Lab-based limits on the Carroll-Field-Jackiw Lorentz-violating electrodynamics

The CPT-odd and Lorentz-violating Carroll-Field-Jackiw modification of electrodynamics is discussed and we study its effects on the energy spectrum of hydrogen, as well as in the generation of a momentum-dependent electric dipole moment for charged leptons. We also briefly comment on the possibility of the detection of Lorentz violation in measurements of vacuum birefringence in resonant cavities. The bounds found are based on local laboratory experimental limits and are not competitive with the ones coming from astrophysical considerations.Comment: Reviewed version in two columns (8 pages, 1 figure): small corrections. Matches the version accepted for publication (Phys. Rev. D

Lancret helices

Helical configurations of inhomogeneous symmetric rods with non-constant bending and twisting stiffness are studied within the framework of the Kirchhoff rod model. From the static Kirchhoff equations, we obtain a set of differential equations for the curvature and torsion of the centerline of the rod and the Lancret's theorem is used to find helical solutions. We obtain a free standing helical solution for an inhomogeneous rod whose curvature and torsion depend on the form of variation of the bending coefficient along the rod. These results are obtained for inhomogeneous rods without intrinsic curvature, and for a particular case of intrinsic curvature.Comment: 31 pages, 3 figure

Helical filaments with varying cross section radius

The tridimensional configuration and the twist density of helical rods with varying cross section radius are studied within the framework of the Kirchhoff rod model. It is shown that the twist density increases when the cross section radius decreases. Some tridimensional configurations of helix-like rods are displayed showing the effects of the nonhomogeneity considered here. Since the helix-like solutions of the nonhomogeneous rods do not present constant curvature and torsion a set of differential equations for these quantities is presented. We discuss the results and possible consequences.Comment: 10 pages and 5 figure

Circular and helical equilibrium solutions of inhomogeneous rods

Real filaments are not perfectly homogeneous. Most of them have various materials composition and shapes making their stiffnesses not constant along the arclength. We investigate the existence of circular and helical equilibrium solutions of an intrinsically straight rod with varying bending and twisting stiffnesses, within the framework of the Kirchhoff model. The planar ring equilibrium solution only exists for a rod with a given form of variation of the bending stiffness. We show that the well known circular helix is not an equilibrium solution of the static Kirchhoff equations for a rod with non constant bending stiffness. Our results may provide an explanation for the variation of the curvature seen in small closed DNAs immersed in a solution containing Zn^{2+}, and in the DNA wrapped around a nucleosome.Comment: 27 pages, 2 figure

A novel test of Lorentz violation in the photon sector with an LC circuit

In the presence of an external magnetic field, the Carroll-Field-Jackiw term introduces a displacement current proportional to the Lorentz-violating background that induces a time-dependent magnetic field. Axion-like particles or hidden photons could generate an analogous signal, potentially detectable with the set-up suggested by Sikivie, Tanner and Sullivan - a sensitive magnetometer coupled to a superconducting LC circuit. We show that a similar set-up, but with an externally driven pick-up loop whose area varies harmonically at $\sim$ Hz, can be used to probe the spatial components of the Lorentz-violating background to the level of $\lesssim 10^{-31}$ GeV. This is eight orders of magnitude more sensitive than previous laboratory-based limits.Comment: 6 pages, 1 figure, matches published versio

Is it possible to grow amorphous normal nanosprings ?

Nanosprings have been object of intense investigations in recent years. They can be classified as normal or binormal depending on the geometry of their cross-section. Normal amorphous nanosprings have not been observed experimentally up to now, and only recently the synthesis of a crystalline ZnO normal nanohelix has been reported. We discuss the shape of the catalyst in terms of the cross-sectional shape of the nanospring, and show that, within the vapor-liquid-solid model, the growth of amorphous normal nanospring is not energetically favoured.Comment: 12 pages, 6 figure

Effect of symmetry breaking on level curvature distributions

We derive an exact general formalism that expresses the eigenvector and the eigenvalue dynamics as a set of coupled equations of motion in terms of the matrix elements dynamics. Combined with an appropriate model Hamiltonian, these equations are used to investigate the effect of the presence of a discrete symmetry in the level curvature distribution. An explanation of the unexpected behavior of the data regarding frequencies of acoustic vibrations of quartz block is provided.Comment: 13 pages, 3 figure

Mechanical properties of amorphous nanosprings

Helical amorphous nanosprings have attracted particular interest due to their special mechanical properties. In this work we present a simple model, within the framework of the Kirchhoff rod model, for investigating the structural properties of nanosprings having asymmetric cross section. We have derived expressions that can be used to obtain the Young's modulus and Poisson's ratio of the nanospring material composite. We also address the importance of the presence of a catalyst in the growth process of amorphous nanosprings in terms of the stability of helical rods.Comment: 14 pages, 4 figure

The Schrodinger picture and the zero-point radiation

Dalibard, Dupont-Roc and Cohen-Tannoudji (J. Physique 43 (1982) 1617; 45 (1984) 637) used the Heisenberg picture to show that the atomic transitions, and the stability of the ground state, can only be explained by introducing radiation reaction and vacuum fluctuation forces. Here we consider the simple case of nonrelativistic charged harmonic oscillator, in one dimension, to investigate how to take into account the radiation reaction and vacuum fluctuation forces within the Schrodinger picture. We consider classical vacuum fields and large mass oscillator.Comment: 7 pages. To be published in "Quanta, Relativity and Electromagnetism: The Search for Unity in Physics", Proceedings of a Symposium in Honor of Jean-Pierre Vigier (Paris, September, 2003). Kluwer Academic Publisher

Lorentz violation in simple QED processes

We determine the effect of a CPT-even and Lorentz violating non-minimal coupling on the differential cross sections for some of the most important tree-level processes in QED, namely, Compton and Bhabha scatterings, as well as electron-positron annihilation. Experimental limits constraining the allowed deviation of the differential cross sections relative to pure QED allow us to place upper bounds on the Lorentz violating parameters. A constraint based on the decay rate of para-positronium is also obtained.Comment: Final version, includind suggestions of the referee. Published in PR