Entanglement and bifurcations in Jahn-Teller models

We compare and contrast the entanglement in the ground state of two Jahn-Teller models. The $E\otimes\beta$ system models the coupling of a two-level electronic system, or qubit, to a single oscillator mode, while the $E\otimes\epsilon$ models the qubit coupled to two independent, degenerate oscillator modes. In the absence of a transverse magnetic field applied to the qubit, both systems exhibit a degenerate ground state. Whereas there always exists a completely separable ground state in the $E\otimes\beta$ system, the ground states of the $E\otimes\epsilon$ model always exhibit entanglement. For the $E\otimes\beta$ case we aim to clarify results from previous work, alluding to a link between the ground state entanglement characteristics and a bifurcation of a fixed point in the classical analogue. In the $E\otimes\epsilon$ case we make use of an ansatz for the ground state. We compare this ansatz to exact numerical calculations and use it to investigate how the entanglement is shared between the three system degrees of freedom.Comment: 11 pages, 9 figures, comments welcome; 2 references adde

Aircraft requirements for low/medium density markets

A study was conducted to determine the demand for and the economic factors involved in air transportation in a low and medium density market. The subjects investigated are as follows: (1) industry and market structure, (2) aircraft analysis, (3) economic analysis, (4) field surveys, and (5) computer network analysis. Graphs are included to show the economic requirements and the aircraft performance characteristics

The stability of modified gravity models

Conditions for the existence and stability of de Sitter space in modified gravity are derived by considering inhomogeneous perturbations in a gauge-invariant formalism. The stability condition coincides with the corresponding condition for stability with respect to homogeneous perturbations, while this is not the case in scalar-tensor gravity. The stability criterion is applied to various modified gravity models of the early and the present universe.Comment: 22 pages, LaTeX, to appear in Phys. Rev.

Photonic Clusters

We show through rigorous calculations that dielectric microspheres can be organized by an incident electromagnetic plane wave into stable cluster configurations, which we call photonic molecules. The long-range optical binding force arises from multiple scattering between the spheres. A photonic molecule can exhibit a multiplicity of distinct geometries, including quasicrystal-like configurations, with exotic dynamics. Linear stability analysis and dynamical simulations show that the equilibrium configurations can correspond with either stable or a type of quasi-stable states exhibiting periodic particle motion in the presence of frictional dissipation.Comment: 4 pages, 3 figure

Who are you talking to? The role of addressee identity in utterance comprehension

Issue online: 30 March 2020Experimental evidence suggests that speaker and addressee quickly adapt to each other from the earliest moments of sentence processing, and that interlocutor-related information is rapidly integrated with other sources of nonpragmatic information (e.g., semantic, morphosyntactic, etc.). These findings have been taken as support for one-step models of sentence comprehension. The results from the present eventrelated potential study challenge this theoretical framework providing a case where discourse level information is integrated only at a late stage of processing, when morphosyntactic analysis has been already initiated. We considered the case of Basque allocutive agreement, where information about addressee gender is encoded in verbal inflection. Two different types of Basque grammatical violations were presented together with the corresponding control conditions: one could be detected based on a morphosyntactic mismatch (person agreement violation), while the other could be detected only if the addressee's gender was considered (allocutive violation). Morphosyntactic violations elicited greater N400 effects followed by P600 effects, while allocutive violations elicited only P600 effects. These results provide new constraints to one-step accounts as they represent a case where speakers do not immediately adjust to the addressee's perspective. We propose that the relevance of discourse-level information might be a crucial variable to reconcile the dichotomy between one- and two-step models.Horizon 2020 Framework Programme, Grant/Award Number: H2020-MSCAIF- 2018-837228; Fundación BBVA, Grant/ Award Number: IN[18]_HMS_LIN_0058; Ministerio de Economía y Competitividad, Grant/Award Number: IJCI-2016-27702, PSI2014-54500, RYC 2017-22015 and SEV-2015-490; Eusko Jaurlaritza, Grant/ Award Number: PI_2015_1_25; Gipuzkoa Fellowship Program, Grant/Award Number: FFI2016-76432-P. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 83722

