Quantum Phase Transitions in the Interacting Boson Model: Integrability, level repulsion and level crossing

We study the quantum phase transition mechanisms that arise in the Interacting Boson Model. We show that the second-order nature of the phase transition from U(5) to O(6) may be attributed to quantum integrability, whereas all the first-order phase transitions of the model are due to level repulsion with one singular point of level crossing. We propose a model Hamiltonian with a true first-order phase transition for finite systems due to level crossings.Comment: Accepted in PR

Thermal diagnostic of the Optical Window on board LISA Pathfinder

Vacuum conditions inside the LTP Gravitational Reference Sensor must comply with rather demanding requirements. The Optical Window (OW) is an interface which seals the vacuum enclosure and, at the same time, lets the laser beam go through for interferometric Metrology with the test masses. The OW is a plane-parallel plate clamped in a Titanium flange, and is considerably sensitive to thermal and stress fluctuations. It is critical for the required precision measurements, hence its temperature will be carefully monitored in flight. This paper reports on the results of a series of OW characterisation laboratory runs, intended to study its response to selected thermal signals, as well as their fit to numerical models, and the meaning of the latter. We find that a single pole ARMA transfer function provides a consistent approximation to the OW response to thermal excitations, and derive a relationship with the physical processes taking place in the OW. We also show how system noise reduction can be accomplished by means of that transfer function.Comment: 20 pages, 14 figures; accepted for publication in Class. Quantum Gra

Epistemología, caos y enseñanza de las ciencias

In this article it is maintained that modern science is going through a critical period where its epistemological assumptions and the use of a parcelling and reductionist methodology are questioned. This will surely have important implications in the teaching of the sciences, perhaps because the world today demands above all an epistemological change in the people who, within a few years, will occuppy the posts in the production and reproduction of scientific and technical knowledge

Manual for inspection of sprayers in use and PRITEAF, dedicated software for inspection of sprayers: success tools developed for the inspector’s training process in Spain

Software dedicated to inspection of sprayers in use has been developed with the aim to facilitate the accomplishment of the mandatory requirements from EU Directive for a Sustainable Use of Pesticides, specifically those concerning the inspection of sprayers in use. The software- PRITEAF- has been developed according to the European standards EN 13790 concerning mandatory inspection of sprayers in use and it is ready to be used not only for inspectors among all the EU members but also for training purposes all over the world. The software is ready to be on line –after minor arrangements - with the recently approved new international inspection standards ISO 16122, and its main features are: to facilitate the sprayer’s inspection procedure, to manage, storage and transfer all the information to the official bodies in charge of the procedure, and to be used as a support tool to improve the training activities during the process, according the European Directive 2009/128/CE for a Sustainable Use of Pesticides. For this purpose, PRITEAF has been designed for three different types of users: inspection teams, inspection workshops and regional authorities. PRITEAF has been developed using the File Maker Pro package and it is composed of three databases – inspections activities, database on sprayers already inspected, and owners or official responsible for the agricultural activity. The software is completed with specific modules for data acquisition and for generating official reports, files and communications. For its implementation, PRITEAF uses specific hardware (a PC server, a tablet and local Wi-Fi) necessary to ensure proper data collection in the field. After data collection, the software generates an official inspection report and an inspection certificate, as required by law. Using PRITEAF reduces inspection time by 33% compared to traditional sprayer inspection systems. Following its validation, PRITEAF has been made available to regional authorities and inspection workshops across Spain, and is also being used to train all inspection teams in the country. More than 800 inspectors have been officially trained using the developed software, resulting in an interesting tool to improve the daily activities to be executed in all the inspection’s workshops in Europe

An intrinsic state for an extended version of the interacting boson model

An intrinsic-state formalism for IBM-4 is presented. A basis of deformed bosons is introduced which allows the construction of a general trial wave function which has Wigner's spin-isospin SU(4) symmetry as a particular limit. Intrinsic-state calculations are compared with exact ones showing good agreement.Comment: 12 pages, TeX (ReVTeX). Content changed. Accepted in Phys. Rev.

Study on the effects of using a carbon dioxide atmosphere on the properties of vine shoots-derived biochar

This study analyzes the effects of using a different atmosphere (pure N2 or pure CO2) at two levels of absolute pressure (0.1 and 1.1 MPa) on the pyrolysis of vine shoots at a constant peak temperature of 600 °C. Recycling CO2 from residual flue gases into the pyrolysis process may be economically beneficial, since CO2 can replace the use of an expensive N2 environment. In addition, the use of a moderate pressure (e.g., 1.1 MPa) can result in higher carbonization efficiencies and an improvement in the pyrolysis gas (in terms of yield and composition). Results from our study suggest that the use of CO2 instead of N2 as pyrolysis environment led to similar carbonization efficiencies (i.e., fixed-carbon yields) and mass yields of biochar. The chemical properties related to the potential stability of biochar (i.e., fixed-carbon content and molar H:C and O:C ratios) were very similar for both pyrolysis atmospheres. Under an atmosphere of CO2, the yield of produced CO2 was drastically decreased at the expense of an increase in the yield of CO, probably as a consequence of the promotion of the reverse Boudouard reaction, especially at high pressure. The enhanced reverse Boudouard reaction can also explain the relatively high BET specific surface area and the macro-porosity development observed for the biochar produced under a CO2 environment at 1.1 MPa. In summary, the pressurized pyrolysis of biomass under an atmosphere of CO2 appears as a very interesting route to produce highly stable and porous biochars and simultaneously improving the yield of CO

The platinum nuclei: concealed configuration mixing and shape coexistence

The role of configuration mixing in the Pt region is investigated. For this chain of isotopes, the nature of the ground state changes smoothly, being spherical around mass $A\sim 174$ and $A\sim 192$ and deformed around the mid-shell N=104 region. This has a dramatic effect on the systematics of the energy spectra as compared to the systematics in the Pb and Hg nuclei. Interacting Boson Model with configuration mixing calculations are presented for gyromagnetic factors, $\alpha$-decay hindrance factors, and isotope shifts. The necessity of incorporating intruder configurations to obtain an accurate description of the latter properties becomes evident.Comment: Accepted in Physical Review

Anharmonic double-phonon excitations in the interacting boson model

Double-$\gamma$ vibrations in deformed nuclei are analyzed in the context of the interacting boson model. A simple extension of the original version of the model towards higher-order interactions is required to explain the observed anharmonicities of nuclear vibrations. The influence of three- and four-body interactions on the moments of inertia of ground- and $\gamma$-bands, and on the relative position of single-$\gamma$ and double-$\gamma$ bands is studied in detail. As an example of a realistic calculation, spectra and transitions of the highly $\gamma$-anharmonic nuclei $^{164}$Dy, $^{166}$Er, and $^{168}$Er are interpreted in this approach.Comment: 38 pages, TeX (ReVTeX). 15 ps figures. Submitted to Phys. Rev.

The U(5)-O(6) transition in the Interacting Boson Model and the E(5) critical point symmetry

The relation of the recently proposed E(5) critical point symmetry with the interacting boson model is investigated. The large-N limit of the interacting boson model at the critical point in the transition from U(5) to O(6) is obtained by solving the Richardson equations. It is shown explicitly that this algebraic calculation leads to the same results as the solution of the Bohr differential equation with a $\beta^4$ potential.Comment: Accepted in PR