All macroscopic quantum states are fragile and hard to prepare

We study the effect of local decoherence on arbitrary quantum states. Adapting techniques developed in quantum metrology, we show that the action of generic local noise processes -- though arbitrarily small -- always yields a state whose Quantum Fisher Information (QFI) with respect to local observables is linear in system size N, independent of the initial state. This implies that all macroscopic quantum states, which are characterized by a QFI that is quadratic in N, are fragile under decoherence, and cannot be maintained if the system is not perfectly isolated. We also provide analytical bounds on the effective system size, and show that the effective system size scales as the inverse of the noise parameter p for small p for all the noise channels considered, making it increasingly difficult to generate macroscopic or even mesoscopic quantum states. In turn, we also show that the preparation of a macroscopic quantum state, with respect to a conserved quantity, requires a device whose QFI is already at least as large as the one of the desired state. Given that the preparation device itself is classical and not a perfectly isolated macroscopic quantum state, the preparation device needs to be quadratically bigger than the macroscopic target state

Cuando x = x, no significa lo mismo

Uno de los aspectos esenciales en el trabajo en matemáticas es la aceptación del principio de identidad, esto es X=X. Este principio se ha considerado, en los ámbitos educativos como verdad absoluta. Desde una perspectiva psicogenética se asume que los jóvenes acceden a éste como producto del desarrollo cognitivo (Piaget, 1985). Sin embargo, ante posturas filosóficas como la falibilista y dialógica (Ernest (2004), Sierpinska y Lerman (1996), este principio puede ser reconsiderado. La intención de este trabajo es doble, por un lado, determinar si en matemáticas, el principio de identidad puede ser evidente y asequible para los estudiantes de bachillerato, si éste se interpreta de manera unívoca y canónicamente o conlleva otras posibles interpretaciones, y por otro, explorar si esta aprehensión tiene relación con su desempeño en la materia

Dissecting the ΔI=1/2\Delta I= 1/2 rule at large NcN_c

We study the scaling of kaon decay amplitudes with the number of colours, $N_c$, in a theory with four degenerate flavours, $N_f=4$. In this scenario, two current-current operators, $Q^\pm$, mediate $\Delta S=1$ transitions, such as the two isospin amplitudes of non-leptonic kaon decays for $K\to (\pi\pi)_{I=0,2}$, $A_0$ and $A_2$. In particular, we concentrate on the simpler $K\to\pi$ amplitudes, $A^\pm$, mediated by these two operators. A diagrammatic analysis of the large-$N_c$ scaling of these observables is presented, which demonstrates the anticorrelation of the leading ${\mathcal O}(1/N_c)$ and ${\mathcal O}(N_f/N_c^2)$ corrections in both amplitudes. Using our new $N_f=4$ and previous quenched data, we confirm this expectation and show that these corrections are $naturally$ large and may be at the origin of the $\Delta I=1/2$ rule. The evidence for the latter is indirect, based on the matching of the amplitudes to their prediction in Chiral Perturbation Theory, from which the LO low-energy couplings of the chiral weak Hamiltonian, $g^\pm$, can be determined. A NLO estimate of the $K \to (\pi\pi)_{I=0,2}$ isospin amplitudes can then be derived, which is in good agreement with the experimental value.Comment: 12 pages, 7 figures. Minor change

Variability in non-invasive brain stimulation studies: reasons and results

Non-invasive brain stimulation techniques (NIBS), such as Theta Burst Stimulation (TBS), Paired Associative Stimulation (PAS) and transcranial Direct Current Stimulation (tDCS), are widely used to probe plasticity in the human motor cortex (M1). Although TBS, PAS and tDCS differ in terms of physiological mechanisms responsible for experimentally-induced cortical plasticity, they all share the ability to elicit long-term potentiation (LTP) and depression (LTD) in M1. However, NIBS techniques are all affected by relevant variability in intra- and inter-subject responses. A growing number of factors contributing to NIBS variability have been recently identified and reported. In this review, we have readdressed the issue of variability in human NIBS studies. We have first briefly discussed the physiological mechanisms responsible for TBS, PAS and tDCS-induced cortical plasticity. Then, we have provided statistical measures of intra- and inter-subject variability, as calculated in previous studies. Finally, we have reported in detail known sources of variability by categorizing them into physiological, technical and statistical factors. Improving knowledge about sources of variability could lead to relevant advances in designing new tailored NIBS protocols in physiological and pathological conditions

Modeling the live-pig trade network in Georgia: Implications for disease prevention and control.

Live pig trade patterns, drivers and characteristics, particularly in backyard predominant systems, remain largely unexplored despite their important contribution to the spread of infectious diseases in the swine industry. A better understanding of the pig trade dynamics can inform the implementation of risk-based and more cost-effective prevention and control programs for swine diseases. In this study, a semi-structured questionnaire elaborated by FAO and implemented to 487 farmers was used to collect data regarding basic characteristics about pig demographics and live-pig trade among villages in the country of Georgia, where very scarce information is available. Social network analysis and exponential random graph models were used to better understand the structure, contact patterns and main drivers for pig trade in the country. Results indicate relatively infrequent (a total of 599 shipments in one year) and geographically localized (median Euclidean distance between shipments = 6.08 km; IQR = 0-13.88 km) pig movements in the studied regions. The main factors contributing to live-pig trade movements among villages were being from the same region (i.e., local trade), usage of a middleman or a live animal market to trade live pigs by at least one farmer in the village, and having a large number of pig farmers in the village. The identified villages' characteristics and structural network properties could be used to inform the design of more cost-effective surveillance systems in a country which pig industry was recently devastated by African swine fever epidemics and where backyard production systems are predominant

El Impacto potencial de BEPS en los sistemas fiscales. “Cláusula General Antiabuso Tributaria”

Treballs Finals del Grau de d'Administració i Direcció d'Empreses, Facultat d'Economia i Empresa, Universitat de Barcelona, Curs: 2016-2017 , Tutora: Maria Teresa DivíEl presente trabajo tiene por objeto exponer una de las herramientas de fiscalidad internacional adoptada por todos los miembros de la OECD contra el fraude y la evasión fiscal: Las BEPS (Base Erosion and Profit Shifting), y en especial la acción 6 relativa a las medidas anti abuso en la normativa interna y en los convenios para evitar la doble imposición internacional. Se detallará cuál ha sido la reacción en nuestro país acerca de este pack de recomendaciones y medidas antiabuso para evitar la erosión de la base imponible y al traslado de beneficios y se comparará con las medidas introducidas en otros ordenamientos jurídicos de diferentes países miembros de la OECD. La información aportada en este trabajo se basa en gran parte a mi experiencia como asistente al Wintercourse del EUCOTAX 2016 (Universidad de Viena)

Creación de filial de sociedad dedicada a la alimentación

Traballo fin de grao (UDC.DER). Dereito. Curso 2014/201