Search results for "Observable"
showing 10 items of 634 documents
An Empirical Analysis of the Determinants of Perceived Inequality
2017
Perception of inequality is important for the analysis of individuals' motivations and decisions and for policy assessment. Despite the broad range of analytic gains that it grants, our knowledge about measurement and determinants of perception of inequality is still limited, since it is intrinsically unobservable, multidimensional, and essentially contested. Using a novel econometric approach, we study how observable individual characteristics affect the joint distribution of a set of indicators of perceived inequality in specific domains. Using data from the International Social Survey Programme, we shed light on the associations among these indicators and how they are affected by covaria…
Is traditional teaching really all that bad? A within-student between-subject approach
2011
Abstract Recent studies conclude that teachers are important for student learning but it remains uncertain what actually determines effective teaching. This study directly peers into the black box of educational production by investigating the relationship between lecture style teaching and student achievement. Based on matched student–teacher data for the US, the estimation strategy exploits between-subject variation to control for unobserved student traits. Results indicate that traditional lecture style teaching is associated with significantly higher student achievement. No support for detrimental effects of lecture style teaching can be found even when evaluating possible selection bia…
Calculating Hedonic Price Indices with Unobserved Product Attributes: An Application to the UK Car Market
2006
We show that hedonic price indices that omit model-specific unobservable product attributes are subject to considerable bias. We utilize a complete panel of new car versions marketed in the UK over 1971–98 which incorporates over 100 observable product characteristics, sales weighting to capture the distribution of purchases across models, and model-specific fixed effects to account for unobservable characteristics. We find that quality-adjusted prices obtained from hedonic regressions that do not account for unobservable characteristics exhibit a severe downward bias. We also show that quality-adjusted prices exhibit distinct sub-market differences having increased in ‘mass production’ seg…
Study of Cluster Structures in Nuclei through the Ratio Method. A Tribute to Mahir Hussein
2020
For one-neutron halo nuclei, the cross sections for elastic scattering and breakup at intermediate energy exhibit similar angular dependences. The Recoil Excitation and Breakup (REB) model of reactions elegantly explains this feature. It also leads to the idea of a new reaction observable to study the structure of loosely-bound nuclear systems: the Ratio. This observable consists of the ratio of angular distributions for different reaction channels, viz. elastic scattering and breakup, which cancels most of the dependence on the reaction mechanism; in particular it is insensitive to the choice of optical potentials that simulate the projectile-target interaction. This new observable is very…
Thermodynamics of electrokinetic processes—II. systems with different kinds of electrodes
1990
Abstract In this work Haase's Formulation of Electrokinetic Processes is applied to special systems: those working with two different electrodes and those where gaseous phases are formed. Phenomenological equations are always written in terms of directly observable variables. The extrinsic character of Haase's Formulation is clearly shown. Some special results on streaming current in dielectric liquids are explained.
The lifetime of unstable particles in electromagnetic fields
2007
We show that the electromagnetic moments of unstable particles (resonances) have an absorptive contribution which quantifies the change of the particle's lifetime in an external electromagnetic field. To give an example we compute here the imaginary part of the magnetic moment for the cases of the muon and the neutron at leading order in the electroweak coupling. We also consider an analogous effect for the strongly-decaying $\Delta$(1232) resonance. The result for the muon is Im$ \mu = e G_F^2 m^3/768 \pi^3$, with $e$ the charge and $m$ the mass of the muon, $G_F$ the Fermi constant, which in an external magnetic field of $B$ Tesla give rise to the relative change in the muon lifetime of $…
Vacuum induced berry phase: Theory and experimental proposal
2003
We investigate quantum effects in geometric phases arising when a two-level system is interacting with a quantized electromagnetic field. When the system is adiabatically driven along a closed loop in the parameter space, signatures of the field quantization are observable in the geometric phase. We propose a feasible experiment to measure these effects in cavity QED and also analyse the semi-classical limit, recovering the usual Berry phase results.
Virtual Compton Scattering and polarizabilities
1999
Abstract Virtual Compton Scattering (VCS) off the proton below pion threshold allows access to generalized polarizabilities of the proton. These observables measure the response of the nucleon to low energy electromagnetic field perturbations. This paper presents a comparison with Real Compton Scattering and also results for the first dedicated VCS experiment performed at the Mainz Microtron MAMI with high resolution spectrometers at Q2 = 0.33 GeV2.
Expanding the Active Inference Landscape: More Intrinsic Motivations in the Perception-Action Loop
2018
Active inference is an ambitious theory that treats perception, inference and action selection of autonomous agents under the heading of a single principle. It suggests biologically plausible explanations for many cognitive phenomena, including consciousness. In active inference, action selection is driven by an objective function that evaluates possible future actions with respect to current, inferred beliefs about the world. Active inference at its core is independent from extrinsic rewards, resulting in a high level of robustness across e.g.\ different environments or agent morphologies. In the literature, paradigms that share this independence have been summarised under the notion of in…
A quantum vocal theory of sound
2020
Concepts and formalism from acoustics are often used to exemplify quantum mechanics. Conversely, quantum mechanics could be used to achieve a new perspective on acoustics, as shown by Gabor studies. Here, we focus in particular on the study of human voice, considered as a probe to investigate the world of sounds. We present a theoretical framework that is based on observables of vocal production, and on some measurement apparati that can be used both for analysis and synthesis. In analogy to the description of spin states of a particle, the quantum-mechanical formalism is used to describe the relations between the fundamental states associated with phonetic labels such as phonation, turbule…