Localisation Transition in the Driven Aubry-Andr\'e Model

A recent experiment by P. Bordia et al. (Periodically Driving a Many Body Localized Quantum System, Nat Phys, Jan 2017) has demonstrated that periodically modulating the potential of a localised many-body quantum system described by the Aubry-Andr\'e Hamiltonian with on-site interactions can lead to a many-body localisation-delocalisation transition, provided the modulation amplitude is big enough. Here, we consider the noninteracting counterpart of that model in order to explore its phase diagram as a function of the strength of the disordered potential, the driving frequency and its amplitude. We will first of all mimic the experimental procedure of the experiment and use the even-odd sites imbalance as a parameter in order to discern between different phases. Then we compute the Floquet eigenstates and relate the localisation-delocalisation transition to their Inverse Participation Ratio. Both these approaches show that the delocalisation transition occurs for frequencies that are low compared to the bandwidth of the time independent model. Moreover, in agreement with the results of the experiment there is an amplitude threshold below which no delocalisation transition occurs. We estimate both the critical values for the frequency and the amplitude

Cana de açúcar: Indicadores de fertilidade física e vulnerabilidade do solo em Tucumán, Argentina

In a sugarcane experimental site (Famaillá, Tucumán, Argentina) there were determined the load-strain ratio, the pre-compression stresses and the compression indexes of unaltered soil samples. Test procedure was based on the methodology described in ASTM D 2435 03. Soil samples were soaked for 48 hours in order to reach the saturation state before being subjected to vertical pressures from 6 to 1478 kPa. The time of application was the necessary one to allow the drainage of excess water from the soil sample. Deformation of the soil sample was plotted as a function of the logarithm of the time. Voids ratio were established as a function of the logarithm of the pressure and, from this function, the mentioned parameters were calculated. Results obtained from the consolidation tests seem to show the effect of the history of loads exerted on the soil. There is a high gradient of reduction of void ratio, which tends to compromise the future physical integrity of the soil.Instituto de Ingeniería RuralFil: Tesouro, Mario Omar. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; ArgentinaFil: Roba, Marcos Andrés. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; ArgentinaFil: Romito, Angel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; ArgentinaFil: Neiman, Otto Erik. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; ArgentinaFil: Fernandez Ullivarri, Enrique. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Donato, Lidia Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; Argentin

Yields and economic results of sugarcane cultivation under an alternative system compared to traditional management

XXX Congress of the ISSCT (International Society of Sugar Cane Technologists), Tucumán, from 31 August to 8 September 2019In the traditional method of managing sugarcane in Argentina, the entire field where the crop will be planted is severely ploughed, requiring large amounts of energy. In addition, during the subsequent maintenance tasks, furrows are worked at depth, reducing their yielding capacity and making them more vulnerable to traffic from farming equipment, harvesters and heavy trucks. The use of this system during prolonged periods of monoculture affects the soil physical integrity, compromising yields and the efficient use of the inputs. It was necessary, therefore, to develop an enhanced alternative management system to the traditional one in order to revert, stop or mitigate soil deterioration and improve crop economic results. A possible solution was to use energy only where it could be harnessed by the roots of the crop and maintain, without disturbing, the traffic lanes throughout the cane cycle. In order to implement this form of controlled-traffic management, an experimental scarifier for deep strip-tillage was developed and manufactured. Since 2013, trials have been carried out at EEA INTA Famaillá (Tucumán) comparing both cultivation technologies. Results indicate that, during the cane production stage, fuel consumption, energy requirements and operating times and costs can be reduced by 60-70% with this new management system. The average gross margin over five harvests was approximately 15% than that of the traditional management system, due to an increase in yields and fewer maintenance tasks required by the new technology. The new system is presented as less operationally complex, economically profitable and a more sustainable management alternative.Instituto de Ingeniería RuralFil: Tesouro, Omar. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; ArgentinaFil: Fernandez Ullivarri, Enrique. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Venturelli, Leonardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; ArgentinaFil: Roba, Marcos. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; ArgentinaFil: Romito, Angel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; ArgentinaFil: Donato, Lidia Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; ArgentinaFil: Bongiovanni, Rodolfo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Manfredi; ArgentinaFil: Erazzú, Luis Ernesto. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Fontana, Paola Daniela. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Peralta, Adriana. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; Argentin

Cultivo de caña en Famaillá: Estudio de caso. Propiedades físicas del suelo: Evolución e impacto en el rendimiento del cultivo

