Hemeroteca de la sección ‘Ciencia y tecnología’

Computational Chemistry as Voodoo Quantum Mechanics : Models, Parameterization, and Software

Por • 8 dic, 2018 • Category: Ciencia y tecnología

Computational chemistry grew in a new era of “desktop modeling”, which coincided with a growing demand for modeling software, especially from the pharmaceutical industry. Parameterization of models in computational chemistry is an arduous enterprise, and we argue that this activity leads, in this specific context, to tensions among scientists regarding the lack of epistemic transparency of parameterized methods and the software implementing them. To explicit these tensions, we rely on a corpus which is suited for revealing them, namely the Computational Chemistry mailing List (CCL), a professional scientific discussion forum. We relate one flame war from this corpus in order to assess in detail the relationships between modeling methods, parameterization, software and the various forms of their enclosure or disclosure. Our claim is that parameterization issues are a source of epistemic opacity and that this opacity is entangled in methods and software alike. Models and software must be addressed together to understand the epistemological tensions at stake.

Real numbers as infinite decimals — theory and computation

Por • 29 nov, 2018 • Category: Ciencia y tecnología

In the 16th century, Simon Stevin initiated a modern approach to decimal representation of measuring numbers, marking a transition from the discrete arithmetic practised by the Greeks to the arithmetic of the continuum taken for granted today. However, how to perform arithmetic directly on infinite decimals remains a long-standing problem, which has seen the popular degeometrisation of real numbers since the first constructions were published in around 1872. Our article is devoted to solving this historical problem. An issue that Hardy called “a fatal defect” is also settled.

Applications of Deep Learning to Nuclear Fusion Research

Por • 10 nov, 2018 • Category: Ciencia y tecnología

Diogo R. Ferreira on behalf of JET Contributors Abstract: Nuclear fusion is the process that powers the sun, and it is one of the best hopes to achieve a virtually unlimited energy source for the future of humanity. However, reproducing sustainable nuclear fusion reactions here on Earth is a tremendous scientific and technical challenge. Special […]

Search for resonances in the mass spectrum of muon pairs produced in association with b quark jets in proton-proton collisions at s√= 8 and 13 TeV

Por • 3 nov, 2018 • Category: Ciencia y tecnología

A search for resonances in the mass range 12-70 GeV produced in association with a b quark jet and a second jet, and decaying to a muon pair, is reported. The analysis is based on data from proton-proton collisions at center-of-mass energies of 8 and 13 TeV, collected with the CMS detector at the LHC and corresponding to integrated luminosities of 19.7 and 35.9 fb−1, respectively. The search is carried out in two mutually exclusive event categories. Events in the first category are required to have a b quark jet in the central region (|η|≤ 2.4) and at least one jet in the forward region (|η|>2.4). Events in the second category are required to have two jets in the central region, at least one of which is identified as a b quark jet, no jets in the forward region, and low missing transverse momentum.

Theoretical Equivalence in Physics

Por • 30 oct, 2018 • Category: Ciencia y tecnología

I review the philosophical literature on the question of when two physical theories are equivalent. This includes a discussion of empirical equivalence, which is often taken to be necessary, and sometimes taken to be sufficient, for theoretical equivalence; and “interpretational” equivalence, which is the idea that two theories are equivalent just in case they have the same interpretation. It also includes a discussion of several formal notions of equivalence that have been considered in the recent philosophical literature, including (generalized) definitional equivalence and categorical equivalence. The article concludes with a brief discussion of the relationship between equivalence and duality.

The Paraconsistent Logic of Quantum Superpositions

Por • 13 oct, 2018 • Category: Ciencia y tecnología

Physical superpositions exist both in classical and in quantum physics. However, what is exactly meant by ‘superposition’ in each case is extremely different. In this paper we discuss some of the multiple interpretations which exist in the literature regarding superpositions in quantum mechanics. We argue that all these interpretations have something in common: they all attempt to avoid ‘contradiction’. We argue in this paper, in favor of the importance of developing a new interpretation of superpositions which takes into account contradiction, as a key element of the formal structure of the theory, “right from the start”. In order to show the feasibility of our interpretational project we present an outline of a paraconsistent approach to quantum superpositions which attempts to account for the contradictory properties present in general within quantum superpositions. This approach must not be understood as a closed formal and conceptual scheme but rather as a first step towards a different type of understanding regarding quantum superpositions.

Lenguage and Ontological Emergence

Por • 2 oct, 2018 • Category: Ciencia y tecnología

Providing empirically supportable instances of ontological emergence is notoriously difficult. Typically, the literature has focused on two possible sources. The first is the mind and consciousness; the second is within physics, and more specifically certain quantum effects. In this paper, I wish to suggest that the literature has overlooked a further possible instance of emergence, taken from the special science of linguistics. In particular, I will focus on the property of truth-evaluability, taken to be a property of sentences as created by the language faculty within human minds (or brains).

Intransitive Machines

Por • 24 sep, 2018 • Category: Ciencia y tecnología

The intransitive cycle of superiority is characterized by such binary relations between A, B, and C that A is superior to B, B is superior to C, and C is superior to A (i.e., A>B>C>A – in contrast with transitive relations A>B>C). The first part of the article presents a brief review of studies of intransitive cycles in various disciplines (mathematics, biology, sociology, logical games, decision theory, etc.), and their reflections in educational materials. The second part of the article introduces the issue of intransitivity in elementary physics. We present principles of building mechanical intransitive devices in correspondence with the structure of the Condorcet paradox, and describe five intransitive devices: intransitive gears; levers; pulleys, wheels, and axles; wedges; inclined planes.

Weak Optimality, and the Meaning of Sharing

Por • 19 sep, 2018 • Category: Ciencia y tecnología

In this paper we investigate laziness and optimal evaluation strategies for functional programming languages. We consider the weak λ-calculus as a basis of functional programming languages, and we adapt to this setting the concepts of optimal reductions that were defined for the full λ-calculus. We prove that the usual implementation of call-by-need using sharing is optimal, that is, normalizing any λ-term with call-by-need requires exactly the same number of reduction steps as the shortest reduction sequence in the weak λ-calculus without sharing. Furthermore, we prove that optimal reduction sequences without sharing are not computable. Hence sharing is the only computable means to reach weak optimality.

A Century of Science: Globalization of Scientific Collaborations, Citations, and Innovations

Por • 5 sep, 2018 • Category: Ciencia y tecnología

Progress in science has advanced the development of human society across history, with dramatic revolutions shaped by information theory, genetic cloning, and artificial intelligence, among the many scientific achievements produced in the 20th century. However, the way that science advances itself is much less well-understood. In this work, we study the evolution of scientific development over the past century by presenting an anatomy of 89 million digitalized papers published between 1900 and 2015. We find that science has benefited from the shift from individual work to collaborative effort, with over 90% of the world-leading innovations generated by collaborations in this century, nearly four times higher than they were in the 1900s. We discover that rather than the frequent myopic- and self-referencing that was common in the early 20th century, modern scientists instead tend to look for literature further back and farther around. Finally, we also observe the globalization of scientific development from 1900 to 2015, including 25-fold and 7-fold increases in international collaborations and citations, respectively, as well as a dramatic decline in the dominant accumulation of citations by the US, the UK, and Germany, from 95% to 50% over the same period.