General Relativity as a Hybrid theory: The Genesis of Einstein's work on the problem of motion

In this paper I describe the genesis of Einstein's early work on the problem of motion in general relativity (GR): the question of whether the motion of matter subject to gravity can be derived directly from the Einstein field equations. In addressing this question, Einstein himself always preferred the vacuum approach to the problem: the attempt to derive geodesic motion of matter from the vacuum Einstein equations. The paper first investigates why Einstein was so skeptical of the energy-momentum tensor and its role in GR. Drawing on hitherto unknown correspondence between Einstein and George Yuri Rainich, I then show step by step how his work on the vacuum approach came about, and how his quest for a unified field theory informed his interpretation of GR. I show that Einstein saw GR as a hybrid theory from very early on: fundamental and correct as far as gravity was concerned but phenomenological and effective in how it accounted for matter. As a result, Einstein saw energy-momentum tensors and singularities in GR as placeholders for a theory of matter not yet delivered. The reason he preferred singularities was that he hoped that their mathematical treatment would give a hint as to the sought after theory of matter, a theory that would do justice to quantum features of matter

Mass-Energy-Momentum: Only there because of Spacetime?

I describe how relativistic field theory generalises the paradigm property of material systems, the possession of mass, to the requirement that they have a mass-energy-momentum density tensor associated with them. I argue that the latter does not represent an intrinsic property of matter. For it will become evident that its definition depends on the metric field in a variety of ways. Accordingly, since the metric field represents the geometry of spacetime itself, the properties of mass, stress, energy and momentum should not be seen as intrinsic properties of matter, but as relational properties that material systems have only in virtue of their relation to spacetime structure

Current state and challenges of science in today's TV: a look at the interplay between supply and demand on european media markets

Aquest estudi avalua l'estat actual de la ciència a la televisió i els seus reptes de futur. Les avaluacions es basen substancialment en un parell de media studies empírics comparatius, publicats en l'última dècada, centrats bé en la producció de continguts de ciències a la televisió europea, bé en la recepció d'aquests continguts per part del públic europeu. Aquest treball integra ambdues perspectives en un quadre complet per trobar la clau de la interacció bàsica entre l'oferta i la demanda de la ciència a la televisió. Es diagnostica que l'oferta de programes especialitzats depèn predominantment de canals públics amb finançament fort i convenientment estructurats, essent especialment clau la presència de petits canals públics especialitzats per explicar les diferències considerables en la programació a tota Europa. Es diagnostica, a més, que la demanda d'aquests programes per part del públic europeu en general no és suficient per estimular-ne la producció, particularment en el cas dels espectadors més joves, que mostren una manca rellevant d'interès. Per concloure, s'identifiquen els principals reptes a què s'enfronten els productors de televisió quan es tracta d'arribar a la major audiència possible.This study assesses the current state of science in TV and its future challenges. The assessments are based in substantial parts on a couple of comparative empirical media studies published in the last decade. The focus of these studies was either on the production of science contents in European TV, or on the reception of these contents by European Audiences. This paper integrates both perspectives into a comprehensive picture in order to unlock the basic interplay between supply and demand of Science in TV. It is diagnosed that the supply of specialised programmes is predominantly dependent upon financially strong and conveniently structured public service channels, especially the presence of small public niche channels is key to explain the considerable differences of programme offers across Europe. It is further diagnosed that the demand for these programmes by European audiences in general is not sufficient to stimulate production, of special relevance is the lack of appeal for younger viewers. We conclude by identifying main challenges TV producers face when trying to reach the largest possible audience

On Government, Governance and Judicial Review: The Case of European Competition Policy

From a traditional rationalist principal-agent framework, the development of the European Community's competition policy could appear as a straightforward story of agency loss. However, the recent overhaul of competition policy, which the Community presented in terms of decentralisation, appears to have changed the story. We are confronted with the uncommon event of an agent (the European Commission) returning some of its powers to the principals (the member states). This paper resolves the puzzle by highlighting the role of the Commission and of European courts. It has become part of the Commission's strategy to pursue its objectives through legally non-binding instruments such as notices or guidelines or co-operation in networks. These instruments do not need the approval of the Council of Ministers or the European Parliament. With the Commission's promotion of new modes of governance, the link between sectoral governance (in terms of regulation specific to competition policy) and the governmental shadow of hierarchy shifted to an increasing extent to judicial review by European courts. Alongside this shift, the character of judicial review has changed in the direction of judicial control, as European courts no longer restrict themselves to review of the legality of Commission actions, but also engage in assessing the facts themselve

