Causal structure of the entanglement renormalization ansatz

We show that the multiscale entanglement renormalization ansatz (MERA) can be reformulated in terms of a causality constraint on discrete quantum dynamics. This causal structure is that of de Sitter space with a flat space-like boundary, where the volume of a spacetime region corresponds to the number of variational parameters it contains. This result clarifies the nature of the ansatz, and suggests a generalization to quantum field theory. It also constitutes an independent justification of the connection between MERA and hyperbolic geometry which was proposed as a concrete implementation of the AdS-CFT correspondence.

Equality of opportunity, cultural diversity and claims for fairness

The present paper examines some of the tensions, problems and challenges associated with claims for equality of opportunity (the fairness argument). The introductory part identifies three separate forms of justification for public education, including the argument associated with equality of opportunity. Part II examines in detail two questions that reveal part of the anatomy of equality of opportunity: (1) what an opportunity is, and (2) when individuals’ opportunities are equal. This is followed by a presentation of the two basic principles of equality of opportunity: (1) the principle of non-discrimination, and (2) the “levelling the playing field” principle. The next part takes up the multiculturalist hypothesis advanced by minority groups for the accommodation and recognition of cultural diversity. This is followed by the identification of a set of claims comprising the “fairness argument”. The last section focuses on the “currency problem” associated with cultural diversity as a form of “unfair disadvantage”. Part V examines two of the major shortcomings associated with the multicultural conception of equality of opportunity, while the concluding part discusses some of the questions that must be answered by any conception of equal opportunities. (DIPF/Orig.)

Asymptotic scattering and duality in the one-dimensional three-state quantum Potts model on a lattice

We determine numerically the single-particle and the two-particle spectrum of the three-state quantum Potts model on a lattice by using the density matrix renormalization group method, and extract information on the asymptotic (small momentum) S-matrix of the quasiparticles. The low energy part of the finite size spectrum can be understood in terms of a simple effective model introduced in a previous work, and is consistent with an asymptotic S-matrix of an exchange form below a momentum scale p*. This scale appears to vanish faster than the Compton scale, mc, as one approaches the critical point, suggesting that a dangerously irrelevant operator may be responsible for the behaviour observed on the lattice.

Coleman’s third report

The article analyses the (third) Coleman Report on private and public schools. The report scrutinises the relationship between private and public schools and shows that private school students show better academic achievement. Coleman concluded that these findings provided a strong argument in favour of public financial support for private schools. However, he identified a number of school characteristics that he believed to be related to student achievement. According to his analysis, these characteristics were not limited to private schools; public schools exhibiting the same characteristics also had good results. Coleman interpreted the available data in favour of financial aid to private schools, although this was not the only possible interpretation. An alternative conclusion would have been to encourage these characteristics in public schools. Why did Coleman disregard this possibility? Why did he deviate from his usual scientific rigour? The present article suggests that there appear to be two reasons for the narrow interpretation of the relationship between public and private schools in Coleman's third report. The first lies in Coleman's notion of contemporary society as a constructed system in which every individual actor holds a place in the structure and requires incentives in order to act to the benefit of society. In the case of education, the goal of the institution is to ensure the high cognitive achievement of students, and the incentive is related to choice and competition. The second reason is related to Coleman's vision of sociology as a discipline aiding the construction of an effective society. (DIPF/Orig.)

A representation-free description of the Kasevich-Chu interferometer: a resolution of the redshift controversy

Motivated by a recent claim by Muller et al (2010 Nature 463 926-9) that an atom interferometer can serve as an atom clock to measure the gravitational redshift with an unprecedented accuracy, we provide a representation-free description of the Kasevich-Chu interferometer based on operator algebra. We use this framework to show that the operator product determining the number of atoms at the exit ports of the interferometer is a c-number phase factor whose phase is the sum of only two phases: one is due to the acceleration of the phases of the laser pulses and the other one is due to the acceleration of the atom. This formulation brings out most clearly that this interferometer is an accelerometer or a gravimeter. Moreover, we point out that in different representations of quantum mechanics such as the position or the momentum representation the phase shift appears as though it originates from different physical phenomena. Due to this representation dependence conclusions concerning an enhanced accuracy derived in a specific representation are unfounded.

Tomographic readout of an opto-mechanical interferometer

The quantum state of light changes its nature when being reflected off a mechanical oscillator due to the latter's susceptibility to radiation pressure. As a result, a coherent state can transform into a squeezed state and can get entangled with the motion of the oscillator. Full information of the state of light can only be gathered by a tomographic measurement. Here we demonstrate a tomographic interferometer readout by measuring arbitrary quadratures of the light field exiting a Michelson-Sagnac interferometer that contains a thermally excited high-quality silicon nitride membrane. A readout noise of 1.9 x 10(-16) mHz(-1/2) around the membrane's fundamental oscillation mode at 133 kHz has been achieved, going below the peak value of the standard quantum limit by a factor of 8.2 (9 dB). The readout noise was entirely dominated by shot noise in a rather broad frequency range around the mechanical resonance.

