93 research outputs found
Two-particle interference in standard and Bohmian quantum mechanics
The compatibility of standard and Bohmian quantum mechanics has recently been
challenged in the context of two-particle interference, both from a theoretical
and an experimental point of view. We analyze different setups proposed and
derive corresponding exact forms for Bohmian equations of motion. The equations
are then solved numerically, and shown to reproduce standard quantum-mechanical
results.Comment: Minor corrections, 2 references added, version to appear in J. Phys.
On the zig-zag pilot-wave approach for fermions
We consider a pilot-wave approach for the Dirac theory that was recently
proposed by Colin and Wiseman. In this approach, the particles perform a
zig-zag motion, due to stochastic jumps of their velocity. We respectively
discuss the one-particle theory, the many-particle theory and possible
extensions to quantum field theory. We also discuss the non-relativistic limit
of the one-particle theory. For a single particle, the motion is always
luminal, a feature that persists in the non-relativistic limit. For more than
one particle the motion is in general subluminal.Comment: 23 pages, no figures, LaTe
\Lambda-buildings and base change functors
We prove an analog of the base change functor of \Lambda-trees in the setting
of generalized affine buildings. The proof is mainly based on local and global
combinatorics of the associated spherical buildings. As an application we
obtain that the class of generalized affine building is closed under ultracones
and asymptotic cones. Other applications involve a complex of groups
decompositions and fixed point theorems for certain classes of generalized
affine buildings.Comment: revised version, 29 pages, to appear in Geom. Dedicat
A Dirac sea pilot-wave model for quantum field theory
We present a pilot-wave model for quantum field theory in which the Dirac sea
is taken seriously. The model ascribes particle trajectories to all the
fermions, including the fermions filling the Dirac sea. The model is
deterministic and applies to the regime in which fermion number is
superselected. This work is a further elaboration of work by Colin, in which a
Dirac sea pilot-wave model is presented for quantum electrodynamics. We extend
his work to non-electromagnetic interactions, we discuss a cut-off
regularization of the pilot-wave model and study how it reproduces the standard
quantum predictions. The Dirac sea pilot-wave model can be seen as a possible
continuum generalization of a lattice model by Bell. It can also be seen as a
development and generalization of the ideas by Bohm, Hiley and Kaloyerou, who
also suggested the use of the Dirac sea for the development of a pilot-wave
model for quantum electrodynamics.Comment: 41 pages, no figures, LaTex, v2 minor improvements and addition
The measurement of collaborative culture in secondary schools: An informal subgroup approach
Research on teacher collaboration underlines the importance of a collaborative culture for teachers’ functioning. However, while scholars usually regard collaborative culture as a school team characteristic, this study argues that subgroups may be more meaningful units of analysis to conceptualize and assess teachers’ perceptions of collaborative culture. Based on the assumption that collaborative culture is developed, expressed, and maintained in frequent work-related interactions, this study hypothesizes that collaborative culture is not homogenously spread over the school but rather varies between informal subgroups. Data from 760 Flemish teachers were examined using social network analysis and consensus analyses. The results provided evidence that perceptions on collaborative culture are more homogeneous within informal subgroups that are characterized by frequent interactions than the entire school team. This finding stresses the importance of assessing the meaningful unit of analysis for collective-level and socially-constructed concepts, such as collaborative culture. Moreover, the benefits and potential of a social network approach to identify (socially stable) subunits within the school team are illustrated
Causal Loop Quantum Gravity and Cosmological Solutions
We shall present here the causal interpretation of canonical quantum gravity
in terms of new variables. Then we shall apply it to the minisuperspace of
cosmology. A vacuum solution of quantum cosmology is obtained and the Bohmian
trajectory is investigated. At the end a coherent state with matter is
considered in the cosmological model.Comment: 22 pages, 6 figure
A first experimental test of de Broglie-Bohm theory against standard quantum mechanics
De Broglie - Bohm (dBB) theory is a deterministic theory, built for
reproducing almost all Quantum Mechanics (QM) predictions, where position plays
the role of a hidden variable. It was recently shown that different coincidence
patterns are predicted by QM and dBB when a double slit experiment is realised
under specific conditions and, therefore, an experiment can test the two
theories. In this letter we present the first realisation of such a double slit
experiment by using correlated photons produced in type I Parametric Down
Conversion. Our results confirm QM contradicting dBB predictions
The "Unromantic Pictures" of Quantum Theory
I am concerned with two views of quantum mechanics that John S. Bell called
``unromantic'': spontaneous wave function collapse and Bohmian mechanics. I
discuss some of their merits and report about recent progress concerning
extensions to quantum field theory and relativity. In the last section, I
speculate about an extension of Bohmian mechanics to quantum gravity.Comment: 37 pages LaTeX, no figures; written for special volume of J. Phys. A
in honor of G.C. Ghirard
Bohmian approach to spin-dependent time of arrival for particles in a uniform field and for particles passing through a barrier
It is known that Lorentz covariance fixes uniquely the current and the
associated guidance law in the trajectory interpretation of quantum mechanics
for spin-1/2 particles. In the nonrelativistic domain this implies a guidance
law for electrons which differs by an additional spin-dependent term from the
one originally proposed by de Broglie and Bohm. Although the additional term in
the guidance equation may not be detectable in the quantum measurements derived
solely from the probability density , it plays a role in the case of
arrival-time measurements. In this paper we compute the arrival time
distribution and the mean arrival time at a given location, with and without
the spin contribution, for two problems: 1) a symmetrical Gaussian packet in a
uniform field and 2) a symmetrical Gaussian packet passing through a 1D
barrier. Using the Runge-Kutta method for integration of the guidance law,
Bohmian paths of these problems are also computed
Experimental tests of hidden variable theories from dBB to Stochastic Electrodynamics
In this paper we present some of our experimental results on testing hidden
variable theories, which range from Bell inequalities measurements to a
conclusive test of stochastic electrodynamics
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