Dynamics of Rough Interfaces in Chemical Vapor Deposition: Experiments and a Model for Silica Films

We study the surface dynamics of silica films grown by low pressure chemical vapor deposition. Atomic force microscopy measurements show that the surface reaches a scale invariant stationary state compatible with the Kardar-Parisi-Zhang (KPZ) equation in three dimensions. At intermediate times the surface undergoes an unstable transient due to shadowing effects. By varying growth conditions and using spectroscopic techniques, we determine the physical origin of KPZ scaling to be a low value of the surface sticking probability, related to the surface concentration of reactive groups. We propose a stochastic equation that describes the qualitative behavior of our experimental system.Comment: 5 two-column pages, Revtex, 5 figures, to appear in Phys. Rev. Let

Uniqueness of limit cycles for quadratic vector fields

Producción CientíficaThis article deals with the study of the number of limit cycles surrounding a critical point of a quadratic planar vector field, which, in normal form, can be written as x ′ = a1x − y − a3x 2 + (2a2 + a5)xy+a6y 2 , y ′ = x+a1y+a2x 2+(2a3+a4)xy−a2y 2 . In particular, we study the semi-varieties defined in terms of the parameters a1, a2, . . . , a6 where some classical criteria for the associated Abel equation apply. The proofs will combine classical ideas with tools from computational algebraic geometry.Agencia Estatal de Investigación - Fondo Europeo de Desarrollo Regional (grant MTM 2011-22751)Junta de Extremadura (grant GR15055)Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (grant MTM2015-65764-C3-1-P

Magnetization Study of the Heavy-Fermion System Yb(Rh1-xCox)2Si2 and of the Quantum Magnet NiCl2-4SC(NH2)2

