Microscopic dynamical Casimir effect
Souza, Reinaldo de Melo e.; Impens, François; Neto, Paulo A. Maia
2018-03-01
We consider an atom in its ground state undergoing a nonrelativistic oscillation in free space. The interaction with the electromagnetic quantum vacuum leads to two effects to leading order in perturbation theory. When the mechanical frequency is larger than the atomic transition frequency, the dominant effect is the motion-induced transition to an excited state with the emission of a photon carrying the excess energy. We compute the angular distribution of emitted photons and the excitation rate. On the other hand, when the mechanical frequency is smaller than the transition frequency, the leading-order effect is the parametric emission of photon pairs, which constitutes the microscopic counterpart of the dynamical Casimir effect. We discuss the properties of the microscopic dynamical Casimir effect and build a connection with the photon production by an oscillating macroscopic metallic mirror.
Casimir effect for interacting fields
International Nuclear Information System (INIS)
Kay, B.S.
1982-01-01
The author discusses some recent work on the Casimir effect: that is the problem of renormalizing Tsub(μγ) on locally-flat space-times. That is on space-times which, while topologically non-trivial are locally Minkowskian - with vanishing local curvature. The author has developed a systematic method for calculating this Casimir effect for interacting fields to arbitrary order in perturbation theory - and for arbitrary components of Tsub(μγ) which he describes in general and then illustrates it by describing first order perturbation theory calculations for a lambdaphi 4 theory for the two models: the cylinder space-time and the parallel plates. (Auth.)
Casimir Effect on the Worldline
Gies, Holger; Moyaerts, L; Gies, Holger; Langfeld, Kurt; Moyaerts, Laurent
2003-01-01
We develop a method to compute the Casimir effect for arbitrary geometries. The method is based on the string-inspired worldline approach to quantum field theory and its numerical realization with Monte-Carlo techniques. Concentrating on Casimir forces between rigid bodies induced by a fluctuating scalar field, we test our method with the parallel-plate configuration. For the experimentally relevant sphere-plate configuration, we study curvature effects quantitatively and perform a comparison with the ``proximity force approximation'', which is the standard approximation technique. Sizable curvature effects are found for a distance-to-curvature-radius ratio of a/R >~ 0.02. Our method is embedded in renormalizable quantum field theory with a controlled treatment of the UV divergencies. As a technical by-product, we develop various efficient algorithms for generating closed-loop ensembles with Gaussian distribution.
The Casimir effect: medium and geometry
International Nuclear Information System (INIS)
Marachevsky, Valery N
2012-01-01
Theory of the Casimir effect is presented in several examples. Casimir–Polder-type formulas, Lifshitz theory and theory of the Casimir effect for two gratings separated by a vacuum slit are derived. Equations for the electromagnetic field in the presence of a medium and dispersion are discussed. The Casimir effect for systems with a layer of 2 + 1 fermions is studied. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical in honour of Stuart Dowker's 75th birthday devoted to ‘Applications of zeta functions and other spectral functions in mathematics and physics’. (paper)
Casimir effect in spherical shells
International Nuclear Information System (INIS)
Ruggiero, J.R.
1985-01-01
The analytic regularization method is applied to study the Casimir effect for spherical cavities. Although many works have been presented in the past few years, problems related to the elimination of the regulator parameter still remain. A way to calculate the zero point energy of a perfectly conducting spherical shell which is a miscellaneous of those presented early is here proposed, How a cancelation of divergent terms occurs and how a finite parte is obtained after the elimination of the regulator parameter is shown. As a by-product the zero point energy of the interior vibration modes is obtained and this has some relevance to the quarks bag model. This relev ance is also discussed. The calculation of the energy fom the density view is also discussed. Some works in this field are criticized. The logarithmic divergent terms in the zero point energy are studied when the interior and exterior of the sphere are considered as a medium not dispersive and characterized by a dielectric constants ε 1 and ε 2 and peermeability constants μ 1 and μ 2 respectivelly. The logarithmic divergent terms are not present in the case of ε i μ i =K, with K some constant and i=1,2. (author) [pt
Johnson noise and the thermal Casimir effect
International Nuclear Information System (INIS)
Bimonte, Giuseppe
2007-01-01
We study the thermal interaction between two nearby thin metallic wires, at finite temperature. It is shown that the Johnson currents in the wires give rise, via inductive coupling, to a repulsive force between them. This thermal interaction exhibits all the puzzling features found recently in the thermal Casimir effect for lossy metallic plates, suggesting that the physical origin of the difficulties encountered in the Casimir problem resides in the inductive coupling between the Johnson currents inside the plates. We show that in our simple model all puzzles are resolved if account is taken of capacitive effects associated with the end points of the wires. Our findings suggest that capacitive finite-size effects may play an important role in the resolution of the analogous problems met in the thermal Casimir effect
Dynamical Casimir effect with semi-transparent mirrors, and cosmology
International Nuclear Information System (INIS)
Elizalde, Emilio
2008-01-01
After reviewing some essential features of the Casimir effect and, specifically, of its regularization by zeta function and Hadamard methods, we consider the dynamical Casimir effect (or Fulling-Davies theory), where related regularization problems appear, with a view to an experimental verification of this theory. We finish with a discussion of the possible contribution of vacuum fluctuations to dark energy, in a Casimir-like fashion, that might involve the dynamical version
Xu, Jun; Klimchitskaya, G. L.; Mostepanenko, V. M.; Mohideen, U.
2018-03-01
It is well known that residual electrostatic forces create significant difficulties in precise measurements of the Casimir force and the wide use of Casimir-operated microdevices. We experimentally demonstrate that, with the help of Ar-ion cleaning of the surfaces, it is possible to make electrostatic effects negligibly small compared to the Casimir interaction. Our experimental setup consists of a dynamic atomic force microscope supplemented with an Ar-ion gun and argon reservoir. The residual potential difference between the Au-coated surfaces of a sphere and those of a plate was measured both before and after in situ Ar-ion cleaning. It is shown that this cleaning decreases the magnitude of the residual potential by up to an order of magnitude and makes it almost independent of the separation. The gradient of the Casimir force was measured using ordinary samples subjected to Ar-ion cleaning. The obtained results are shown to be in good agreement both with previous precision measurements using specially selected samples and with theoretical predictions of the Lifshitz theory. The conclusion is made that the suggested method of in situ Ar-ion cleaning is effective in reducing the electrostatic effects and therefore is a great resource for experiments on measuring the Casimir interaction and for Casimir-operated microdevices.
Gravitational Casimir-Polder effect
Hu, Jiawei; Yu, Hongwei
2017-04-01
The interaction due to quantum gravitational vacuum fluctuations between a gravitationally polarizable object modelled as a two-level system and a gravitational boundary is investigated. This quantum gravitational interaction is found to be position-dependent, which induces a force in close analogy to the Casimir-Polder force in the electromagnetic case. For a Dirichlet boundary, the quantum gravitational potential for the polarizable object in its ground-state is shown to behave like z-5 in the near zone, and z-6 in the far zone, where z is the distance to the boundary. For a concrete example, where a Bose-Einstein condensate is taken as a gravitationally polarizable object, the relative correction to the radius of the BEC caused by fluctuating quantum gravitational waves in vacuum is found to be of order 10-21. Although the correction is far too small to observe in comparison with its electromagnetic counterpart, it is nevertheless of the order of the gravitational strain caused by a recently detected black hole merger on the arms of the LIGO.
Temperature dependence of the Casimir effect
Energy Technology Data Exchange (ETDEWEB)
Brevik, I [Department of Energy and Process Engineering, Norwegian University of Science and Technology, N-7491 Trondheim (Norway); Aarseth, J B [Department of Structural Engineering, Norwegian University of Science and Technology, N-7491 Trondheim (Norway)
2006-05-26
In view of the increasing accuracy of Casimir experiments, there is a need for performing accurate theoretical calculations. Using accurate experimental data for the permittivities we present, via the Lifshitz formula applied to the standard Casimir setup with two parallel plates, accurate theoretical results in the case of the metals Au, Cu and Al. Both similar and dissimilar cases are considered. Concentrating in particular on the finite temperature effect, we show how the Casimir pressure varies with separation for three different temperatures, T = {l_brace}1, 300, 350{r_brace}K. The metal surfaces are taken to be perfectly plane. The experimental data for the permittivities generally yield results that are in a good agreement with those calculated from the Drude relation with finite relaxation frequency. We give the results in a tabular form, in order to facilitate the assessment of the temperature correction which is on the 1% level. We emphasize two points: (i) the most promising route for a definite experimental verification of the finite temperature correction appears to be to concentrate on the case of large separations (optimum around 2 {mu}m); and (ii) there is no conflict between the present kind of theory and the Nernst theorem in thermodynamics.
Mode Contributions to the Casimir Effect
Intravaia, F.; Henkel, C.
2010-04-01
Applying a sum-over-modes approach to the Casimir interaction between two plates with finite conductivity, we isolate and study the contributions of surface plasmons and Foucault (eddy current) modes. We show in particular that for the TE-polarization eddy currents provide a repulsive force that cancels, at high temperatures, the Casimir free energy calculated with the plasma model.
Nonperturbative Dynamical Casimir Effect in Optomechanical Systems: Vacuum Casimir-Rabi Splittings
Directory of Open Access Journals (Sweden)
Vincenzo Macrì
2018-02-01
Full Text Available We study the dynamical Casimir effect using a fully quantum-mechanical description of both the cavity field and the oscillating mirror. We do not linearize the dynamics, nor do we adopt any parametric or perturbative approximation. By numerically diagonalizing the full optomechanical Hamiltonian, we show that the resonant generation of photons from the vacuum is determined by a ladder of mirror-field vacuum Rabi splittings. We find that vacuum emission can originate from the free evolution of an initial pure mechanical excited state, in analogy with the spontaneous emission from excited atoms. By considering a coherent drive of the mirror, using a master-equation approach to take losses into account, we are able to study the dynamical Casimir effect for optomechanical coupling strengths ranging from weak to ultrastrong. We find that a resonant production of photons out of the vacuum can be observed even for mechanical frequencies lower than the cavity-mode frequency. Since high mechanical frequencies, which are hard to achieve experimentally, were thought to be imperative for realizing the dynamical Casimir effect, this result removes one of the major obstacles for the observation of this long-sought effect. We also find that the dynamical Casimir effect can create entanglement between the oscillating mirror and the radiation produced by its motion in the vacuum field, and that vacuum Casimir-Rabi oscillations can occur. Finally, we also show that all these findings apply not only to optomechanical systems, but also to parametric amplifiers operating in the fully quantum regime.
The Casimir effect for pistons with transmittal boundary conditions
Fucci, Guglielmo
2017-11-01
This work focuses on the analysis of the Casimir effect for pistons subject to transmittal boundary conditions. In particular we consider, as piston configuration, a direct product manifold of the type I × N where I is a closed interval of the real line and N is a smooth compact Riemannian manifold. By utilizing the spectral zeta function regularization technique, we compute the Casimir energy of the system and the Casimir force acting on the piston. Explicit results for the force are provided when the manifold N is a d-dimensional sphere.
Casimir effect in presence of spontaneous Lorentz symmetry breaking
Escobar, C. A.
2018-01-01
The Casimir effect is one of the most remarkable consequences of the nonzero vacuum energy predicted by quantum field theory. In this contribution we study the Lorentz-violation effects of the minimal standard-model extension on the Casimir force between two parallel conducting plates in the vacuum. Using a perturbative method, we compute the relevant Green’s function which satisfies given boundary conditions. The standard point-splitting technique allow us to express the vacuum expectation value of the stress-energy tensor in terms of this Green’s function. Finally, we study the Casimir energy and the Casimir force paying particular attention to the quantum effects as approaching the plates.
An ``Anatomic approach" to study the Casimir effect
Intravaia, Francesco; Haakh, Harald; Henkel, Carsten
2010-03-01
The Casimir effect, in its simplest definition, is a quantum mechanical force between two objects placed in vacuum. In recent years the Casimir force has been the object of an exponentially growing attention both from theorists and experimentalists. A new generation of experiments paved the way for new challenges and spotted some shadows in the comparison to theory. Here we are going to isolate different contributions to the Casimir interaction and perform a detailed study to shine new light on this phenomenon. As an example, the contributions of Foucault (eddy current) modes will be discussed in different configurations. This ``anatomic approach'' allows to clearly put into evidence special features and to explain unusual behaviors. This brings new physical understanding on the undergoing physical mechanisms and suggests new ways to engineer the Casimir effect.
Casimir Effect and Black Hole Radiation
Rahbardehghan, S.
2018-03-01
The gravitational field of a black hole intrinsically creates a potential barrier consisted of two reflecting boundaries; the first one far from the hole and the second one in the vicinity of its horizon. With respect to this fact and assuming the boundaries as good conductors (in view of an observer near the horizon just outside the second boundary), in a series of papers, R.M. Nugayev by considering a conformally coupled massless scalar field and based on the calculations of Candelas and Deutsch (the accelerated-mirror results) has claimed that " ...the existence of the potential barrier is as crucial for Hawking evaporation as the existence of the horizon". In this paper, by taking the same assumptions, through straightforward reasonings, we explicitly show that contrary to this claim, the effects of the first boundary on the black hole radiation are quite negligible. Moreover, the inclusion of the second boundary makes the situation more complicated, because the induced Casimir energy-momentum tensor by this boundary in its vicinity is divergent of order δ ^{-4} ( δ is the distance to the boundary).
Evanescent radiation, quantum mechanics and the Casimir effect
Schatten, Kenneth H.
1989-01-01
An attempt to bridge the gap between classical and quantum mechanics and to explain the Casimir effect is presented. The general nature of chaotic motion is discussed from two points of view: the first uses catastrophe theory and strange attractors to describe the deterministic view of this motion; the underlying framework for chaos in these classical dynamic systems is their extreme sensitivity to initial conditions. The second interpretation refers to randomness associated with probabilistic dynamics, as for Brownian motion. The present approach to understanding evanescent radiation and its relation to the Casimir effect corresponds to the first interpretation, whereas stochastic electrodynamics corresponds to the second viewpoint. The nonlinear behavior of the electromagnetic field is also studied. This well-understood behavior is utilized to examine the motions of two orbiting charges and shows a closeness between the classical behavior and the quantum uncertainty principle. The evanescent radiation is used to help explain the Casimir effect.
Interplay between geometry and temperature in the Casimir effect
Energy Technology Data Exchange (ETDEWEB)
Weber, Alexej
2010-06-23
In this thesis, we investigate the interplay between geometry and temperature in the Casimir effect for the inclined-plates, sphere-plate and cylinder-plate configurations. We use the worldline approach, which combines the string-inspired quantum field theoretical formalism with Monte Carlo techniques. The approach allows the precise computation of Casimir energies in arbitrary geometries. We analyze the dependence of the Casimir energy, force and torque on the separation parameter and temperature T, and find Casimir phenomena which are dominated by long-range fluctuations. We demonstrate that for open geometries, thermal energy densities are typically distributed on scales of thermal wavelengths. As an important consequence, approximation methods for thermal corrections based on local energy-density estimates, such as the proximity-force approximation, are found to become unreliable even at small surface-separations. Whereas the hightemperature behavior is always found to be linear in T, richer power-law behaviors at small temperatures emerge. In particular, thermal forces can develop a non-monotonic behavior. Many novel numerical as well as analytical results are presented. (orig.)
Cosmology in nonlinear multidimensional gravity and the Casimir effect
International Nuclear Information System (INIS)
Bolokhov, S V; Bronnikov, K A
2017-01-01
We study the possible cosmological models in Kaluza-Klein-type multidimensional gravity with a curvature-nonlinear Lagrangian and a spherical extra space, taking into account the Casimir energy. First, we find a minimum of the effective potential of extra dimensions, leading to a physically reasonable value of the effective cosmological constant in our 4D space-time. In this model, the huge Casimir energy density is compensated by a fine-tuned contribution of the curvature-nonlinear terms in the original action. Second, we present a viable model with slowly evolving extra dimensions and power-law inflation in our space-time. In both models, the results formulated in Einstein and Jordan frames are compared. (paper)
Attractive Casimir effect in an infrared modified gluon bag model
International Nuclear Information System (INIS)
Oxman, L.E.; Amaral, R.L.P.G.; Svaiter, N.F.
2005-01-01
In this work, we are motivated by previous attempts to derive the vacuum contribution to the bag energy in terms of familiar Casimir energy calculations for spherical geometries. A simple infrared modified model is introduced which allows studying the effects of the analytic structure as well as the geometry in a clear manner. In this context, we show that if a class of infrared vanishing effective gluon propagators is considered, then the renormalized vacuum energy for a spherical bag is attractive, as required by the bag model to adjust hadron spectroscopy
Hide it to see it better: a robust setup to probe the thermal Casimir effect.
Bimonte, Giuseppe
2014-06-20
We describe a Casimir setup consisting of two aligned sinusoidally corrugated Ni surfaces, one of which is "hidden" by a thin opaque layer of gold with a flat exposed surface. The gold layer acts as a low-pass filter that allows for a clean observation of the controversial thermal Casimir force between the corrugations, with currently available Casimir apparatuses. The proposed scheme of measurement, based on the phase-dependent modulation of the Casimir force, requires no electrostatic calibrations of the apparatus, and is unaffected by uncertainties in the knowledge of the optical properties of the surfaces. This scheme should allow for an unambiguous discrimination between alternative theoretical prescriptions that have been proposed in the literature for the thermal Casimir effect.
Casimir effect in multidimensional quantum supergravities and supersymmetry breaking
International Nuclear Information System (INIS)
Odintsov, S.D.
1988-01-01
The one-loop effective action (the Casimir gravitational energy) of the aribitrary Einstein supergravity on the background M/sub 4/ X T/sub D-4/, where M/sub 4/ is the Minkowski space with non-zero temperature, T/sub d/ is the d-dimensional torus, is calculated. The problem of quantum breaking of supersymmetry is discussed. The Vilkovisky-De Witt effective action in the D-dimensional Einstein gravity with the Λ-term on the background M/sub 4/ X T/sub D-4/ is found. An idea is expressed that a temperature phase transition in Kaluza-Klein theories is possible. For d=5 gravity, the Vilkovisky-De Witt effective a< ction on the R/sub 4/ X S/sub 1/, where R/sub 4/ is fourdimensional curved space-time with non-zero temperature, is found
Casimir effect in the rainbow Einstein's universe
Bezerra, V. B.; Mota, H. F.; Muniz, C. R.
2017-10-01
In the present paper we investigate the effects caused by the modification of the dispersion relation obtained by solving the Klein-Gordon equation in the closed Einstein's universe in the context of rainbow's gravity models. Thus, we analyse how the quantum vacuum fluctuations of the scalar field are modified when compared with the results obtained in the usual General Relativity scenario. The regularization, and consequently the renormalization, of the vacuum energy is performed adopting the Epstein-Hurwitz and Riemann's zeta functions.
Speeding up the antidynamical Casimir effect with nonstationary qutrits
Dodonov, A. V.; Díaz-Guevara, J. J.; Napoli, A.; Militello, B.
2017-09-01
The antidynamical Casimir effect (ADCE) is a term coined to designate the coherent annihilation of excitations due to resonant external perturbation of system parameters, allowing for extraction of quantum work from nonvacuum states of some field. Originally proposed for a two-level atom (qubit) coupled to a single-cavity mode in the context of the nonstationary quantum Rabi model, it suffered from a very low transition rate and correspondingly narrow resonance linewidth. In this paper we show analytically and numerically that the ADCE rate can be increased by at least one order of magnitude by replacing the qubit by an artificial three-level atom (qutrit) in a properly chosen configuration. For the cavity thermal state we demonstrate that the dynamics of the average photon number and atomic excitation is completely different from the qubit's case, while the behavior of the total number of excitations is qualitatively similar yet significantly faster.
Effective field theory of thermal Casimir interactions between anisotropic particles.
Haussman, Robert C; Deserno, Markus
2014-06-01
We employ an effective field theory (EFT) approach to study thermal Casimir interactions between objects bound to a fluctuating fluid surface or interface dominated by surface tension, with a focus on the effects of particle anisotropy. The EFT prescription disentangles the constraints imposed by the particles' boundaries from the calculation of the interaction free energy by constructing an equivalent point particle description. The finite-size information is captured in a derivative expansion that encodes the particles' response to external fields. The coefficients of the expansion terms correspond to generalized tensorial polarizabilities and are found by matching the results of a linear response boundary value problem computed in both the full and effective theories. We demonstrate the versatility of the EFT approach by constructing the general effective Hamiltonian for a collection of particles of arbitrary shapes. Taking advantage of the conformal symmetry of the Hamiltonian, we discuss a straightforward conformal mapping procedure to systematically determine the polarizabilities and derive a complete description for elliptical particles. We compute the pairwise interaction energies to several orders for nonidentical ellipses as well as their leading-order triplet interactions and discuss the resulting preferred pair and multibody configurations. Furthermore, we elaborate on the complications that arise with pinned particle boundary conditions and show that the powerlike corrections expected from dimensional analysis are exponentially suppressed by the leading-order interaction energies.
Casimir effect in rugby-ball type flux compactifications
International Nuclear Information System (INIS)
Elizalde, Emilio; Minamitsuji, Masato; Naylor, Wade
2007-01-01
As a continuation of the work by Minamitsuji, Naylor, and Sasaki [J. High Energy Phys. 12 (2006) 079], we discuss the Casimir effect for a massless bulk scalar field in a 4D toy model of a 6D warped flux compactification model, to stabilize the volume modulus. The one-loop effective potential for the volume modulus has a form similar to the Coleman-Weinberg potential. The stability of the volume modulus against quantum corrections is related to an appropriate heat kernel coefficient. However, to make any physical predictions after volume stabilization, knowledge of the derivative of the zeta function, ζ ' (0) (in a conformally related spacetime) is also required. By adding up the exact mass spectrum using zeta-function regularization, we present a revised analysis of the effective potential. Finally, we discuss some physical implications, especially concerning the degree of the hierarchy between the fundamental energy scales on the branes. For a larger degree of warping our new results are very similar to the ones given by Minamitsuji, Naylor, and Sasaki [J. High Energy Phys. 12 (2006) 079] and imply a larger hierarchy. In the nonwarped (rugby ball) limit the ratio tends to converge to the same value, independently of the bulk dilaton coupling
A Toy Cosmology Using a Hubble-Scale Casimir Effect
Directory of Open Access Journals (Sweden)
Michael E. McCulloch
2014-02-01
Full Text Available The visible mass of the observable universe agrees with that needed for a flat cosmos, and the reason for this is not known. It is shown that this can be explained by modelling the Hubble volume as a black hole that emits Hawking radiation inwards, disallowing wavelengths that do not fit exactly into the Hubble diameter, since partial waves would allow an inference of what lies outside the horizon. This model of “horizon wave censorship” is equivalent to a Hubble-scale Casimir effect. This incomplete toy model is presented to stimulate discussion. It predicts a minimum mass and acceleration for the observable universe which are in agreement with the observed mass and acceleration, and predicts that the observable universe gains mass as it expands and was hotter in the past. It also predicts a suppression of variation on the largest cosmic scales that agrees with the low-l cosmic microwave background anomaly seen by the Planck satellite.
What is the temperature dependence of the Casimir effect?
Energy Technology Data Exchange (ETDEWEB)
Hoeye, J S [Department of Physics, Norwegian University of Science and Technology, N-7491, Trondheim (Norway); Brevik, I [Department of Energy and Process Engineering, Norwegian University of Science and Technology, N-7491, Trondheim (Norway); Aarseth, J B [Department of Energy and Process Engineering, Norwegian University of Science and Technology, N-7491, Trondheim (Norway); Milton, K A [Department of Physics, Washington University, St. Louis, MO 63130 (United States)
2006-05-19
There has been recent criticism of our approach to the Casimir force between real metallic surfaces at finite temperature, saying it is in conflict with the third law of thermodynamics and in contradiction with experiment. We show that these claims are unwarranted, and that our approach has strong theoretical support, while the experimental situation is still unclear.
The Casimir effect in rugby-ball type flux compactifications
Minamitsuji, M.
2008-04-01
We discuss volume stabilization in a 6D braneworld model based on 6D supergravity theory. The internal space is compactified by magnetic flux and contains codimension two 3-branes (conical singularities) as its boundaries. In general the external 4D spacetime is warped and in the unwrapped limit the shape of the internal space looks like a 'rugby ball'. The size of the internal space is not fixed due to the scale invariance of the supergravity theory. We discuss the possibility of volume stabilization by the Casimir effect for a massless, minimally coupled bulk scalar field. The main obstacle in studying this case is that the brane (conical) part of the relevant heat kernel coefficient (a6) has not been formulated. Thus as a first step, we consider the 4D analog model with boundary codimension two 1-branes. The spacetime structure of the 4D model is very similar to that of the original 6D model, where now the relevant heat kernel coefficient is well known. We derive the one-loop effective potential induced by a scalar field in the bulk by employing zeta function regularization with heat kernel analysis. As a result, the volume is stabilized for most possible choices of the parameters. Especially, for a larger degree of warping, our results imply that a large hierarchy between the mass scales and a tiny amount of effective cosmological constant can be realized on the brane. In the non-warped limit the ratio tends to converge to the same value, independently of the bulk gauge coupling constant. Finally, we will analyze volume stabilization in the original model 6D by employing the same mode-sum technique.
The Casimir effect in rugby-ball type flux compactifications
International Nuclear Information System (INIS)
Minamitsuji, M
2008-01-01
We discuss volume stabilization in a 6D braneworld model based on 6D supergravity theory. The internal space is compactified by magnetic flux and contains codimension two 3-branes (conical singularities) as its boundaries. In general the external 4D spacetime is warped and in the unwrapped limit the shape of the internal space looks like a 'rugby ball'. The size of the internal space is not fixed due to the scale invariance of the supergravity theory. We discuss the possibility of volume stabilization by the Casimir effect for a massless, minimally coupled bulk scalar field. The main obstacle in studying this case is that the brane (conical) part of the relevant heat kernel coefficient (a 6 ) has not been formulated. Thus as a first step, we consider the 4D analog model with boundary codimension two 1-branes. The spacetime structure of the 4D model is very similar to that of the original 6D model, where now the relevant heat kernel coefficient is well known. We derive the one-loop effective potential induced by a scalar field in the bulk by employing zeta function regularization with heat kernel analysis. As a result, the volume is stabilized for most possible choices of the parameters. Especially, for a larger degree of warping, our results imply that a large hierarchy between the mass scales and a tiny amount of effective cosmological constant can be realized on the brane. In the non-warped limit the ratio tends to converge to the same value, independently of the bulk gauge coupling constant. Finally, we will analyze volume stabilization in the original model 6D by employing the same mode-sum technique
International Nuclear Information System (INIS)
Eab, C. H.; Lim, S. C.; Teo, L. P.
2007-01-01
This paper studies the Casimir effect due to fractional massless Klein-Gordon field confined to parallel plates. A new kind of boundary condition called fractional Neumann condition which involves vanishing fractional derivatives of the field is introduced. The fractional Neumann condition allows the interpolation of Dirichlet and Neumann conditions imposed on the two plates. There exists a transition value in the difference between the orders of the fractional Neumann conditions for which the Casimir force changes from attractive to repulsive. Low and high temperature limits of Casimir energy and pressure are obtained. For sufficiently high temperature, these quantities are dominated by terms independent of the boundary conditions. Finally, validity of the temperature inversion symmetry for various boundary conditions is discussed
On the static Casimir effect with parity-breaking mirrors
Energy Technology Data Exchange (ETDEWEB)
Fosco, C.D. [Comision Nacional de Energia Atomica, Centro Atomico Bariloche and Instituto Balseiro, Bariloche (Argentina); Remaggi, M.L. [Universidad Nacional de Cuyo, Facultad de Ciencias Exactas y Naturales, Mendoza (Argentina)
2017-03-15
We study the Casimir interaction energy due to the vacuum fluctuations of the electromagnetic (EM) field in the presence of two mirrors, described by 2+1-dimensional, generally nonlocal actions, which may contain both parity-conserving and parity-breaking terms. We compare the results with the ones corresponding to Chern-Simons boundary conditions and evaluate the interaction energy for several particular situations. (orig.)
On the global Casimir effect in the Schwarzschild spacetime
Muniz, C. R.; Tahim, M. O.; Cunha, M. S.; Vieira, H. S.
2018-01-01
In this paper we study the vacuum quantum fluctuations of the stationary modes of an uncharged scalar field with mass m around a Schwarzschild black hole with mass M, at zero and non-zero temperatures. The procedure consists of calculating the energy eigenvalues starting from the exact solutions found for the dynamics of the scalar field, considering a frequency cutoff in which the particle is not absorbed by the black hole. From this result, we obtain the exterior contributions for the vacuum energy associated to the stationary states of the scalar field, by considering the half-summing of the levels of energy and taking into account the respective degeneracies, in order to better capture the nontrivial topology of the black hole spacetime. Then we use the Riemann's zeta function to regularize the vacuum energy thus found. Such a regularized quantity is the Casimir energy, whose analytic computation we show to yield a convergent series. The Casimir energy obtained does not take into account any boundaries artificially imposed on the system, just the nontrivial spacetime topology associated to the source and its singularity. We suggest that this latter manifests itself through the vacuum tension calculated on the event horizon. We also investigate the problem by considering the thermal corrections via Helmholtz free energy calculation, computing the Casimir internal energy, the corresponding tension on the event horizon, the Casimir entropy, and the thermal capacity of the regularized quantum vacuum, analyzing their behavior at low and high temperatures, pointing out the thermodynamic instability of the system in the considered regime, i.e. mMll 1.
The energy–momentum tensor, the trace identity and the Casimir effect
Indian Academy of Sciences (India)
physics pp. 345–360. The energy–momentum tensor, the trace identity and the Casimir effect. S G KAMATH. Department of Mathematics, Indian Institute of Technology Madras, Chennai 600 036,. India. E-mail: kamath@iitm.ac.in. MS received 11 July 2005; revised 10 October 2005; accepted 18 November 2005. Abstract.
Guo, Hongyu; Stan, Gheorghe; Liu, Yun
2018-02-21
Nanoparticles typically have an inherent wide size distribution that may affect the performance and reliability of many nanomaterials. Because the synthesis and purification of nanoparticles with desirable sizes are crucial to the applications of nanoparticles in various fields including medicine, biology, health care, and energy, there is a great need to search for more efficient and generic methods for size-selective nanoparticle purification/separation. Here we propose and conclusively demonstrate the effectiveness of a size-selective particle purification/separation method based on the critical Casimir force. The critical Casimir force is a generic interaction between colloidal particles near the solvent critical point and has been extensively studied in the past several decades due to its importance in reversibly controlling the aggregation and stability of colloidal particles. Combining multiple experimental techniques, we found that the critical Casimir force-induced aggregation depends on relative particle sizes in a system with larger ones aggregating first and the smaller ones remaining in solution. Based on this observation, a new size-dependent nanoparticle purification/separation method is proposed and demonstrated to be very efficient in purifying commercial silica nanoparticles in the lutidine/water binary solvent. Due to the ubiquity of the critical Casimir force for many colloidal particles in binary solvents, this method might be applicable to many types of colloidal particles.
Casimir effect due to a single boundary as a manifestation of the Weyl problem
Kolomeisky, Eugene B.; Straley, Joseph P.; Langsjoen, Luke S.; Zaidi, Hussain
2010-09-01
The Casimir self-energy of a boundary is ultraviolet-divergent. In many cases, the divergences can be eliminated by methods such as zeta-function regularization or through physical arguments (ultraviolet transparency of the boundary would provide a cutoff). Using the example of a massless scalar field theory with a single Dirichlet boundary, we explore the relationship between such approaches, with the goal of better understanding of the origin of the divergences. We are guided by the insight due to Dowker and Kennedy (1978 J. Phys. A: Math. Gen. 11 895) and Deutsch and Candelas (1979 Phys. Rev. D 20 3063) that the divergences represent measurable effects that can be interpreted with the aid of the theory of the asymptotic distribution of eigenvalues of the Laplacian discussed by Weyl. In many cases, the Casimir self-energy is the sum of cutoff-dependent (Weyl) terms having a geometrical origin, and an 'intrinsic' term that is independent of the cutoff. The Weyl terms make a measurable contribution to the physical situation even when regularization methods succeed in isolating the intrinsic part. Regularization methods fail when the Weyl terms and intrinsic parts of the Casimir effect cannot be clearly separated. Specifically, we demonstrate that the Casimir self-energy of a smooth boundary in two dimensions is a sum of two Weyl terms (exhibiting quadratic and logarithmic cutoff dependence), a geometrical term that is independent of cutoff and a non-geometrical intrinsic term. As by-products, we resolve the puzzle of the divergent Casimir force on a ring and correct the sign of the coefficient of linear tension of the Dirichlet line predicted in earlier treatments.
Resolution of an apparent inconsistency in the electromagnetic Casimir effect
International Nuclear Information System (INIS)
Alnes, H; Olaussen, K; Ravndal, F; Wehus, I K
2007-01-01
The vacuum expectation value of the electromagnetic energy-momentum tensor between two parallel plates in spacetime dimensions D > 4 is calculated in the axial gauge. While the pressure between the plates agrees with the global Casimir force, the energy density is divergent at the plates and not compatible with the total energy which follows from the force. However, subtracting the divergent self-energies of the plates, the resulting energy is finite and consistent with the force. In analogy with the corresponding scalar case for spacetime dimensions D > 2, the divergent self-energy of a single plate can be related to the lack of conformal invariance of the electromagnetic Lagrangian for dimensions D > 4. (fast track communication)
International Nuclear Information System (INIS)
Chaichian, M.; Tureanu, A.; Demichev, A.; Presnajder, P.; Sheikh-Jabbari, M.M.
2001-02-01
After discussing the peculiarities of quantum systems on noncommutative (NC) spaces with nontrivial topology and the operator representation of the *-product on them, we consider the Aharonov-Bohm and Casimir effects for such spaces. For the case of the Aharonov-Bohm effect, we have obtained an explicit expression for the shift of the phase, which is gauge invariant in the NC sense. The Casimir energy of a field theory on a NC cylinder is divergent, while it becomes finite on a torus, when the dimensionless parameter of noncommutativity is a rational number. The latter corresponds to a well-defined physical picture. Certain distinctions from other treatments based on a different way of taking the noncommutativity into account are also discussed. (author)
Vortex loops in the critical Casimir effect in superfluid and superconducting films
International Nuclear Information System (INIS)
Williams, Gary A.
2004-01-01
Vortex-loop renormalization techniques are used to calculate the magnitude of the critical Casimir forces in superfluid and superconducting thin films. The force is found to become appreciable when the size of the thermally excited vortex loops is comparable to the film thickness, and the results for T c are found to match very well with perturbative renormalization-group theories that can only be carried out for T>T c . In helium films the Casimir force leads to a change in the film thickness close to T c that has been observed experimentally. A similar effect is predicted to occur near the transition temperature of high-T c superconducting films, which is also a vortex-loop phase transition. In this case the Casimir force takes the form of a voltage difference that will appear at the junction between a thin film and a bulk sample. Estimates show that this voltage can be appreciable (tens of microvolts), and it may be possible to observe the effect by measuring the voltage across two Josephson tunnel junctions to the film and to the bulk, using a SQUID voltmeter
Determination of the Contact Angle Based on the Casimir Effect
Mazuruk, Konstantin; Volz, Martin P.
2015-01-01
On a macroscopic scale, a nonreactive liquid partially covering a homogeneous solid surface will intersect the solid at an angle called the contact angle. For molten metals and semiconductors, the contact angle is materially dependent upon both the solid and liquid and typical values fall in the range 80-170 deg, depending on the crucible material. On a microscopic scale, there does not exist a precise and sharp contact angle but rather the liquid and solid surfaces merge smoothly and continuously. Consider the example of the so called detached Bridgman crystal growth process. In this technique, a small gap is formed between the growing crystal and the crucible. At the crystal/melt interface, a meniscus ring is formed. Its width can be in the range of a few micrometers, approaching a microscopic scale. It then becomes questionable to describe the shape of this meniscus by the contact angle. A more advanced treatment of the interface is needed and here we propose such a refined model. The interaction of the liquid surface with the solid can be calculated by considering two forces: a short-range repulsive force and a longer range (up to a few micrometers) Casimir or van der Waals force.
Particle creation by a black hole as a consequence of the Casimir effect
Nugayev, R. M.
1987-12-01
Particle creation by a black hole is investigated in terms of temperature corrections to the Casimir effect. The reduction of the Hawking effect to more familiar effects observed in the laboratory enables us to reveal the mechanism of particle creation. The blackbody nature of the Hawking radiation is due to the interaction of virtual particles with the surface of a “cavity” formed by the Schwarzschild gravitational field potential barrier. These particles are “squeezed out” by the contraction of the potential barrier and appear to an observer at J + as the real blackbody ones.
International Nuclear Information System (INIS)
Graham, N.; Jaffe, R.L.; Khemani, V.; Quandt, M.; Schroeder, O.; Weigel, H.
2004-01-01
Casimir forces are conventionally computed by analyzing the effects of boundary conditions on a fluctuating quantum field. Although this analysis provides a clean and calculationally tractable idealization, it does not always accurately capture the characteristics of real materials, which cannot constrain the modes of the fluctuating field at all energies. We study the vacuum polarization energy of renormalizable, continuum quantum field theory in the presence of a background field, designed to impose a Dirichlet boundary condition in a particular limit. We show that in two and three space dimensions, as a background field becomes concentrated on the surface on which the Dirichlet boundary condition would eventually hold, the Casimir energy diverges. This result implies that the energy depends in detail on the properties of the material, which are not captured by the idealized boundary conditions. This divergence does not affect the force between rigid bodies, but it does invalidate calculations of Casimir stresses based on idealized boundary conditions
Zeta Function Regularization in Casimir Effect Calculations and J. S. Dowker's Contribution
Elizalde, Emilio
2012-07-01
A summary of relevant contributions, ordered in time, to the subject of operator zeta functions and their application to physical issues is provided. The description ends with the seminal contributions of Stephen Hawking and Stuart Dowker and collaborators, considered by many authors as the actual starting point of the introduction of zeta function regularization methods in theoretical physics, in particular, for quantum vacuum fluctuation and Casimir effect calculations. After recalling a number of the strengths of this powerful and elegant method, some of its limitations are discussed. Finally, recent results of the so called operator regularization procedure are presented.
Nori, Franco
2012-02-01
This talk will present an overview of some of our recent results on atomic physics and quantum optics using superconducting circuits. Particular emphasis will be given to photons interacting with qubits, interferometry, the Dynamical Casimir effect, and also studying Majorana fermions using superconducting circuits.[4pt] References available online at our web site:[0pt] J.Q. You, Z.D. Wang, W. Zhang, F. Nori, Manipulating and probing Majorana fermions using superconducting circuits, (2011). Arxiv. J.R. Johansson, G. Johansson, C.M. Wilson, F. Nori, Dynamical Casimir effect in a superconducting coplanar waveguide, Phys. Rev. Lett. 103, 147003 (2009). [0pt] J.R. Johansson, G. Johansson, C.M. Wilson, F. Nori, Dynamical Casimir effect in superconducting microwave circuits, Phys. Rev. A 82, 052509 (2010). [0pt] C.M. Wilson, G. Johansson, A. Pourkabirian, J.R. Johansson, T. Duty, F. Nori, P. Delsing, Observation of the Dynamical Casimir Effect in a superconducting circuit. Nature, in press (Nov. 2011). P.D. Nation, J.R. Johansson, M.P. Blencowe, F. Nori, Stimulating uncertainty: Amplifying the quantum vacuum with superconducting circuits, Rev. Mod. Phys., in press (2011). [0pt] J.Q. You, F. Nori, Atomic physics and quantum optics using superconducting circuits, Nature 474, 589 (2011). [0pt] S.N. Shevchenko, S. Ashhab, F. Nori, Landau-Zener-Stuckelberg interferometry, Phys. Reports 492, 1 (2010). [0pt] I. Buluta, S. Ashhab, F. Nori. Natural and artificial atoms for quantum computation, Reports on Progress in Physics 74, 104401 (2011). [0pt] I.Buluta, F. Nori, Quantum Simulators, Science 326, 108 (2009). [0pt] L.F. Wei, K. Maruyama, X.B. Wang, J.Q. You, F. Nori, Testing quantum contextuality with macroscopic superconducting circuits, Phys. Rev. B 81, 174513 (2010). [0pt] J.Q. You, X.-F. Shi, X. Hu, F. Nori, Quantum emulation of a spin system with topologically protected ground states using superconducting quantum circuit, Phys. Rev. A 81, 063823 (2010).
The generalized Abel-Plana formula. Applications to Bessel functions and Casimir effect
International Nuclear Information System (INIS)
Saharian, A.A.; Institute of Applied Problems in Physics NAS RA, Yerevan; Abdus Salam International Centre for Theoretical Physics, Trieste
2000-02-01
One of the most efficient methods to obtain the vacuum expectation values for the physical observables in the Casimir effect is based on using the Abel-Plana summation formula. This allows us to derive the regularized quantities in a manifestly cutoff independent way and present them in the form of strongly convergent integrals. However, the application of Abel-Plana formula, in its usual form, is restricted by simple geometries when the eigenmodes have a simple dependence on quantum numbers. The author generalized the Abel-Plana formula which essentially enlarges its application range. Based on this generalization, formulae have been obtained for various types of series over the zeros of some combinations of Bessel functions and for integrals involving these functions. It has been shown that these results generalize the special cases existing in literature. Further, the derived summation formulae have been used to summarize series arising in the mode summation approach to the Casimir effect for spherically and cylindrically symmetric boundaries. This allows us to extract the divergent parts from the vacuum expectation values for the local physical observables in a manifestly cutoff independent way. The present paper reviews these results. Some new considerations are also added. (author)
Energy Technology Data Exchange (ETDEWEB)
Torres-Guzman, Jose C [Centro de Ciencias FIsicas, Universidad Nacional Autonoma de Mexico, Apartado Postal 48-3, 62251 Cuernavaca, Morelos (Mexico); Mochan, W Luis [Centro de Ciencias FIsicas, Universidad Nacional Autonoma de Mexico, Apartado Postal 48-3, 62251 Cuernavaca, Morelos (Mexico)
2006-05-26
We develop a formalism for the calculation of the flow of angular momentum carried by the fluctuating electromagnetic field within a cavity bounded by two flat anisotropic materials. By generalizing a procedure employed recently for the calculation of the Casimir force between arbitrary materials, we obtain an expression for the torque between anisotropic plates in terms of their reflection amplitude matrices. We evaluate the torque in 1D for ideal and dispersive model materials.
International Nuclear Information System (INIS)
Rego, Andreson L.C.; Farina, Carlos; Alves, J.P.S.; Alves, Danilo T.
2012-01-01
Full text: The creation of real particles from vacuum induced by moving mirrors with non-uniform acceleration is a quantum vacuum effect usually called dynamical Casimir effect (DCE). The radiation reaction force acting on this moving plate is an alternative manner to explain this fascinating effect. The theoretical prediction of the DCE was made by Moore in 1970 (J Math. Phys. 11, 2679, (1970)), considering a cavity with a moving boundary, and a real massless scalar field in a two-dimensional space-time. DeWitt (Phys. Rep. 19, 295 (1975)), Fulling and Davies (Proc. R. Soc. London, A 348, 393 (1976)) also investigated the DCE with the same two-dimensional model, but with just a single moving mirror, the simplest way to produce the Casimir radiation. The experimental measure of the DCE can be treated as a direct confirmation of existence of vacuum fluctuations. In the single mirror problem, for realistic parameters, the amount of created particles is not appreciable. In order to remove this difficulty, several experimental proposals were presented to detect the radiation generated by the DCE. More than 40 years after its first theoretical prediction, the DCE was observed by Wilson and collaborators (Nature, 479, 376, (2011)) in the context of circuit Quantum Electrodynamics (circuit-QED). The experiment was based on a superconducting circuit consisting in a coplanar waveguide terminated by a SQUID (a sensitive magnetometer). The presence of time-dependent magnetic fluxes enable fast modulations in the electrical length of the transmission line. This setup simulates a moving mirror whose effective velocity can achieve 0:1 of velocity of light. In the present work, taking into account the fact of the effective velocity implemented on the first experimental observation of the DCE is a substantial fraction of velocity of light, we investigate relativistic effects in the particle creation via DCE in a superconducting circuit. Considering a massless scalar field in 1
Amplification of the parametric dynamical Casimir effect via optimal control
Hoeb, Fabian; Angaroni, Fabrizio; Zoller, Jonathan; Calarco, Tommaso; Strini, Giuliano; Montangero, Simone; Benenti, Giuliano
2017-09-01
We introduce different strategies to enhance photon generation in a cavity within the Rabi model in the ultrastrong coupling regime. We show that a bang-bang strategy allows one to enhance the effect up to 1 order of magnitude with respect to simply driving the system in resonance for a fixed time. Moreover, up to about another order of magnitude can be gained by exploiting quantum optimal control strategies. Finally, we show that such optimized protocols are robust with respect to systematic errors and noise, paving the way to future experimental implementations of such strategies.
