Publications (22)0 Total impact
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Article: Derivative expansion of the electromagnetic Casimir energy for two thin mirrors
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ABSTRACT: We extend our previous work on a derivative expansion for the Casimir energy, to the case of the electromagnetic field coupled to two thin, imperfect mirrors. The latter are described by means of vacuum polarization tensors localized on the mirrors. We apply the results so obtained to compute the first correction to the proximity force approximation to the static Casimir effect.03/2012; -
Article: Casimir Force for Absorbing Media in an Open Quantum System Framework: Scalar Model
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ABSTRACT: In this article we compute the Casimir force between two finite-width mirrors at finite temperature, working in a simplified model in 1+1 dimensions. The mirrors, considered as dissipative media, are modeled by a continuous set of harmonic oscillators which in turn are coupled to an external environment at thermal equilibrium. The calculation of the Casimir force is performed in the framework of the theory of quantum open systems. It is shown that the Casimir interaction has two different contributions: the usual radiation pressure from vacuum, which is obtained for ideal mirrors without dissipation or losses, and a Langevin force associated with the noise induced by the interaction between dielectric atoms in the slabs and the thermal bath. Both contributions to the Casimir force are needed in order to reproduce the analogous of Lifshitz formula in 1+1 dimensions. We also discuss the relation between the electromagnetic properties of the mirrors and the spectral density of the environment07/2011; -
Article: Quantum dissipative effects in moving imperfect mirrors: sidewise and normal motions
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ABSTRACT: 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 non-vanishing frictional force, even for a constant shifting speed.05/2011; -
Article: On the accuracy of the PFA: analogies between Casimir and electrostatic forces
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ABSTRACT: We present an overview of the validity of the Proximity Force Approximation (PFA) in the calculation of Casimir forces between perfect conductors for different geometries, with particular emphasis for the configuration of a cylinder in front of a plane. In all cases we compare the exact numerical results with those of PFA, and with asymptotic expansions that include the next to leading order corrections. We also discuss the similarities and differences between the results for Casimir and electrostatic forces.01/2009; -
Article: Decoherence induced by a fluctuating Aharonov-Casher phase
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ABSTRACT: Dipoles interference is studied when atomic systems are coupled to classical electromagnetic fields. The interaction between the dipoles and the classical fields induces a time-varying Aharonov-Casher phase. Averaging over the phase generates a suppression of fringe visibility in the interference pattern. We show that, for suitable experimental conditions, the loss of contrast for dipoles can be observable and almost as large as the corresponding one for coherent electrons. We analyze different trajectories in order to show the dependence of the decoherence factor with the velocity of the particles.09/2005; -
Article: Hertz potentials approach to the dynamical Casimir effect in cylindrical cavities of arbitrary section
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ABSTRACT: We study the creation of photons in resonant cylindrical cavities with time dependent length. The physical degrees of freedom of the electromagnetic field are described using Hertz potentials. We describe the general formalism for cavities with arbitrary section. Then we compute explicitly the number of TE and TM motion-induced photons for cylindrical cavities with rectangular and circular sections. We also discuss the creation of TEM photons in non-simply connected cylindrical cavities. Comment: 13 pages, 3 figures, revtex411/2004; -
Article: Model for resonant photon creation in a cavity with time dependent conductivity
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ABSTRACT: In an electromagnetic cavity, photons can be created from the vacuum state by changing the cavity's properties with time. Using a simple model based on a massless scalar field, we analyze resonant photon creation induced by the time-dependent conductivity of a thin semiconductor film contained in the cavity. This time dependence may be achieved by irradiating periodically the film with short laser pulses. This setup offers several experimental advantages over the case of moving mirrors. Comment: 9 pages, 1 figure. Minor changes. Version to appear in Phys. Rev. A04/2004; -
Article: Quantum electromagnetic field in a three dimensional oscillating cavity
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ABSTRACT: We compute the photon creation inside a perfectly conducting, three dimensional oscillating cavity, taking the polarization of the electromagnetic field into account. As the boundary conditions for this field are both of Dirichlet and (generalized) Neumann type, we analyze as a preliminary step the dynamical Casimir effect for a scalar field satisfying generalized Neumann boundary conditions. We show that particle production is enhanced with respect to the case of Dirichlet boundary conditions. Then we consider the transverse electric and transverse magnetic polarizations of the electromagnetic field. For resonant frequencies, the total number of photons grows exponentially in time for both polarizations, the rate being greater for transverse magnetic modes.06/2002; -