This thesis presents a comprehensive study of the magnetic properties and of quantum phase transitions (QPTs) of two different systems which have been investigated by means of low-temperature magnetization measurements. The systems are the heavy-fermion Yb(Rh1-xCox)2Si2 (metallic) and the quantum magnet NiCl2-4SC(NH2)2 (insulator). Although they are very different materials, they share two common properties: magnetism and QPTs. Magnetism originates in Yb(Rh1-xCox)2Si2 from the trivalent state of the Yb3+ ions with effective spin S = 1=2. In NiCl2-4SC(NH2)2, the magnetic Ni2+ ions have spin S = 1. These magnetic ions are located on a body-centered tetragonal lattice in both systems and, in this study, the QPTs are induced by an external magnetic field. In Yb(Rh1-xCox)2Si2 the evolution of magnetism from itinerant in slightly Co-doped YbRh2Si2 to local in YbCo2Si2 is examined analyzing the magnetic moment versus chemical pressure x phase diagram in high-quality single crystals, which indicates a continuous change of dominating energy scale from the Kondo to the RKKY one. The physics of the antiferromagnet YbCo2Si2 can be completely understood. On the other hand, the physics of pure and slightly Co-containing YbRh2Si2 is much more complex, due to the itinerant character of magnetism and the vicinity of the system to an unconventional quantum critical point (QCP). The field-induced AFM QCP in Yb(Rh0.93Co0.07)2Si2 and in pure YbRh2Si2 under a pressure of 1.5GPa is characterized by means of the magnetic Grüneisen ratio. The final part of this thesis describes quantum criticality near the field-induced QCP in NiCl2-4SC(NH2)2 . These results will be compared to the theory of QPTs in Ising and XY antiferromagnets. Since the XY -AFM ordering can be described as BEC of magnons by mapping the spin-1 system into a gas of hardcore bosons, the temperature dependence of the magnetization for a BEC is analytically derived and compared to the results just below the critical field. The remarkable agreement between the BEC theory and experiments in this quantum magnet is one of the most prominent examples of the concept of universality.:1 Introduction 1 2 Theoretical concepts 5 2.1 Ce- and Yb-based 4f-electron systems . . . . . . . . . . . . . . . . 5 2.1.1 Crystalline electric field . . . . . . . . . . . . . . . . . . . . 6 2.2 Heavy-fermion systems . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.1 Fermi liquid theory . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.2 Kondo eff ect . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.3 RKKY interaction . . . . . . . . . . . . . . . . . . . . . . . 11 2.2.4 Doniach phase diagram . . . . . . . . . . . . . . . . . . . . . 12 2.3 Quantum phase transitions . . . . . . . . . . . . . . . . . . . . . . . 14 2.3.1 Spin density wave scenario . . . . . . . . . . . . . . . . . . . 16 2.3.2 Local quantum critical point scenario . . . . . . . . . . . . . 17 2.3.3 Global phase diagram . . . . . . . . . . . . . . . . . . . . . 18 2.3.4 The Grüneisen ratio . . . . . . . . . . . . . . . . . . . . . . 21 2.4 Spins are almost bosons . . . . . . . . . . . . . . . . . . . . . . . . 22 3 Experimental methods 31 3.1 Magnetization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.1.1 Magnetization measurements . . . . . . . . . . . . . . . . . 32 3.2 Experimental techniques . . . . . . . . . . . . . . . . . . . . . . . . 34 3.2.1 Faraday magnetometer . . . . . . . . . . . . . . . . . . . . . 35 3.2.1.1 Measurement of the force . . . . . . . . . . . . . . 35 3.2.1.2 Capacitive cell . . . . . . . . . . . . . . . . . . . . 35 3.2.1.3 Design and performance of the cell . . . . . . . . . 37 3.2.1.4 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . 42 3.2.1.5 Background contributions . . . . . . . . . . . . . . 42 3.2.1.6 Calibration . . . . . . . . . . . . . . . . . . . . . . 42 3.2.1.7 Magnets characteristics . . . . . . . . . . . . . . . 44 3.2.1.8 Installation in a dilution refrigerator . . . . . . . . 45 3.2.2 SQUID magnetometer . . . . . . . . . . . . . . . . . . . . . 47 3.3 Magnetization measurements at high pressure . . . . . . . . . . . . 48 3.3.1 Experimental setup for M(H - T) under pressure . . . . . . . 50 4 Yb(Rh1-xCox)2Si2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 4.1 Introduction and motivation . . . . . . . . . . . . . . . . . . . . . . 51 4.1.1 The heavy-fermion compound YbRh2Si2 . . . . . . . . . . . 53 4.1.2 The antiferromagnet YbCo2Si2 . . . . . . . . . . . . . . . . 58 4.1.3 Isoelectronic substitution of Co for Rh: Yb(Rh1-xCox)2Si2 . . . .62 4.2 Itinerant vs. local magnetism in Yb(Rh1-xCox)2Si2 . . . . . . . . . 67 4.2.1 Magnetization of Yb(Rh1-xCox)2Si2 with 0 x 0.27 . . . 67 4.2.1.1 YbRh2Si2 and Yb(Rh0.93Co0.07)2Si2 . . . . . . . . . 67 4.2.1.2 Yb(Rh0.88Co0.12)2Si2 . . . . . . . . . . . . . . . . . 71 4.2.1.3 Yb(Rh0.82Co0.18)2Si2 . . . . . . . . . . . . . . . . . 73 4.2.1.4 Yb(Rh0.73Co0.27)2Si2 . . . . . . . . . . . . . . . . . 74 4.2.1.5 Summary . . . . . . . . . . . . . . . . . . . . . . . 78 4.2.2 Magnetization of Yb(Rh1-xCox)2Si2 with x = 0.58 and x = 1 . . . . . 79 4.2.3 Evolution from itinerant to local magnetism . . . . . . . . . 83 4.3 Field-induced QCP in Yb(Rh0.93Co0.07)2Si2 . . . . . . . . . . . . . . 88 4.4 YbRh2Si2 under hydrostatic pressure . . . . . . . . . . . . . . . . . 96 4.4.1 Magnetization vs. field . . . . . . . . . . . . . . . . . . . . . 97 4.4.2 Comparison with 1.28 GPa . . . . . . . . . . . . . . . . . . . 99 4.4.3 Magnetization vs. temperature . . . . . . . . . . . . . . . . 101 4.4.4 Field-induced QCP at 1.5 GPa . . . . . . . . . . . . . . . . 103 4.4.5 The magnetic Grüneisen ratio . . . . . . . . . . . . . . . . . 105 4.5 The magnetic phase diagrams of YbCo2Si2 . . . . . . . . . . . . . . 107 4.5.1 Magnetization vs. temperature . . . . . . . . . . . . . . . . 107 4.5.2 Magnetization vs. fi eld . . . . . . . . . . . . . . . . . . . . . 109 4.5.3 H - T phase diagrams . . . . . . . . . . . . . . . . . . . . 114 4.5.4 Ac-susceptibility . . . . . . . . . . . . . . . . . . . . . . . . 117 4.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 5 NiCl2-4SC(NH2)2 . . . . . . . . . . . . . . . . . . . . . . . .121 5.1 Introduction and motivation . . . . . . . . . . . . . . . . . . . . . . 121 5.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.2.1 Magnetization . . . . . . . . . . . . . . . . . . . . . . . . . . 124 5.2.2 Comparison between theory and experiment . . . . . . . . . 126 5.2.3 Magnetic phase diagram . . . . . . . . . . . . . . . . . . . . 129 5.2.4 Speci c heat . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 5.2.5 The magnetic Grüneisen ratio . . . . . . . . . . . . . . . . . 131 5.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 6 General conclusions . . . . . . . . . . . . . . . . . . . . . . . .135 Appendix 1 . . . . . . . . . . . . . . . . . . . . . . . .13