Energy Technology Data Exchange (ETDEWEB)
Grueneberg, Daniel
2008-02-15
To study how the behavior of the thermodynamic Casimir force changes qualitatively and quantitatively due to the presence of such interactions - compared to systems with purely short-range interactions - is the aim of this work. Considering d-dimensional models belonging to the universality class of the O(n)-symmetrical systems, the thermodynamic Casimir force and its leading corrections are derived for temperatures at and above the transition temperature (T{>=}T{sub c,{infinity}}). The underlying pair potential is assumed to be isotropic and long-ranged, decaying asymptotically proportional to x{sup -(d+{sigma}}{sup )} for large separations x, where the value of the parameter {sigma} is restricted to the interval 2<{sigma}<4. By solving an appropriate spherical model in 2
Garrett, Joseph L; Somers, David; Munday, Jeremy N
2015-06-03
Measurements of the Casimir force require the elimination of the electrostatic force between the surfaces. However, due to electrostatic patch potentials, the voltage required to minimize the total force may not be sufficient to completely nullify the electrostatic interaction. Thus, these surface potential variations cause an additional force, which can obscure the Casimir force signal. In this paper, we inspect the spatially varying surface potential of e-beamed, sputtered, sputtered and annealed, and template stripped gold surfaces with Heterodyne amplitude modulated Kelvin probe force microscopy (HAM-KPFM). It is demonstrated that HAM-KPFM improves the spatial resolution of surface potential measurements compared to amplitude modulated Kelvin probe force microscopy. We find that patch potentials vary depending on sample preparation, and that the calculated pressure can be similar to the pressure difference between Casimir force calculations employing the plasma and Drude models.
Oscillating Casimir force between two slabs in a Fermi sea
DEFF Research Database (Denmark)
Li-Wei, Chen; Guo-Zhen, Su; Jin-Can, Chen
2012-01-01
The Casimir effect for two parallel slabs immersed in an ideal Fermi sea is investigated at both zero and nonzero temperatures. It is found that the Casimir effect in a Fermi gas is distinctly different from that in an electromagnetic field or a massive Bose gas. In contrast to the familiar result...... that the Casimir force decreases monotonically with the increase of the separation L between two slabs in an electromagnetic field and a massive Bose gas, the Casimir force in a Fermi gas oscillates as a function of L. The Casimir force can be either attractive or repulsive, depending sensitively on the magnitude...... of L. In addition, it is found that the amplitude of the Casimir force in a Fermi gas decreases with the increase of the temperature, which also is contrary to the case in a Bose gas, since the bosonic Casimir force increases linearly with the increase of the temperature in the region T
International Nuclear Information System (INIS)
Fosco, Cesar D.; Lombardo, Fernando C.
2015-01-01
We study the properties of the classical electromagnetic radiation produced by two physically different yet closely related systems, which may be regarded as classical analogues of the dynamical Casimir effect. They correspond to two flat, infinite, parallel planes, one of them static and imposing perfect-conductor boundary conditions, while the other performs a rigid oscillatory motion. The systems differ just in the electrical properties of the oscillating plane: one of them is just a planar dipole layer (representing, for instance, a small-width electret). The other, instead, has a dipole layer on the side which faces the static plane, but behaves as a conductor on the other side: this can be used as a representation of a conductor endowed with patch potentials (on the side which faces the conducting plane). We evaluate, in both cases, the dissipative flux of energy between the system and its environment, showing that, at least for small mechanical oscillation amplitudes, it can be written in terms of the dipole layer autocorrelation function. We show that there are resonances as a function of the frequency of the mechanical oscillation. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Fosco, Cesar D. [Comision Nacional de Energia Atomica, Centro Atomico Bariloche, Instituto Balseiro, Bariloche (Argentina); Lombardo, Fernando C. [Ciudad Universitaria, Departamento de Fisica Juan Jose Giambiagi, FCEyN UBA y IFIBA CONICET-UBA, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)
2015-12-15
We study the properties of the classical electromagnetic radiation produced by two physically different yet closely related systems, which may be regarded as classical analogues of the dynamical Casimir effect. They correspond to two flat, infinite, parallel planes, one of them static and imposing perfect-conductor boundary conditions, while the other performs a rigid oscillatory motion. The systems differ just in the electrical properties of the oscillating plane: one of them is just a planar dipole layer (representing, for instance, a small-width electret). The other, instead, has a dipole layer on the side which faces the static plane, but behaves as a conductor on the other side: this can be used as a representation of a conductor endowed with patch potentials (on the side which faces the conducting plane). We evaluate, in both cases, the dissipative flux of energy between the system and its environment, showing that, at least for small mechanical oscillation amplitudes, it can be written in terms of the dipole layer autocorrelation function. We show that there are resonances as a function of the frequency of the mechanical oscillation. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Fosco, César D. [Centro Atómico Bariloche, Instituto Balseiro, Comisión Nacional de Energía Atómica, R8402AGP, Bariloche (Argentina); Lombardo, Fernando C., E-mail: lombardo@df.uba.ar [Departamento de Física Juan José Giambiagi, FCEyN UBA and IFIBA CONICET-UBA, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria, Pabellón I, 1428, Buenos Aires (Argentina)
2015-12-17
We study the properties of the classical electromagnetic radiation produced by two physically different yet closely related systems, which may be regarded as classical analogues of the dynamical Casimir effect. They correspond to two flat, infinite, parallel planes, one of them static and imposing perfect-conductor boundary conditions, while the other performs a rigid oscillatory motion. The systems differ just in the electrical properties of the oscillating plane: one of them is just a planar dipole layer (representing, for instance, a small-width electret). The other, instead, has a dipole layer on the side which faces the static plane, but behaves as a conductor on the other side: this can be used as a representation of a conductor endowed with patch potentials (on the side which faces the conducting plane). We evaluate, in both cases, the dissipative flux of energy between the system and its environment, showing that, at least for small mechanical oscillation amplitudes, it can be written in terms of the dipole layer autocorrelation function. We show that there are resonances as a function of the frequency of the mechanical oscillation.
The Casimir Effect from the Point of View of Algebraic Quantum Field Theory
Energy Technology Data Exchange (ETDEWEB)
Dappiaggi, Claudio, E-mail: claudio.dappiaggi@unipv.it; Nosari, Gabriele [Università degli Studi di Pavia, Dipartimento di Fisica (Italy); Pinamonti, Nicola [Università di Genova, Dipartimento di Matematica (Italy)
2016-06-15
We consider a region of Minkowski spacetime bounded either by one or by two parallel, infinitely extended plates orthogonal to a spatial direction and a real Klein-Gordon field satisfying Dirichlet boundary conditions. We quantize these two systems within the algebraic approach to quantum field theory using the so-called functional formalism. As a first step we construct a suitable unital ∗-algebra of observables whose generating functionals are characterized by a labelling space which is at the same time optimal and separating and fulfils the F-locality property. Subsequently we give a definition for these systems of Hadamard states and we investigate explicit examples. In the case of a single plate, it turns out that one can build algebraic states via a pull-back of those on the whole Minkowski spacetime, moreover inheriting from them the Hadamard property. When we consider instead two plates, algebraic states can be put in correspondence with those on flat spacetime via the so-called method of images, which we translate to the algebraic setting. For a massless scalar field we show that this procedure works perfectly for a large class of quasi-free states including the Poincaré vacuum and KMS states. Eventually Wick polynomials are introduced. Contrary to the Minkowski case, the extended algebras, built in globally hyperbolic subregions can be collected in a global counterpart only after a suitable deformation which is expressed locally in terms of a *-isomorphism. As a last step, we construct explicitly the two-point function and the regularized energy density, showing, moreover, that the outcome is consistent with the standard results of the Casimir effect.
Thermal Casimir effect in Kerr spacetime with quintessence and massive gravitons
Energy Technology Data Exchange (ETDEWEB)
Bezerra, V.B. [Universidade Federal da Paraiba, Departamento de Fisica, Joao Pessoa, PB (Brazil); Christiansen, H.R. [Ciencia e Tecnologia do Ceara (IFCE), Departamento de Fisica, Instituto Federal de Educacao, Sobral, CE (Brazil); Cunha, M.S. [Universidade Estadual do Ceara, Grupo de Fisica Teorica (GFT), Fortaleza, CE (Brazil); Muniz, C.R.; Tahim, M.O. [Universidade Estadual do Ceara, Faculdade de Educacao, Ciencias e Letras do Sertao Central, Quixada, CE (Brazil)
2017-11-15
Starting from an analytical expression for the Helmholtz free energy we calculate the thermal corrections to the Casimir energy density and entropy within nearby ideal parallel plates in the vacuum of a massless scalar field. Our framework is the Kerr spacetime in the presence of quintessence and massive gravitons. The high and low temperature regimes are especially analyzed in order to distinguish the main contributions. For instance, in the high temperature regime, we show that the force between the plates is repulsive and grows with both the quintessence and the massive gravitons. Regarding the Casimir entropy, our results are in agreement with the Nernst heat theorem and therefore confirm the third law of thermodynamics in the present scenario. (orig.)
Out-of-equilibrium relaxation of the thermal Casimir effect in a model polarizable material.
Dean, David S; Démery, Vincent; Parsegian, V Adrian; Podgornik, Rudolf
2012-03-01
Relaxation of the thermal Casimir or van der Waals force (the high temperature limit of the Casimir force) for a model dielectric medium is investigated. We start with a model of interacting polarization fields with a dynamics that leads to a frequency dependent dielectric constant of the Debye form. In the static limit, the usual zero frequency Matsubara mode component of the Casimir force is recovered. We then consider the out-of-equilibrium relaxation of the van der Waals force to its equilibrium value when two initially uncorrelated dielectric bodies are brought into sudden proximity. For the interaction between dielectric slabs, it is found that the spatial dependence of the out-of-equilibrium force is the same as the equilibrium one, but it has a time dependent amplitude, or Hamaker coefficient, which increases in time to its equilibrium value. The final relaxation of the force to its equilibrium value is exponential in systems with a single or finite number of polarization field relaxation times. However, in systems, such as those described by the Havriliak-Negami dielectric constant with a broad distribution of relaxation times, we observe a much slower power law decay to the equilibrium value.
Archimedes force on Casimir apparatus
Directory of Open Access Journals (Sweden)
Shevchenko V.
2016-01-01
Full Text Available The talk addresses a problem of Casimir apparatus in weak gravitational field, surrounded by a dense medium. The falling of the apparatus has to be governed by the equivalence principle, taking into account proper contributions to the weight of the apparatus from its material part and from distorted quantum fields. We discuss general ex pression for the corresponding force in terms of the effective action. By way of example we compute explicit expression for Archimedes force, acting on the Casimir apparatus of finite size, immersed into thermal bath of free scalar field. It is shown that besides universal term, proportional to the volume of the apparatus, there are non-universal quantum corrections, depending on the boundary conditions.
The Reality of Casimir Friction
Directory of Open Access Journals (Sweden)
Kimball A. Milton
2016-04-01
Full Text Available For more than 35 years theorists have studied quantum or Casimir friction, which occurs when two smooth bodies move transversely to each other, experiencing a frictional dissipative force due to quantum electromagnetic fluctuations, which break time-reversal symmetry. These forces are typically very small, unless the bodies are nearly touching, and consequently such effects have never been observed, although lateral Casimir forces have been seen for corrugated surfaces. Partly because of the lack of contact with observations, theoretical predictions for the frictional force between parallel plates, or between a polarizable atom and a metallic plate, have varied widely. Here, we review the history of these calculations, show that theoretical consensus is emerging, and offer some hope that it might be possible to experimentally confirm this phenomenon of dissipative quantum electrodynamics.
Nonlinear (Anharmonic Casimir Oscillator
Directory of Open Access Journals (Sweden)
Habibollah Razmi
2011-01-01
Full Text Available We want to study the dynamics of a simple linear harmonic micro spring which is under the influence of the quantum Casimir force/pressure and thus behaves as a (an nonlinear (anharmonic Casimir oscillator. Generally, the equation of motion of this nonlinear micromechanical Casimir oscillator has no exact solvable (analytical solution and the turning point(s of the system has (have no fixed position(s; however, for particular values of the stiffness of the micro spring and at appropriately well-chosen distance scales and conditions, there is (are approximately sinusoidal solution(s for the problem (the variable turning points are collected in a very small interval of positions. This, as a simple and elementary plan, may be useful in controlling the Casimir stiction problem in micromechanical devices.
Casimir effect for parallel plates in a Friedmann-Robertson-Walker universe
Bezerra de Mello, E. R.; Saharian, A. A.; Setare, M. R.
2017-03-01
We evaluate the Hadamard function, the vacuum expectation values (VEVs) of the field squared and the energy-momentum tensor for a massive scalar field with a general curvature coupling parameter in the geometry of two parallel plates on a spatially flat Friedmann-Robertson-Walker background with a general scale factor. On the plates, the field operator obeys the Robin boundary conditions with the coefficients depending on the scale factor. In all the spatial regions, the VEVs are decomposed into the boundary-free and boundary-induced contributions. Unlike the problem with the Minkowski bulk, in the region between the plates, the normal stress is not homogeneous and does not vanish in the geometry of a single plate. Near the plates, it has different signs for accelerated and decelerated expansions of the Universe. The VEV of the energy-momentum tensor, in addition to the diagonal components, has a nonzero off-diagonal component describing an energy flux along the direction normal to the boundaries. Expressions are derived for the Casimir forces acting on the plates. Depending on the Robin coefficients and on the vacuum state, these forces can be either attractive or repulsive. An important difference from the corresponding result in the Minkowski bulk is that the forces on the separate plates, in general, are different if the corresponding Robin coefficients differ. We give the applications of general results for the class of α vacua in the de Sitter bulk. It is shown that, compared with the Bunch-Davies vacuum state, the Casimir forces for a given α vacuum may change the sign.
Energy Technology Data Exchange (ETDEWEB)
Fischer, D.J.
2008-01-15
We study the Casimir energy density of the Klein-Gordon-field in the case of two static geometries. We model the effect by coupling the free quantum field to a static classical scalar field. We work out the dependence on the coupling {lambda}, including the limit {lambda}={infinity} (Dirichlet boundary condition). The chosen geometries are described by a {delta}-funktion ({sigma}(x)={delta}(x{sub 3})) and a step function of finite height ({sigma}(x)= (1)/(2{epsilon})1{sub [{epsilon},{epsilon}]}(x{sub 3})), respectively. In the area outside the support of the background the density energy converges; calculations for the distorted area lead to divergent surface terms. (orig.)
International Nuclear Information System (INIS)
Soroush, R; Koochi, A; Haddadpour, H; Kazemi, A S; Noghrehabadi, A; Abadyan, M
2010-01-01
This paper investigates the effect of dispersion (van der Waals and Casimir) forces on the pull-in instability of cantilever nano-actuators by considering their range of application. Adomian decomposition is introduced to obtain an analytical solution of the distributed parameter model. Dispersion forces decrease the pull-in deflection and voltage of a nano-actuator. However, the fringing field increases the pull-in deflection while decreasing the pull-in voltage of the actuator. The minimum initial gap and the detachment length of the actuator that does not stick to the substrate due to van der Waals and Casimir attractions were determined. Furthermore, the proposed approach is capable of determining the stress distribution of the actuator at the onset of instability. It is seen that Casimir and van der Waals attractions effectively reduce the maximum value of stress resultants at the onset of instability. The results indicate that Adomian decomposition is a reliable method for simulating nano-structures at submicrometer ranges.
Halving the Casimir force with Conductive Oxides
de Man, S.P.J.; Heeck, K.; Wijngaarden, R.J.; Iannuzzi, D.
2009-01-01
The possibility to modify the strength of the Casimir effect by tailoring the dielectric functions of the interacting surfaces is regarded as a unique opportunity in the development of micro- and nanoelectromechanical systems. In air, however, one expects that, unless noble metals are used, the
Casimir energy and the possibility of higher dimensional manipulation
Obousy, R. K.; Saharian, A. A.
2009-01-01
It is well known that the Casimir effect is an excellent candidate for the stabilization of the extra dimensions. It has also been suggested that the Casimir effect in higher dimensions may be the underlying phenomenon that is responsible for the dark energy which is currently driving the accelerated expansion of the universe. In this paper we suggest that, in principle, it may be possible to directly manipulate the size of an extra dimension locally using Standard Model fields in the next ge...
Casimir Energy, Extra Dimensions and Exotic Propulsion
Obousy, R.; Saharian, A.
It is well known that the Casimir effect is an excellent candidate for the stabilization of the extra dimensions. It has also been suggested that the Casimir effect in higher dimensions may be the underlying phenomenon that is responsible for the dark energy which is currently driving the accelerated expansion of the universe. In this paper we suggest that, in principle, it may be possible to directly manipulate the size of an extra dimension locally using Standard Model fields in the next generation of particle accelerators. This adjustment of the size of the higher dimension could serve as a technological mechanism to locally adjust the dark energy density and change the local expansion of spacetime. This idea holds tantalizing possibilities in the context of exotic spacecraft propulsion.
Casimir interactions between graphene sheets and metamaterials
International Nuclear Information System (INIS)
Drosdoff, D.; Woods, Lilia M.
2011-01-01
The Casimir force between graphene sheets and metamaterials is studied. Theoretical results based on the Lifshitz theory for layered, planar, two-dimensional systems in media are presented. We consider graphene-graphene, graphene-metamaterial, and metal-graphene-metamaterial configurations. We find that quantum effects of the temperature-dependent force are not apparent until the submicron range. In contrast to results with bulk dielectric and bulk metallic materials, no Casimir repulsion is found when graphene is placed on top of a magnetically active metamaterial substrate, regardless of the strength of the low-frequency magnetic response. In the case of the metal-graphene-metamaterial setting, repulsion between the metamaterial and the metal-graphene system is possible only when the dielectric response from the metal contributes significantly.
Graphene cantilever under Casimir force
Derras-Chouk, Amel; Chudnovsky, Eugene M.; Garanin, Dmitry A.; Jaafar, Reem
2018-05-01
The stability of graphene cantilever under Casimir attraction to an underlying conductor is investigated. The dependence of the instability threshold on temperature and flexural rigidity is obtained. Analytical work is supplemented by numerical computation of the critical temperature above which the graphene cantilever irreversibly bends down and attaches to the conductor. The geometry of the attachment and exfoliation of the graphene sheet is discussed. It is argued that graphene cantilever can be an excellent tool for precision measurements of the Casimir force.
Casimir-Polder interaction in second quantization
Energy Technology Data Exchange (ETDEWEB)
Schiefele, Juergen
2011-03-21
The Casimir-Polder interaction between a single neutral atom and a nearby surface, arising from the (quantum and thermal) fluctuations of the electromagnetic field, is a cornerstone of cavity quantum electrodynamics (cQED), and theoretically well established. Recently, Bose-Einstein condensates (BECs) of ultracold atoms have been used to test the predictions of cQED. The purpose of the present thesis is to upgrade single-atom cQED with the many-body theory needed to describe trapped atomic BECs. Tools and methods are developed in a second-quantized picture that treats atom and photon fields on the same footing. We formulate a diagrammatic expansion using correlation functions for both the electromagnetic field and the atomic system. The formalism is applied to investigate, for BECs trapped near surfaces, dispersion interactions of the van der Waals-Casimir-Polder type, and the Bosonic stimulation in spontaneous decay of excited atomic states. We also discuss a phononic Casimir effect, which arises from the quantum fluctuations in an interacting BEC. (orig.)
Casimir-Polder interaction in second quantization
International Nuclear Information System (INIS)
Schiefele, Juergen
2011-01-01
The Casimir-Polder interaction between a single neutral atom and a nearby surface, arising from the (quantum and thermal) fluctuations of the electromagnetic field, is a cornerstone of cavity quantum electrodynamics (cQED), and theoretically well established. Recently, Bose-Einstein condensates (BECs) of ultracold atoms have been used to test the predictions of cQED. The purpose of the present thesis is to upgrade single-atom cQED with the many-body theory needed to describe trapped atomic BECs. Tools and methods are developed in a second-quantized picture that treats atom and photon fields on the same footing. We formulate a diagrammatic expansion using correlation functions for both the electromagnetic field and the atomic system. The formalism is applied to investigate, for BECs trapped near surfaces, dispersion interactions of the van der Waals-Casimir-Polder type, and the Bosonic stimulation in spontaneous decay of excited atomic states. We also discuss a phononic Casimir effect, which arises from the quantum fluctuations in an interacting BEC. (orig.)
On convergence generation in computing the electro-magnetic Casimir force
International Nuclear Information System (INIS)
Schuller, F.
2008-01-01
We tackle the very fundamental problem of zero-point energy divergence in the context of the Casimir effect. We calculate the Casimir force due to field fluctuations by using standard cavity radiation modes. The validity of convergence generation by means of an exponential energy cut-off factor is discussed in detail. (orig.)
Banishev, Alexandr; Chang, Chia-Cheng; Mohideen, Umar
2012-02-01
The Casimir effect is important in various fields from atomic physics to nanotechnology. According to the Lifshitz theory of the Casimir force, the interaction between two objects depends both on their dielectric permittivity and magenetic permeability. Thus the role of magnetic properties on the Casimir force is interesting particularly due to the possibility of a reduction the Casimir force. In this report we will present the results of a Casimir force measurement between a magnetic material such as nickel coated on SiO2 plate and a Au-coated sphere.
Some new results of the Casimir force for rectangular cavity
International Nuclear Information System (INIS)
Zhai, X.-H.; Li, X.-Z.
2001-01-01
The Casimir effect giving rise to an attractive or repulsive force between the configuration boundaries that confine the massless scalar field is analytically approached for a p-dimensional rectangular cavity with the Dirichlet boundary conditions and different spacetime dimensions D. The Casimir force is attractive in the cases: i) p-odd hypercube when D is less than the critical dimension D c and p ≤ 29; ii) o =2 and the length ratio is less than a critical value; iii) p = 1. The Casimir force is repulsive in the cases: i) p = 2 and the length ratio is larger than a critical value; ii) the length of q edges is equal and others are much longer than q edges, in the direction of (p-q) edges; iii) (p-q) edges are much longer than q edges, in the direction of (p-q) edges
Thermal Fluctuations in Casimir Pistons
Lomnitz, M.; Villarreal, C.
2012-07-01
We present analytical and simple expressions to determine the free energy, internal energy, entropy, as well as the pressure acting at the interface of a perfectly conducting rectangular Casimir piston. We show that infrared divergencies linear in temperature become cancelled within the piston configuration, and show a continuous behavior consistent with intuitive expectations.
Supersymmetry Breaking Casimir Warp Drive
Obousy, Richard K.; Cleaver, Gerald
2007-01-01
This paper utilizes a recent model which relates the cosmological constant to the Casimir energy of the extra dimensions in brane-world theories. The objective of this paper is to demonstrate that, given some sufficiently advanced civilization with the ability to manipulate the radius of the extra dimension, a local adjustment of the cosmological constant could be created. This adjustment would facilitate an expansion/contraction of the spacetime around a spacecraft creating an exotic form of field-propulsion. This idea is analogous to the Alcubierre bubble, but differs entirely in the approach, utilizing the physics of higher dimensional quantum field theory, instead of general relativity.
Theoretical ingredients of a Casimir analog computer.
Rodriguez, Alejandro W; McCauley, Alexander P; Joannopoulos, John D; Johnson, Steven G
2010-05-25
We derive a correspondence between the contour integration of the Casimir stress tensor in the complex-frequency plane and the electromagnetic response of a physical dissipative medium in a finite real-frequency bandwidth. The consequences of this correspondence are at least threefold: First, the correspondence makes it easier to understand Casimir systems from the perspective of conventional classical electromagnetism, based on real-frequency responses, in contrast to the standard imaginary-frequency point of view based on Wick rotations. Second, it forms the starting point of finite-difference time-domain numerical techniques for calculation of Casimir forces in arbitrary geometries. Finally, this correspondence is also key to a technique for computing quantum Casimir forces at micrometer scales using antenna measurements at tabletop (e.g., centimeter) scales, forming a type of analog computer for the Casimir force. Superficially, relationships between the Casimir force and the classical electromagnetic Green's function are well known, so one might expect that any experimental measurement of the Green's function would suffice to calculate the Casimir force. However, we show that the standard forms of this relationship lead to infeasible experiments involving infinite bandwidth or exponentially growing fields, and a fundamentally different formulation is therefore required.
Casimir Interaction from Magnetically Coupled Eddy Currents
Intravaia, Francesco; Henkel, Carsten
2009-09-01
We study the quantum and thermal fluctuations of eddy (Foucault) currents in thick metallic plates. A Casimir interaction between two plates arises from the coupling via quasistatic magnetic fields. As a function of distance, the relevant eddy current modes cross over from a quantum to a thermal regime. These modes alone reproduce previously discussed thermal anomalies of the electromagnetic Casimir interaction between good conductors. In particular, they provide a physical picture for the Casimir entropy whose nonzero value at zero temperature arises from a correlated, glassy state.
Casimir interaction between spheres in (D+1)-dimensional Minkowski spacetime
Energy Technology Data Exchange (ETDEWEB)
Teo, L.P. [Department of Applied Mathematics, Faculty of Engineering, University of Nottingham Malaysia Campus, Jalan Broga, 43500, Semenyih, Selangor Darul Ehsan (Malaysia)
2014-05-06
We consider the Casimir interaction between two spheres in (D+1)-dimensional Minkowski spacetime due to the vacuum fluctuations of scalar fields. We consider combinations of Dirichlet and Neumann boundary conditions. The TGTG formula of the Casimir interaction energy is derived. The computations of the T matrices of the two spheres are straightforward. To compute the two G matrices, known as translation matrices, which relate the hyper-spherical waves in two spherical coordinate frames differ by a translation, we generalize the operator approach employed in R.C. Wittman, Spherical Wave Operators and the Translation Formulas, IEEE Trans. Antennas Propag. 36 (1988) 1078. . The result is expressed in terms of an integral over Gegenbauer polynomials. In contrast to the D=3 case, we do not re-express the integral in terms of 3j-symbols and hyper-spherical waves, which in principle, can be done but does not simplify the formula. Using our expression for the Casimir interaction energy, we derive the large separation and small separation asymptotic expansions of the Casimir interaction energy. In the large separation regime, we find that the Casimir interaction energy is of order L{sup −2D+3}, L{sup −2D+1} and L{sup −2D−1} respectively for Dirichlet-Dirichlet, Dirichlet-Neumann and Neumann-Neumann boundary conditions, where L is the center-to-center distance of the two spheres. In the small separation regime, we confirm that the leading term of the Casimir interaction agrees with the proximity force approximation, which is of order d{sup −((D+1)/2)}, where d is the distance between the two spheres. Another main result of this work is the analytic computations of the next-to-leading order term in the small separation asymptotic expansion. This term is computed using careful order analysis as well as perturbation method. In the case the radius of one of the sphere goes to infinity, we find that the results agree with the one we derive for sphere-plate configuration
Casimir force between two Aharonov-Bohm selenoids
International Nuclear Information System (INIS)
Duru, I.H.
1989-06-01
We show that a force of Casimir type case be associated with the Aharonov-Bohm effect. We consider two parallel, infinitely long and thin selenoids confining the quantized fluxes n 1 and n 2 within them. Using the Green function method, the vacuum expectation value of the system's energy which includes ''self interaction'' terms and a finite ''mutual interaction'' term is calculated. 8 refs
Tuning the Mass of Chameleon Fields in Casimir Force Experiments
Brax, Ph; Davis, A C; Shaw, D J; Iannuzzi, D
2010-01-01
We have calculated the chameleon pressure between two parallel plates in the presence of an intervening medium that affects the mass of the chameleon field. As intuitively expected, the gas in the gap weakens the chameleon interaction mechanism with a screening effect that increases with the plate separation and with the density of the intervening medium. This phenomenon might open up new directions in the search of chameleon particles with future long range Casimir force experiments.
Non-equilibrium Casimir force between vibrating plates.
Directory of Open Access Journals (Sweden)
Andreas Hanke
Full Text Available We study the fluctuation-induced, time-dependent force between two plates confining a correlated fluid which is driven out of equilibrium mechanically by harmonic vibrations of one of the plates. For a purely relaxational dynamics of the fluid we calculate the fluctuation-induced force generated by the vibrating plate on the plate at rest. The time-dependence of this force is characterized by a positive lag time with respect to the driving. We obtain two distinctive contributions to the force, one generated by diffusion of stress in the fluid and another related to resonant dissipation in the cavity. The relation to the dynamic Casimir effect of the electromagnetic field and possible experiments to measure the time-dependent Casimir force are discussed.
Energy Technology Data Exchange (ETDEWEB)
Ellingsen, Simen Andreas Aadnoey
2011-01-15
The present thesis focuses on several topics within three separate but related branches of the overall field of dispersion forces. The three branches are: temperature corrections to the Casimir force between real materials (Part 1), explicit calculation of Casimir energy in wedge geometries (Part 2), and Casimir-Polder forces on particles out of thermal equilibrium (Part 3). Part 1 deals primarily with analysis of a previously purported thermodynamic inconsistency in the Casimir-Lifshitz free energy of the interaction of two plane mirrors - violation of the third law of thermodynamics - when the latter's dielectric response is described with dissipative models. It is shown analytically and numerically that the Casimir entropy of the interaction between two metallic mirrors described by the Drude model does tend to zero at zero temperature, provided electronic relaxation does not vanish. The leading order terms at low temperature are found. A similar calculation is carried out for the interaction of semiconductors with small but non-zero DC conductivity. In a generalisation, it is shown that a violation of the third law can only occur for permittivities whose low-frequency behaviour is temperature dependent near zero temperature. A calculation using path integral methods shows that the low temperature behaviour of the interaction of fluctuating Foucault currents in two mirrors of Drude metal is identical to that of the full Casimir-Lifshitz free energy, reasserting a previous finding by Intravaia and Henkel that such fluctuating bulk currents are the physical reason for the anomalous entropy behaviour. In a related effort, an analysis of the frequency dependence of the Casimir force by Ford is generalised to imperfectly reflecting mirrors. A paradox is pointed out, in that the effects of a perturbation of the reflecting properties of the mirrors in a finite frequency window can be calculated in two ways giving different results. It is concluded that optimistic
Casimir force in noncommutative Randall-Sundrum models revisited
International Nuclear Information System (INIS)
Teo, L. P.
2010-01-01
We propose another method to compute the Casimir force in noncommutative Randall-Sundrum braneworld model considered by K. Nouicer and Y. Sabri, Phys. Rev. D 80, 086013 (2009). recently. Our method can be used to compute the Casimir force to any order in the noncommutative parameter. Contrary to the claim made by K. Nouicer and Y. Sabri that repulsive Casimir force can appear in the first order approximation, we show that the Casimir force is always attractive at any order of approximation.
Casimir-Foucault interaction: Free energy and entropy at low temperature
International Nuclear Information System (INIS)
Intravaia, Francesco; Ellingsen, Simen A.; Henkel, Carsten
2010-01-01
It was recently found that thermodynamic anomalies which arise in the Casimir effect between metals described by the Drude model can be attributed to the interaction of fluctuating Foucault (or eddy) currents [F. Intravaia and C. Henkel, Phys. Rev. Lett. 103, 130405 (2009).] We focus on the transverse electric (TE) polarization, where the anomalies occur, and show explicitly that the two leading terms of the low-temperature correction to the Casimir free energy of interaction between two plates are identical to those pertaining to the Foucault current interaction alone, up to a correction which is very small for good metals. Moreover, a mode density along real frequencies is introduced, showing that the TE contribution to the Casimir free energy, as given by the Lifshitz theory, separates in a natural manner into contributions from eddy currents and propagating cavity modes, respectively. The latter have long been known to be of little importance to the low-temperature Casimir anomalies. This convincingly demonstrates that eddy current modes are responsible for the large temperature correction to the Casimir effect between Drude metals, predicted by the Lifshitz theory, but not observed in experiments.
Casimir-Foucault interaction: Free energy and entropy at low temperature
Intravaia, Francesco; Ellingsen, Simen Å.; Henkel, Carsten
2010-09-01
It was recently found that thermodynamic anomalies which arise in the Casimir effect between metals described by the Drude model can be attributed to the interaction of fluctuating Foucault (or eddy) currents [F. Intravaia and C. Henkel, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.130405 103, 130405 (2009).] We focus on the transverse electric (TE) polarization, where the anomalies occur, and show explicitly that the two leading terms of the low-temperature correction to the Casimir free energy of interaction between two plates are identical to those pertaining to the Foucault current interaction alone, up to a correction which is very small for good metals. Moreover, a mode density along real frequencies is introduced, showing that the TE contribution to the Casimir free energy, as given by the Lifshitz theory, separates in a natural manner into contributions from eddy currents and propagating cavity modes, respectively. The latter have long been known to be of little importance to the low-temperature Casimir anomalies. This convincingly demonstrates that eddy current modes are responsible for the large temperature correction to the Casimir effect between Drude metals, predicted by the Lifshitz theory, but not observed in experiments.
Casimir force experiments with quartz tuning forks and an atomic force microscope (AFM)
International Nuclear Information System (INIS)
Ludwig, T
2008-01-01
The aim of the measurement series is to study the Casimir force, specifically the effects of different materials and geometries. The art of measuring sub-nano Newton forces has been engineered to a great extent in the material sciences, especially for the atomic force microscope. In today's scanning microscope technologies there are several common methods used to measure sub-nano Newton forces. While the commercial atomic force microscopes (AFM) mostly work with soft silicon cantilevers, there are a large number of reports from university groups on the use of quartz tuning forks to get high resolution AFM pictures, to measure shear forces or to create new force sensors. The quartz tuning fork based force sensor has a number of advantages over the silicon cantilever, but also has some disadvantages. In this report the method based on quartz tuning forks is described with respect to their usability for Casimir force measurements and compared with other successful techniques. Furthermore, a design for Casimir force measurements that was set up in Berlin will be described and practical experimental aspects will be discussed. A status report on the Casimir experiments in Berlin will be given, including the experimental setup. In order to study the details of the Casimir effect the apparatus and active surfaces have to be improved further. The surfaces have to be flatter and cleaner. For better resolution, cantilevers and tuning forks with a low spring constant have to be employed
Modelling critical Casimir force induced self-assembly experiments on patchy colloidal dumbbells.
Newton, Arthur C; Nguyen, T Anh; Veen, Sandra J; Kraft, Daniela J; Schall, Peter; Bolhuis, Peter G
2017-07-19
Colloidal particles suspended in a binary liquid mixture can interact via solvent mediated interactions, known as critical Casimir forces. For anisotropic colloids this interaction becomes directional, which leads to rich phase behavior. While experimental imaging and particle tracking techniques allow determination of isotropic effective potentials via Boltzmann inversion, the modeling of effective interaction in anisotropic systems is non-trivial precisely because of this directionality. Here we extract effective interaction potentials for non-spherical dumbbell particles from observed radial and angular distributions, by employing reference interaction site model (RISM) theory and direct Monte Carlo simulations. For colloidal dumbbell particles dispersed in a binary liquid mixture and interacting via induced critical Casimir forces, we determine the effective site-site potentials for a range of experimental temperatures. Using these potentials to simulate the system for strong Casimir forces, we reproduce the experimentally observed collapse, and provide a qualitative explanation for this behavior.
Detecting chameleons through Casimir force measurements
International Nuclear Information System (INIS)
Brax, Philippe; Bruck, Carsten van de; Davis, Anne-Christine; Shaw, Douglas; Mota, David F.
2007-01-01
The best laboratory constraints on strongly coupled chameleon fields come not from tests of gravity per se but from precision measurements of the Casimir force. The chameleonic force between two nearby bodies is more akin to a Casimir-like force than a gravitational one: The chameleon force behaves as an inverse power of the distance of separation between the surfaces of two bodies, just as the Casimir force does. Additionally, experimental tests of gravity often employ a thin metallic sheet to shield electrostatic forces; however, this sheet masks any detectable signal due to the presence of a strongly coupled chameleon field. As a result of this shielding, experiments that are designed to specifically test the behavior of gravity are often unable to place any constraint on chameleon fields with a strong coupling to matter. Casimir force measurements do not employ a physical electrostatic shield and as such are able to put tighter constraints on the properties of chameleons fields with a strong matter coupling than tests of gravity. Motivated by this, we perform a full investigation on the possibility of testing chameleon models with both present and future Casimir experiments. We find that present-day measurements are not able to detect the chameleon. However, future experiments have a strong possibility of detecting or rule out a whole class of chameleon models
Casimir energy density for spherical universes in n-dimensional spacetime
International Nuclear Information System (INIS)
Oezcan, Mustafa
2006-01-01
We consider the Casimir effect for the massless conformal scalar field in an n-dimensional, closed, static universe. We calculate the renormalized vacuum energy density using the covariant point-splitting method, the mode-sum regularization and the renormalized vacuum energy with the zeta-function regularization. We observe that all odd spacetime dimensions give us the zero renormalized vacuum energy density. For even spacetime dimensions the renormalized vacuum energy density oscillates in sign. The result agrees with three regularization techniques. The Casimir energy density for spherical universes in n-dimensional spacetime is regarded as interesting both to understand the correspondence between the sign of the effect and the dimension of manifold in topology and as a key to confirming the Casimir energy for half spherical universes (manifold with boundary) in n-dimensional spacetime
Casimir elements of epsilon Lie algebras
International Nuclear Information System (INIS)
Scheunert, M.
1982-10-01
The classical framework for investigating the Casimir elements of a Lie algebra is generalized to the case of an epsilon Lie algebra L. We construct the standard L-module isomorphism of the epsilon-symmetric algebra of L onto its enveloping algebra and we introduce the Harish-Chandra homomorphism. In case the generators of L can be written in a canonical two-index form, we construct the associated standard sequence of Casimir elements and derive a formula for their eigenvalues in an arbitrary highest weight module. (orig.)
Casimir free energy of dielectric films: classical limit, low-temperature behavior and control.
Klimchitskaya, G L; Mostepanenko, V M
2017-07-12
The Casimir free energy of dielectric films, both free-standing in vacuum and deposited on metallic or dielectric plates, is investigated. It is shown that the values of the free energy depend considerably on whether the calculation approach used neglects or takes into account the dc conductivity of film material. We demonstrate that there are material-dependent and universal classical limits in the former and latter cases, respectively. The analytic behavior of the Casimir free energy and entropy for a free-standing dielectric film at low temperature is found. According to our results, the Casimir entropy goes to zero when the temperature vanishes if the calculation approach with neglected dc conductivity of a film is employed. If the dc conductivity is taken into account, the Casimir entropy takes the positive value at zero temperature, depending on the parameters of a film, i.e. the Nernst heat theorem is violated. By considering the Casimir free energy of SiO 2 and Al 2 O 3 films deposited on a Au plate in the framework of two calculation approaches, we argue that physically correct values are obtained by disregarding the role of dc conductivity. A comparison with the well known results for the configuration of two parallel plates is made. Finally, we compute the Casimir free energy of SiO 2 , Al 2 O 3 and Ge films deposited on high-resistivity Si plates of different thicknesses and demonstrate that it can be positive, negative and equal to zero. The effect of illumination of a Si plate with laser light is considered. Possible applications of the obtained results to thin films used in microelectronics are discussed.
Casimir entropy for a ball in front of a plane
Bordag, M.; Pirozhenko, I. G.
2010-12-01
The violation of the third law of thermodynamics for metals described by the Drude model and for dielectrics with finite dc conductivity is one of the most interesting problems in the field of the Casimir effect. It manifests itself as a nonvanishing of the entropy for vanishing temperature. We review the relevant calculations for plane surfaces and calculate the corresponding contributions for a ball in front of a plane. In this geometry, these appear in much the same way as for parallel planes. We conclude that the violation of the 3rd law is not related to the infinite size of the planes.
Repulsive electromagnetic stresses in the Casimir piston
García, L.; González, L. E.; Lomnitz, M.; Villarreal, C.
2008-01-01
This manuscript has been withdrawn, since the authors have detected numerical inaccuracies that invalidate their main results concerning the existence of repulsive Casimir forces within a rectangular piston. Formulas presented in the manuscript keep still valid. The authors deeply apologize for this mistake.
Kinetic Roughening and Material Optical Properties Influence on Van der Waals/Casimir Forces
van Zwol, P. J.; Palasantzas, G.
Atomic force microscopy measurements and force theory calculations using the Lifshitz theory show that van der Waals/Casimir dispersive forces have a strong dependence on surface roughness and material optical properties. It is found that at separations below 100 nm the roughness effect is
Casimir force for a scalar field in warped brane worlds
International Nuclear Information System (INIS)
Linares, Roman; Morales-Tecotl, Hugo A.; Pedraza, Omar
2008-01-01
In looking for imprints of extra dimensions in braneworld models one usually builds these so that they are compatible with known low energy physics and thus focuses on high energy effects. Nevertheless, just as submillimeter Newton's law tests probe the mode structure of gravity other low energy tests might apply to matter. As a model example, in this work we determine the 4D Casimir force corresponding to a scalar field subject to Dirichlet boundary conditions on two parallel planes lying within the single brane of a Randall-Sundrum scenario extended by one compact extra dimension. Using the Green's function method such a force picks the contribution of each field mode as if it acted individually but with a weight given by the square of the mode wave functions on the brane. In the low energy regime one regains the standard 4D Casimir force that is associated to a zero mode in the massless case or to a quasilocalized or resonant mode in the massive one while the effect of the extra dimensions gets encoded as an additional term.
Selective decay by Casimir dissipation in inviscid fluids
International Nuclear Information System (INIS)
Gay-Balmaz, François; Holm, Darryl D
2013-01-01
The problem of parameterizing the interactions of larger scales and smaller scales in fluid flows is addressed by considering a property of two-dimensional (2D) incompressible turbulence. The property we consider is selective decay, in which a Casimir of the ideal formulation (enstrophy in 2D flows, helicity in three-dimensional flows) decays in time, while the energy stays essentially constant. This paper introduces a mechanism that produces selective decay by enforcing Casimir dissipation in fluid dynamics. This mechanism turns out to be related in certain cases to the numerical method of anticipated vorticity discussed in Sadourny and Basdevant (1981 C. R. Acad. Sci. Paris 292 1061–4, 1985 J. Atm. Sci. 42 1353–63). Several examples are given and a general theory of selective decay is developed that uses the Lie–Poisson structure of the ideal theory. A scale-selection operator allows the resulting modifications of the fluid motion equations to be interpreted in several examples as parametrizing the nonlinear, dynamical interactions between disparate scales. The type of modified fluid equation systems derived here may be useful in modelling turbulent geophysical flows where it is computationally prohibitive to rely on the slower, indirect effects of a realistic viscosity, such as in large-scale, coherent, oceanic flows interacting with much smaller eddies. (paper)
Casimir apparatuses in a weak gravitational field
DEFF Research Database (Denmark)
Bimonte, Giuseppe; Calloni, Enrico; Esposito, Giampiero
2009-01-01
We review and assess a part of the recent work on Casimir apparatuses in the weak gravitational field of the Earth. For a free, real massless scalar field subject to Dirichlet or Neumann boundary conditions on the parallel plates, the resulting regularized and renormalized energy-momentum tensor...... is covariantly conserved, while the trace anomaly vanishes if the massless field is conformally coupled to gravity. Conformal coupling also ensures a finite Casimir energy and finite values of the pressure upon parallel plates. These results have been extended to an electromagnetic field subject to perfect...... conductor (hence idealized) boundary conditions on parallel plates, by various authors. The regularized and renormalized energy-momentum tensor has beene valuated up to second order in the gravity acceleration. In both the scalar and the electromagnetic case, studied to first order in the gravity...
Casimir energy for a piecewise uniform string
International Nuclear Information System (INIS)
Brevik, I.; Nielsen, H.B.
1989-07-01
The Casimir energy for the transverse oscillations of a piecewise uniform closed string is calculated. The string consists of two parts I and II, endowed in general with different tensions and mass densities, although adjusted in such a way that the velocity of sound always equals the velocity of light. The dispersion equation is worked out under general conditions, and the frequency spectrum is determined in special cases. When the ratio L II /L I between the string lengths is an integer, it is in principle possible to determine the frequency spectrum through solving algebraic equations of increasingly high degree. The Casimir energy relative to the uniform string is in general found to be negative, although in the special case L I =L II the energy is equal to zero. Delicate points in the regularization procedure are discussed; they point toward an anomaly in the theory. (orig.)
Casimir pistons with general boundary conditions
Directory of Open Access Journals (Sweden)
Guglielmo Fucci
2015-02-01
Full Text Available In this work we analyze the Casimir energy and force for a scalar field endowed with general self-adjoint boundary conditions propagating in a higher dimensional piston configuration. The piston is constructed as a direct product I×N, with I=[0,L]⊂R and N a smooth, compact Riemannian manifold with or without boundary. The study of the Casimir energy and force for this configuration is performed by employing the spectral zeta function regularization technique. The obtained analytic results depend explicitly on the spectral zeta function associated with the manifold N and the parameters describing the general boundary conditions imposed. These results are then specialized to the case in which the manifold N is a d-dimensional sphere.
Casimir forces from a loop integral formulation
International Nuclear Information System (INIS)
Babington, James
2010-01-01
We reformulate the Casimir force between bodies in non-trivial background media. The force may be written in terms of loop variables, the loop being a curve around the scattering sites. A natural path ordering of exponentials takes place when a particular representation of the scattering centres is given. The basic object to be evaluated is a reduced (or abbreviated) classical pseudo-action that can be operator valued, and can be obtained from a classical path integral description.
On Casimir elements of simple Lie algebras
International Nuclear Information System (INIS)
El Houari, M.
