Transfer Matrices and Excitations with Matrix Product States

We investigate the relation between static correlation functions in the ground state of local quantum many-body Hamiltonians and the dispersion relations of the corresponding low energy excitations using the formalism of tensor network states. In particular, we show that the Matrix Product State Transfer Matrix (MPS-TM) - a central object in the computation of static correlation functions - provides important information about the location and magnitude of the minima of the low energy dispersion relation(s) and present supporting numerical data for one-dimensional lattice and continuum models as well as two-dimensional lattice models on a cylinder. We elaborate on the peculiar structure of the MPS-TM's eigenspectrum and give several arguments for the close relation between the structure of the low energy spectrum of the system and the form of static correlation functions. Finally, we discuss how the MPS-TM connects to the exact Quantum Transfer Matrix (QTM) of the model at zero temperature. We present a renormalization group argument for obtaining finite bond dimension approximations of MPS, which allows to reinterpret variational MPS techniques (such as the Density Matrix Renormalization Group) as an application of Wilson's Numerical Renormalization Group along the virtual (imaginary time) dimension of the system.Comment: 39 pages (+8 pages appendix), 14 figure

A ship-based methodology for high precision atmospheric oxygen measurements and its application in the Southern Ocean region

A method for achieving continuous high precision measurements of atmospheric O-2 is presented based on a commercially available fuel-cell instrument, (Sable Systems, Oxzilla FC-II) with a precision of 7 per meg (approximately equivalent to 1.2 ppm) for a 6-min measurement. The Oxzilla was deployed on two voyages in the Western Pacific sector of the Southern Ocean, in February 2003 and in April 2004, making these the second set of continuous O-2 measurements ever made from a ship. The results show significant temporal variation in O-2, in the order of +/- 10 per meg over 6-hourly time intervals, and substantial spatial variation. Data from both voyages show an O-2 maximum centred on 50 degrees S, which is most likely to be the result of biologically driven O-2 outgassing in the region of subtropical convergence around New Zealand, and a decreasing O-2 trend towards Antarctica. O-2 from the ship-based measurements is elevated compared with measurements from the Scripps Institution of Oceanography flask-sampling network, and the O-2 maximum is also not captured in the network observations. This preliminary study shows that ship-based continuous measurements are a valuable addition to current fixed site sampling programmes for the understanding of ocean-atmosphere O-2 exchange processes. [References: 39

Transfer matrices and excitations with matrix product states

We use the formalism of tensor network states to investigate the relation between static correlation functions in the ground state of local quantum many-body Hamiltonians and the dispersion relations of the corresponding low-energy excitations. In particular, we show that the matrix product state transfer matrix (MPS-TM)—a central object in the computation of static correlation functions—provides important information about the location and magnitude of the minima of the low-energy dispersion relation(s), and we present supporting numerical data for one-dimensional lattice and continuum models as well as two-dimensional lattice models on a cylinder. We elaborate on the peculiar structure of the MPS-TM's eigenspectrum and give several arguments for the close relation between the structure of the low-energy spectrum of the system and the form of the static correlation functions. Finally, we discuss how the MPS-TM connects to the exact quantum transfer matrix of the model at zero temperature. We present a renormalization group argument for obtaining finite bond dimension approximations of the MPS, which allows one to reinterpret variational MPS techniques (such as the density matrix renormalization group) as an application of Wilson's numerical renormalization group along the virtual (imaginary time) dimension of the system

Towards an Appropriation Infrastructure: Supporting User Creativity in IT Adoption

Research on the adoption of information systems (IS) often stated technology as a fixed entity. Following the ’practical turn’ in IS we argue that information technology artefacts are mainly ’cultural artefacts’, which are shaped in a social process of appropriation where software usage is accompanied by processes of interpretation, negotiation or change in organizations. We elaborate on a (neo-)Marxian interpretation of appropriation from a design-oriented perspective in order to investigate the possibilities of technological support of activities of appropriation work. To capture the different facets of appropriation, we combine theoretical concepts of social capital and activity-based learning. With the help of this theoretical orientation, we systemize empirical evidence from several research projects in order to detect recurring patterns. We use these patterns to develop a generic architecture for actively supporting the social activity of appropriating the cultural artefact in context of its usage

Determination of a correction factor for the interaction potential of He + ions backscattered from a Cu(1 0 0) surface

Abstract We have used coaxial impact collision ion scattering spectroscopy (CAICISS) data collected from 3 keV He + ions backscattered from a Cu(1 0 0) surface in different azimuthal orientations to investigate the influence of the screening length on CAICISS polar angle scans. We have compared the experimental data to computer simulations generated with the FAN code and found that for our experimental conditions an exceptionally low value of 0.53 was required for the correction factor to the Firsov screening length used with the ThomasFermi-Moliere potential. In addition we found that the Ziegler-Biersack-Littmark potential is not applicable, resulting in incorrect peak positions in the CAICISS polar angle plots

Tracking Down the Intuitiveness of Gesture Interaction in the Truck Domain

AbstractTouchless hand gesture control potentially leads to a safer, more comfortable and more intuitive Human Vehicle Interaction (HVI) if relevant ergonomic requirements are met. To achieve intuitive interaction and thus to favor user acceptance, the gesture interface should be conform to user expectation and enable the users to apply their prior knowledge. This particularly concerns the gestures used for input. The conducted experiment investigates which gestures subjects tend to use for various functions of a truck and how these gestures are affected by the subjects’ prior knowledge. In total, 17 potential functions were considered for this purpose. Within the experiment, 74 subjects performed gestures for each of these functions while being recorded on video. The video data shows a variety of gestures differing in hand pose, execution space, and palm orientation. Nevertheless, several interindividual similarities in gesturing can be observed, which made it possible to analyze the gestures in terms of the prior knowledge applied. The results show that gestures differ according to the sources of prior knowledge like culture and instincts. Depending on the function, the gestures observed within the experiment are based on gestures of quasi-direct manipulation, emblematic gestures, instinctive gestures, standardized gestures and gestures expressing the users’ mental model. However, the applicability of these gestures is limited by capabilities of gesture recognition and is depending on how the user interface will be designed

Mapping the aerosol over Eurasia from the Zotino Tall Tower

The present study covers more than 5 yr corresponding to more than 40 000 hours of particle and gas data measured at the Siberian tall tower Zotino Tall Tower (ZOTTO) (60.8%26deg%3BN; 89.35%26deg%3BE). Extrapolated along 10-d back trajectories, the ZOTTO measurements cover large parts of the Eurasian land mass. Mapping the extrapolated ZOTTO data points to major anthropogenic source regions and Siberian fire regions, consistent with emission data for CO and vegetation fires. Middle East mid-latitude sources stand out strongly and possibly emissions from Northern China may be seen at times from ZOTTO. The maps of measured light scattering and absorption characteristics support the interpretation of different source types. Three clusters of substantially different submicrometer particle size distributions were found, the maps of which also could be related to major aerosol source regions