Why special relativity should not be a template for a fundamental reformulation of quantum mechanics

In a comparison of the principles of special relativity and of quantum mechanics, the former theory is marked by its relative economy and apparent explanatory simplicity. A number of theorists have thus been led to search for a small number of postulates - essentially information theoretic in nature - that would play the role in quantum mechanics that the relativity principle and the light postulate jointly play in Einstein's 1905 special relativity theory. The purpose of the present paper is to resist this idea, at least in so far as it is supposed to reveal the fundamental form of the theory. It is argued that the methodology of Einstein's 1905 theory represents a victory of pragmatism over explanatory depth; and that its adoption only made sense in the context of the chaotic state state of physics at the start of the 20th century - as Einstein well knew

Proper and Improper Separability

The distinction between proper and improper mixtures is a staple of the discussion of foundational questions in quantum mechanics. Here we note an analogous distinction in the context of the theory of entanglement. The terminology of `proper' versus `improper' separability is proposed to mark the distinction.Comment: 10 pages, LaTex, uses amsmath, 2 .eps figures. v2 additional figure; and reference and footnote to Seevinck and Uffink (2001). To appear in International Journal of Quantum Informatio

Learning the Right Lessons from Iraq

Foreign policy experts and policy analysts are misreading the lessons of Iraq. The emerging conventional wisdom holds that success could have been achieved in Iraq with more troops, more cooperation among U.S. government agencies, and better counterinsurgency doctrine. To analysts who share these views, Iraq is not an example of what not to do but of how not to do it. Their policy proposals aim to reform the national security bureaucracy so that we will get it right the next time. The near-consensus view is wrong and dangerous. What Iraq demonstrates is a need for a new national security strategy, not better tactics and tools to serve the current one. By insisting that Iraq was ours to remake were it not for the Bush administration's mismanagement, we ignore the limits on our power that the war exposes and in the process risk repeating our mistake. The popular contention that the Bush administration's failures and errors in judgment can be attributed to poor planning is also false. There was ample planning for the war, but it conflicted with the Bush administration's expectations. To the extent that planning failed, therefore, the lesson to draw is not that the United States national security establishment needs better planning, but that it needs better leaders. That problem is solved by elections, not bureaucratic tinkering. The military gives us the power to conquer foreign countries, but not the power to run them. Because there are few good reasons to take on missions meant to resuscitate failed governments, terrorism notwithstanding, the most important lesson from the war in Iraq should be a newfound appreciation for the limits of our power

Electron Dynamics in High-Intensity Laser Fields

Access to the full-text thesis is no longer available at the author's request, due to 3rd party copyright restrictions. Access removed on 28.11.2016 by CS (TIS).Metadata merged with duplicate record (http://hdl.handle.net/10026.1/1627) on 20.12.2016 by CS (TIS).We consider electron dynamics in strong electromagnetic fields, such as those expected from the next generation of high-intensity laser facilities. Beginning with a review of constant classical fields, we demonstrate that the electron motion (as given by the Lorentz force equation) can be divided into one of four Lorentz invariant cases. Parameterising the field tensor in terms of a null tetrad, we calculate the radiative energy spectrum for an electron in crossed fields. Progressing to an infinite plane wave, we demonstrate how the electron orbit in the average rest frame changes from figure-of-eight to circular as the polarisation changes from linear to circular. To move beyond a plane wave one must resort to numerics. We therefore present a novel numerical formulation for solving the Lorentz equation. Our scheme is manifestly covariant and valid for arbitrary electromagnetic field configurations. Finally, we reconsider the case of an infinite plane wave from a strong field QED perspective. At high intensities we predict a substantial redshift of the usual kinematic Compton edge of the photon emission spectrum, caused by the large, intensity dependent effective mass of the electrons inside the laser beam. In addition, we find that the notion of a centre-of-mass frame for a given harmonic becomes intensity dependent