The effect of Six Sigma on corporate performance in the manufacturing and service sectors

As global competition becomes more intense, organizations try to implement strategies that allow them become more efficient, increase quality and productivity, and stay ahead of their competition. Over the years, there have been different programs or methodologies that companies have adopted with the purpose of achieving enhanced operational performance and bottom line impact. Six Sigma is one of the strategies that have gained more popularity during recent years, being adopted by companies in both manufacturing and service. There have been numerous claims by adopting companies about the financial benefits of implementing Six Sigma. However, the number of studies conducting empirical research to back those claims is limited. ^ The purpose of this study was to evaluate whether Six Sigma impacts corporate performance and the extent to which that impact is similar for manufacturing and service companies. The study was conducted by selecting a sample of 48 companies, within the manufacturing and service sectors, and assessing the effect of Six Sigma adoption by comparing their financial performance with the performance of control companies that did not implement Sig Sigma, during a period of 8 years after implementation. The statistical results provided evidence to conclude that Six Sigma has a positive effect on financial performance in the long term, showing significant results for years 7 and 8 after implementation, with the sample companies outperforming their corresponding control companies for these periods of time. The results were consistent in both manufacturing and service for year 8, validating that the impact of Six Sigma is similar for both sectors

Regresividad fiscal y redistribución regulatoria. (El núcleo del Análisis Económico del Derecho Público en la obra de Villar Palasí)

La regulación es considerada por Villar Palasí como un remedio necesario frente a la regresividad de los sistemas tributarios modernos, que dependen críticamente de los impuestos indirectos para mantener la recaudación y no cuentan con estructuras presupuestarias fiables para la reasignación de rentas. Este núcleo central de sus aportaciones al Análisis Económico del Derecho público está conectado con el neoclasicismo económico y la Economía del Bienestar, según se explica en este artículo. La noción de precio justo, de la que Villar ofrece una síntesis prodigiosa sobre la base de un conocimiento exhaustivo de la historia de las ideas, es empleada para definir la misión redistributiva de la Administración mediante regulación. Las elaboraciones de Villar son especialmente útiles para comprender la difícil situación actual de las balanzas fiscales y las instituciones de acción colectiva.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Monetización del déficitl público y compra de deuda soberana por el BCE/SEBC

La contribución se ha enmarcado en un panel específico sobre aplicación del análisis económico del derecho a la regulación financiera y bancaria1. La compra de deuda soberana tiene siempre un efecto de monetización del déficit, se adquiera en mercado primario o secundario. Sin perjuicio de sus consecuencias inflacionarias y, por tanto, redistributivas, esta práctica supone una violación del art. 123.1 del TFUE. 2. La prohibición de financiación monetaria de los Estados miembros por el BCE/SEBC está enraizado en un elemento de polaridad clave en el proyecto europeo, que consiste en el otorgamiento en exclusiva a aquellos por el Derecho primario de la UE de las competencias de política fiscal y económica. La compra de deuda pública por el BCE/SEBC es, por tanto, una actuación incompatible con el marco constitucional de la UE. 3. Habría, por tanto, que sacar del ámbito comunitario los medios de ayuda financiera a los Estados miembros, a través de instrumentos intergubernamentales (MEEF/MEDE), sin participación del BCE/SEBC. Dichos instrumentos deberían quedar complementados por un nuevo sistema paneuropeo de mercado para la reestructuración de deuda pública en casos de default soberano. 4. El único efecto real y contrastable de los programas de compra de deuda soberana ha sido la reducción significativa de los tipos de interés de mercado de las emisiones, sin que pueda apreciarse un impacto relevante sobre el incremento de los flujos de crédito de los bancos comerciales hacia los agentes productivos, ni tampoco sobre la inflación. Esto significaría, sencillamente, que carece de fundamento la idea, amparada por el TJUE, de que la incidencia tan significativa del BCE/SEBC en los mercados de deuda pública sea una condición indispensable de transmisión de los efectos de la política monetaria a la economía real. 5. Se produce un quebranto en el escenario representativo de la moneda única. El BCE/SEBC ha llevado a cabo actuaciones destructivas de valor capaces de hacer del euro un signo que no significa valor y, en consecuencia, no puede ni causarlo, ni transmitirlo, ni preservarlo.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Universidad Católica Portugues

