Casimir Energy and Entropy between perfect metal Spheres

We calculate the Casimir energy and entropy for two perfect metal spheres in the large and short separation limit. We obtain nonmonotonic behavior of the Helmholtz free energy with separation and temperature, leading to parameter ranges with negative entropy, and also nonmonotonic behavior of the entropy with temperature and with the separation between the spheres. The appearance of this anomalous behavior of the entropy is discussed as well as its thermodynamic consequences.Comment: 10 pages and 8 figures. Accepted for publication in the Proceedings of the tenth conference on Quantum Field Theory under the influence of external conditions - QFEXT'1

Casimir Forces between Compact Objects: I. The Scalar Case

We have developed an exact, general method to compute Casimir interactions between a finite number of compact objects of arbitrary shape and separation. Here, we present details of the method for a scalar field to illustrate our approach in its most simple form; the generalization to electromagnetic fields is outlined in Ref. [1]. The interaction between the objects is attributed to quantum fluctuations of source distributions on their surfaces, which we decompose in terms of multipoles. A functional integral over the effective action of multipoles gives the resulting interaction. Each object's shape and boundary conditions enter the effective action only through its scattering matrix. Their relative positions enter through universal translation matrices that depend only on field type and spatial dimension. The distinction of our method from the pairwise summation of two-body potentials is elucidated in terms of the scattering processes between three objects. To illustrate the power of the technique, we consider Robin boundary conditions $\phi -\lambda \partial_n \phi=0$, which interpolate between Dirichlet and Neumann cases as $\lambda$ is varied. We obtain the interaction between two such spheres analytically in a large separation expansion, and numerically for all separations. The cases of unequal radii and unequal $\lambda$ are studied. We find sign changes in the force as a function of separation in certain ranges of $\lambda$ and see deviations from the proximity force approximation even at short separations, most notably for Neumann boundary conditions.Comment: 27 pages, 9 figure

The effects of burnout and supervisory social support on the relationship between work-family conflict and intention to leave: a study of Australian cancer workers.

Purpose- To examine the effects of burnout and supervisory social support on the relationship between work-family conflict, and intention to leave of cancer workers in an Australian health care setting. Design/methodology/approach- Data collected from a public hospital of 114 cancer workers were used to test a model of the consequences of work-family conflict. The strength of the indirect effects of work-family conflict on intention to leave via burnout will depend on supervisor support was tested by conducting a moderated mediation analysis. Findings- Path analytic tests of moderated mediation supported the hypothesis that burnout mediates the relationship between work-family conflict (i.e., work-in-family conflict and family-in-work) and intention to leave the organisation and that the mediation framework is stronger in the presence of higher social supervisory support. Implications are drawn for theory, research and practice. Originality/value- This study applies the innovative statistical technique of moderated mediation analysis to demonstrate that burnout mediates the relationship between workfamily conflict and intention to leave the organisation and that the mediation framework is stronger in the presence of lower social supervisory support. In the context of the continued shortage of many clinician groups theses results shed further light on the appropriate course of action for hospital management

Fermion Particle Production in Dynamical Casimir Effect in a Three Dimensional Box

In this paper we investigate the problem of fermion creation inside a three dimensional box. We present an appropriate wave function which satisfies the Dirac equation in this geometry with MIT bag model boundary condition. We consider walls of the box to have dynamic and introduce the time evolution of the quantized field by expanding it over the 'instantaneous basis'. We explain how we can obtain the average number of particles created. In this regard we find the Bogliubove coefficients. We consider an oscillation and determine the coupling conditions between different modes that can be satisfied depending on the cavity's spectrum. Assuming the parametric resonance case we obtain an expression for the mean number of created fermions in each mode of an oscillation and their dynamical Casimir energy.Comment: 5 pages, no figur

Fluctuations of the Casimir-Polder force between an atom and a conducting wall

We consider the quantum fluctuations of the Casimir-Polder force between a neutral atom and a perfectly conducting wall in the ground state of the system. In order to obtain the atom-wall force fluctuation we first define an operator directly associated to the force experienced by the atom considered as a polarizable body in an electromagnetic field, and we use a time-averaged force operator in order to avoid ultraviolet divergences appearing in the fluctuation of the force. This time-averaged force operator takes into account that any measurement involves a finite time. We also calculate the Casimir-Polder force fluctuation for an atom between two conducting walls. Experimental observability of these Casimir-Polder force fluctuations is also discussed, as well as the dependence of the relative force fluctuation on the duration of the measurement.Comment: 6 page

