209 research outputs found

    Quantum mechanics: A new chapter?

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    We review the conceptual problems in quantum mechanics on a fundamental level. It is shown that the proposed model of extended electrons and a clear understanding of rotations in three dimensional space solve a large part of these problems, in particular the problems related to the ontological status and physical meaning of wavefunctions. It also solves the problem of non-locality. The experimental results obtained in Yves Couder's group and theoretical results by Gerdard Gr\"ossing indicate that the wave-like distribution of trajectories of electrons in interference experiments are most likely due to the quantized interactions leading to a discrete set of transferred momenta. A separate experimental confirmation of this interpretation for double-slit interferometry of photons has been given by the group of Steinberg.Comment: 8 pages, article to appear in the Proceedings of the 6th Conference: Quantum Theory: Reconsideration of Foundations, June 11-14 2012 in Vaexjoe, Swede

    Theoretical study of the role of the tip in enhancing the sensitivity of differential conductance tunneling spectroscopy on magnetic surfaces

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    Based on a simple model for spin-polarized scanning tunneling spectroscopy (SP-STS) we study how tip magnetization and electronic structure affects the differential conductance (dI/dV) tunneling spectrum of an Fe(001) surface. We take into account energy dependence of the vacuum decay of electron states, and tip electronic structure either using an ideal model or based on ab initio electronic structure calculation. In the STS approach, topographic and magnetic contributions to dI/dV can clearly be distinguished and analyzed separately. Our results suggest that the sensitivity of STS on a magnetic sample can be tuned and even enhanced by choosing the appropriate magnetic tip and bias setpoint, and the effect is governed by the effective spin-polarization.Comment: 22 pages manuscript, 4 figures; http://link.aps.org/doi/10.1103/PhysRevB.83.21441

    Simulation of spin-polarized scanning tunneling microscopy on complex magnetic surfaces: Case of a Cr monolayer on Ag(111)

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    We propose an atom-superposition-based method for simulating spin-polarized scanning tunneling microscopy (SP-STM) from first principles. Our approach provides bias dependent STM images in high spatial resolution, with the capability of using either constant current or constant height modes of STM. In addition, topographic and magnetic contributions can clearly be distinguished, which are directly comparable to results of SP-STM experiments in the differential magnetic mode. Advantages of the proposed method are that it is computationally cheap, it is easy to parallelize, and it can employ the results of any ab initio electronic structure code. Its capabilities are illustrated for the prototype frustrated hexagonal antiferromagnetic system, Cr monolayer on Ag(111) in a noncollinear magnetic 120∘120^{\circ} N\'eel state. We show evidence that the magnetic contrast is sensitive to the tip electronic structure, and this contrast can be reversed depending on the bias voltage.Comment: 28 pages manuscript, 1 table, 5 figure

    Is quantum mechanics creationism, and not science?

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    I revisit the reply of Bohr to Einstein. Bohr's assertion that there are no causes in atomic scale systems is, as a closer analysis reveals, not in line with the Copenhagen interpretation since it would contain a statement about reality. What Bohr should have written is that there are no causes in mathematics, which is universally acknowledged. The law of causality requires physical effects to be due to physical causes. For this reason any theoretical model which replaces physical causes by mathematical objects is creationism, that is, it creates physical objects out of mathematical elements. I show that this is the case for most of quantum mechanics.Comment: 8 pages, no in-depth knowledge of mathematics required, sets out the case for a major revision of theoretical physics. This revision expands the case against Bohm and the analysis whether quantum mechanics actually meets Popper's requirement for a scientific theory (it does not, since it is not falsifiable) and corrects a few typo
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