2,768 research outputs found
Helping Students Master Concepts in Mechanics by Graphing with Spreadsheets
An example of a curricular activity to help students master concepts in mechanics is presented. Students measure positions and times of movements using calculators, and construct graphs using spreadsheets. Students learn to connect concepts in mechanics and reinforce them following a spiral approach of increasing complexity. Comments from students about the activity are also presented
Maximum approximate entropy and r threshold: A new approach for regularity changes detection
Approximate entropy (ApEn) has been widely used as an estimator of regularity
in many scientific fields. It has proved to be a useful tool because of its
ability to distinguish different system's dynamics when there is only available
short-length noisy data. Incorrect parameter selection (embedding dimension
, threshold and data length ) and the presence of noise in the signal
can undermine the ApEn discrimination capacity. In this work we show that
() can also be used as a feature to
discern between dynamics. Moreover, the combined use of and
allows a better discrimination capacity to be accomplished, even in
the presence of noise. We conducted our studies using real physiological time
series and simulated signals corresponding to both low- and high-dimensional
systems. When is incapable of discerning between different
dynamics because of the noise presence, our results suggest that
provides additional information that can be useful for classification purposes.
Based on cross-validation tests, we conclude that, for short length noisy
signals, the joint use of and can significantly decrease
the misclassification rate of a linear classifier in comparison with their
isolated use
Bound-state dark matter with Majorana neutrinos
We propose a simple scenario in which dark matter (DM) emerges as a stable
neutral hadronic thermal relics, its stability following from an exact
symmetry. Neutrinos pick up radiatively induced
Majorana masses from the exchange of colored DM constituents. There is a common
origin for both dark matter and neutrino mass, with a lower bound for
neutrinoless double beta decay. Direct DM searches at nuclear recoil
experiments will test the proposal, which may also lead to other
phenomenological signals at future hadron collider and lepton flavour violation
experiments.Comment: 9 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1803.0852
Simple regular black hole with logarithmic entropy correction
A simple regular black hole solution satisfying the weak energy condition is
obtained within Einstein--non--linear electrodynamics theory. We have computed
the thermodynamic properties of this black hole by a careful analysis of the
horizons and we have found that the usual Bekenstein--Hawking entropy gets
corrected by a logarithmic term. Therefore, in this sense our model realizes
some quantum gravity predictions which add this kind of correction to the black
hole entropy. In particular, we have established some similitudes between our
model and a quadratic generalized uncertainty principle. This similitude has
been confirmed by the existence of a remnant, which prevents complete
evaporation, in agreement with the quadratic generalized uncertainty principle
case
Neutralino Phenomenology at LEP2 in Supersymmetry with Bilinear Breaking of R-parity
We discuss the phenomenology of the lightest neutralino in models where an
effective bilinear term in the superpotential parametrizes the explicit
breaking of R-parity. We consider supergravity scenarios where the lightest
supersymmetric particle (LSP) is the lightest neutralino and which can be
explored at LEP2. We present a detailed study of the LSP decay properties and
general features of the corresponding signals expected at LEP2. We also
contrast our model with gauge mediated supersymmetry breaking.Comment: 21 pages, Latex, uses axodraw.sty (included), 13 figures included as
ps- and eps-files, figures slightly changed after bug-fixing, comparison with
GMSB and a few references added, version to appear in NP
Finding the Higgs Boson through Supersymmetry
The study of displaced vertices containing two b--jets may provide a double
discovery at the Large Hadron Collider (LHC): we show how it may not only
reveal evidence for supersymmetry, but also provide a way to uncover the Higgs
boson necessary in the formulation of the electroweak theory in a large region
of the parameter space. We quantify this explicitly using the simplest minimal
supergravity model with bilinear breaking of R-parity, which accounts for the
observed pattern of neutrino masses and mixings seen in neutrino oscillation
experiments.Comment: 7 pages, 7 figures. Final version to appear at PRD. Discussion and
results were enlarge
Characterizing the dynamical importance of network nodes and links
The largest eigenvalue of the adjacency matrix of the networks is a key
quantity determining several important dynamical processes on complex networks.
Based on this fact, we present a quantitative, objective characterization of
the dynamical importance of network nodes and links in terms of their effect on
the largest eigenvalue. We show how our characterization of the dynamical
importance of nodes can be affected by degree-degree correlations and network
community structure. We discuss how our characterization can be used to
optimize techniques for controlling certain network dynamical processes and
apply our results to real networks.Comment: 4 pages, 4 figure
The Work of Amnesty International and Human Rights Watch: Evidence from Colombia
We process the main written output of Amnesty International and Human Rights Watch on Colombia covering the period 1988-2004, recording all numerical conflict information and accounts of specific conflict events. We check for internal consistency and against a unique Colombian conflict database. We find that both organizations have substantive problems in their handling of quantitative information. Problems include failre to specify sources, unclear definitions, an erratic reporting template and a distorted portrayal of conflict dynamics. Accounts of individual events are fairly representative and much more useful and accurate than the statistical information. We disprove a common accusation that Amnesty International and Human Rights Watch rarely criticize the guerrillas, but do find some evidence of anti-government bias. The quantitative human rights and conflict information produced by these organizations for other countries must be viewed with scepticism along with cross-country and time series human rights data based on Amnesty International reports.
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