Browsing by Author "Escobar, C. A."
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- Casimir effect in presence of spontaneous Lorentz symmetry breakingPublication . Escobar, C. A.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.
- Cosmic-ray fermion decay through tau-antitau emission with Lorentz violationPublication . Escobar, C. A.; Noordmans, J. P.; Potting, R.We study CPT and Lorentz violation in the tau-lepton sector of the Standard Model in the context of the Standard-Model Extension, parametrized by a coefficient which is thus far unbounded by experiment. We show that any nonzero value of this coefficient implies that, for sufficiently large energies, Standard Model fermions become unstable against decay due to the emission of a pair of tau-antitau leptons. We calculate the induced fermion energy-loss rate and we deduce the first limit on the Lorentz- and CPT-violation coefficient.
- Degenerate behavior in nonlinear vacuum electrodynamicsPublication . Escobar, C. A.; Potting, RobertusWe study nonlinear vacuum electrodynamics in the first-order formulation proposed by Plebanski. We analyze in detail the equations of motion, and identify conditions for which a singularity can occur for the time derivative of one of the field components. The resulting degenerate behavior can give rise to a shock wave with a reduction of the local number of degrees of freedom. We use an example model to illustrate the occurrence of superluminal propagation for field values approaching the singularity.
- Nonlinear vacuum electrodynamics and spontaneous breaking of Lorentz symmetryPublication . Escobar, C. A.; Potting, RobertusWe study spontaneous breaking of Lorentz symmetry in nonlinear vacuum electrodynamics. Using a first-order formulation of the latter proposed by Plebanski, we apply a Dirac constraint analysis and derive an effective Hamiltonian. We show that there exists a large class of potentials for which the effective Hamiltonian is bounded from below, while at the same time possessing local minima in which the field strength acquires a nonzero vacuum expectation value, thereby breaking Lorentz invariance spontaneously. These possible vacua can be classified in four classes, depending on the way Lorentz symmetry is broken. We show that the small field fluctuations around these vacua involve modes for which the dynamics can develop degeneracies, resulting in shock-wave-like and/or superluminal motion. Finally, we study the physical applicability of these models, and show how the Lorentz breaking vacua might in principle be detected by coupling the model to a suitable external current, or to gravity.
- Vector models with spontaneous Lorentz-symmetry breakingPublication . Escobar, C. A.; Urrutia, L. F.Even though models with spontaneous Lorentz-symmetry breaking also damage gauge invariance, an interesting possibility that emerges is to interpret the resultant massless Goldstone bosons as the gauge bosons of the related gauge theory. In this contribution we review the conditions under which gauge invariance is recovered from such models. To illustrate our general approach we consider the classical Abelian bumblebee and Nambu models. In the former case we prove its connection with electrodynamics by a procedure which takes proper care of the gauge-fixing conditions. In the case of the Abelian Nambu model its relation with electrodynamics is established in such a way that the generalization to the non-Abelian case is straightforward.