal, focusing on the renormalized field fluctuations (equivalent to energy densities) in the proximity of the dielectric-vacuum interface. We show that, whereas in presence of a real conductor the renormalized field fluctuations are finite in any point of space, surface divergences appear at the interface in the ideal conductor limit. The main features of such divergences are discussed in detail. We point out that the behavior of field fluctuations close to the interfa…

La Casina cinese alla Favorita di Palermo: un'ipotesi di lettura.

2016

L'articolo verte su un'ipotesi interpretativa della componente decorativa della Casina cinese alla Favorita di Palermo basata sulla componente "alla cinese" e su una sua densa natura confuciana. The paper offers a hypothesis of interpretation of the decorative patterns of the Casina cinese at the Favorita Park in Palermo which is based on the component "in Chinese style" that is characterized by a strong Confucian element.

Common fixed point theorems of integral type for OWC mappings under relaxed condition

2017

In this paper, we prove a common fixed point theorem for a pair of occasionally weakly compatible (owc) self mappings satisfying a mixed contractive condition of integral type without using the triangle inequality. We prove also analogous results for two pairs of owc self mappings by assuming symmetry only on the set of points of coincidence. These results unify, extend and complement many results existing in the recent literature. Finally, we give an application of our results in dynamic programming.

Some common fixed point theorems for owc mappings with applications

2013

Starting from the setting of fuzzy metric spaces, we give some new common fixed point theorems for a pair of occasionally weakly compatible (owc) self-mappings satisfying a mixed contractive condition. In proving our results, we do not need to use the triangular inequality. Also we obtain analogous results for two pairs of owc self-mappings by assuming symmetry only on the set of points of coincidence. These results unify, extend and complement some results existing in the literature. Finally, we give some applications of our results.

Lamb shift of a uniformly accelerated hydrogen atom in the presence of a conducting plate

2009

We investigate the effects of acceleration on the energy-level shifts of a hydrogen atom interacting with the electromagnetic field and in the presence of an infinite perfectly conducting plate. We consider the contributions of vacuum fluctuations and of the radiation reaction field to the Lamb shift, and we discuss their dependence from the acceleration of the atom. We show that, because of the presence of the boundary, both vacuum field fluctuations and radiation reaction field contributions are affected by atomic acceleration. In particular, the effect of the vacuum field fluctuations on the energy-level shifts is not equivalent to that of a thermal field. We also discuss the dependence …