Error Analysis of Modified Langevin Dynamics

We consider Langevin dynamics associated with a modified kinetic energy vanishing for small momenta. This allows us to freeze slow particles, and hence avoid the re-computation of inter-particle forces, which leads to computational gains. On the other hand, the statistical error may increase since there are a priori more correlations in time. The aim of this work is first to prove the ergodicity of the modified Langevin dynamics (which fails to be hypoelliptic), and next to analyze how the asymptotic variance on ergodic averages depends on the parameters of the modified kinetic energy. Numerical results illustrate the approach, both for low-dimensional systems where we resort to a Galerkin approximation of the generator, and for more realistic systems using Monte Carlo simulations

Risk-hedging using options for an upgrading investment in a data network

In this paper, we illustrate how a mobile data network operator can plan an upgrading investment to anticipate explosions of the demand, taking into account the expected generated profit and the customers satisfaction. The former parameter grows with the demand, whereas the latter sinks if the demand is too high as throughput may collapse. As the equipment price decreases with time, it may be interesting to wait rather than to invest at once. We then propose a real option strategy to hedge against the risk that the investment has to take place earlier than expected. At last, we price this option with a backward dynamic programming approach, using recent improvements based on least-squares estimations.

Interactive Chemical Reactivity Exploration

Elucidating chemical reactivity in complex molecular assemblies of a few hundred atoms is, despite the remarkable progress in quantum chemistry, still a major challenge. Black-box search methods to find intermediates and transition-state structures might fail in such situations because of the high-dimensionality of the potential energy surface. Here, we propose the concept of interactive chemical reactivity exploration to effectively introduce the chemist's intuition into the search process. We employ a haptic pointer device with force-feedback to allow the operator the direct manipulation of structures in three dimensions along with simultaneous perception of the quantum mechanical response upon structure modification as forces. We elaborate on the details of how such an interactive exploration should proceed and which technical difficulties need to be overcome. All reactivity-exploration concepts developed for this purpose have been implemented in the Samson programming environment.Comment: 36 pages, 14 figure