1996-08-01
In this letter, we recall briefly the generalized Casimir elements of a finite dimensional Lie algebra. We specify those of orders two and three: when the Lie algebra is simple (even semisimple), we begin by normalizing the former (the quadratic), and then we study some actions of the latter (the cubic). In particular, we introduce a graphical formalism, translating rigorously the tensorial calculus. This allows us to prove the main theorem in a graphic theoretic manner. (author). 11 refs, 1 tab
Gross, Markus; Gambassi, Andrea; Dietrich, S
2017-08-01
The effect of imposing a constraint on a fluctuating scalar order parameter field in a system of finite volume is studied within statistical field theory. The canonical ensemble, corresponding to a fixed total integrated order parameter (e.g., the total number of particles), is obtained as a special case of the theory. A perturbative expansion is developed which allows one to systematically determine the constraint-induced finite-volume corrections to the free energy and to correlation functions. In particular, we focus on the Landau-Ginzburg model in a film geometry (i.e., in a rectangular parallelepiped with a small aspect ratio) with periodic, Dirichlet, or Neumann boundary conditions in the transverse direction and periodic boundary conditions in the remaining, lateral directions. Within the expansion in terms of ε=4-d, where d is the spatial dimension of the bulk, the finite-size contribution to the free energy of the confined system and the associated critical Casimir force are calculated to leading order in ε and are compared to the corresponding expressions for an unconstrained (grand canonical) system. The constraint restricts the fluctuations within the system and it accordingly modifies the residual finite-size free energy. The resulting critical Casimir force is shown to depend on whether it is defined by assuming a fixed transverse area or a fixed total volume. In the former case, the constraint is typically found to significantly enhance the attractive character of the force as compared to the grand canonical case. In contrast to the grand canonical Casimir force, which, for supercritical temperatures, vanishes in the limit of thick films, in the canonical case with fixed transverse area the critical Casimir force attains for thick films a negative value for all boundary conditions studied here. Typically, the dependence of the critical Casimir force both on the temperaturelike and on the fieldlike scaling variables is different in the two ensembles.
Symmetries and casimir of an extended classical long wave system
Indian Academy of Sciences (India)
We discuss the construction of a sequence of negative ranking symmetries through the property of uniformity in rank. More interestingly, we obtain the conserved quantities directly from the casimir of Poisson pencil. Keywords. Dispersionless equations; symmetries; casimir; conserved quantities. PACS Nos 02.30.Ik; 02.30.
Reply to 'Comment on 'Temperature dependence of the Casimir force for lossy bulk media''
Energy Technology Data Exchange (ETDEWEB)
Yampol' skii, V. A.; Maizelis, Z. A.; Apostolov, S. S. [Advanced Science Institute, RIKEN, Saitama, 351-0198 (Japan); A. Ya. Usikov Institute for Radiophysics and Electronics, NASU, 61085 Kharkov (Ukraine); Savel' ev, Sergey [Advanced Science Institute, RIKEN, Saitama, 351-0198 (Japan); Department of Physics, Loughborough University, Loughborough LE11 3TU (United Kingdom); Nori, Franco [Advanced Science Institute, RIKEN, Saitama, 351-0198 (Japan); Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)
2011-09-15
Here, we present an estimate of the characteristic wavelengths of the evanescent modes, which define the main contribution to the thermal part of the Casimir force. This estimate is more precise than the one in the preceding Comment by Bimonte et al.[Phys. Rev. A 84, 036501 (2011)]. The wavelengths we derive are indeed smaller than the sizes of the interacting bodies. We also discuss the results of several experiments on the thermal effects in the Casimir force.
Repulsive Casimir force at zero and finite temperature
International Nuclear Information System (INIS)
Lim, S C; Teo, L P
2009-01-01
We study the zero and finite temperature Casimir force acting on a perfectly conducting piston with arbitrary cross section moving inside a closed cylinder with infinitely permeable walls. We show that at any temperature, the Casimir force always tends to move the piston away from the walls and toward its equilibrium position. In the case of a rectangular piston, exact expressions for the Casimir force are derived. In the high-temperature regime, we show that the leading term of the Casimir force is linear in temperature and therefore the Casimir force has a classical limit. Due to duality, all these results also hold for an infinitely permeable piston moving inside a closed cylinder with perfectly conducting walls.
A microscopic approach to Casimir and Casimir-Polder forces between metallic bodies
Barcellona, Pablo; Passante, Roberto
2015-04-01
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 the overall two- and three-body contributions to the macroscopic Casimir-Polder and Casimir force, and to compare them with each other, for the two following geometries: metal nanoparticle/half-space and half-space/half-space, where all the materials are assumed perfect conductors. The above evaluation is obtained by summing up the contributions from the microscopic constituents of the bodies (metal nanoparticles). In the case of nanoparticle/half-space, our results fully agree with those that can be extracted from the corresponding macroscopic results, and explicitly show the non-applicability of the pairwise approximation for the geometry considered. In both cases, we find that, while the overall two-body contribution yields an attractive force, the overall three-body contribution is repulsive. Also, they turn out to be of the same order, consistently with the known non applicability of the pairwise approximation. The issue of the rapidity of convergence of the many-body expansion is also briefly discussed.
Zeta-function approach to Casimir energy with singular potentials
International Nuclear Information System (INIS)
Khusnutdinov, Nail R.
2006-01-01
In the framework of zeta-function approach the Casimir energy for three simple model system: single delta potential, step function potential and three delta potentials are analyzed. It is shown that the energy contains contributions which are peculiar to the potentials. It is suggested to renormalize the energy using the condition that the energy of infinitely separated potentials is zero which corresponds to subtraction all terms of asymptotic expansion of zeta-function. The energy obtained in this way obeys all physically reasonable conditions. It is finite in the Dirichlet limit, and it may be attractive or repulsive depending on the strength of potential. The effective action is calculated, and it is shown that the surface contribution appears. The renormalization of the effective action is discussed
Henkel, C.; Klimchitskaya, G. L.; Mostepanenko, V. M.
2018-03-01
We present a formalism based on first principles of quantum electrodynamics at nonzero temperature which permits us to calculate the Casimir-Polder interaction between an atom and a graphene sheet with arbitrary mass gap and chemical potential, including graphene-coated substrates. The free energy and force of the Casimir-Polder interaction are expressed via the polarization tensor of graphene in (2 +1 ) -dimensional space-time in the framework of the Dirac model. The obtained expressions are used to investigate the influence of the chemical potential of graphene on the Casimir-Polder interaction. Computations are performed for an atom of metastable helium interacting with either a freestanding graphene sheet or a graphene-coated substrate made of amorphous silica. It is shown that the impacts of the nonzero chemical potential and the mass gap on the Casimir-Polder interaction are in opposite directions, by increasing and decreasing the magnitudes of the free energy and force, respectively. It turns out, however, that the temperature-dependent part of the Casimir-Polder interaction is decreased by a nonzero chemical potential, whereas the mass gap increases it compared to the case of undoped, gapless graphene. The physical explanation for these effects is provided. Numerical computations of the Casimir-Polder interaction are performed at various temperatures and atom-graphene separations.
Sign and other aspects of semiclassical Casimir energies
International Nuclear Information System (INIS)
Schaden, Martin
2006-01-01
The Casimir energy of a massless scalar field is semiclassically given by contributions due to classical periodic rays. The required subtractions in the spectral density are determined explicitly. The semiclassical Casimir energies so defined coincide with those of zeta function regularization in the cases studied. Poles in the analytic continuation of zeta function regularization are related to nonuniversal subtractions in the spectral density. The sign of the Casimir energy of a scalar field on a smooth manifold is estimated by the sign of the contribution due to the shortest periodic rays only. Demanding continuity of the Casimir energy under small deformations of the manifold, the method is extended to integrable systems. The Casimir energy of a massless scalar field on a manifold with boundaries includes contributions due to periodic rays that lie entirely within the boundaries. These contributions in general depend on the boundary conditions. Although the Casimir energy due to a massless scalar field may be sensitive to the physical dimensions of manifolds with boundary. In favorable cases its sign can, contrary to conventional wisdom, be inferred without calculation of the Casimir energy
Repulsive Casimir and Casimir–Polder forces
International Nuclear Information System (INIS)
Milton, Kimball A; Abalo, E K; Parashar, Prachi; Pourtolami, Nima; Brevik, Iver; Ellingsen, Simen Å
2012-01-01
Casimir and Casimir–Polder repulsions have been known for more than 50 years. The general ‘Lifshitz’ configuration of parallel semi-infinite dielectric slabs permits repulsion if they are separated by a dielectric fluid that has a value of permittivity that is intermediate between those of the dielectric slabs. This was indirectly confirmed in the 1970s, and more directly by Capasso’s group recently. It has also been known for many years that electrically and magnetically polarizable bodies can experience a repulsive quantum vacuum force. More amenable to practical application are situations where repulsion could be achieved between ordinary conducting and dielectric bodies in vacuum. The status of the field of Casimir repulsion with emphasis on some recent developments will be surveyed. Here, stress will be placed on analytic developments, especially on Casimir–Polder (CP) interactions between anisotropically polarizable atoms, and CP interactions between anisotropic atoms and bodies that also exhibit anisotropy, either because of anisotropic constituents, or because of geometry. Repulsion occurs for wedge-shaped and cylindrical conductors, provided the geometry is sufficiently asymmetric, that is, either the wedge is sufficiently sharp or the atom is sufficiently far from the cylinder. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical in honour of Stuart Dowker’s 75th birthday devoted to ‘Applications of zeta functions and other spectral functions in mathematics and physics’. (review)
Casimir amplitudes in topological quantum phase transitions.
Griffith, M A; Continentino, M A
2018-01-01
Topological phase transitions constitute a new class of quantum critical phenomena. They cannot be described within the usual framework of the Landau theory since, in general, the different phases cannot be distinguished by an order parameter, neither can they be related to different symmetries. In most cases, however, one can identify a diverging length at these topological transitions. This allows us to describe them using a scaling approach and to introduce a set of critical exponents that characterize their universality class. Here we consider some relevant models of quantum topological transitions associated with well-defined critical exponents that are related by a quantum hyperscaling relation. We extend to these models a finite-size scaling approach based on techniques for calculating the Casimir force in electromagnetism. This procedure allows us to obtain universal Casimir amplitudes at their quantum critical points. Our results verify the validity of finite-size scaling in these systems and confirm the values of the critical exponents obtained previously.
Casimir amplitudes in topological quantum phase transitions
Griffith, M. A.; Continentino, M. A.
2018-01-01
Topological phase transitions constitute a new class of quantum critical phenomena. They cannot be described within the usual framework of the Landau theory since, in general, the different phases cannot be distinguished by an order parameter, neither can they be related to different symmetries. In most cases, however, one can identify a diverging length at these topological transitions. This allows us to describe them using a scaling approach and to introduce a set of critical exponents that characterize their universality class. Here we consider some relevant models of quantum topological transitions associated with well-defined critical exponents that are related by a quantum hyperscaling relation. We extend to these models a finite-size scaling approach based on techniques for calculating the Casimir force in electromagnetism. This procedure allows us to obtain universal Casimir amplitudes at their quantum critical points. Our results verify the validity of finite-size scaling in these systems and confirm the values of the critical exponents obtained previously.
Edge corrections to electromagnetic Casimir energies from general-purpose Mathieu-function routines
Blose, Elizabeth Noelle; Ghimire, Biswash; Graham, Noah; Stratton-Smith, Jeremy
2015-01-01
Scattering theory methods make it possible to calculate the Casimir energy of a perfectly conducting elliptic cylinder opposite a perfectly conducting plane in terms of Mathieu functions. In the limit of zero radius, the elliptic cylinder becomes a finite-width strip, which allows for the study of edge effects. However, existing packages for computing Mathieu functions are insufficient for this calculation because none can compute Mathieu functions of both the first and second kind for complex arguments. To address this shortcoming, we have written a general-purpose Mathieu-function package, based on algorithms developed by Alhargan. We use these routines to find edge corrections to the proximity force approximation for the Casimir energy of a perfectly conducting strip opposite a perfectly conducting plane.
Johnson-Nyquist noise and the Casimir force between real metals at nonzero temperature
International Nuclear Information System (INIS)
Bimonte, Giuseppe
2008-01-01
It has been well known for a long time that all lossy conductors at finite temperature display an electronic noise, the Johnson-Nyquist noise, arising from the thermal agitation of electric charges inside the conductor. The existence of this noise implies that two nearby discharged conductors at finite temperature should repel each other, as a result of the electrodynamic interaction between the Johnson-Nyquist currents in either conductor and the eddy currents they induce in the other. It is suggested that this force is at the origin of the recently discovered large repulsive correction to the thermal Casimir force between two lossy metallic plates. Further support for this physical picture is obtained by studying a simple system of two linear noisy antennas. Using elementary concepts from circuit theory, we show that the repulsive force engendered by the Johnson-Nyquist noise results in the same kind of thermodynamic inconsistencies found in the Casimir problem. We show that all inconsistencies are however resolved if account is taken of capacitive effects associated with the end points of the antennas. Our findings therefore suggest that capacitive effects resulting from the finite size of the plates may be essential for a resolution of the analogous problems met in the thermal Casimir effect
Johnson Nyquist noise and the Casimir force between real metals at nonzero temperature
Bimonte, Giuseppe
2008-04-01
It has been well known for a long time that all lossy conductors at finite temperature display an electronic noise, the Johnson-Nyquist noise, arising from the thermal agitation of electric charges inside the conductor. The existence of this noise implies that two nearby discharged conductors at finite temperature should repel each other, as a result of the electrodynamic interaction between the Johnson-Nyquist currents in either conductor and the eddy currents they induce in the other. It is suggested that this force is at the origin of the recently discovered large repulsive correction to the thermal Casimir force between two lossy metallic plates. Further support for this physical picture is obtained by studying a simple system of two linear noisy antennas. Using elementary concepts from circuit theory, we show that the repulsive force engendered by the Johnson-Nyquist noise results in the same kind of thermodynamic inconsistencies found in the Casimir problem. We show that all inconsistencies are however resolved if account is taken of capacitive effects associated with the end points of the antennas. Our findings therefore suggest that capacitive effects resulting from the finite size of the plates may be essential for a resolution of the analogous problems met in the thermal Casimir effect.
Casimir stress in materials: Hard divergency at soft walls
Griniasty, Itay; Leonhardt, Ulf
2017-11-01
The Casimir force between macroscopic bodies is well understood, but not the Casimir stress inside bodies. Suppose empty space or a uniform medium meets a soft wall where the refractive index is continuous but its derivative jumps. For this situation we predict a characteristic power law for the stress inside the soft wall and close to its edges. Our result shows that such edges are not tolerated in the aggregation of liquids at surfaces, regardless whether the liquid is attracted or repelled.
Towards a Casimir Force Measurement between Micromachined Parallel Plate Structures
Directory of Open Access Journals (Sweden)
Remco J. Wiegerink
2012-11-01
Full Text Available Ever since its prediction, experimental investigation of the Casimir force has been of great scientific interest. Many research groups have successfully attempted quantifying the force with different device geometries; however, measurement of the Casimir force between parallel plates with sub-micron separation distance is still a challenging task, since it becomes extremely difficult to maintain sufficient parallelism between the plates. The Casimir force can significantly influence the operation of micro devices and to realize reliable and reproducible devices it is necessary to understand and experimentally verify the influence of the Casimir force at sub-micron scale. In this paper, we present the design principle, fabrication and characterization of micromachined parallel plate structures that could allow the measurement of the Casimir force with tunable separation distance in the range of 100 to 1000 nm. Initially, a gold coated parallel plate structure is explored to measure the Casimir force, but also other material combinations could be investigated. Using gold-silicon eutectic bonding, a reliable approach to bond chips with integrated suspended plates together with a well-defined separation distance in the order of 1–2 μm is developed.
Casimir scaling and Yang-Mills glueballs
Hong, Deog Ki; Lee, Jong-Wan; Lucini, Biagio; Piai, Maurizio; Vadacchino, Davide
2017-12-01
We conjecture that in Yang-Mills theories the ratio between the ground-state glueball mass squared and the string tension is proportional to the ratio of the eigenvalues of quadratic Casimir operators in the adjoint and the fundamental representations. The proportionality constant depends on the dimension of the space-time only, and is henceforth universal. We argue that this universality, which is supported by available lattice results, is a direct consequence of area-law confinement. In order to explain this universal behavior, we provide three analytical arguments, based respectively on a Bethe-Salpeter analysis, on the saturation of the scale anomaly by the lightest scalar glueball and on QCD sum rules, commenting on the underlying assumptions that they entail and on their physical implications.
Casimir Energies for Isorefractive or Diaphanous Balls
Directory of Open Access Journals (Sweden)
Kimball A. Milton
2018-03-01
Full Text Available It is known that the Casimir self-energy of a homogeneous dielectric ball is divergent, although a finite self-energy can be extracted through second order in the deviation of the permittivity from the vacuum value. The exception occurs when the speed of light inside the spherical boundary is the same as that outside, so the self-energy of a perfectly conducting spherical shell is finite, as is the energy of a dielectric-diamagnetic sphere with ε μ = 1 , a so-called isorefractive or diaphanous ball. Here we re-examine that example and attempt to extend it to an electromagnetic δ -function sphere, where the electric and magnetic couplings are equal and opposite. Unfortunately, although the energy expression is superficially ultraviolet finite, additional divergences appear that render it difficult to extract a meaningful result in general, but some limited results are presented.
Casimir scaling, glueballs, and hybrid gluelumps
International Nuclear Information System (INIS)
Mathieu, V.; Semay, C.; Brau, F.
2006-01-01
Assuming that the Casimir scaling hypothesis is well verified in QCD, masses of glueballs and hybrid gluelumps (gluon attached to a point-like c anti c pair) are computed within the framework of the rotating string formalism. In our model, two gluons are attached by an adjoint string in a glueball, while the gluon and the colour octet c anti c pair are attached by two fundamental strings in a hybrid gluelump. Masses for such exotic hadrons are computed with very few free parameters. These predictions can serve as a guide for experimental searches. In particular, the ground-state glueballs lie on a Regge trajectory and the lightest 2 ++ state has a mass compatible with some experimental candidates. (orig.)
Repulsive Casimir force from fractional Neumann boundary conditions
International Nuclear Information System (INIS)
Lim, S.C.; Teo, L.P.
2009-01-01
This Letter studies the finite temperature Casimir force acting on a rectangular piston associated with a massless fractional Klein-Gordon field at finite temperature. Dirichlet boundary conditions are imposed on the walls of a d-dimensional rectangular cavity, and a fractional Neumann condition is imposed on the piston that moves freely inside the cavity. The fractional Neumann condition gives an interpolation between the Dirichlet and Neumann conditions, where the Casimir force is known to be always attractive and always repulsive respectively. For the fractional Neumann boundary condition, the attractive or repulsive nature of the Casimir force is governed by the fractional order which takes values from zero (Dirichlet) to one (Neumann). When the fractional order is larger than 1/2, the Casimir force is always repulsive. For some fractional orders that are less than but close to 1/2, it is shown that the Casimir force can be either attractive or repulsive depending on the aspect ratio of the cavity and the temperature.
Switching Colloidal Superstructures by Critical Casimir Forces.
Nguyen, Truc A; Newton, Arthur; Veen, Sandra J; Kraft, Daniela J; Bolhuis, Peter G; Schall, Peter
2017-09-01
Recent breakthroughs in colloidal synthesis promise the bottom-up assembly of superstructures on nano- and micrometer length scales, offering molecular analogues on the colloidal scale. However, a structural control similar to that in supramolecular chemistry remains very challenging. Here, colloidal superstructures are built and controlled using critical Casimir forces on patchy colloidal particles. These solvent-mediated forces offer direct analogues of molecular bonds, allowing patch-to-patch binding with exquisite temperature control of bond strength and stiffness. Particles with two patches are shown to form linear chains undergoing morphological changes with temperature, resembling a polymer collapse under poor-solvent conditions. This reversible temperature switching carries over to particles with higher valency, exhibiting a variety of patch-to-patch bonded structures. Using Monte Carlo simulations, it is shown that the collapse results from the growing interaction range favoring close-packed configurations. These results offer new opportunities for the active control of complex structures at the nano and micrometer scale, paving the way to novel temperature-switchable materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
The Casimir force for 2d sinusoidal gratings
Directory of Open Access Journals (Sweden)
Marachevsky Valery N.
2016-01-01
Full Text Available The Casimir free energy for 2d gratings separated by a vacuum slit is expressed in terms of Rayleigh coefficients, a novel general approach valid for arbitrary 2d surface profiles of gratings is outlined. The normal Casimir force in the system of two identical Si gratings with 2d sinusoidal surface profiles separated by a vacuum slit is computed for several amplitudes of surface profiles, distance dependence of the force is studied. A comparison with results for flat boundaries is performed.
The mathematics of the Casimir effect
International Nuclear Information System (INIS)
Dowling, J.P.
1987-02-01
We show how a famous problem in theoretical physics leads to two classical formulas which allow one to compute the difference between a definite integral and an infinite sum of the same functional form f. (author). 5 refs, 3 figs
Thermal corrections to the Casimir energy in a general weak gravitational field
Nazari, Borzoo
2016-12-01
We calculate finite temperature corrections to the energy of the Casimir effect of a two conducting parallel plates in a general weak gravitational field. After solving the Klein-Gordon equation inside the apparatus, mode frequencies inside the apparatus are obtained in terms of the parameters of the weak background. Using Matsubara’s approach to quantum statistical mechanics gravity-induced thermal corrections of the energy density are obtained. Well-known weak static and stationary gravitational fields are analyzed and it is found that in the low temperature limit the energy of the system increases compared to that in the zero temperature case.
Casimir densities for parallel plate in the domain wall background
International Nuclear Information System (INIS)
Setare, M R
2003-01-01
The Casimir forces on two parallel plates in the conformally flat domain wall background due to a conformally coupled massless scalar field satisfying mixed boundary conditions on the plates are investigated. In the general case of mixed boundary conditions, formulae are derived for the vacuum expectation values of the energy-momentum tensor and vacuum forces acting on the boundaries
Casimir-Lifshitz force out of thermal equilibrium
Antezza, M.; Pitaevskii, L.P.; Stringari, S.; Svetovoy, Vitaly
We study the Casimir-Lifshitz interaction out of thermal equilibrium, when the interacting objects are at different temperatures. The analysis is focused on the surface-surface, surface-rarefied body, and surface-atom configurations. A systematic investigation of the contributions to the force
Switching Casimir forces with phase-change materials
Torricelli, G.; van Zwol, P. J.; Shpak, O.; Binns, C.; Palasantzas, G.; Kooi, B. J.; Svetovoy, V. B.; Wuttig, M.
2010-01-01
We demonstrate here a controllable variation in the Casimir force. Changes in the force of up to 20% at separations of similar to 100 nm between Au and Ag-In-Sb-Te (AIST) surfaces were achieved on crystallization of an amorphous sample of AIST. This material is well known for its structural
Phillips, Nicholas G.; Hu, B. L.
2000-10-01
We present calculations of the variance of fluctuations and of the mean of the energy momentum tensor of a massless scalar field for the Minkowski and Casimir vacua as a function of an intrinsic scale defined by a smeared field or by point separation. We point out that, contrary to prior claims, the ratio of variance to mean-squared being of the order unity is not necessarily a good criterion for measuring the invalidity of semiclassical gravity. For the Casimir topology we obtain expressions for the variance to mean-squared ratio as a function of the intrinsic scale (defined by a smeared field) compared to the extrinsic scale (defined by the separation of the plates, or the periodicity of space). Our results make it possible to identify the spatial extent where negative energy density prevails which could be useful for studying quantum field effects in worm holes and baby universes, and for examining the design feasibility of real-life ``time machines.'' For the Minkowski vacuum we find that the ratio of the variance to the mean-squared, calculated from the coincidence limit, is identical to the value of the Casimir case at the same limit for spatial point separation while identical to the value of a hot flat space result with a temporal point separation. We analyze the origin of divergences in the fluctuations of the energy density and discuss choices in formulating a procedure for their removal, thus raising new questions about the uniqueness and even the very meaning of regularization of the energy momentum tensor for quantum fields in curved or even flat spacetimes when spacetime is viewed as having an extended structure.
Free vibration of geometrically nonlinear micro-switches under electrostatic and Casimir forces
International Nuclear Information System (INIS)
Jia, X L; Kitipornchai, S; Lim, C W; Yang, J
2010-01-01
This paper investigates the free vibration characteristics of micro-switches under combined electrostatic, intermolecular forces and axial residual stress, with an emphasis on the effect of geometric nonlinear deformation due to mid-plane stretching and the influence of Casimir force. The micro-switch considered in this study is made of either homogeneous material or non-homogeneous functionally graded material with two material phases. The Euler–Bernoulli beam theory with von Karman type nonlinear kinematics is applied in the theoretical formulation. The principle of virtual work is used to derive the nonlinear governing differential equation. The eigenvalue problem which describes free vibration of the micro-beam at its statically deflected state is then solved using the differential quadrature method. The natural frequencies and mode shapes of micro-switches for four different boundary conditions (i.e. clamped–clamped, clamped–simply supported, simply supported and clamped–free) are obtained. The solutions are validated through direct comparisons with experimental and other existing results reported in previous studies. A parametric study is conducted to show the significant effects of geometric nonlinearity, Casimir force, axial residual stress and material composition for the natural frequencies
Casimir scaling and YangâMills glueballs
Directory of Open Access Journals (Sweden)
Deog Ki Hong
2017-12-01
Full Text Available We conjecture that in YangâMills theories the ratio between the ground-state glueball mass squared and the string tension is proportional to the ratio of the eigenvalues of quadratic Casimir operators in the adjoint and the fundamental representations. The proportionality constant depends on the dimension of the space-time only, and is henceforth universal. We argue that this universality, which is supported by available lattice results, is a direct consequence of area-law confinement. In order to explain this universal behavior, we provide three analytical arguments, based respectively on a BetheâSalpeter analysis, on the saturation of the scale anomaly by the lightest scalar glueball and on QCD sum rules, commenting on the underlying assumptions that they entail and on their physical implications. Keywords: Glueballs, YangâMills theories, Confinement, Casimir scaling
Attractive electromagnetic Casimir stress on a spherical dielectric shell
International Nuclear Information System (INIS)
Graham, N.; Quandt, M.; Weigel, H.
2013-01-01
Based on calculations involving an idealized boundary condition, it has long been assumed that the stress on a spherical conducting shell is repulsive. We use the more realistic case of a Drude dielectric to show that the stress is attractive, matching the generic behavior of Casimir forces in electromagnetism. We trace the discrepancy between these two cases to interactions between the electromagnetic quantum fluctuations and the dielectric material
International Nuclear Information System (INIS)
Scheunert, M.
1982-10-01
The generators of the algebras under consideration can be written in a canonical two-index form and hence the associated standard seuqence of Casimir elements can be constructed. Following the classical approach by Perelomov and Popov, we obtain the eigenvalues of these Casimir elements in an arbitrary highest weight module by calculating the corresponding generating functions. (orig.)
A verification of quantum field theory – measurement of Casimir force
Indian Academy of Sciences (India)
Abstract. Here we review our work on measurement of the Casimir force between a large alu- minum coated a sphere and flat plate using an atomic force microscope. The average statistical pre- cision is 1% of the force measured at the closest separation. We have also shown nontrival boundary dependence of the Casimir ...
Towards measurement of the Casimir force between parallel plates separated at sub-mircon distance
Syed Nawazuddin, M.B.; Lammerink, Theodorus S.J.; Wiegerink, Remco J.; Berenschot, Johan W.; de Boer, Meint J.; Elwenspoek, Michael Curt
2011-01-01
Ever since its prediction, experimental investigation of the Casimir force has been of great scientific interest. Many research groups have successfully attempted quantifying the force with different device geometries; however measurement of the Casimir force between parallel plates with sub-micron
On the Casimir of the group ISL(n,R) and its algebraic decomposition
International Nuclear Information System (INIS)
Pecina-Cruz, J.N.
2005-01-01
In this paper, an explicit expression for the Casimir operator (or the Casimir invariant) of the inhomogeneous group ISL(n,R) in its enveloping algebra is proposed, which using contractions of the tensorial indices of the generating operators P ρ and E μ ν may be presented in the following [slightly more comprehensible as Eq. (1)] form. The Casimir is obtained by symmetrizing this expression. This tensor form is useful in the classification of particles in affine gravitational gauge theories; such as that based on ISL(4,R). It is also proven that the Casimir of ISL(n,R) can be decomposed in terms of the Casimirs of its little groups, a key point in the posterior construction of its irreducible representations
Casimir Forces and Quantum Friction from Ginzburg Radiation in Atomic Bose-Einstein Condensates.
Marino, Jamir; Recati, Alessio; Carusotto, Iacopo
2017-01-27
We theoretically propose an experimentally viable scheme to use an impurity atom in an atomic Bose-Einstein condensate, in order to realize condensed-matter analogs of quantum vacuum effects. In a suitable atomic level configuration, the collisional interaction between the impurity atom and the density fluctuations in the condensate can be tailored to closely reproduce the electric-dipole coupling of quantum electrodynamics. By virtue of this analogy, we recover and extend the paradigm of electromagnetic vacuum forces to the domain of cold atoms, showing in particular the emergence, at supersonic atomic speeds, of a novel power-law scaling of the Casimir force felt by the atomic impurity, as well as the occurrence of a quantum frictional force, accompanied by the Ginzburg emission of Bogoliubov quanta. Observable consequences of these quantum vacuum effects in realistic spectroscopic experiments are discussed.
Casimir energy of massless fermions in the Slab-bag
International Nuclear Information System (INIS)
Paola, R.D.M. de; Rodrigues, R.B.; Svaiter, N.F.
1999-04-01
The zero-point energy of a massless fermion field in the interior of two parallel plates in a D-dimensional space-time at zero temperature is calculated. In order to regularize the model, a mix between dimensional and zeta function regularization procedure is used and it is founded that the regularized zero-point energy density is finite for any number of space-time dimensions. We present a general expression for the Casimir energy for the fermionic field in such a situation. (author)
Lateral Casimir-Polder forces by breaking time-reversal symmetry
Oude Weernink, Ricardo R. Q. P. T.; Barcellona, Pablo; Buhmann, Stefan Yoshi
2018-03-01
We examine the lateral Casimir-Polder force acting on a circular rotating emitter near a dielectric plane surface. As the circular motion breaks time-reversal symmetry, the spontaneous emission in a direction parallel to the surface is in general anisotropic. We show that a lateral force arises which can be interpreted as a recoil force because of this asymmetric emission. The force is an oscillating function of the distance between the emitter and the surface, and the lossy character of the dielectric strongly influences the results in the near-field regime. The force exhibits also a population-induced dynamics, decaying exponentially with respect to time on time scales of the inverse of the spontaneous decay rate. We propose that this effect could be detected measuring the velocity acquired by the emitter, following different cycles of excitation and spontaneous decay. Our results are expressed in terms of the Green's tensor and can therefore easily be applied to more complex geometries.
International Nuclear Information System (INIS)
Seyedzahedi, A.; Moradian, A.; Setare, M.R.
2016-01-01
We investigate the Casimir force for a system composed of two thick slabs as substrates within three different homogeneous layers. We use the scattering approach along with the Matsubara formalism in order to calculate the Casimir force at finite temperature. First, we focus on constructing the reflection matrices and then we calculate the Casimir force for a water–lipid system. According to the conventional use of silicon as a substrate, we apply the formalism to calculate the Casimir force for layers of Au, VO 2 , mica, KCl and foam rubber on the thick slabs of silicon. Afterwards, introducing an increasing factor, we compare our results with Lifshitz force in the vacuum between two semispaces of silicon in order to illustrate the influence of the layers on intensifying the Casimir force. We also calculate the Casimir force between two slabs of the forementioned materials with finite thicknesses to indicate the substrate's role in increasing the obtained Casimir force. Our simple calculation is interesting since one can extend it along with the Rigorous Coupled Wave Analysis to systems containing inhomogeneous layers as good candidates for designing nanomechanical devices.
Energy Technology Data Exchange (ETDEWEB)
Seyedzahedi, A. [Department of Science, University of Kurdistan, Sanandaj (Iran, Islamic Republic of); Moradian, A., E-mail: a.moradian@uok.ac.ir [Department of Science, Campus of Bijar, University of Kurdistan, Bijar (Iran, Islamic Republic of); Setare, M.R., E-mail: rezakord@ipm.ir [Department of Science, University of Kurdistan, Sanandaj (Iran, Islamic Republic of)
2016-04-01
We investigate the Casimir force for a system composed of two thick slabs as substrates within three different homogeneous layers. We use the scattering approach along with the Matsubara formalism in order to calculate the Casimir force at finite temperature. First, we focus on constructing the reflection matrices and then we calculate the Casimir force for a water–lipid system. According to the conventional use of silicon as a substrate, we apply the formalism to calculate the Casimir force for layers of Au, VO{sub 2}, mica, KCl and foam rubber on the thick slabs of silicon. Afterwards, introducing an increasing factor, we compare our results with Lifshitz force in the vacuum between two semispaces of silicon in order to illustrate the influence of the layers on intensifying the Casimir force. We also calculate the Casimir force between two slabs of the forementioned materials with finite thicknesses to indicate the substrate's role in increasing the obtained Casimir force. Our simple calculation is interesting since one can extend it along with the Rigorous Coupled Wave Analysis to systems containing inhomogeneous layers as good candidates for designing nanomechanical devices.
Modulation of the Casimir force by laser pulses: Influence of oxide films on the silicon surface
Klimchitskaya, G. L.; Bukina, M. N.; Churkin, Yu. V.; Yurova, V. A.
2010-10-01
The possibility of modulating the Casimir force that acts in an air medium between a gold sphere and a silicon plate irradiated by laser pulses has been studied. It has been demonstrated that the oxide film that is formed on the silicon surface in air hardly affects the possibility of modulating the Casimir force when the distances between interacting bodies are of the order of 100 nm. With an increase in the distance, the modulation depth decreases; however, this region is of less practical interest, because the Casimir forces become too weak.
Rectification of a Casimir Nanomachine with a Triangular Wave Signal
Directory of Open Access Journals (Sweden)
ali moradian
2017-11-01
Full Text Available In this paper, we investigate the Casimir nano system composed of two quadrisected dielectric disks separated by a thin gap. Initially the two disks have the same surface dielectric distributions. We use scatting approach in the weak coupling limit and show that the top plate experiences a torque if it rotates about its axes by an angle. Consequently, we will be able to calculate. Quite interesting, such a nanomachine may be used to examine the dielectric dependence of the Casimir torque. Our small system can be used to measure small torques. We assume that the top disk is mounted on an axle and part of the rotational friction in the system comes from the axial friction and an external load is mounted on it. For such a system with specified parameters, we can estimate inertia and axial friction. Therefor we can neglect the inertia term and use the over damped regime to describe the dynamics of our system. We show that our small system can rectify a periodic square-wave angular velocity and we obtain the average angular velocity of the top plate.
Energy Technology Data Exchange (ETDEWEB)
Mohideen, Umar [Univ. of California, Riverside, CA (United States)
2015-04-14
Duration of award was from 4/15/10-4/14/15. In this grant period our contributions to the field of VdW/Casimir forces are 24 refereed publications in journals such as Physical Review Letters (4) [1-4], Physical Review B (10) [5-14], Physical Review D (2) [15,16], Applied Physics Letters (1) [17], Review of Scientific Instruments (1) [18] and the International Journal of Modern Physics A (5) [19-23] and B(1) (invited review article [24]). We presented 2 plenary conference talks, 3 lectures at the Pan American School on Frontiers in Casimir Physics, 2 conferences, 1 colloquium and 11 APS talks. If publications are restricted to only those with direct connection to the aims proposed in the prior grant period, then it will be a total of 12: Physical Review Letters (3) [2-4], Physical Review B (6) [6-8,12,13,25], Review of Scientific Instruments (1) [18], International Journal of Modern Physics A (1) [19] and B(1) [169]. A brief aggregated description of the directly connected accomplishments is below. The following topics are detailed: dispersion force measurements with graphene, dispersion force from ferromagnetic metals, conclusion on role of electrostatic patches, UV radiation induced modification of the Casimir force, low temperature measurement of the Casimir force, and Casimir force from thin fluctuating membranes.
Casimir force in the Goedel space-time and its possible induced cosmological inhomogeneity
Energy Technology Data Exchange (ETDEWEB)
Khodabakhshi, Sh. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Shojai, A. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), Foundations of Physics Group, School of Physics, Tehran (Iran, Islamic Republic of)
2017-07-15
The Casimir force between two parallel plates in the Goedel universe is computed for a scalar field at finite temperature. It is observed that when the plates' separation is comparable with the scale given by the rotation of the space-time, the force becomes repulsive and then approaches zero. Since it has been shown previously that the universe may experience a Goedel phase for a small period of time, the induced inhomogeneities from the Casimir force are also studied. (orig.)
Okamoto, Ryuichi; Onuki, Akira
2012-03-21
We investigate the critical behavior of a near-critical fluid confined between two parallel plates in contact with a reservoir by calculating the order parameter profile and the Casimir amplitudes (for the force density and for the grand potential). Our results are applicable to one-component fluids and binary mixtures. We assume that the walls absorb one of the fluid components selectively for binary mixtures. We propose a renormalized local functional theory accounting for the fluctuation effects. Analysis is performed in the plane of the temperature T and the order parameter in the reservoir ψ(∞). Our theory is universal if the physical quantities are scaled appropriately. If the component favored by the walls is slightly poor in the reservoir, there appears a line of first-order phase transition of capillary condensation outside the bulk coexistence curve. The excess adsorption changes discontinuously between condensed and noncondensed states at the transition. With increasing T, the transition line ends at a capillary critical point T=T(c) (ca) slightly lower than the bulk critical temperature T(c) for the upper critical solution temperature. The Casimir amplitudes are larger than their critical point values by 10-100 times at off-critical compositions near the capillary condensation line. © 2012 American Institute of Physics
The Casimir interaction of a massive vector field between concentric spherical bodies
International Nuclear Information System (INIS)
Teo, L.P.
2011-01-01
The Casimir interaction energy due to the vacuum fluctuations of a massive vector field between two perfectly conducting concentric spherical bodies is computed. The TE contribution to the Casimir interaction energy is a direct generalization of the massless case but the TM contribution is much more complicated. Each TM mode is a linear combination of a transverse mode which is the generalization of a TM mode in the massless case and a longitudinal mode that does not appear in the massless case. In contrast to the case of two parallel perfectly conducting plates, there are no TM discrete modes that vanish identically in the perfectly conducting spherical bodies. Numerical simulations show that the Casimir interaction force between the two bodies is always attractive.
On the Casimir scaling violation in the cusp anomalous dimension at small angle
Grozin, Andrey; Henn, Johannes; Stahlhofen, Maximilian
2017-10-01
We compute the four-loop n f contribution proportional to the quartic Casimir of the QCD cusp anomalous dimension as an expansion for small cusp angle ϕ. This piece is gauge invariant, violates Casimir scaling, and first appears at four loops. It requires the evaluation of genuine non-planar four-loop Feynman integrals. We present results up to O({φ}^4) . One motivation for our calculation is to probe a recent conjecture on the all-order structure of the cusp anomalous dimension. As a byproduct we obtain the four-loop HQET wave function anomalous dimension for this color structure.
Casimir force in the Gödel space-time and its possible induced cosmological inhomogeneity
Khodabakhshi, Sh.; Shojai, A.
2017-07-01
The Casimir force between two parallel plates in the Gödel universe is computed for a scalar field at finite temperature. It is observed that when the plates' separation is comparable with the scale given by the rotation of the space-time, the force becomes repulsive and then approaches zero. Since it has been shown previously that the universe may experience a Gödel phase for a small period of time, the induced inhomogeneities from the Casimir force are also studied.
Energy Technology Data Exchange (ETDEWEB)
Klimchitskaya, G.L. [Central Astronomical Observatory at Pulkovo of the Russian Academy of Sciences, Saint Petersburg (Russian Federation); Peter the Great Saint Petersburg Polytechnic University, Institute of Physics, Nanotechnology and Telecommunications, Saint Petersburg (Russian Federation)
2017-05-15
The strongest constraints on the Yukawa-type corrections to Newton's gravitational law and on the coupling constants of axion-like particles to nucleons, following from recently performed experiments of Casimir physics, are presented. Specifically, the constraints obtained from measurements of the lateral and normal Casimir forces between sinusoidally corrugated surfaces, and from the isoelectronic experiment are considered, and the ranges of their greatest strength are refined. Minor modifications in the experimental setups are proposed which allow for strengthening the resultant constraints up to an order of magnitude. The comparison with some weaker constraints derived in the Casimir regime is also made. (orig.)
Uma introdução aos métodos de cálculo da energia de Casimir
Directory of Open Access Journals (Sweden)
Passos Sobrinho J.J.
2001-01-01
Full Text Available O efeito Casimir é um dos aspectos mais intrigantes da física moderna. A previsão da existência de uma força macroscópica de origem quântica entre condutores neutros e sua posterior comprovação experimental é sem dúvida um dos triunfos da teoria quântica dos campos. Complementando uma introdução conceitual publicada recentemente nesta revista, apresentamos alguns métodos de cálculo da energia de Casimir, que é a grandeza fundamental que origina o efeito Casimir.
Optical properties and kinetic roughening influence on dispersive casimir and van der Waals forces
Palasantzas, G.; Svetovoy, Vitaly; van Zwol, P.J.
2010-01-01
Casimir and van der Waals dispersive forces between real material surfaces can be strongly influenced by surface roughness and the frequency dependent dielectric functions of the interacting materials. The Lifshitz theory allows calculations of these forces between two flat plates if the frequency
Optical Properties and Kinetic Roughening Influence on Dispersive Casimir and van der Waals Forces
Palasantzas, G.; Svetovoy, V. B.; Van Zwol, P. J.
2010-01-01
Casimir and van der Waals dispersive forces between real material surfaces can be strongly influenced by surface roughness and the frequency dependent dielectric functions of the interacting materials. The Lifshitz theory allows calculations of these forces between two flat plates if the frequency
Casimir-lifshitz force out of thermal equilibrium and asymptotic nonadditivity
Antezza, Mauro; Pitaevskii, Lev P.; Stringari, Sandro; Svetovoy, Vitaly
2006-01-01
We investigate the force acting between two parallel plates held at different temperatures. The force reproduces, as limiting cases, the well-known Casimir-Lifshitz surface-surface force at thermal equilibrium and the surface-atom force out of thermal equilibrium recently derived by M. Antezza et
Tailoring optical metamaterials to tune the atom-surface Casimir-Polder interaction.
Chan, Eng Aik; Aljunid, Syed Abdullah; Adamo, Giorgio; Laliotis, Athanasios; Ducloy, Martial; Wilkowski, David
2018-02-01
Metamaterials are fascinating tools that can structure not only surface plasmons and electromagnetic waves but also electromagnetic vacuum fluctuations. The possibility of shaping the quantum vacuum is a powerful concept that ultimately allows engineering the interaction between macroscopic surfaces and quantum emitters such as atoms, molecules, or quantum dots. The long-range atom-surface interaction, known as Casimir-Polder interaction, is of fundamental importance in quantum electrodynamics but also attracts a significant interest for platforms that interface atoms with nanophotonic devices. We perform a spectroscopic selective reflection measurement of the Casimir-Polder interaction between a Cs(6P 3/2 ) atom and a nanostructured metallic planar metamaterial. We show that by engineering the near-field plasmonic resonances of the metamaterial, we can successfully tune the Casimir-Polder interaction, demonstrating both a strong enhancement and reduction with respect to its nonresonant value. We also show an enhancement of the atomic spontaneous emission rate due to its coupling with the evanescent modes of the nanostructure. Probing excited-state atoms next to nontrivial tailored surfaces is a rigorous test of quantum electrodynamics. Engineering Casimir-Polder interactions represents a significant step toward atom trapping in the extreme near field, possibly without the use of external fields.
Klimchitskaya, G. L.; Mostepanenko, V. M.
2017-06-01
We derive constraints on the coupling constants of axionlike particles to nucleons and on the Yukawa-type corrections to Newton's gravitational law from the results of recent experiment on measuring the difference of Casimir forces between a Ni-coated sphere and Au and Ni sectors of a structured disc. Over the wide range of axion masses from 2.61 meV to 0.9 eV the obtained constraints on the axion-to-nucleon coupling are up to a factor of 14.6 stronger than all previously known constraints following from experiments on measuring the Casimir interaction. The constraints on non-Newtonian gravity found here are also stronger than all that following from the Casimir- and Cavendish-type experiments over the interaction range from 30 nm to 5.4 μ m . They are up to a factor of 177 stronger than the constraints derived recently from measuring the difference of lateral forces. Our constraints confirm previous somewhat stronger limits obtained from the isoelectronic experiment, where the contribution of the Casimir force was nullified.
Generalized Riemann zeta-function regularization and Casimir energy for a piecewise uniform string
International Nuclear Information System (INIS)
Li Xinzhou; Shi Xin; Zhang Jianzu.
1990-12-01
The generalized zeta-function techniques will be utilized to investigate the Casimir energy for the transverse oscillations of a piecewise uniform closed string. We find that zeta-function regularization method can lead straightforwardly to a correct result. (author). 6 refs
The casimir free energy in high- and low-temperature limits
Svetovoy, Vitaly; Esquivel, R.
2006-01-01
The problem with the temperature dependence of the Casimir force is investigated. We analyse high-temperature limit analytically making calculations at real frequencies. The purpose is to answer the questionwhy there is no continuous transition between real and ideal metals and why the result does
Chaotic behavior in Casimir oscillators: A case study for phase-change materials.
Tajik, Fatemeh; Sedighi, Mehdi; Khorrami, Mohammad; Masoudi, Amir Ali; Palasantzas, George
2017-10-01
Casimir forces between material surfaces at close proximity of less than 200 nm can lead to increased chaotic behavior of actuating devices depending on the strength of the Casimir interaction. We investigate these phenomena for phase-change materials in torsional oscillators, where the amorphous to crystalline phase transitions lead to transitions between high and low Casimir force and torque states, respectively, without material compositions. For a conservative system bifurcation curve and Poincare maps analysis show the absence of chaotic behavior but with the crystalline phase (high force-torque state) favoring more unstable behavior and stiction. However, for a nonconservative system chaotic behavior can take place introducing significant risk for stiction, which is again more pronounced for the crystalline phase. The latter illustrates the more general scenario that stronger Casimir forces and torques increase the possibility for chaotic behavior. The latter is making it impossible to predict whether stiction or stable actuation will occur on a long-term basis, and it is setting limitations in the design of micronano devices operating at short-range nanoscale separations.
