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showing 10 items of 1264 documents
Harmonic oscillator model for the atom-surface Casimir-Polder interaction energy
2012
In this paper we consider a quantum harmonic oscillator interacting with the electromagnetic radiation field in the presence of a boundary condition preserving the continuous spectrum of the field, such as an infinite perfectly conducting plate. Using an appropriate Bogoliubov-type transformation we can diagonalize exactly the Hamiltonian of our system in the continuum limit and obtain non-perturbative expressions for its ground-state energy. From the expressions found, the atom-wall Casimir-Polder interaction energy can be obtained, and well-know lowest-order results are recovered as a limiting case. Use and advantage of this method for dealing with other systems where perturbation theory …
A microscopic approach to Casimir and Casimir-Polder forces between metallic bodies
2014
We consider the Casimir-Polder interaction energy between a metallic nanoparticle and a metallic plate, as well as the Casimir interaction energy between two macroscopic metal plates, in terms of the many-body dispersion interactions between their constituents. Expressions for two- and three-body dispersion interactions between the microscopic parts of a real metal are first obtained, both in the retarded and non-retarded limits. These expressions are then used to evaluate, a compare each other, the overall two- and three-body contributions to the macroscopic Casimir-Polder and Casimir force, by summing up the contributions from the microscopic constituents of the bodies (metal nanoparticle…
Dynamical Casimir-Polder potentials in non-adiabatic conditions
2014
In this paper we review different aspects of the dynamical Casimir¿Polder potential between a neutral atom and a perfectly conducting plate under nonequilibrium conditions. In order to calculate the time evolution of the atom¿wall Casimir¿Polder potential, we solve the Heisenberg equations describing the dynamics of the coupled system using an iterative technique. Different nonequilibrium initial states are considered, such as bare and partially dressed states. The partially dressed states considered are obtained by a sudden change of a physical parameter of the atom or of its position relative to the conducting plate. Experimental feasibility of detecting the considered dynamical effects i…
Thermal and non-thermal signatures of the Unruh effect in Casimir-Polder forces
2014
We show that Casimir-Polder forces between two relativistic uniformly accelerated atoms exhibit a transition from the short distance thermal-like behavior predicted by the Unruh effect, to a long distance non-thermal behavior, associated with the breakdown of a local inertial description of the system. This phenomenology extends the Unruh thermal response detected by a single accelerated observer to an accelerated spatially extended system of two particles, and we identify the characteristic length scale for this crossover with the inverse of the proper acceleration of the two atoms. Our results are derived separating at fourth order in perturbation theory the contributions of vacuum fluctu…
Reply to "Comment on 'Dispersion Interaction between Two Hydrogen Atoms in a Static Electric Field' "
2020
In their Comment on our Letter Dispersion Interaction between Two Hydrogen Atoms in a Static Electric Field, P. P. Abrantes et al. address one of the main points discussed in our Letter, that is, the possibility to manipulate interatomic interactions through an external static electric field. In our Letter, we have shown that the interaction between two ground-state atoms can be significantly modified, exploiting an external static electric field, and even turned from attractive to repulsive, depending on the strength of the external field and the geometrical configu- ration. In their Comment, Abrantes et al. point out that it is the electrostatic contribution between the electric dipoles i…
Dynamical Casimir-Polder energy between an excited- and a ground-state atom.
2004
We consider the Casimir-Polder interaction between two atoms, one in the ground state and the other in its excited state. The interaction is time-dependent for this system, because of the dynamical self-dressing and the spontaneous decay of the excited atom. We calculate the dynamical Casimir-Polder potential between the two atoms using an effective Hamiltonian approach. The results obtained and their physical meaning are discussed and compared with previous results based on a time-independent approach which uses a non-normalizable dressed state for the excited atom.
Saskarsmes prasmju sekmēšana rotaļdarbībā vidējā pirmsskolas vecuma bērniem
2017
Darba autore: Liene Učaikina Darba temats: Saskarsmes prasmju sekmēšana rotaļdarbībā vidējā pirmsskolas vecuma bērniem Darba veids: Kvalifikācijas darbs Darba zinātniskā vadītāja:lekt. Mg.paed. Rasma Purmale Darba apjoms: 48lappuses, 2 tabulas, 19 attēli, 46 literatūras avoti, 2 pielikumi. Atslēgas vārdi: Vidējā pirmsskolas vecuma bērni, saskarsme, rotaļdarbība Pētījuma mērķis: Pētīt un analizēt vidējā pirmsskolas vecuma bērnu saskarsmes attīstības iespējas rotaļdarbībā. Pētījuma hipotēze: Bērniem būs labi attīstīta saskarsmes prasme, ja pedagogs pedagoģiskajā procesā rotaļdarbībās veidos pozitīvi vidi, organizēs rotaļdarbības atbilstoši bērnu vajadzībām un interesēm. Teorētiskais pamatojum…
Coastal Governance Solutions Development in Latvia
2015
This chapter has focused on the application of the environmental collaboration communication model for separate coastal municipalities in Latvia, in order to assess and to advise on the development of coastal-climate-risk-communication specifications. The model has four components— information, education, participation, and environmentally friendly behavior —and its use in three coastal municipalities was examined in relation to coastal governance processes and stakeholder participation. This four-part model is recommended for use by municipal administrations in other types of complex communication applications, and should be introduced into all governance levels of the planning process and…
The Strategic Cognition View of Issue Salience and the Evolution of a Political Issue: Landis & Gyr, the Hungarian Uprising and East-West Trade, …
2017
Why do firms facing similar stakeholder issues respond quite differently? The recently introduced strategic cognition view of issue salience and firm responsiveness (hereinafter: issue salience model) seeks to tackle this core question of stakeholder theory. I extend the nascent theorizing with a historical case study in order to rethink the model’s firm-centric perspective. The firm under examination in this historical case study is the Swiss multinational Landis & Gyr (LG) during the Cold War period. Like many other Swiss export-oriented companies in the 1950s and early 1960s, LG was challenged by Swiss pressure groups, which were highly effective at putting an issue on the public agenda:…
Innovating European Long-Term Care Policies through the Socio-Economic Support of Families: A Lesson from Practices
2022
LTC and socio-economic deprivation of families are two relevant issues in international debate. The economic or time investment made by families in caregiving has an impact on the socio-economic status of family members in terms of economic means and social inclusion. This study analyzes the practices that are supported by home LTC, examining their characteristics, identifying their strengths, weaknesses, drivers, and barriers, as well as identifying social innovation aspects. The study provides a qualitative interpretative comparison of 22 practices from eight countries, representing the four LTC care models existing in Europe. Cross-studies aid in the development of sustainable policies. …