A Numerical Analysis of PSM with Applications to DDEs

The Modified Picard method (PSM) for approximating IVPs (in a non-standard numerical fashion) involving ODEs or PDEs has been established as a viable option (see Sochacki and Parker et al.). The form of the approximating method allows itself to be used without much labor on delay differential equations (where the vector field at the current time relies on the state of the system at some earlier time as well as the current time). The properties of the solutions to the DDEs can be different depending on how the delay shows up, hence there are a myriad of subclasses (see Baker, Paul and Wille) and as a consequence, their numerical simulation can be delicate. This jump to DDEs via PSM appears to be possible without worrying about which subclass is involved

GARP derived TGFβ promotes acetylation-mediated Foxp3 protein stabilization and Treg functionality

Diseases of immune dysregulation are frequently caused by single gene mutations in central pathways of immune tolerance. They are characterised by heterogeneous clinical manifestations with autoimmune symptoms based on defects in mechanisms regulating self-tolerance. Identification of the genetic cause of such diseases has critical implications for the treatment of patients. To identify underlying molecular etiologies, patients suffering from immune dysregulation were subjected to whole-exome sequencing. Two patients bearing previously undescribed mutations of LRRC32 encoding glycoprotein A repetitions predominant (GARP) were identified. GARP has been recently described to be specifically expressed on regulatory T cells (Tregs) and is important for their suppressive capacity. GARP is involved in TGFβ1 activation by binding latent TGFβ1 in the cytoplasm and translocating it to the cell surface. The importance of fully functional Tregs is well described for maintaining immunological self-tolerance and homeostasis of the immune system. Tregs control destructive immune responses against pathogens and limit reactions towards self antigens. However, the function of this TGFβ1 source and the underlying mechanisms are not yet completely understood. My PhD thesis presents data that reinforces the importance of GARP as a regulator of Treg function and stability. It describes two patients with LRRC32 mutations, characterises the function of GARP in cellular and molecular detail and demonstrates the importance of functional Tregs for physiological immune homeostasis in men and mice. The study identifies a novel link between GARP dependent TGFβ signalling in Tregs and expression of the Treg specific histone deacetylase (HDAC)9 that promotes Foxp3 deacetylation, which contributes to an instable dysfunctional Treg phenotype. The research shows that Tregs from patients with LRRC32 mutations have only minimal GARP expression on the cell surface and reduced TGFβ signalling. Tregs from these patients further show a strongly diminished Treg suppressor function and significant reduction in Treg numbers and frequency. GARP functions are characterised in a novel molecular detail using a model of conditional Garp-deficiency in mice. Here the study confirms increased susceptibility to inflammatory diseases once GARP expression is decreased on Tregs. Consistent with the effects observed in patients, Garp-deficiency in mice leads to absence of latent TGFβ on the cell surface of Tregs, reduced TGFβ signalling and diminished suppressor function. Further, Treg from Garp-deficient mice exhibit an unstable phenotype due to diminished Foxp3 protein acetylation and stability. In sum, the PhD thesis reinforces the understanding of immunological mechanisms of immune dysregulation and expands the knowledge of immunological function of GARP as an important regulator of Treg stability

Literal versus Careful Interpretations of Scientific Theories: The Vacuum Approach to the Problem of Motion in General Relativity

The problem of motion in general relativity is about how exactly the gravitational field equations, the Einstein equations, are related to the equations of motion of material bodies subject to gravitational fields. This article compares two approaches to derive the geodesic motion of (test) matter from the field equations: the ‘T approach’ and the ‘vacuum approach’. The latter approach has been dismissed by philosophers of physics because it apparently represents material bodies by singularities. I argue that a careful interpretation of the approach shows that it does not depend on introducing singularities at all and that it holds at least as much promise as the T approach