Hall response of interacting bosonic atoms in strong gauge fields: from condensed to FQH states

Interacting bosonic atoms under strong gauge fields undergo a series of phase transitions that take the cloud from a simple Bose-Einstein condensate all the way to a family of fractional-quantum-Hall-type states [M. Popp, B. Paredes, and J. I. Cirac, Phys. Rev. A 70, 053612 (2004)]. In this work we demonstrate that the Hall response of the atoms can be used to locate the phase transitions and characterize the ground state of the many-body state. Moreover, the same response function reveals within some regions of the parameter space, the structure of the spectrum and the allowed transitions to excited states. We verify numerically these ideas using exact diagonalization for a small number of atoms, and provide an experimental protocol to implement the gauge fields and probe the linear response using a periodically driven optical lattice. Finally, we discuss our theoretical results in relation to recent experiments with condensates in artificial magnetic fields [ L. J. LeBlanc, K. Jimenez-Garcia, R. A. Williams, M. C. Beeler, A. R. Perry, W. D. Phillips, and I. B. Spielman, Proc. Natl. Acad. Sci. USA 109, 10811 (2012)] and we analyze the role played by vortex states in the Hall response.Comment: 10 pages, 7 figure

The ScS precursors for the study of the lowermost mantle

The exploration of the lowermost-mantle structures by means of body waveform modeling allows the small-scale detection of heterogeneity and anomalous layers. In some regions the D00 layer presents a discontinuity at its top that seems to be a local feature. This anomalous reflector may be recognized by the detection of a small core-reflected phases precursor. These studies may present different order of problems. The main difficulties, are connected to the identification of the precursor and its association to the D00 region. Misunderstandings often result because of phases produced by heterogeneity and anisotropy along and in the vicinity of the ray paths, in the crust and mantle structures. These complexities are increased when large dataset and recording arrays, which may facilitate the waveform analysis, are not available. In this paper we discuss the body waveform modeling of lower-mantle phases for the study of the D00 with particular focus on the case of sparse data with only few events and stations available

What sets the magnetic field strength and cycle period in solar-type stars?

Two fundamental properties of stellar magnetic fields have been determined by observations for solar-like stars with different Rossby numbers (Ro), namely, the magnetic field strength and the magnetic cycle period. The field strength exhibits two regimes: 1) for fast rotation it is independent of Ro, 2) for slow rotation it decays with Ro following a power law. For the magnetic cycle period two regimes of activity, the active and inactive branches, also have been identified. For both of them, the longer the rotation period, the longer the activity cycle. Using global dynamo simulations of solar like stars with Rossby numbers between ~0.4 and ~2, this paper explores the relevance of rotational shear layers in determining these observational properties. Our results, consistent with non-linear alpha^2-Omega dynamos, show that the total magnetic field strength is independent of the rotation period. Yet at surface levels, the origin of the magnetic field is determined by Ro. While for Ro<1 it is generated in the convection zone, for Ro>1 strong toroidal fields are generated at the tachocline and rapidly emerge towards the surface. In agreement with the observations, the magnetic cycle period increases with the rotational period. However, a bifurcation is observed for Ro~1, separating a regime where oscillatory dynamos operate mainly in the convection zone, from the regime where the tachocline has a predominant role. In the latter the cycles are believed to result from the periodic energy exchange between the dynamo and the magneto-shear instabilities developing in the tachocline and the radiative interior.Comment: 43 pages, 14 figures, accepted for publication in The Astrophysical Journa

Upper mantle compressional velocity structure beneath the West Mediterranean Basin

P waveforms of regional crustal earthquakes have been modeled to obtain an upper mantle compressional velocity model for the West Mediterranean Basin. Data come from long-period stations of the World-Wide Standardized Seismograph Network and broadband stations located in the Iberian Peninsula. Synthetic waveforms have first been computed for published velocity models corresponding to different tectonic provinces and obtained with analogous techniques. A model that strongly improves the fits to the data is then derived. The proposed model is characterized by a 100-km-thick lid overlaying a not very pronounced low-velocity zone and a 3% discontinuity at 368 km where an increase of the velocity gradient also occurs. These features could be explained either as a deflection of the olivine-to-spinel phase transition, regionally detected at about 395 km, resulting from the lower temperature produced by the subduction of the African plate, or as being due to the presence below 300 km depth of a layer of silicate melt, producing a strong reflection from its bottom, and a more usual depth for the olivine-spinel transition. In both cases the occurrence of relatively low velocities beneath 300 km is interpreted as being caused by the presence of melt associated with the northward dipping subduction of the African plate

Elementary seismological analysis applied to the April 6, 2009 L'Aquila mainshock and its larger aftershock

To understand the source complexity of the April 6, 2009 L’Aquila earthquake (MW = 6.3), a quick seismological analysis is done on the waveforms of the mainshock and the larger aftershock that occurred on April 7, 2009. We prove that a simple waveform analysis gives useful insights into the source complexity, as soon as the seismograms are available after the earthquake occurrence, whereas the reconstruction of the rupture dynamics through the application of sophisticated techniques requires a definitely longer time. We analyzed the seismograms recorded at broadband and strong motion stations and provided firm constraints on rupture kinematics, slip distribution, and static surface deformation, also discriminating the actual fault plane. We found that two distinct rupture patches associated with different fracture propagation directions and possibly occurring on distinct rupture planes, characterized the source kinematics of the April 6 events. An initial updip propagation successively proceeds toward SE, possibly on a different plane. We also show that the same processing, applied to the April 7, 2009 aftershock (MW = 5.6), allows us to obtain useful information also in the case of lower magnitude events. Smaller events with similar location and source mechanism as the mainshock, to be used as Green’s empirical function, occur in the days before or within tens of minutes to a few hours after the mainshock. These quick, preliminary analyses can provide useful constraints for more refined studies, such as inversion of data for imaging the rupture evolution and the slip distribution on the fault plane. We suggest implementing these analyses for real, automatic or semi-automatic, investigations

Blending process assessment and employees competencies assessment in very small entities

The ISO/IEC 29110 series aims to provide Very Small Entities (VSEs) with a set of standards based on subsets of existing standards. Process capability determination does not seem suitable for a VSE in terms of return on investment. Our approach proposes to move the viewpoint away from process and to the human resources. We propose a blended assessment model using the ISO/IEC 15504 for the level 1, but based on competency assessment for higher capability levels