The trace identity and the planar Casimir effect
Indian Academy of Sciences (India)
Abstract. The familiar trace identity associated with the scale transformation xµ → x µ = e−λxµ on the Lagrangian density for a noninteracting massive real scalar field in 2 + 1 dimensions is shown to be violated on a single plate on which the Dirichlet boundary condition φ(t, x1, x2 = −a) = 0 is imposed. It is however respected ...
The trace identity and the planar Casimir effect
Indian Academy of Sciences (India)
The familiar trace identity associated with the scale transformation → ′ = - on the Lagrangian density for a noninteracting massive real scalar field in 2 + 1 dimensions is shown to be violated on a single plate on which the Dirichlet boundary condition (, 1, 2 = -) = 0 is imposed. It is however respected ...
Casimir effect for closed cavities with conducting and permeable walls
International Nuclear Information System (INIS)
Ferreira, L.A.; Zimerman, A.H.; Ruggiero, J.R.
1980-01-01
The quantum electromagnetic zero point energy is calculated for rectangular cavities where some of the walls are perfect conductors and the others are made of infinitely permeable materials. It is found that for cubic systems, for some configurations the zero point electromagnetic energy is positive, while in other configurations this zero point energy is negative. The consequences of these results on possible models for the electron are discussed. (Author) [pt
The trace identity and the planar Casimir effect
Indian Academy of Sciences (India)
S G Kamath the derivative operators in (24) acting on ∆(x−y), the latter being now defined by. (18a) but with the δ-function appropriate to three space–time dimensions. Rewrit- ing (24) as exp iZ[J(x),Kµ,Dαβ,Lµν]. = 1. W0. ∞. ∑. 0. (−i)n n! {∫. d3yDµν(y)Gµν. }n. × exp −. {. 1. 2 i. ∫. d3xd3yM(x)∆(x − y)M(y). } (25) with. Gµν = 3.
From optical lattice clocks to the measurement of forces in the Casimir regime
International Nuclear Information System (INIS)
Wolf, Peter; Lemonde, Pierre; Bize, Sebastien; Landragin, Arnaud; Clairon, Andre; Lambrecht, Astrid
2007-01-01
We describe an experiment based on atoms trapped close to a macroscopic surface, to study the interactions between the atoms and the surface at very small separations (0.6-10 μm). In this range the dominant potential is the QED interaction (Casimir-Polder and van der Waals) between the surface and the atom. Additionally, several theoretical models suggest the possibility of Yukawa-type potentials with sub-millimeter range, arising from new physics related to gravity. The proposed setup is very similar to neutral atom optical lattice clocks, but with the atoms trapped in lattice sites close to the reflecting mirror. A sequence of pulses of the probe laser at different frequencies is then used to create an interferometer with a coherent superposition between atomic states at different distances from the mirror (in different lattice sites). Assuming atom interferometry state-of-the-art measurement of the phase difference and a duration of the superposition of about 0.1 s, we expect to be able to measure the potential difference between separated states with an uncertainty of ≅10 -4 Hz. An analysis of systematic effects for different atoms and surfaces indicates no fundamentally limiting effect at the same level of uncertainty, but does influence the choice of atom and surface material. Based on those estimates, we expect that such an experiment would improve the best existing measurements of the atom-wall QED interaction by ≥ 2 orders of magnitude, while gaining up to four orders of magnitude on the best present limits on new interactions in the range between 100 nm and 100 μm
Thermal Casimir-Polder forces on a V-type three-level atom
Xu, Chen-Ran; Xu, Jing-Ping; Al-amri, M.; Zhu, Cheng-Jie; Xie, Shuang-Yuan; Yang, Ya-Ping
2017-09-01
We study the thermal Casimir-Polder (CP) forces on a V-type three-level atom. The competition between the thermal effect and the quantum interference of the two transition dipoles on the force is investigated. To shed light onto the role of the quantum interference, we analyze two kinds of initial states of the atom, i.e., the superradiant state and the subradiant state. Considering the atom being in the thermal reservoir, the resonant CP force arising from the real photon emission dominates in the evolution of the CP force. Under the zero-temperature condition, the quantum interference can effectively modify the amplitude and the evolution of the force, leading to a long-time force or even the cancellation of the force. Our results reveal that in the finite-temperature case, the thermal photons can enhance the amplitude of all force elements, but have no influence on the net resonant CP force in the steady state, which means that the second law of thermodynamics still works. For the ideal degenerate V-type atom with parallel dipoles under the initial subradiant state, the robust destructive quantum interference overrides the thermal fluctuations, leading to the trapping of the atom in the subradiant state and the disappearance of the CP force. However, in terms of a realistic Zeeman atom, the thermal photons play a significant role during the evolution of the CP force. The thermal fluctuations can enhance the amplitude of the initial CP force by increasing the temperature, and weaken the influence of the quantum interference on the evolution of the CP force from the initial superradiant (subradiant) state to the steady state.
International Nuclear Information System (INIS)
Macfarlane, A J; Pfeiffer, Hendryk
2003-01-01
The uniformity, for the family of exceptional Lie algebras g, of the decompositions of the powers of their adjoint representations is now well known for powers up to four. The paper describes an extension of this uniformity for the totally antisymmetrized nth powers up to n = 9, identifying families of representations with integer eigenvalues 5, ..., 9 for the quadratic Casimir operator, in each case providing a formula for the dimensions of the representations in the family as a function of D = dim g. This generalizes previous results for powers j and Casimir eigenvalues j, j ≤ 4. Many intriguing, perhaps puzzling, features of the dimension formulae are discussed and the possibility that they may be valid for a wider class of not necessarily simple Lie algebras is considered
Stability Analysis of a Rigid Body with a Flexible Attachment Using the Energy-Casimir Method
Posbergh, T. A.; Krishnaprasad, Perinkulam S.; Marsden, Jerrold E.
1987-01-01
We consider a system consisting of a rigid body to which a linear extensible shear beam is attached. For such a system the Energy-Casimir method can be used to investigate the stability of the equilibria. In the case we consider, it can be shown that a test for (formal) stability reduces to checking the positive definiteness of two matrices which depend on the parameters of the system and the particular equilibrium about which the stability is to be ascertained.
Energy loss mechanism for suspended micro- and nanoresonators due to the Casimir force
Gusso, André
2011-01-01
A so far not considered energy loss mechanism in suspended micro- and nanoresonators due to noncontact acoustical energy loss is investigated theoretically. The mechanism consists on the conversion of the mechanical energy from the vibratory motion of the resonator into acoustic waves on large nearby structures, such as the substrate, due to the coupling between the resonator and those structures resulting from the Casimir force acting over the separation gaps. Analytical expressions for the ...
Guérout, R.; Lambrecht, A.; Milton, K. A.; Reynaud, S.
2014-10-01
We carefully reexamine the conditions of validity for the consistent derivation of the Lifshitz-Matsubara sum formula for the Casimir pressure between metallic plane mirrors. We recover the usual expression for the lossy Drude model but not for the lossless plasma model. We give an interpretation of this new result in terms of the modes associated with the Foucault currents, which play a role in the limit of vanishing losses, in contrast to common expectations.
Casimir friction and near-field radiative heat transfer in graphene structures
International Nuclear Information System (INIS)
Volokitin, A.I.; Samara State Technical Univ.
2017-01-01
The dependence of the Casimir friction force between a graphene sheet and a (amorphous) SiO 2 substrate on the drift velocity of the electrons in the graphene sheet is studied. It is shown that the Casimir friction is strongly enhanced for the drift velocity above the threshold velocity when the friction is determined by the resonant excitation of the surface phonon-polaritons in the SiO 2 substrate and the electron-hole pairs in graphene. The theory agrees well with the experimental data for the current-voltage dependence for unsuspended graphene on the SiO 2 substrate. The theories of the Casimir friction and the near-field radiative energy transfer are used to study the heat generation and dissipation in graphene due to the interaction with phonon-polaritons in the (amorphous) SiO 2 substrate and acoustic phonons in graphene. For suspended graphene, the energy transfer coefficient at nanoscale gap is ∝ three orders of magnitude larger than the radiative heat transfer coefficient of the blackbody radiation limit.
Casimir energy of a scalar field with a space-dependent mass distribution
International Nuclear Information System (INIS)
Aoyama, H.
1984-01-01
The Casimir energy is evaluated for a free scalar field that has a mass term m 2 (x 1 ), depending on one space coordinate x 1 . The formalism for evaluating the Casimir energy is developed for the case of m 2 (x 1 ) finite everywhere in d-dimensional space-time. The case with m 2 (x 1 )=m 0 2 theta((1/2)L-vertical strokex 1 vertical stroke)+msub(infinite) 2 theta(vertical strokex 1 vertical stroke(-1/2)L) is explicitly evaluated for any value of m 0 and msub(infinite) without any approximation. The result consists of volume energy terms, a surface term, and a non-leading term. Most of the UV divergences are in the volume energy terms and renormalize the coupling constants of the underlying theory. The surface energy term is finite for d =5 due to the boundaries being sharp. A closed finite expression is obtained for the non-leading term. Our results are shown to reproduce the known Casimir energies for the limiting cases, m 0 ->infinite and msub(infinite)->infinite. (orig.)
Rodrigues, Janderson R; Gusso, Andre; Rosa, Felipe S S; Almeida, Vilson R
2018-02-22
Nano-optomechanical devices have enabled a lot of interesting scientific and technological applications. However, due to their nanoscale dimensions, they are vulnerable to the action of Casimir and van der Waals (dispersion) forces. This work presents a rigorous analysis of the dispersion forces on a nano-optomechanical device based on a silicon waveguide and a silicon dioxide substrate, surrounded by air and driven by optical forces. The dispersion forces are calculated using a modified Lifshitz theory with experimental optical data and validated by means of a rigorous 3D FDTD simulation. The mechanical nonlinearity of the nanowaveguide is taken into account and validated using a 3D FEM simulation. The results show that it is possible to attain a no pull-in critical point due to only the optical forces; however, the dispersion forces usually impose a pull-in critical point to the device and establish a minimal initial gap between the waveguide and the substrate. Furthermore, it is shown that the geometric nonlinearity effect may be exploited in order to avoid or minimize the pull-in and, therefore, the device collapse.
International Nuclear Information System (INIS)
Xiong, Jie L.; Tong, M.S.; Atkins, Phillip; Chew, W.C.
2010-01-01
In this Letter, we generalized the surface integral equation method for the evaluation of Casimir force in arbitrary three-dimensional geometries. Similar to the two-dimensional case, the evaluation of the mean Maxwell stress tensor is cast into solving a series of three-dimensional scattering problems. The formulation and solution of the three-dimensional scattering problems are well-studied in classical computational electromagnetics. This Letter demonstrates that this quantum electrodynamic phenomenon can be studied using the knowledge and techniques of classical electrodynamics.
Lifshitz-Matsubara sum formula for the Casimir pressure between magnetic metallic mirrors
Guérout, R.; Lambrecht, A.; Milton, K. A.; Reynaud, S.
2016-02-01
We examine the conditions of validity for the Lifshitz-Matsubara sum formula for the Casimir pressure between magnetic metallic plane mirrors. As in the previously studied case of nonmagnetic materials [Guérout et al., Phys. Rev. E 90, 042125 (2014), 10.1103/PhysRevE.90.042125], we recover the usual expression for the lossy model of optical response, but not for the lossless plasma model. We also show that the modes associated with the Foucault currents play a crucial role in the limit of vanishing losses, in contrast to expectations.
Calculation of nonzero-temperature Casimir forces in the time domain
International Nuclear Information System (INIS)
Pan, Kai; Reid, M. T. Homer; McCauley, Alexander P.; Rodriguez, Alejandro W.; White, Jacob K.; Johnson, Steven G.
2011-01-01
We show how to compute Casimir forces at nonzero temperatures with time-domain electromagnetic simulations, for example, using a finite-difference time-domain (FDTD) method. Compared to our previous zero-temperature time-domain method, only a small modification is required, but we explain that some care is required to properly capture the zero-frequency contribution. We validate the method against analytical and numerical frequency-domain calculations, and show a surprising high-temperature disappearance of a nonmonotonic behavior previously demonstrated in a pistonlike geometry.
Casimir problem of spherical dielectrics: quantum statistical and field theoretical approaches.
Høye, J S; Brevik, I; Aarseth, J B
2001-05-01
The Casimir free energy for a system of two dielectric concentric nonmagnetic spherical bodies is calculated with use of a quantum statistical mechanical method, at arbitrary temperature. By means of this rather novel method, which turns out to be quite powerful (we have shown this to be true in other situations also), we consider first an explicit evaluation of the free energy for the static case, corresponding to zero Matsubara frequency (n=0). Thereafter, the time-dependent case is examined. For comparison we consider the calculation of the free energy with use of the more commonly known field theoretical method, assuming for simplicity metallic boundary surfaces.
International Nuclear Information System (INIS)
Ton-That, Tuong
2005-01-01
In a previous paper we gave a generalization of the notion of Casimir invariant differential operators for the infinite-dimensional Lie groups GL ∞ (C) (or equivalently, for its Lie algebra gj ∞ (C)). In this paper we give a generalization of the Casimir invariant differential operators for a class of infinite-dimensional Lie groups (or equivalently, for their Lie algebras) which contains the infinite-dimensional complex classical groups. These infinite-dimensional Lie groups, and their Lie algebras, are inductive limits of finite-dimensional Lie groups, and their Lie algebras, with some additional properties. These groups or their Lie algebras act via the generalized adjoint representations on projective limits of certain chains of vector spaces of universal enveloping algebras. Then the generalized Casimir operators are the invariants of the generalized adjoint representations. In order to be able to explicitly compute the Casimir operators one needs a basis for the universal enveloping algebra of a Lie algebra. The Poincare-Birkhoff-Witt (PBW) theorem gives an explicit construction of such a basis. Thus in the first part of this paper we give a generalization of the PBW theorem for inductive limits of Lie algebras. In the last part of this paper a generalization of the very important theorem in representation theory, namely the Chevalley-Racah theorem, is also discussed
Palasantzas, George
2007-01-01
In this work, we investigate the combined influence of electromagnetic and acoustic Casimir forces on the pull-in voltage of microswitches with self-affine rough plates. It is shown that for plate separations within the micron range the acoustic term arising from pressure fluctuations can influence
Casimir energies in M4≥/sup N/ for even N. Green's-function and zeta-function techniques
International Nuclear Information System (INIS)
Kantowski, R.; Milton, K.A.
1987-01-01
The Green's-function technique developed in the first paper in this series is generalized to apply to massive scalar, vector, second-order tensor, and Dirac spinor fields, as a preliminary to a full graviton calculation. The Casimir energies are of the form u/sub Casimir/ = (1/a 4 )[α/sub N/lna/b)+β/sub N/], where N (even) is the dimension of the internal sphere, a is its radius, and b/sup -1/ is an ultraviolet cutoff (presumably at the Planck scale). The coefficient of the divergent logarithm, α/sub N/, is unambiguously obtained for each field considered. The Green's-function technique gives rise to no difficulties in the evaluation of imaginary-mass-mode contributions to the Casimir energy. In addition, a new, simplified zeta-function technique is presented which is very easily implemented by symbolic programs, and which, of course, gives the same results. An error in a previous zeta-function calculation of the Casimir energy for even N is pointed out
Plasma versus Drude Modeling of the Casimir Force: Beyond the Proximity Force Approximation
Hartmann, Michael; Ingold, Gert-Ludwig; Neto, Paulo A. Maia
2017-07-01
We calculate the Casimir force and its gradient between a spherical and a planar gold surface. Significant numerical improvements allow us to extend the range of accessible parameters into the experimental regime. We compare our numerically exact results with those obtained within the proximity force approximation (PFA) employed in the analysis of all Casimir force experiments reported in the literature so far. Special attention is paid to the difference between the Drude model and the dissipationless plasma model at zero frequency. It is found that the correction to PFA is too small to explain the discrepancy between the experimental data and the PFA result based on the Drude model. However, it turns out that for the plasma model, the corrections to PFA lie well outside the experimental bound obtained by probing the variation of the force gradient with the sphere radius [D. E. Krause et al., Phys. Rev. Lett. 98, 050403 (2007), 10.1103/PhysRevLett.98.050403]. The corresponding corrections based on the Drude model are significantly smaller but still in violation of the experimental bound for small distances between plane and sphere.
International Nuclear Information System (INIS)
Kim, W J; Brown-Hayes, M; Brownell, J H; Dalvit, D A R; Onofrio, R
2009-01-01
We report on measurements of forces acting between two conducting surfaces in a spherical-plane configuration in the 35 nm-1 μm separation range. The measurements are obtained by performing electrostatic calibrations followed by a residuals analysis after subtracting the electrostatic-dependent component. We find in all runs optimal fitting of the calibrations for exponents smaller than the one predicted by electrostatics for an ideal sphere-plane geometry. We also find that the external bias potential necessary to minimize the electrostatic contribution depends on the sphere-plane distance. In spite of these anomalies, by implementing a parametrization-dependent subtraction of the electrostatic contribution we have found evidence for short-distance attractive forces of magnitude comparable to the expected Casimir-Lifshitz force. We finally discuss the relevance of our findings in the more general context of Casimir-Lifshitz force measurements, with particular regard to the critical issues of the electrical and geometrical characterization of the involved surfaces.
Fermions on the low-buckled honey-comb structured lattice plane and classical Casimir-Polder force
Goswami, Partha
2016-05-01
We start with the well-known expression for the vacuum polarization and suitably modify it for 2+1-dimensional spin-orbit coupled (SOC) fermions on the low-buckled honey-comb structured lattice plane described by the low-energy Liu-Yao-Feng-Ezawa (LYFE) model Hamiltonian involving the Dirac matrices in the chiral representation obeying the Clifford algebra. The silicene and germanene fit this description suitably. They have the Dirac cones similar to those of graphene and SOC is much stronger. The system could be normal or ferromagnetic in nature. The silicene turns into the latter type if there is exchange field arising due to the proximity coupling to a ferromagnet (FM) such as depositing Fe atoms to the silicene surface. For the silicene, we find that the many-body effects considerably change the bare Coulomb potential by way of the dependence of the Coulomb propagator on the real-spin, iso-spin and the potential due to an electric field applied perpendicular to the silicene plane. The computation aspect of the Casimir-Polder force (CPF) needs to be investigated in this paper. An important quantity in this process is the dielectric response function (DRF) of the material. The plasmon branch was obtained by finding the zeros of DRF in the long-wavelength limit. This leads to the plasmon frequencies. We find that the collective charge excitations at zero doping, i.e., intrinsic plasmons, in this system, are absent in the Dirac limit. The valley-spin-split intrinsic plasmons, however, come into being in the case of the massive Dirac particles with characteristic frequency close to 10 THz. Our scheme to calculate the Casimir-Polder interaction (CPI) of a micro-particle with a sheet involves replacing the dielectric constant of the sample in the CPI expression obtained on the basis of the Lifshitz theory by the static DRF obtained using the expressions for the polarization function we started with. Though the approach replaces a macroscopic constant by a microscopic
Gauge dynamics in the PNJL model: Color neutrality and Casimir scaling
International Nuclear Information System (INIS)
Abuki, Hiroaki; Fukushima, Kenji
2009-01-01
We discuss a gauge-invariant prescription to take the mean-field approximation self-consistently in the PNJL model (Nambu-Jona-Lasinio model with the Polyakov loop). We first address the problem of non-vanishing color density in normal quark matter, which is an artifact arising from gauge-fixed treatment of the Polyakov loop mean-fields. We then confirm that the gauge average incorporated in our prescription resolves this problem and ensures color neutrality. We point out that the proposed method has an advantage in computing the expectation value of any function of the Polyakov loop matrix. We discuss the Casimir scaling as an immediate application of the method.
Dynamics of the Vacuum and Casimir Analogs to the Hydrogen Atom
White, Harold; Vera, Jerry; Bailey, Paul; March, Paul; Lawrence, Tim; Sylvester, Andre; Brady, David
2015-01-01
This paper will discuss the current viewpoint of the vacuum state and explore the idea of a "natural" vacuum as opposed to immutable, non-degradable vacuum. This concept will be explored for all primary quantum numbers to show consistency with observation at the level of Bohr theory. A comparison with the Casimir force per unit area will be made, and an explicit function for the spatial variation of the vacuum density around the atomic nucleus will be derived. This explicit function will be numerically modeled using the industry multi-physics tool, COMSOL(trademark), and the eigenfrequencies for the n = 1 to n = 7 states will be found and compared to expectation.
Irreversible dynamics, Onsager-Casimir symmetry, and an application to turbulence.
Ottinger, Hans Christian
2014-10-01
Irreversible contributions to the dynamics of nonequilibrium systems can be formulated in terms of dissipative, or irreversible, brackets. We discuss the structure of such irreversible brackets in view of a degeneracy implied by energy conservation, where we consider different types of symmetries of the bracket corresponding to the Onsager and Casimir symmetries of linear irreversible thermodynamics. Slip and turbulence provide important examples of antisymmetric irreversible brackets and offer guidance for the more general modeling of irreversible dynamics without entropy production. Conversely, turbulence modeling could benefit from elucidating thermodynamic structure. The examples suggest constructing antisymmetric irreversible brackets in terms of completely antisymmetric functions of three indices. Irreversible brackets without well-defined symmetry properties can arise for rare events, causing big configurational changes.
Brevik, Iver
2012-09-01
The main part of this paper is to present an updated review of the Casimir energy at zero and finite temperature for the transverse oscillations of a piecewise uniform closed string. We make use of three different regularizations: the cutoff method, the complex contour integration method and the zeta-function method. The string model is relativistic, in the sense that the velocity of sound is for each string piece set equal to the velocity of light. In this sense the theory is analogous to the electromagnetic theory in a dielectric medium in which the product of permittivity and permeability is equal to unity (an isorefractive medium). We demonstrate how the formalism works for a two-piece string, and for a 2N-piece string, and show how in the latter case a compact recursion relation serves to facilitate the formalism considerably. The Casimir energy turns out to be negative, and the more so the larger the number of pieces in the string. The two-piece string is quantized in D-dimensional spacetime, in the limit when the ratio between the two tensions is very small. We calculate the free energy and other thermodynamic quantities, demonstrate scaling properties, and comment finally on the meaning of the Hagedorn critical temperature for the two-piece string. Thereafter, as a novel development we present a scalar field theory for a real field in three-dimensional space in a potential rising linearly with a longitudinal coordinate z in the interval 0 birthday devoted to ‘Applications of zeta functions and other spectral functions in mathematics and physics’.
International Nuclear Information System (INIS)
Lim, S C; Teo, L P
2007-01-01
We derive rigorously explicit formulae of the Casimir free energy at finite temperature for massless scalar field and electromagnetic field confined in a closed rectangular cavity with different boundary conditions by a zeta regularization method. We study both the low and high temperature expansions of the free energy. In each case, we write the free energy as a sum of a polynomial in temperature plus exponentially decay terms. We show that the free energy is always a decreasing function of temperature. In the cases of massless scalar field with the Dirichlet boundary condition and electromagnetic field, the zero temperature Casimir free energy might be positive. In each of these cases, there is a unique transition temperature (as a function of the side lengths of the cavity) where the Casimir energy changes from positive to negative. When the space dimension is equal to two and three, we show graphically the dependence of this transition temperature on the side lengths of the cavity. Finally we also show that we can obtain the results for a non-closed rectangular cavity by letting the size of some directions of a closed cavity go to infinity, and we find that these results agree with the usual integration prescription adopted by other authors
De vette jaren: de Commissie-Casimir en het Nederlandse wetenschapsbeleid 1957-1970
Directory of Open Access Journals (Sweden)
David Baneke
2012-11-01
Full Text Available The Years of Abundance: the Casimir Committee and Dutch Science Policy 1957–1970 In October 1958, a committee of six prominent Dutch scientists and industrial managers presented a brief report in which they requested a major increase of the science budget. This report has been described as a turning point in the history of science in the Netherlands, signaling the beginning of a decade of rapid growth of funding for ‘pure’ research. Surprisingly little is known about the backgrounds of this report, however. In this paper, I analyze its origin, its relation to contemporary higher education policy, and its consequences. As it turns out, the report was less revolutionary than is usually assumed: it mostly reinforced developments that had already begun earlier. Furthermore, Sputnik and the Cold War were not as important as is often claimed. This paper also suggests a reinterpretation of the justification of the government spending on academic research after the Second World War. Producing skilled researchers for industry was at least as important as produc- ing new knowledge.
Casimir meets Poisson: improved quark/gluon discrimination with counting observables
Frye, Christopher; Larkoski, Andrew J.; Thaler, Jesse; Zhou, Kevin
2017-09-01
Charged track multiplicity is among the most powerful observables for discriminating quark- from gluon-initiated jets. Despite its utility, it is not infrared and collinear (IRC) safe, so perturbative calculations are limited to studying the energy evolution of multiplicity moments. While IRC-safe observables, like jet mass, are perturbatively calculable, their distributions often exhibit Casimir scaling, such that their quark/gluon discrimination power is limited by the ratio of quark to gluon color factors. In this paper, we introduce new IRC-safe counting observables whose discrimination performance exceeds that of jet mass and approaches that of track multiplicity. The key observation is that track multiplicity is approximately Poisson distributed, with more suppressed tails than the Sudakov peak structure from jet mass. By using an iterated version of the soft drop jet grooming algorithm, we can define a "soft drop multiplicity" which is Poisson distributed at leading-logarithmic accuracy. In addition, we calculate the next-to-leading-logarithmic corrections to this Poisson structure. If we allow the soft drop groomer to proceed to the end of the jet branching history, we can define a collinear-unsafe (but still infrared-safe) counting observable. Exploiting the universality of the collinear limit, we define generalized fragmentation functions to study the perturbative energy evolution of collinear-unsafe multiplicity.
Directory of Open Access Journals (Sweden)
Agnieszka Skrodzka
2016-12-01
Full Text Available The young Casimir Vasa was brought up at the court of his father, Sigismund III Vasa, in the atmosphere of great devotion, which made him enter the order of Jesuits. Even though he decided to leave the monastery and to take the Polish crown, he came back to the life of a monk after his abdication. The present paper presents the very few pieces of art commemorating the monastic life of John Casimir: an emblem, a medal, some prints and his tomb in Paris. All those objects demonstrate the deep piety of the king.
Directory of Open Access Journals (Sweden)
Michael A. Persinger
2015-09-01
Full Text Available The ~1.5 × 10−20 J which is considered a universal quantity and is associated with the movement of protons in water also relates to the ratio of the magnetic moment of a proton divided by its unit charge, multiplied by viscosity and applied over the O-H distance. There is quantitative evidence that thixotropy, the “spontaneous” increased viscosity in water when undisturbed, originates from the transformation of virtual particles or vacuum oscillations to real states through conversion of Casimir-magnetic energies that involve the frequency of the neutral hydrogen line and the upper bound threshold value for intergalactic magnetic fields. The results indicate that ½ of a single electron orbit is real (particle and the other ½ is virtual (wave. The matter equivalent per s for virtual-to-real states for electrons in 1 mL of water with a neutral pH is consistent with the numbers of protons (H+ and the measured range of molecules in the coherent domains for both width and duration of growth and is similar to widths of intergalactic dust grains from which planets and stars may condense. The de Broglie momentum for the lower boundary of the width of coherent domains multiplied by the fine structure velocity of an electron is concurrent with the quantum when one proton is being removed from another and when the upper boundary of the rest mass of a photon is transformed by the product of velocities for putative “entanglement” and light. Theoretical and experimental results indicate that components of thixotropy, such as specific domains of intercalated water molecules, could display excess correlations over very large distances. Because the energies of the universal quantity and water converge it may be a special conduit for discrete transformations from virtual to real states.
Effect of intermolecular force on the static/dynamic behaviour of M/NEM devices.
Kim, Namjung; Aluru, N R
2014-12-05
Advances made in the fabrication of micro/nano-electromechanical (M/NEM) devices over the last ten years necessitate the understanding of the attractive force that arises from quantum fluctuations (generally referred to as Casimir effects) [Casimir H B G 1948 Proc. K. Ned. Akad. Wet. 51 793]. The fundamental mechanisms underlying quantum fluctuations have been actively investigated through various theoretical and experimental approaches. However, the effect of the force on M/NEM devices has not been fully understood yet, especially in the transition region involving gaps ranging from 10 nm to 1 μm, due to the complexity of the force. Here, we numerically calculate the Casimir effects in M/NEM devices by using the Lifshitz formula, the general expression for the Casimir effects [Lifshitz E 1956 Sov. Phys. JETP 2 73]. Since the Casimir effects are highly dependent on the permittivity of the materials, the Kramer-Kronig relation [Landau L D, Lifshitz E M and Pitaevskii L P 1984 Electrodynamics of Continuous Media (New York: Pergamon Press)] and the optical data for metals and dielectrics are used in order to obtain the permittivity. Several simplified models for the permittivity of the materials, such as the Drude and Lorentz models [Jackson J D 1975 Classical Electrodynamics (New York: Wiley)], are also used to extrapolate the optical data. Important characteristic values of M/NEM devices, such as the pull-in voltage, pull-in gap, detachment length, etc, are calculated for devices operating in the transition region. Our results show that accurate predictions for the pull-in behaviour are possible when the Lifshitz formula is used instead of the idealized expressions for Casimir effects. We expand this study into the dynamics of M/NEM devices, so that the time and frequency response of M/NEM devices with Casimir effects can be explored.
Effect of intermolecular force on the static/dynamic behaviour of M/NEM devices
Kim, Namjung; Aluru, N. R.
2014-12-01
Advances made in the fabrication of micro/nano-electromechanical (M/NEM) devices over the last ten years necessitate the understanding of the attractive force that arises from quantum fluctuations (generally referred to as Casimir effects) [Casimir H B G 1948 Proc. K. Ned. Akad. Wet. 51 793]. The fundamental mechanisms underlying quantum fluctuations have been actively investigated through various theoretical and experimental approaches. However, the effect of the force on M/NEM devices has not been fully understood yet, especially in the transition region involving gaps ranging from 10 nm to 1 μm, due to the complexity of the force. Here, we numerically calculate the Casimir effects in M/NEM devices by using the Lifshitz formula, the general expression for the Casimir effects [Lifshitz E 1956 Sov. Phys. JETP 2 73]. Since the Casimir effects are highly dependent on the permittivity of the materials, the Kramer-Kronig relation [Landau L D, Lifshitz E M and Pitaevskii L P 1984 Electrodynamics of Continuous Media (New York: Pergamon Press)] and the optical data for metals and dielectrics are used in order to obtain the permittivity. Several simplified models for the permittivity of the materials, such as the Drude and Lorentz models [Jackson J D 1975 Classical Electrodynamics (New York: Wiley)], are also used to extrapolate the optical data. Important characteristic values of M/NEM devices, such as the pull-in voltage, pull-in gap, detachment length, etc, are calculated for devices operating in the transition region. Our results show that accurate predictions for the pull-in behaviour are possible when the Lifshitz formula is used instead of the idealized expressions for Casimir effects. We expand this study into the dynamics of M/NEM devices, so that the time and frequency response of M/NEM devices with Casimir effects can be explored.
Effect of intermolecular force on the static/dynamic behaviour of M/NEM devices
International Nuclear Information System (INIS)
Kim, Namjung; Aluru, N R
2014-01-01
Advances made in the fabrication of micro/nano-electromechanical (M/NEM) devices over the last ten years necessitate the understanding of the attractive force that arises from quantum fluctuations (generally referred to as Casimir effects) [Casimir H B G 1948 Proc. K. Ned. Akad. Wet. 51 793]. The fundamental mechanisms underlying quantum fluctuations have been actively investigated through various theoretical and experimental approaches. However, the effect of the force on M/NEM devices has not been fully understood yet, especially in the transition region involving gaps ranging from 10 nm to 1 μm, due to the complexity of the force. Here, we numerically calculate the Casimir effects in M/NEM devices by using the Lifshitz formula, the general expression for the Casimir effects [Lifshitz E 1956 Sov. Phys. JETP 2 73]. Since the Casimir effects are highly dependent on the permittivity of the materials, the Kramer–Kronig relation [Landau L D, Lifshitz E M and Pitaevskii L P 1984 Electrodynamics of Continuous Media (New York: Pergamon Press)] and the optical data for metals and dielectrics are used in order to obtain the permittivity. Several simplified models for the permittivity of the materials, such as the Drude and Lorentz models [Jackson J D 1975 Classical Electrodynamics (New York: Wiley)], are also used to extrapolate the optical data. Important characteristic values of M/NEM devices, such as the pull-in voltage, pull-in gap, detachment length, etc, are calculated for devices operating in the transition region. Our results show that accurate predictions for the pull-in behaviour are possible when the Lifshitz formula is used instead of the idealized expressions for Casimir effects. We expand this study into the dynamics of M/NEM devices, so that the time and frequency response of M/NEM devices with Casimir effects can be explored. (paper)
International Nuclear Information System (INIS)
Le Van Hop.
1989-12-01
The combinatorics computation is used to describe the Casimir operators of the symplectic Lie Algebra. This result is applied for determining the Center of the enveloping Algebra of the semidirect Product of the Heisenberg Lie Algebra and the symplectic Lie Algebra. (author). 10 refs
International Nuclear Information System (INIS)
Mostepanenko, V M; Babb, J F; Caride, A O; Klimchitskaya, G L; Zanette, S I
2006-01-01
The Casimir-Polder and van der Waals interactions between an atom and a flat cavity wall are investigated under the influence of real conditions including the dynamic polarizability of the atom, actual conductivity of the wall material and nonzero temperature of the wall. The cases of different atoms near metal and dielectric walls are considered. It is shown that to obtain accurate results for the atom-wall interaction at short separations, one should use the complete tabulated optical data for the complex refractive index of the wall material and the accurate dynamic polarizability of an atom. At relatively large separations in the case of a metal wall, one may use the plasma model dielectric function to describe the dielectric properties of the wall material. The obtained results are important for the theoretical interpretation of experiments on quantum reflection and Bose-Einstein condensation
Directory of Open Access Journals (Sweden)
Amir R. Askari
2014-01-01
Full Text Available The influence of the Casimir excitation on dynamic pull-in instability of a nanoelectromechanical beam under ramp-input voltage is studied. The ramp-input actuation has applications in frequency sweeping of RF-N/MEMS. The presented model is nonlinear due to the inherent nonlinearity of electrostatics and the Casimir excitations as well as the geometric nonlinearity of midplane stretching. A Galerkin based reduced order modeling is utilized. It is found that the calculated dynamic pull-in ramp input voltage leads to dynamic pull-in step input voltage by increasing the slope of voltage-time diagram. This fact is utilized to verify the results of present study.
Slicing the vacuum: New accelerating mirror solutions of the dynamical Casimir effect
Good, Michael R. R.; Linder, Eric V.
2017-12-01
Radiation from accelerating mirrors in a Minkowski spacetime provides insights into the nature of horizons, black holes, and entanglement entropy. We introduce new, simple, symmetric and analytic moving mirror solutions and study their particle, energy, and entropy production. This includes an asymptotically static case with finite emission that is the black hole analog of complete evaporation. The total energy, total entropy, total particles, and spectrum are the same on both sides of the mirror. We also study its asymptotically inertial, drifting analog (which gives a black hole remnant) to explore differences in finite and infinite production.
The energy-momentum tensor, the trace identity and the Casimir effect
Indian Academy of Sciences (India)
The trace identity associated with the scale transformation → ′ = -ρ on the Lagrangian density for the noninteracting electromagnetic field in the covariant gauge is shown to be violated on a single plate on which the Dirichlet boundary condition (; 1, 2, 3 = -) = 0 is imposed. It is however respected in ...
Finite-temperature Casimir effect in the presence of nonlinear dielectrics
DEFF Research Database (Denmark)
Kheirandish, Fardin; Amooghorban, Ehsan; Soltani, Morteza
2011-01-01
Starting from a Lagrangian, the electromagnetic field in the presence of a nonlinear dielectric medium is quantized using path-integral techniques, and correlation functions of different fields are calculated. The susceptibilities of the nonlinear medium are obtained, and their relations to coupl......Starting from a Lagrangian, the electromagnetic field in the presence of a nonlinear dielectric medium is quantized using path-integral techniques, and correlation functions of different fields are calculated. The susceptibilities of the nonlinear medium are obtained, and their relations...
The energy–momentum tensor, the trace identity and the Casimir effect
Indian Academy of Sciences (India)
ρxµ on the Lagrangian density for the noninteracting electromagnetic field in the co- variant gauge is shown to be violated on a single plate on which the Dirichlet boundary condition Aµ(t, x1, x2,x3 = −a) = 0 is imposed. It is however respected ...
A Gedanken spacecraft that operates using the quantum vacuum (Dynamic Casimir effect)
Maclay, G. Jordan; Forward, Robert L.
2003-01-01
Conventional rockets are not a suitable technology for deep space missions. Chemical rockets require a very large weight of propellant, travel very slowly compared to light speed, and require significant energy to maintain operation over periods of years. For example, the 722 kg Voyager spacecraft required 13,600 kg of propellant to launch and would take about 80,000 years to reach the nearest star, Proxima Centauri, about 4.3 light years away. There have been various attempts at developing i...
The energy–momentum tensor, the trace identity and the Casimir effect
Indian Academy of Sciences (India)
Pramana – Journal of Physics. Current Issue : Vol. 90, Issue 2 · Current Issue Volume 90 | Issue 2. February 2018. Home · Volumes & Issues · Special Issues · Forthcoming Articles · Search · Editorial Board · Information for Authors · Subscription ...
International Nuclear Information System (INIS)
Campoamor-Stursberg, R
2008-01-01
We show that the Inoenue-Wigner contraction naturally associated to a reduction chain s implies s' of semisimple Lie algebras induces a decomposition of the Casimir operators into homogeneous polynomials, the terms of which can be used to obtain additional mutually commuting missing label operators for this reduction. The adjunction of these scalars that are no more invariants of the contraction allow to solve the missing label problem for those reductions where the contraction provides an insufficient number of labelling operators.
Valchev, Galin; Dantchev, Daniel
2017-08-01
We study systems in which both long-ranged van der Waals and critical Casimir interactions are present. The latter arise as an effective force between bodies when immersed in a near-critical medium, say a nonpolar one-component fluid or a binary liquid mixture. They are due to the fact that the presence of the bodies modifies the order parameter profile of the medium between them as well as the spectrum of its allowed fluctuations. We study the interplay between these forces, as well as the total force (TF) between a spherical colloid particle and a thick planar slab and between two spherical colloid particles. We do that using general scaling arguments and mean-field-type calculations utilizing the Derjaguin and the surface integration approaches. They both are based on data of the forces between two parallel slabs separated at a distance L from each other, confining the fluctuating fluid medium characterized by its temperature T and chemical potential μ. The surfaces of the colloid particles and the slab are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials, ensuring the so-called (+,+) boundary conditions. On the other hand, the core region of the slab and the particles influence the fluid by long-ranged competing dispersion potentials. We demonstrate that for a suitable set of colloids-fluid, slab-fluid, and fluid-fluid coupling parameters, the competition between the effects due to the coatings and the core regions of the objects involved result, when one changes T, μ, or L, in sign change of the Casimir force (CF) and the TF acting between the colloid and the slab, as well as between the colloids. This can be used for governing the behavior of objects, say colloidal particles, at small distances, say in colloid suspensions for preventing flocculation. It can also provide a strategy for solving problems with handling, feeding
Valchev, Galin; Dantchev, Daniel
2017-08-01
We study systems in which both long-ranged van der Waals and critical Casimir interactions are present. The latter arise as an effective force between bodies when immersed in a near-critical medium, say a nonpolar one-component fluid or a binary liquid mixture. They are due to the fact that the presence of the bodies modifies the order parameter profile of the medium between them as well as the spectrum of its allowed fluctuations. We study the interplay between these forces, as well as the total force (TF) between a spherical colloid particle and a thick planar slab and between two spherical colloid particles. We do that using general scaling arguments and mean-field-type calculations utilizing the Derjaguin and the surface integration approaches. They both are based on data of the forces between two parallel slabs separated at a distance L from each other, confining the fluctuating fluid medium characterized by its temperature T and chemical potential μ . The surfaces of the colloid particles and the slab are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials, ensuring the so-called (+,+) boundary conditions. On the other hand, the core region of the slab and the particles influence the fluid by long-ranged competing dispersion potentials. We demonstrate that for a suitable set of colloids-fluid, slab-fluid, and fluid-fluid coupling parameters, the competition between the effects due to the coatings and the core regions of the objects involved result, when one changes T , μ , or L , in sign change of the Casimir force (CF) and the TF acting between the colloid and the slab, as well as between the colloids. This can be used for governing the behavior of objects, say colloidal particles, at small distances, say in colloid suspensions for preventing flocculation. It can also provide a strategy for solving problems with handling, feeding
International Nuclear Information System (INIS)
Barut, A.O.; Dowling, J.P.
1986-12-01
Using a previously formulated theory of quantum electrodynamics based on self-energy, we give a general method for computing the Lamb shift and related Casimir-Polder energies for a quantum system in the vicinity of perfectly conducting boundaries. Our results are exact and easily extendable to a full covariant relativistic form. As a particular example we apply the method to an atom near an infinite conducting plane, and we recover the standard QED results (which are known only in the dipole approximation) in a simple and straightforward manner. This is accomplished in the context of the new theory which is not second quantized and contains no vacuum fluctuations. (author)
Milton, Kimball A.; Fulling, Stephen A.; Parashar, Prachi; Kalauni, Pushpa; Murphy, Taylor
2016-04-01
Motivated by a desire to understand quantum fluctuation energy densities and stress within a spatially varying dielectric medium, we examine the vacuum expectation value for the stress tensor of a scalar field with arbitrary conformal parameter, in the background of a given potential that depends on only one spatial coordinate. We regulate the expressions by incorporating a temporal-spatial cutoff in the (imaginary) time and transverse-spatial directions. The divergences are captured by the zeroth- and second-order WKB approximations. Then the stress tensor is "renormalized" by omitting the terms that depend on the cutoff. The ambiguities that inevitably arise in this procedure are both duly noted and restricted by imposing certain physical conditions; one result is that the renormalized stress tensor exhibits the expected trace anomaly. The renormalized stress tensor exhibits no pressure anomaly, in that the principle of virtual work is satisfied for motions in a transverse direction. We then consider a potential that defines a wall, a one-dimensional potential that vanishes for z 0 , for z >0 . Previously, the stress tensor had been computed outside of the wall, whereas now we compute all components of the stress tensor in the interior of the wall. The full finite stress tensor is computed numerically for the two cases where explicit solutions to the differential equation are available, α =1 and 2. The energy density exhibits an inverse linear divergence as the boundary is approached from the inside for a linear potential, and a logarithmic divergence for a quadratic potential. Finally, the interaction between two such walls is computed, and it is shown that the attractive Casimir pressure between the two walls also satisfies the principle of virtual work (i.e., the pressure equals the negative derivative of the energy with respect to the distance between the walls).
Chen, Shao-Guang
According to f =d(mv)/dt=m(dv/dt)+ v(dm/dt), a same gravitational formula had been de-duced from the variance in physical mass of QFT and from the variance in mass of inductive energy-transfer of GR respectively: f QF T = f GR = -G (mM/r2 )((r/r)+(v/c)) when their interaction-constants are all taken the experimental values (H05-0029-08, E15-0039-08). f QF T is the quasi-Casimir pressure. f GR is equivalent to Einstein's equation, then more easy to solve it. The hypothesis of the equivalent principle is not used in f QF T , but required by f GR . The predictions of f QF T and f GR are identical except that f QF T has quantum effects but f GR has not and f GR has Lense-Thirring effect but f QF T has not. The quantum effects of gravitation had been verified by Nesvizhevsky et al with the ultracold neutrons falling in the earth's gravitational field in 2002. Yet Lense-Thirring effect had not been measured by GP-B. It shows that f QF T is essential but f GR is phenomenological. The macro-f QF T is the statistic average pressure collided by net virtual neutrinos ν 0 flux (after self-offset in opposite directions) and in direct proportion to the mass. But micro-f QF T is in direct proportion to the scattering section. The electric mass (in inverse proportion to de Broglie wavelength λ) far less than nucleonic mass and the electric scattering section (in direct proportion to λ2 ) far large than that of nucleon, then the net ν 0 flux pressure exerted to electron far large than that to nucleon and the electric displacement far large than that of nucleon, it causes the gravitational polarization of positive-negative charge center separation. Because the gravity far less than the electromagnetic binding force, in atoms the gravitational polarization only produces a little separation. But the net ν 0 flux can press a part freedom electrons in plasma of ionosphere into the earth's surface, the static electric force of redundant positive ions prevents electrons from further
Hertzberg, Jared B; Aksit, Mahmut; Otelaja, Obafemi O; Stewart, Derek A; Robinson, Richard D
2014-02-12
Thermal transport in nanostructures is strongly affected by phonon-surface interactions, which are expected to depend on the phonon's wavelength and the surface roughness. Here we fabricate silicon nanosheets, measure their surface roughness (∼ 1 nm) using atomic force microscopy (AFM), and assess the phonon scattering rate in the sheets with a novel technique: a microscale phonon spectrometer. The spectrometer employs superconducting tunnel junctions (STJs) to produce and detect controllable nonthermal distributions of phonons from ∼ 90 to ∼ 870 GHz. This technique offers spectral resolution nearly 10 times better than a thermal conductance measurement. We compare measured phonon transmission rates to rates predicted by a Monte Carlo model of phonon trajectories, assuming that these trajectories are dominated by phonon-surface interactions and using the Ziman theory to predict phonon-surface scattering rates based on surface topology. Whereas theory predicts a diffuse surface scattering probability of less than 40%, our measurements are consistent with a 100% probability. Our nanosheets therefore exhibit the so-called "Casimir limit" at a much lower frequency than expected if the phonon scattering rates follow the Ziman theory for a 1 nm surface roughness. Such a result holds implications for thermal management in nanoscale electronics and the design of nanostructured thermoelectrics.
