209 research outputs found
Quantum mechanics: A new chapter?
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
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)
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 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?
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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