A minimal model for chaotic shear banding in shear-thickening fluids

We present a minimal model for spatiotemporal oscillation and rheochaos in shear-thickening complex fluids at zero Reynolds number. In the model, a tendency towards inhomogeneous flows in the form of shear bands combines with a slow structural dynamics, modelled by delayed stress relaxation. Using Fourier-space numerics, we study the nonequilibrium `phase diagram' of the fluid as a function of a steady mean (spatially averaged) stress, and of the relaxation time for structural relaxation. We find several distinct regions of periodic behavior (oscillating bands, travelling bands, and more complex oscillations) and also regions of spatiotemporal rheochaos. A low-dimensional truncation of the model retains the important physical features of the full model (including rheochaos) despite the suppression of sharply defined interfaces between shear bands. Our model maps onto the FitzHugh-Nagumo model for neural network dynamics, with an unusual form of long-range coupling.Comment: Revised version (in particular, new section III.E. and Appendix A

Auto-regressive moving average analysis of linear and discontinuous models of human balance during quiet standing

Linear Time Invariant (LTI) processes can be modelled by means of Auto-Regressive Moving Average (ARMA) model systems. In this paper, we examine whether an ARMA model can be fitted to a process characterised by switched nonlinearities. In particular, we conduct the following test: we generate data from known LTI and nonlinear (threshold/dead-zone) models of human balance and analyse the output using ARMA. We show that both these known systems can be fitted, according to standard criteria, with low order ARMA models. To check if there are some obvious effects of the dead-zone, we compare the power spectra of both systems with the power spectra of their ARMA models. We then examine spectral properties of three posturographic data sets and their ARMA models and compare them with the power spectra of our model systems. Finally, we examine the dynamics of our model systems in the absence of noise to determine what is the effect of the switching threshold (dead-zone) on the asymptotic dynamics

Generation And Transmission Systems For Wave Power: A Feasibility Study

Following his recommendation to WESC, Dr. J.K. Wright was asked to approach GEC, Joseph Lucas and IRD with a view to seeking their support in assessing the technical feasibility and cost of converting wave energy, available in some mechanical form at the output of a device (WEC), to a more usable form for consumption on the UK mainland. At this time it was anticipated that this usable form would be electricity which would be fed into the CEGB/Scottish Boards grid network but it was also agreed that other energy forms were to be included. Early agreement by the companies on the desirability of such a study and discussions on how it might proceed led to the proposal 'Getting the Power to Shore' (1). The overall objectives of the study were agreed as (i) to identify and assess possible energy conversion and transmission system; (ii) estimate the performance and cost of the more promising systems and make a first order assessment of the impact of the operational and performance characteristics of particular designs on the overall economics of WEC systems; (iii) provide design information for the device teams developing particular WECs - both through independent studies and by way of consultancies; (iv) estimate the timescales and the R & D effort required to implement particular designs. The very large number of possible routes, the unfamiliar characteristics of the energy supply and the 'fluid' state of the thinking of the device teams were all factors which led TAG 6 to propose a preliminary, 9 month, 'broad brush' study as a necessary precursor to a detailed study of preferred systems. It is this preliminary study which is the subject of the present report. The succeeding sections of the report set out the specific objectives of the preliminary survey, set out the system options, discuss the assumptions which have been made in relation to wave and device properties and then discuss specific elements of the possible systems. The final sections relate these generic considerations to specific device designs and describe the preferred systems, ranked in order of technical 'credibility' and cost, which TAG 6 believe should be examined in greater detail during the second stage of its phase I study. Frequent reference is made to the working papers which have been prepared in the course of this study (a total of more than sixty are listed in Appendix III). It goes without saying that these papers are available for examination by anyone who wishes to obtain background information and supporting technical detail but the reader is asked to note that these are working papers and do not necessarily represent the present views of TAG 6. It would be surprising if detailed studies during stage II, when better information is available from device teams and the other TAGs, do not give rise to further shifts of emphasis

Potential For Power: A Symposium On The Prospects For Power From Currently Unconventional Energy Sources

The wave energy arriving on the west coast of the United Kingdom represents a very substantial energy resource, amounting on average to more than twice the present installed capacity of the CEGB. Recent, comprehensive, studies by the CEGB (1) (2) and the National Engineering Laboratory (3) suggest that although there is no obvious technical reason for being unable ultimately to harness much of this energy, and many methods have been proposed, there are still considerable uncertainties over the choice of wave power system and its economics. Wave power does show sufficient promise however to have been made the subject of serious studies supported by the CEGB and the Department of Energy (4). In this Paper the potential of wave power and some of the more promising methods of harnessing it are discussed, together with an appreciation of some of the many technical and engineering problems which still need to be examined, and a discussion of the impact of wave power on the environment. By considering the results of recent research and their impact on wave power economics it is argued that wave power could be exploited to conserve fossil fuels but is unlikely to be competitive with nuclear power