Test of the gravitational redshift with stable clocks in eccentric orbits: application to Galileo satellites 5 and 6

The Einstein Equivalence Principle (EEP) is one of the foundations of the theory of General Relativity and several alternative theories of gravitation predict violations of the EEP. Experimental constraints on this fundamental principle of nature are therefore of paramount importance. The EEP can be split in three sub-principles: the Universality of Free Fall (UFF), the Local Lorentz Invariance (LLI) and the Local Position Invariance (LPI). In this paper we propose to use stable clocks in eccentric orbits to perform a test of the gravitational redshift, a consequence of the LPI. The best test to date was performed with the Gravity Probe A (GP-A) experiment in 1976 with an uncertainty of $1.4\times10^{-4}$. Our proposal considers the opportunity of using Galileo satellites 5 and 6 to improve on the GP-A test uncertainty. We show that considering realistic noise and systematic effects, and thanks to a highly eccentric orbit, it is possible to improve on the GP-A limit to an uncertainty around $(3-4)\times 10^{-5}$ after one year of integration of Galileo 5 and 6 data.Comment: 13 pages, 5 figures, accepted in Classical and Quantum Gravity as a Fast Track Communicatio

Time and frequency transfer with a microwave link in the ACES/PHARAO mission

The Atomic Clocks Ensemble in Space (ACES/PHARAO mission), which will be installed on board the International Space Station (ISS), uses a dedicated two-way Micro-Wave Link (MWL) in order to compare the timescale generated on board with those provided by many ground stations disseminated on the Earth. Phase accuracy and stability of this long range link will have a key role in the success of the ACES/PHARAO experiment. SYRTE laboratory is heavily involved in the design and development of the data processing software : from theoretical modelling and numerical simulations to the development of a software prototype. Our team is working on a wide range of problems that need to be solved in order to achieve high accuracy in (almost) real time. In this article we present some key aspects of the measurement, as well as current status of the software's development.Comment: Proceedings of the European Frequency and Time Forum (EFTF) 2012 held in Gothenburg, Sweden, April 201

Predictors of discordance among Chilean families

Parent-youth agreement on parental behaviors can characterize effective parenting. Although discordance in families may be developmentally salient and harmful to youth outcomes, predictors of discordance have been understudied, and existing research in this field has been mostly limited to North American samples. This paper addressed this literature gap by using data from a community-based study of Chilean adolescents. Analysis was based on 1,068 adolescents in Santiago, Chile. The dependent variable was discordance which was measured by the difference between parent and youth’s assessment of parental monitoring. Major independent variables for this study were selected based on previous research findings that underscore youth’s developmental factors, positive parental and familial factors and demographic factors. Descriptive and multivariate analyses were conducted to examine the prevalence and associations between youth, parental and familial measures with parent-youth discordance. There was a sizable level of discordance between parent and youth’s report of parental monitoring. Youth’s gender and externalizing behavior were significant predictors of discordance. Warm parenting and family involvement were met with decreases in discordance. The negative interaction coefficients between parental warmth and youth’s gender indicated that positive parental and familial measures have a greater effect on reducing parent-youth discordance among male youths. Results support the significance of positive family interactions in healthy family dynamics. Findings from this study inform the importance of services and interventions for families that aim to reduce youth’s problem behavior and to create a warm and interactive family environment.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4181713/Accepted manuscrip

A comparison between matter wave and light wave interferometers for the detection of gravitational waves

We calculate and compare the response of light wave interferometers and matter wave interferometers to gravitational waves. We find that metric matter wave interferometers will not challenge kilometric light wave interferometers such as Virgo or LIGO, but could be a good candidate for the detection of very low frequency gravitational waves

Extended Fermi coordinates

We extend the notion of Fermi coordinates to a generalized definition in which the highest orders are described by arbitrary functions. From this definition rises a formalism that naturally gives coordinate transformation formulae. Some examples are developped in which the extended Fermi coordinates simplify the metric components.Comment: 16 pages, 1 figur

The motion of vibrating systems in Schwarzchild spacetime

Abstract. In this communication, the effects of vibrations at high frequencies onto a freely falling two-body system in Schwarzschild spacetime are investigated. We present these effects for different kinds of reference motions, all of which are placed in regions of weak gravitation: circular orbits, radial free fall (with different initial velocities) and radial free fall with a small tangential velocity. The vibrations induce a change in the motion of the vibrating system, which is characterized by a radial deviation between the vibrating system and the reference motion of the non-vibrating system. For a circular orbit, we show that the maximal radial deviation increases linearly with the initial radius. For a radial free fall, the radial deviation after one oscillation decreases quadratically with respect to the initial radius

Differential item functioning due to gender between depression and anxiety items among Chilean adolescents

Although much is known about the higher prevalence of anxiety and depressive disorders among adolescent females, less is known about the differential item endorsement due to gender in items of commonly scales used to measure anxiety and depression. We conducted a study to examine if adolescent males and females from Chile differed on how they endorsed the items of the Youth Self-Report (YSR) anxious/depressed problem scale. We used data from a cross-sectional sample consisting of 925 participants (Mean age = 14, SD=1.3, 49% females) of low to lower-middle socioeconomic status. A two-parameter logistic (2PL) IRT DIF model was fit. Results revealed differential item endorsement (DIF) by gender for six of the 13 items with adolescent females being more likely to endorse a depression item while males were found more likely to endorse anxiety items. Findings suggest that items found in commonly utilized measures of anxiety and depression symptoms may not equally capture true levels of these behavioral problems among adolescent males and females. Given the high levels of mental disorders in Chile and surrounding countries, further attention should be focused on increasing the number of empirical studies examining potential gender differences in the assessment of mental health problems among Latin American populations to better aid our understanding of the phenomenology and determinants of these problems in the region.R01 HD033487 - NICHD NIH HHS; R01 DA021181-05 - NIDA NIH HHS; R01 DA021181 - NIDA NIH HH