Inverse Square Law of Gravitation in (2+1)-Dimensional Space-Time as a Consequence of Casimir Energy
Soleng, H. H.
1993-01-01
The gravitational effect of vacuum polarization in space exterior to a particle in (2+1)-dimensional Einstein theory is investigated. In the weak field limit this gravitational field corresponds to an inverse square law of gravitational attraction, even though the gravitational mass of the quantum vacuum is negative. The paradox is resolved by considering a particle of finite extension and taking into account the vacuum polarization in its interior.
More on renormalization ambiguities: effective action and model summation
International Nuclear Information System (INIS)
Albuquerque, Luis C. de
1997-01-01
The one-loop effective action is formally equivalent to the summation of the energies associated with the vacuum fluctuations of the quantum field. However, renormalization effects may introduce an anormalous scale dependence in the one-loop effective action, and also in the summation of zero-point energies. Recently, it has been argued that these two methods lead to distinct results for the Casimir energy. We show that the one-loop effective action is completely equivalent to the zero-point energy summation, working in a regularized way since beginning. Hence, we clarify some statements made earlier in the literature. (author)
Koochi, Ali; Hosseini-Toudeshky, Hossein; Abadyan, Mohamadreza
2018-03-01
Herein, a corrected theoretical model is proposed for modeling the static and dynamic behavior of electrostatically actuated narrow-width nanotweezers considering the correction due to finite dimensions, size dependency and surface energy. The Gurtin-Murdoch surface elasticity in conjunction with the modified couple stress theory is employed to consider the coupling effect of surface stresses and size phenomenon. In addition, the model accounts for the external force corrections by incorporating the impact of narrow width on the distribution of Casimir attraction, van der Waals (vdW) force and the fringing field effect. The proposed model is beneficial for the precise modeling of the narrow nanotweezers in nano-scale.
Gholami, R.; Ansari, R.
2018-01-01
Presented herein is the study of grain size, grain surface energy and small scale effects on the nonlinear pull-in instability and free vibration of electrostatic nanoscale actuators made of nanocrystalline silicon (Nc-Si). A Mori-Tanaka micromechanical model is utilized to calculate the effective material properties of Nc-Si considering material structure inhomogeneity, grain size and grain surface energy. The small-scale effect is also taken into account using Mindlin’s strain gradient theory. Governing equations are derived in the discretized weak form using the variational differential quadrature method based on the third-order shear defamation beam theory in conjunction with the von Kármán hypothesis. The electrostatic actuation is modeled considering the fringing field effects based upon the parallel plate approximation. Moreover, the Casimir force effect is considered. The pseudo arc-length continuation technique is used to obtain the applied voltage-deflection curve of Nc-Si actuators. Then, a time-dependent small disturbance around the deflected configuration is assumed to solve the free vibration problem. By performing a numerical study, the influences of various factors such as length scale parameter, volume fraction of the inclusion phase, density ratio, average inclusion radius and Casimir force on the pull-in instability and free vibration of Nc-Si actuators are investigated.
Critical Casimir forces and anomalous wetting
Indian Academy of Sciences (India)
the origin of artefacts in the profiles found by Ueno et al, whose fringe patterns were severely bent, due to inhomogeneous stresses on the two cell windows. In our new experiment, we have found zero contact angle in the whole temperature range. Two examples of profiles are shown in figure 8. At low temperature (271 mK).
2190-IJBCS-Article-Casimir Anouma
African Journals Online (AJOL)
hp
breadmaking were assessed by sensory analysis of products obtained. Both roots and fermented flours were energizing foods. Moisture (6.09-10.49%), protein (1.12-1.57%), ash ... Keywords: Gelatinized food, yace cultivar, sensory evaluation, composite flour, bread. ...... parameters that guide consumer choice.
Critical Casimir forces and anomalous wetting
Indian Academy of Sciences (India)
range forces responsible for this exception. By using .... using an ϵ-expansion method. For periodic boundary conditions and ..... interface profile is obtained by subtracting the optical path without the interface from the optical path with the interface ...
1092-IJBCS-Article-Casimir Anouma KOKO
African Journals Online (AJOL)
KODJIO NORBERT
product was ground and sieved with a 200 µm mesh sieve. Proximate composition and the ability of fermented flour to be processed into placali appreciated by consumers were evaluated. Moisture, protein, ash, fat, total sugars and cyanide contents were low while starch, total carbohydrate and energy contents were high.
Quantum dissipative effects in moving imperfect mirrors: Sidewise and normal motions
International Nuclear Information System (INIS)
Fosco, Cesar D.; Lombardo, Fernando C.; Mazzitelli, Francisco D.
2011-01-01
We extend our previous work on the functional approach to the dynamical Casimir effect, to compute dissipative effects due to the relative motion of two flat, parallel, imperfect mirrors in vacuum. The interaction between the internal degrees of freedom of the mirrors and the vacuum field is modeled with a nonlocal term in the vacuum field action. We consider two different situations: either the motion is 'normal', i.e., the mirrors advance or recede changing the distance a(t) between them; or it is 'parallel', namely, a remains constant, but there is a relative sliding motion of the mirrors' planes. For the latter, we show explicitly that there is a nonvanishing frictional force, even for a constant shifting speed.
Directory of Open Access Journals (Sweden)
Miguel Conde Pazos
2012-03-01
Full Text Available Throughout the seventeenth century, the Vasa of Poland and the Habsburg family established a series of contacts which would link to the Catholic Monarchy with the events in Eastern Europe. This article addresses a specific event of these relationships: the closure by the French of Prince Casimir on his way to Spain, and subse-quent negotiations between his half-brother, King Ladislaus IV, and the viceroy of Naples, the Duke of Medina de las Torres, to raise an army of punishment to free the prince. In this negotiation between Naples, Madrid, Vienna and Warsaw, the catholic king diplomacy interacted with leading personalities of the Polish court.Durante todo el siglo XVII los Vasa de Polonia y la familia Habsburgo establecieron una serie de contactos que vincularían a la Monarquía Católica con los acontecimientos de la Europa Oriental. El presente artículo trata un suceso concreto de estas relaciones: el encierro por parte de los franceses del príncipe Casimiro cuando se dirigía hacia España, y las ulteriores negociaciones entre su medio hermano, el rey Ladislao IV, y el virrey de Nápoles, el duque de Medina de las Torres, para levantar un ejército de castigo que liberara al príncipe. En esta negociación entre Nápoles, Madrid, Viena y Varsovia, la diplomacia del rey Católico interactuó con los más destacados personajes de la corte polaca.
Equilibrium & Nonequilibrium Fluctuation Effects in Biopolymer Networks
Kachan, Devin Michael
Fluctuation-induced interactions are an important organizing principle in a variety of soft matter systems. In this dissertation, I explore the role of both thermal and active fluctuations within cross-linked polymer networks. The systems I study are in large part inspired by the amazing physics found within the cytoskeleton of eukaryotic cells. I first predict and verify the existence of a thermal Casimir force between cross-linkers bound to a semi-flexible polymer. The calculation is complicated by the appearance of second order derivatives in the bending Hamiltonian for such polymers, which requires a careful evaluation of the the path integral formulation of the partition function in order to arrive at the physically correct continuum limit and properly address ultraviolet divergences. I find that cross linkers interact along a filament with an attractive logarithmic potential proportional to thermal energy. The proportionality constant depends on whether and how the cross linkers constrain the relative angle between the two filaments to which they are bound. The interaction has important implications for the synthesis of biopolymer bundles within cells. I model the cross-linkers as existing in two phases: bound to the bundle and free in solution. When the cross-linkers are bound, they behave as a one-dimensional gas of particles interacting with the Casimir force, while the free phase is a simple ideal gas. Demanding equilibrium between the two phases, I find a discontinuous transition between a sparsely and a densely bound bundle. This discontinuous condensation transition induced by the long-ranged nature of the Casimir interaction allows for a similarly abrupt structural transition in semiflexible filament networks between a low cross linker density isotropic phase and a higher cross link density bundle network. This work is supported by the results of finite element Brownian dynamics simulations of semiflexible filaments and transient cross-linkers. I
Effective field theories for van der Waals interactions
Brambilla, Nora; Shtabovenko, Vladyslav; Tarrús Castellà, Jaume; Vairo, Antonio
2017-06-01
Van der Waals interactions between two neutral but polarizable systems at a separation R much larger than the typical size of the systems are at the core of a broad sweep of contemporary problems in settings ranging from atomic, molecular and condensed matter physics to strong interactions and gravity. In this paper, we reexamine the dispersive van der Waals interactions between two hydrogen atoms. The novelty of the analysis resides in the usage of nonrelativistic effective field theories of quantum electrodynamics. In this framework, the van der Waals potential acquires the meaning of a matching coefficient in an effective field theory, dubbed van der Waals effective field theory, suited to describe the low-energy dynamics of an atom pair. It may be computed systematically as a series in R times some typical atomic scale and in the fine-structure constant α . The van der Waals potential gets short-range contributions and radiative corrections, which we compute in dimensional regularization and renormalize here for the first time. Results are given in d space-time dimensions. One can distinguish among different regimes depending on the relative size between 1 /R and the typical atomic bound-state energy, which is of order m α2. Each regime is characterized by a specific hierarchy of scales and a corresponding tower of effective field theories. The short-distance regime is characterized by 1 /R ≫m α2 and the leading-order van der Waals potential is the London potential. We also compute next-to-next-to-next-to-leading-order corrections. In the long-distance regime we have 1 /R ≪m α2. In this regime, the van der Waals potential contains contact terms, which are parametrically larger than the Casimir-Polder potential that describes the potential at large distances. In the effective field theory, the Casimir-Polder potential counts as a next-to-next-to-next-to-leading-order effect. In the intermediate-distance regime, 1 /R ˜m α2, a significantly more complex
Proximity effects in cold gases of multiply charged atoms (Review)
Chikina, I.; Shikin, V.
2016-07-01
problems involving Eproxi. Here we are speaking of one or more sharp boundaries formed by the ionic component of a many-particle problem. These may be a metal-vacuum boundary in a standard Casimir cell in a study of the vacuum properties in the 2l gap between conducting media of different kinds or different layered systems (quantum wells) in semiconductors, etc. As the mobile part of the equilibrium near a sharp boundary, electrons can (should) escape beyond the confines of the ion core into a gap 2l with a probability that depends, among other factors, on the properties of Eproxi for the electron cloud inside the conducting walls of the Casimir cell (quantum well). The analog of the Casimir sandwich in semiconductors is the widely used multilayer heterostructures referred to as quantum wells of width 2l with sides made of suitable doped materials, which ensure statistical equilibrium exchange of electrons between the layers of the multilayer structure. The thermal component of the proximity effects in semiconducting quantum wells provides an idea of many features of the dissociation process in doped semiconductors. In particular, a positive Eproxi > 0 (relative to the bottom of the conduction band) indicates that TF donors with a finite density nd ≠ 0 form a degenerate, semiconducting state in the semiconductor. At zero temperature, there is a finite density of free carriers which increases with a power-law dependence on T.
Estimate for the size of the compactification radius of a one extra dimension universe
Energy Technology Data Exchange (ETDEWEB)
Da Rosa, Felipe S [Los Alamos National Laboratory; Pascoal, F [DEPARTAMENTO DE FISICA; Oliveira, L F [CIDADE UNIV; Farina, C [INSTITUTO DE FISICA
2008-01-01
In this work, we use the Casimir effect to probe the existence of one extra dimension. We begin by evaluating the Casimir pressure between two plates in a M{sup 4} x S{sup 1} manifold, and then use an appropriate statistical analysis in order to compare the theoretical expression with a recent experimental data and set bounds for the compactification radius.
Parallel plate structures for optical modulation and casimir force measurement
Syed Nawazuddin, M.B.; Wiegerink, Remco J.; Lammerink, Theodorus S.J.; Elwenspoek, Michael Curt
2009-01-01
Integrated optical switches using mechano-optical sensing are gaining more attention in many fields due to their fast switching speed, large bandwidth and compact devices. In this paper, a micromachined electrostatically actuated metal plate to sense the evanescent field above the waveguide is
Casimir densities for a boundary in Robertson-Walker spacetime
Energy Technology Data Exchange (ETDEWEB)
Saharian, A.A., E-mail: saharian@ictp.i [Department of Physics, Yerevan State University, 1 Alex Manoogian Street, 0025 Yerevan (Armenia); Setare, M.R., E-mail: rezakord@ipm.i [Department of Science of Bijar, University of Kurdistan, Bijar (Iran, Islamic Republic of)
2010-04-12
For scalar and electromagnetic fields we evaluate the vacuum expectation value of the energy-momentum tensor induced by a curved boundary in the Robertson-Walker spacetime with negative spatial curvature. In order to generate the vacuum densities we use the conformal relation between the Robertson-Walker and Rindler spacetimes and the corresponding results for a plate moving by uniform proper acceleration through the Fulling-Rindler vacuum. For the general case of the scale factor the vacuum energy-momentum tensor is presented as the sum of the boundary free and boundary induced parts.
Casimir densities for a boundary in Robertson-Walker spacetime
International Nuclear Information System (INIS)
Saharian, A.A.; Setare, M.R.
2010-01-01
For scalar and electromagnetic fields we evaluate the vacuum expectation value of the energy-momentum tensor induced by a curved boundary in the Robertson-Walker spacetime with negative spatial curvature. In order to generate the vacuum densities we use the conformal relation between the Robertson-Walker and Rindler spacetimes and the corresponding results for a plate moving by uniform proper acceleration through the Fulling-Rindler vacuum. For the general case of the scale factor the vacuum energy-momentum tensor is presented as the sum of the boundary free and boundary induced parts.
Casimir forces in multilayer magnetodielectrics with both gain and loss
DEFF Research Database (Denmark)
Amooghorban, Ehsan; Wubs, Martijn; Mortensen, N. Asger
2011-01-01
A path-integral approach to the quantization of the electromagnetic field in a linearly amplifying magnetodielectric medium is presented. Two continua of inverted harmonic oscillators are used to describe the polarizability and magnetizability of the amplifying medium. The causal susceptibilities...
On boson condensation considering a generalized Casimir example
Voigt, K.
1990-12-01
From the concept of generalized condensation [M. Van den Berg, J. T. Lewis, and J. V. Pulè, Helv. Phys. Acta 59, 1271 (1986)] it is known that two critical densities ρc and ρm exist for a free boson gas. Density ρc is the classical one and ρm is the critical density below which there can be no macroscopic occupation of ground state. A free boson gas is studied in a weak external potential which behaves asymptotically like ||x1||α1+||x2||α2+ṡṡṡ +||xd||αd near the origin. It is shown that there are only two possibilities to get ρc<ρm<∞, namely, α1=α2=∞ and d≥3 (this corresponds to Dirichlet boundary conditions), and α1=2 and d≥2 (i.e., a harmonic oscillator).
Casimir Force Contrast Between Amorphous and Crystalline Phases of AIST
Torricelli, Gauthier; van Zwol, Peter J.; Shpak, Olex; Palasantzas, George; Svetovoy, Vitaly B.; Binns, Chris; Kooi, Bart J.; Jost, Peter; Wuttig, Matthias
2012-01-01
Phase change materials (PCMs) can be rapidly and reversibly switched between the amorphous and crystalline state. The structural transformation is accompanied by a significant change of optical and electronic properties rendering PCMs suitable for rewritable optical data storage and non-volatile
Casimir Force Contrast Between Amorphous and Crystalline Phases of AIST
Torrichelli, G.; van Zwol, P.J.; Shpak, O.; Palasantzas, G.; Svetovoy, Vitaly; Binns, C.; Kooi, B.J.; Jost, P.; Wittig, M.
2012-01-01
Phase change materials (PCMs) can be rapidly and reversibly switched between the amorphous and crystalline state. The structural transformation is accompanied by a signifi cant change of optical and electronic properties rendering PCMs suitable for rewritable optical data storage and nonvolatile
Symmetries and casimir of an extended classical long wave system
Indian Academy of Sciences (India)
In this paper, we derive Lie point, generalized, master and time-dependent symmetries of a dispersionless equation, which is an extension of a classical long wave system. This equation also admits an infinite-dimensional Lie algebraic structure of Virasoro-type, as in the dispersive integrable systems. We discuss the ...
Global consequences of a local Casimir force : Adhered cantilever
Svetovoy, V. B.; Melenev, A. E.; Lokhanin, M. V.; Palasantzas, G.
2017-01-01
Although stiction is a cumbersome problem for microsystems, it stimulates investigations of surface adhesion. In fact, the shape of an adhered cantilever carries information of the adhesion energy that locks one end to the substrate. We demonstrate here that the system is also sensitive to the
Symmetries and casimir of an extended classical long wave system
Indian Academy of Sciences (India)
... has strong physical reasons and rich mathematical structures. Also, it is of recent interest to obtain many integrable systems from Benney system under various reductions and the study of these reduced systems also assumes significance [6,7]. It is well known that Benney system [1] ut = uux + ghx − uy. ∫ h. 0 ux dy, ht =.
Sadhu, Jyothi Swaroop
Thermoelectrics enable solid-state conversion of heat to electricity by the Seebeck effect, but must provide scalable and cost-effective technology for practical waste heat harvesting. This dissertation explores the thermoelectric properties of electrochemically etched silicon nanowires through experiments, complemented by charge and thermal transport theories. Electrolessly etched silicon nanowires show anomalously low thermal conductivity that has been attributed to the increased scattering of heat conducting phonons from the surface disorder introduced by etching. The reduction is below the incoherent limit for phonon scattering at the boundary, the so-called Casimir limit. A new model of partially coherent phonon transport shows that correlated multiple scattering of phonons off resonantly matched rough surfaces can indeed lead to thermal conductivity below the Casimir limit. Using design guidelines from the theory, silicon nanowires of controllable surface roughness are fabricated using metal-assisted chemical etching. Extensive characterization of the nanowire surfaces using transmission electron microscopy provides surface roughness parameters that are important in testing transport theories. The second part of the dissertation focuses on the implications of increased phonon scattering on the Seebeck coefficient, which is a cumulative effect of non-equilibrium amongst charge carriers and phonons. A novel frequency-domain technique enables simultaneous measurements of the Seebeck coefficient and the thermal conductivity of nanowire arrays. The frequency response measurements isolate the parasitic contributions thus improving upon existing techniques for cross-plane thermoelectric measurements. While the thermal conductivity of nanowires reduces significantly with increased roughness, there is also a significant reduction in the Seebeck coefficient over a wide range of doping. Theoretical fitting of the data reveals that such reduction results from the
International Nuclear Information System (INIS)
Yang, W D; Li, Y D; Wang, X
2016-01-01
An analytical method is presented to investigate the pull-in instability of a carbon nanotube (CNT)-reinforced variable cross-section nanoswitch with a piezoelectric effect. Governing equations with variable coefficients are derived based on the nonlocal beam model with geometrical nonlinearity and are solved using the shooting method. All the nonlinear effects of the piezoelectric voltage, van der Waals force, Casimir force, CNT volume fraction, nonlocal parameters and width ratio on the pull-in instability are investigated. The pull-in electrostatic voltage increases with the increment of nonlocal parameters, which exhibits the significant scale-dependent behavior of nanostructures. The results show that the variable cross-section improves the flexural rigidity of the cantilever-type nanoswitch effectively, and that the piezoelectric effect of the piezoelectric layer is utilized to control the electrostatic force induced by the voltage exerted on the elastic layer, owing to piezoelectric materials’ advantages of rapid response, light weight and low energy consumption. (paper)
Geometrical Dynamics in a Transitioning Superconducting Sphere
Directory of Open Access Journals (Sweden)
Claycomb J. R.
2006-10-01
Full Text Available Recent theoretical works have concentrated on calculating the Casimir effect in curved spacetime. In this paper we outline the forward problem of metrical variation due to the Casimir effect for spherical geometries. We consider a scalar quantum field inside a hollow superconducting sphere. Metric equations are developed describing the evolution of the scalar curvature after the sphere transitions to the normal state.
Directory of Open Access Journals (Sweden)
Fateme Abadian
2017-06-01
Full Text Available The Casimir attraction can significantly interfere the physical response of nanoactuators. The intensity of the Casimir force depends on the geometries of interacting bodies. The present paper is dedicated to model the influence of the Casimir attraction on the electrostatic stability of nanoactuators made of cylindrical conductive nanowire/nanotube. An asymptotic solution, based on path-integral approach, is employed to consider the Casimir force. The continuum theory is employed to derive the constitutive equation of the actuator. The governing nonlinear equations are solved by three different approaches. Various perspectives of the issue including comparison with the van der Waals (vdW force regime, the variation of instability parameters and effect of geometry are addressed.
Cross-coupling effects in chemically non-equilibrium viscous compressible flows
International Nuclear Information System (INIS)
Kustova, E.V.; Giordano, D.
2011-01-01
Graphical abstract: Self-cosistent kinetic-theory description of chemical-reaction rates and mean normal stress in one-temperature viscous compressible gas flows. Reaearch highlights: → In chemically non-equilibrium viscous compressible flows, the rate of each reaction depends on the velocity divergence and rates of all other reactions. → Cross effects between the rates of chemical reactions and normal mean stress can be found in the symmetric form and expressed in terms of the reaction affinities. → In the case of small affinities, the entropy production is unconditionally non-negative; in the case of finite affinities, the entropy production related to the scalar forces has no definite sign. - Abstract: A closed self-consistent description of a one-temperature non-equilibrium reacting flow is presented on the basis of the kinetic theory methods. A general case including internal degrees of freedom, dissociation-recombination and exchange reactions, and arbitrary values of affinities of chemical reactions is considered. Chemical-reaction rates and mean normal stress in viscous compressible flows are studied and a symmetric cross coupling between these terms is found. It is shown that the rate of each chemical reaction and the mean normal stress depend on velocity divergence and affinities of all chemical reactions; the law of mass action is violated in viscous flows. The results obtained in the frame of linear irreversible thermodynamics can be deduced from the proposed model for the particular case of small affinities. The reciprocal Onsager-Casimir relations are verified, the symmetry of kinetic coefficients is demonstrated, and the entropy production in a viscous flow is studied.
Casimir-Polder forces on atoms in the presence of magnetoelectronic bodies
Energy Technology Data Exchange (ETDEWEB)
Buhmann, S.Y.
2007-07-05
In this work, the CP force between a single neutral atom or molecule and neutral magnetoelectric bodies is studied. The focus lies on the pure vacuum CP force, i.e., the electromagnetic field is in general understood to be in its ground state. Furthermore, we assume that the atom-body separation is sufficiently large to ensure that the atom is adequately characterised as an electric dipole, while the body can be described by its macroscopic magnetoelectric properties; and that repulsive exchange forces due to the overlap between the electronic wave functions of the atom and the bodies can be neglected. Interactions due to non-vanishing net charges, permanent electric dipole moments, magnetisability, quadrupole (or higher multipole) polarisabilities of the atom and those resulting from non-local or anisotropic magnetoelectric properties of the bodies are ignored. (orig.)
Curved Space Quantum Field Theory of the 1970S Elucidates Boundary Casimir Energy Today
Fulling, S. A.
2017-03-01
Results of investigations of the divergent vacuum energy at reflecting boundaries in quantum field theory are summarized. The boundary is modeled by a soft rapidly increasing potential barrier such as a power wall. In the model without pressure anomaly and the principle of virtual work is fulfilled.
A verification of quantum field theory – measurement of Casimir force
Indian Academy of Sciences (India)
: F = &z where & is the force constant and z is the cantilever deflection. The cantilever is calibrated and the residual potential difference between the grounded sphere and plate is measured using the electrostatic force between them. The detail ...
The Poisson algebra of the invariant charges of the Nambu-Goto theory: Casimir elements
International Nuclear Information System (INIS)
Pohlmeyer, K.
1988-01-01
The reparametrization invariant ''non-local'' conserved charges of the Nambu-Goto theory form an algebra under Poisson bracket operation. The center of the formal closure of this algebra is determined. The relation of the central elements to the constraints of the Nambu-Goto theory is clarified. (orig.)
Force sensor for chameleon and Casimir force experiments with parallel-plate configuration
Almasi, A.; Brax, P.; Iannuzzi, D.; Sedmik, R.
2015-01-01
The search for non-Newtonian forces has been pursued following many different paths. Recently it was suggested that hypothetical chameleon interactions, which might explain the mechanisms behind dark energy, could be detected in a high-precision force measurement. In such an experiment, interactions
The Low Temperature Corrections to the Casimir Force Between a Sphere and a Plane
Bordag, Michael; Pirozhenko, Irina G.
We calculate the low temperature corrections to the free energy for a sphere in front of a plane. First, the scalar field obeying Dirichet or Neumann boundary conditions is considered. Second, the electromagnetic field is studied, the sphere being perfectly conducting and being a dielectric ball with both, constant permittivity and permittivity of the plasma model.
Loop-Effects in Pseudo-Supersymmetry
Energy Technology Data Exchange (ETDEWEB)
Klein, Matthias
2002-11-01
We analyze the transmission of supersymmetry breaking in brane-world models of pseudo-supersymmetry. In these models two branes preserve different halves of the bulk supersymmetry. Thus supersymmetry is broken although each sector of the model is supersymmetric when considered separately. The world-volume theory on one brane feels the breakdown of supersymmetry only through two-loop interactions involving a coupling to fields from the other brane. In a 5D toy model with bulk vectors, we compute the diagrams that contribute to scalar masses on one brane and find that the masses are proportional to the compactification scale up to logarithmic corrections, m{sup 2} {infinity} (2{pi}R){sup -2} (ln(2{pi}R m{sub S}) - 1.1), where m{sub s} is an ultraviolet cutoff. Thus, for large compactification radii, where this result is valid, the brane scalars acquire a positive mass squared. We also compute the three-loop diagrams relevant to the Casimir energy between the two branes and find E {infinity} (2{pi}R){sup -4}((ln(2{pi}R m{sub S}) - 1.7){sup 2} + 0.2). For large radii, this yields a repulsive Casimir force.
A note on a boundary sine-Gordon model at the free-Fermion point
Murgan, Rajan
2018-02-01
We investigate the free-Fermion point of a boundary sine-Gordon model with nondiagonal boundary interactions for the ground state using auxiliary functions obtained from T - Q equations of a corresponding inhomogeneous open spin-\\frac{1}{2} XXZ chain with nondiagonal boundary terms. In particular, we obtain the Casimir energy. Our result for the Casimir energy is shown to agree with the result from the TBA approach. The analytical result for the effective central charge in the ultraviolet (UV) limit is also verified from the plots of effective central charge for intermediate values of volume.
The design of long range quantum electrodynamical forces and torques between macroscopic bodies
Iannuzzi, D.; Lisanti, M.; Munday, J. N.; Capasso, F.
2005-01-01
The interaction between electrically neutral surfaces at sub-micron separation is dominated by the force arising from quantum fluctuations of the electromagnetic field, known as the Casimir force. This effect has been witnessing a renewed interest because of its potential impact in micro- and
Class and Pedagogy: A Case Study of Two Chicago Preschools
Sanders-Smith, Stephanie C.
2015-01-01
Using a Bernsteinian theoretical framework, this study compares two American early childhood centres, one with a primarily progressive pedagogy (Frank Lloyd Wright Family Centre) and one with a primarily traditional pedagogy (Casimir Pulaski Centre), in high-poverty Chicago neighbourhoods to examine the effects of different pedagogic practices on…
[Gamma scattering in condensed matter with high intensity Moessbauer radiation
International Nuclear Information System (INIS)
1992-01-01
This report discusses: quasielastic scattering studies on glycerol; gamma-ray scattering from alkali halides; lattice dynamics in metals; Moessbauer neutron scattering, x-ray diffraction, and macroscopic studies of high T c superconductors containing tungsten; NiAl scattering studies; and atomic interference factors and nuclear Casimir effect
A New Era of Exotic Electromagnetism
Indian Academy of Sciences (India)
of Snell's law, reversed Doppler effect, Cerenkov radi- ation ... the Snell's law. Light that enters from an ordinary medium to the metamaterial medium will undergo re- fraction opposite to that occuring in the conventional ordinary medium. How could .... In 1948, HBG Casimir predicted the attraction between a pair of neutral, ...
Gauge gravity in noncommutative de Sitter space and pair creation
Energy Technology Data Exchange (ETDEWEB)
Mebarki, N; Khodja, L; Aisaoui, H [Laboratoire de Physique Mathematique et Subatomique, Faculte des Sciences, Mentouri University, Constantine (Algeria); Zaim, S [Departement de Physique, Faculte des Sciences, Universite Hadj Lakhdar, Batna (Algeria)], E-mail: zaimslimane@yahoo.fr
2008-10-15
From the invariance of the generalized space-time non-commutative commutation relations, local Poincare and general coordinate transformations are derived. Moreover, a generalized Dirac equation is obtained. Applied to the de Sitter universe, it is shown that the space-time non-commutativity contributes to the particle creation process and induces a Casimir-like effect.
Indian Academy of Sciences (India)
Anisotropic static solutions in modelling highly compact bodies. M Chaisi and S D Maharaj. 609–614. Particle Physics. The trace identity and the planar Casimir effect .... Field-theoretic calculation of kinetic helicity flux. V Avinash,. Mahendra K Verma and Amar V Chandra. 447–453. Plasma Physics. Plasma–maser instability ...
Joulain, Karl
2006-01-01
Cette habilitation traite des transferts de chaleur et de quantité de mouvement aux courtes échelles d'espace et de temps. Une première partie du travail s'interesse au propriétés du rayonnement thermique en champ proche. Il est montré qu'en présence de matériaux supportant des ondes de surface, le champ électromagnétique d'origine thermique peut voir ses propriétés de cohérence changées entre le champ proche et le champ lointain, en particulier lorsque les matériaux mis en jeu supportent des...
Shpak, O.; Palasantzas, G.
2011-01-01
In this work we describe how the window method, which has been used with ideal Kramers-Kroning (K-K) consistent dielectric functions, is affected by real optical data where some degree of K-K inconsistency is always present. Analysis using measured data of the frequency-dependent dielectric function
Rackson, Charles; Watt, Alex; Kim, Woo-Joong; Seattle University Team
2015-03-01
We report on the development of a high-sensitivity torsion balance using a capacitively-coupled Wheatstone Bridge. The torsion balance will be employed to measure the Casimir Force, with a particular emphasis on the surface patch effects that are ubiquitous on metallic surfaces. We will show that these effects also play a significant role in another class of experiments involving quantum-point contacts between two metal wires.
Quartz Microbalance Study of 400-angstrom Thick Films near the lambda Point
Chan, Moses H. W.
2003-01-01
In a recent measurement we observed the thinning of an adsorbed helium film induced by the confinement of critical fluctuations a few millikelvin below the lambda point. A capacitor set-up was used to measure this Casimir effect. In this poster we will present our measurement of an adsorbed helium film of 400 angstroms near the lambda point with a quartz microbalance. For films this thick, we must take into account the non-linear dynamics of the shear waves in the fluid. In spite of the added complications, we were able to confirm the thinning of the film due to the Casimir effect and the onset of the superfluid transition. In addition, we observe a sharp anomaly at the bulk lambda point, most likely related to critical dissipation of the first sound. This work is carried out in collaboration with Rafael Garcia, Stephen Jordon and John Lazzaretti. This work is funded by NASA's Office of Biological and Physical Research under grant.
Eternal and Evanescent Black Holes: It's All Done With Mirrors
Good, Michael R. R.; Linder, Eric V.
2017-01-01
The analogy between black hole radiation and accelerating mirror radiation (the dynamical Casimir effect) is particularly strong for mirror trajectories giving rise to a constant thermal flux of particles. We present new ways to achieve such thermal plateaus, and customize their finite, semi-infinite, and eternal presence, corresponding to forming/collapsing, complete-evaporation/remnants, and eternal black holes. We find simple expressions for the energy flux in terms of the mirror rapidity ...
Circular Motion of a Small Oscillator in a Zero-Point Field Without External Forces: Is It Possible?
Levin, Yefim S.
2016-01-01
A small dipole oscillator moving along a circular trajectory in zero-point electromagnetic field ( ZPF ) and with a polarization normal to the rotation plane, is considered. Temporal periodicity conditions are imposed on ZPF, associated with the way the rotating oscillator observes ZPF. They are similar to spatial boundary conditions in Casimir phenomenon and therefore result in ZPF spectrum change from continuous one to a discrete one and, as a consequence, an effective temperature of the mo...
Principles and applications of nanomems physics
Santos, Hector
2005-01-01
""Principles and Applications of NanoMEMS Physics"" presents the first unified exposition of the physical principles at the heart of NanoMEMS-based devices and applications. In particular, after beginning with a comprehensive presentation of the fundamentals and limitations of nanotechnology and MEMS fabrication techniques, the book addresses the physics germane to this dimensional regime, namely, quantum wave-particle phenomena, including, the manifestation of charge discreteness, quantized electrostatic actuation, and the Casimir effect, and quantum wave phenomena, including, quantized elect
Spontaneous symmetry breaking and neutral stability in the noncanonical Hamiltonian formalism
International Nuclear Information System (INIS)
Morrison, P.J.; Eliezer, S.
1985-10-01
The noncanonical Hamiltonian formalism is based upon a generalization of the Poisson bracket, a particular form of which is possessed by continuous media fields. Associated with this generalization are special constants of motion called Casimirs. These are constants that can be viewed as being built into the phase space, for they are invariant for all Hamiltonians. Casimirs are important because when added to the Hamiltonian they yield an effective Hamiltonian that produces equilibrium states upon variation. The stability of these states can be ascertained by a second variation. Goldstone's theorem, in its usual context, determines zero eigenvalues of the mass matrix for a given vacuum state, the equilibrium with minimum energy. Here, since for fluids and plasmas the vacuum state is uninteresting, we examine symmetry breaking for general equilibria. Broken symmetries imply directions of neutral stability. Two examples are presented: the nonlinear Alfven wave of plasma physics and the Korteweg-de Vries soliton. 46 refs
International Nuclear Information System (INIS)
Brzoska, A.M.; Lenz, F.; Thies, M.; Negele, J.W.
2005-01-01
A phenomenological analysis of the distribution of Wilson loops in SU(2) Yang-Mills theory is presented in which Wilson loop distributions are described as the result of a diffusion process on the group manifold. It is shown that, in the absence of forces, diffusion implies Casimir scaling and, conversely, exact Casimir scaling implies free diffusion. Screening processes occur if diffusion takes place in a potential. The crucial distinction between screening of fundamental and adjoint loops is formulated as a symmetry property related to the center symmetry of the underlying gauge theory. The results are expressed in terms of an effective Wilson loop action and compared with various limits of SU(2) Yang-Mills theory
Automorphisms of W-algebras and extended rational conformal field theories
International Nuclear Information System (INIS)
Honecker, A.
1992-11-01
Many extended conformal algebras with one generator in addition to the Virasoro field as well as Casimir algebras have non-trivial outer automorphisms which enables one to impose 'twisted' boundary conditions on the chiral fields. We study their effect on the highest weight representations. We give formulae for the enlarged rational conformal field theories in both series of W-algebras with two generators and conjecture a general formula for the additional models in the minimal series of Casimir algebras. A third series of W-algebras with two generators which includes the spin three algebra at c = -2 also has finitely many additional fields in the twisted sector although the model itself is apparently not rational. The additional fields in the twisted sector have applications in statistical mechanics as we demonstrate for Z n -quantum spin chains with a particular type of boundary conditions. (orig.)
Conference on the occasion of the 60th Birthday of Professor Emilio Elizalde
Odintsov, Sergey D; Xambó-Descamps, Sebastian; Cosmology, Quantum Vacuum and Zeta Functions
2011-01-01
Some major developments of physics in the last three decades are addressed by highly qualified specialists in different specific fields. They include renormalization problems in QFT, vacuum energy fluctuations and the Casimir effect in different configurations, and a wealth of applications. A number of closely related issues are also considered. The cosmological applications of these theories play a crucial role and are at the very heart of the book; in particular, the possibility to explain in a unified way the whole history of the evolution of the Universe: from primordial inflation to the present day accelerated expansion. Further, a description of the mathematical background underlying many of the physical theories considered above is provided. This includes the uses of zeta functions in physics, as in the regularization problems in QFT already mentioned, specifically in curved space-time, and in Casimir problems as.
Finite-size effects in the spectrum of the OSp (3 | 2) superspin chain
Frahm, Holger; Martins, Márcio J.
2015-05-01
The low energy spectrum of a spin chain with OSp (3 | 2) supergroup symmetry is studied based on the Bethe ansatz solution of the related vertex model. This model is a lattice realization of intersecting loops in two dimensions with loop fugacity z = 1 which provides a framework to study the critical properties of the unusual low temperature Goldstone phase of the O (N) sigma model for N = 1 in the context of an integrable model. Our finite-size analysis provides strong evidence for the existence of continua of scaling dimensions, the lowest of them starting at the ground state. Based on our data we conjecture that the so-called watermelon correlation functions decay logarithmically with exponents related to the quadratic Casimir operator of OSp (3 | 2). The presence of a continuous spectrum is not affected by a change to the boundary conditions although the density of states in the continua appears to be modified.
Finite-size effects in the spectrum of the OSp(3|2 superspin chain
Directory of Open Access Journals (Sweden)
Holger Frahm
2015-05-01
Full Text Available The low energy spectrum of a spin chain with OSp(3|2 supergroup symmetry is studied based on the Bethe ansatz solution of the related vertex model. This model is a lattice realization of intersecting loops in two dimensions with loop fugacity z=1 which provides a framework to study the critical properties of the unusual low temperature Goldstone phase of the O(N sigma model for N=1 in the context of an integrable model. Our finite-size analysis provides strong evidence for the existence of continua of scaling dimensions, the lowest of them starting at the ground state. Based on our data we conjecture that the so-called watermelon correlation functions decay logarithmically with exponents related to the quadratic Casimir operator of OSp(3|2. The presence of a continuous spectrum is not affected by a change to the boundary conditions although the density of states in the continua appears to be modified.
Newton, A.C.
2017-01-01
Self-assembly, the non-dissipative spontaneous formation of structural order spans many length scales, from amphiphilic molecules forming micelles to stars forming galaxies. This thesis mainly deals with systems on the colloidal length scale where the size of a particle is between a nanometer and a
Side effects are problems that occur when cancer treatment affects healthy tissues or organs. Learn about side effects caused by cancer treatment. Know what signs and symptoms to call your doctor about. Learn about treatments for side effects.
PREFACE: Quantum Field Theory Under the Influence of External Conditions (QFEXT07)
Bordag, M.; Mostepanenko, V. M.
2008-04-01
This special issue contains papers reflecting talks presented at the 8th Workshop on Quantum Field Theory Under the Influence of External Conditions (QFEXT07), held on 17 21 September 2007, at Leipzig University. This workshop gathered 108 physicists and mathematicians working on problems which are focused on the following topics: •Casimir and van der Waals forces—progress in theory and new experiments, applications at micro- and nano-scale •Casimir effect—exact results, approximate methods and mathematical problems •Vacuum quantum effects in classical background fields—renormalization issues, singular backgrounds, applications to particle and high energy physics •Vacuum energy and gravity, vacuum energy in supersymmetric and noncommutative theories. This workshop is part of a series started in 1989 and 1992 in Leipzig by Dieter Robaschik, and continued in 1995, 1998 and 2001 in Leipzig by Michael Bordag. In 2003 this Workshop was organized by Kimball A Milton in Oklahoma, in 2005 by Emilio Elizalde in Barcelona and in 2007 it returned to Leipzig. The field of physics after which this series of workshops is named is remarkably broad. It stretches from experimental work on the measurement of dispersion forces between macroscopic bodies to quantum corrections in the presence of classical background fields. The underlying physical idea is that even in its ground state (vacuum) a quantum system responds to changes in its environment. The universality of this idea makes the field of its application so very broad. The most prominent manifestation of vacuum energy is the Casimir effect. This is, in its original formulation, the attraction between conducting planes due to the vacuum fluctuations of the electromagnetic field. In a sense, this is the long-range tail of the more general dispersion forces acting between macroscopic bodies. With the progress in nanotechnology, dispersion forces become of direct practical significance. On a more theoretical side
Habayeb, A R
1987-01-01
Highlights three principal applications of system effectiveness: hardware system evaluation, organizational development and evaluation, and conflict analysis. The text emphasizes the commonality of the system effectiveness discipline. The first part of the work presents a framework for system effectiveness, partitioning and hierarchy of hardware systems. The second part covers the structure, hierarchy, states, functions and activities of organizations. Contains an extended Appendix on mathematical concepts and also several project suggestions.
Kinigstein, Steven Michael
In writing Further Effects, I intended to illustrate the benefits that are to be had from the use of effects - processing, when applied at the compositional level, rather than as a post-compositional afterthought. When effects are used creatively in the compositional stage, they will influence the very nature of a piece. They are capable of expressing rhythmic and metric ideas. They can alter the natural timbre of an instrument. This can be done on levels of abstraction ranging from discreet subtlety to disguise beyond recognition. There is one effect (known as "pitch shift.") that allows an instrument to play pitches that are well outside of its range. In Further Effects, I direct the performers to use a volume pedal (which I view as a tool, rather than an effect) for the broadened creative use of dynamics that it so efficiently grants. The use of an effects processor and volume pedal creates a need for ancillary equipment. An amplifier, cables, and an electric hook-up (a microphone or a pickup) will be required for each instrument. While an amplifier serves to project the processed sound, there must also be a device or method to suppress unprocessed sound. A great deal of thought and work goes into the use of effects; yet I feel it is wasteful to use this musical resource merely as post-compositional decoration.
Talmage, Sylvia S.; Coutant, Charles C.
1978-01-01
Presents a literature review of the effect of temperature on the biosphere water, covering publications of 1976-77. This review includes the effects of temperature on growth, production, and embryonic and larval development. A list of 401 references is also presented. (HM)
... the placebo. Some people wonder whether it is fair or ethical to give a placebo treatment to ... carefully done using a placebo, so that the true effect of the treatment can be fully understood. ...
... Listen Español Text Size Email Print Share Effective Parenting Page Content Article Body Now that our children ... school play and his soccer games. Your Current Parenting Experiences Spend some time thinking about how you ...
International Nuclear Information System (INIS)
Trott, K.R.
1973-01-01
Following an introduction into the field of cellular radiation effect considering the most important experimental results, the biological significance of the colony formation ability is brought out. The inactivation concept of stem cells does not only prove to be good, according to the present results, in the interpretation of the pathogenesis of acute radiation effects on moult tissue, it also enables chronicle radiation injuries to be interpreted through changes in the fibrous part of the organs. Radiation therapy of tumours can also be explained to a large extent by the radiation effect on the unlimited reproductiveness of tumour cells. The more or less similar dose effect curves for healthy and tumour tissue in practice lead to intermittent irradiation. The dependence of the intermittent doses and intervals on factors such as Elkind recovery, synchronisation, redistribution, reoxygenation, repopulation and regeneration are reviewed. (ORU/LH) [de
STOICA, Anamaria
2011-01-01
This research paper is intended to understand the effects that Facebook, the social networking site has upon us, whether it influences our lives in a good or in a bad way. In order to understand the Facebook Effect we are trying to see how it impacts our lives at economic level,social level, political level, terminology level , psychological level and cultural level . Starting from the question : What does Facebook want? we found several answers consisting in pros and cons of this phenomenon ...
DEFF Research Database (Denmark)
Frost, Jacob
To investigate the use of VTLoE as a basis for formal derivation of functional programs with effects. As a part of the process, a number of issues central to effective formal programming are considered. In particular it is considered how to develop a proof system suitable for pratical reasoning......, how to implement this system in the generic proof assistant Isabelle and finally how to apply the logic and the implementation to programming....
Sernelius, Bo E
2011-01-01
Electromagnetic surface modes are present at all surfaces and interfaces between material of different dielectric properties. These modes have very important effects on numerous physical quantities: adhesion, capillary force, step formation and crystal growth, the Casimir effect etc. They cause surface tension and wetting and they give rise to forces which are important e.g. for the stability of colloids.This book is a useful and elegant approach to the topic, showing how the concept of electromagnetic modes can be developed as a unifying theme for a range of condensed matter physics. The
Surface dependency in thermodynamics of ideal gases
International Nuclear Information System (INIS)
Sisman, Altug
2004-01-01
The Casimir-like size effect rises in ideal gases confined in a finite domain due to the wave character of atoms. By considering this effect, thermodynamic properties of an ideal gas confined in spherical and cylindrical geometries are derived and compared with those in rectangular geometry. It is seen that an ideal gas exhibits an unavoidable quantum surface free energy and surface over volume ratio becomes a control variable on thermodynamic state functions in microscale. Thermodynamics turns into non-extensive thermodynamics and geometry difference becomes a driving force since the surface over volume ratio depends on the geometry
International Nuclear Information System (INIS)
Kato, Hiroo
1975-01-01
In 1948-1953 a large scale field survey was conducted to investigate the possible genetic effects of A-bomb radiation on over 70,000 pregnancy terminations in the cities of Hiroshima and Nagasaki. The indices of possible genetic effect including sex ratio, birth weight, frequency of malformation, stillbirth, neonatal death, deaths within 9 months and anthropometric measurements at 9 months of age for these children were investigated in relation to their parent's exposure status to the A-bomb. There were no detectable genetic effects in this sample, except for a slight change in sex ratio which was in the direction to be expected if exposure had induced sex-linked lethal mutations. However, continued study of the sex ratio, based upon birth certificates in Hiroshima and Nagasaki for 1954-1962, did not confirm the earlier trend. Mortality in these children of A-bomb survivors is being followed using a cohort of 54,000 subjects. No clearly significant effect of parental exposure on survival of the children has been demonstrated up to 1972 (age 17 on the average). On the basis of the regression data, the minimal genetic doubling dose of this type of radiation for mutations resulting in death is estimated at 46 rem for the father and 125 rem for the mother. (auth.)
