Viscosity near phase transitions

Probably the most enticing observation in theoretical physics during the last decade was the discovery of the great amount of consequences obtained from the AdS/CFT conjecture put forward by Maldacena. In this work we review how this correspondence can be used to address hydrodynamic properties such as the viscosity of some strongly interacting systems. We also employ the Boltzmann equation for those systems closer to low-energy QCD, and argue that this kind of transport coefficients can be related to phase transitions, in particular the QGP/hadronic phase transition studied in heavy ion collisions.Comment: 9 pages, 1 figure. Contribution to the Gribov-80 Memorial Workshop. ICTP Trieste, Italy, May 26-28, 201

Los factores claves de la innovación tecnológica: claves de la competitividad empresarial

Actualmente la innovación tecnológica está impulsada por la investigación, por interacciones entre diferentes agentes y por el conocimiento científico-tecnológico, lo que pone de relieve que se trata de un proceso orientado a la resolución de problemas, que tiene su ocurrencia primaria en el mercado, que implica relaciones formales e informales entre diferentes agentes, además del intercambio de conocimiento tácito y explícito. Para abordar el análisis de esta influencia, en este trabajo se identifican los drivers o factores que caracterizan el proceso de innovación tecnológica y que pueden clasificarse en internos y externos. Actually, technological innovation is propelled by the research, the interactions between different agents and the scientific and technological knowledge. It is a process oriented towards the resolution of problems that occurs primarily in the market, implies formal and informal relations between agents and the exchange of tacit and explicit knowledge.This paper analyses the drivers that characterize the technological innovation process.They can be classifies in internal and external. Internal drivers depend of the managers capacity to consolidate the quality and productivity dimensions (short-run), and the possibility to create technologies, competences and aptitudes that generate new products or services more quickly than the competitors (long-run). External drivers are associated to the activity sector of the firm, to its institutional context and to the economic policy that affects it

Minimum of η/s\eta/s and the phase transition of the Linear Sigma Model in the large-N limit

We reexamine the possibility of employing the viscosity over entropy density ratio as a diagnostic tool to identify a phase transition in hadron physics to the strongly coupled quark-gluon plasma and other circumstances where direct measurement of the order parameter or the free energy may be difficult. It has been conjectured that the minimum of eta/s does indeed occur at the phase transition. We now make a careful assessment in a controled theoretical framework, the Linear Sigma Model at large-N, and indeed find that the minimum of eta/s occurs near the second order phase transition of the model due to the rapid variation of the order parameter (here the sigma vacuum expectation value) at a temperature slightly smaller than the critical one.Comment: 22 pages, 19 figures, v2, some references and several figures added, typos corrected and certain arguments clarified, revised for PR

eta/s is critical (at phase transitions)

The viscosity over entropy density ratio, or KSS number, can help isolate the critical point in the hadron phase-diagram in Relativistic Heavy Ion Collisions. We argue that this quantity does have a minimum at a phase transition or crossover. Although indications from conventional non-relativistic gases point out to even a divergence in eta/s when the phase-transition is first-order, since the critical exponent is rather low, this will be more difficult to ascertain in RHIC or FAIR. The experimental data are more likely to reveal a discontinuity for a first order phase transition or a smooth minimum at a crossover.Comment: 3-pages, 2 figures, contribution to XIII Mexican School of Particles and Fields, to be published in AIP-proceeding

η/s\eta/s and Phase Transitions

We present a calculation of eta/s for the meson gas (zero baryon number), with the viscosity computed within unitarized NLO chiral perturbation theory, and confirm the observation that eta/s decreases towards the possible phase transition to a quark-gluon plasma/liquid. The value is somewhat higher than previously estimated in LO chi PT. We also examine the case of atomic Argon gas to check the discontinuity of eta/s across a first order phase transition. Our results suggest employing this dimensionless number, sometimes called KSS number (in analogy with other ratios in fluid mechanics such as Reynolds number or Prandtl number) to pin down the phase transition and critical end point to a cross-over in strongly interacting nuclear matter between the hadron gas and quark and gluon plasma/liquid.Comment: Revised for PRD. Shorter (by one section) than first version. 6 pp, 4 figure

A process-specific approach in the study of normal aging deficits in cognitive control: What deteriorates with age?

