10,637 research outputs found
The Unresolved Land Reform Debate: Beyond State-Led or Market-Led Models
Land Reform; Debate; State-Led; Market-Led; Model
A Bootstrapping architecture for time expression recognition in unlabelled corpora via syntactic-semantic patterns
In this paper we describe a semi-supervised approach to the extraction of time expression mentions in large unlabelled corpora based on bootstrapping.
Bootstrapping techniques rely on a relatively small amount of initial human-supplied examples (termed “seeds”) of the type of entity or concept to be learned, in order to capture an initial set of patterns or rules from the unlabelled text that extract the supplied data. In turn, the learned patterns are employed to find new potential examples, and the process is repeated to grow the set of patterns and (optionally) the set of examples. In order to prevent the learned pattern set from producing spurious results, it becomes essential
to implement a ranking and selection procedure to filter out “bad” patterns and, depending on the case, new candidate examples. Therefore, the type of patterns employed (knowledge representation) as well as the ranking and selection procedure are paramount to the quality of the results. We present a complete bootstrapping algorithm for recognition of time expressions, with a special emphasis on the type of patterns used (a combination of semantic and morpho- syntantic elements) and the ranking and selection criteria. Bootstrap-
ping techniques have been previously employed with limited success for several NLP problems, both of recognition and classification, but their application to time expression recognition is, to the best of our knowledge, novel. As of this writing, the described architecture is in the final stages of implementation, with experimention and evalution being already underway.Postprint (published version
Topic modeling for entity linking using keyphrase
This paper proposes an Entity Linking system that applies a topic modeling ranking. We apply a novel approach in order to provide new relevant elements to the model. These elements are keyphrases related to the queries and gathered from a huge Wikipedia-based knowledge resourcePeer ReviewedPostprint (author’s final draft
Detecting entanglement of two electron spin qubits with witness operators
We propose a scheme for detecting entanglement between two electron spin
qubits in a double quantum dot using an entanglement witness operator. We first
calculate the optimal configuration of the two electron spins, defined as the
position in the energy level spectrum where, averaged over the nuclear spin
distribution, 1) the probability to have two separated electrons, and 2) the
degree of entanglement of the quantum state quantified by the concurrence are
both large. Using a density matrix approach, we then calculate the evolution of
the expectation value of the witness operator for the two-spin singlet state,
taking into account the effect of decoherence due to quantum charge
fluctuations modeled as a boson bath. We find that, for large interdot
coupling, it is possible to obtain a highly entangled and robust ground state.Comment: 4 pages, 3 figure
Collisional and thermal dissociation of and states at the LHC
We present new results for the suppression of high transverse momentum
charmonium [] and bottomonium
[] states in Pb+Pb collisions at the
Large Hadron Collider. Our theoretical formalism combines the collisional
dissociation of quarkonia, as they propagate in the quark-gluon plasma, with
the thermal wavefunction effects due to the screening of the
attractive potential in the medium. We find that a good description of the
relative suppression of the ground and higher excited quarkonium states,
transverse momentum and centrality distributions is achieved, when comparison
to measurements at a center-of-mass energy of 2.76 TeV is performed.
Theoretical predictions for the highest Pb+Pb center-of-mass energy of 5.02 TeV
at the LHC, where new experimental results are being finalized, are also
presented.Comment: 8 pages, 8 eps figures; 2 figures and references added, introduction
restructured; version to appear in PL
Mesure du de plus court temps de vie dans le cadre de l'expérience LHCb
L'expérience LHCb est une expérience de seconde génération dédiée à l'étude de la violation de la symétrie CP dans les systèmes des hadrons beaux. La symétrie CP est la combinaison de la symétrie de conjugaison de charge (C) qui échange particule et anti-particule et de la symétrie de parité (P) qui inverse les directions d'espace. L'ensemble des hadrons beaux est produit. Son détecteur sera l'un des quatre devant être installé sur le grand collisionneur de protons (LHC). Dans l'objectif de tester la validité du modèle standard dans ce domaine, il sera nécessaire d'effectuer une série de mesures de précision concernant les paramètres qui définissent la violation de CP et les grandeurs physiques caractérisant le mélange et la désintégration des hadrons beaux. Ce document décrit la probabilité de mesure de la différence relative de largeur de désintégration dans le système du méson () à travers l'étude du canal $B_{s}^{0}\rightarrow\,D_{s}^{+}\,D_{s}^{-}
Entanglement and the Quantum Brachistochrone Problem
Entanglement is closely related to some fundamental features of the dynamics
of composite quantum systems: quantum entanglement enhances the "speed" of
evolution of certain quantum states, as measured by the time required to reach
an orthogonal state. The concept of "speed" of quantum evolution constitutes an
important ingredient in any attempt to determine the fundamental limits that
basic physical laws impose on how fast a physical system can process or
transmit information. Here we explore the relationship between entanglement and
the speed of quantum evolution in the context of the quantum brachistochrone
problem. Given an initial and a final state of a composite system we consider
the amount of entanglement associated with the brachistochrone evolution
between those states, showing that entanglement is an essential resource to
achieve the alluded time-optimal quantum evolution.Comment: 6 pages, 3 figures. Corrected typos in Eqs. 1 and
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