DEFF Research Database (Denmark)
Heckman, James J.; Lopes, Hedibert F.; Piatek, Rémi
2014-01-01
This paper contributes to the emerging Bayesian literature on treatment effects. It derives treatment parameters in the framework of a potential outcomes model with a treatment choice equation, where the correlation between the unobservable components of the model is driven by a low-dimensional v...... easily be applied....
DEFF Research Database (Denmark)
Mundt, M.; Mathisen, H. M.; Moser, M.
Improving the ventilation effectiveness allows the indoor air quality to be significantly enhanced without the need for higher air changes in the building, thereby avoiding the higher costs and energy consumption associated with increasing the ventilation rates. This Guidebook provides easy-to-un...
Aspects of quantum field theory in curved space-time
Energy Technology Data Exchange (ETDEWEB)
Fulling, S.A. (Texas A and M Univ., College Station, TX (USA). Dept. of Mathematics)
1989-01-01
The theory of quantum fields on curved spacetimes has attracted great attention since the discovery, by Stephen Hawking, of black-hole evaporation. It remains an important subject for the understanding of such contemporary topics as inflationary cosmology, quantum gravity and superstring theory. The topics covered include normal-mode expansions for a general elliptic operator, Fock space, the Casimir effect, the Klein 'paradox', particle definition and particle creation in expanding universes, asymptotic expansion of Green's functions and heat kernels, and renormalization of the stress tensor. (author).
Alpenglow. A signature for chameleons in axion-like particle search experiments
International Nuclear Information System (INIS)
Ahlers, M.; Lindner, A.; Ringwald, A.; Schrempp, L.; Weniger, C.
2007-10-01
We point out that chameleon field theories might reveal themselves as an ''afterglow'' effect in axion-like particle search experiments due to chameleon-photon conversion in a magnetic field. We estimate the parameter space which is accessible by currently available technology and find that afterglow experiments could constrain this parameter space in a way complementary to gravitational and Casimir force experiments.In addition, one could reach photon-chameleon couplings which are beyond the sensitivity of common laser polarization experiments. We also sketch the idea of a Fabry-Perot cavity with chameleons which could increase the experimental sensitivity significantly. (orig.)
Alpenglow: A signature for chameleons in axionlike particle search experiments
International Nuclear Information System (INIS)
Ahlers, M.; Lindner, A.; Ringwald, A.; Schrempp, L.; Weniger, C.
2008-01-01
We point out that chameleon field theories might reveal themselves as an afterglow effect in axionlike particle search experiments due to chameleon-photon conversion in a magnetic field. We estimate the parameter space which is accessible by currently available technology and find that afterglow experiments could constrain this parameter space in a way complementary to gravitational and Casimir force experiments. In addition, one could reach photon-chameleon couplings which are beyond the sensitivity of common laser polarization experiments. We also sketch the idea of a Fabry-Perot cavity with chameleons which could increase the experimental sensitivity significantly
Aspects of quantum field theory in curved space-time
International Nuclear Information System (INIS)
Fulling, S.A.
1989-01-01
The theory of quantum fields on curved spacetimes has attracted great attention since the discovery, by Stephen Hawking, of black-hole evaporation. It remains an important subject for the understanding of such contemporary topics as inflationary cosmology, quantum gravity and superstring theory. The topics covered include normal-mode expansions for a general elliptic operator, Fock space, the Casimir effect, the Klein 'paradox', particle definition and particle creation in expanding universes, asymptotic expansion of Green's functions and heat kernels, and renormalization of the stress tensor. (author)
On the zero point energy of the electromagnetic field in the presence of material media
International Nuclear Information System (INIS)
Ferreira, L.A.
1980-12-01
The Van der Waals force between two semi-infinite material media separated by a piece of a third material is calculated. In this calculation, a generalization of some works on this theme is made, considering the radiation field delay effect, and impose no kind of electric and magnetic permeability dependence on the field frequency. The zero point energy of electromagnetic field in the presence of rectangular cavities with perfectly conducting walls (epsilon →i infinite) and/or infinitely permeable walls (μ→ infinite), is also calculated. Two kinds of regularization are made. In view of the results obtained modifications in the Casimir's model for the electron are suggested [pt
Cardy-Verlinde Formula and Its Self-Gravitational Corrections for Regular Black Holes
International Nuclear Information System (INIS)
Saleem, Rabia; Sharif, M.
2014-01-01
We check the consistency of the entropy of Bardeen and Ayón Beato-García-Bronnikov black holes with the entropy of particular conformal field theory via Cardy-Verlinde formula. We also compute the first-order semiclassical corrections of this formula due to self-gravitational effects by modifying pure extensive and Casimir energy in the context of Keski-Vakkuri, Kraus and Wilczek analysis. It is concluded that the correction term remains positive for both black holes, which leads to the violation of the holographic bound
Resonance of High Tc Superconducting Microstrip Patch in a Substrate-Superstrate Configuration
Directory of Open Access Journals (Sweden)
S. Benkouda
2014-02-01
Full Text Available The effect of a protecting dielectric superstrate on the resonance of a high Tc superconducting microstrip patch is investigated. The analysis approach is based on the spectral-domain method of moments in conjunction with the complex resistive boundary condition. The complex surface impedance of the superconducting thin film is determined using London’s equation and the two-fluid model of Gorter and Casimir. Numerical results show that the resonant frequency of the high Tc superconducting rectangular patch decreases monotonically with increasing superstrate thickness, the decrease being greater for high permittivity loading.
Graham, Peter W.; Kaplan, David E.; Rajendran, Surjeet
2018-02-01
We present a class of nonsingular, bouncing cosmologies that evade singularity theorems through the use of vorticity in compact extra dimensions. The vorticity combats the focusing of geodesics during the contracting phase. The construction requires fluids that violate the null energy condition (NEC) in the compact dimensions, where they can be provided by known stable NEC violating sources such as Casimir energy. The four dimensional effective theory contains an NEC violating fluid of Kaluza-Klein excitations of the higher dimensional metric. These spacetime metrics could potentially allow dynamical relaxation to solve the cosmological constant problem. These ideas can also be used to support traversable Lorentzian wormholes.
Eternal and evanescent black holes and accelerating mirror analogs
Good, Michael R. R.; Linder, Eric V.
2018-03-01
The analogy between black hole radiation and accelerating mirror radiation (the dynamical Casimir effect) is particularly strong for mirror trajectories giving rise to a constant thermal flux of particles. We present new ways to achieve such thermal plateaus, and customize their finite, semi-infinite, and eternal presence, corresponding to forming/collapsing, complete-evaporation/remnants, and eternal black holes. We find simple expressions for the energy flux in terms of the mirror rapidity as a function of proper time and null time.
Galaxy rotations from quantised inertia and visible matter only
McCulloch, M. E.
2017-01-01
It is shown here that a model for inertial mass, called quantised inertia, or MiHsC (Modified inertia by a Hubble-scale Casimir effect) predicts the rotational acceleration of the 153 good quality galaxies in the SPARC dataset (2016 AJ 152 157), with a large range of scales and mass, from just their visible baryonic matter, the speed of light and the co-moving diameter of the observable universe. No dark matter is needed. The performance of quantised inertia is comparable to that of MoND, yet...
Effect of the Gribov horizon on the Polyakov loop and vice versa
Energy Technology Data Exchange (ETDEWEB)
Canfora, F.E. [Centro de Estudios Cientificos (CECS), Valdivia (Chile); Dudal, D. [KU Leuven Campus Kortrijk, KULAK, Department of Physics, Kortrijk (Belgium); Ghent University, Department of Physics and Astronomy, Gent (Belgium); Justo, I.F. [Ghent University, Department of Physics and Astronomy, Gent (Belgium); UERJ, Universidade do Estado do Rio de Janeiro, Departamento de Fisica Teorica, Instituto de Fisica, Maracana, Rio de Janeiro (Brazil); Pais, P. [Centro de Estudios Cientificos (CECS), Valdivia (Chile); Universite Libre de Bruxelles and International Solvay Institutes, Physique Theorique et Mathematique, Brussels (Belgium); Rosa, L. [Universita di Napoli Federico II, Dipartimento di Fisica, Monte S. Angelo (Italy); INFN, Sezione di Napoli, Monte S. Angelo (Italy); Vercauteren, D. [Duy Tan University, Institute of Research and Development, Da Nang (Viet Nam)
2015-07-15
We consider finite-temperature SU(2) gauge theory in the continuum formulation, which necessitates the choice of a gauge fixing. Choosing the Landau gauge, the existing gauge copies are taken into account by means of the Gribov-Zwanziger quantization scheme, which entails the introduction of a dynamical mass scale (Gribov mass) directly influencing the Green functions of the theory. Here, we determine simultaneously the Polyakov loop (vacuum expectation value) and Gribov mass in terms of temperature, by minimizing the vacuum energy w.r.t. the Polyakov-loop parameter and solving the Gribov gap equation. Inspired by the Casimir energy-style of computation, we illustrate the usage of Zeta function regularization in finite-temperature calculations. Our main result is that the Gribov mass directly feels the deconfinement transition, visible from a cusp occurring at the same temperature where the Polyakov loop becomes nonzero. In this exploratory work we mainly restrict ourselves to the original Gribov-Zwanziger quantization procedure in order to illustrate the approach and the potential direct link between the vacuum structure of the theory (dynamical mass scales) and (de)confinement. We also present a first look at the critical temperature obtained from the refined Gribov-Zwanziger approach. Finally, a particular problem for the pressure at low temperatures is reported. (orig.)
International Nuclear Information System (INIS)
Mahieu, L.
1998-01-01
The main objectives of research in the field of health effects at the Belgian Nuclear Research Centre SCK-CEN are: (1) to study cancer mortality and morbidity in nuclear workers in Belgium; (2) to document the feasibility of retrospective cohort studies in Belgium; (3) to participate in the IARC study; (4) to elucidate the mechanisms of the effects of ionizing radiation on the mammalian embryo during the early phases of its development; (5) to assess the genetic risks of material exposure to ionizing radiation; (6) to elucidate the cellular mechanisms leading to brain damage after prenatal irradiation; (7) to advise authorities and to provide the general population with adequate information concerning the health risk arising from radiation exposure. Progress and major achievements in these topical areas for 1997 are reported
Energy Technology Data Exchange (ETDEWEB)
Mahieu, L
1998-07-01
The main objectives of research in the field of health effects at the Belgian Nuclear Research Centre SCK-CEN are: (1) to study cancer mortality and morbidity in nuclear workers in Belgium; (2) to document the feasibility of retrospective cohort studies in Belgium; (3) to participate in the IARC study; (4) to elucidate the mechanisms of the effects of ionizing radiation on the mammalian embryo during the early phases of its development; (5) to assess the genetic risks of material exposure to ionizing radiation; (6) to elucidate the cellular mechanisms leading to brain damage after prenatal irradiation; (7) to advise authorities and to provide the general population with adequate information concerning the health risk arising from radiation exposure. Progress and major achievements in these topical areas for 1997 are reported.
Directory of Open Access Journals (Sweden)
Beverly A. King Miller
2015-09-01
Full Text Available This article focuses on the educational strategies that can be used to support female students of African descent in their persistence in science, technology, engineering, and mathematics (STEM education and careers. STEM careers have historically been White male and White female dominated, which has yielded an underrepresentation of those of African descent. Drawing from a grounded qualitative case study, the data used for this article share the responses of Afro-Caribbean females in STEM who have immigrated to the United States from the country of Panama. As Latinas, they are representative of the changing face in the American educational system—bilingual, multicultural, and of African descent. The strategies offered reflect their own teaching practices, their former teachers, or experiences with their children’s teachers. What emerged were descriptions of four strategies and behaviors of effective teachers that align with Ladson-Billings’s culturally relevant pedagogy and Gay’s culturally responsive teaching. Included in the findings are the high standards and expectations embodied by effective teachers that serve to positively inspire their students. Culturally responsive teachers create an atmosphere of learning that supports academic success, conveying their belief in their students’ ability based upon their own reflectivity. As the U.S. educational system continues to become multilingual and multicultural, there is need for strategies for the successful inclusion and progression of students in STEM educational pathways and careers. This will occur as teachers challenge themselves to be the agents of change in the lives of their students.
Effective Protection or Effective Combat
DEFF Research Database (Denmark)
Lemberg-Pedersen, Martin
2016-01-01
and multilocal character of European border control. This is then elaborated via a critical gaze at several attempts to defi ne how European states have attempted to externalize migration control to other countries in terms of supranational policy drives, ripple and mimicry effects. This then facilitates a more...... nuanced understanding of externalization. Since border control reterritorializes geographic spaces according to the mobility of the people through them, it follows that the EU’s border control, and with it also aspects of the union’s asylum policy, have both biopolitical and geopolitical implications...
Porche, D J
1998-01-01
People who choose not to abstain from sexual intercourse can use barrier contraceptive methods, such as condoms, to reduce their risk of contracting HIV and other sexually transmitted diseases (STDs). Health care providers who provide safer sex education and counseling should provide information on condoms as a way of reducing the risk of HIV/STD transmission. Since latex condoms are regulated by the US Food and Drug Administration (FDA) as medical devices, FDA regulations govern latex condom manufacturing and testing in accordance with stringent national standards. The FDA randomly tests imported condoms according to the same stringent quality control standards as US-produced condoms. Condom effectiveness, however, depends upon their correct and consistent use during every sexual act. Relevant data and guidelines are presented on the correct use of male latex and female polyurethane condoms. Both male latex and female polyurethane condoms can prevent the transmission of HIV and other STDs.
International Nuclear Information System (INIS)
Collings, E.W.
1986-01-01
An important cause of deterioration in superconducting magnets intended for high-energy physics and fusion-reactor applications is radiation damage. The present chapter deals chiefly with the effects of electron, proton, gamma and neutron irradiation on the properties of stabilized Ti-Nb-base composite superconductors. The authors examine the particle-accelerator environment, electron irradiation of Ti-Nb superconductor, proton irradiation of Ti-Nb superconductor and its stabilizer, and deuteron irradiation of Ti-Nb superconductor. A section discussing the fusion reactor environment in general is presented, and the two principal classes of fusion reactor based on the magnetic-confinement concept, namely the tokamak and the mirrormachine are examined. Also discussed is neutron irradiation of Cu/TiNb composite superconductors and critical current density of neutronirradiated Ti-Nb. Finally, radiation damage to stabilizer and insulating materials is described
International Nuclear Information System (INIS)
Mahieu, L.
1998-01-01
The objectives of the research in the field of epidemiology , performed at the Belgian Nuclear Research Centre SCK-CEN are (1) to study cancer mortality and morbidity in nuclear workers in Belgium; (2) to document the feasibility of retrospective cohort studies in Belgium; (3) to participate in the IARC study. For radiobiology, the main objectives are: (1) to elucidate the mechanisms of the effects of ionizing radiation on the mammalian embryo during the early phase of its development, (2) to assess the genetic risks of maternal exposure to ionizing radiation, (3) to elucidate the mechanisms by which damage to the brain and mental retardation are caused in man after prenatal irradiation. The main achievements in these domains for 1997 are presented
International Nuclear Information System (INIS)
Maxon, H.; Thomas, S.; Buncher, C.; Book, S.; Hertzberg, V.
1985-01-01
Risk coefficients for thyroid disorders have been developed for both 131 I and external x or gamma low-LET radiation. A linear, no-threshold model has been used for thyroid neoplasms. A linear, threshold model has been used for other thyroid disorders. Improvements since the Reactor Safety Study were made possible by relevant new animal and human data. Major changes are as follows. Animal data are used to supplement the human experience where necessary. A specific risk estimate model is used for thyroid neoplasms, which accounts for observed effects of gender and age at exposure on risk. For thyroid cancer, the basis of the risk coefficients is the experience of North Americans following x-irradiation for benign disease in childhood. This recognizes possible differences in susceptibility in people of different heritage. A minimum induction period for thyroid neoplasms following irradiation is used to define periods at risk. An upper bound risk coefficient for cancer induction following exposure to 131 I is based on human experience at relatively low dose exposures. While the overall lifetime risks of death due to thyroid cancer are consistent with projections by the ICRP, BEIR III, and UNSCEAR Reports, the current model permits greater flexibility in determining risk for population subgroups. 88 references, 8 tables
A geometric theory of selective decay with applications in MHD
International Nuclear Information System (INIS)
Gay-Balmaz, François; Holm, Darryl D
2014-01-01
Modifications of the equations of ideal fluid dynamics with advected quantities are introduced that allow selective decay of either the energy h or the Casimir quantities C in the Lie–Poisson (LP) formulation. The dissipated quantity (energy or Casimir, respectively) is shown to decrease in time until the modified system reaches an equilibrium state consistent with ideal energy-Casimir equilibria, namely δ(h + C) = 0. The result holds for LP equations in general, independently of the Lie algebra and the choice of Casimir. This selective decay process is illustrated with a number of examples in 2D and 3D magnetohydrodynamics. (paper)
... Media ASA Member Toolkit Anesthesia 101 Effects of Anesthesia Explore this page: Effects of Anesthesia How can ... of anesthesia and their side effects? Effects of Anesthesia If you’re having surgery, you most likely ...
The Trace Anomaly and Dynamical Vacuum Energy in Cosmology
Mottola, Emil
2010-01-01
The trace anomaly of conformal matter implies the existence of massless scalar poles in physical amplitudes involving the stress-energy tensor. These poles may be described by a local effective action with massless scalar fields, which couple to classical sources, contribute to gravitational scattering processes, and can have long range gravitational effects at macroscopic scales. In an effective field theory approach, the effective action of the anomaly is an infrared relevant term that should be added to the Einstein-Hilbert action of classical General Relativity to take account of macroscopic quantum effects. The additional scalar degrees of freedom contained in this effective action may be understood as responsible for both the Casimir effect in flat spacetime and large quantum backreaction effects at the horizon scale of cosmological spacetimes. These effects of the trace anomaly imply that the cosmological vacuum energy is dynamical, and its value depends on macroscopic boundary conditions at the cosmol...
Bulk renormalization and particle spectrum in codimension-two brane worlds
International Nuclear Information System (INIS)
Salvio, Alberto
2013-01-01
We study the Casimir energy due to bulk loops of matter fields in codimension-two brane worlds and discuss how effective field theory methods allow us to use this result to renormalize the bulk and brane operators. In the calculation we explicitly sum over the Kaluza-Klein (KK) states with a new convenient method, which is based on a combined use of zeta function and dimensional regularization. Among the general class of models we consider we include a supersymmetric example, 6D gauged chiral supergravity. Although much of our discussion is more general, we treat in some detail a class of compactifications, where the extra dimensions parametrize a rugby ball shaped space with size stabilized by a bulk magnetic flux. The rugby ball geometry requires two branes, which can host the Standard Model fields and carry both tension and magnetic flux (of the bulk gauge field), the leading terms in a derivative expansion. The brane properties have an impact on the KK spectrum and therefore on the Casimir energy as well as on the renormalization of the brane operators. A very interesting feature is that when the two branes carry exactly the same amount of flux, one half of the bulk supersymmetries survives after the compactification, even if the brane tensions are large. We also discuss the implications of these calculations for the natural value of the cosmological constant when the bulk has two large extra dimensions and the bulk supersymmetry is partially preserved (or completely broken).
An inflationary cosmological model with induced gravity from higher dimensions
International Nuclear Information System (INIS)
Pollock, M.D.
1985-05-01
It is shown how dimensional reduction of a (4+N)-dimensional theory can lead to an effective four-dimensional, broken-symmetry theory of gravity, whose Lagrangian density is of the form L=(1/2)epsilonphi 2 R+(1/2)phisub(;k)phisup(;k)-V(phi), where R is the Ricci scalar, the field phi is the inverse of the radius function of the internal space, and the potential contains both a classical contribution and a Casimir energy -(1/4)lambdaprimephi 4 . For small phi, the Casimir energy dominates, and quantum corrections automatically generate a Coleman-Weinberg potential V(phi)=(1/4)lambdaphi 4 [ln(phi 2 /μ 2 )-(1/2)]+Λ-tilde. A generalized Rubakov-Shaposhnikov ansatz is made in the (4+N)-dimensional metric, by means of which the vacuum energy density can be made sufficiently small for compatibility with the cosmological microwave background radiation, for a given lambda. It turns out that epsilon=(2/3)(N+1) -1 (N-3) -1 . Cosmological inflation can be realized, provided that N > or approx. 13. But the Brans-Dicke parameter is ω=(4epsilon) -1 , and ω > or approx. 500 means that N > or approx. 40. (author)
Edery, Ariel; Graham, Noah; MacDonald, Ilana
2009-06-01
Under dimensional reduction, a system in D spacetime dimensions will not necessarily yield its D-1-dimensional analog version. Among other things, this result will depend on the boundary conditions and the dimension D of the system. We investigate this question for scalar and Abelian gauge fields under boundary conditions that obey the symmetries of the action. We apply our findings to the Casimir piston, an ideal system for detecting boundary effects. Our investigation is not limited to extra dimensions and we show that the original piston scenario proposed in 2004, a toy model involving a scalar field in 3D (2+1) dimensions, can be obtained via dimensional reduction from a more realistic 4D electromagnetic (EM) system. We show that for perfect conductor conditions, a D-dimensional EM field reduces to a D-1 scalar field and not its lower-dimensional version. For Dirichlet boundary conditions, no theory is recovered under dimensional reduction and the Casimir pressure goes to zero in any dimension. This “zero Dirichlet” result is useful for understanding the EM case. We then identify two special systems where the lower-dimensional version is recovered in any dimension: systems with perfect magnetic conductor (PMC) and Neumann boundary conditions. We show that these two boundary conditions can be obtained from a variational procedure in which the action vanishes outside the bounded region. The fields are free to vary on the surface and have zero modes, which survive after dimensional reduction.
Pejhan, Hamed; Rahbardehghan, Surena
2016-04-01
Respecting that any consistent quantum field theory in curved space-time must include black hole radiation, in this paper, we examine the Krein-Gupta-Bleuler (KGB) formalism as an inevitable quantization scheme in order to follow the guideline of the covariance of minimally coupled massless scalar field and linear gravity on de Sitter (dS) background in the sense of Wightman-Gärding approach, by investigating thermodynamical aspects of black holes. The formalism is interestingly free of pathological large distance behavior. In this construction, also, no infinite term appears in the calculation of expectation values of the energy-momentum tensor (we have an automatic and covariant renormalization) which results in the vacuum energy of the free field to vanish. However, the existence of an effective potential barrier, intrinsically created by black holes gravitational field, gives a Casimir-type contribution to the vacuum expectation value of the energy-momentum tensor. On this basis, by evaluating the Casimir energy-momentum tensor for a conformally coupled massless scalar field in the vicinity of a nonrotating black hole event horizon through the KGB quantization, in this work, we explicitly prove that the hole produces black-body radiation which its temperature exactly coincides with the result obtained by Hawking for black hole radiation.
Van der Waals interactions: Corrections from radiation in fluids
Directory of Open Access Journals (Sweden)
Magnus H. Waage
2013-02-01
Full Text Available We consider induced van der Waals interactions with corrections due to radiation in fluids consisting of polarizable hard spheres. The fluctuating polarizations are quantized while the positions of particles are treated classically. First the well known result for the induced Casimir free energy for a pair of particles is used to establish the resulting free energy at low density. The Casimir interaction includes the full effect of the quantized radiating electromagnetic field. Then the situation with electrostatic dipole-dipole interactions is considered for general density. For this situation the induced interactions are the van der Waals interactions, and we evaluate numerically the free energy based upon analytic results obtained earlier. These analytic results were obtained by extending methods of classical statistical mechanics to the path integral of quantum mechanics. We have realized that these methods can be extended to time-dependent interactions too. Thus we here also make the extension to the radiating dipole-dipole interaction between pairs of particles to obtain explicit results for more arbitrary fluid densities, and radiation corrections to the induced free energy are found both analytically and numerically.
Colossal magnetodielectric effect caused by magnetoelectric effect ...
Indian Academy of Sciences (India)
The colossal magnetodielectric effect is reported in Pb(Zr,Ti)O3/Terfenol-D laminate composite under low magnetic field. When the composite is placed in an external a.c. magnetic field, magnetoelectric effect is produced, as a result, the dielectric properties of the Pb(Zr,Ti)O3 is changed, i.e. magnetodielectric effect. Both the ...
Theory of Effectiveness Measurement
National Research Council Canada - National Science Library
Bullock, Richard K
2006-01-01
.... Currently, however, there is no formal foundation for formulating effectiveness measures. This research presents a new framework for effectiveness measurement from both a theoretical and practical view...
Yilbas, B. S.; Ali, H.
2016-08-01
Short-pulse laser heating of aluminum and silicon thin films pair with presence of a minute vacuum gap in between them is considered and energy transfer across the thin films pair is predicted. The frequency dependent Boltzmann equation is used to predict the phonon intensity distribution along the films pair for three cycles of the repetitive short-pulse laser irradiation on the aluminum film surface. Since the gap size considered is within the Casimir limit, thermal radiation and ballistic phonon contributions to energy transfer across the vacuum gap is incorporated. The laser irradiated field is formulated in line with the Lambert's Beer law and it is considered as the volumetric source in the governing equations of energy transport. In order to assess the phonon intensity distribution in the films pair, equivalent equilibrium temperature is introduced. It is demonstrated that thermal separation of electron and lattice sub-systems in the aluminum film, due to the short-pulse laser irradiation, takes place and electron temperature remains high in the aluminum film while equivalent equilibrium temperature for phonons decays sharply in the close region of the aluminum film interface. This behavior is attributed to the phonon boundary scattering at the interface and the ballistic phonon transfer to the silicon film across the vacuum gap. Energy transfer due to the ballistic phonon contribution is significantly higher than that of the thermal radiation across the vacuum gap.
International Nuclear Information System (INIS)
Tadmor, J.
1984-05-01
A sound evaluation of the consequences of releases of radioactivity into the environment, especially of those large amounts, and of the effectiveness of different protective measures, requires thorough concern of the various aspects of the radiological effects. The effects of ionizing radiation were reviewed according to the following characterization: Affected subject (somatic, genetic and psychological effects); Duration of irradiation (acute and chronic irradiation); Latent period (early and late effects); Dose-effect relationship (stochastic and non-stochastic effects); Population affected (e.g. children, pregnant women). In addition to the lethal effects which are generally considered extensively in all the evaluations of the consequences of radioactivity releases, such effects as early symptoms and morbidity are emphasized in this review. The dependence of the effects on dose rates, repair mechanism and medical treatment is discussed, and the uncertainties involved with their evaluation is highlighted. The differences between QF (quality factor) and RBE (relative biological effectiveness) of different radiation sources are interpreted. Synergystic effects and the effectiveness of various means of medication are discussed. It is suggested that all radiological effects, including those resulting from relatively low radiation doses, e.g. foetus deformations, fertility impairment, prodomal - leading to psychological effects, should be considered within the evaluation of the consequences of radioactivity releases and of the effectiveness of protective measures. Limits of the repair factors to be considered within the evaluation of the effects of chronic exposures are proposed
Kelley, Ken; Preacher, Kristopher J.
2012-01-01
The call for researchers to report and interpret effect sizes and their corresponding confidence intervals has never been stronger. However, there is confusion in the literature on the definition of effect size, and consequently the term is used inconsistently. We propose a definition for effect size, discuss 3 facets of effect size (dimension,…
Biological effects of radiation
International Nuclear Information System (INIS)
2013-01-01
This fourth chapter presents: cell structure and metabolism; radiation interaction with biological tissues; steps of the production of biological effect of radiation; radiosensitivity of tissues; classification of biological effects; reversibility, transmissivity and influence factors; pre-natal biological effects; biological effects in therapy and syndrome of acute irradiation
Colossal magnetodielectric effect caused by magnetoelectric effect ...
Indian Academy of Sciences (India)
-D laminate composite under low magnetic field. When the composite is placed in an external a.c. magnetic field, magnetoelectric effect is produced, as a result, the dielectric properties of the Pb(Zr,Ti)O3 is changed, i.e. magnetodielectric effect ...
Colossal magnetodielectric effect caused by magnetoelectric effect ...
Indian Academy of Sciences (India)
Keywords. Composite materials; electrical properties; magnetodielectric effect; magnetoelectric effect. 1. Introduction. Recently, multiferroic materials have attracted much interest for their coexistence of ferroelectricity, ferromagnetism and ferroelasticity (Kimura et al 2003; Wang et al 2003; Hur et al. 2004; Spaldin and Fiebig ...
Cholak, Peter; McCoy, Charlie
2014-01-01
Assuming the obvious definitions (see paper) we show the a decidable model that is effectively prime is also effectively atomic. This implies that two effectively prime (decidable) models are computably isomorphic. This is in contrast to the theorem that there are two atomic decidable models which are not computably isomorphic. The implications of this work in reverse mathematics is that "effectively prime implies effectively atomic" holds in topped models. But due to an observation of David ...
How effective is the effective potential?
International Nuclear Information System (INIS)
Dodelson, S.; Gradwohl, B.A.
1993-01-01
Motivated by bubble nucleation in first order phase transitions, we question the validity of the effective potential for inhomogeneous configurations. In an attempt to get some insight into the importance of derivative terms, we analyze a simple model, a kink in 1+1 dimensions and zero temperature. We evaluate the energy shift from the quantum fluctuations about the non-uniform background (i.e. the effective action) and compare it to the energy from the effective potential. Our results clearly show that for inhomogeneous configurations it may be inadequate to omit derivative terms and confine oneself to the effective potential. We then couple the kink field to an additional scalar field and perform the same comparison. The addition of the second field allows us to vary the mass of the fluctuations and their coupling to the underlying kink. If the mass of the second field is large, it does not feel the inhomogeneities in the kink field and consequently does not give rise to important derivative corrections in the effective action. In contrast, if the mass is small, derivative terms are significant and the effective potential fails. In the latter regime we can, however, rely on the Born approximation to calculate the effective action. (orig.)
A complete analogue of Hardy's theorem on SL2 (R) and ...
Indian Academy of Sciences (India)
We also consider the `heat equation' of the Casimir operator, which plays the role of the Laplacian for the group. We show that despite the structural difference of the Casimir with the Laplacian on R n or the Laplace-Beltrami operator on the Riemannian symmetric spaces, it is possible to have a heat kernel. This heat kernel ...
Zö
2011-01-01
The rapid development in various fields of Digital Audio Effects, or DAFX, has led to new algorithms and this second edition of the popular book, DAFX: Digital Audio Effects has been updated throughout to reflect progress in the field. It maintains a unique approach to DAFX with a lecture-style introduction into the basics of effect processing. Each effect description begins with the presentation of the physical and acoustical phenomena, an explanation of the signal processing techniques to achieve the effect, followed by a discussion of musical applications and the control of effect parameter
Biological effects of hyperthermia
International Nuclear Information System (INIS)
Okumura, Hiroshi
1980-01-01
Biological effects of hyperthermia and application of hyperthermia to cancer therapy were outlined. As to independent effects of hyperthermia, heat sensitivity of cancer cells, targets of hyperthermia, thermal tolerance of cancer cells, effects of pH on hyperthermic cell survival, effects of hyperthermia on normal tissues, and possibility of clinical application of hyperthermia were described. Combined effect of hyperthermia and x-irradiation to enhance radiosensitivity of cancer cells, its mechanism, effects of oxygen on cancer cells treated with hyperthermia and irradiation, and therapeutic ratio of combined hyperthermia and irradiation were also described. Finally, sensitizers were mentioned. (Tsunoda, M.)
Modeling quantization effects in field effect transistors
Troger, C
2001-01-01
Numerical simulation in the field of semiconductor device development advanced to a valuable, cost-effective and flexible facility. The most widely used simulators are based on classical models, as they need to satisfy time and memory constraints. To improve the performance of field effect transistors such as MOSFETs and HEMTs these devices are continuously scaled down in their dimensions. Consequently the characteristics of such devices are getting more and more determined by quantum mechanical effects arising from strong transversal fields in the channel. In this work an approach based on a two-dimensional electron gas is used to describe the confinement of the carriers. Quantization is considered in one direction only. For the derivation of a one-dimensional Schroedinger equation in the effective mass framework a non-parabolic correction for the energy dispersion due to Kane is included. For each subband a non-parabolic dispersion relation characterized by subband masses and subband non-parabolicity coeffi...
... Guidance and Trainings Webinars Data and Tools Publications Climate Effects on Health Recommend on Facebook Tweet Share ... effects has been excerpted from the Third National Climate Assessment’s Health Chapter . Additional information regarding the health ...
Multipollutant health effect simulations
U.S. Environmental Protection Agency — Resulting betas (health effects) from a variety of copollutant epidemiologic models used to analyze the impact of exposure measurement error on health effect...
Skills for Effective Consultation.
Dustin, Dick; Ehly, Stewart
1984-01-01
Discusses counselor skills that promote effective consultation. Reviews research on effective school consultation and presents a five-stage model which involves phasing in, problem identification, implementation, evaluation, and termination. Provides recommendations for the process and products of consultation. (JAC)
Characteristics of Effective Argumentation.
Frana, Adrian W.
1989-01-01
Examines how the 1988 Presidential Debates provide a resource for effective instruction in public argument. Provides several examples of effective (and ineffective) argumentative speaking taken from the debates. (MM)
... to fully work. You might feel some side effects of your medication before your feel the benefits – ... as sleepiness, anxiety or headache) is a side effect or a symptom of your illness. Many side ...
... cancer care is relieving side effects, called symptom management, palliative care, or supportive care. It is important ... treat them. To learn about the symptoms and management of the long-term side effects of cancer ...
Leadership Effectiveness and Gender
National Research Council Canada - National Science Library
Gedney, Christine
1999-01-01
This research paper on the subject of Leadership Effectiveness and Gender attempts to conduct a focused amount of research to answer the question about the correlation between gender and leadership effectiveness...
DEFF Research Database (Denmark)
Wahlgren, Bjarne; Larsen, Lea Lund
2010-01-01
The article gives a short overview over existing knowledge concerning the effect of teacher training in relation to adult learning. It presents a research design for measuring the effect of teacher traning.......The article gives a short overview over existing knowledge concerning the effect of teacher training in relation to adult learning. It presents a research design for measuring the effect of teacher traning....
Special Effects Activity Guide.
Boxer, Jennifer; Valenta, Carol
This guide accompanies "Special Effects," a 40-minute IMAX film and "Special Effects II", a multimedia, interactive traveling exhibit designed by the California Museum of Science and Industry. The exhibit focuses on the underlying scientific and technical processes of special effects from the earliest motion picture to state-of-the-art digital…
DEFF Research Database (Denmark)
Keiding, Hans; Peleg, Bezalel
2006-01-01
effectivity rule is regular if it is the effectivity rule of some regular binary SCR. We characterize completely the family of regular binary effectivity rules. Quite surprisingly, intrinsically defined von Neumann-Morgenstern solutions play an important role in this characterization...
Magnetic effects in electrochemistry
Directory of Open Access Journals (Sweden)
NEBOJSA D. NIKOLIC
2005-05-01
Full Text Available The effect of imposed magnetic fields onto the electrodeposition of magnetic (nickel and non – magnetic (copper metals was analysed. Also, magnetic properties of electrochemically obtained nanocontacts were examined. An effort to establish a possible correlation between the morphologies of the nanocontacts and the effect of the very large ballistic magnetoresistance (BMR effect was made.
Phylogenetic effective sample size.
Bartoszek, Krzysztof
2016-10-21
In this paper I address the question-how large is a phylogenetic sample? I propose a definition of a phylogenetic effective sample size for Brownian motion and Ornstein-Uhlenbeck processes-the regression effective sample size. I discuss how mutual information can be used to define an effective sample size in the non-normal process case and compare these two definitions to an already present concept of effective sample size (the mean effective sample size). Through a simulation study I find that the AICc is robust if one corrects for the number of species or effective number of species. Lastly I discuss how the concept of the phylogenetic effective sample size can be useful for biodiversity quantification, identification of interesting clades and deciding on the importance of phylogenetic correlations. Copyright © 2016 Elsevier Ltd. All rights reserved.
DEFF Research Database (Denmark)
Landex, Alex
2012-01-01
. Therefore, sections 3 and 4 describe the network effects for passengers and how they can be measured using passenger delay models. Before the concluding remarks in section 6, section 5 discusses how the operation can be improved by examining network effects in the planning process. © 2012 WIT Press....... each other everywhere in the network. First this paper describes network effects in general (section 1). In section 2 the network effects for trains and how they can be measured by scheduled waiting time is described. When the trains are affected by network effects the passengers are also affected......Railway operation is often affected by network effects as a change in one part of the network can influence other parts of the network. Network effects occur because the train runs may be quite long and since the railway system has a high degree of interdependencies as trains cannot cross/overtake...
International Nuclear Information System (INIS)
Gomes, R.A.
1976-01-01
The stages of processes leading to radiation damage are studied, as well as, the direct and indirect mechanics of its production. The radiation effects on nucleic acid and protein macro moleculas are treated. The physical and chemical factors that modify radiosensibility are analysed, in particular the oxygen effects, the sensibilization by analogues of nitrogen bases, post-effects, chemical protection and inherent cell factors. Consideration is given to restoration processes by excision of injured fragments, the bloching of the excision restoration processes, the restoration of lesions caused by ionizing radiations and to the restoration by genetic recombination. Referring to somatic effects of radiation, the early ones and the acute syndrome of radiation are discussed. The difference of radiosensibility observed in mammalian cells and main observable alterations in tissues and organs are commented. Referring to delayed radiation effects, carcinogeneses, alterations of life span, effects on growth and development, as well as localized effects, are also discussed [pt
Modeling the size dependent pull-in instability of beam-type NEMS using strain gradient theory
Directory of Open Access Journals (Sweden)
Ali Koochi
Full Text Available It is well recognized that size dependency of materials characteristics, i.e. size-effect, often plays a significant role in the performance of nano-structures. Herein, strain gradient continuum theory is employed to investigate the size dependent pull-in instability of beam-type nano-electromechanical systems (NEMS. Two most common types of NEMS i.e. nano-bridge and nano-cantilever are considered. Effects of electrostatic field and dispersion forces i.e. Casimir and van der Waals (vdW attractions have been considered in the nonlinear governing equations of the systems. Two different solution methods including numerical and Rayleigh-Ritz have been employed to solve the constitutive differential equations of the system. Effect of dispersion forces, the size dependency and the importance of coupling between them on the instability performance are discussed.
Quantum field theory the why, what and how
Padmanabhan, Thanu
2016-01-01
This book describes, in clear terms, the Why, What and the How of Quantum Field Theory. The raison d'etre of QFT is explained by starting from the dynamics of a relativistic particle and demonstrating how it leads to the notion of quantum fields. Non-perturbative aspects and the Wilsonian interpretation of field theory are emphasized right from the start. Several interesting topics such as the Schwinger effect, Davies-Unruh effect, Casimir effect and spontaneous symmetry breaking introduce the reader to the elegance and breadth of applicability of field theoretical concepts. Complementing the conceptual aspects, the book also develops all the relevant mathematical techniques in detail, leading e.g., to the computation of anomalous magnetic moment of the electron and the two-loop renormalisation of the self-interacting scalar field. It contains nearly a hundred problems, of varying degrees of difficulty, making it suitable for both self-study and classroom use.
EFFECTS OF EFFECTS OF PARTICLE SIZE DISTRIBUTION ...
African Journals Online (AJOL)
eobe
Bioremediation has been proven to be the most effective method of cleaning up oil contaminated soils through the application of nutrients and microor the application of nutrients and microorganism. Hence, this ganism. Hence, this ganism. Hence, this research presents the research presents the research presents the ...
International Nuclear Information System (INIS)
DeWitt, B.
1987-01-01
The concept of the effective action in quantum field theory was introduced into physics by Julian Schwinger in 1954. The effective action summarizes, in a single functional, all the quantum properties of the fields under consideration. The functional derivative of the effective action yields the effective field equations, which replace the classical field equations as descriptors of the dynamical behavior of quantized fields. Solutions of these equations are 'in-out' matrix elements of the field operators and, when substituted back into the effective action itself, yield logarithms of the corresponding 'in-out' amplitudes. The classical field equations are gauge covariant, a fact that derives from the gauge invariance of the classical action. One has learned how to construct effective actions that are similarly gauge invariant (in each order of perturbation theory) and that yield effective field equations having the covariance properties of their classical analogs. Despite this advance, problems remain, stemming from the fact that there is not one but an infinite number of gauge invariant effective actions, one for every background-covariant choice of supplementary conditions and ghost fields. Vilkovisky (1984) has argued persuasively that by requiring additionally that the effective action be invariant under local invertible changes in the choice of basic field variables, one can construct a natural unique gauge invariant effective action. This lecture will examine Vilkovisky's ideas. 3 refs
The Aid Effectiveness Literature
DEFF Research Database (Denmark)
Doucouliagos, Hristos; Paldam, Martin
The AEL consists of empirical macro studies of the effects of development aid. At the end of 2004 it had reached 97 studies of three families, which we have summarized in one study each using meta-analysis. Studies of the effect on investments show that they rise by 1/3 of the aid – the rest...... is crowded out by a fall in savings. Studies of the effect on growth show an insignificant positive effect. Studies of the effect on growth, conditional on something else, have till now shown weak results. The Dutch Disease effect of aid has been ignored. The best aggregate estimate is that since its start...... in the early 1960s aid has increased the standard of living in the poor countries by 20%....
The Hubble effective potential
Energy Technology Data Exchange (ETDEWEB)
Janssen, T.M.; Miao, S.P.; Prokopec, T. [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, Postbus 80.195, 3508 TD Utrecht (Netherlands); Woodard, R.P., E-mail: T.M.Janssen@uu.nl, E-mail: S.Miao@uu.nl, E-mail: T.Prokopec@uu.nl, E-mail: woodard@phys.ufl.edu [Department of Physics, University of Florida, Gainesville, FL 32611 (United States)
2009-05-15
We generalize the effective potential to scalar field configurations which are proportional to the Hubble parameter of a homogeneous and isotropic background geometry. This may be useful in situations for which curvature effects are significant. We evaluate the one loop contribution to the Hubble Effective Potential for a massless scalar with arbitrary conformal and quartic couplings, on a background for which the deceleration parameter is constant. Among other things, we find that inflationary particle production leads to symmetry restoration at late times.
Leadership Effectiveness and Gender
National Research Council Canada - National Science Library
Gedney, Christine
1999-01-01
.... It specifically looks at the current definitions of leadership and looks at some historical background information relating to the more common theories that relate to leadership and effectiveness...
Impedance and Collective Effects
Metral, E; Rumolo, R; Herr, W
2013-01-01
This document is part of Subvolume C 'Accelerators and Colliders' of Volume 21 'Elementary Particles' of Landolt-Börnstein - Group I 'Elementary Particles, Nuclei and Atoms'. It contains the Chapter '4 Impedance and Collective Effects' with the content: 4 Impedance and Collective Effects Introduction 4.1 Space Charge 4.2 Wake Fields and Impedances 4.3 Coherent Instabilities 4.4 Landau Damping 4.5 Two-Stream Effects (Electron Cloud and Ions) 4.6 Beam-Beam Effects 4.7 Numerical Modelling
Secondary hydrogen isotope effects
International Nuclear Information System (INIS)
Melander, L.; Sonders, U.
1983-01-01
Secondary isotope effects can be produced by isotopes of elements heavier than hydrogen, but secondary isotope effects of hydrogen are of greater interest, because they are larger and can be measured easier. Such aspects of the problem as solvolytic reactions (in the case of α-position and β-position in organic compounds), reactions of compounds with deuterium remoted from reaction centre, with deuterium in nonsaturated compounds, participation of neighbouring groups in the reaction, are considered. Besides, steric isotope effects and inductive isotope effects are considered
Effects of Leadership Roles on Team Effectiveness
Ethem Duygulu; Nurcan Ciraklar
2009-01-01
In this study we aim to explain the patterns of leadership roles for team effectiveness in non profit organizations compared to economic organizations. For this purpose, we studied three successful organization types, i.e the amateur sports clubs (football, basketball), theater companies and, regional folk groups. Our basic hypothesis is that the relationship between the type of organization (specially teams) and the role of leadership is not random. Therefore, we believe that an empirical ap...
Stiff self-interacting strings at high temperature QCD
S Bakry, A.; Chen, X.; Deliyergiyev, M.; Galal, A.; Khalaf, A.; M Pengming, P.
2018-03-01
We investigate the implications of Nambu-Goto (NG), Lüscher Weisz (LW) and Polyakov-Kleinert (PK) effective string actions for the Casimir energy and the width of the quantum delocalization of the string in 4-dim pure SU(3) Yang-Mills lattice gauge theory. At a temperature closer to the critical point T/Tc=0.9, we found that the next to leading-order (NLO) contributions from the expansion of the NG string in addition to the boundary terms in LW action to decrease the deviations from the lattice data in the intermediate distance scales for both the quark-antiquark QQ̅ potential and broadening of the color tube compared to the free string approximation. We conjecture possible stiffness of the QCD string through studying the effects of extrinsic curvature term in PK action and find a good fitting behavior for the lattice Monte-Carlo data at both long and intermediate quark separations regions.
