The electro production of d* dibaryon

$d^*$ dibaryon study is a critical test of hadron interaction models. The electro production cross sections of $ed\to ed^*$ have been calculated based on the meson exchange current model and the cross section around 30 degree of 1 GeV electron in the laboratory frame is about 10 nb. The implication of this result for the $d^*$ dibaryon search has been discussed.Comment: 12 pages, 12 figures, Late

Spontaneous patterns in coherently driven polariton microcavities

We consider a polariton microcavity resonantly driven by two external lasers which simultaneously pump both lower and upper polariton branches at normal incidence. In this setup, we study the occurrence of instabilities of the pump-only solutions towards the spontaneous formation of patterns. Their appearance is a consequence of the spontaneous symmetry breaking of translational and rotational invariance due to interaction induced parametric scattering. We observe the evolution between diverse patterns which can be classified as single-pump, where parametric scattering occurs at the same energy as one of the pumps, and as two-pump, where scattering occurs at a different energy. For two-pump instabilities, stripe and chequerboard patterns become the dominant steady-state solutions because cubic parametric scattering processes are forbidden. This contrasts with the single-pump case, where hexagonal patterns are the most common arrangements. We study the possibility of controlling the evolution between different patterns. Our results are obtained within a linear stability analysis and are confirmed by finite size full numerical calculations.Comment: 15 pages, 9 figure

Quantitative Description of Strong-Coupling of Quantum Dots in Microcavities

We have recently developed a self-consistent theory of Strong-Coupling in the presence of an incoherent pumping [arXiv:0807.3194] and shown how it could reproduce quantitatively the experimental data [PRL 101, 083601 (2008)]. Here, we summarize our main results, provide the detailed analysis of the fitting of the experiment and discuss how the field should now evolve beyond merely qualitative expectations, that could well be erroneous even when they seem to be firmly established.Comment: Submitted to the AIP Conference Proceedings Series for the ICPS 2008 (Rio de Janeiro). 2 pages, reduced-quality figur

Electrostatic control of quantum dot entanglement induced by coupling to external reservoirs

We propose a quantum transport experiment to prepare and measure charge-entanglement between two electrostatically defined quantum dots. Coherent population trapping, as realized in cavity quantum electrodynamics, can be carried out by using a third quantum dot to play the role of the optical cavity. In our proposal, a pumping which is quantum mechanically indistinguishable for the quantum dots drives the system into a state with a high degree of entanglement. The whole effect can be switched on and off by means of a gate potential allowing both state preparation and entanglement detection by simply measuring the total current.Comment: 5 pages, 4 figures, Latex2e with EPL macros, to appear in Europhysics Letter

La estadística y los diferentes paradigmas de investigación educativa

En este trabajo el autor asocia el término paradigma a la perspectiva científica que predomina en un campo determinado y aboga por mantener la denominación "paradigmas racionalista y naturalista" y evitar el planteamiento del problema en términos de "cuantitativo y cualitativo". Analiza las diferencias entre ambos paradigmas y asocia la dicotomía entre los métodos cuantitativos y cualitativos al pensamiento de que existe una vinculación única e inequívoca entre método y paradigma justificando que no existe una relación exclusiva entre método y paradigma. Se define el método como el conjunto de procedimientos a seguir por toda actividad que aspire a ser científica cuya misión es aportar pruebas empíricas verificables aunque, una vez observado el hecho, el investigador puede afrontar el problema dentro de un marco Hipotético-Deductivo o dentro de un marco Analítico-Inductiva. Se aportan las características de los métodos cuantitativos y de los métodos cualitativos asociándolos a unas metodologías, diseños y a unas técnicas de análisis de datos determinadas y se analizan las diferencias principales entre ambos aportando soluciones para responder a posibles desajustes entre modelos teóricos y esquemas experimentales. Se fundamenta la Estadística como instrumento principal del estudio pedagógico concreto y se la define como la ciencia que, analizando los datos reales, posibilita el contacto con las estructuras de los sistemas formales. El autor deja claro la no procedencia de "rebajan, las exigencias del análisis estadístico para hacerlo compatible con estrategias cualitativas y apunta la posibilidad y la necesidad de convergencia metodológica de la investigación educativa. Una afirmación rotunda: la investigación mas relevante será aquélla que, contribuyendo a mejorar la practica, ofrezca hipótesis cuya aplicación pueda verificarse con la propia acción docente al desarrollar el curriculum. Esta investigación no puede ser otra que aquélla que consiga la adecuada síntesis entre las diversas estrategias metodológicas.In this work the author associates the word paradigm to the scientific perspective which prevails in a determinate field and upholds the denomination "Rationalist and Naturalist paradigms" and avoids setting out the problem in terms of "quantitative and qualitative". He analizes the differences between both paradigms and associates the dichotomy between quantitative and qualitative methods to the thought that one unique and unequivocal vinculation exists between method and paradigm does not exist. The method is defined as the combination of procedures to follow for every activity which pretends to be scientific whose mission is to bring empiric factual evidence although, once the fact has been observed, the researcher can look at the problem from a Hypothetic-Deductive angle or an Analitic-Inductive point of view. The characteristics of the quantitative methods and qualitative methods are brought in and are associated to some methodologies, designs and techniques of certain data analysis. The main differences between both are analysed bringing in solutions to answer and experimental schemes. Statistics is established as the main instrument of specific pedagogical study and is defined as the science which wile analising real data enables contact with the formal systems' structures. The author makes clear that is not proper to reduce the demands of statical analysis to make it compatible with qualitative strategies and points out the possibility and necessity of methodological convergence in educational research. One emphatic affirmation: the most important research will be that while helping to improve practice, offers hypotesis whoseapplication can be proved by the educational action itself when developing the curriculum.This research can be no other than that which achieves the suitable synthesis between methodological strategies

Restrictions on the coherence of the ultrafast optical emission from an electron-hole pairs condensate

We report on the transfer of coherence from a quantum-well electron-hole condensate to the light it emits. As a function of density, the coherence of the electron-hole pair system evolves from being full for the low density Bose-Einstein condensate to a chaotic behavior for a high density BCS-like state. This degree of coherence is transfered to the light emitted in a damped oscillatory way in the ultrafast regime. Additionally, the photon field exhibits squeezing properties during the transfer time. We analyze the effect of light frequency and separation between electron and hole layers on the optical coherence. Our results suggest new type of ultrafast experiments for detecting electron-hole pair condensation.Comment: 4 pages,3 figures, to be published in Physical Review Letters. Minor change

All-optical non-demolition measurement of single-hole spin in a quantum-dot molecule

We propose an all-optical scheme to perform a non-demolition measurement of a single hole spin localized in a quantum-dot molecule. The latter is embedded in a microcavity and driven by two lasers. This allows to induce Raman transitions which entangle the spin state with the polarization of the emitted photons. We find that the measurement can be completed with high fidelity on a timescale of 100 ps, shorter than the typical T2. Furthermore, we show that the scheme can be used to induce and observe spin oscillations without the need of time-dependent magnetic fields