Entre los meses de junio y julio de 2013 se inició un ensayo de larga duración en la EEA Famaillá (Tucumán) a fin de probar diferentes tecnologías de cultivo en caña de azúcar. El área experimental posee suelos argiudoles ácuicos, con un prolongado historial de monocultivo de caña con el manejo tradicional de la zona. El diseño del ensayo es en bloques completos aleatorizados con parcelas divididas y tres repeticiones por tratamiento. Las unidades completas son las formas de cultivo, convencional y mediante labranza en franjas, mientras que las subparcelas, están definidas por la forma de cosecha. En las borduras de las parcelas se mantienen sitios sin alterar, a fin de poder monitorear la evolución del suelo abandonado a la vegetación natural. En este Informe Técnico se presenta la situación de los principales parámetros físicos del área experimental relevados durante el segundo año del ensayo (2014 ) y el rendimiento del cultivo. Las cargas ejercidas sobre el área de cultivo durante la cosecha convencional incrementaron sustancialmente la densidad aparente del horizonte A. Las subparcelas cosechadas de esta forma y que habían sido preparadas con el método tradicional de laboreo, se diferenciaron claramente de los sitios sin alterar. El efecto de los tratamientos y subtratamientos tuvo menor relevancia en el horizonte Bt 1. La resistencia media del perfil del suelo con labranza en franjas fue superior al obtenido con labranza convencional, pero se mantuvo más estable frente a los diferentes niveles de cargas aplicadas durante la cosecha. En la zona de influencia de las raíces del cultivo, la dureza del suelo resultó sensiblemente inferior cuando se utilizó la labranza en franjas. Los sitios sin alterar presentaron los perfiles de mayor resistencia debido a su menor contenido de humedad. Aún no se presentan diferencias significativas en el rendimiento del cultivo que reflejen las variaciones observadas en el estado del suelo.Instituto de Ingeniería RuralFil: Tesouro, Mario Omar. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural. Laboratorio de Terramecánica e Implantación de Cultivos; ArgentinaFil: Roba, Marcos Andrés. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural. Laboratorio de Terramecánica e Implantación de Cultivos; ArgentinaFil: Romito, Angel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural. Laboratorio de Terramecánica e Implantación de Cultivos; ArgentinaFil: Fernandez Ullivarri, Enrique. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Donato, Lidia Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural. Laboratorio de Terramecánica e Implantación de Cultivos; ArgentinaFil: Neiman, Otto Erik. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural. Laboratorio de Terramecánica e Implantación de Cultivos; Argentin

Cultivo de caña en Famaillá: Estudio de caso. Indicadores de la fertilidad física y de la vulnerabilidad del suelo: Evolución de la estabilidad estructural

Entre los meses de junio y julio de 2013 se inició un ensayo de larga duración en la EEA Famaillá (Tucumán) a fin de probar diferentes tecnologías de cultivo en caña de azúcar. El área experimental posee suelos argiudoles ácuicos, con un prolongado historial de monocultivo de caña con el manejo tradicional de la zona. La estructura del suelo tiene influencia en la mayoría de los factores de crecimiento de las plantas, siendo en determinados casos, un factor limitante en la producción. El laboreo continuo redujo el contenido de carbono lábil degradando la estructura superficial del suelo. Los ciclos de laboreo intenso-lluvia-cosecha generaron capas subsuperficiales compactadas que constituyen un impedimento para el movimiento de agua, nutrientes y el normal desarrollo de las raíces. La pérdida de estructura es una forma de degradación física del suelo, que frecuentemente está relacionada con el uso del mismo y las prácticas de manejo. En el área donde se desarrolla un ensayo de nuevas metodologías para la plantación y manejo de los cañaverales, se mantuvieron sitios abandonados a la vegetación nativa a fin de poder monitorear la evolución natural de la estabilidad estructural y del carbono del suelo. La estabilidad estructural de la capa superficial del horizonte A, la de mayor actividad biológica, experimentó una mejora notable luego de permanecer tres años bajo vegetación natural. El incremento en la relación carbono liviano/carbono total resultó coherente con el aporte de materia orgánica conjuntamente con la no disturbación del suelo durante este período. En la capa subyacente del horizonte A también se produjo un aumento en el contenido de carbono liviano y total, pero a diferencia de lo mencionado anteriormente, no tuvo el efecto esperado sobre la estabilidad de la estructura.Instituto de Ingeniería RuralFil: Tesouro, Mario Omar. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural. Laboratorio de Terramecánica e Implantación de Cultivos; ArgentinaFil: Roba, Marcos Andrés. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural. Laboratorio de Terramecánica e Implantación de Cultivos; ArgentinaFil: Romito, Angel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural. Laboratorio de Terramecánica e Implantación de Cultivos; ArgentinaFil: Fernandez Ullivarri, Enrique. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Donato, Lidia Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural. Laboratorio de Terramecánica e Implantación de Cultivos; ArgentinaFil: Neiman, Otto Erik. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural. Laboratorio de Terramecánica e Implantación de Cultivos; Argentin