Non-equilibrium concentration fluctuations in binary liquids with realistic boundary conditions.
Ortiz de Zárate, J M; Kirkpatrick, T R; Sengers, J V
2015-09-01
Because of the spatially long-ranged nature of spontaneous fluctuations in thermal non-equilibrium systems, they are affected by boundary conditions for the fluctuating hydrodynamic variables. In this paper we consider a liquid mixture between two rigid and impervious plates with a stationary concentration gradient resulting from a temperature gradient through the Soret effect. For liquid mixtures with large Lewis and Schmidt numbers, we are able to obtain explicit analytical expressions for the intensity of the non-equilibrium concentration fluctuations as a function of the frequency ω and the wave number q of the fluctuations. In addition we elucidate the spatial dependence of the intensity of the non-equilibrium fluctuations responsible for a non-equilibrium Casimir effect.
International Nuclear Information System (INIS)
Nelson, Ann E.; Walsh, Jonathan
2008-01-01
We show that for a force mediated by a vector particle coupled to a conserved U(1) charge, the apparent range and strength can depend on the size and density of the source, and the proximity to other sources. This chameleon effect is due to screening from a light charged scalar. Such screening can weaken astrophysical constraints on new gauge bosons. As an example we consider the constraints on chameleonic gauged B-L. We show that although Casimir measurements greatly constrain any B-L force much stronger than gravity with range longer than 0.1 μm, there remains an experimental window for a long-range chameleonic B-L force. Such a force could be much stronger than gravity, and long or infinite range in vacuum, but have an effective range near the surface of the earth which is less than a micron.
Extended inflation from higher-dimensional theories
International Nuclear Information System (INIS)
Holman, R.; Kolb, E.W.; Vadas, S.L.; Wang, Y.
1991-01-01
We consider the possibility that higher-dimensional theories may, upon reduction to four dimensions, allow extended inflation to occur. We analyze two separate models. One is a very simple toy model consisting of higher-dimensional gravity coupled to a scalar field whose potential allows for a first-order phase transition. The other is a more sophisticated model incorporating the effects of nontrivial field configurations (monopole, Casimir, and fermion bilinear condensate effects) that yield a nontrivial potential for the radius of the internal space. We find that extended inflation does not occur in these models. We also find that the bubble nucleation rate in these theories is time dependent unlike the case in the original version of extended inflation
Extended inflation from higher dimensional theories
International Nuclear Information System (INIS)
Holman, R.; Kolb, E.W.; Vadas, S.L.; Wang, Yun.
1990-04-01
The possibility is considered that higher dimensional theories may, upon reduction to four dimensions, allow extended inflation to occur. Two separate models are analayzed. One is a very simple toy model consisting of higher dimensional gravity coupled to a scalar field whose potential allows for a first-order phase transition. The other is a more sophisticated model incorporating the effects of non-trivial field configurations (monopole, Casimir, and fermion bilinear condensate effects) that yield a non-trivial potential for the radius of the internal space. It was found that extended inflation does not occur in these models. It was also found that the bubble nucleation rate in these theories is time dependent unlike the case in the original version of extended inflation
Antimatter Production at a Potential Boundary
LaPointe, Michael R.; Reddy, Dhanireddy (Technical Monitor)
2001-01-01
Current antiproton production techniques rely on high-energy collisions between beam particles and target nuclei to produce particle and antiparticle pairs, but inherently low production and capture efficiencies render these techniques impractical for the cost-effective production of antimatter for space propulsion and other commercial applications. Based on Dirac's theory of the vacuum field, a new antimatter production concept is proposed in which particle-antiparticle pairs are created at the boundary of a steep potential step formed by the suppression of the local vacuum fields. Current antimatter production techniques are reviewed, followed by a description of Dirac's relativistic quantum theory of the vacuum state and corresponding solutions for particle tunneling and reflection from a potential barrier. The use of the Casimir effect to suppress local vacuum fields is presented as a possible technique for generating the sharp potential gradients required for particle-antiparticle pair creation.
Presenting Food Science Effectively
Winter, Carl K.
2016-01-01
While the need to present food science information effectively is viewed as a critical competency for food scientists by the Institute of Food Technologists, most food scientists may not receive adequate training in this area. Effective presentations combine both scientific content and delivery mechanisms that demonstrate presenter enthusiasm for…
Adverse effects of bisphosphonates
DEFF Research Database (Denmark)
Abrahamsen, Bo
2010-01-01
and are tolerated by the majority of patients, but serious adverse events have been recorded in some cases. Only the most common of adverse effects are robustly observable in clinical trials. In general, studies were not powered to detect effects that were lower in incidence than fractures. This review of adverse...
Experiences with effects specifications
DEFF Research Database (Denmark)
Simonsen, Jesper; Hertzum, Morten; Barlach, Anders
2011-01-01
We describe the effects-specification process from a project that was conducted during the fall 2010 and spring of 2011 in this chapter. The project configured and implemented an electronic patient record system at a maternity ward at a hospital located in a European region. The process comprised...... for measuring effects were designed. The project is analyzed and lessons learned are discussed....
Safeguards system effectiveness modeling
International Nuclear Information System (INIS)
Bennett, H.A.; Boozer, D.D.; Chapman, L.D.; Daniel, S.L.; Engi, D.; Hulme, B.L.; Varnado, G.B.
1976-01-01
A general methodology for the comparative evaluation of physical protection system effectiveness at nuclear facilities is presently under development. The approach is applicable to problems of sabotage or theft at fuel cycle facilities. The overall methodology and the primary analytic techniques used to assess system effectiveness are briefly outlined
Safeguards system effectiveness modeling
International Nuclear Information System (INIS)
Bennett, H.A.; Boozer, D.D.; Chapman, L.D.; Daniel, S.L.; Engi, D.; Hulme, B.L.; Varnado, G.B.
1976-01-01
A general methodology for the comparative evaluation of physical protection system effectiveness at nuclear facilities is presently under development. The approach is applicable to problems of sabotage or theft at fuel cycle facilities. In this paper, the overall methodology and the primary analytic techniques used to assess system effectiveness are briefly outlined
International Nuclear Information System (INIS)
2006-06-01
This road-map proposes by the Group Total aims to inform the public on the greenhouse effect gases. It presents the greenhouses effect as a key component of the climate system, the impacts of the human activity, the foreseeable consequences of global warming, the Kyoto protocol and Total commitment in the domain. (A.L.B.)
Isotopic effect giant resonances
International Nuclear Information System (INIS)
Buenerd, M.; Lebrun, D.; Martin, P.; Perrin, G.; Saintignon, P. de; Chauvin, J.; Duhamel, G.
1981-10-01
The systematics of the excitation energy of the giant dipole, monopole, and quadrupole resonances are shown to exhibit an isotopic effect. For a given element, the excitation energy of the transition decreases faster with the increasing neutron number than the empirical laws fitting the overall data. This effect is discussed in terms of the available models
Braeken, Johan; Mulder, Joris; Wood, Stephen
2015-01-01
Assessing the relative importance of predictors has been of historical importance in a variety of disciplines including management, medicine, economics, and psychology. When approaching hypotheses on the relative ordering of the magnitude of predicted effects (e.g., the effects of discrimination
International Nuclear Information System (INIS)
1990-01-01
In the present report, data on RBE values for effects in tissues of experimental animals and man are analysed to assess whether for specific tissues the present dose limits or annual limits of intake based on Q values, are adequate to prevent deterministic effects. (author)
DEFF Research Database (Denmark)
Di Nucci, Ezio
2014-01-01
cases from the literature on double effect such as, amongst others, strategic bombing, the trolley problem, and craniotomy. I find that, despite some common features such as the dilemmatic structure and the inevitability of a bad effect, Aristotle’s mixed actions do not count as cases justifiable...
International Nuclear Information System (INIS)
Fry, R.J.M.
1987-07-01
As more people spend more time in space, and the return to the moon and exploratory missions are considered, the risks require continuing examination. The effects of microgravity and radiation are two potential risks in space. These risks increase with increasing mission duration. This document considers the risk of radiation effects in space workers and explorers. 17 refs., 1 fig., 4 tabs
International Nuclear Information System (INIS)
2004-01-01
In the framework of the sustainable development, this paper presents the greenhouse effect and its impact on the climatic change, the world interest from Rio to Buenos Aires, the human activities producing the carbon dioxide and responsible of the greenhouse effect, the carbon dioxide emission decrease possibilities and shows the necessity of the electric power producers contribution. (A.L.B.)
Petrov, Alexey A
2016-01-01
This book is a broad-based text intended to help the growing student body interested in topics such as gravitational effective theories, supersymmetric effective theories, applications of effective theory techniques to problems in condensed matter physics (superconductivity) and quantum chromodynamics (such as soft-collinear effective theory). It begins with a review of the use of symmetries to identify the relevant degrees of freedom in a problem, and then presents a variety of methods that can be used to solve physical problems. A detailed discussion of canonical examples of effective field theories with increasing complexity is then conducted. Special cases such as supersymmetry and lattice EFT are discussed, as well as recently-found applications to problems in gravitation and cosmology. An appendix includes various factoids from group theory and other topics that are used throughout the text, in an attempt to make the book self-contained.
Directory of Open Access Journals (Sweden)
Sidharth Sonthalia
2015-01-01
Full Text Available Nocebo effect, originally denoting the negative counterpart of the placebo phenomenon, is now better defined as the occurrence of adverse effects to a therapeutic intervention because the patient expects them to develop. More commonly encountered in patients with a past negative experience, this effect stems from highly active processes in the central nervous system, mediated by specific neurotransmitters and modulated by psychological mechanisms such as expectation and conditioning. The magnitude of nocebo effect in clinical medicine is being increasingly appreciated and its relevance encompasses clinical trials as well as clinical practice. Although there is hardly any reference to the term nocebo in dermatology articles, the phenomenon is encountered routinely by dermatologists. Dermatology patients are more susceptible to nocebo responses owing to the psychological concern from visibility of skin lesions and the chronicity, unpredictable course, lack of ′permanent cure′ and frequent relapses of skin disorders. While finasteride remains the prototypical drug that displays a prominent nocebo effect in dermatologic therapeutics, other drugs such as isotretinoin are also likely inducers. This peculiar phenomenon has recently been appreciated in the modulation of itch perception and in controlled drug provocation tests in patients with a history of adverse drug reactions. Considering the conflict between patients′ right to information about treatment related adverse effects and the likelihood of nocebo effect stemming from information disclosure, the prospect of ethically minimizing nocebo effect remains daunting. In this article, we review the concept of nocebo effect, its postulated mechanism, relevance in clinical dermatology and techniques to prevent it from becoming a barrier to effective patient management.
[Psychoanalysis and Side Effect].
Shirahase, Joichiro
2015-01-01
A study of psychoanalysis from the perspective of side effects reveals that its history was a succession of measures to deal with its own side effects. This, however, does not merely suggest that, as a treatment method, psychoanalysis is incomplete and weak: rather, its history is a record of the growth and development of psychoanalysis that discovered therapeutic significance from phenomena that were initially regarded as side effects, made use of these discoveries, and elaborated them as a treatment method. The approach of research seen during the course of these developments is linked to the basic therapeutic approach of psychoanalysis. A therapist therefore does not draw conclusions about a patient's words and behaviors from a single aspect, but continues to make efforts to actively discover a variety of meanings and values from them, and to make the patient's life richer and more productive. This therapeutic approach is undoubtedly one of the unique aspects of psychoanalysis. I discuss the issue of psychoanalysis and side effects with the aim of clarifying this unique characteristic of psychoanalysis. The phenomenon called resistance inevitably emerges during the process of psychoanalytic treatment. Resistance can not only obstruct the progress of therapy; it also carries the risk of causing a variety of disadvantages to the patient. It can therefore be seen as an adverse effect. However, if we re-examine this phenomenon from the perspective of transference, we find that resistance is in fact a crucial tool in psychoanalysis, and included in its main effect, rather than a side effect. From the perspective of minimizing the character of resistance as a side effect and maximizing its character as a main effect, I have reviewed logical organization, dynamic evaluation, the structuring of treatment, the therapist's attitudes, and the training of therapists. I conclude by stating that psychoanalysis has aspects that do not match the perspective known as a side
A Study on the Applications of Quantum Optical Coherence to Nano-Optics
Hakami, Jabir Wali
Optically controlled dipole-dipole interaction at submicrometers and subwavelength scales leads to many interesting phenomenon and remarkable potential applications in quantum optics, condensed matter physics, and today's micro-devices. In this dissertation, we study the applications of quantum optical coherence to nano-optics in the following systems and aspects. On the one hand, chiral metamaterials has been previously reported as excellent candidates to realize both attractive and repulsive Casimir forces, where the existence of a repulsive Casimir force depends upon the strength of the chirality. On the other hand, nanoscale integration of metal nanoparticles and semiconductors is particularly interesting because the strengths of both materials are combined in such a hybrid system. In the first part of this work, we proposed a technical scheme to coherently control of the Casimir interaction energy with two identical chirality mediums. We took explicit caution regarding the requirements of passivity and causal response of the materials, since these requirements are essential for the application of the Lifshitz formula. The rare-earth metals' atomic species, for instance, dysprosium, is proposed as an applicable medium for the forthcoming studies of possible experimental implementation of our technique. Secondly, we fully investigated the coherent control of the quantum optical properties of spontaneous emission spectra of a semiconductor quantum dot coupled to a metallic nanoparticle. The properties of the spontaneous emission spectra of such a system are studied in detail with and without involving the coherent field. The Rabi splitting effect in the spectrum emitted by the quantum dot under particular conditions is predicted for different sizes of the metal nanoparticles. We show that the spontaneous emission spectra of the transition coupled to surface plasmons may be further modified by adjusting the external coherent control on the adjacent transitions. In
Creating more effective graphs
Robbins, Naomi B
2012-01-01
A succinct and highly readable guide to creating effective graphs The right graph can be a powerful tool for communicating information, improving a presentation, or conveying your point in print. If your professional endeavors call for you to present data graphically, here's a book that can help you do it more effectively. Creating More Effective Graphs gives you the basic knowledge and techniques required to choose and create appropriate graphs for a broad range of applications. Using real-world examples everyone can relate to, the author draws on her years of experience in gr
Directory of Open Access Journals (Sweden)
Frank Roumen
2017-01-01
Full Text Available We will define two ways to assign cohomology groups to effect algebras, which occur in the algebraic study of quantum logic. The first way is based on Connes' cyclic cohomology. The resulting cohomology groups are related to the state space of the effect algebra, and can be computed using variations on the Kunneth and Mayer-Vietoris sequences. The second way involves a chain complex of ordered abelian groups, and gives rise to a cohomological characterization of state extensions on effect algebras. This has applications to no-go theorems in quantum foundations, such as Bell's theorem.
The effective nuclear potential
International Nuclear Information System (INIS)
Skyrme, T.H.R.
1994-01-01
An empirical analyses is made of the mean effective internucleon potential required in the shell-model description of nuclei, allowing for the presence of many-body effects as suggested by current theory. A consistent description is found in which the effective two-body interaction acts almost entirely in even states, and the many-body effects are simulated by a repulsive three-body contact interaction. The strength of the two-body interaction is consistent with that expressed by the free scattering matrix of the two-nucleon system, and that of the three-body interaction with the 'rearrangement energy' calculated in the many-body theory. (author). 21 refs, 2 figs, 7 tabs
Theory of Effectiveness Measurement
National Research Council Canada - National Science Library
Bullock, Richard K
2006-01-01
Effectiveness measures provide decision makers feedback on the impact of deliberate actions and affect critical issues such as allocation of scarce resources, as well as whether to maintain or change existing strategy...
International Nuclear Information System (INIS)
Fry, R.J.M.
1986-01-01
The paper discusses the radiation environment in space that astronauts are likely to be exposed to. Emphasis is on proton and HZE particle effects. Recommendations for radiation protection guidelines are presented
Cancer treatments may lower your appetite. Side effects such as nausea, fatigue, or mouth sores can also making eating difficult. Learn how to eat well to avoid losing weight or becoming dehydrated, so you stay strong during treatment.
Fatigue is a common side effect of many cancer treatments such as chemotherapy, radiation therapy, immunotherapy, and surgery. Anemia and pain can also cause fatigue. Learn about symptoms and way to manage fatigue.
Sleep problems are a common side effect during cancer treatment. Learn how a polysomnogram can assess sleep problems. Learn about the benefits of managing sleep disorders in men and women with cancer.
Developing Effective Performance Measures
2014-10-14
University When Performance Measurement Goes Bad Laziness Vanity Narcissism Too Many Pettiness Inanity 52 Developing Effective...Kasunic, October 14, 2014 © 2014 Carnegie Mellon University Narcissism Measuring performance from the organization’s point of view, rather than from
National Research Council Canada - National Science Library
Friman, Henrik
2006-01-01
... (extended from Leavitt, 1965). This text identifies aspects of network-based effectiveness that can benefit from a better understanding of leadership and management development of people, procedures, technology, and organizations...
Authoring Effective Demonstrations
National Research Council Canada - National Science Library
Fu, Dan; Jensen, Randy; Salas, Eduardo; Rosen, Michael A; Ramachandran, Sowmya; Upshaw, Christin L; Hinkelman, Elizabeth; Lampton, Don
2007-01-01
... or human role-players for each training event. We report our ongoing efforts to (1) research the nature and purpose of demonstration, articulating guidelines for effective demonstration within a training context, and (2...
Frost Effects Research Facility
Federal Laboratory Consortium — Full-scale study in controlled conditionsThe Frost Effects Research Facility (FERF) is the largest refrigerated warehouse in the United States that can be used for a...
Controlling pain is an important part of your cancer treatment plan. Learn how to track levels of pain. Find out how pain, a side effect of cancer treatment, is treated using acupuncture, biofeedback, and physical therapy.
Kim, Tae Hyong; Johnstone, Jennie; Loeb, Mark
2011-09-01
Vaccination ideally protects susceptible populations at high risk for complications of the infection. However, vaccines for these subgroups do not always provide sufficient effectiveness. The herd effect or herd immunity is an attractive way to extend vaccine benefits beyond the directly targeted population. It refers to the indirect protection of unvaccinated persons, whereby an increase in the prevalence of immunity by the vaccine prevents circulation of infectious agents in susceptible populations. The herd effect has had a major impact in the eradication of smallpox, has reduced transmission of pertussis, and protects against influenza and pneumococcal disease. A high uptake of vaccines is generally needed for success. In this paper we aim to provide an update review on the herd effect, focusing on the clinical benefit, by reviewing data for specific vaccines.
Flexoelectric Effect in Solids
Zubko, Pavlo; Catalan, Gustau; Tagantsev, Alexander K.
2013-07-01
Flexoelectricity-the coupling between polarization and strain gradients-is a universal effect allowed by symmetry in all materials. Following its discovery several decades ago, studies of flexoelectricity in solids have been scarce due to the seemingly small magnitude of this effect in bulk samples. The development of nanoscale technologies, however, has renewed the interest in flexoelectricity, as the large strain gradients often present at the nanoscale can lead to strong flexoelectric effects. Here we review the fundamentals of the flexoelectric effect in solids, discuss its presence in many nanoscale systems, and look at potential applications of this electromechanical phenomenon. The review also emphasizes the many open questions and unresolved issues in this developing field.
... Pet Shelters Protect Your Pets Health Effects of Tsunamis Language: English Español (Spanish) Recommend on Facebook Tweet ... environmental hazards. The majority of deaths associated with tsunamis are related to drownings, but traumatic injuries are ...
Reflections on greenhouse effect
International Nuclear Information System (INIS)
Ortoli, F.X.
1993-01-01
After a brief introduction on greenhouse effect phenomenon, the author approaches economic aspects and costs of greenhouse gases emission abatement and describes an energy policy which takes account of economical constraints and environmental impacts
Nutrient pollution has diverse and far-reaching effects on the U.S. economy, impacting tourism, property values, commercial fishing, recreational businesses and many other sectors that depend on clean water.
Diarrhea, a side effect of cancer treatment, may cause symptoms such as loose, watery stools. Diarrhea can lead to dehydration and malnutrition in cancer patients. Learn about ways to treat and manage diarrhea during cancer treatment.
Deforestation Hydrological Effects
International Nuclear Information System (INIS)
Poveda J, G.; Mesa S, O.J.
1995-01-01
Deforestation causes strong disturbances in ecosystems and in hydrological cycle, increasing or reducing wealths. Particularly in this work, effects of feed back between interface processes land - atmosphere are discussed and is demonstrated that losses of water by evaporation-transpiration are thoroughly indispensable to maintain the balance of hydrological regime. It's concluded that as a rule the effect of deforestation is to reduce wealth middle and to increase extreme wealth with consequent stronger and more frequent droughts or flood effects. Other deforestation effects as increase in superficial temperature, increase in atmospherical pressure, decrease in soil moisture, decrease in evaporation-transpiration, decrease of soil ruggedness, decrease of thickness of atmospherical cap limit, decrease of clouds, decrease of rain in both medium and long term and the consequent decrease of rivers wealth middle are explained. Of other side, the basins with greater deforestation affectation in Colombia are indicated. Finally, it's demonstrated the need of implementing reforestation programs
Anemia is a side effect of cancer treatments, including chemotherapy and radiation therapy. It can make women and men feel fatigued, dizzy, and short of breath. Learn how to manage fatigue caused by anemia during cancer treatment.
DEFF Research Database (Denmark)
Hansen, Mie Østergaard
The present report studies the mechanism of the occlusion effect by means of literature studies, experiments and model estimates. A mathematical model of the occlusion effect is developed. The model includes the mechanical properties of the earmould and the airborne sound as well as the body...... conducted sound from own voice. These aspects are new in the sense that previous studies disregard the earmould mechanics and includes only one sound source placed in the ear canal....
International Nuclear Information System (INIS)
Poitou, J.
2008-04-01
In the framework of the climatic change, the author aims to explain the phenomena of greenhouse effect. He details the historical aspects of the scientific knowledge in the domain, the gases produced, some characteristic of the greenhouse effect, the other actors which contribute to the climate, the climate simulation, the different factors of climate change since 1750 and the signs of the global heating. (A.L.B.)
Vella, Dominic; Mahadevan, L.
2004-01-01
Objects that float at the interface between a liquid and a gas interact because of interfacial deformation and the effect of gravity. We highlight the crucial role of buoyancy in this interaction, which, for small particles, prevails over the capillary suction that is often assumed to be the dominant effect. We emphasize this point using a simple classroom demonstration, and then derive the physical conditions leading to mutual attraction or repulsion. We also quantify the force of interactio...
Modulational effects in accelerators
International Nuclear Information System (INIS)
Satogata, T.
1997-01-01
We discuss effects of field modulations in accelerators, specifically those that can be used for operational beam diagnostics and beam halo control. In transverse beam dynamics, combined effects of nonlinear resonances and tune modulations influence diffusion rates with applied tune modulation has been demonstrated. In the longitudinal domain, applied RF phase and voltage modulations provide mechanisms for parasitic halo transport, useful in slow crystal extraction. Experimental experiences with transverse tune and RF modulations are also discussed
Kim, Tae Hyong; Johnstone, Jennie; Loeb, Mark
2011-01-01
Vaccination ideally protects susceptible populations at high risk for complications of the infection. However, vaccines for these subgroups do not always provide sufficient effectiveness. The herd effect or herd immunity is an attractive way to extend vaccine benefits beyond the directly targeted population. It refers to the indirect protection of unvaccinated persons, whereby an increase in the prevalence of immunity by the vaccine prevents circulation of infectious agents in susceptible pop...
Dr. Basanti Jain
2017-01-01
The abnormal increase in the concentration of the greenhouse gases is resulting in higher temperatures. We call this effect is global warming. The average temperature around the world has increased about 1'c over 140 years, 75% of this has risen just over the past 30 years. The solar radiation, as it reaches the earth, produces "greenhouse effect" in the atmosphere. The thick atmospheric layers over the earth behaves as a glass surface, as it permits short wave radiations from coming in, but ...
Modeling information technology effectiveness
Aleksander Lotko
2005-01-01
Numerous cases of systems not bringing expected results cause that investments in information technology are treated more and more carefully and are not privileged amongst others. This gives rise to the need for applying costs–effect calculations. Modeling IT effectiveness is a procedure which helps to bring system complexity under control. By using proper measures it is possible to perform an objective investment appraisal for projects under consideration. In the paper, a framework of method...
Weeks, Edwin P
2002-01-01
The Lisse effect is a rarely noted phenomenon occurring when infiltration caused by intense rain seals the surface soil layer to airflow, trapping air in the unsaturated zone. Compression of air by the advancing front results in a pressure increase that produces a water-level rise in an observation well screened below the water table that is several times as large as the distance penetrated by the wetting front. The effect is triggered by intense rains and results in a very rapid water-level rise, followed by a recession lasting a few days. The Lisse effect was first noted and explained by Thal Larsen in 1932 from water-level observations obtained in a shallow well in the village of Lisse, Holland. The original explanation does not account for the increased air pressure pushing up on the bottom of the wetting front. Analysis of the effect of this upward pressure indicates that a negative pressure head at the base of the wetting front, psi(f), analogous to that postulated by Green and Ampt (1911) to explain initially rapid infiltration rates into unsaturated soils, is involved in producing the Lisse effect. Analysis of recorded observations of the Lisse effect by Larsen and others indicates that the water-level rise, which typically ranges from 0.10 to 0.55 m, should be only slightly larger than psi(f) and that the depth of penetration of the wetting front is no more than several millimeters.
A Hamiltonian five-field gyrofluid model
Energy Technology Data Exchange (ETDEWEB)
Keramidas Charidakos, I.; Waelbroeck, F. L.; Morrison, P. J. [Institute for Fusion Studies and Department of Physics, The University of Texas at Austin, Austin, TX 78712 (United States)
2015-11-15
A Lie-Poisson bracket is presented for a five-field gyrofluid model, thereby showing the model to be Hamiltonian. The model includes the effects of magnetic field curvature and describes the evolution of the electron and ion gyro-center densities, the parallel component of the ion and electron velocities, and the ion temperature. The quasineutrality property and Ampère's law determine, respectively, the electrostatic potential and magnetic flux. The Casimir invariants are presented, and shown to be associated with five Lagrangian invariants advected by distinct velocity fields. A linear, local study of the model is conducted both with and without Landau and diamagnetic resonant damping terms. Stability criteria and dispersion relations for the electrostatic and the electromagnetic cases are derived and compared with their analogs for fluid and kinetic models.
On the renormalization of string functionals
International Nuclear Information System (INIS)
Dietz, K.; Filk, T.
1982-09-01
We investigate analytic renormalization procedures for functional integrals, corresponding to field theories defined on compact manifolds, which arise e.g. from string functionals of the Nambu-Schild-Eguchi type. Although these models belong to the nonrenormalizable class of quantum field theories, we prove finiteness for a rectangular string shape up to three loop level, for circular boundary up to two loop order, and for a variety of graphs in higher order, thus indicating that the result might hold in general. From the explicit calculation of the two loop approximation we extract the first model dependent corrections to the qanti q - potential or the Casimir effect. The importance of dilation transformations for the properties of the renormalization procedure are investigated. We prove that under certain conditions, forced by symmetry properties, the association of finite values to divergent series is unique, independent of the regularization procedure. (orig.)
Atom-surface potentials and atom interferometry
International Nuclear Information System (INIS)
Babb, J.F.
1998-01-01
Long-range atom-surface potentials characterize the physics of many actual systems and are now measurable spectroscopically in deflection of atomic beams in cavities or in reflection of atoms in atomic fountains. For a ground state, spherically symmetric atom the potential varies as -1/R 3 near the wall, where R is the atom-surface distance. For asymptotically large distances the potential is weaker and goes as -1/R 4 due to retardation arising from the finite speed of light. This diminished interaction can also be interpreted as a Casimir effect. The possibility of measuring atom-surface potentials using atomic interferometry is explored. The particular cases studied are the interactions of a ground-state alkali-metal atom and a dielectric or a conducting wall. Accurate descriptions of atom-surface potentials in theories of evanescent-wave atomic mirrors and evanescent wave-guided atoms are also discussed. (author)
International Nuclear Information System (INIS)
Sernelius, Bo E
2008-01-01
The energy spectrum of electromagnetic normal modes plays a central role in the theory of the van der Waals and Casimir interaction. Here we study the modes in connection with the van der Waals interaction between two metal half spaces. Neglecting dissipation leads to distinct normal modes with real-valued frequencies. Including dissipation seems to have the effect that these distinct modes move away from the real axis into the complex frequency plane. The summation of the zero-point energies of these modes render a complex-valued result. Using the contour integration, resulting from the use of the generalized argument principle, gives a real-valued and different result. We resolve this contradiction and show that the spectrum of true normal modes forms a continuum with real frequencies
Spectral functions in mathematics and physics
Kirsten, Klaus
2002-01-01
The literature on the spectral analysis of second order elliptic differential operators contains a great deal of information on the spectral functions for explicitly known spectra. The same is not true, however, for situations where the spectra are not explicitly known. Over the last several years, the author and his colleagues have developed new, innovative methods for the exact analysis of a variety of spectral functions occurring in spectral geometry and under external conditions in statistical mechanics and quantum field theory. Spectral Functions in Mathematics and Physics presents a detailed overview of these advances. The author develops and applies methods for analyzing determinants arising when the external conditions originate from the Casimir effect, dielectric media, scalar backgrounds, and magnetic backgrounds. The zeta function underlies all of these techniques, and the book begins by deriving its basic properties and relations to the spectral functions. The author then uses those relations to d...
Directory of Open Access Journals (Sweden)
S. Bedra
2017-05-01
Full Text Available In this paper, an electromagnetic approach based on cavity model in conjunction with electromagnetic knowledge was developed. The cavity model combined with London’s equations and the Gorter-Casimir two-fluid model has been improved to investigate the resonant characteristics of high Tc superconducting circular microstrip patch in the case where the patch is printed on uniaxially anisotropic substrate materials. Merits of our extended model include low computational cost and mathematical simplify. The numerical simulation of this modeling shows excellent agreement with experimental results available in the literature. Finally, numerical results for the dielectric anisotropic substrates effects on the operating frequencies for the case of superconducting circular patch are also presented.
Light moduli in almost no-scale models
International Nuclear Information System (INIS)
Buchmueller, Wilfried; Moeller, Jan; Schmidt, Jonas
2009-09-01
We discuss the stabilization of the compact dimension for a class of five-dimensional orbifold supergravity models. Supersymmetry is broken by the superpotential on a boundary. Classically, the size L of the fifth dimension is undetermined, with or without supersymmetry breaking, and the effective potential is of no-scale type. The size L is fixed by quantum corrections to the Kaehler potential, the Casimir energy and Fayet-Iliopoulos (FI) terms localized at the boundaries. For an FI scale of order M GUT , as in heterotic string compactifications with anomalous U(1) symmetries, one obtains L∝1/M GUT . A small mass is predicted for the scalar fluctuation associated with the fifth dimension, m ρ 3/2 /(L M). (orig.)
Habituation of reinforcer effectiveness
Directory of Open Access Journals (Sweden)
David R Lloyd
2014-01-01
Full Text Available In this paper we propose an integrative model of habituation of reinforcer effectiveness (HRE that links behavioral and neural based explanations of reinforcement. We argue that habituation of reinforcer effectiveness (HRE is a fundamental property of reinforcing stimuli. Most reinforcement models implicitly suggest that the effectiveness of a reinforcer is stable across repeated presentations. In contrast, an HRE approach predicts decreased effectiveness due to repeated presentation. We argue that repeated presentation of reinforcing stimuli decreases their effectiveness and that these decreases are described by the behavioral characteristics of habituation (McSweeney and Murphy, 2009;Rankin et al., 2009. We describe a neural model that postulates a positive association between dopamine neurotransmission and HRE. We present evidence that stimulant drugs, which artificially increase dopamine neurotransmission, disrupt (slow normally occurring HRE and also provide evidence that stimulant drugs have differential effects on operant responding maintained by reinforcers with rapid vs. slow HRE rates. We hypothesize that abnormal HRE due to genetic and/or environmental factors may underlie some behavioral disorders. For example, recent research indicates that slow-HRE is predictive of obesity. In contrast ADHD may reflect ‘accelerated-HRE’. Consideration of HRE is important for the development of effective reinforcement based treatments. Finally, we point out that most of the reinforcing stimuli that regulate daily behavior are non-consumable environmental/social reinforcers which have rapid-HRE. The almost exclusive use of consumable reinforcers with slow-HRE in pre-clinical studies with animals may have caused the importance of HRE to be overlooked. Further study of reinforcing stimuli with rapid-HRE is needed in order to understand how habituation and reinforcement interact and regulate behavior.
International Nuclear Information System (INIS)
Guz, A.N.; Kokhanenko, Yu.V.
1995-01-01
In the present article we survey papers on edge effects investigated by the rigorous approach. We interpret edge effects as stressed states created in a composite as a result of zones in which the stresses exhibit a rapidly changing behavior in comparison with the slow variation of the stresses outside such zones. Here the range of the edge effect is defined as the distance from the point of its inception to the boundary of the edge zone in a given direction. The transition of the stresses to the slowly varying state is determined within prescribed error limits. The size and configuration of the edge zone depends on the tolerated error. Clearly, the main difficulty associated with the rigorous approach is finding solutions of the elasticity problems. The finite-difference approach is suggested for the approximate solution of these problems. In light of the comparative time consumption of the finite-difference approach, it is best directed at certain classes of problems rather than at particular individual problems. Not too many papers on the investigation of edge effects by the rigorous approach have been published to date. Below, following in their footsteps, we formulate edge effect problems in composites, determine classes of problems, and investigate edge effects in composite materials and structural elements using them in Cartesian (planar and three-dimensional problems) and cylindrical (axisymmetric problems) coordinate frames. We note that the division of approaches to the study of edge effects into qualitative (nonrigorous) and quantitative (rigorous) reflects the authors own point of view. Of course, other schemes of classification of the approaches to the investigation of the regions of rapidly varying states in composites are possible
Magnetoelectric effects in manganites
Jeen, Hyoung Jeen
Research on manganites has been conducted for more than half century. Recent discoveries of colossal responses to external fields such as colossal magnetoresistance effects and correlation among spin, orbital, and lattice in phase separated manganites and multiferroic manganites have motivated me to understand these materials. The main purpose of this dissertation is to understand magnetoelectric effects in phase separated (La1-yPr y)1-xCaxMnO3 (LPCMO) thin films and multiferroic BiMnO3 (BMO) thin films. First, high quality phase separated manganite thin films have been successfully grown. To grow the high quality manganite thin films, extensive effort was devoted to fine tuning of oxygen pressure, temperature, and laser fluence during film growth. As-grown films were characterized with various ex-situ techniques: magnetization measurements, transport measurements, x-ray diffraction, atomic force microscopy, and/or transmission electron microscopy to remove the effects of impurities and unwanted strains except substrate induced strain. Second, three major results were obtained in high quality phase separated LPCMO thin films. These results are based on the dynamic nature of phases in LPCMO. 1) LPCMO thin films showed single domain to multi-domain transition during cooling. This transition can be tuned by substrate stress induced in-plane magnetic anisotropy. 2) Evidence for the origin of colossal electroresistance (CER) effect has been observed. The CER is triggered by dielectrophoresis, or movements of ferromagnetic metallic (FMM) phase, which is manifested in anisotropic transport properties in microfabricated LPCMO cross structures. This fluidic nature of the FMM phase in LPCMO under high electric fields lead to exotic magnetoelectric effects. 3) Electric field effects on magnetotransport properties have been observed. This phenomena can also be tuned by the combined effect of substrate strain and current flow. This combined effect of electric and magnetic
Radiation effects and radioprotectors
International Nuclear Information System (INIS)
Purohit, R.K.; Bugalia, Saroj; Dakshene, Monika
2012-01-01
Radiation exposure causes damage to biological systems and these damages are mediated by the generation of free radicals and reactive oxygen species targeting vital cellular components such as DNA and membranes. DNA repair systems and the endogenous cellular biochemical defense mechanisms against reactive oxygen species and antioxidants enzymes like reduced Glutathione (GSH), Superoxide dismutase, Glutathione peroxidase catalase etc. fail upon exposures to higher as well as chronic radiation doses leading to alterations in cell functions, cell death or mutations. Radioprotectors prevent these alterations and protect cells and tissues from the deleterious effects of radiations. Radioprotectors are of great importance due to their possible and potential application during planned radiation exposures such as radiotherapy, diagnostic scanning, clean up operations in nuclear accidents, space expeditions etc. and Unplanned radiations exposures such as accidents in nuclear industry, nuclear terrorism, natural background radiation etc. Many of the available synthetic radioprotectors are toxic to mammalian system at doses required to be effective as radioprotector. Increasing uses of ionizing radiation have drawn the attention of many radiobiologists towards their undesired side effects produced in various tissues and for modifying them to facilitate the beneficial uses of radiation. Modification of radiation response is obtained by means of chemical substances that can significantly decrease the magnitude of response when present in a biological system during irradiation. Radioprotectors are chemicals that modify a cell's response to radiation. Radioprotectors are drugs that protect normal (non cancerous) cells from the damage caused by radiation therapy. These agents promote the repair of normal cells that are exposed to radiation. Various chemicals, like Cysteamine, MPG , WR-2721 have been tested for the protection against harmful effects of radiation. These radio
the effect of training on teachers' knowledge of effective classroom ...
African Journals Online (AJOL)
Global Journal
The purpose of this study was to determine the effectiveness of in-service training on teachers' knowledge of effective ... strategies that teachers believe are effective for classroom management was significantly higher after the training, indicating ... meaningful and effective learning is the ability of the teacher to effectively ...
Pleiotropic effects of statins
Directory of Open Access Journals (Sweden)
Narasaraju Kavalipati
2015-01-01
Full Text Available Statins or 3-hydroxy-methylglutaryl coenzyme A (HMG CoA reductase inhibitors not only prevents the synthesis of cholesterol biosynthesis but also inhibits the synthesis of essential isoprenoid intermediates such as farnesyl pyrophosphate, geranylgeranyl pyrophosphate, isopentanyl adenosine, dolichols and polyisoprenoid side chains of ubiquinone, heme A, and nuclear lamins. These isoprenoid intermediates are required for activation of various intracellular/signaling proteins- small guanosine triphosphate bound protein Ras and Ras-like proteins like Rho, Rab, Rac, Ral, or Rap which plays an indispensible role in multiple cellular processes. Reduction of circulating isoprenoids intermediates as a result of HMG CoA reductase inhibition by statins prevents activation of these signalling proteins. Hence, the multiple effects of statins such as antiinflammatory effects, antioxidant effects, antiproliferative and immunomodulatory effects, plaque stability, normalization of sympathetic outflow, and prevention of platelet aggregation are due to reduction of circulating isoprenoids and hence inactivation of signalling proteins. These multiple lipid-independent effects of statins termed as statin pleiotropy would potentially open floodgates for research in multiple treatment domains catching attentions of researchers and clinician across the globe.
International Nuclear Information System (INIS)
Yao, Y.P.
1981-01-01
There are two problems discussed, both of which have to do with dissimilar magnitudes in mass. Theoretically, we can devise the large difference in mass as observed by decreeing some vev, v/sub i/ to be much bigger than the other; or, we can assume that some couplings g/sub i/ are much stronger. These two different assumptions give rise to entirely different patterns of interaction in the resulting theory. The first way to generate a mass hierarchy can be called the soft way, because in the zeroth order, the large mass scale leaves its foot print merely in a few effective parameters of the residual theory. The effective theory is renormalizable, sans anomaly. In this limit, the heavy particles decouple. The second assumption (g/sub j/ much greater than g/sub j'/) to create mass hierarchy does a lot of violence to a theory. Effects of the large mass scale will be felt by the system left behind in many ways. An infinite number of parameters are needed to summarize the effects in this limit. This is called the hard limit. It follows that the resulting effective Lagrangian, if in fact it makes sense to construct one at all, will be non-polynomial and apparently non-renormalizable
Relative age effect: implications for effective practice.
Andronikos, Georgios; Elumaro, Adeboye Israel; Westbury, Tony; Martindale, Russell J J
2016-01-01
Physical and psychological differences related to birthdate amongst athletes of the same selection year have been characterised as the "relative age effects" (RAEs). RAEs have been identified in a variety of sports, both at youth and adult level, and are linked with dropout of athletes and a reduction of the talent pool. This study examined the existence, mechanisms and possible solutions to RAEs using qualitative methodology. Seven experts in the field of talent identification and development were interviewed. Inductive analysis of the data showed that, while there was mixed evidence for the existence of RAEs across sports, the eradication of RAEs was attributed to controllable features of the development environment. The factors reported included the structure of "categories" used to group athletes within the sport (e.g. age, weight, size, skills), recognition and prioritisation of long-term development over "short term win focus." Education of relevant parties (e.g. coaches, scouts, clubs) about RAEs and the nature of "talent" within a long-term context was suggested, along with careful consideration of the structure of the development environment (e.g. delayed selection, provision for late developers, focus on skills not results, use of challenge). Implications for research and practice are discussed.
Sleboda, Claire
1997-01-01
Quality assurance programs provide a very effective means to monitor and evaluate medical care. Quality assurance involves: (1) Identify a problem; (2) Determine the source and nature of the problem; (3) Develop policies and methods to effect improvement; (4) Implement those polices; (5) Monitor the methods applied; and (6) Evaluate their effectiveness. Because this definition of quality assurance so closely resembles the Nursing Process, the health unit staff was able to use their knowledge of the nursing process to develop many forms which improve the quality of patient care. These forms include the NASA DFRC Service Report, the occupational injury form (Incident Report), the patient survey (Pre-hospital Evaluation/Care Report), the Laboratory Log Sheet, the 911 Run Sheet, and the Patient Assessment Stamp. Examples and steps which are followed to generate these reports are described.
Newman, J. S.; Beattie, K. R.
1985-03-01
This report summarizes the effects of aviation noise in many areas, ranging from human annoyance to impact on real estate values. It also synthesizes the findings of literature on several topics. Included in the literature were many original studies carried out under FAA and other Federal funding over the past two decades. Efforts have been made to present the critical findings and conclusions of pertinent research, providing, when possible, a bottom line conclusion, criterion or perspective. Issues related to aviation noise are highlighted, and current policy is presented. Specific topic addressed include: annoyance; Hearing and hearing loss; noise metrics; human response to noise; speech interference; sleep interference; non-auditory health effects of noise; effects of noise on wild and domesticated animals; low frequency acoustical energy; impulsive noise; time of day weightings; noise contours; land use compatibility; and real estate values. This document is designed for a variety of users, from the individual completely unfamiliar with aviation noise to experts in the field.
DEFF Research Database (Denmark)
Doucouliagos, Hristos; Paldam, Martin
The AEL (aid effectiveness literature) studies the effect of development aid using econometrics on macro data. It contains about 100 papers of which a third analyzes conditional models where aid effectiveness depends upon z, so that aid only works for a certain range of the variable. The key term...... in this family of AEL models is thus an interaction term of z times aid. The leading candidates for z are a good policy index and aid itself. In this paper, meta-analysis techniques are used (i) to determine whether the AEL has established the said interaction terms, and (ii) to identify some of the determinants...... of the differences in results between studies. Taking all available studies in consideration, we find no support for conditionality with respect to policy, while conditionality regarding aid itself is dubious. However, the results differ depending on the authors’ institutional affiliation....
International Nuclear Information System (INIS)
Fidorra, J.
1982-07-01
The biological effectiveness of ionizing radiation is based upon the absorption of energy in molecular structures of a cell. Because of the quantum nature of radiation large fluctuations of energy concentration in subcellulare regions has to be considered. In addition both the spatial distribution of a sensitive molecular target and cellulare repair processes has to be taken into consideration for an assessment of radiation action. In radiation protection the difference between the quality factor and the Relative Biological Effectiveness has a fundamental meaning and will be discussed in more detail. The present report includes a short review on some relevant models on radiation action and a short discussion on effects of low dose irradiation. (orig.) [de
Biological effects of neutrons
Energy Technology Data Exchange (ETDEWEB)
Ogiu, Toshiaki; Ohmachi, Yasushi; Ishida, Yuka [National Inst. of Radiological Sciences, Chiba (JP)] [and others
2003-03-01
Although the occasion to be exposed to neutrons is rare in our life, except for nuclear accidents like in the critical accident at Tokai-mura in 1999, countermeasures against accident should be always prepared. In the Tokai-mura accident, residents received less than 21 mSv of neutrons and gamma rays. The cancer risks and fetal effects of low doses of neutrons were matters of concern among residents. The purpose of this program is to investigate the relative biological effectiveness (RBE) for leukemias, and thereby to assess risks of neutrons. Animal experiments are planed to obtain the following RBEs: (1) RBE for the induction of leukemias in mice and (2) RBE for effects on fetuses. Cyclotron fast neutrons (10 MeV) and electrostatic accelerator-derived neutrons (2 MeV) are used for exposure in this program. Furthermore, cytological and cytogenetic analyses will be performed. (author)
Proactively evaluating training effectiveness
International Nuclear Information System (INIS)
Fetterman, Harry E.
