Physica Scripta is published by the IOP on behalf of the Royal Swedish Academy of Sciences for the Science Academies and the Physical Societies of the Nordic Countries.
Paper of the Week – Quantum explorations: from the waltz of the Pauli exclusion principle to the rock of the spontaneous collapse In spite of its tremendous success, quantum mechanics still generates discussions related to its possible limits. In this paper, researchers from Europe present experimental tests for two of the most interesting items in quantum theory: the Pauli exclusion principle (PEP), as a manifestation of the spin–statistics relation, and the measurement problem, within the spontaneous collapse of the wave function model.
Proceedings of Quantum Theory: Advances and Problems - QTAP, Linnaeus University, Sweden, June 10-13, 2013
The proceedings of this conference that was held in Sweden in June 2013, are now available as a Topical Issue of Physica Scripta. The articles in this issue will be free to read online until the end of March 2015.
ASOS-11 special issue now available
Selected papers from the Eleventh International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas (Mons, Belgium, 5-9 August 2013) are now available as a special section of Physica Scripta
Virtual issue: Emerging technologies and the future of humanity
This virtual issue of Physica Scripta grew out of the one-day meeting 'Emerging technologies and the future of humanity' that took place on March 17, 2014, at the Royal Swedish Academy of Sciences. The backdrop of the discussions at the meeting is the realization that technologies developed in the next few decades can have profound influence on the future of humanity.
Photonica'13 Topical Issue now available
Papers from the 4th International School and Conference on Photonics (PHOTONICA'13) that took place in the Serbian Academy of Sciences and Arts in Belgrade, Serbia, from 26–30 August 2013, are now available as a Topical Issue of Physica Scripta. A selection of the best work has been made free to read until the end of January 2015.
Crystallography and the Gregori Aminoff Prize
To mark the fact that 2014 has been designated the 'International Year of Crystallography', Physica Scripta will be publishing a virtual issue containing Invited Comments on the history of crystallography, as well as autobiographical articles from some of the current and previous winners of the Gregori Aminoff Prize. You can read the first papers published in this virtual issue here.
In the last 30 days
Kaj Sotala and Roman V Yampolskiy 2015 Phys. Scr. 90 018001
Many researchers have argued that humanity will create artificial general intelligence (AGI) within the next twenty to one hundred years. It has been suggested that AGI may inflict serious damage to human well-being on a global scale (‘catastrophic risk’). After summarizing the arguments for why AGI may pose such a risk, we review the fieldʼs proposed responses to AGI risk. We consider societal proposals, proposals for external constraints on AGI behaviors and proposals for creating AGIs that are safe due to their internal design.
D J Dunstan and D J Hodgson 2014 Phys. Scr. 89 068002
Many gardeners and horticulturalists seek non-chemical methods to control populations of snails. It has frequently been reported that snails that are marked and removed from a garden are later found in the garden again. This phenomenon is often cited as evidence for a homing instinct. We report a systematic study of the snail population in a small suburban garden, in which large numbers of snails were marked and removed over a period of about 6 months. While many returned, inferring a homing instinct from this evidence requires statistical modelling. Monte Carlo techniques demonstrate that movements of snails are better explained by drift under the influence of a homing instinct than by random diffusion. Maximum likelihood techniques infer the existence of two groups of snails in the garden: members of a larger population that show little affinity to the garden itself, and core members of a local garden population that regularly return to their home if removed. The data are strongly suggestive of a homing instinct, but also reveal that snail-throwing can work as a pest management strategy.
Seth D Baum 2014 Phys. Scr. 89 128004
Some emerging technologies promise to significantly improve the human condition, but come with a risk of failure so catastrophic that human civilization may not survive. This article discusses the great downside dilemma posed by the decision of whether or not to use these technologies. The dilemma is: use the technology, and risk the downside of catastrophic failure, or do not use the technology, and suffer through life without it. Historical precedents include the first nuclear weapon test and messaging to extraterrestrial intelligence. Contemporary examples include stratospheric geoengineering, a technology under development in response to global warming, and artificial general intelligence, a technology that could even take over the world. How the dilemma should be resolved depends on the details of each technology’s downside risk and on what the human condition would otherwise be. Meanwhile, other technologies do not pose this dilemma, including sustainable design technologies, nuclear fusion power, and space colonization. Decisions on all of these technologies should be made with the long-term interests of human civilization in mind. This paper is part of a series of papers based on presentations at the Emerging Technologies and the Future of Humanity event held at the Royal Swedish Academy of Sciences on 17 March 2014.
Andrei Khrennikov et al 2014 Phys. Scr. 2014 014019
Recently, the results of the first experimental test for entangled photons closing the detection loophole (also referred to as the fair sampling loophole) were published (Vienna, 2013). From the theoretical viewpoint the main distinguishing feature of this long-aspired to experiment was that the Eberhard inequality was used. Almost simultaneously another experiment closing this loophole was performed (Urbana-Champaign, 2013) and it was based on the Clauser–Horne inequality (for probabilities). The aim of this note is to analyze the mathematical and experimental equivalence of tests based on the Eberhard inequality and various forms of the Clauser–Horne inequality. The structure of the mathematical equivalence is nontrivial. In particular, it is necessary to distinguish between algebraic and statistical equivalence. Although the tests based on these inequalities are algebraically equivalent, they need not be equivalent statistically, i.e., theoretically the level of statistical significance can drop under transition from one test to another (at least for finite samples). Nevertheless, the data collected in the Vienna test implies not only a statistically significant violation of the Eberhard inequality, but also of the Clauser–Horne inequality (in the ratio-rate form): for both a violation .
