Is the relativity principle consistent with classical electrodynamics? Towards a logico-empiricist reconstruction of a physical theory

The transformation rules for the basic electrodynamical quantities are routinely derived from the hypothesis that the relativity principle (RP) applies for Maxwell's electrodynamics. These derivations leave open several questions: (1) Is the RP a true law of nature for electrodynamical phenomena? (2) Are, at least, the transformation rules of the fundamental electrodynamical quantities, derived from the RP, true? (3) Is the RP consistent with the laws of electrodynamics in one single inertial frame of reference? (4) Are, at least, the derived transformation rules consistent with the laws of electrodynamics in one single frame of reference? (1) and (2) are empirical questions; we will investigate problems (3) and (4). First we will develop a formalism of the RP. In the second part, we will deal with the operational definitions of the fundamental quantities. In the third part of the paper we will show that the proper transformation rules are indeed identical with the ones obtained by presuming the covariance, and that the covariance is indeed satisfied. Problem (3) raises conceptual problems to which there seems no satisfactory solution in electrodynamics; thus, contrary to the widespread views, the question we asked in the title has no obvious answer.Comment: 39 pages, 3 figures, LaTeX; more concise notations, elucidatory remarks and examples adde

The starfish experiment: a Lagrangian approach

The present paper analyses the free surface deformation of a liquid metal drop under the influence of an alternating magnetic field. The analysis is restricted to the first axi- symmetric mode oscillation. In the low frequency case, the electromagnetic forces are of gradient type and purely oscillatory. Without any viscous damping, it is then possible to build a Lagrangian function, which involves the kinetic energy, the gravitational energy, the surface energy and the electromagnetic energy. The time evolution of the pool height is easily obtained from the Lagrange equation. It is shown that the pool height behaves like a non-linear forced oscillator

On the relativistic mass function and averaging in cosmology

The general relativistic description of cosmological structure formation is an important challenge from both the theoretical and the numerical point of views. In this paper we present a brief prescription for a general relativistic treatment of structure formation and a resulting mass function on galaxy cluster scales in a highly generic scenario. To obtain this we use an exact scalar averaging scheme together with the relativistic generalization of Zel'dovich's approximation (RZA) that serves as a closure condition for the averaged equations.Comment: Contribution to the proceedings of MG1

Relativistic structure formation models and gravitoelectromagnetism

In the framework of Lagrangian perturbation theory in general relativity we discuss the possibility to split the Einstein equations, written in terms of spatial Cartan coframes within a 3+1 foliation of spacetime, into gravitoelectric and gravitomagnetic parts. While the former reproduces the full hierarchy of the Newtonian perturbation solutions, the latter contains non-Newtonian aspects like gravitational waves. This split can be understood and made unique through the Hodge decomposition of Cartan coframe fields.Comment: 6 pages; contribution to the proceedings of MG14, Parallel Session DE

Experiential knowledge of disability, impairment and illness : the reproductive decisions of families genetically at risk

As the capacities of Reproductive Genetic Technologies expand, would-be parents face an increasing number of reproductive decisions regarding testing and screening for different conditions. Several studies have acknowledged the role that ‘experiential knowledge of disability’ plays in arriving at decisions around the use of these technologies; however, there is a lack of clarity within this literature as to what constitutes ‘experiential knowledge of disability’ and an over-reliance on medical diagnoses as a shorthand to describe different types of experience. Drawing on both social model of disability theory and the literature on chronic illness, this article presents an analysis of data from an in-depth qualitative interview study with 64 people with an inheritable condition in their family, Spinal Muscular Atrophy, and reports their views around reproduction and Reproductive Genetic Technologies. An experiential typology is presented which demonstrates the way in which experiences of ‘disability’, ‘embodied experiences of impairment’ or ‘embodied experiences of illness, death and bereavement’ are strategically privileged in accounts of reproductive decisions, in order to validate reproductive decisions taken, and, specifically, justify use (or non-use) of Reproductive Genetic Technologies. By highlighting the experiential categories within which participants embedded their reproductive decisions, this article draws attention to the porous and collapsible nature of diagnostic categories in the context of reproductive decision-making and genetic risk, and suggests new ways of researching ‘experiential knowledge of disability’ within these contexts which are able to account for the various contours of the embodied lived reality of life with ‘disability’

