Search results for "Invariance"

Noncritical quadrature squeezing in two-transverse-mode optical parametric oscillators

2010

In this article we explore the quantum properties of a degenerate optical parametric oscillator when it is tuned to the first family of transverse modes at the down-converted frequency. Recently we found [C. Navarrete-Benlloch et al., Phys. Rev. Lett. 100, 203601 (2008)] that above threshold a TEM${}_{10}$ mode following a random rotation in the transverse plane emerges in this system (we denote it as the bright mode), breaking thus its rotational invariance. Then, owing to the mode orientation being undetermined, we showed that the phase quadrature of the transverse mode orthogonal to this one (denoted as the dark mode) is perfectly squeezed at any pump level and without an increase in the…

Tridimensional invariant correlation based on phase-coded and sine-coded range images

1998

New methods for recognition of range images based on correlation are presented. The techniques allow the detection of a range image of a tridimensional pattern whatever its position along the x, y and z axes. The first method uses the phase-coding of the range image in order to obtain invariance along the z-axis in the correlation process. The second method uses the sine-coding of the range image in order to obtain better discrimination than that obtained with phase-coding. The third method is a hybrid one that makes use of sine-coding for the input scene and phase-coding for the reference image, so both the full translation invariance and high discrimination abilities are obtained. Compute…

Fractals and multifractals in the description of the cosmic structure

1990

Abstract The concepts of fractals and multifractals are applied to describe the large scale galaxy distribution. It is shown how the Universe fits the fractal geometry on small scales (several Mpc), but that there exists some cut-off where the scale invariance is broken. Even in the scaling region the cosmic structure is not a simple fractal, and the task is to introduce more complex and complete clustering descriptors. At this stage, the concept of multifractals appears to be more efficient to describe the texture of the Universe.

Analytical formula for calculating the focal shift in apodized systems

1998

We report a quite simple analytical formula for the evaluation of the focal shift in apodized systems, with or without rotational invariance. Specifically it is shown that the magnitude of the focal shift is determined by the product of the Fresnel number of the focusing geometry and the standard deviation of a mapped version of the azimuthal average of the pupil transmittance. To illustrate our approach, several examples are examined.

A parts-per-billion measurement of the antiproton magnetic moment

2017

The magnetic moment of the antiproton is measured at the parts-per-billion level, improving on previous measurements by a factor of about 350. Comparing the fundamental properties of normal-matter particles with their antimatter counterparts tests charge–parity–time (CPT) invariance, which is an important part of the standard model of particle physics. Many properties have been measured to the parts-per-billion level of uncertainty, but the magnetic moment of the antiproton has not. Christian Smorra and colleagues have now done so, and report that it is −2.7928473441 ± 0.0000000042 in units of the nuclear magneton. This is consistent with the magnetic moment of the proton, 2.792847350 ± 0.0…

Short form of revised two-factor study process questionnaire: Development, validation, and cross-validation in two European countries

2022

2019

Despite the general consensus regarding the implementation of self-report measures in the training monitoring, there is a lack of research about their applicability and comprehensibility among developing athletes. However, this target group needs special considerations to manage the increasing training demands while maintaining health and performance. This study deals with challenges of applying recovery-stress questionnaires which were validated with adult populations among developing athletes and presents a possible approach to enhance their applicability. In two phases, the Acute Recovery and Stress Scale (ARSS), a 32-adjective list covering eight scales, and the 8-item derived version, …

Analyzing measurement invariance of the students’ engagement instrument brief version:the cases of Denmark, Finland, and Portugal

2017

The promotion of students’ engagement with school is an internationally acknowledged challenge in education. There is a need to examine the structure of the concept of student engagement and to discover the best practices for fostering it across societies. That is why the cross-cultural invariance testing of students’ engagement measures is highly needed. This study aimed, first, to find the reduced set of theoretically valid items to represent students’ affective and cognitive engagement forming the Brief-SEI (brief version of the Student Engagement Instrument; SEI). The second aim was to test the measurement invariance of the Brief-SEI across three countries (Denmark, Finland, and Portug…

Factorial Validity and Reliability of the Curricular Goals in Physical Education Questionnaire

2015

This study aimed to examine the validity and reliability of an instrument designed to measure student perceptions of curricular goals in physical education, the Curricular Goals in Physical Education Questionnaire. Participants were 879 Finnish students from grades 7 to 9 (412 girls, 467 boys; mean age 13.81). An exploratory factor analysis was performed on Sample 1 (n = 287), revealing a four-factor solution and suggesting that factor structure be cross-validated with confirmatory factor analysis in Sample 2 (n = 592). Confirmatory factor analysis demonstrated an acceptable fit and supported the four-factor model. Tests for gender invariance supported configural, metric, and scalar invaria…

Modular Calabi-Yau threefolds of level eight

2005

In the studies on the modularity conjecture for rigid Calabi-Yau threefolds several examples with the unique level 8 cusp form were constructed. According to the Tate Conjecture correspondences inducing isomorphisms on the middle cohomologies should exist between these varieties. In the paper we construct several examples of such correspondences. In the constructions elliptic fibrations play a crucial role. In fact we show that all but three examples are in some sense built upon two modular curves from the Beauville list.