The age of studies and reports: selected elements concerning the background of encounters defining the power of education

In the present paper, we discuss the time before the “age of reports”. Besides the Coleman Report in the period of Coleman, the Lady Plowden Report also appeared, while there were important studies in France (Bourdieu & Passeron, 1964; Peyre, 1959) and studies that inaugurated comprehensive education in Nordic countries. We focus on the period after the World War II, which was marked by rising economic nationalism, on the one hand, and by the second wave of mass education, on the other, bearing the promise of more equality and a reduction of several social inequalities, both supposed to be ensured by school. It was a period of great expectations related to the power of education and the rise of educational meritocracy. On this background, in the second part of the paper, the authors attempt to explore the phenomenon of the aforementioned reports, which significantly questioned the power of education and, at the same time, enabled the formation of evidence-based education policies. In this part of the paper, the central place is devoted to the case of socialist Yugoslavia/Slovenia and its striving for more equality and equity through education. Through the socialist ideology of more education for all, socialist Yugoslavia, with its exaggerated stress on the unified school and its overemphasised belief in simple equality, overstepped the line between relying on comprehensive education as an important mechanism for increasing the possibility of more equal and just education, on the one hand, and the myth of the almighty unified school capable of eradicating social inequalities, especially class inequalities, on the other. With this radical approach to the reduction of inequalities, socialist policy in the then Yugoslavia paradoxically reduced the opportunity for greater equality, and even more so for more equitable education. (DIPF/Orig.)

Exciton-mediated photothermal cooling in GaAs membranes

Cooling of the mechanical motion of a GaAs nano-membrane using the photothermal effect mediated by excitons was recently demonstrated by some of the authors (Usami et al 2012 Nature Phys. 8 168) and provides a clear example of the use of thermal forces to cool down mechanical motion. Here, we report on a single-free-parameter theoretical model to explain the results of this experiment which matches the experimental data remarkably well.

Social capital and educational achievements: Coleman vs. Bourdieu

The influence of social capital on an individual’s educational achievements is the subject of numerous scientific papers. Research on social capital is most frequently based on Coleman’s (1988) or Bourdieu’s (1986) theories of capital, which are related to different paradigms of social theory: whereas Coleman’s approach has its roots in structural functionalism, Bourdieu’s approach contains elements of conflict theory. A number of authors, starting with Bourdieu, attempt to explain and prove that, when connected with the education of individuals, the activity of social capital facilitates social reproduction. Other authors support the notion that social capital is, in fact, a powerful weapon that encourages social mobility. A third group of researchers emphasise that neither of these approaches in isolation can entirety explain the influences of social capital on an individual’s education (Ho, 2003). The present paper offers a review of research focusing on the influences of social capital on educational achievements, while outlining the fundamental differences between the two theoretical approaches that are most frequently used for research of this topic. The aim of the paper is to explain the influence of social capital on an individual’s educational achievements under Bourdieu’s and Coleman’s theoretical concepts, and to establish whether combining the approaches is possible. The conclusion and arguments show that it is legitimate to use all three theoretical approaches. (DIPF/Orig.)

A proposal for self-correcting stabilizer quantum memories in 3 dimensions (or slightly less)

We propose a family of local CSS stabilizer codes as possible candidates for self-correcting quantum memories in 3D. The construction is inspired by the classical Ising model on a Sierpinski carpet fractal, which acts as a classical self-correcting memory. Our models are naturally defined on fractal subsets of a 4D hypercubic lattice with Hausdorff dimension less than 3. Though this does not imply that these models can be realized with local interactions in R3, we also discuss this possibility. The X and Z sectors of the code are dual to one another, and we show that there exists a finite temperature phase transition associated with each of these sectors, providing evidence that the system may robustly store quantum information at finite temperature.

Disentangling the magnetic force noise contribution in LISA Pathfinder

Magnetically-induced forces on the inertial masses on-board LISA Path finder are expected to be one of the dominant contributions to the mission noise budget, accounting for up to 40%. The origin of this disturbance is the coupling of the residual magnetization and susceptibility of the test masses with the environmental magnetic field. In order to fully understand this important part of the noise model, a set of coils and magnetometers are integrated as a part of the diagnostics subsystem. During operations a sequence of magnetic excitations will be applied to precisely determine the coupling of the magnetic environment to the test mass displacement using the on-board magnetometers. Since no direct measurement of the magnetic field in the test mass position will be available, an extrapolation of the magnetic measurements to the test mass position will be carried out as a part of the data analysis activities. In this paper we show the first results on the magnetic experiments during an end-to-end LISA Path finder simulation, and we describe the methods under development to map the magnetic field on-board.