Operational understanding of the covariance of classical electrodynamics

It is common in the literature on classical electrodynamics and relativity theory that the transformation rules for the basic electrodynamical quantities are derived from the pre-assumption that the equations of electrodynamics are covariant against these---unknown---transformation rules. There are several problems to be raised concerning these derivations. This is, however, not our main concern in this paper. Even if these derivations were completely correct, they leave open the following fundamental question: Are the so-obtained transformation rules indeed identical with the true transformation rules of the fundamental electrodynamical quantities? In other words, is it indeed the case that the values calculated from the quantities in one inertial frame by means of the transformation rules we derived are equal to the values of the same quantities obtained by the same operations with the same measuring equipments when they are co-moving with the other inertial frame? This is of course an empirical question. In this paper, we will investigate the problem in a purely theoretical framework by applying what J. S. Bell calls “Lorentzian pedagogy”---according to which the laws of physics in any one reference frame account for all physical phenomena. We will show that the transformation rules of the electrodynamical quantities are indeed identical with the ones obtained by presuming the covariance of the equations of electrodynamics, and that the covariance is indeed satisfied. Beforehand, however, we need to clarify the operational definitions of the fundamental electrodynamical quantities. As we will see, these semantic issues are not as trivial as one might think

'Men give in to chips and beer too easily': How working-class men make sense of gender differences in health

This article, based on qualitative research with working-class men, explores men's perceptions and experiences regarding gender differences in health. It demonstrates how men put forward a range of behavioural/cultural, materialist/structural and psychosocial factors, which were believed to differently impact men's health compared to women. A common theme underpinning their explanations was the ways in which men and women were located within two distinct gender categories. These characterisations were used to explain why health-damaging beliefs and behaviours were more prevalent among men and also why men were better suited for certain kinds of jobs, albeit with potential costs to their health. Men also believed that women were protected from the damaging physical and emotional impact of manual employment because of their primary role within the home and because they were less emotionally robust, which required men to shield women from the stresses they experienced. However, men's emotional withdrawal can also be viewed as another example of how men use whatever resources are available to achieve and maintain dominance over women. Finally, the article demonstrates how a gender- and class-based approach can capture the impact of men's health-related practices alongside the broader cultural and structural influences on men's health

Knowledge is power? : the role of experiential knowledge in genetically 'risky' reproductive decisions

Knowledge of the condition being tested for is increasingly acknowledged as an important factor in prenatal testing and screening decisions. An analysis of the way in which family members living with an inheritable condition use and value this knowledge has much to add to debates around whether and how this type of knowledge could be made available to prospective parents facing screening decisions. This paper reports on in-depth interviews with sixty-one people (conducted 2007-9), with a genetic condition in their family, Spinal Muscular Atrophy (SMA). Many participants described their intimate familial knowledge of SMA as offering them valuable insights with which they could imagine future lives. Other participants, however, found themselves trapped between their experiential knowledge of SMA and their (often) competing responsibility to maintain the wellbeing of their family. Still others established a ‘hierarchy’ of knowledge to rank the authenticity of different family member’s accounts of SMA in order to discredit, or justify, their decisions. This paper highlights the way in which experiential knowledge of the condition being tested for cannot be unproblematically assumed to be a useful resource in the context of prenatal testing and screening decisions, and may actually constrain reproductive decisions

The effect of strategies of personal resilience on depression recovery in an Australian cohort : a mixed methods study

Strategies of personal resilience enable successful adaptation in adversity. Among patients experiencing depression symptoms, we explored which personal resilience strategies they find most helpful, and tested the hypothesis that use of these strategies improves depression recovery. We used interview and survey data from the Diagnosis, Management and Outcomes of Depression in Primary Care 2005 cohort of patients experiencing depression symptoms in Victoria, Australia. 564 participants answered a computer assisted telephone interview question at 12 months follow-up, about what they found most helpful for their depression, stress or worries. Depressive disorder and severity were measured at annual follow-up using the Composite International Diagnostic Interview and the PHQ-9 self-rating questionnaire. Using interview responses we categorised participants as users or not of strategies of personal resilience, specifically, drawing primarily on expanding their own inner resources or pre-existing relationships: 316 (56%) were categorised as primarily users of personal resilience strategies. Of these, 193 (61%) reported expanding inner resources, 79 (25%) drawing on relationships, and 44 (14%) reported both. There was no association between drawing on relationships and depression outcome. There was evidence supporting an association between expanding inner resources and depression outcome: 25% of users having major depressive disorder one year later compared to 38% of non-users (adjusted OR 0.59, CI 0.36-0.97). This is the first study to show improved outcome for depression for those who identify as most helpful the use of personal resilience strategies. The difference in outcome is important as expanding inner resources includes a range of low intensity, yet commonly available strategies

How to move an electromagnetic field?

As a first principle, it is the basic assumption of the standard relativistic formulation of classical electrodynamics (ED) that the physical laws describing the electromagnetic phenomena satisfy the relativity principle (RP). According to the standard view, this assumption is absolutely unproblematic, and its correctness is well confirmed, at least in a hypothetico-deductive sense, by means of the empirical confirmation of the consequences derived from it. In this paper, we will challenge this customary view as being somewhat simplistic. The RP is actually used in exceptional cases satisfying some special conditions. As we will see, however, it is quite problematic how the RP must be understood in the general case of a coupled particles + electromagnetic field system