Silicon-on-insulator waveguide structures for electro-optic applications

Silicon based photonic devices have been demonstrated by industrial leaders in the microelectronic industry. The need for system integration has pushed the development of silicon as a photonic material to new levels. This report presents details on a silicon-on-insulator waveguide structure based on a metal Bragg reflection diffraction grating, which utilizes a change in refractive index caused by a carrier change to induce optical modulation. The motivation of the device was for use as an electrically controlled optical modulator operating in the near infrared region; an optically controlled device has been demonstrated in previous work. This study has thoroughly examined the process development and electrical characteristics of the device through use of Silvaco(TM) simulation software and experimentation. The device has exhibited excellent optical characteristics and has shown promise as an optical modulator and a sub-bandgap photon detector. A silicon-on-insulator waveguide structure specified to operate at a wavelength of 1053nm has been simulated, designed, fabricated and tested both optically and electrically. Future iterations have been simulated and designed to take advantage of advanced microelectronic processe

Ecological impact of entomopathogenic nematodes used to control the large pine weevil, Hylobius abietis (Coleoptera: Curculionidae)

The large pine weevil (Hylobius abietis; Coleoptera: Curculionidae) is one of the most economically damaging pests in forestry across Northern Europe. Its larvae develop in coniferous tree stumps on clearfell sites and adult weevils feed on seedlings that are replanted on these sites, causing substantial mortality. As the drive towards achieving the sustainable management of natural resources increases, biological control agents are being considered as an alternative to chemical pesticides. Though such agents have great potential for contributing towards a reduction in the ecological impact of pest insect control, they must also be investigated for any potentially damaging effects they may have in whichever context they are being employed. Entomopathogenic nematodes (EPN; Steinernema carpocapsae and Heterorhabditis downesi) are currently being inundatively applied to tree stumps on coniferous clearfell sites in the UK and Ireland as biological control agents against the large pine weevil. The aim of the laboratory and field-based experiments and field sampling of clearfell sites that were carried out for this thesis was to investigate the risks associated with this use of EPN in this setting. To this end, the persistence of EPN in soil and bark after application to clearfell sites was recorded and attempts were made to investigate the possibility of hybridisation occurring between an exotic and a native Steinernema strain. Effects of EPN on some important non-target insects on clearfell sites, the service-providing wood decomposer Rhagium bifasciatum and the pine weevil parasitoid Bracon hylobii were also assessed in laboratory and field experiments. EPN presence in soil samples collected around tree stumps on clearfell sites five months, one year and two years after application of EPN decreased significantly from year one to year two. EPN presence on all sites sampled two years post EPN application was relatively low (less than 7 % positive soil samples). A similar trend was observed for EPN persistence under the bark of stumps. No EPN at all were detected two years after application on those sites treated on a small scale by manually applying nematodes. EPN persistence appeared to be better predicted by tree stump species (which in turn is indicative of the number of pine weevils developing within them) compared to soil type. Spread of nematodes was limited mostly to a 40 cm radius around stumps and little evidence of EPN presence in untreated areas was found on any of the investigated sites. While some spread of EPN to areas adjoining two of the sites occurred, there was no evidence of establishment off-site. (Chapter III). Attempts to distinguish between an indigenous and an exotic strain of S. feltiae and their hybrid using two molecular methods (Amplified Fragment Length Polymorphism or AFLP and Restriction Fragment Length Polymorphism or RFLP) were confounded by methodological obstacles. However, RFLP analysis of the strains did indicate a high rate of intraspecific and even intrastrain variation for S. feltiae. Using this method it was also possible to tentatively identify a field-isolated Steinernema sp. as Steinernema kraussei, though two other unidentified isolates could not be assigned to a particular species (Chapter IV). The saproxylic beetle community in deadwood other than tree stumps on Irish clearfell sites appears to be dominated by the longhorn beetle Rhagium bifasciatum (Coleoptera: Cerambycidae; Fabricius 1775). Both S. carpocapsae and H. downesi invaded decomposing logs and infected all stages of this species within logs when applied directly to them. However, infection