2003-01-01
A common model of the five phase Systematic Approach to Training (SAT) displays the fifth phase, evaluation, feeding back into the previous four phases: analysis, design, development, and implementation. Evaluating training effectiveness in PP and L's Nuclear Department is not simply the fifth phase of the SAT. PP and L has demonstrated a more effective methodology is realized when evaluation is built into each of the other four phases. At PP and L, evaluation is conducted formatively throughout the first four phases of the SAT process and summatively after implementation. (author)
Analgesic effects of melatonin
DEFF Research Database (Denmark)
Wilhelmsen, Michael; Amirian, Ilda; Reiter, Russel J
2011-01-01
studies, melatonin shows potent analgesic effects in a dose-dependent manner. In clinical studies, melatonin has been shown to have analgesic benefits in patients with chronic pain (fibromyalgia, irritable bowel syndrome, migraine). The physiologic mechanism underlying the analgesic actions of melatonin...... has not been clarified. The effects may be linked to G(i) -coupled melatonin receptors, to G(i) -coupled opioid µ-receptors or GABA-B receptors with unknown downstream changes with a consequential reduction in anxiety and pain. Also, the repeated administration of melatonin improves sleep and thereby...
International Nuclear Information System (INIS)
Koshimizu, S.
1992-01-01
Although the pseudo- or super-elasticity phenomena and the shape memory effect were known since the 1940's, the enormous curiosity and the great interest to their practical applications emerged with the development of the NITINOL alloy (Nickel-Titanium Naval Ordance Laboratory) by the NASA during the 1960's. This fact marked the appearance of a new class of materials, popularly known as shape memory effect alloys (SMEA). The objective of this work is to present a state-of-the-art of the development and applications for the SMEA. (E.O.)
International Nuclear Information System (INIS)
Tubiana, M.
1997-01-01
In this article is asked the question about a possible carcinogens effect of low dose irradiation. With epidemiological data, knowledge about the carcinogenesis, the professor Tubiana explains that in spite of experiments made on thousand or hundred of thousands animals it has not been possible to bring to the fore a carcinogens effect for low doses and then it is not reasonable to believe and let the population believe that low dose irradiation could lead to an increase of neoplasms and from this point of view any hardening of radiation protection standards could in fact, increase anguish about ionizing radiations. (N.C.)
Climate, greenhouse effect, energy
International Nuclear Information System (INIS)
Henriksen, Thormod; Kanestroem, Ingolf
2001-01-01
The book has sections on the sun as energy source, the earth climate and it's changes and factors influencing this, the greenhouse effect on earth and other planets, greenhouse gases and aerosols and their properties and importance, historic climate and paleoclimate, climatic models and their uses and limitations, future climate, consequences of climatic changes, uncertainties regarding the climate and measures for reducing the greenhouse effect. Finally there are sections on energy and energy resources, the use, sources such as fossil fuels, nuclear power, renewable resources, heat pumps, energy storage and environmental aspects and the earth magnetic field is briefly surveyed
Buncel, Erwin
2015-01-01
This book introduces the concepts, theory and experimental knowledge concerning solvent effects on the rate and equilibrium of chemical reactions of all kinds. It begins with basic thermodynamics and kinetics, building on this foundation to demonstrate how a more detailed understanding of these effects may be used to aid in determination of reaction mechanisms, and to aid in planning syntheses. Consideration is given to theoretical calculations (quantum chemistry, molecular dynamics, etc.), to statistical methods (chemometrics), and to modern day concerns such as ""green"" chemistry, where ut
Laurent Guiraud
1998-01-01
Members of the RD39 collaboration stage a demonstration of the Lazarus effect in the CERN cryolab. At the LHC experiments, the front-line inner detectors - trackers - will be traversed by a mammoth thousand million million passing particles per square centimetre over the lifetimes of the experiments. After long exposure to passing particles, defects appear in the silicon and the signal is destroyed. A group of physicists at Bern University have found that at temperatures below 100 K, dead detectors apparently come back to life. They're calling their discovery the Lazarus effect after the Biblical character raised from the dead by Jesus after he had been entombed for four days.
Training effectiveness evaluation model
International Nuclear Information System (INIS)
Penrose, J.B.
1993-01-01
NAESCO's Training Effectiveness Evaluation Model (TEEM) integrates existing evaluation procedures with new procedures. The new procedures are designed to measure training impact on organizational productivity. TEEM seeks to enhance organizational productivity through proactive training focused on operation results. These results can be identified and measured by establishing and tracking performance indicators. Relating training to organizational productivity is not easy. TEEM is a team process. It offers strategies to assess more effectively organizational costs and benefits of training. TEEM is one organization's attempt to refine, manage and extend its training evaluation program
Renville, Gary
1999-01-01
Describes the positive mental, physical, and social growth impacts that the camping experience had on the author, and urges camp program evaluation to plan and implement such changes. Sidebar lists steps of effective evaluation: program goals and objectives, goals of evaluation, implementation of evaluation, data analysis, and findings and…
Effective presentation skills.
Dolan, Robert
2017-12-29
Most PhD's will have a presentation component during the interview process, as well as presenting their work at conferences. This article will provide guidance on how to develop relevant content and effectively deliver it to your audience. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
African Journals Online (AJOL)
Prof. Adipala Ekwamu
To assess the effect of coconut fruit set on the variation expression of the number of nuts yielded at the end of the fructification, a modelling approach was used. Four female parents namely Kar Kar Tall (KKT), Kappadam. Tall (KPD), Sri Lanka Tall (SLT) and Vanuatu Tall (VTT) as well as four male parents known as Panama.
Indian Academy of Sciences (India)
may encounter matter which might affect their energy and path in ways that will have observable effects. One such case is that of CMBR photons streaming through a region of galaxy clusters. ... change its energy in a dramatic fashion. This is called the `inverse Compton scattering', but to understand it we need to ...
Clement, Charles; Dawson, Peter
2017-06-01
In response to Kate Brown’s article “Chernobyl’s hidden legacy (Physics World Focus on Nuclear Energy 2017 pp9-11) in which she argues that researchers today should be looking at Soviet-era information on the medical effects of the Chernobyl disaster.
Haemodynamic effects of eating
DEFF Research Database (Denmark)
Høost, U; Kelbaek, H; Rasmusen, H
1996-01-01
1. The purpose of this study was to investigate the effect of fractional meal stimulation on postprandial haemodynamic changes, the possible correlation between these changes and the potential mediating role of circulating catecholamines and insulin. 2. Healthy young subjects were studied before...
DEFF Research Database (Denmark)
Erfgen, Carsten; Zenker, Sebastian; Sattler, Henrik
2015-01-01
Although many brand managers favor the use of celebrities in advertisements, others worry that celebrities overshadow the brand and thus impair brand recall. Practitioners refer to this overshadowing as the vampire effect, defined as a decrease in brand recall for an advertising stimulus...
Wouters, E.F.M.; Creutzberg, E.C.; Schols, A.M.W.J.
2002-01-01
Systemic effects in COPD. Wouters EF, Creutzberg EC, Schols AM. Department of Pulmonary Diseases, University Hospital Maastricht, PO Box 5800, 6202 AZ Maastricht, the Netherlands. ewo@ms-azm-3.azm.nl The pathogenesis and clinical manifestations of COPD are not restricted to pulmonary inflammation
Biological Effects of Radiation
International Nuclear Information System (INIS)
Jatau, B.D.; Garba, N.N.; Yusuf, A.M.; Yamusa, Y. A.; Musa, Y.
2013-01-01
In earlier studies, researchers aimed a single particle at the nucleus of the cell where DNA is located. Eighty percent of the cells shot through the nucleus survived. This contradicts the belief that if radiation slams through the nucleus, the cell will die. But the bad news is that the surviving cells contained mutations. Cells have a great capacity to repair DNA, but they cannot do it perfectly. The damage left behind in these studies from a single particle of alpha radiation doubled the damage that is already there. This proved, beyond a shadow of doubt, those there biological effects occur as a result of exposure to radiation, Radiation is harmful to living tissue because of its ionizing power in matter. This ionization can damage living cells directly, by breaking the chemical bonds of important biological molecules (particularly DNA), or indirectly, by creating chemical radicals from water molecules in the cells, which can then attack the biological molecules chemically. At some extent these molecules are repaired by natural biological processes, however, the effectiveness of this repair depends on the extent of the damage. The interaction of ionizing with the human body, arising either from external sources outside the body or from internal contamination of the body by radioactive materials, leads to the biological effects which may later show up as a clinical symptoms. Basically, this formed the baseline of this research to serve as a yardstick for creating awareness about radiation and its resulting effects.
Stereoelectronic Substituent Effects
DEFF Research Database (Denmark)
Bols, Mikael; Jensen, Henrik Helligsø
2006-01-01
An investigation was carried Out on the influence of the stereo-chemistry of substituents, particularly hydroxyl groups, on their electronic effects in piperidines, carbohydrates (pyranosides), and related compounds. Polar groups, such as OH, OR, and F, were found in the 3 and 4 position to be mu...
DEFF Research Database (Denmark)
Sandoval, J. H.; Bellotti, F. F.; Yamashita, M. T.
2018-01-01
The quantum mechanical three-body problem is a source of continuing interest due to its complexity and not least due to the presence of fascinating solvable cases. The prime example is the Efimov effect where infinitely many bound states of identical bosons can arise at the threshold where the tw...
Analgesic effects of melatonin
DEFF Research Database (Denmark)
Wilhelmsen, Michael; Amirian, Ilda; Reiter, Russel J
2011-01-01
has not been clarified. The effects may be linked to G(i) -coupled melatonin receptors, to G(i) -coupled opioid μ-receptors or GABA-B receptors with unknown downstream changes with a consequential reduction in anxiety and pain. Also, the repeated administration of melatonin improves sleep and thereby...
DEFF Research Database (Denmark)
Hansen, Mie Østergaard
annoyances and the objective measurements were analysed. Persons suffering from tinnitus behaved differently than person without tinnitus. The latter group showed significant relations between the measured occlusion effect, hearing loss and the personal of occlusion. The actual sensation level is also...
Fina, Allan de
1992-01-01
Explains how elementary teachers can help students understand onomatopoeia, suggesting that they define onomatopoeia, share examples of it, read poems and have students discuss onomatopoeic words, act out common household sounds, write about sound effects, and create choral readings of onomatopoeic poems. Two appropriate poems are included. (SM)
Pleiotropic effects of incretins
Directory of Open Access Journals (Sweden)
Vishal Gupta
2012-01-01
Full Text Available Drugs that augment the incretin system [glucagon like peptide (GLP agonists and dipeptidyl peptidase-4 (DPP-4 inhibitors] represent a novel class of anti-hyperglycemic agents that have shown to improve the health and survival of beta-cells (improvement in postprandial hyperglycemia and suppress glucagon (improvement in fasting hyperglycemia. The incretins represent a large family of molecules referred to as the "glucagon superfamily of peptide hormones" of which more than 90% of the physiological effects of incretins are accomplished by GLP-1 7-37 and GLP1 7-36 amide and gastric insulinotropic peptide (GIP. GLP-1 mediates its effects via the GLP-1 receptor, which has a wide tissue distribution [pancreas, lung, heart, vascular smooth muscle cells, endothelial cells, macrophages and monocytes, kidney, gastrointestinal tract (stomach and intestine, central nervous system (neoortex, cerebellum, hypothalamus, hippocampus, brainstem nucleus tractus solitarius and peripheral nervous system]. This would imply that the incretin system has effects outside the pancreas. Over time data has accumulated to suggest that therapies that augment the incretin system has beneficial pleiotrophic effects. The incretins have shown to possess a cardiac-friendly profile, preserve neuronal cells and safeguard from neuronal degeneration, improve hepatic inflammation and hepatosteatosis, improve insulin resistance, promote weight loss and induce satiety. There is growing evidence that they may also be renoprotective promoting wound healing and bone health.
Radioprotective effect of interferon
Energy Technology Data Exchange (ETDEWEB)
Zasukhina, G.
1984-12-18
A cycle of experiments performed jointly with associations of the Moscow Engineering Physics Institute reportedly demonstrated that interferons protect human cells cultivated in a test tube against the action of fast neutrons and gamma radiation. Cells treated in advance with interferon not only survived irradiation but were almost totally protected against harmful effects of fast neutrons on the structure of chromosomes, according to the author. She mentions that the laboratory has also been studying effects produced on cells by compounds of heavy metals and other chemical compounds, including ones which cause breaks in the DNA molecule. Interferon's ability to protect cells against effects of chemical compounds has been studied in this connection. Another direction of the laboratory's work is research on interferon's effects on blood cells of persons suffering from certain hereditary diseases in which restorative processes of cells are impaired. The purpose of this is to develop courses of treatment which will not cause irreversible damages to chromosomes, the author explains. Interferon has been found to stimulate the reparation systems of cells in cases of Marfan's syndrome, for example.
Effective Classroom Management
Mansor, Azlin Norhaini; Eng, Wong Kim; Rasul, Mohamad Sattar; Hamzah, Mohd Izham Mohd; Hamid, Aida Hanim A.
2012-01-01
This paper attempts to explore and identify the characteristics of an effective teacher who teaches English as a second language to 10 year old students from different ethnics, various social economic background and multi-level language ability, at a private primary school in Malaysia. The study focused on classroom management using a case study…
International Nuclear Information System (INIS)
Gilbert, E.S.
1989-01-01
Late effects are by definition effects that occur at least one year, and in most cases decades, after the time of exposure. The late effects considered in this chapter are limited to latent cancer incidence and mortality, and benign thyroid disease. A model is provided for estimating risks of late effects resulting from the radiation exposure likely to be received in the event of a nuclear power plant accident. It is assumed that exposure to high-LET radiation would be negligible in such an accident, and thus only risks from low-LET exposure are evaluated. Separate estimates are provided for risks of leukemia, bone cancer, lung cancer, gastrointestinal cancers, thyroid cancer, skin cancer, and the residual group of all other cancers; estimates of leukemia and other cancers due to in utero exposure are also provided. Risks are expressed in absolute terms as the number of cancer deaths (or cases) per million persons exposed to a particular dose. Because the time of death is also important in assessing the impact of an accident, and because the quality of life after the occurrence of cancer will often be reduced, the number of years of life lost and the number of years of life lived after the occurrence of cancer are also estimated
Radiation effects on lymphocytes
International Nuclear Information System (INIS)
Roser, B.
1976-01-01
This review of the ontogeny of lymphocyte populations concentrates on sites of production, rates of production, and the factors governing the differentiation and longevity of the various lymphocyte pools. The physiology of the lymphocyte pools is described with particular emphasis on recirculation from blood to lymph through lymphoid tissues. The separate routes of recirculation of both thymus-derived and nonthymus-derived lymphocytes and the possible anatomical sites and mechanisms of lymphocyte cooperation are discussed. Radiation effects on lymphocyte populations are divided into two sections. First, the effects of whole-body irradiation on the total lymphocyte pools are discussed including the differential effects of irradiation on T lymphocytes, B lymphocytes, lymphoblasts, and plasma cells. The differential sensitivity of various types of immune response is correlated, where possible, with the differential sensitivity of the lymphocyte types involved. Second, experimental attempts to selectively deplete discrete subpopulations of the total lymphocyte pools, e.g., recirculating cells, are briefly discussed with particular emphasis on studies on the effects of the localization of radionuclides in lymphoid tissue
Leadership Effectiveness and Gender
1999-04-01
Historical Conclusions.............................................................................................7 CONTINGENCY LEADERSHIP THEORIES ... leadership and looks at some historical background information relating to the more common theories that relate to leadership and effectiveness. It also...delves into some of the more traditional leadership theories as well as some of the more modern day theories and attempts to identify why there is still
DEFF Research Database (Denmark)
Cornean, Horia; Nenciu, Gheorghe
2009-01-01
This paper is the second in a series revisiting the (effect of) Faraday rotation. We formulate and prove the thermodynamic limit for the transverse electric conductivity of Bloch electrons, as well as for the Verdet constant. The main mathematical tool is a regularized magnetic and geometric...
DEFF Research Database (Denmark)
Pedersen, Lars
system and change its dynamic behavior and its dynamic characteristics. When predicting structural vibrations it is not common to account for the passive crowd, but the paper will illustrate effects of the presence of a passive croud on structural behavior. Numerical and experimental results...
Indian Academy of Sciences (India)
Soon after the discovery of the cosmic back- ground radiation, Zeldovich and Sunyaev pro- posed that hot gas in galaxy clusters should cast a faint shadow because of the interaction be- tween energetic electrons and the radiation pho- tons. Sunayev{Zeldovich effect is now routinely observed, and it has become an ...
Czech Academy of Sciences Publication Activity Database
Nagaosa, N.; Sinova, Jairo; Onoda, S.; MacDonald, A. H.; Ong, N. P.
2010-01-01
Roč. 82, č. 2 (2010), s. 1539-1592 ISSN 0034-6861 Institutional research plan: CEZ:AV0Z10100521 Keywords : anomalous Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 51.695, year: 2010
Effects of ionizing radiations
International Nuclear Information System (INIS)
Gaussens, G.
1984-08-01
After recalling radiation-matter interaction, influence on radiation effects of chemical composition, structure, irradiation atmosphere, dose rate, temperature of organic materials and evolution of electrical, mechanical and physical properties are reviewed. Then behaviour under irradiation of main organic materials: elastomers, thermoplastics, thermosetting plastics, oils and paints are examined. 68 refs [fr
Problems in photoradiation effects
International Nuclear Information System (INIS)
Milinchuk, V.K.
1986-01-01
This paper discusses the most interesting photoradiation effects observed in recent years and directs attention to problems whose solution has a bearing on progress in photoradiation chemistry, and which also are significant for divisions of modern physical chemistry such as the kinetics and mechanisms of elementary processes in solid organic materials, the radiation resistance of organic materials, and aging in polymers
Physiological Effects of Training.
1985-06-25
glycolysis and ’" 1,20,32 glycogenolysis along with oxidation of carbohydrates. This is associated with increases that have been demonstrated for high energy...The effects of length and stimulus rate on isometric tension in the cat soleus muscle. J Physiol 204:443-460, 1969 113. Sale DG, McDougall JD, Upton
Tunnelling Effects in Chemistry
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 19; Issue 2. Tunnelling Effects in Chemistry: Molecules in the Strange Quantum World. Sharmistha Karmakar Deepthi Jose Ayan Datta. General Article Volume 19 Issue 2 February 2014 pp 160-174 ...
Koomen, Elsje Rosalie
2010-01-01
Cutaneous melanoma is the most aggressive form of skin cancer and its incidence among Caucasian populations has increased whereas mortality rates are stabilizing or decreasing. The total burden of melanoma is expected to be increasing. As effective treatment options for advanced melanoma are
Multimodal news framing effects
Powell, T.E.
2017-01-01
Visuals in news media play a vital role in framing citizens’ political preferences. Yet, compared to the written word, visual images are undervalued in political communication research. Using framing theory, this thesis redresses the balance by studying the combined, or multimodal, effects of visual
Educator Effectiveness Administrative Manual
Pennsylvania Department of Education, 2014
2014-01-01
The goal of this manual is to provide guidance in the evaluation of educators, highlight critical components of effectiveness training, and offer opportunities for professional growth. The term "educator" includes teachers, all professional and temporary professional employees, education specialists, and school administrators/principals.…
Tomic, W.
2008-01-01
Before the cognitive shift in educational psychology research on teaching practices that bring about the desired learning outcomes on the part of the students was dominated by the process-product research program. The findings of this confirmative research approach show that an effective lesson may
Qualities of Effective Principals
Stronge, James H.; Richard, Holly B.; Catano, Nancy
2008-01-01
You know how important principals are in advancing student achievement and school success, but it's not been exactly clear which components of the principal's job are the highest priority... until now. Following on the results-based approach from the ASCD best-seller "Qualities of Effective Teachers", James Stronge and his coauthors…
Akkermans, H.A.; Voss, C.
2013-01-01
Purpose This paper sets out to explore whether and how the bullwhip effect, as found in product supply chains, might also manifest itself in services, as well as what policies can be successful for mitigating it. Design/methodology/approach A combination of analytic methods was used—inductive case
Unconscious advertising effects
Moorman, M.; Belch, M.A.; Belch, G.E.
2011-01-01
Most traditional advertising effect models are based on the premise that advertising is attended to and processed consciously. However, recent neuroscientific research shows that most information is unconsciously attended to, processed, and stored in memory. The concept of unconscious processing is
Effective Nonverbal Communication.
Parratt, Smitty
1995-01-01
Discusses the importance of understanding nonverbal communication in enhancing the personal and work relationships of interpreters and increasing their effectiveness in meeting the needs of customers. Discusses the mystique of body language, cultural variation in the use of gestures, the stages of an encounter, interpreting gesture clusters, and…
Edge effects in magnetoplasmas
Suttorp, L.G.; Kraeft, W.D.; Schlanges, M.
1996-01-01
Edge effects in magnetized charged-particle systems are discussed with the help of a multiple-reflection expansion for the Green function. The profiles of the density and the electric current are determined both for the non-degenerate and the highly degenerate case. The asymptotic form of the
Directory of Open Access Journals (Sweden)
Andrei A. Fedoseev
2014-01-01
Full Text Available The article analyzes effective electronic tutorials creation and application based on the theory of pedagogy. Herewith the issues of necessary electronic tutorial functional, ways of the educational process organization with the use of information and communication technologies and the logistics of electronic educational resources are touched upon.
Kok, Akke; Middelaar, van C.E.; Engel, B.; Knegsel, van A.T.M.; Hogeveen, H.; Kemp, B.; Boer, de I.J.M.
2016-01-01
To compare milk yields between cows or management strategies, lactations are traditionally standardized to 305-d yields. The 305-d yield, however, gives no insight into the combined effect of additional milk yield before calving, decreased milk yield after calving, and a possible shorter calving
Gudder, Stan
2004-08-01
We define a special type of additive map J on an effect algebra E called a compression. We call J(1) the focus of J and if p is the focus of a compression then p is called a projection. The set of projections in E is denoted by P(E). A compression J is direct if J( a) ≤ a for all a ɛ E. We show that direct compressions are equivalent to projections onto components of cartesian products. An effect algebra E is said to be compressible if every compression on E is uniquely determined by its focus and every compression on E has a supplement. We define and characterize the commutant C(p) of a projection p and show that a compression with focus p is direct if and only if C(p) = E. We show that P(E) is an orthomodular poset. It is proved that the cartesian product of effect algebras is compressible if and only if each component is compressible. We then consider compressible sequential effect algebras, Lüders maps and conditional probabilities.
Flowers, William L., Jr.; Harris, John B.
1981-01-01
The multiplier effect is discussed as it applies to the field of continuing education. The authors' main point is that one grant or contract can, and should, be used as the basis for building organizational competencies and capabilities that will secure other funds. (Author/CT)
[Papillomavirus vaccines: adverse effects].
Bayés, Maria E; Valero, Edith; Valero, Edith Gil; Gutiérrez, Herance; Martín Zafra, Antonia; Valverde Caballero, Inocencia; Aizpurua Galdeano, María Pilar
2011-11-01
The Health Department of Catalunya laun- ched the first vaccination campaign against human papillo- mavirus (HPV) in the 2008-09 school year This study des- cribes the side effects of HPV vaccine and compared them with those of the vaccine against Hepatitis. This is a prospective observational study Nurses of our primary health centre went to the area's schools to administer the HPV vaccine and hepatitis vaccine (when necessary). Afterwards, between 24 to 72 hours, they went back to schools in order to control the adverse effects. The frequency of general symptoms (syn- cope, fever, headache, muscle aches, malaise) was less than 5% with the first two doses. With the third, 9.8% of girls referred headache. Pain was the most common local symptom: 28.3% of girls reported pain with the first dose, 53.4% with the second and 53.6% with the third. Local reactions appear more often with HPV than with hepatitis vaccine, especially in the second and third doses (McNemar test p HPV vaccine was generally well tolerated. General side effects were rare. Local symptoms were com- mon and increased with each new dose. The vaccine against hepatitis produced fewer side effects.
Effective magnetic Hamiltonians
Czech Academy of Sciences Publication Activity Database
Drchal, Václav; Kudrnovský, Josef; Turek, I.
2013-01-01
Roč. 26, č. 5 (2013), s. 1997-2000 ISSN 1557-1939 R&D Projects: GA ČR GA202/09/0775 Institutional support: RVO:68378271 Keywords : effective magnetic Hamiltonian * ab initio * magnetic structure Subject RIV: BE - Theoretical Physics Impact factor: 0.930, year: 2013
The Negative Repetition Effect
Mulligan, Neil W.; Peterson, Daniel J.
2013-01-01
A fundamental property of human memory is that repetition enhances memory. Peterson and Mulligan (2012) recently documented a surprising "negative repetition effect," in which participants who studied a list of cue-target pairs twice recalled fewer targets than a group who studied the pairs only once. Words within a pair rhymed, and…
... by finding a way to relax—listening to music, doing yoga or stretching exercises, taking a walk in the woods or on the beach, or watching a movie marathon on television. Effectively relieving stress will help contribute to the ultimate goal of ...
Wickman, Jerry L.; Kundu, Nikhil K.
1996-01-01
This laboratory exercise seeks to develop a cost effective prototype development. The exercise has the potential of linking part design, CAD, mold development, quality control, metrology, mold flow, materials testing, fixture design, automation, limited parts production and other issues as related to plastics manufacturing.
Directory of Open Access Journals (Sweden)
R. Hentschke
2017-04-01
Full Text Available Measurements of the storage modulus, μ', vs. strain amplitude, u, for highly filled rubbers exhibit a pronounced decrease of μ' with increasing u. Unfilled rubbers do not show this so called Payne effect. Even though the effect is known since the 1940s, it continues to play a significant role in the research community focusing on rubber materials in general and automobile tires in particular. The key problem is the elucidation of the dependence of the Payne effect on the chemical composition of the rubber material. Based on a scaling approach we derive the functional form μ' (u,T – μ'(∞,T ∝ (1 – (D/du–(σ –df + 1g(T, where the parameters D/d and σ – df + 1 are directly related to the filler network structure. In addition, we explain the temperature dependence of the Payne effect, g(T, in terms of a distribution of activation energies corresponding to different types of filler-filler interactions. Finally, the model is extended to describe the attendant amplitude dependence of the loss modulus.
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 15; Issue 11. The Placebo Effect. Vasant Natarajan. General Article Volume 15 Issue 11 November 2010 pp 1003-1008. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/015/11/1003-1008. Keywords. Placebo ...
Haemodynamic effects of eating
DEFF Research Database (Denmark)
Høost, U; Kelbaek, H; Rasmusen, H
1996-01-01
1. The purpose of this study was to investigate the effect of fractional meal stimulation on postprandial haemodynamic changes, the possible correlation between these changes and the potential mediating role of circulating catecholamines and insulin. 2. Healthy young subjects were studied before ...
Tunnelling Effects in Chemistry
Indian Academy of Sciences (India)
IAS Admin
GENERAL ⎜ ARTICLE. Tunnelling Effects in Chemistry. Molecules in the Strange Quantum World. Sharmistha Karmakar, Deepthi Jose and Ayan Datta. (left) Sharmistha Karmakar is doing her PhD in the group of. Ayan Datta, IACS,. Kolkata. Her research interests are modelling molecules with strong optical absorbtion and.
African Journals Online (AJOL)
Students in universities and colleges commonly use khat, cigarette, coffee and other substances to get mental alertness. The objective of this ... substance use and its effect on academic achievement of students in Jimma University. METHODS: A cross ... cannabis or marihuana and khat (2, 3). Reports showed that these ...
Antioxidant effects of carotenoids
Bast, A.; Haenen, G.R.M.M.; Berg, R. van den; Berg, H. van den
1998-01-01
Surprisingly, neither the precise pharmacological effect nor the toxicological profile is usually established for food components. Carotenoids are no exception in this regard. Only limited insight into the pharmacology and toxicology of carotenoids exists. It is known that the antioxidant action of
DEFF Research Database (Denmark)
Di Nucci, Ezio
2014-01-01
There are some interesting similarities between Aristotle’s ‘mixed actions’ in Book III of the Nicomachean Ethics and the actions often thought to be justifiable with the Doctrine of Double Effect. Here I analyse these similarities by comparing Aristotle’s examples of mixed actions with standard ...
Theory of Effectiveness Measurement
2006-09-01
Operations Research Society, January 2003. Hill, Raymond , Gregory A. McIntyre, Thomas R. Tighe, and Richard K. Bullock, “Some Experiments with Agent...Measurement, Physica-Verlag, Wurzburg, 1971. Pinker, Aron , Aryeh H. Samuel, and Robert Batcher, “On Measures of Effectiveness,” PHALANX, pp 8-12
Brain effects of melanocortins.
Bertolini, Alfio; Tacchi, Raffaella; Vergoni, Anna Valeria
2009-01-01
The melanocortins (alpha, beta and gamma-melanocyte-stimulating hormones: MSHs; adrenocorticotrophic hormone: ACTH), a family of pro-opiomelanocortin (POMC)-derived peptides having in common the tetrapeptide sequence His-Phe-Arg-Trp, have progressively revealed an incredibly wide range of extra-hormonal effects, so to become one of the most promising source of innovative drugs for many, important and widespread pathological conditions. The discovery of their effects on some brain functions, independently made by William Ferrari and David De Wied about half a century ago, led to the formulation of the term "neuropeptide" at a time when no demonstration of the actual production of peptide molecules by neurons, in the brain, was still available, and there were no receptors characterized for these molecules. In the course of the subsequent decades it came out that melanocortins, besides inducing one of the most complex and bizarre behavioural syndromes (excessive grooming, crises of stretchings and yawnings, repeated episodes of spontaneous penile erection and ejaculation, increased sexual receptivity), play a key role in functions of fundamental physiological importance as well as impressive therapeutic effects in different pathological conditions. If serendipity had been an important determinant in the discovery of the above-mentioned first-noticed extra-hormonal effects of melanocortins, many of the subsequent discoveries in the pharmacology of these peptides (feeding inhibition, shock reversal, role in opiate tolerance/withdrawal, etc.) have been the result of a planned research, aimed at testing the "pro-nociceptive/anti-nociceptive homeostatic system" hypothesis. The discovery of melanocortin receptors, and the ensuing synthesis of selective ligands with agonist or antagonist activity, is generating completely innovative drugs for the treatment of a potentially very long list of important and widespread pathological conditions: sexual impotence, frigidity
2011-01-01
Cannabis, Cannabis sativa L., is used to produce a resin that contains high levels of cannabinoids, particularly delta9-tetrahydrocannabinol (THC), which are psychoactive substances. Although cannabis use is illegal in France and in many other countries, it is widely used for its relaxing or euphoric effects, especially by adolescents and young adults. What are the adverse effects of cannabis on health? During consumption? And in the long term? Does cannabis predispose users to the development of psychotic disorders? To answer these questions, we reviewed the available evidence using the standard Prescrire methodology. The long-term adverse effects of cannabis are difficult to evaluate. Since and associated substances, with or without the user's knowledge. Tobacco and alcohol consumption, and particular lifestyles and behaviours are often associated with cannabis use. Some traits predispose individuals to the use of psychoactive substances in general. The effects of cannabis are dosedependent.The most frequently report-ed adverse effects are mental slowness, impaired reaction times, and sometimes accentuation of anxiety. Serious psychological disorders have been reported with high levels of intoxication. The relationship between poor school performance and early, regular, and frequent cannabis use seems to be a vicious circle, in which each sustains the other. Many studies have focused on the long-term effects of cannabis on memory, but their results have been inconclusive. There do not * About fifteen longitudinal cohort studies that examined the influence of cannabis on depressive thoughts or suicidal ideation have yielded conflicting results and are inconclusive. Several longitudinal cohort studies have shown a statistical association between psychotic illness and self-reported cannabis use. However, the results are difficult to interpret due to methodological problems, particularly the unknown reliability of self-reported data. It has not been possible to
Cognitive Effects and Sedation.
Dhingra, Lara; Ahmed, Ebtesam; Shin, Jae; Scharaga, Elyssa; Magun, Maximilian
2015-10-01
Cognitive effects and sedation (CES) are prevalent in chronic nonmalignant pain populations receiving long-term opioid therapy and are among the most common reasons patients discontinue opioid use. In this narrative review, we describe the phenomenology, epidemiology, mechanisms, assessment, and management of opioid-related CES. We reviewed the empirical and theoretical literature on CES in opioid-treated populations with chronic pain. Data on long-term opioid therapy (≥ 3 months in duration) in chronic nonmalignant pain patients were sought. The phenomenology of CES includes: inattention, concentration difficulties, memory deficits, psychomotor dysfunction, perceptual distortions, and executive dysfunction and somnolence, sleep disorders, and lethargy. Deficits may be caused by unrelieved pain or opioid therapy alone, or from a combination of these and other factors. Mechanisms include central nervous system effects, for example, direct toxic effects on neurons resulting in decreased consciousness; direct effects on processing and reaction resulting in cognitive or psychomotor impairment, and inhibitory effects on cholinergic activity. Pharmacological management approaches may include opioid dose reduction and rotation or psychostimulant use. Nonpharmacological approaches may include cognitive-behavioral therapy, mindfulness-based stress reduction, acupuncture, exercise, and yoga. The most prevalent CES include: memory deficits (73-81%), sleep disturbance (35-57%), and fatigue (10%). At its most severe, extreme cognitive dysfunction can result in frank delirium and decreased alertness can result in coma. Emotional distress, sleep disorders, and other comorbidities and treatments can worsen CES, particularly among the elderly. Conclusions about the neuropsychological domains affected by opioids are limited due to the heterogeneity of studies and methodological issues. Wiley Periodicals, Inc.
... Your Health » Alcohol's Effects on the Body Alcohol's Effects on the Body Drinking too much – on a ... hours after getting drunk. Learn more about alcohol’s effects on the body. Follow Get Updates Donations Share ...
Effects of Medications on Voice
... ENTCareers Marketplace Find an ENT Doctor Near You Effects of Medications on Voice Effects of Medications on Voice Patient Health Information News ... replacement therapy post-menopause may have a variable effect. An inadequate level of thyroid replacement medication in ...
Zero-point energy of confined fermions
International Nuclear Information System (INIS)
Milton, K.A.
1980-01-01
A closed form for the reduced Green's function of massless fermions in the interior of a spherical bag is obtained. In terms of this Green's function, the corresponding zero-point or Casimir energy is computed. It is proposed that a resulting quadratic divergence can be absorbed by renormalizing a suitable parameter in the bag model (that is, absorbed by a contact term). The residual Casimir stress is attractive, but smaller than the repulsive Casimir stress of gluons in the model. The result for the total zero-point energy is in substantial disagreement with bag model phenomenological values
Regional Healthcare Effectiveness
Directory of Open Access Journals (Sweden)
Olga Vladimirovna Kudelina
2016-03-01
Full Text Available An evaluation of healthcare systems effectiveness of the regions of the Russian Federation (federal districts was conducted using the Minmax method based on the data available at the United Interdepartmental Statistical Information System. Four groups of components (i.e. availability of resources; use of resources; access to resources and medical effectiveness decomposed into 17 items were analyzed. The resource availability was measured by four indicators, including the provision of doctors, nurses, hospital beds; agencies providing health care to the population. Use of resources was measured by seven indicators: the average hospital stay, days; the average bed occupancy, days; the number of operations per 1 physician surgical; the cost per unit volume of medical care: in outpatient clinics, day hospitals, inpatient and emergency care. Access to the resources was measured by three indicators: the satisfaction of the population by medical care; the capacity of outpatient clinics; the average number of visits to health facility. The medical effectiveness was also measured by three indicators: incidence with the "first-ever diagnosis of malignancy"; life expectancy at birth, years; the number of days of temporary disability. The study of the dynamics of the components and indexes for 2008–2012 allows to indicate a multidirectional influence on the regional healthcare system. In some federal districts (e.g. North Caucasian, the effectiveness decreases due to resource availability, in others (South, North Caucasian — due to the use of resources, in others (Far Eastern, Ural — due to access to resources. It is found that the effectiveness of the healthcare systems of the federal districts differs significantly. In addition, the built matrix proves the variability the of effectiveness (comparison of expenditures and results of healthcare systems of the federal districts of the Russian Federation: the high results can be obtained at high costs
Benjamin, Arlin James; Bushman, Brad J
2018-02-01
In some societies, weapons are plentiful and highly visible. This review examines recent trends in research on the weapons effect, which is the finding that the mere presence of weapons can prime people to behave aggressively. The General Aggression Model provides a theoretical framework to explain why the weapons effect occurs. This model postulates that exposure to weapons increases aggressive thoughts and hostile appraisals, thus explaining why weapons facilitate aggressive behavior. Data from meta-analytic reviews are consistent with the General Aggression Model. These findings have important practical as well as theoretical implications. They suggest that the link between weapons and aggression is very strong in semantic memory, and that merely seeing a weapon can make people more aggressive. Copyright © 2017 Elsevier Ltd. All rights reserved.
International Nuclear Information System (INIS)
Espriu, D.
2003-01-01
QCD can be described in a certain kinematical regime by an effective string theory. This string must couple to background chiral fields in a chirally invariant manner, thus taking into account the true chirally non-invariant QCD vacuum. By requiring conformal symmetry of the string and the unitarity constraint on chiral fields we reconstruct the equations of motion for the latter ones. These provide a consistent background for the propagation of the string. By further requiring locality of the effective action we recover the Lagrangian of non-linear sigma model of pion interactions. The prediction is unambiguous and parameter-free. The estimated chiral structural constants of Gasser and Leutwyler fit very well the phenomenological values. (author)
Developing Effective Clinical Trainers
Directory of Open Access Journals (Sweden)
Kevin Khamarko
2012-05-01
Full Text Available Continuing education and training provides a means to improve performance among health care professionals (HCP. Research shows, however, that continuing professional education activities have inconsistent effects on HCP competence, performance, and patient health outcomes. Furthermore, the trainer’s role as a facilitator of knowledge translation (KT has been understudied. To understand how clinical trainers support their trainees in translating what they learned into practice, we conducted 16 in-depth interviews with expert trainers. These interviews yielded a variety of KT-enhancing strategies, including tailoring training activities to their trainees’ needs. In addition, participants recommended trainers familiarize themselves with their trainees’ work environments, be able to identify their knowledge deficits, and devote time to provide trainees with post-training support. Creating an effective training, one that leads to transfer, requires active planning, communication, and command of the training topic by skilled trainers.
Analgesic effects of melatonin
DEFF Research Database (Denmark)
Wilhelmsen, Michael; Amirian, Ilda; Reiter, Russel J
2011-01-01
Melatonin is an endogenous indoleamine, produced mainly by the pineal gland. Melatonin has been proven to have chronobiotic, antioxidant, antihypertensive, anxiolytic and sedative properties. There are also experimental and clinical data supporting an analgesic role of melatonin. In experimental...... studies, melatonin shows potent analgesic effects in a dose-dependent manner. In clinical studies, melatonin has been shown to have analgesic benefits in patients with chronic pain (fibromyalgia, irritable bowel syndrome, migraine). The physiologic mechanism underlying the analgesic actions of melatonin...... has not been clarified. The effects may be linked to G(i) -coupled melatonin receptors, to G(i) -coupled opioid µ-receptors or GABA-B receptors with unknown downstream changes with a consequential reduction in anxiety and pain. Also, the repeated administration of melatonin improves sleep and thereby...
Renormalization and effective lagrangians
International Nuclear Information System (INIS)
Polchinski, J.
1984-01-01
There is a strong intuitive understanding of renormalization, due to Wilson, in terms of the scaling of effective lagrangians. We show that this can be made the basis for a proof of perturbative renormalization. We first study renormalizability in the language of renormalization group flows for a toy renormalization group equation. We then derive an exact renormalization group equation for a four-dimensional lambda PHI 4 theory with a momentum cutoff. We organize the cutoff dependence of the effective lagrangian into relevant and irrelevant parts, and derive a linear equation for the irrelevant part. A lengthy but straightforward argument establishes that the piece identified as irrelevant actually is so in perturbation theory. This implies renormalizability. The method extends immediately to any system in which a momentum-space cutoff can be used, but the principle is more general and should apply for any physical cutoff. Neither Weinberg's theorem nor arguments based on the topology of graphs are needed. (orig.)
Magnetoviscous effects in ferrofluids
Odenbach, Stefan
2002-01-01
Suspensions of magnetic nanoparticles or ferrofluids can be effectively controlled by magnetic fields, which opens up a fascinating field for basic research into fluid dynamics as well as a host of applications in engineering and medicine. The introductory chapter provides the reader with basic information on the structure, and magnetic and viscous properties of ferrofluids. The bulk of this monograph is based on the author's own research activity and deals with ferrohydrodynamics, especially with the magnetoviscous effects. In particular, the author studies in detail the interparticle interactions so far often neglected but of great importance in concentrated ferrofluids. The basic theory and the most recent experimental findings are presented, making the book interesting reading for physicists or engineers interested in smart materials.
Measuring marketing effectiveness.
Gluckman, J; Michaelis, T
1987-09-01
The most frequent question about the marketing function in hospitals today is, What are we getting for our money? To answer this, marketing directors must convince the board first of the need for marketing, then of marketing's effectiveness. To measure marketing effectiveness, some basic needs are a staff, equipment, cooperation between departments, utilization data, and a research budget. Some steps to be followed include developing a marketing data base--consisting of demographic projections, demand projections, and market share--testing a marketing strategy through experimentation, documenting the expected results and measurement techniques, and calculating the expected return on investments. In dealing with those "impossible-to-measure" cases, such as a physician who is not advertising but finds that a competitor is, a decision tree can help determine whether to advertise and how much to spend by indicating what the return on investment might be.
The Creativity Passdown Effect
DEFF Research Database (Denmark)
Pries-Heje, Jan; Lee, Jong Seok; Baskerville, Richard
2015-01-01
Purpose – The purpose of this paper is to suggest that translating a design theory (DT) into practice (e.g. creating an instance design artifact (IDA)) is hardly straight-forward and requires substantial creativity. Specifically the authors suggest that adopting a DT embodies a creativity passdown...... effect in which the creative thinking of a team of design theorist(s) inherent in DT invokes a creative mind of a team of artifact instance designer(s) in creating an IDA. In this study, the authors empirically investigate the creativity passdown effect through an action case in which a DT (DT nexus...... designer team introducing a previously published DT as a basis for creating an IDA. Findings – The experience in the action case suggests that using a DT in creating an IDA may encourage design thinking, and in certain way increase its power and practical relevance by fostering the creative mind...
DEFF Research Database (Denmark)
Doucouliagos, Hristos; Paldam, Martin
The AEL (aid effectiveness literature) is econo¬metric studies of the macroeconomic effects of development aid. It contains about 100 papers of which 68 are reduced form estimates of theeffect of aid on growth in the recipient country. The raw data show that growth is unconnected to aid......, but the AEL has put so much structure on the data that all results possible have emerged. The present meta study considers both the best-set of the 68 papers and the all-set of 543 regressions published. Both sets have a positive average aid-growth elasticity, but it is small and insignificant: The AEL has...... betweenstudies is real. In particular, the aid-growth association is stronger for Asian countries, and the aid-growth association is shown to have been weaker in the 1970s....
Aerodynamic Leidenfrost effect
Gauthier, Anaïs; Bird, James C.; Clanet, Christophe; Quéré, David
2016-12-01
When deposited on a plate moving quickly enough, any liquid can levitate as it does when it is volatile on a very hot solid (Leidenfrost effect). In the aerodynamic Leidenfrost situation, air gets inserted between the liquid and the moving solid, a situation that we analyze. We observe two types of entrainment. (i) The thickness of the air gap is found to increase with the plate speed, which is interpreted in the Landau-Levich-Derjaguin frame: Air is dynamically dragged along the surface and its thickness results from a balance between capillary and viscous effects. (ii) Air set in motion by the plate exerts a force on the levitating liquid. We discuss the magnitude of this aerodynamic force and show that it can be exploited to control the liquid and even to drive it against gravity.
Electricity Distribution Effectiveness
Directory of Open Access Journals (Sweden)
Waldemar Szpyra
2015-12-01
Full Text Available This paper discusses the basic concepts of cost accounting in the power industry and selected ways of assessing the effectiveness of electricity distribution. The results of effectiveness analysis of MV/LV distribution transformer replacement are presented, and unit costs of energy transmission through various medium-voltage line types are compared. The calculation results confirm the viability of replacing transformers manufactured before 1975. Replacing transformers manufactured after 1975 – only to reduce energy losses – is not economically justified. Increasing use of a PAS type line for energy transmission in local distribution networks is reasonable. Cabling these networks under the current calculation rules of discounts for excessive power outages is not viable, even in areas particularly exposed to catastrophic wire icing.
Susceptibility to anchoring effects
Directory of Open Access Journals (Sweden)
Todd McElroy
2007-02-01
Full Text Available Previous research on anchoring has shown this heuristic to be a very robust psychological phenomenon ubiquitous across many domains of human judgment and decision-making. Despite the prevalence of anchoring effects, researchers have only recently begun to investigate the underlying factors responsible for how and in what ways a person is susceptible to them. This paper examines how one such factor, the Big-Five personality trait of openness-to-experience, influences the effect of previously presented anchors on participants' judgments. Our findings indicate that participants high in openness-to-experience were significantly more influenced by anchoring cues relative to participants low in this trait. These findings were consistent across two different types of anchoring tasks providing convergent evidence for our hypothesis.
Radiation Effects Research Foundation
International Nuclear Information System (INIS)
1979-01-01
The last day of March 1978 marked the completion of the first 3 years of operation of the Radiation Effects Research Foundation in Hiroshima and Nagasaki. RERF was established on 1 April 1975 as successor to the Atomic Bomb Casualty Commission which had been in continuous operation since 1947. This record of the first 3 years of operation consists of selected reports and other documents prepared in the course of conducting the business of RERF and includes a brief history, a late radiation effects that might be conducted at RERF. The wisdom and thought given to the research program and its operation by the Scientific Council and the Board of Directors is reflected in the minutes of their meetings which are included in the Appendix. (Mori, K.)