3,750 research outputs found
Collapse models: from theoretical foundations to experimental verifications
The basic strategy underlying models of spontaneous wave function collapse
(collapse models) is to modify the Schroedinger equation by including nonlinear
stochastic terms, which tend to localize wave functions in space in a dynamical
manner. These terms have negligible effects on microscopic systems-therefore
their quantum behaviour is practically preserved. On the other end, since the
strength of these new terms scales with the mass of the system, they become
dominant at the macroscopic level, making sure that wave functions of
macro-objects are always well-localized in space. We will review these basic
features. By changing the dynamics of quantum systems, collapse models make
predictions, which are different from standard quantum mechanical predictions.
Although they are difficult to detect, we discuss the most relevant scenarios,
where such deviations can be observedComment: 10 Pages. Invited Talk at the Heinz von Foerster Centenary
International Conference on Self-Organization and Emergence: Emergent Quantum
Mechanics (EmerQuM11). Nov. 10-13, 2011, Vienna, Austria. Proceedings to
appear in J. Phys. (Conf. Series
Does the Targeted Jobs Tax Credit Create Jobs at Subsidized Firms?
This paper uses the results of a survey of more than 3,500 private employers to determine whether use of the Targeted Jobs Tax Credit (TJTC) alters the level of a firm\u27s employment and/or whom the firm hires. We estimate that each subsidized hire generates between .13 and .3 new jobs at a participating firm. Use of the program also appears to induce employers to hire more young workers (age 25 and under). Our results suggest, however, that at least 70 percent of the tax credits granted employers are payments for workers who would have been hired even without the subsidy. Such payments represent mere transfers to employers
On the Electromagnetic Properties of Matter in Collapse Models
We discuss the electromagnetic properties of both a charged free particle,
and a charged particle bounded by an harmonic potential, within collapse
models. By choosing a particularly simple, yet physically relevant, collapse
model, and under only the dipole approximation, we are able to solve the
equation of motion exactly. In this way, both the finite time and large time
behavior can be analyzed accurately. We discovered new features, which did not
appear in previous works on the same subject. Since, so far, the spontaneous
photon emission process places the strongest upper bounds on the collapse
parameters, our results call for a further analysis of this process for those
atomic systems which can be employed in experimental tests of collapse models,
as well as of quantum mechanics.Comment: 17 pages, LaTeX, updated version with minor change
Non-interferometric Test of Collapse Models in Optomechanical Systems
The test of modifications to quantum mechanics aimed at identifying the
fundamental reasons behind the un-observability of quantum mechanical
superpositions at the macro-scale is a crucial goal of modern quantum
mechanics. Within the context of collapse models, current proposals based on
interferometric techniques for their falsification are far from the
experimental state-of-the-art. Here we discuss an alternative approach to the
testing of quantum collapse models that, by bypassing the need for the
preparation of quantum superposition states might help us addressing non-linear
stochastic mechanisms such as the one at the basis of the continuous
spontaneous localisation model.Comment: 6 pages, accepted for publication in Phys. Rev. Lett.
CALCAREOUS ALGAE FROM THE LOWER OLIGOCENE GORNJI GRAD BEDS OF NORTHERN SLOVENIA
This paper presents the first systematic account of calcareous algae from the limestones of the Lower Oligocene Gornji Grad beds of northern Slovenia. These bioclastic limestones are dominated by different coralline algal assemblages as well as corals, large and small benthic foraminifera as well as bivalves. The taxonomy and growth-forms of eleven species of seven non-geniculate coralline algal genera are described: Lithoporella, Neogoniolithon, Spongites, Lithothamnion, Mesophyllum, Sporolithon, Subterraniphyllum,. Additionally, the genera Polystrata (Peyssonneliaceae) Halimeda (Halimedaceae), and Cymopolia (Dasycladaceae) are present. The taxonomic interpretation of fossil coralline material in a manner consistent with generic and specific concepts currently in use for Recent material is, at present, difficult. In the absence of comparative studies on type material, only limited comparisons are possible, and in most cases definitive taxonomic conclusions cannot be reached. Most of the species designations are thus made following and open nomenclature, pending the rigorous taxonomic revision of historically established, fossil coralline algal species. The present study reveals a considerable variation of growth-form morphologies at both genus and species levels. This demonstrates the difficulties in using this feature as a diagnostic character in the identification of fossil coralline red algal taxa. 
Generalized cross-covariances and their estimation
Generalized cross-covariances describe the linear relationships between spatial variables observed at different locations. They are invariant under translation of the locations for any intrinsic processes, they determine the cokriging predictors without additional assumptions and they are unique up to linear functions. If the model is stationary, that is if the variograms are bounded, they correspond to the stationary cross-covariances. Under some symmetry condition they are equal to minus the usual cross-variogram. We present a method to estimate these generalized cross-covariances from data observed at arbitrary sampling locations. In particular we do not require that all variables are observed at the same points. For fitting a linear coregionalization model we combine this new method with a standard algorithm which ensures positive definite coregionalization matrices. We study the behavior of the method both by computing variances exactly and by simulating from various model
Matrix difference equations for the supersymmetric Lie algebra sl(2,1) and the `off-shell' Bethe ansatz
Based on the rational R-matrix of the supersymmetric sl(2,1) matrix
difference equations are solved by means of a generalization of the nested
algebraic Bethe ansatz. These solutions are shown to be of highest-weight with
respect to the underlying graded Lie algebra structure.Comment: 10 pages, LaTex, references and acknowledgements added, spl(2,1) now
called sl(2,1
Crowdsourcing for Research: Perspectives From a Delphi Panel
Crowdsourcing, an open call for the public to collaborate and participate in problem solving, has been increasingly employed as a method in health-related research studies. Various reviews of the literature across different disciplines found crowdsourcing being used for data collection, processing, and analysis as well as tasks such as problem solving, data processing, surveillance/monitoring, and surveying. Studies on crowdsourcing tend to focus on its use of software, technology and online platforms, or its application for the purposes previously noted. There is need for further exploration to understand how best to use crowdsourcing for research, as there is limited guidance for researchers who are undertaking crowdsourcing for the purposes of scientific study. Numerous authors have identified gaps in research related to crowdsourcing, including a lack of decision aids to assist researchers using crowdsourcing, and best-practice guidelines. This exploratory study looks at crowdsourcing as a research method by understanding how and why it is being used, through application of a modified Delphi technique. It begins to articulate how crowdsourcing is applied in practice by researchers, and its alignment with existing research methods. The result is a conceptual framework for crowdsourcing, developed within traditional and existing research approaches as a first step toward its use in research
- …