Field Tuning the G-Factor in InAs Nanowire Double Quantum Dots

We study the effects of magnetic and electric fields on the g-factors of spins confined in a two-electron InAs nanowire double quantum dot. Spin sensitive measurements are performed by monitoring the leakage current in the Pauli blockade regime. Rotations of single spins are driven using electric-dipole spin resonance. The g-factors are extracted from the spin resonance condition as a function of the magnetic field direction, allowing determination of the full g-tensor. Electric and magnetic field tuning can be used to maximize the g-factor difference and in some cases altogether quench the EDSR response, allowing selective single spin control.Comment: Related papers at http://pettagroup.princeton.ed

Radio frequency charge sensing in InAs nanowire double quantum dots

We demonstrate charge sensing of an InAs nanowire double quantum dot (DQD) coupled to a radio frequency (rf) circuit. We measure the rf signal reflected by the resonator using homodyne detection. Clear single dot and DQD behavior are observed in the resonator response. rf-reflectometry allows measurements of the DQD charge stability diagram in the few-electron regime even when the dc current through the device is too small to be measured. For a signal-to-noise ratio of one, we estimate a minimum charge detection time of 350 microseconds at interdot charge transitions and 9 microseconds for charge transitions with the leads.Comment: Related papers at http://pettagroup.princeton.ed

Film matters: Historical and material considerations of colour, movement and sound in film

The narratives presented in most film histories seem to ignore the essential material components of analogue film stock. Film matters focuses on material components of the film image – specifically colour, movement and sound – with the aim of telling a material history in a contemporary, ‘post-digital’ environment. The aim of this history is to show how film as a material has participated in the building of social and political realities that are still at work today. My practice-led research results in two videos on colour and a 16 mm film on movement and sound. In these works I practice alternative ways of history writing and telling that may not be written, but which leave their sediments in the materialities and projections of film. My research is embedded in a historical framework, but at the same time reflects upon the actuality of the political history of film. History and memory images are disassembled into their components in order to make visible that which the image does not show, but of which it is made. Setting out from this methodology, in Chapter 1 I research the representational and constitutional participation of these material components in film’s different temporalities. Through a close reading of several seminal films and moving image works I focus on the interplay between film, time and certain contexts of social and political structures, in order to understand how these are constructed along with material history. Chapter 2 explores movement, rhythm and physicality in the materiality of film. Setting out from the experimental set-up of the film Fugue (2015), the chapter analyses the relationship between physicality(of a body) and materiality (of the film) founded on movement. I claim that movement on film and movement of film produce involuntary side products, which become readable in film through dance-like movements and rhythms. I discover micromovements and habit-formation in both the movement of the film and the movement of the body and seek to read their political and transformative potential in situations in which they were joined, or when transitions from one to the other took place. In Chapter 3 I analyse the role of colour within film history and collective memory. Colour, as a chemical component of the film emulsion, has a temporal permanence, seeping into the grounds and bodies as chemicality, as toxic substance. Colour as a transtemporal figure is elaborated in the video Red, she said (2011), which focuses on Technicolor, looking at the colonising power of colour film by characterising the film emulsion as an autonomous actor within the rules and boundaries of cinematic space. The research into colour continues with Rainbow’s Gravity (2014) – a cinematic study of the production, use and employment of colour in the Nazi period and the politics of memory it entails. I found that in many historical cases colour can take on an active role in processes of memorisation. The thesis concludes in a reflection on the practice of working with a negative approach. In my search for forms of resistance within the moving image that interrupt constant reproductions of power and its representations, I detect the necessity of working with negativity in a processual way

The Pivotal Role of Causality in Local Quantum Physics

In this article an attempt is made to present very recent conceptual and computational developments in QFT as new manifestations of old and well establihed physical principles. The vehicle for converting the quantum-algebraic aspects of local quantum physics into more classical geometric structures is the modular theory of Tomita. As the above named laureate to whom I have dedicated has shown together with his collaborator for the first time in sufficient generality, its use in physics goes through Einstein causality. This line of research recently gained momentum when it was realized that it is not only of structural and conceptual innovative power (see section 4), but also promises to be a new computational road into nonperturbative QFT (section 5) which, picturesquely speaking, enters the subject on the extreme opposite (noncommutative) side.Comment: This is a updated version which has been submitted to Journal of Physics A, tcilatex 62 pages. Adress: Institut fuer Theoretische Physik FU-Berlin, Arnimallee 14, 14195 Berlin presently CBPF, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro, Brazi

