Entropy? Exercices de Style

Since its inception, the concept of entropy has been known under a variety of guises and been used in an increasing number of contexts, achieving an almost rock star-like status in both the sciences and popular culture. The three most prominent “styles” which entropy has been (re)told in and which have determined its popularity are the thermodynamic, statistical and information-theoretic one, owing much to the work of Clausius, Boltzmann and Gibbs, and Shannon, respectively. In the relentless hunt for the core of the concept that spurred this development, connections with irreversibility and emergence of time, nature of probability and information emerged adding to its elusiveness as much as stimulating its proliferation and cross-contextual adoption. In this historical review, we retrace, through primary and secondary sources, the three main perspectives from which entropy has been regarded, emphasising the motivations behind each new version, their ramifications and the bridges that have been constructed to justify them. From this analysis of the foundations a number of characteristic traits of the concept emerge that underline its exceptionality as an engine of conceptual progress

Yoichiro Nambu and the Concept of Apparent Vacuum: A Stepping Stone to Spontaneous Symmetry Breaking

The processes of discovery and concept formation are as mysterious as they are intriguing. In this article, they give a sketch of Yoichiro Nambu’s long path toward the concept of spontaneous symmetry breaking focusing on the pivotal role played by his notion of “apparent vacuum”. This is instrumental to draw the original analogical correspondence between the vacuum of quantum field theory and solid matter, which, transforming over time in its use and purpose, enables Nambu to arrive at the concept of spontaneous symmetry breaking. From this historical episode they draw a methodological lesson and emphasise the broad cultural influences that conditioned the conceptual development

Cubesat mission with technological demonstrator payload for high data rate downlink and health monitoring

The HyperCube payload will be composed by two different technological experiment, an high data-rate C band antenna, and a demonstrator for a remote structural health monitoring system. The first one has been thought with the aim to give Cubesats the capability to download an high quantity of data; it could be useful either if the data requiring the high data-rate downlink is on-board generated or simply retransmitted. The applications for which this payload could be used are several; an example for the first category of application is to download the data generated by another payload; the high data-rate capability could be necessary due to the narrow visibility window with the ground station, affected also by the absence of an active AOCS subsystem, which makes difficult the alignment of the on board antenna with the ground one. But the C band antenna could also be used to act as a “space–repeater”, downloading up–linked information. The second payload is related to the need to take under strictly control the health of the structures (not only the ones strictly belonging to primary structures, but also that of any subsystem component). In order to do that, smart materials are integrated into the structural component that need to be monitored; in particular, piezoelectric patches are used as sensors. As the structure is stressed, and the integrated piezoelectric sensors are subjected to mechanical deformation, they produce an electric signal; acquiring and properly studying the produced signal it is possible to monitor the mechanical condition of the structures. The health monitoring system is completed by a MicroController Unit which acquires, samples and stores the signal produced, and a transmitting system, which could be the C band antenna, or the TT&C antenna which each satellite needs

Far from the Particle Crowd: Shugyosha Nambu and Michizane Wheeler

In the late 1940s many physicists embrace the surging particle physics regarding it as potentially resolutive of the crisis of nuclear physics. Against this backdrop, two thinkers of peculiar taste choose otherwise. Here we trace the roots and consequences of their decisions

Looking Stereoscopically at Goethe vs. Newton: Heisenberg and Pauli on the Future of Physics

Goethe’s polemics against Newtonian optics is not rarely men- tioned as a singular instance of incompetent stubbornness, or quickly dis- posed of as an embarrassing incident, not worthy of Goethe’s stature. None- theless, Goethe’s presence in the mind of 20th-century physicists is not a neg- ligible chapter, not only due to the pre-eminence of his literary work but to a suffused Naturphilosophie as well. Even more significantly, physicists of the calibre of Heisenberg and Pauli, while openly recognizing the ‘mistakes’ of the Goethean polemics in optics, tried to extract from that episode important lessons and expectations about the future of science

Optical variability of the strong-lined and X-ray bright source 1WGA J0447.9-0322

We present the historic light curve of 1WGA J0447.9-0322, spanning the time interval from 1962 to 1991, built using the Asiago archive plates. The source shows small fluctuations of about 0.3 mag around B=16 until 1986 and a fast dimming of its average level by about 0.5 mag after that date, again with small short term variations. The variability pattern is within the values shown by other QSOs with long term monitoring, notwithstanding its high X-ray/optical ratio. We present also its overall SED using literature data and recent UV-optical SWIFT observations.Comment: 17 pages, 4 figures, accepted by The Astronomical Journal. Table 2 available upon reques

Tales from Dubna’s Oakwood: Bogoliubov, Pontecorvo, and the JINR Seminars

Not much has been said about the scientific milieu in which Bru- no Pontecorvo worked after his emigration to the USSR (1950): the Joint Institute for Nuclear Research (JINR) in Dubna. In this paper, we begin to fill this gap by focusing on some of the distinguished scientists he interacted with, besides direct collaborations, paying particular attention to Nikolai N. Bogoliubov around 1957