Some topics in the theory of ultracold atomic gases

This thesis deals with a variety of topics that are relevant for the theory of ultracold atoms, with a focus on the many interaction regimes that can be obtained in these systems. The topics are presented in increasing order of complexity with regards to these interaction regimes. In the first chapter we are prompted by an experiment on a realization of an interacting Aubry-Andr´e Hamiltonian driven by a periodic modulation, where a localisation-delocalisation transition is observed. We will model an analogue non interacting system and show that it reproduces an equivalent phase diagram. Moreover we are able to provide a physical explanation for the critical amplitude and the critical frequency for the delocalisation transition. Next, we will consider a model of N atoms which are non interacting with the addition of a single light impurity that interacts with them. We will propose a simplified model based on the Born-Oppenheimer approximation and a polaron-like picture through which we are able to estimate the energy of the system and to address the question of theexistence of stable clusters bound by an impurity in the large N limit. In the rest of the thesis the pivot will be on the Andreev-Bashkin effect which describes the drag that each component of a mixture of two superfluids exerts on the other, as a result of their mutual interactions. We will first propose a microscopic theory based on linear response theory that describes the drag, and derive its implications on the nature of the excited states in a superfluid mixture. Then we will compute the effect of the drag on the spin speed of sound and the spin dipole mode which can in principle observed in experiments. Analytical results for the case of a weakly interacting mixture are presented as a benchmark for our methods. Finally we will focus on the Andreev-Bashkin effect in a Bose-Hubbard Hamiltonian in a one dimensional ring lattice. We will show that the effect is enhanced for attractive intraspecies interactions, more so close to the transition to paired superfluidity. A discussion on the correction brought by the drag in the low energy Luttinger theory for the model is also presented

Dataset for "Some Topics in the Theory of Ultracold Atomic Gases"

Data obtained from numerical simulations for a University of Southampton Doctoral Thesis &quot;Some Topics in the Theory of Ultracold Atomic Gases&quot;</span

Linear response study of collisionless spin drag

In this work we are concerned with the understanding of the collisionless drag or entrainment between two superfluids, also called Andreev-Bashkin effect, in terms of current response functions. The drag density is shown to be proportional to the cross transverse current-current response func- tion, playing the role of a normal component for the single species superfluid density. We can in this way link the existence of finite entrainment with the exhaustion of the energy-weighted sum rule in the spin channel. The formalism is then used to reproduce some known results for a weakly inter- acting Bose-Bose mixture. Finally we include the drag effect to determine the beyond mean-field correction on the speed of sound and on the spin dipole excitations for a homogeneous and trapped gas, respectively

Collisionless drag for a one-dimensional two-component Bose-Hubbard model

We theoretically investigate the elusive Andreev-Bashkin collisionless drag for a two-component one-dimensional Bose-Hubbard model on a ring. By means of tensor network algorithms, we calculate the superfluid stiffness matrix as a function of intra- and interspecies interactions and of the lattice filling. We then focus on the most promising region close to the so-called pair-superfluid phase, where we observe that the drag can become comparable with the total superfluid density. We elucidate the importance of the drag in determining the long-range behavior of the correlation functions and the spin speed of sound. In this way, we are able to provide an expression for the spin Luttinger parameter K-S in terms of drag and the spin susceptibility. Our results are promising in view of implementing the system by using ultracold Bose mixtures trapped in deep optical lattices, where the size of the sample is of the same order of the number of particles we simulate. Importantly, the mesoscopicity of the system, far from being detrimental, appears to favor a large drag, avoiding the Berezinskii-Kosterlitz-Thouless jump at the transition to the pair-superfluid phase which would reduce the region where a large drag can be observed