Andrei Khrennikov and Andrew Schumann 2014 Phys. Scr. 2014 014020
We analyze the logical foundations of quantum mechanics (QM) by stressing non-objectivity of quantum observables, which is a consequence of the absence of logical atoms in QM. We argue that the matter of quantum non-objectivity is that, on the one hand, the formalism of QM constructed as a mathematical theory is self-consistent, but, on the other hand, quantum phenomena as results of experimenters’ performances are not self-consistent. This self-inconsistency is an effect of the language of QM differing greatly from the language of human performances. The former is the language of a mathematical theory that uses some Aristotelian and Russellian assumptions (e.g., the assumption that there are logical atoms). The latter language consists of performative propositions that are self-inconsistent only from the viewpoint of conventional mathematical theory, but they satisfy another logic that is non-Aristotelian. Hence, the representation of quantum reality in linguistic terms may be different: the difference between a mathematical theory and a logic of performative propositions. To solve quantum self-inconsistency, we apply the formalism of non-classical self-referent logics.
K S Novoselov and A H Castro Neto 2012 Phys. Scr. 2012 014006
Graphene is just one example of a large class of two-dimensional crystals. These crystals can either be extracted from layered three-dimensional materials or grown artificially by several different methods. Furthermore, they present physical properties that are unique because of the low dimensionality and their special crystal structure. They have potential for semiconducting behavior, magnetism, superconductivity, and even more complex many-body phenomena. Two-dimensional crystals can also be assembled in three-dimensional heterostructures that do not exist in nature and have tailored properties, opening an entirely new chapter in condensed matter research.
Garry Robinson and Ian Robinson 2013 Phys. Scr. 88 018101
In this paper the differential equations which govern the motion of a spherical projectile rotating about an arbitrary axis in the presence of an arbitrary ‘wind’ are developed. Three forces are assumed to act on the projectile: (i) gravity, (ii) a drag force proportional to the square of the projectile's velocity and in the opposite direction to this velocity and (iii) a lift or ‘Magnus’ force also assumed to be proportional to the square of the projectile's velocity and in a direction perpendicular to both this velocity and the angular velocity vector of the projectile. The problem has been coded in Matlab and some illustrative model trajectories are presented for ‘ball-games’, specifically golf and cricket, although the equations could equally well be applied to other ball-games such as tennis, soccer or baseball.
Spin about an arbitrary axis allows for the treatment of situations where, for example, the spin has a component about the direction of travel. In the case of a cricket ball the subtle behaviour of so-called ‘drift’, particularly ‘late drift’, and also ‘dip’, which may be produced by a slow bowler's off or leg-spin, are investigated. It is found that the trajectories obtained are broadly in accord with those observed in practice. We envisage that this paper may be useful in two ways: (i) for its inherent scientific value as, to the best of our knowledge, the fundamental equations derived here have not appeared in the literature and (ii) in cultivating student interest in the numerical solution of differential equations, since so many of them actively participate in ball-games, and they will be able to compare their own practical experience with the overall trends indicated by the numerical results.
As the paper presents equations which can be further extended, it may be of interest to research workers. However, since only the most basic principles of fundamental mechanics are employed, it should be well within the grasp of first year university students in physics and engineering and, with the guidance of teachers, good final year secondary school students. The trajectory results included may be useful to sporting personnel with no formal training in physics.
Sukang Bae et al 2012 Phys. Scr. 2012 014024
Since the first isolation of graphene in 2004 by mechanical exfoliation from graphite, many people have tried to synthesize large-scale graphene using various chemical methods. In particular, there has been a great number of advances in the synthesis of graphene using chemical vapor deposition (CVD) on metal substrates such as Ni and Cu. Recently, a method to synthesize ultra-large-scale (~30 inch) graphene films using roll-to-roll transfer and chemical doping processes was developed that shows excellent electrical and physical properties suitable for practical applications on a large scale. Considering the outstanding scalability/processibility of roll-to-roll and CVD methods as well as the extraordinary flexibility/conductivity of graphene films, we expect that transparent graphene electrodes can replace indium tin oxide in the near future.
Yigong Shi 2014 Phys. Scr. 89 068004
As a Chinese born and raised in central China, I came to the United States for graduate education in 1990. Eighteen years later, I resigned my tenured faculty position at Princeton University and returned to my alma mater Tsinghua University. In this review, I share my experiences and reflections as a graduate student, a postdoctoral fellow, and an independent scientist in both Princeton and Beijing. Much focus is given to my research effort in the field of programmed cell death (also known as apoptosis). Systematic structural biology, which combines x-ray crystallography with other biochemical and biophysical methods, has led to comprehensive understanding of the underlying molecular mechanisms that govern the initiation, execution, and regulation of apoptosis.
GianCarlo Ghirardi and Raffaele Romano 2014 Phys. Scr. 2014 014028
Recently, it has been argued that quantum mechanics is a complete theory, and that different quantum states do necessarily correspond to different elements of reality, under the assumptions that quantum mechanics is correct and that measurement settings can be freely chosen. In this work, we prove that this result is a consequence of an unnecessarily strong mathematical expression of the free choice assumption, which embodies more conditions than explicitly stated. The issues of the completeness of quantum mechanics, and of the interpretation of the state vector, are by no means resolved. Taking this perspective, we describe how the recently introduced class of crypto-nonlocal hidden variables theories can be used to characterize the maximal possible departure from quantum mechanics, when the system consists of a pair of qubits.