An Unexpected Perspective: from Ancient Egypt to Adventure

[ES] En 1979 Atari lanzó el videojuego Adventure, considerado pionero en los juegos de aventuras rpg (rol-player game), inaugurando un sistema de representación propio que recibió el nombre de perspectiva tres cuartos, que sería empleado posteriormente por todas las grandes compañías de videojuegos. Esta perspectiva tres cuartos se trataba en realidad de un caso particular de perspectiva isométrica frontal de ángulos ZY’=Z’Y que en dibujo arquitectónico se ha venido denominando ‘perspectiva egipcia’ o perspectiva Hejduk. Este acontecimiento tuvo gran repercusión en el comienzo de la representación del espacio virtual mostrando una concepción determinada del mundo, demostrando que la producción del espacio en los videojuegos tiene desde su origen un vínculo interdisciplinar con el espacio materializado de la arquitectura.[EN] In 1979, Atari launched the videogame Adventure, considered a pioneer in RPGs (role-playing games). Atari thus launched its own system of representation that was named three-quarter perspective, and that would subsequently be used by all large videogame companies. Three-quarter perspective was, in reality, what was  termed ‘Egyptian perspective’ 1 orHejduk perspective, which consists of placing plan and elevation in a single drawing and simultaneously. That event had a great impact on the representation of virtual space showing a particular conception of the world, demonstrating that the production of space in videogames has, since its inception, had an interdisciplinary link with the materialised space of architecture.Grupo de Investigación Hypermedia, Warren Robinett, Rice University.Redon, AN. (2021). Una perspectiva inesperada. De la perspectiva en el antiguo Egipto al videojuego Adventure. EGA Expresión Gráfica Arquitectónica. 26(41):206-217. https://doi.org/10.4995/ega.2021.14296OJS2062172641ARES, Ignacio. La organización del espacio en perspectiva egipcia. Revista de Arqueología nº191p 30-37 (March 1997).BAROLSKY, Paul. The playful artifice of douanier Rousseau's persona. Source: Notes in the History of Art 13, no. 1 21-25 (Fall 1993). https://doi.org/10.1086/sou.13.1.23203036BARTON, Matt. Dungeons and Desktops: The History of Computer Role-Playing Games. A K Peters/CRC Press (2008). https://doi.org/10.1201/b10638DELEUZE, Gilles. El fin del espacio egipcio y el molde geométrico-cristalino. Pintura. El concepto de diagrama. Ed Cactus. Buenos Aires (2008)DONOVAN, Tristan. Replay: la historia de los videojuegos. Ed. Héroes de papel. (2010) 2018 6.Gentil Baldrich, J. María. Sobre la supuesta perspectiva antigua (y algunas consecuencias modernas). Ed. Universidad de Sevilla. Sevilla. (2012)GOMBRICH, E.H. La historia del Arte. Ed. Phaidon. London (1950) 1999HEJDUK, John. Mask of Medusa. Works 1947-1983. Rizzoli International Publications. (1989) 9.Heydenreich, L H. Leonardo da Vinci. Enciclopedia Universale dell'arte. Vol VIII Istituto per la collaborazione culturale, Pages 562-590 Venezia - Roma (1958)IZQUIERDO ASENSI, Fernando. Geometría descriptiva superior y aplicada, Madrid, s.n., 2000, 24ª ed.KENT, Steven. L. The Ultimate history of videogames. Penguin Random House Group Ed. España. (2001) 2016LUQUE, Andrés. Picasso, documentos sobre la ascendencia del arte egipcio en el personaje central de las señoritas de Aviñón. Laboratorio de Arte. Núm.17, Universidad de Sevilla, Pages 523-534. Sevilla. (2005)PARKINSON, Richard. Painted Tomb Chapel of Nebamun. Ed. Brisith Museum Press. London (2008)PERRON, Bernard. WOLF, Marl J.P. The Video Game Theory Reader. Routledge. London (2003)PERROT, Georges. CHIPIEZ, Charles Histoire de l'art dans l'antiquité: Egypte, Assyrie, Perse, Asie Mineure, Grèce, Étrurie, Rome (Band 1): L'Egypte. Paris. (1903) (accessed on September 15, 2018 at https://digi.ub.uni-heidelberg.de/diglit/perrot1882bd1)RABASA DIAZ, Enrique. Proyección y representación: conceptos intuitivos. Colección Cuadernos del Instituto Juan de Herrera, Madrid, 2000.RAE. Direccionario de la Real Academia de la Lengua Española. Espasa Ed. (2017)REMIE, C. O. Chess and Courtly Culture in Medieval Castile: The Libro de ajedrez of Alfonso X, el Sabio, περ. Speculum, A Journal of Medieval Studies, Vol 2. Page 82 (2007) 19. https://doi.org/10.1017/S0038713400009404ROBINETT, Warren. Interview for Stanford University. https://web.stanford. edu/dept/HPS/TimLenoir/ MilitaryEntertainment/Atari/Warren%20Robinett%20 Interview.html (1997) (accessed on September 13, 2018)ROBINETT, Warren. GDC Talk on Adventure (2015) (accessed on September 14, 2018) 21.Robinett, Warren. Personal interview via email on September 14, 2018RUBIN, William. La génesis de Les demoiselles d'Avignon; at Les demoiselles d'Avignon. pages 374- 375. Paris (1987) Barcelona (1988)SÁNCHEZ GALLEGO, Juan Antonio. Geometría descriptiva. Sistemas de proyección cilíndrica, Barcelona, UPC, 1998

Ciència, veritat i epistemologia antropològica. Una síntesi històrica de les crítiques a la universalitat de la ciència

Aquest treball pretén fer una síntesi de les aportacions epistemològiques fonamentals que al llarg del segle XX han criticat la vella concepció positivista del coneixement científic. Aquesta concepció no només perdura encara hui dia, sinó que és la concepció dominant internacionalment al món de les ciències socials. Sembla llavors indispensable traçar una crítica en profunditat d'aquesta qüestió. El present treball no pretén ésser aquesta crítica, necessàriament complexa, sinó que intenta aportar-ne les línies mestres de manera sintètica.This work aims to make a synthesis of the main epistemological contributions that have criticized, along the 20th century, the old positivist conception of scientific knowledge. This conception is not only still alive nowadays, but is the dominant conception in the international world of social sciences. It seems then necessary to sketch a deep critic concerning this question. This works doesn't pretend to be this critic, which would be necessarily complex, but tries to give the main lines towards this direction in a synthetic way

Nanotechnologie : conception à l'échelle atomique par Stéphane Redon. Dynamique moléculaire interactive, entretien avec Serge Crouzy, propos recueillis par Dominique Chouchan.

National audienceL'exploration et la manipulation de l'infiniment petit passeront sans doute par la conception assistée par ordinateur : le prototypage virtuel d'objets nanoscopiques concerne un grand nombre d'applications industrielles, pharmacologiques..

Allison Brown, The Return of Lucretius to Renaissance Florence, Cambridge, Harvard University Press, 2010

Sin resume

Places of order, order in place.Police forces’ spatialities and practices

From policing to policed territories Today, countless news reports and reality TV programs stage the work of the police forces, creating the illusion that they are following them in action. However, these broadcasts provide almost no information on the spaces where the interventions take place, or on the relationship between those spaces and the agents responsible for keeping public order. In other words, the spectators are made to watch “on-the-ground” action without being provided with an ..