Coherent matter wave inertial sensors for precision measurements in space

We analyze the advantages of using ultra-cold coherent sources of atoms for matter-wave interferometry in space. We present a proof-of-principle experiment that is based on an analysis of the results previously published in [Richard et al., Phys. Rev. Lett., 91, 010405 (2003)] from which we extract the ratio h/m for 87Rb. This measurement shows that a limitation in accuracy arises due to atomic interactions within the Bose-Einstein condensate

Accuracy of numerical relativity waveforms from binary neutron star mergers and their comparison with post-Newtonian waveforms

We present numerical relativity simulations of nine-orbit equal-mass binary neutron star covering the quasicircular late inspiral and merger. The extracted gravitational waveforms are analyzed for convergence and accuracy. Second order convergence is observed up to contact, i.e. about 3-4 cycles to merger; error estimates can be made up to this point. The uncertainties on the phase and the amplitude are dominated by truncation errors and can be minimized to 0.13 rad and less then 1%, respectively, by using several simulations and extrapolating in resolution. In the latter case finite-radius extraction uncertainties become a source of error of the same order and have to be taken into account. The waveforms are tested against accuracy standards for data analysis. The uncertainties on the waveforms are such that accuracy standards are generically not met for signal-to-noise ratios relevant for detection, except for some best cases using extrapolation from several runs. A detailed analysis of the errors is thus imperative for the use of numerical relativity waveforms from binary neutron stars in quantitative studies. The waveforms are compared with the post-Newtonian Taylor T4 approximants both for point-particle and including the analytically known tidal corrections. The T4 approximants accumulate significant phase differences of 2 rad at contact and 4 rad at merger, underestimating the influence of finite size effects. Tidal signatures in the waveforms are thus important at least during the last six orbits of the merger process.Comment: Physical Review D (Vol.85, No.10) 201

On Essential Incompleteness of Hertz's Experiments on Propagation of Electromagnetic Interactions

The historical background of the 19th century electromagnetic theory is revisited from the standpoint of the opposition between alternative approaches in respect to the problem of interactions. The 19th century electrodynamics became the battle-field of a paramount importance to test existing conceptions of interactions. Hertz's experiments were designed to bring a solid experimental evidence in favor of one of them. The modern scientific method applied to analyze Hertz's experimental approach as well as the analysis of his laboratory notes, dairy and private letters show that Hertz's "\textit{crucial}" experiments cannot be considered as conclusive at many points as it is generally implied. We found that alternative Helmholtz's electrodynamics did not contradict any of Hertz's experimental observations of transverse components as Maxwell's theory predicted. Moreover, as we now know from recently published Hertz's dairy and private notes, his first experimental results indicated clearly on infinite rate of propagation. Nevertheless, Hertz's experiments provided no further explicit information on non-local longitudinal components which were such an essential feature of Helmholtz's theory. Necessary and sufficient conditions for a decisive choice on the adequate account of electromagnetic interactions are discussed from the position of modern scientific method

Heisenberg's uncertainty principle

Heisenberg's uncertainty principle is usually taken to express a limitation of operational possibilities imposed by quantum mechanics. Here we demonstrate that the full content of this principle also includes its positive role as a condition ensuring that mutually exclusive experimental options can be reconciled if an appropriate trade-off is accepted. The uncertainty principle is shown to appear in three manifestations, in the form of uncertainty relations: for the widths of the position and momentum distributions in any quantum state; for the inaccuracies of any joint measurement of these quantities; and for the inaccuracy of a measurement of one of the quantities and the ensuing disturbance in the distribution of the other quantity. Whilst conceptually distinct, these three kinds of uncertainty relations are shown to be closely related formally. Finally, we survey models and experimental implementations of joint measurements of position and momentum and comment briefly on the status of experimental tests of the uncertainty principle. (c) 2007 Elsevier B.V. All rights reserved

Dopamine, time perception, and future time perspective.

RationaleImpairment in time perception, a critical component of decision-making, represents a risk factor for psychiatric conditions including substance abuse. A therapeutic that ameliorates this impairment could be advantageous in the treatment of impulsivity and decision-making disorders.ObjectivesHere we hypothesize that the catechol-O-methyltransferase (COMT) inhibitor tolcapone, which increases dopamine tone in frontal cortex (Ceravolo et al Synapse 43:201-207, 2002), improves time perception, with predictive behavioral, genetic, and neurobiological components.MethodsSubjects (n = 66) completed a duration estimation task and other behavioral testing in each of two sessions after receiving a single oral dose of tolcapone (200 mg) or placebo in randomized, double-blind, counterbalanced, crossover fashion. Resting state fMRI data were obtained in a subset of subjects (n = 40). Subjects were also genotyped for the COMT (rs4680) polymorphism.ResultsTime perception was significantly improved across four proximal time points ranging from 5 to 60 s (T(524) = 2.04, p = 0.042). The degree of this improvement positively correlated with subjective measures of stress, depression, and alcohol consumption and was most robust in carriers of the COMT Val158 allele. Using seed regions defined by a previous meta-analysis (Wiener et al Neuroimage 49:1728-1740, 2010), we found not only that a connection from right inferior frontal gyrus (RIFG) to right putamen decreases in strength on tolcapone versus placebo (p < 0.05, corrected), but also that the strength of this decrease correlates inversely with the increase in duration estimation on tolcapone versus placebo (r = - 0.37, p = 0.02).ConclusionsCompressed time perception can be ameliorated by administration of tolcapone. Additional studies should be conducted to determine whether COMT inhibitors may be effective in treating decision-making disorders and addictive behaviors

Development of a strontium optical lattice clock for the SOC mission on the ISS

The ESA mission "Space Optical Clock" project aims at operating an optical lattice clock on the ISS in approximately 2023. The scientific goals of the mission are to perform tests of fundamental physics, to enable space-assisted relativistic geodesy and to intercompare optical clocks on the ground using microwave and optical links. The performance goal of the space clock is less than $1 \times 10^{-17}$ uncertainty and $1 \times 10^{-15} {\tau}^{-1/2}$ instability. Within an EU-FP7-funded project, a strontium optical lattice clock demonstrator has been developed. Goal performances are instability below $1 \times 10^{-15} {\tau}^{-1/2}$ and fractional inaccuracy $5 \times 10^{-17}$. For the design of the clock, techniques and approaches suitable for later space application are used, such as modular design, diode lasers, low power consumption subunits, and compact dimensions. The Sr clock apparatus is fully operational, and the clock transition in $^{88}$Sr was observed with linewidth as small as 9 Hz.Comment: 12 pages, 8 figures, SPIE Photonics Europe 201

A single axis study of flight simulator kinematics by difference techniques

The kinematic parameters of position, velocity, and acceleration of a flight simulator may be calculated by knowing the distance between two or more points on an axis and the time the simulator takes to traverse the space between each set of points. These parameters are calculated through the use of difference techniques. Given the true kinematic response of the simulator to computer generated commands, the entire motion system loop may be calibrated, and system operability verified