Anomalous Scale Dimensions from Timelike Braiding

Using the previously gained insight about the particle/field relation in conformal quantum field theories which required interactions to be related to the existence of particle-like states associated with fields of anomalous scaling dimensions, we set out to construct a classification theory for the spectra of anomalous dimensions. Starting from the old observations on conformal superselection sectors related to the anomalous dimensions via the phases which appear in the spectral decomposition of the center of the conformal covering group $Z(\widetilde{SO(d,2)}),$ we explore the possibility of a timelike braiding structure consistent with the timelike ordering which refines and explains the central decomposition. We regard this as a preparatory step in a new construction attempt of interacting conformal quantum field theories in D=4 spacetime dimensions. Other ideas of constructions based on the $AdS_{5}$-$CQFT_{4}$ or the perturbative SYM approach in their relation to the present idea are briefly mentioned.Comment: completely revised, updated and shortened replacement, 24 pages tcilatex, 3 latexcad figure

Causality and dispersion relations and the role of the S-matrix in the ongoing research

The adaptation of the Kramers-Kronig dispersion relations to the causal localization structure of QFT led to an important project in particle physics, the only one with a successful closure. The same cannot be said about the subsequent attempts to formulate particle physics as a pure S-matrix project. The feasibility of a pure S-matrix approach are critically analyzed and their serious shortcomings are highlighted. Whereas the conceptual/mathematical demands of renormalized perturbation theory are modest and misunderstandings could easily be corrected, the correct understanding about the origin of the crossing property requires the use of the mathematical theory of modular localization and its relation to the thermal KMS condition. These new concepts, which combine localization, vacuum polarization and thermal properties under the roof of modular theory, will be explained and their potential use in a new constructive (nonperturbative) approach to QFT will be indicated. The S-matrix still plays a predominant role but, different from Heisenberg's and Mandelstam's proposals, the new project is not a pure S-matrix approach. The S-matrix plays a new role as a "relative modular invariant"..Comment: 47 pages expansion of arguments and addition of references, corrections of misprints and bad formulation

The paradigm of the area law and the structure of transversal and longitudinal lightfront degrees of freedom

It is shown that an algebraically defined holographic projection of a QFT onto the lightfront changes the local quantum properties in a very drastic way. The expected ubiquitous vacuum polarization characteristic of QFT is confined to the lightray (longitudinal) direction, whereas operators whose localization is transversely separated are completely free of vacuum correlations. This unexpected ''transverse return to QM'' combined with the rather universal nature of the strongly longitudinal correlated vacuum correlations (which turn out to be described by rather kinematical chiral theories) leads to a d-2 dimensional area structure of the d-1 dimensional lightfront theory. An additive transcription in terms of an appropriately defined entropy related to the vacuum restricted to the horizon is proposed and its model independent universality aspects which permit its interpretation as a quantum candidate for Bekenstein's area law are discussed. The transverse tensor product foliation structure of lightfront degrees of freedom is essential for the simplifying aspects of the algebraic lightcone holography. Key-words: Quantum field theory; Mathematical physics, Quantum gravityComment: 16 pages latex, identical to version published in JPA: Math. Gen. 35 (2002) 9165-918

Extant ape dental topography and its implications for reconstructing the emergence of early Homo

Dental topography has successfully predicted the diets of species in several extant and extinct 11 mammalian clades. However, dental topographic dietary reconstructions have high success rates only 12 when closely related taxa are compared. Given the dietary breadth that exists among extant apes and 13 likely existed among fossil hominins, dental topographic values from many species and subspecies of 14 great apes are necessary for making dietary inferences about the hominin fossil record. Here, we 15 present the results of one metric of dental topography, Dirichlet normal energy (DNE), for seven groups 16 of great apes (Pongo pygmaeus pygmaeus, Pan paniscus, Pan troglodytes troglodytes and 17 schweinfurthii, Gorilla gorilla gorilla, Gorilla beringei graueri and beringei). DNE was inadequate at 18 differentiating folivores from frugivores, but was adequate at predicting which groups had more fibrous 19 diets among sympatric African apes. Character displacement analyses confirmed there is substantial 20 dental topographic and relative molar size (M1:M2 ratio; length, width, and area) divergence in sympatric 21 apes when compared to their allopatric counterparts, but character displacement is only present in 22 relative molar size when DNE is also considered. Presence of character displacement is likely due to 23 indirect competition over similar food resources. Assuming similar ecological conditions in the Plio-24 Pleistocene, the derived masticatory apparatuses of the robust australopithecines and early Homo may 25 be due to indirect competition over dietary resources between the taxa, causing dietary niche 26 partitioning. Our results imply that dental topography cannot be used to predict dietary categories in 27 fossil hominins without consideration of ecological factors such as dietary and geographic overlap. In 28 addition, our results may open new avenues for understanding the community compositions of early 29 hominins and the formation of specific ecological niches among hominin taxa