18,340 research outputs found
Thermodynamics of nonsingular bouncing universes
Homogeneous and isotropic, nonsingular, bouncing world models are designed to
evade the initial singularity at the beginning of the cosmic expansion. Here,
we study the thermodynamics of the subset of these models governed by general
relativity. Considering the entropy of matter, radiation and that the entropy
of the apparent horizon is proportional to its area, we argue that these models
do not respect the generalised second law of thermodynamics, also away from the
bounce.Comment: 12 pages, 3 figures. Version published in the European Physical
Journal
Discriminating word senses with tourist walks in complex networks
Patterns of topological arrangement are widely used for both animal and human
brains in the learning process. Nevertheless, automatic learning techniques
frequently overlook these patterns. In this paper, we apply a learning
technique based on the structural organization of the data in the attribute
space to the problem of discriminating the senses of 10 polysemous words. Using
two types of characterization of meanings, namely semantical and topological
approaches, we have observed significative accuracy rates in identifying the
suitable meanings in both techniques. Most importantly, we have found that the
characterization based on the deterministic tourist walk improves the
disambiguation process when one compares with the discrimination achieved with
traditional complex networks measurements such as assortativity and clustering
coefficient. To our knowledge, this is the first time that such deterministic
walk has been applied to such a kind of problem. Therefore, our finding
suggests that the tourist walk characterization may be useful in other related
applications
System identification, time series analysis and forecasting:The Captain Toolbox handbook.
CAPTAIN is a MATLAB compatible toolbox for non stationary time series analysis, system identification, signal processing and forecasting, using unobserved components models, time variable parameter models, state dependent parameter models and multiple input transfer function models. CAPTAIN also includes functions for true digital control
Ultrafast Coherent Spectroscopy of the Fermi Edge Singularity
In this work we present a theoretical description of the transient response
of the Fermi Edge Singularity (FES). We study the linear and the nonlinear
response of an n-doped QW to laser pulses in the Coherent Control (CC) and Four
Wave Mixing (FWM) Configurations. By means of a bosonization formalism we
calculate the FWM signal emitted by the sample when it is excited by pulses
spectrally peaked around the FES and we show that the long time behavior of the
nonlinear signal is very similar to the linear case.Comment: Conference paper (13 EP2DS
Quantum Strings and the AdS4/CFT3 Interpolating Function
The existence of a nontrivial interpolating function h(\lambda) is one of the
novel features of the new AdS4/CFT3 correspondence involving ABJM theory. At
strong coupling, most of the investigation of semiclassical effects so far has
been for strings in the AdS4 sector. Several cutoff prescriptions have been
proposed, leading to different predictions for the constant term in the
expansion h(\lambda)=\sqrt{\lambda/2} + c + ... . We calculate quantum
corrections for giant magnons, using the algebraic curve, and show by comparing
to the dispersion relation that the same prescriptions lead to the same values
of c in this CP3 sector. We then turn to finite-J effects, where a comparison
with the Luescher F-term correction shows a mismatch for one of the three sum
prescriptions. We also compute some dyonic and higher F-terms for future
comparisons.Comment: 30 pages, 1 figure, 1 table. v2 has minor improvements to the text,
and extra references. v3 has further textual changes, version to appear in
JHE
Discussion of âclustering on dissimilarity Representations for detecting mislabelled Seismic signals at Nevado del Ruiz Volcanoâ by Mauricio Orozco-Alzate, and CĂ©sar GermĂĄn Castellanos-DomĂnguez
The authors are to be congratulated for a systematic investigationof the accurate and non subjective classifying approach in seismic research. The authors have conducted several clustering algorithms to the seismic event records from Volcanological and SeismologicalObservatory at Manizales. Their objective was to improve the grouping of seismic data (i.e., volcano-tectonic earthquakes, long-period earthquakes and icequakes) digitized at 100.16 Hz sampling frequency.Their study seems adding new approach to their previous work of Langer et al. (2006) who applied different classification techniques to seismic data
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