Relativistic fluid dynamics and its extensions as an effective field theory

We examine hydrodynamics from the perspective of an effective field theory. The microscopic scale in this case is the thermalization scale, and the macroscopic scale is the gradient, with thermal fluctuations playing the role of $\hbar$. We argue that this method can be applied both, to consistently include thermal fluctuations in the theory, and to extend hydrodynamics to systems whose microscopic structure is non-trivial. For the latter, we discuss the case of spin polarization and gauge theories.Comment: Proceedings for the "Epiphany in Krakow 2019" conference, submitted to Acta Fisica Polonic

Thrifty swimming with shear-thinning

Microscale propulsion is integral to numerous biomedical systems, for example biofilm formation and human reproduction, where the surrounding fluids comprise suspensions of polymers. These polymers endow the fluid with non-Newtonian rheological properties, such as shear-thinning and viscoelasticity. Thus, the complex dynamics of non-Newtonian fluids presents numerous modelling challenges, strongly motivating experimental study. Here, we demonstrate that failing to account for "out-of-plane" effects when analysing experimental data of undulatory swimming through a shear-thinning fluid results in a significant overestimate of fluid viscosity around the model swimmer C. elegans. This miscalculation of viscosity corresponds with an overestimate of the power the swimmer expends, a key biophysical quantity important for understanding the internal mechanics of the swimmer. As experimental flow tracking techniques improve, accurate experimental estimates of power consumption using this technique will arise in similar undulatory systems, such as the planar beating of human sperm through cervical mucus, will be required to probe the interaction between internal power generation, fluid rheology, and the resulting waveform

Ghosts of Futures Past: Time in Francis Alÿs’ Rehearsal and Tania Bruguera’s Untitled (Place, Year) series

This paper addresses the construction of time in Francis Alÿs' Rehearsal (1999-2004) and Tania Bruguera's Untitled (Place, Year) (2000-present) series. These suites posit a model of temporality that questions two foundational premises of the modernist understanding of time, the futuristic regime of historicity, and the categorical differentiation between past, present and future. I argue that their works posit an uncanny temporality where the coordinates of the now are always mapped out in relationship to what was and what is to be

Radical (Dis)Identification: Santiago Sierra's Double(D) Spectator

This paper explores how Santiago Sierra’s artistic practice undoes the stable identification of the viewer by placing him or her in the double position of master and slave, employer and employee, at the same time. I posit that Sierra’s works double the spectator’s position of power and make visible the existence in the present of past hierarchical constructions ostensibly surmounted. Contrary to Claire Bishop’s interpretation of Sierra’s work —which rests on a 'mutual moment of non-identification' between hired performers and audience members—, I argue that in his practice there is also the possibility for the audience to identify with his hired performers as well as with Sierra as employer. I investigate how Sierra’s works force us to realise how, as contemporary economic subjects, we operate as hiring individuals —of others’ bodies—, and at the same time are individuals —bodies— for hire

Los modelos económicos en la Constitución Política de 1991: análisis jurisprudencial en estudio de caso

Artículo de investigaciónSe hace un estudio con el fin de identificar los modelos y tipologías Constitucionales para lograr identificar cuál de ellos resulta aplicable a la Constitución Política de 1991. Posteriormente se hace un estudio de caso aplicando los conceptos antes descritos, con el fin de identificar si en los fallos de la Corte Constitucional, son con tendencia liberal o social, o integradora entre los dos sistemas.PregradoAbogad

Francis Alÿs, Santiago Sierra y Tania Bruguera: Exilios voluntarios, lugares en debate y desplazamientos orales

Francis Alÿs, Santiago Sierra y Tania Bruguera se caracterizan, entre otros factores, por una extrema movilidad geográfica. Estos tres artistas han logrado articular un lenguaje artístico que, aunque derivado de vivencias personales, les ha permitido intervenir en múltiples y disímiles regiones geográficas, desde Corea del Norte hasta La Habana, de Hong Kong a Ciudad de Mexico, desde Kassel a Nueva York. Estas prácticas itinerantes, alimentadas por el sistema artístico transnacional y por deseos e intereses artísticos individuales, articulan una posición desde la cual se entiende el trasladarse de un lugar a otro como una oportunidad que posibilita la generación de un encuentro crítico con un determinado contexto. En vez de ser entendido como una condena, una violación o un destierro, el desplazamiento se articula como una herramienta para la dislocación cultural que fomenta la emergencia de diferentes puntos de vista alrededor de una situación, contexto o realidad específica. En su acepción más general, este texto explora como el desplazamiento para estos tres artistas implica la revaluación de ciertas perspectivas consolidadas y el cues tionamiento de conceptos sedimentados

Locating Work in Santiago Sierra’s Artistic Practice

This paper closely analyses Santiago Sierra’s understanding of the relationship between work and freedom in contemporary society. By focusing on a series of works where the artist hired someone to perform a specific activity (often involving labour or a contractual working agreement), this essay explores the location(s) of work in Sierra’s artistic practice. In these pieces, the artist delegated or subcontracted a part of the artistic event, either to remain still, hidden inside a box or in a humid, hot compartment in a ship under the sun. At the same time, he remained as a ‘director’ or ‘coordinator’, dictating the conditions of possibility for these actions, the ensuing documentation and its posterior commercialisation. This implies that we can find, at least, two moments where work can be located in Santiago Sierra’s practice. On one level, work (manual labour associated with a paid wage in a determinate economic context) happens at the moment of the actual performance by the hired employees. At the same time, work can also be located at the moment when the artist records and produces an artwork (as intellectual labour). In this sense, the artist uses the work of others in order to produce his own, blatantly turning the workers from a means to an end. This duality suggests that work can be clearly antithetical to freedom for some in a system of advanced, corporate, capitalism while deceitfully emancipatory for a select few. By carefully examining the complex networks of work displacement in Santiago Sierra’s practice, it is my intention to lay bare the premises that support his vision of work as a site for constant struggle between freedom and subjugation

Precision stop control for motors

An improved stop control system and method are provided for a motor having a drive mechanism in which the motor is coupled to a motor controller that controls the speed and position of the drive mechanism using a first signal indicative of a commanded position of the drive mechanism, a second signal indicative of the actual speed of the drive mechanism and a third signal indicative of the actual position of the drive mechanism. The improved system/method uses a first circuit that receives the first and third signal and generates an error signal indicative of a difference therebetween. A second circuit receives the error signal and compares same with a threshold position error. The result of this comparison is used to selectively supply the second signal (i.e., speed) to the motor controller at least whenever the error signal is less than the threshold position error so that the motor controller can use the second signal in conjunction with the third signal to stop the motor