Indigenous Rights and Intellectual Property Law: A Comparison of the United States and Australia

Quantum Physics has many concepts that are hard to conceive. The main goal with this project is to explain and demonstrate some of these. To achieve this, a setup has been built where a beam is split into two paths, which then subsequently coincide on a mutual screen. If we choose to deny ourselves the possibility of determining which path the wave takes, the paths are said to be indistinguishable. In this case the waves from the two dierent paths will interfere, which will be seen as a periodic interference pattern on the screen. If we instead choose to do a measurement in such a way that we know which path the wave took, the paths are distinguishable. As this occurs, the interference pattern will disappear. There is also a third possibility. The third possibility is to leave the opportunity of measuring, but not actually doing it. This alternative gives the same result as if the path was actually determined, the interference pattern will disappear. In this setup the wavefront is split into two by a thin metal wire. On each side is a polarisation lter with perpendicular polarisation with respect to one another. These lters help us to distinguish the two possible paths. By placing a third polariser between the wire and the screen, parallel to one of the earlier polarisers, it can be seen which path the light has taken, making the paths distinguishable. If the third polariser is instead rotated at a 45o-angle letting through equal parts of both paths, the passing light will have a mutual direction of polarisation. This will once again make the light indistinguishable and the interference pattern will reappear.Kvantfysiken har många svårbegripliga koncept. Målet med detta projekt är att förklara och demonstrera vissa av dessa. För att uppnå detta har en uppställning byggts där en ljusstråle delas upp och får utbredas längs två olika vägar. Vägen kan kodas på de respektive vägarna med hjälp av polarisationslter. Därefter låter man ljuset som tog de två vägarna sammanfalla på en gemensam skärm. Om vi väljer att avsäga oss möjligheten att avgöra vilken väg ljuset tar, sägs ljuset som tog respektive väg icke-särskiljbart. I detta fall kommer vågorna från de två olika banorna interferera, vilket syns som ett mönster på skärmen. Däremot om vi väljer att mäta vilken bana vågen tar är banorna särskiljbara. När vi gör detta val försvinner interferensm önstret. Det nns även ett tredje alternativ. Det alternativet är att skapa en möjlighet att mäta, men inte utnyttja den. Detta fall ger samma resultat som att faktiskt mäta, det vill säga interferens- 3 mönstret försvinner. I vår uppställning delas vågfronten upp i två delar med hjälp av en metalltr åd. På vardera sida om tråden sitter polariseringslter med vinkelr äta polarisationsriktningar i förhållande till varandra. Med hjälp av dessa kan vägarna särskiljas. Genom att sätta ett tredje polarisations- lter mellan metalltråden och skärmen parallellt med ett av ltren kan man bestämma vilken väg ljuset tagit, vilket gör banorna särskiljbara. Om vi däremot sätter det tredje ltret i 45o-vinkel mot de vinkelräta polarisatorerna så att ljuset från de båda vägarna återigen får samma polarisationsrikting, går det inte längre att avgöra vilken väg ljuset tagit. Alltså är vägarna nu icke-särskiljbara och interferensmönstret på skärmen återuppstår.

Probing vacuum birefringence using x-ray free electron and optical high-intensity lasers

Vacuum birefringence is one of the most striking predictions of strong field quantum electrodynamics: Probe photons traversing a strong field region can indirectly sense the applied "pump" electromagnetic field via quantum fluctuations of virtual charged particles which couple to both pump and probe fields. This coupling is sensitive to the field alignment and can effectively result in two different indices of refraction for the probe photon polarization modes giving rise to a birefringence phenomenon. In this article we perform a dedicated theoretical analysis of the proposed discovery experiment of vacuum birefringence at a x-ray free electron laser/optical high-intensity laser facility. Describing both pump and probe laser pulses realistically in terms of their macroscopic electromagnetic fields, we go beyond previous analyses by accounting for various effects not considered before in this context. Our study facilitates stringent quantitative predictions and optimizations of the signal in an actual experiment.Comment: 23 pages, 4 figure

