Integrals of motion in the Many-Body localized phase

We construct a complete set of quasi-local integrals of motion for the many-body localized phase of interacting fermions in a disordered potential. The integrals of motion can be chosen to have binary spectrum $\{0,1\}$, thus constituting exact quasiparticle occupation number operators for the Fermi insulator. We map the problem onto a non-Hermitian hopping problem on a lattice in operator space. We show how the integrals of motion can be built, under certain approximations, as a convergent series in the interaction strength. An estimate of its radius of convergence is given, which also provides an estimate for the many-body localization-delocalization transition. Finally, we discuss how the properties of the operator expansion for the integrals of motion imply the presence or absence of a finite temperature transition.Comment: 65 pages, 12 figures. Corrected typos, added reference

Persistence and ability in the innovation decisions

The main concern of this paper is to analyse the complementarities between the decisions to carry out both product and process innovations. We also try to identify the main determinants of the innovation activity as well as to separate the experience effect of the firm (capacities, routines as organization) from the experience effect of the manager (skills, abilities). It has been common when facing the study of technological change, to consider innovation as a homogeneous activity. The main analyses have focused on the determinants of such activity trying to explain decisions, counts or R and D expenses in the context of a unique activity. Several recent works, however, are worried about the possibility of analysing innovation distinguishing among different types according to the final purpose of this activity. We focus on two different decisions, product and process innovations, using typical discrete choice specifications (univariate and bivariate models) and also binary choice models with heterogeneity. Among the results, we find complementary but asymmetric effects concerning both decisions in static models even controlling heterogeneity. We also test whether the persistence in conducting innovation activities matter. We do so in an extensive database that provides information about manufacturing firms. Our results point towards the importance of both ability of the manager (unobserved heterogeneity) and experience of the firm (dynamics in the equation indicator)

Absolute kinematics of radio source components in the complete S5 polar cap sample. III. First wide-field high-precision astrometry at 15.4 GHz

We report on the first wide-field, high-precision astrometric analysis of the 13 extragalactic radio sources of the complete S5 polar cap sample at 15.4 GHz. We describe new algorithms developed to enable the use of differenced phase delays in wide-field astrometric observations and discuss the impact of using differenced phase delays on the precision of the wide-field astrometric analysis. From this global fit, we obtained estimates of the relative source positions with precisions ranging from 14 to 200 $\mu$as at 15.4 GHz, depending on the angular separation of the sources (from $\sim$1.6 to $\sim$20.8 degrees). These precisions are $\sim$10 times higher than the achievable precisions using the phase-reference mapping technique.Comment: 9 pages, 7 figure

Adapting robot behavior to user's capabilities: a dance instruction study.

The ALIZ-E1 projects goal is to design a robot companion able to maintain affective interactions with young users over a period of time. One of these interactions consists in teaching a dance to hospitalized children according to their capabilities. We propose a methodology for adapting both, the movements used in the dance based on the users cognitive and physical capabilities through a set of metrics, and the robots interaction based on the users personality traits

PERSISTENCE AND ABILITY IN THE INNOVATION DECISIONS

The main concern of this paper is to analyse the complementarities between the decisions to carry out both product and process innovations. We also try to identify the main determinants of the innovation activity as well as to separate the experience effect of the firm (capacities, routines as organization) from the experience effect of the manager (skills, abilities). It has been common when facing the study of technological change, to consider innovation as a homogeneous activity. The main analyses have focused on the determinants of such activity trying to explain decisions, counts or R&D expenses in the context of a unique activity. Several recent works, however, are worried about the possibility of analysing innovation distinguishing among different types according to the final purpose of this activity. We focus on two different decisions, product and process innovations, using typical discrete choice specifications (univariate and bivariate models) and also binary choice models with heterogeneity. Among the results, we find complementary but asymmetric effects concerning both decisions in static models even controlling heterogeneity. We also test whether the persistence in conducting innovation activities matter. We do so in an extensive database that provides information about manufacturing firms. Our results point towards the importance of both ability of the manager (unobserved heterogeneity) and experience of the firm (dynamics in the equation indicator).

Discovery of Solar Rieger Periodicities in Another Star

The Rieger periods are solar cycles with a time scale of months, which are present in both flaring activity and sunspot occurrence. These short-term periodicities, tentatively explained by equatorially trapped Rossby-type waves modulating the emergence of magnetic flux at the surface, are considered a peculiar and not yet fully understood solar phenomenon. We chose a stellar system with solar characteristics, UX Arietis, and performed a timing analysis of two 9-year datasets of radio and optical observations. The analysis reveals a 294-day cycle. When the two 9-year datasets are folded with this period, a synchronization of the peak of the optical light curve (i.e., the minimum spot coverage) with the minimum radio flaring activity is observed. This close relationship between two completly independent curves makes it very likely that the 294-day cycle is real. We conclude that the process invoked for the Sun of a periodical emergence of magnetic flux may also be applied to UX Arietis and can explain the cyclic flaring activity triggered by interactions between successive cyclic emergences of magnetic flux.Comment: 4 Pages, 1 table, 3 figures (quality of Fig. 1 degraded to match the requested size), needs aa.cls, accepted to be published as a letter in Astronomy & Astrophysic

How to Mix Molecules with Mathematics

In this paper we develop two methods to calculate thermodynamic properties of mixtures. Starting point are the basic assumptions that also form the basis for the COSMO-RS model. In this approach, the individual molecules are represented by their geometrical shape with an electrical charge density on their surfaces. Next, the surface is split up into surface segments each with its own charge. In COSMO-RS a strong reduction is introduced by treating the segments as if they are completely independent. In the present study we take into account that the coupling between two patches is essentially dependent on the charge distribution on neighboring segments and on the local geometrical structure of the surface. Two approaches are followed. The first one points out how the model equations, which comprise the optimization of the entropy and conservation of internal energy, can efficiently be solved in general, thus also if the dependency between segments and the local geometry is included in the expression for the coupling energy between segments. In the second method the configuration with maximal entropy and prescribed energy is sought via simulation. Successive molecular configurations of the mixture are simulated and updated via a genetic algorithm to optimize the entropy. The second method is more time consuming but very general

Differential Astrometry over 15 degrees

We observed the pair of radio sources 1150+812 and 1803+784 in November 1993 with a VLBI array, simultaneously recording at 8.4 and 2.3 GHz. We determined the angular separation between the two sources with submilliarcsecond accuracy by using differential techniques. This result demonstrates the feasibility of high precision differential astrometry for radio sources separated in the sky by almost 15 degrees, and opens the avenue to its application to larger samples of radio sources.Comment: 6 pages, latex2e, 2 figures, To appear in the proceedings of the EVN/JIVE Symposium No. 4, New Astronomy Reviews (eds. Garret, M. Campbell, R., and Gurvits, L.