The sources of inequity in the education system of Serbia and how to combat them

The concept of equal opportunity for all students is deeply embedded in the Serbian constitution and in education laws. On that level, there is no doubt that everyone is ensured an opportunity to receive quality education. Many measures in education policy have been created specifically to achieve this objective and make the system fair and inclusive. The Coleman Report was linked to a wave of optimism that certain educational measures would help in achieving these noble goals. This aim is a high priority in education in a democratic country, and due to its importance needs to be re-examined. Thus, the present research examines the equity of students in the Serbian education system, detecting areas on all educational levels that could be (or already are) systemic sources of inequity (e.g., criteria for preschool institution enrolment, the system of student awards, rationalisation of the school network, the concept of entrance exams to secondary school or university, etc.). A number of measures have already been taken in the system specifically to deal with inequity (e.g., the Preschool Preparatory Programme, dropout measures, inclusion, scholarships, etc.). The effects of these measures in particular are analysed in the present work. In addition to an analysis of the systemic sources of inequity in the Serbian education system, the article also makes recommendations for their overcoming. (DIPF/Orig.)

Comics as a literary-didactic method and their use for reducing gender differences in reading literacy at the primary level of education

The aim of the present study was to examine the effect of the systematic use of comics as a literary-didactic method to reduce gender differences in reading literacy and reading motivation at the primary level of education. It was assumed that the use of comics would have a positive effect on pupils’ reading literacy and reading motivation, while also reducing the aforementioned differences between boys and girls. The dimensions of reading literacy and reading motivation were examined in experimental and control groups, before and after the intervention, by means of questionnaires and tests for pupils. The sample consisted of 143 pupils from second to fifth grade from two Slovenian primary schools in a rural environment, of which 73 pupils participated in the experimental group and 70 pupils represented the control group. Effects of the use of comics as a literary-didactic method were not found: using comics as a literary-didactic method did not have a statistically significant effect on pupils’ reading literacy and reading motivation. However, when the four-way structure of the research (taking into account the age and gender of the pupils) was considered, some subgroups showed a statistically significant increase in reading interest and attitude towards reading. No reduction of gender differences in reading literacy and reading motivation was found. Based on the results, guidelines for further research are established and suggestions are offered for teachers’ work. (DIPF/Orig.)

A Strategy to Characterize the LISA-Pathfinder Cold Gas Thruster System

The cold gas micro-propulsion system that will be used during the LISA-Pathfinder mission will be one of the most important component used to ensure the "free-fall" of the enclosed test masses. In this paper we present a possible strategy to characterize the effective direction and amplitude gain of each of the 6 thrusters of this system.

Durchlässigkeit als mehrdimensionale Aufgabe. Bedingungen für flexible Bildungsübergänge

Ein institutionell durchlässiges Bildungssystem ist … eine grundlegende Voraussetzung für die Ermöglichung flexibler Bildungsbiographien und damit auch die Verwirklichung von gleichen Bildungschancen. Aber wie kann institutionelle Durchlässigkeit zwischen beruflicher und akademischer Bildung in Deutschland gefördert werden? Und wie kann dafür Sorge getragen werden, dass trotz einer Flexibilisierung die jeweilige Kernlogik von beruflicher und akademischer Bildung aufrecht erhalten wird, die von vielen Akteuren in ihrer Komplementarität als Träger eines erfolgreichen Bildungssystems gesehen werden? In dieser Expertise werden … die Teildimensionen institutioneller Durchlässigkeit genauer betrachtet: (I.) Zugang in Bildungsbereiche, (II.) Anrechnung von Erlerntem, (III.) organisationale Verbindung von Bildungsbereichen und (IV.) Umgang mit heterogenen Bedürfnissen (Abschnitt 2). Im nächsten Schritt wird ein Überblick über wichtige Initiativen und Regelungen zu Durchlässigkeit in Deutschland gegeben (Abschnitt 3). Es folgt eine kurze Vorstellung des methodischen Vorgehens und Begründung der Fallauswahl (Sektion 4.1). Darauf aufbauend werden drei (über-)regionale Initiativen, in denen Durchlässigkeit zwischen Berufs- und Hochschulbildung innovativ gefördert wird, genauer vorgestellt und analysiert. Dabei handelt es sich um die "Offene Hochschule Niedersachsen", die Duale Hochschule Baden-Württemberg und den Modellversuch "Duale Berufsausbildung mit Abitur in Sachsen" (DuBAS) (Abschnitt 4). Übergeordnetes Ziel ist es, anhand des Überblicks über durchlässigkeitsfördernde Programme, aber insbesondere auch durch die vertiefende Darstellung der regionalen Fallstudien, mögliche Bedingungen für erfolgreiche Durchlässigkeitsstrukturen zwischen Berufs- und Hochschulbildung, aber auch Barrieren zu identifizieren und daraus relevante Schlussfolgerungen abzuleiten (Abschnitt 5). (DIPF/Orig.)