only occurred to a large extent (> 50 % of insects) if the applied dose of EPN was half that applied to tree stumps (1.8 million IJs) to control the pine weevil and infection was also significantly lower when such logs were incubated in the field rather than the laboratory. R. bifasciatum individuals were infected in all regions of logs and baiting of wood samples revealed that IJs were penetrating logs to their very centre, indicating high mobility and infectivity of IJs within this substrate. S. carpocapsae emerged in numbers of 1,000 IJs or more per week for up to eight weeks after first emergence while H. downesi emergence had effectively ceased by the fifth week. A substantial number of live S. carpocapsae IJs remained in host cadavers even after eight weeks of emergence. Infection of R. bifasciatum was also recorded on three clearfell sites to which EPN had been applied around tree stumps previously (only a single infected larva found on one of the sites). Wood samples from some of these logs contained high numbers of EPN IJs (> 6,000), suggesting that EPN were recycling within logs. However, since infection of R. bifasciatum decreased significantly as the distance between a log and treated tree stumps increased it appears that the risk to this serviceproviding non-target insect can be minimised by being as accurate as possible when applying nematodes. (Chapter V). The ectoparasitoid wasp Bracon hylobii Ratz. (Hymenoptera: Braconidae) is closely associated with the large pine weevil and may therefore be at risk if EPN are applied against the latter (eggs laid on EPN-infected host larvae do not develop to adulthood). Female wasps did not parasitise dead hosts in standard trials (small bark patch [2.25 cm2]; host either freeze-killed or killed by EPN). However, naive wasps parasitised hosts that were moribund (i.e. those that died of EPN-infection within the 24 h period they were offered to wasps) significantly less frequently than either healthy control hosts or infected hosts that survived the 24 h trial period. Experienced wasps (one egg laying experience) parasitised all of these host types with similar frequency. Behavioural observations provided no evidence of wasps locating heavily infected or dead hosts and then rejecting them. Heavily infected hosts that died within the 24 h trial period during which they were offered to wasps tended to move less than their surviving counterparts and wasp oviposition was significantly correlated with host movement and host feeding during trials. NaЇve wasps were significantly less likely to parasitise hosts that had their mandibles glued shut than those that did not (this had no effect on parasitism by experienced wasps). Thus, it is suggested that vibrations caused by these host activities were the most important cue driving host location and/or host acceptance in B. hylobii. In continuous 30 minute observation of trials in which wasps were offered a host at the centre of a large bark patch (20.25 cm2), experienced wasps spent more time close to the host when it was moving and were also significantly more likely to approach the host when it was moving, indicating a vibrotaxic response. Moreover, they only were attracted to dead hosts (freeze-killed or killed by EPN) when the bark covering them was being scratched manually from below to simulate host movement. Some experienced wasps parasitised freeze-killed and EPN-killed hosts when an artificial vibrational stimulus was added in this way and the dead host was moved about inside its chamber. B. hylobii also parasitised hosts the species is not known to be associated with, including larvae of longhorn beetle R. bifasciatum and waxmoth larvae (Galleria mellonella). These results suggest that wasp foraging behaviour, host acceptance and oviposition success is most affected by vibrational cues and that naïve wasps are less likely to locate moribund hosts that move and feed less due to infection with EPN. The risk is expected to be further mediated in a field situation where wasps are likely to encounter several hosts in one host patch and more likely to be attracted to those hosts that are healthy and producing more or stronger vibrational and volatile cues compared to moribund hosts (Chapter VI). In summary, persistence and spread of EPN after application to tree stumps on clearfell sites was low and there was no evidence of a substantial impact on non-target insects. It can therefore be concluded that the overall risks associated with the use of EPN as an inundative biological control agent against the large pine weevil are low

Raised Polysilicon Source / Drain FinFET Fabrication

The F1nFET is a novel transistor that is fabricated using silicon on insulator (SOl) technology. The body of the transistor is etched out of the top layer of silicon. The device’s polysilicon source I drain are deposited. The gate is self-aligned to the source drain. Contact cuts are made and metal is etched and patterned. The devices did not show field effect as anticipated. Analysis suggested breakdown of the gate oxide