Lack of diamagnetism and the Little-Parks effect

When a superconducting sample is submitted to a sufficiently strong external magnetic field, the superconductivity of the material is lost. In this paper we prove that this effect does not, in general, take place at a unique value of the external magnetic field strength. Indeed, for a sample in the shape of a narrow annulus the set of magnetic field strengths for which the sample is superconducting is not an interval. This is a rigorous justification of the Little-Parks effect. We also show that the same oscillation effect can happen for disc-shaped samples if the external magnetic field is non-uniform. In this case the oscillations can even occur repeatedly along arbitrarily large values of the Ginzburg--Landau parameter $\kappa$. The analysis is based on an understanding of the underlying spectral theory for a magnetic Schr\"{o}dinger operator. It is shown that the ground state energy of such an operator is not in general a monotone function of the intensity of the field, even in the limit of strong fields

Negative-resistance models for parametrically flux-pumped superconducting quantum interference devices

A Superconducting QUantum Interference Device (SQUID) modulated by a fast oscillating magnetic flux can be used as a parametric amplifier, providing gain with very little added noise. Here, we develop linearized models to describe the parametrically flux-pumped SQUID in terms of an impedance. An unpumped SQUID acts as an inductance, the Josephson inductance, whereas a flux-pumped SQUID develops an additional, parallel element which we have coined the ``pumpistor.'' Parametric gain can be understood as a result of a negative resistance of the pumpistor. In the degenerate case, the gain is sensitive to the relative phase between the pump and signal. In the nondegenerate case, gain is independent of this phase. We develop our models first for degenerate parametric pumping in the three-wave and four-wave cases, where the pump frequency is either twice or equal to the signal frequency, respectively. We then derive expressions for the nondegenerate case where the pump frequency is not a multiple of the signal frequency, where it becomes necessary to consider idler tones which develop. For the nondegenerate three-wave case, we present an intuitive picture for a parametric amplifier containing a flux-pumped SQUID where current at the signal frequency depends upon the load impedance at an idler frequency. This understanding provides insight and readily testable predictions of circuits containing flux-pumped SQUIDs.Comment: 27 pages, 6 figures, 1 tabl

Atmospheric NLTE-models for the spectroscopic analysis of blue stars with winds. IV. Porosity in physical and velocity space

[Abridged] Clumping in the radiation-driven winds of hot, massive stars affects the derivation of synthetic observables across the electromagnetic spectrum. We implement a formalism for treating wind clumping - in particular the light-leakage effects associated with a medium that is porous in physical and velocity space - into the global (photosphere+wind) NLTE model atmosphere code FASTWIND. We assume a stochastic, two-component wind consisting of a mixture of optically thick and thin clumps embedded in a rarefied inter-clump medium. We account fully for the reductions in opacity associated with porosity in physical and velocity-space, and for the well-known effect that opacities depending on rho^2 are higher in clumpy winds than in smooth ones of equal mass-loss rate. By formulating our method in terms of suitable mean and effective opacities for the clumpy wind, we are able to compute models with the same speed (~15 min. on a modern laptop) as in previous code-generations. Some first, generic results of the new models include: i) Confirming earlier results that velocity-space porosity is critical for analysis of UV wind lines in O-stars; ii) for the optical Halpha line, optically thick clumping effects are small for O-stars, but potentially very important for late B and A-supergiants; iii) spatial porosity is a marginal effect for absorption of high-energy X-rays in O-stars, as long as the mean-free path between clumps are kept at realistic values; iv) porosity is negligible at typical O-star radio-photosphere radii; v) regarding the wind ionization balance, a general trend is that increased rates of recombination in simulations with optically thin clumps lead to overall lower degrees of ionization than in corresponding smooth models, but that this effect now is counteracted by the increased levels of light-leakage associated with porosity in physical and velocity space.Comment: 12 pages, 5 figures, accepted for publication in Astronomy & Astrophysic