Comment on ``Precision measurement of the Casimir-Lifshitz force in a fluid''

Recently J.N. Munday and F. Capasso [Phys. Rev. A {\bf 75}, 060102(R) (2007); arXiv:0705.3793] claimed that they have performed a precision measurement of the Casimir force between a sphere and a plate coated with Au, both immersed in ethanol. The measurement results were claimed to be consistent with the Lifshitz theory. We demonstrate that the calculation of the Casimir force between the smooth bodies following the authors prescription has a discrepancy up to 25% with respect to authors result. We show also that the attractive electrostatic force only due to the surface potential differences was underestimated by a factor of 590 and the charge double layer interaction was not taken into account. All this leads to the conclusion that the results of this experiment are in fact uncertain.Comment: 5 pages, 1 figure, submitted to Physical Review A; corrections are made in accordance to referee's suggestion

Energy levels and decoherence properties of single electron and nuclear spins in a defect center in diamond

The coherent behavior of the single electron and single nuclear spins of a defect center in diamond and a 13C nucleus in its vicinity, respectively, are investigated. The energy levels associated with the hyperfine coupling of the electron spin of the defect center to the 13C nuclear spin are analyzed. Methods of magnetic resonance together with optical readout of single defect centers have been applied in order to observe the coherent dynamics of the electron and nuclear spins. Long coherence times, in the order of microseconds for electron spins and tens of microseconds for nuclear spins, recommend the studied system as a good experimental approach for implementing a 2-qubit gate.Comment: 4 pages, 4 figure

A New Heavy-Fermion Superconductor CeIrIn5: Relative of the Cuprates?

CeIrIn5 is a member of a new family of heavy-fermion compounds and has a Sommerfeld specific heat coefficient of 720 mJ/mol-K2. It exhibits a bulk, thermodynamic transition to a superconducting state at Tc=0.40 K, below which the specific heat decreases as T2 to a small residual T-linear value. Surprisingly, the electrical resistivity drops below instrumental resolution at a much higher temperature T0=1.2 K. These behaviors are highly reproducible and field-dependent studies indicate that T0 and Tc arise from the same underlying electronic structure. The layered crystal structure of CeIrIn5 suggests a possible analogy to the cuprates in which spin/charge pair correlations develop well above Tc

Coexistent State of Charge Density Wave and Spin Density Wave in One-Dimensional Quarter Filled Band Systems under Magnetic Fields

We theoretically study how the coexistent state of the charge density wave and the spin density wave in the one-dimensional quarter filled band is enhanced by magnetic fields. We found that when the correlation between electrons is strong the spin density wave state is suppressed under high magnetic fields, whereas the charge density wave state still remains. This will be observed in experiments such as the X-ray measurement.Comment: 7 pages, 15 figure

Forces between electric charges in motion: Rutherford scattering, circular Keplerian orbits, action-at-a-distance and Newton's third law in relativistic classical electrodynamics

Standard formulae of classical electromagnetism for the forces between electric charges in motion derived from retarded potentials are compared with those obtained from a recently developed relativistic classical electrodynamic theory with an instantaneous inter-charge force. Problems discussed include small angle Rutherford scattering, Jackson's recent `torque paradox' and circular Keplerian orbits. Results consistent with special relativity are obtained only with an instantaneous interaction. The impossiblity of stable circular motion with retarded fields in either classical electromagnetism or Newtonian gravitation is demonstrated.Comment: 26 pages, 5 figures. QED and special relativity forbid retarded electromagnetic forces. See also physics/0501130. V2 has typos corrected, minor text modifications and updated references. V3 has further typos removed and added text and reference

Anomalous behaviour of the in-plane electrical conductivity of the layered superconductor κ\kappa-(BEDT-TTF)2_2Cu(NCS)2_2

The quasiparticle scattering rates in high-quality crystals of the quasi-two-dimensional superconductor $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$ ~are studied using the Shubnikov-de Haas effect and MHz penetration-depth experiments. There is strong evidence that the broadening of the Landau-levels is primarily caused by spatial inhomogeneities, indicating a quasiparticle lifetime for the Landau states $\gg 3$ ps. In contrast to the predictions of Fermi-liquid theory, the scattering time derived from the intralayer conductivity is found to be much shorter ($0.14-0.56$ ps)

Electronic detection of charged particle effects in a Penning trap

We present a thorough analysis of the electronic detection of charged particles, confined in a Penning trap, via image charges induced in the trap electrodes. Trapping of charged particles in an electrode structure leads to frequency shifts, which are due to image charge and space charge effects. These effects are of importance for Penning trap experiments which involve high charge densities or require high precision in the motional frequencies. Our analysis of image charges shows that only (higher order) odd powers of the particle displacement lead to induced charge differences, giving rise to a signal. This implies that, besides the centre-of-mass frequency of a trapped particle cloud, also higher order individual particle frequencies induce a signal, which can be picked up by an electronic detection circuit attached to the trap electrodes. We also derive analytic expressions for the image charge and space charge induced frequency shifts and perform simulations of space charge effects. In relation to this, we discuss the consequences of the shifted particle frequencies for resistive cooling of the particle motion.Comment: 16 pages, 4 figure

Actinide covalency measured by pulsed electron paramagnetic resonance spectroscopy

Our knowledge of actinide chemical bonds lags far behind our understanding of the bonding regimes of any other series of elements. This is a major issue given the technological as well as fundamental importance of f-block elements. Some key chemical differences between actinides and lanthanides—and between different actinides—can be ascribed to minor differences in covalency, that is, the degree to which electrons are shared between the f-block element and coordinated ligands. Yet there are almost no direct measures of such covalency for actinides. Here we report the first pulsed electron paramagnetic resonance spectra of actinide compounds. We apply the hyperfine sublevel correlation technique to quantify the electron-spin density at ligand nuclei (via the weak hyperfine interactions) in molecular thorium(III) and uranium(III) species and therefore the extent of covalency. Such information will be important in developing our understanding of the chemical bonding, and therefore the reactivity, of actinides