Quantum non-Markovian behavior at the chaos border

In this work we study the non-Markovian behaviour of a qubit coupled to an environment in which the corresponding classical dynamics change from integrable to chaotic. We show that in the transition region, where the dynamics has both regular islands and chaotic areas, the average non-Markovian behaviour is enhanced to values even larger than in the regular regime. This effect can be related to the non-Markovian behaviour as a function of the the initial state of the environment, where maxima are attained at the regions dividing separate areas in classical phase space, particularly at the borders between chaotic and regular regions. Moreover, we show that the fluctuations of the fidelity of the environment -- which determine the non-Markovianity measure -- give a precise image of the classical phase portrait.Comment: 23 pages, 9 figures (JPA style). Closest to published versio

A Systematic Review of The Potential Use of Neurofeedback in Patients with Schizophrenia.

Schizophrenia (SCZ) is a neurodevelopmental disorder characterized by positive symptoms (hallucinations and delusions), negative symptoms (anhedonia, social withdrawal) and marked cognitive deficits (memory, executive function, and attention). Current mainstays of treatment, including medications and psychotherapy, do not adequately address cognitive symptoms, which are essential for everyday functioning. However, recent advances in computational neurobiology have rekindled interest in neurofeedback (NF), a form of self-regulation or neuromodulation, in potentially alleviating cognitive symptoms in patients with SCZ. Therefore, we conducted a systematic review of the literature for NF studies in SCZ to identify lessons learned and to identify steps to move the field forward. Our findings reveal that NF studies to date consist mostly of case studies and small sample, single-group studies. Despite few randomized clinical trials, the results suggest that NF is feasible and that it leads to measurable changes in brain function. These findings indicate early proof-of-concept data that needs to be followed up by larger, randomized clinical trials, testing the efficacy of NF compared to well thought out placebos. We hope that such an undertaking by the field will lead to innovative solutions that address refractory symptoms and improve everyday functioning in patients with SCZ

The logarithmic contribution to the QCD static energy at NNNNLO

Using pNRQCD and known results for the field strength correlator, we calculate the ultrasoft contribution to the QCD static energy of a quark-antiquark pair at short distances at NNNNLO in alpha_s. At the same order, this provides the logarithmic terms of the singlet static potential in pNRQCD and the log alpha_s terms of the static energy.Comment: 16 pages, 5 figures. Minor modifications. References added. Journal versio

Manufactura dels Gobelins: la seva importància en el context de la tintura a la perifèria europea en el llindar del segle XX

Since 1827, the applications of chemical science to textile-dyeing processes were taught at the Chemistry School located in the «Atelier de teinture des Gobelins», in Paris. The school's director was Michel-Eugène Chevreul, whose renown brought to Paris students from several countries. Among them were Catalan an Spanish students, who attended the courses on fellowships endowed by their provincial governments («Diputaciones»). The new techniques those students learned with Mr. Chevreul were then taught in local schools and subsequently adopted by Catalan textile mills, becoming part of their ordinary procedures. This is an example of the transfer of scientific and technical knowledge to the European periphery in the second half of the nineteenth century. On the other hand, there is evidence pointing to a lasting association between Mr. Chevreul and one of his Catalan students, Josep Vallhonest