En el diván del ecoanálisis

Esta comunicación tiene por finalidad aportar algunas reflexiones críticas sobre ciertas ideas predominantes en la corriente del Análisis Económico del Derecho (AED) y, más en concreto, del Derecho público. El núcleo fundamental del trabajo se sitúa en una revisión de los postulados neoclásicos del AED, sobre todo de los soportes intelectuales de los teoremas generales de equilibrio y su relación con la Economía del Bienestar. Se sostiene que la regulación de sectores, el propio Derecho de la competencia, la definición del sistema impositivo y de la balanza fiscal de las Administraciones y del sector público están profundamente influenciados por concepciones erróneas basadas en un óptimo estático de equilibrio que distorsiona las decisiones sobre políticas públicas. Esta distorsión se estima particularmente lesiva en el ámbito de las instituciones que instrumentan la actuación de las Administraciones, habitualmente sesgadas por planteamientos intervencionistas y frontalmente contrarios al funcionamiento de la competencia como orden espontáneo. La estructura fundamental de este trabajo está soportada por un análisis de la literatura económica que se ha estimado más relevante, con el propósito de hacer asequible su contenido a iuspublicistas no expertos en economía, a quienes se sugieren cautelas para evitar que den por sentada la solidez y consistencia de la teoría económica predominante para el análisis de las instituciones del Derecho público. A modo de conclusiones, se señala la prioridad del correcto entendimiento de los incentivos que dirigen la dinámica institucional de la acción colectiva y se enfatiza la necesidad de que los juristas pongan al servicio de la gobernanza pública una mentalidad abierta y atenta a la citada dinámica institucional.Asociación Española de Derecho y Economía (AEDE), Universidad de Granada. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

EU policy responses to Covid-19: effects on money growth, inflation, and spending

This working paper contains some reflections on the potential consequences of the Eurozone’s policy response to the Covid-19. Let's summarise them in the following bullet points: • No fiscal contraction nor money supply reduction might be expected over a period of 3-4 years. Both government deficit/debt and M3 aggregate might continue to rise to even more unprecedented amounts, at least in peacetime. The ECB’s balance-sheet operations would accompany public budget expansions to prevent the Eurozone’s government´s policies from financial market punishment. • As a result, austerity policies, based on fiscal contractions (public spending reduction and tax cuts) are not in the Eurozone’s medium-long run horizon. Taxes simply take resources away from productive activities and cause distortions to market operators. Aggregate demand multipliers are formidable theoretical artefacts that take for granted the absence of pro-cyclical effects. A great deal of research has recently been done to refute the Keynesian tradition on the robust historical dataset. • Getting back to monetary stability would be much tougher for the Eurozone than it should be in rational terms. Sadly, I recognise that the EU’s constitutional counterfeits facilitate rather than refrain from monetary disequilibria. In the absence of an EU centralised (federal), lithe governmental decision-making (comitology is omnipresent), the ECB rises like the saviour for all seasons in the shape of a universal liquidity provider. • Effectively, double-digit inflation would be the inevitable consequence of the failure of a rule-based monetary strategy for the Eurozone. Along with it, weak productivity recovery and private sector zombification pave the path to Japan-like stagflation.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

In the mood for liquidity: non-banks in the shadow of banks & fintechs.

The main of the author goes to the restrictions on the means for liquidity derived from the last decade’s regulatory trends. My contention is about the severe distortions caused to all stakeholders and economic agents by the Humpty-Dumpty mantra of (global) financial stability, which entails a number of overlapping controls directed to channel every single stream of liquidity to the banking sector, devised as a mere elongation of central banks and regulatory authorities. To spur the debate, I’d like to pose a couple of questions: (1) does it make sense the financial repression exercise over OTCs through the duties of notice to the regulators? (2) does the unprecedented proliferation of ETFs since the GFC show the flight by investors from conventional financial vehicles which are seen as unreliable and too close to politicians’ hands? In a nutshell, we would be in the way to forget that liquidity is inevitably about short-term gains and losses, not about money printing, and the adequate discernment of credit risk is the specific role of commercial banks in a market economy; that of the central banks is last resort lending at a penalty rate, and against good collateral, but to commercial banks, not to States.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec