Universal behavior of dispersion forces between two dielectric plates in the low-temperature limit

The universal analytic expressions in the limit of low temperatures (short separations) are obtained for the free energy, entropy and pressure between the two parallel plates made of any dielectric. The analytical proof of the Nernst heat theorem in the case of dispersion forces acting between dielectrics is provided. This permitted us to formulate the stringent thermodynamical requirement that must be satisfied in all models used in the Casimir physics.Comment: 6 pages, iopart.cls is used, to appear in J. Phys. A (special issue: Proceedings of QFEXT05, Barcelona, Sept. 5-9, 2005

Constraints for hypothetical interactions from a recent demonstration of the Casimir force and some possible improvements

The Casimir force is calculated in the configuration of a spherical lens and a disc of finite radius covered by $Cu$ and $Au$ thin layers which was used in a recent experiment. The correction to the Casimir force due to finiteness of the disc radius is shown to be negligible. Also the corrections are discussed due to the finite conductivity, large-scale and short-scale deviations from the perfect shape of the bounding surfaces and the temperature correction. They were found to be essential when confronting the theoretical results with experimental data. Both Yukawa-type and power-law hypothetical forces are computed which may act in the configuration under consideration due to the exchange of light and/or massless elementary particles between the atoms of the lens and the disc. New constraints on the constants of these forces are determined which follow from the fact that they were not observed within the limits of experimental errors. For Yukawa-type forces the new constraints are up to 30 times stronger than the best ones known up today. A possible improvement of experimental parameters is proposed which gives the possibility to strengthen constraints on Yukawa-type interactions up to $10^4$ times and on power-law interactions up to several hundred times.Comment: 15 pages, 3 figures, subm. to Phys. Rev.

Constraining axion-nucleon coupling constants from measurements of effective Casimir pressure by means of micromachined oscillator

Stronger constraints on the pseudoscalar coupling constants of an axion to a proton and a neutron are obtained from an indirect measurement of the effective Casimir pressure between two Au-coated plates by means of micromechanical torsional oscillator. For this purpose, the additional effective pressure due to two-axion exchange is calculated. The role of boundary effects and the validity region of the proximity force approximation in application to forces of axion origin are determined. The obtained constraints are up to factors of 380 and 3.15 stronger than those found recently from other laboratory experiments and are relevant to axion masses from $10^{-3}$eV to 15eV.Comment: 8 pages, 2 figures, 2 tables; several additions have been made in accordance with version accepted for publication in Eur. Phys. J.

Comment on "Thermal Lifshitz force between an atom and a conductor with a small density of carriers"

We demonstrate that the generalization of the Lifshitz theory proposed by L. P. Pitaevskii arXiv:0801.0656 [Phys. Rev. Lett. v.101, 163202 (2008)] violates the Nernst heat theorem for many dielectric materials and is experimentally inconsistent.Comment: 2 pages, 1 figure; minor revisions are made in accordance with the text accepted for publication in Phys. Rev. Let