Search results for "Classical"
showing 10 items of 2294 documents
Field fluctuations near a conducting plate and Casimir-Polder forces in the presence of boundary conditions
2006
We consider vacuum fluctuations of the quantum electromagnetic field in the presence of an infinite and perfectly conducting plate. We evaluate how the change of vacuum fluctuations due to the plate modifies the Casimir-Polder potential between two atoms placed near the plate. We use two different methods to evaluate the Casimir-Polder potential in the presence of the plate. They also give new insights on the role of boundary conditions in the Casimir-Polder interatomic potential, as well as indications for possible generalizations to more complicated boundary conditions.
Dynamical Casimir-Polder force between an atom and a conducting wall
2008
The time-dependent Casimir-Polder force arising during the time evolution of an initially bare two-level atom, interacting with the radiation field and placed near a perfectly conducting wall, is considered. Initially the electromagnetic field is supposed to be in the vacuum state and the atom in its ground state. The analytical expression of the force as a function of time and atom-wall distance, is evaluated from the the time-dependent atom-field interaction energy. Physical features and limits of validity of the results are discussed in detail.
Nonlocal properties of dynamical three-body Casimir-Polder forces
2005
We consider the three-body Casimir-Polder interaction between three atoms during their dynamical self-dressing. We show that the time-dependent three-body Casimir-Polder interaction energy displays nonlocal features related to quantum properties of the electromagnetic field and to the nonlocality of spatial field correlations. We discuss the measurability of this intriguing phenomenon and its relation with the usual concept of stationary three-body forces.
Berry's phase in Cavity QED: proposal for observing an effect of field quantization
2002
Geometric phases are well known in classical electromagnetism and quantum mechanics since the early works of Pantcharatnam and Berry. Their origin relies on the geometric nature of state spaces and has been studied in many different systems such as spins, polarized light and atomic physics. Recent works have explored their application in interferometry and quantum computation. Earlier works suggest how to observe these phases in single quantum systems adiabatically driven by external classical devices or sources, where, by classical, we mean any system whose state does not change considerably during the interaction time: an intense magnetic field interacting with a spin 1/2, or a birefringe…
Hybrid QM/MM Molecular Dynamics with AMOEBA Polarizable Embedding
2017
International audience; We present the implementation of a Born-Oppenheimer (BO) hybrid Quantum Mechan-ics/Molecular Mechanics (QM/MM) Molecular Dynamics (MD) strategy using Density Functional Theory (DFT) and the polarizable AMOEBA force field. This approach couples the Gaussian and Tinker suite of programs through a variational formalism allowing for a full self-consistent relaxation of both the AMOEBA induced dipoles and the DFT electronic density at each MD step. As the DFT SCF cycles are the limiting factor in terms of computational efforts and MD stability, we focus on the latter aspect and compare the Time-Reversible BO (TR– BO) and the Extended BO Lagrangian approaches (XL–BO) to th…
Size-consistent single-reference methods for electronic correlation: a unified formulation through intermediate hamiltonian theory
1996
Using the intermediate hamiltonian theory as a unique conceptual frame and the technique of CI matrix dressing, a wide series of single-reference methods for the treatment of the ground state correlation are reviewed, compared, and sometimes improved. These methods range from independent excitation approximation (the very next step beyond MP2) to coupled cluster, going through the so-called electron pair approximations and the (SC)2CI formalism. A hierarchy of these methods can be established according to two criteria: These formulations in terms of diagonalizations of dressed CI matrices avoid convergence problems, but their main advantage is their flexibility, since they apply to multi-re…
Monstrous Hybrids in Shakespeare’s King Lear
2017
ABSTRACT: This article seeks to present the different languages (emblems, Renaissance translations of classical myths, biblical exegesis) that inform the images of monsters which, as hybrid creatures blending human and animal characteristics, serve a dramatic function in Shakespeare’s King Lear . It means to question the ways in which the play links filial ingratitude with female monstrosity and Lear’s madness. Tracing the classical and medieval lineage of the monstrous bestiary (serpent, tiger, vulture) in King Lear and connecting it to emblematic readings of Shakespeare’s time, it explores how Shakespeare provides a dynamic characterisation of Goneril and Regan through their bestialisatio…
Smith, Marshall and Young on division of labour and economic growth
2003
The aim of this paper is to reconstruct the theory of division of labour and economic growth proposed by Adam Smith and developed by Alfred Marshall and Allyn Young. In their approach division of labour is the main engine of growth and plays a central role in capital accumulation and technological progress. We suggest that, according to their theory: 1) economic growth is endogenous; 2) it has the nature of a cumulative, pathdependent process; and 3) it can be described as a disequilibrium process, supported by competitive forces. We argue that these aspects make the contributions of Smith, Marshall and Young still insightful for the development of growth theory, even in the light of the mo…
Money and the natural rate of interest: structural estimates for the United States and the Euro area
2008
We examine the role of money, allowing for three competing environments: the New Keynesian model with separable utility and static money demand; a non-separable utility variant with habit formation; and a version with adjustment costs for holding real balances. The last two variants imply forward-looking behavior of real money balances, as it is optimal for agents to allow their forecast of future interest rates to affect current portfolio decisions. We distinguish between these specifications by conducting a structural econometric analysis for the U.S. and the euro area. FIML estimates confirm the forward-looking character of money demand. Using these estimates we find that, in response to…
Conceptual Understanding of Newtonian Mechanics Through Cluster Analysis of FCI Student Answers
2018
The Force Concept Inventory is a multiple-choice test and is one of the most popular and most analyzed concept inventories. It is used to investigate student understanding of Newtonian mechanics. A structured approach to data analysis can transform it in a “diagnostic” instrument that can validate inferences about student thinking. In this paper, we show how cluster analysis methods can be used to investigate patterns of student conceptual understanding and supply useful details about the relationships among student concepts and misconceptions. The answers given to the FCI questionnaire by a sample of freshman engineering have been analyzed. The analysis takes into account the decomposition…