Bearing in mind that cognitive control is a complex function that includes several processes, it is not clear exactly which ones deteriorate with age. In fact, controversial results have been found. For example, some studies indicate that age-related deficits are observed in proactive and not in reactive control, others show that it is reactive control that is impaired and not proactive control, and some studies find no deficits at all (e.g., Kopp, Lange, Howe, & Wessel, 2014; Xiang et al., 2016). One possible reason is that the contribution of different processes to the deterioration of cognitive control was investigated separately, i.e., without testing all processes within the same paradigm. Therefore, the main goal of the present experiment was to study the impact of normal aging on several processes related to cognitive control within the same task, which included both Simon and Spatial Stroop trials. The study focused on the following processes: generation of conflict measured by automatic response capture (i.e., stronger task-irrelevant information processing compared to task-relevant information processing); conflict detection; and control implementation (which can be reactive control, both within trials and across trials, and proactive control, as a task-set strategy). The results showed larger automatic response capture for older adults when facing a stimulus-response conflict (Simon) but not a stimulus-stimulus conflict (Spatial Stroop). Similarly, older adults also showed larger detection effects for both conflicts. However, regarding control implementation, they only showed difficulties in inhibiting the early automatic response capture (within-trial reactive control) but not reactive control across trials or proactive control. In conclusion, it seems that older adults are more affected by the presence of task-irrelevant information, especially when it comes to resolving stimulus-response conflict. However, they showed no impairments in their ability to implement cognitive control both across trials and as a task-set strategy

High Phenotypic Diversity Does Not Always Hide Taxonomic Diversity: A Study Case with Cheilosia soror (Zetterstedt, 1843) (Diptera: Syrphidae) in the Iberian Peninsula

Comprising nearly 500 species worldwide, Cheilosia Meigen is the largest genus of Syrphidae in the Palaearctic region. Within Cheilosia, phenotypic diversity has been assessed in different species groups, including the group of Cheilosia longula (Zetterstedt, 1838). However, the phenotypic variability of Cheilosia soror (Zetterstedt, 1843), a highly variable member of the C. longula group, has never been assessed in western Europe. In the present work, morphological and molecular analyses were conducted to assess the phenotypic variability found in 300+ specimens of C. soror from the Iberian Peninsula. A total of 16 variable characters were identified and defined for the C. soror morphology, with the highest variation found in the colour of the mesonotum pilosity and the metatibia colour. Morphological variation was assessed against molecular variation based on two molecular markers, one mitochondrial, the 5 end of the cytochrome c oxidase subunit I (COI-5), and one nuclear, the large subunit ribosomal DNA (28S). Phylogenetic analyses rendered trees with topologies in disagreement with the defined morphological variation. Two haplotypes were identified amongst the analysed specimens of C. soror, together with a haplotypic variant exclusive to the Iberian region. Potential distributions were used to identify unexplored areas of occurrence of C. soror and other species of the C. longula group in the Iberian Peninsula. Unassessed areas of occurrence of C. soror should be surveyed in the future to confirm the absence of hidden taxonomic diversity within the range of phenotypic variation for this species. Phenotypic variation of the other two Iberian species of the C. longula group, C. longula and C. scutellata (Fallén, 1817), was also assessed to find that they are species with less-variable morphology than C. soror and with molecular characters in accordance with other conspecific populations in Europe. New distributional data are provided for C. soror and C. scutellata from Spain, and a leg abnormality is identified for the first time in C. soror.This research was funded by the “Fauna Ibérica” project (PGC2018-095851-A-C65) of the Ministry of Science, Innovation, and Universities, Spain. Antonio Ricarte’s position (Ref. UATALENTO17-08) at the University of Alicante is funded by the “Vicerrectorado de Investigación y Transferencia del Conocimiento.” The positions of Zorica Nedeljković and Iván Ballester-Torres at the University of Alicante are funded by the above-mentioned Fauna Ibérica project