Casimir effect for curved geometries: PFA validity limits

We compute Casimir interaction energies for the sphere-plate and cylinder-plate configuration induced by scalar-field fluctuations with Dirichlet boundary conditions. Based on a high-precision calculation using worldline numerics, we quantitatively determine the validity bounds of the proximity force approximation (PFA) on which the comparison between all corresponding experiments and theory are based. We observe the quantitative failure of the PFA on the 1% level for a curvature parameter a/R > 0.00755. Even qualitatively, the PFA fails to predict reliably the correct sign of genuine Casimir curvature effects. We conclude that data analysis of future experiments aiming at a precision of 0.1% must no longer be based on the PFA.Comment: 4 pages, 4 figure

Casimir Effect in Background of Static Domain Wall

In this paper we investigate the vacuum expectation values of energy- momentum tensor for conformally coupled scalar field in the standard parallel plate geometry with Dirichlet boundary conditions and on background of planar domain wall case. First we calculate the vacuum expectation values of energy-momentum tensor by using the mode sums, then we show that corresponding properties can be obtained by using the conformal properties of the problem. The vacuum expectation values of energy-momentum tensor contains two terms which come from the boundary conditions and the the gravitational background. In the Minkovskian limit our results agree with those obtained in [3].Comment: 8 Page

Alternative derivation of the Feigel effect and call for its experimental verification

A recent theory by Feigel [Phys. Rev. Lett. {\bf 92}, 020404 (2004)] predicts the finite transfer of momentum from the quantum vacuum to a fluid placed in strong perpendicular electric and magnetic fields. The momentum transfer arises because of the optically anisotropic magnetoelectric response induced in the fluid by the fields. After summarising Feigel's original assumptions and derivation (corrected of trivial mistakes), we rederive the same result by a simpler route, validating Feigel's semi-classical approach. We then derive the stress exerted by the vacuum on the fluid which, if the Feigel hypothesis is correct, should induce a Poiseuille flow in a tube with maximum speed $\approx 100\mu$m/s (2000 times larger than Feigel's original prediction). An experiment is suggested to test this prediction for an organometallic fluid in a tube passing through the bore of a high strength magnet. The predicted flow can be measured directly by tracking microscopy or indirectly by measuring the flow rate ($\approx 1$ml/min) corresponding to the Poiseuille flow. A second experiment is also proposed whereby a `vacuum radiometer' is used to test a recent prediction that the net force on a magnetoelectric slab in the vacuum should be zero.Comment: 20 pages, 1 figures. revised and improved versio

Edges and Diffractive Effects in Casimir Energies

The prototypical Casimir effect arises when a scalar field is confined between parallel Dirichlet boundaries. We study corrections to this when the boundaries themselves have apertures and edges. We consider several geometries: a single plate with a slit in it, perpendicular plates separated by a gap, and two parallel plates, one of which has a long slit of large width, related to the case of one plate being semi-infinite. We develop a general formalism for studying such problems, based on the wavefunctional for the field in the gap between the plates. This formalism leads to a lower dimensional theory defined on the open regions of the plates or boundaries. The Casimir energy is then given in terms of the determinant of the nonlocal differential operator which defines the lower dimensional theory. We develop perturbative methods for computing these determinants. Our results are in good agreement with known results based on Monte Carlo simulations. The method is well suited to isolating the diffractive contributions to the Casimir energy.Comment: 32 pages, LaTeX, 9 figures. v2: additional discussion of renormalization procedure, version to appear in PRD. v3: corrected a sign error in (70

Violation of action--reaction and self-forces induced by nonequilibrium fluctuations

We show that the extension of Casimir-like forces to fluctuating fluids driven out of equilibrium can exhibit two interrelated phenomena forbidden at equilibrium: self-forces can be induced on single asymmetric objects and the action--reaction principle between two objects can be violated. These effects originate in asymmetric restrictions imposed by the objects' boundaries on the fluid's fluctuations. They are not ruled out by the second law of thermodynamics since the fluid is in a nonequilibrium state. Considering a simple reaction--diffusion model for the fluid, we explicitly calculate the self-force induced on a deformed circle. We also show that the action--reaction principle does not apply for the internal Casimir forces exerting between a circle and a plate. Their sum, instead of vanishing, provides the self-force on the circle-plate assembly.Comment: 4 pages, 1 figure. V2: New title; Abstract partially rewritten; Largely enhanced introductory and concluding remarks (incl. new Refs.