M. V. Cougo-Pinto

BOSONIC CASIMIR EFFECT IN EXTERNAL MAGNETIC FIELD

We compute the influence of an external magnetic field on the Casimir energy of a massive charged scalar field confined between two parallel infinite plates. For this case the obtained result shows that the magnetic field inhibits the Casimir effect.

QED vacuum between a conducting and a permeable plate

We consider the photon field between an unusual configuration of infinite parallel plates, namely: a perfectly conducting plate () and an infinitely permeable one (µ). After quantizing the vector potential in the Coulomb gauge, we obtain explicit expressions for the vacuum expectation values of field operators of the form EiEj0 and BiBj0. These field correlators allow us to re-obtain the Casimir effect for this set-up and to discuss the light velocity shift caused by the presence of plates (Scharnhorst effect: Scharnhorst (1990 Phys. Lett. B 236 354), Barton (1990 Phys. Lett. B 237 559), Barton and Scharnhorst (1993 J. Phys. A: Math. Gen. 26 2037)) for both scalar and spinor QED.We consider the photon field between an unusual configuration of infinite parallel plates: a perfectly conducting plate (ǫ → ∞) and an infinitely permeable one μ → ∞). After quantizing the vector potential in the Coulomb gauge, we obtain explicit expressions for the vacuum expectation values of field operators of the form < ÊiÊj >0 and < B̂iB̂j >0. These field correlators allow us to reobtain the Casimir effect for this set up and to discuss the light velocity shift caused by the presence of plates (Scharnhorst effect [1, 2, 3]) for both scalar and spinor QED. PACS numbers: 11.10.-z, 11.10.Mn

The speed of light in confined QED vacuum: faster or slower than c?

Abstract We consider the propagation of light in the QED vacuum between an unusual pair of parallel plates, namely: a perfectly conducting one ( ϵ →∞) and an infinitely permeable one ( μ →∞). For weak fields and in the soft photon approximation we show that the speed of light for propagation normal to the plates is smaller than its value in unbounded space (in contrast to the original Scharnhorst effect [K. Scharnhorst, Phys. Lett. B 236 (1990) 354, G. Barton, Phys. Lett. B 237 (1990) 559, G. Barton, K. Scharnhorst, J. Phys. A 26 (1993) 2037]).

Casimir effect and creation of radiation in confined κ-deformed electrodynamics

Abstract We consider a κ -deformed electrodynamics in a sourceless situation and under boundary conditions dictated by the presence of two parallel conducting plates. Using the κ -deformed dispersion relation we compute the corresponding zero-point energy. The result is reduced to quadratures of elementary functions and has a real as well as an imaginary part due to the simultaneous effect of κ -deformation and boundary condition. The imaginary part exhibits a remarkable property of κ -deformed theories: the creation of radiation due to boundary conditions. The real part gives corrections to the Casimir effect due to the κ -deformation and is in agreement with previously known results. Real and imaginary parts also confirms a conjecture originated from a calculation of one-loop effective action for a massive scalar field.

Magnetic permeability in constrained fermionic vacuum

Abstract We obtain using Schwingers proper time approach the Casimir-Euler-Heisenberg effective action of fermion fluctuations for the case of an applied magnetic field. We implement here the compactification of one space dimension into a circle through anti-periodic boundary condition. Aside of higher order non-linear field effects we identify a novel contribution to the vacuum permeability. These contributions are exceedingly small for normal electromagnetism due to the smallness of the electron Compton wavelength compared to the size of the compactified dimension, if we take the latter as the typical size of laboratory cavities, but their presence is thought provoking, also considering the context of strong interactions.

Creation of matter and radiation from deformation of Poincaré invariance

Abstract We show that matter and radiation can be created in the confined vacuum of a quantum field whose space-time symmetries are given by the quantum algebra obtained by κ-deformation of the Poincare algebra. The creation rate goes to zero when the confinement or the deformation disappear.

Past and future blurring at fundamental length scale.

We obtain the κ-deformed versions of the retarded and advanced Green functions and show that their causality properties are blurred in a time interval of the order of a length parameter q=1/(2κ). The functions also indicate a smearing of the light cone. These results favor the interpretation of q as a fundamental length scale below which the concept of a point in space-time should be substituted by the concept of a fuzzy region of radius q, as proposed long ago by Heisenberg.

The influence of an external magnetic field on the fermionic Casimir effect

The influence of an external constant uniform magnetic field on the Casimir energy associated with a Dirac field under antiperiodic boundary condition is computed using Schwingers method. The obtained result shows that the magnetic field enhances the fermionic Casimir energy, in oposition to the bosonic Casimir energy which is inhibited by the magnetic field.

Schwinger's formula for the Casimir effect at finite temperature

We show that the approach proposed by Schwinger to compute the Casimir energy at zero temperature in the context of source theory, can be generalized to include temperature effects. We use a regularization prescription based on analytical continuation methods which allows full employment of the Epstein function techniques. This is to be compared with Schwingers original regularization method by means of the Poisson summation formula.

Schwinger's method for the fermionic Casimir effect

The Casimir energy of a massive Dirac field confined between two parallel infinite plates is computed using a method proposed by Schwinger. The massless case is obtained as a limit of the massive case. The boundary conditions are those of zero current through the plates, as inspired by quark confinement in the MIT bag model for hadrons. We use an analytical continuation method of regularization which allows the employment of Epstein function techniques. The calculation using Schwingers original regularization by a cutoff in proper time is also outlined.