Article: One-loop graviton corrections to Maxwell’s equations
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ABSTRACT: We compute the graviton induced corrections to Maxwell’s equations in the one-loop and weak field approximations. The corrected equations are analogous to the classical equations in anisotropic and inhomogeneous media. We analyze in particular the corrections to the dispersion relations. When the wavelength of the electromagnetic field is much smaller than a typical length scale of the graviton two-point function, the speed of light depends on the direction of propagation and on the polarization of the radiation. In the opposite case, the speed of light may also depend on the energy of the electromagnetic radiation. We study in detail wave propagation in two special backgrounds: flat Robertson-Walker and static, spherically symmetric spacetimes. In the case of a flat Robertson-Walker gravitational background we find that the corrected electromagnetic field equations correspond to an isotropic medium with a time-dependent effective refractive index. For a static, spherically symmetric background the graviton fluctuations induce a vacuum structure which causes birefringence in the propagation of light.Phys. Rev. D. 03/2001; 63(8). -
Article: Resonant photon creation in a three dimensional oscillating cavity
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ABSTRACT: We analyze the problem of photon creation inside a perfectly conducting, rectangular, three dimensional cavity with one oscillating wall. For some particular values of the frequency of the oscillations the system is resonant. We solve the field equation using multiple scale analysis and show that the total number of photons inside the cavity grows exponentially in time. This is also the case for slightly off-resonance situations. Although the spectrum of a cavity is in general non equidistant, we show that the modes of the electromagnetic field can be coupled, and that the rate of photon creation strongly depends on this coupling. We also analyze the thermal enhancement of the photon creation. Comment: 13 pages. New section on off-resonance motion is included. To appear in Physical Review A12/2000; -
Article: Anomalies and symmetries of the regularized action
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ABSTRACT: We show that the Pauli-Villars regularized action for a scalar field in a gravitational background in 1+1 dimensions has, for any value of the cutoff M, a symmetry which involves non-local transformations of the regulator field plus (local) Weyl transformations of the metric tensor. These transformations, an extension to the regularized action of the usual Weyl symmetry transformations of the classical action, lead to a new interpretation of the conformal anomaly in terms of the (non-anomalous) Jacobian for this symmetry. Moreover, the Jacobian is automatically regularized, and yields the correct result when the masses of the regulators tend to infinity. In this limit the transformations, which are non-local in a scale of 1/M, become the usual Weyl transformation of the metric. We also present the example of the chiral anomaly in 1+1 dimensions. Comment: 13 pages, Latex03/2000; -
Article: Classicality of the order parameter during a phase transition
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ABSTRACT: We analyze the quantum to classical transition of the order parameter in second order phase transitions. We consider several toy models in non relativistic quantum mechanics. We study the dynamical evolution of a wave packet initially peaked around a local maximum of the potential using variational approximations and also exact numerical results. The influence of the environment on the evolution of the density matrix and the Wigner function is analyzed in great detail. We also discuss the relevance of our results to the analysis of phase transitions in field theory. In particular, we argue that previous results about classicality of the order parameter in O(N) models may be consequences of the large $N$ approximation. Comment: RevTex file, 15 pages, 19 ps figures. Minor changes, to appear in Physical Review D12/1999; -
Article: Quantum corrected geodesics
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ABSTRACT: We compute the graviton-induced corrections to the trajectory of a classical test particle. We show that the motion of the test particle is governed by an effective action given by the expectation value (with respect to the graviton state) of the classical action. We analyze the quantum corrected equations of motion for the test particle in two particular backgrounds: a Robertson Walker spacetime and a 2+1 dimensional spacetime with rotational symmetry. In both cases we show that the quantum corrected trajectory is not a geodesic of the background metric. Comment: LaTeX file, 15 pages, no figures04/1999; -
Article: Quantum corrections to the geodesic equation
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ABSTRACT: In this talk we will argue that, when gravitons are taken into account, the solution to the semiclassical Einstein equations (SEE) is not physical. The reason is simple: any classical device used to measure the spacetime geometry will also feel the graviton fluctuations. As the coupling between the classical device and the metric is non linear, the device will not measure the `background geometry' (i.e. the geometry that solves the SEE). As a particular example we will show that a classical particle does not follow a geodesic of the background metric. Instead its motion is determined by a quantum corrected geodesic equation that takes into account its coupling to the gravitons. This analysis will also lead us to find a solution to the so-called gauge fixing problem: the quantum corrected geodesic equation is explicitly independent of any gauge fixing parameter. Comment: Revtex file, 6 pages, no figures. Talk presented at the meeting "Trends in Theoretical Physics II", Buenos Aires, Argentina, December 199803/1999; -
