Charge noise at Cooper-pair resonances

We analyze the charge dynamics of a superconducting single-electron transistor (SSET) in the regime where charge transport occurs via Cooper-pair resonances. Using an approximate description of the system Hamiltonian, in terms of a series of resonant doublets, we derive a Born-Markov master equation describing the dynamics of the SSET. The average current displays sharp peaks at the Cooper-pair resonances and we find that the charge noise spectrum has a characteristic structure which consists of a series of asymmetric triplets of peaks. The strongest feature in the charge noise spectrum is the triplet of peaks centered at zero frequency which has a peak spacing equal to the level separation within the doublets and is similar to the triplet in the spectrum of a driven, damped, two-level system. We also explore the back-action that the SSET charge noise would have on an oscillator coupled to the island charge, measurement of which provides a way of probing the charge noise spectrum.Comment: 14 pages, 7 figure

A review of British Upper Jurassic ichthyosaurs

PhD ThesisThe introduction to the thesis presents a synopsis of British Jurassic stratigraphy, and a brief account of the occurrence of British Upper Jurassic ichthyosaur remains which highlights the importance of the Leeds Collection of ichthyosaurs. A historical review of the publications concerning British Upper Jurassic ichthyosaurs (members of the order Ichthyopterygia) is presented. The British Upper Jurassic ichthyosaur taxa are reviewed. Of the five genera and fourteen species erected, only four generic and four specific names are found to be valid. The rejected names are listed with reasons for their rejection. After a listing and discussion of the synonymy of each valid species, a diagnosis and list of referable material is presented, then each species is described in detail. New reconstructions of the skull in dorsal and lateral views, the palate, the lower jaw and the complete skeleton of Ophthalmosaurus icenicus are presented. A reinterpretation of the forepaddle of O. icenicus proposes that previous interpretations have presented the forepaddle laterally inverted. The discovery that a bone of uncertain homology, designated element B, is present in the temporal region of the skull of O. icenicus, has important implications in the problem of the phylogeny and affinities of the Ichthyopterygia, and this is discussed. The presence of element B in the skull, which has been denied by previous authors, leads to the proposal of two alternative hypotheses concerning the relationships of the Ichthyopterygia to other reptiles. The preferred hypothesis is one that states that element B is a neomorph, and that the Ichthyopterygia are diapsid derivatives. A critique of previous schemes of classification of the Ichthyopterygia is presented, and a new classification is proposed. The validity of the division of the Ichthyopterygia into two groups, the latipinnates and longipinnates, is questioned. Finally, a discussion of functional aspects of the anatomy of O. icenicus is presented

Castells, 'Murdochization', Economic Counterpower and Livestreaming

In his Information Age trilogy, Manuel Castells documents the transformation of economic power by means of network affordances. In more recent work, he has built an account of the linking of economic power with cultural and political power through ‘Murdochization’ or ‘the networking of networks’. Whilst Castells’ account of power has thus developed to acknowledge the integration of economic, cultural and political interests within networks, his account of ‘counterpower’ remains largely focused on cultural and political resistance in the form of protest. Here we explore a case of economic counterpower, the unauthorized livestreaming of digital sports broadcasts. Analysis of this particular case (of counterpower) is particularly significant, given the centrality of Murdochization in Castells’ account of power in the network society. Emerging out of, alongside, and in response to the growth of, Murdochized digital media sports networks, we explore the scope and limits of livestreaming as a form of economic counterpower and counter-Murdochization. In this article, we document Castells’ theory of network power, the centrality of Murdochization to that account, and the centrality of monopoly control over digital sports broadcasting to Murdochized media empires. The scope and resilience of alternative streaming media in switching live sports programming from pay to view to free sharing is then examined. The failure to date of all attempts to prohibit free streams shows the ongoing viability of such economic counterpower. However, whilst dominant actors cannot eliminate economic counterpower, where dominant actors choose not to broadcast, no switching of content can take place

Castells, ‘Murdochisation’, Economic Counterpower and Live-Streaming

In his Information Age trilogy, Manuel Castells documents the transformation of economic power by means of network affordances. In more recent work, he has built an account of the linking of economic power with cultural and political power through 'Murdochisation', or 'the networking of networks'. Whilst Castells’ account of power has thus developed to acknowledge the integration of economic, cultural and political interests and networks, his account of 'counterpower' remains largely focussed on cultural and political resistance in the form of protest. Here we explore a case of economic counterpower; the unauthorised live-streaming of digital sports broadcasts. Analysis of this particular case (of counterpower) is particularly significant given the centrality of ‘Murdochisation’ in Castells’ account of power in the network society. Emerging out of, alongside, and in response to the growth of Murdochised digital media sports networks, we explore the scope and limits of live-streaming as a form of economic counterpower and counter-Murdochisation. In this article, we document Castells’ theory of network power, the centrality of ‘Murdochisation’ to that account, and the centrality of monopoly control over digital sports broadcasting to Murdochised media empires. The scope and resilience of alternative streaming media in switching live sports programming from pay to view to free sharing is then examined. The failure to date of all attempts to prohibit free streams shows the on-going viability of such economic counterpower. However, whilst dominant actors cannot eliminate economic counterpower, where dominant actors choose not to broadcast, no switching of content can take place

Universal Behavior of the Resistance Noise across the Metal-Insulator Transition in Silicon Inversion Layers

Studies of low-frequency resistance noise show that the glassy freezing of the two-dimensional (2D) electron system in the vicinity of the metal-insulator transition occurs in all Si inversion layers. The size of the metallic glass phase, which separates the 2D metal and the (glassy) insulator, depends strongly on disorder, becoming extremely small in high-mobility samples. The behavior of the second spectrum, an important fourth-order noise statistic, indicates the presence of long-range correlations between fluctuators in the glassy phase, consistent with the hierarchical picture of glassy dynamics.Comment: revtex4; 4+ pages, 5 figure

Bath induced coherence and the secular approximation

Finding efficient descriptions of how an environment affects a collection of discrete quantum systems would lead to new insights into many areas of modern physics. Markovian, or time-local, methods work well for individual systems, but for groups a question arises: does system-bath or inter-system coupling dominate the dissipative dynamics? The answer has profound consequences for the long-time quantum correlations within the system. We consider two bosonic modes coupled to a bath. By comparing an exact solution to different Markovian master equations, we find that a smooth crossover of the equations-of-motion between dominant inter-system and system-bath coupling exists - but requires a non-secular master equation. We predict a singular behaviour of the dynamics, and show that the ultimate failure of non-secular equations of motion is essentially a failure of the Markov approximation. Our findings justify the use of time-local theories throughout the crossover between system-bath dominated and inter-system-coupling dominated dynamics.PostprintPeer reviewe