8,272 research outputs found
Book Review: "Quantum Theory as an Emergent Phenomenon", by Stephen L. Adler
This is a book review of the book: "Quantum Theory as an Emergent
Phenomenon", by Stephen L. Adler (Cambridge University Press - 2004)Comment: 3 pages, LaTe
Collapse models: from theoretical foundations to experimental verifications
The basic strategy underlying models of spontaneous wave function collapse
(collapse models) is to modify the Schroedinger equation by including nonlinear
stochastic terms, which tend to localize wave functions in space in a dynamical
manner. These terms have negligible effects on microscopic systems-therefore
their quantum behaviour is practically preserved. On the other end, since the
strength of these new terms scales with the mass of the system, they become
dominant at the macroscopic level, making sure that wave functions of
macro-objects are always well-localized in space. We will review these basic
features. By changing the dynamics of quantum systems, collapse models make
predictions, which are different from standard quantum mechanical predictions.
Although they are difficult to detect, we discuss the most relevant scenarios,
where such deviations can be observedComment: 10 Pages. Invited Talk at the Heinz von Foerster Centenary
International Conference on Self-Organization and Emergence: Emergent Quantum
Mechanics (EmerQuM11). Nov. 10-13, 2011, Vienna, Austria. Proceedings to
appear in J. Phys. (Conf. Series
Dynamical Reduction Models: present status and future developments
We review the major achievements of the dynamical reduction program, showing
why and how it provides a unified, consistent description of physical
phenomena, from the microscopic quantum domain to the macroscopic classical
one. We discuss the difficulties in generalizing the existing models in order
to comprise also relativistic quantum field theories. We point out possible
future lines of research, ranging from mathematical physics to phenomenology.Comment: 12 pages. Contribution to the Proceedings of the "Third International
Workshop DICE2006", Castello di Piombino (Tuscany), September 11-15, 2006.
Minor changes mad
On the Electromagnetic Properties of Matter in Collapse Models
We discuss the electromagnetic properties of both a charged free particle,
and a charged particle bounded by an harmonic potential, within collapse
models. By choosing a particularly simple, yet physically relevant, collapse
model, and under only the dipole approximation, we are able to solve the
equation of motion exactly. In this way, both the finite time and large time
behavior can be analyzed accurately. We discovered new features, which did not
appear in previous works on the same subject. Since, so far, the spontaneous
photon emission process places the strongest upper bounds on the collapse
parameters, our results call for a further analysis of this process for those
atomic systems which can be employed in experimental tests of collapse models,
as well as of quantum mechanics.Comment: 17 pages, LaTeX, updated version with minor change
On the spontaneous emission of electromagnetic radiation in the CSL model
Spontaneous photon emission in the Continuous Spontaneous Localization (CSL)
model is studied one more time. In the CSL model each particle interacts with a
noise field that induces the collapse of its wave function. As a consequence of
this interaction, when the particle is electrically charged, it radiates. As
discussed in [1], the formula for the emission rate, to first perturbative
order, contains two terms: One is proportional to the Fourier component of the
noise field at the same frequency as that of the emitted photon and one is
proportional to the zero Fourier component of the noise field. As discussed in
previous works, this second term seems unphysical. In [1], it was shown that
the unphysical term disappears when the noises is confined to a bounded region
and the final particle's state is a wave packet. Here we investigate the origin
of the unphysical term and why it vanishes according to the previous
prescription. For this purpose, the electrodynamic part of the equation of
motion is solved exactly while the part due to the noise is treated
perturbatively. We show that the unphysical term is connected to exponentially
decaying function of time which dies out in the large time limit, however,
approximates to 1 in the first perturbative order in the electromagnetic field.Comment: 10 pages, 1 figure, LaTe
The quantum theory of measurement within dynamical reduction models
We analyze in mathematical detail, within the framework of the QMUPL model of
spontaneous wave function collapse, the von Neumann measurement scheme for the
measurement of a 1/2 spin particle. We prove that, according to the equation of
the model: i) throughout the whole measurement process, the pointer of the
measuring device is always perfectly well localized in space; ii) the
probabilities for the possible outcomes are distributed in agreement with the
Born probability rule; iii) at the end of the measurement the state of the
microscopic system has collapsed to the eigenstate corresponding to the
measured eigenvalue. This analysis shows rigorously how dynamical reduction
models provide a consistent solution to the measurement problem of quantum
mechanics.Comment: 24 pages, RevTeX. Minor changes mad
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