Article: Creation of photons in an oscillating cavity with two moving mirrors
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ABSTRACT: We study the creation of photons in a one dimensional oscillating cavity with two perfectly conducting moving walls. By means of a conformal transformation we derive a set of generalized Moore's equations whose solution contains the whole information of the radiation field within the cavity. For the case of resonant oscillations we solve these equations using a renormalization group procedure that appropriately deals with the secular behaviour present in a naive perturbative approach. We study the time evolution of the energy density profile and of the number of created photons inside the cavity. Comment: LaTex file, 17 pages, 3 figures, uses epsf.sty10/1998; -
Article: Energy-momentum tensor for scalar fields coupled to the dilaton in two dimensions
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ABSTRACT: We clarify some issues related to the evaluation of the mean value of the energy-momentum tensor for quantum scalar fields coupled to the dilaton field in two-dimensional gravity. Because of this coupling, the energy-momentum tensor for the matter is not conserved and therefore it is not determined by the trace anomaly. We discuss different approximations for the calculation of the energy-momentum tensor and show how to obtain the correct amount of Hawking radiation. We also compute cosmological particle creation and quantum corrections to the Newtonian potential. Comment: 18 pages, RevTex, no figures. Some changes have been added. To appear in Physical Review D08/1998; -
Article: Exact CTP Renormalization Group Equation for the Coarse Grained Effective Action
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ABSTRACT: We consider a scalar field theory in Minkowski spacetime and define a coarse grained Closed Time Path (CTP) effective action by integrating quantum fluctuations of wavelengths shorter than a critical value. We derive an exact CTP renormalization group equation for the dependence of the effective action on the coarse graining scale. We solve this equation using a derivative expansion approach. Explicit calculation is performed for the OE 4 theory. We discuss the Electronic address: dalvit@df.uba.ar y Electronic address: fmazzi@df.uba.ar relevance of the CTP average action in the study of non-equilibrium aspects of phase transitions in quantum field theory. I. INTRODUCTION The study of phase transitions in Quantum Field Theory is of great interest in cosmology and particle physics. Cosmological inflationary models [1--3], the electroweak phase transition [4,5], the formation of chiral condensates [6--8], are clear examples of the very interesting problems related to phase trans...06/1998; -
Article: Influence functional in two dimensional dilaton gravity
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ABSTRACT: We evaluate the influence functional for two dimensional models of dilaton gravity. This functional is exactly computed when the conformal invariance is preserved, and it can be written as the difference between the Liouville actions on each closed-time-path branch plus a boundary term. From the influence action we derive the covariant form of the semiclassical field equations. We also study the quantum to classical transition in cosmological backgrounds. In the conformal case we show that the semiclassical approximation is not valid because there is no imaginary part in the influence action. Finally we show that the inclusion of the dilaton loop in the influence functional breaks conformal invariance and ensures the validity of the semiclassical approximation. Comment: 25 pages, RevTex, no figures. Minor changes has been added. To appear in Physical Review D12/1997; -
Article: Renormalization Group Approach to the Dynamical Casimir Effect
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ABSTRACT: In this paper we study the one dimensional dynamical Casimir effect. We consider a one dimensional cavity formed by two mirrors, one of which performs an oscillatory motion with a frequency resonant with the cavity. The naive solution, perturbative in powers of the amplitude, contains secular terms. Therefore it is valid only in the short time limit. Using a renormalization group technique to resum these terms, we obtain an improved analytical solution which is valid for longer times. We discuss the generation of peaks in the density energy profile and show that the total energy inside the cavity increases exponentially.10/1997; -
Article: Geodesics, gravitons and the gauge fixing problem
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ABSTRACT: When graviton loops are taken into account, the background metric obtained as a solution to the one-loop corrected Einstein equations turns out to be gauge fixing dependent. Therefore it is of no physical relevance. Instead we consider a physical observable, namely the trajectory of a test particle in the presence of gravitons. We derive a quantum corrected geodesic equation that includes backreaction effects and is explicitly independent of any gauge fixing parameter. Comment: 21 pages, no figures, RevTeX08/1997;
Top co-authors
Institutions
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1998–2001
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Buenos Aires Ciudad
Buenos Aires, Buenos Aires F.D., Argentina
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1997
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Universidad de Buenos Aires
- Departamento de Física
Buenos Aires, Buenos Aires F.D., Argentina
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