76 research outputs found
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
De Broglie-Bohm Guidance Equations for Arbitrary Hamiltonians
In a pilot-wave theory, an individual closed system is described by a
wavefunction and configuration . The evolution of the wavefunction
and configuration are respectively determined by the Schr\"odinger and guidance
equations. The guidance equation states that the velocity field for the
configuration is given by the quantum current divided by the density
. We present the currents and associated guidance equations for
any Hamiltonian given by a differential operator. These are derived directly
from the Schr\"odinger equation, and also as Noether currents arising from a
global phase symmetry associated with the wavefunction in configuration space.Comment: 22 pages, no figures, LaTex; v3 minor corrections; v2 minor
correction
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
Genes for the Major Structural Components of Thermotogales Species’ Togas Revealed by Proteomic and Evolutionary Analyses of OmpA and OmpB Homologs
The unifying structural characteristic of members of the bacterial order Thermotogales is their toga, an unusual cell envelope that includes a loose-fitting sheath around each cell. Only two toga-associated structural proteins have been purified and characterized in Thermotoga maritima: the anchor protein OmpA1 (or Ompα) and the porin OmpB (or Ompβ). The gene encoding OmpA1 (ompA1) was cloned and sequenced and later assigned to TM0477 in the genome sequence, but because no peptide sequence was available for OmpB, its gene (ompB) was not annotated. We identified six porin candidates in the genome sequence of T. maritima. Of these candidates, only one, encoded by TM0476, has all the characteristics reported for OmpB and characteristics expected of a porin including predominant β-sheet structure, a carboxy terminus porin anchoring motif, and a porin-specific amino acid composition. We highly enriched a toga fraction of cells for OmpB by sucrose gradient centrifugation and hydroxyapatite chromatography and analyzed it by LC/MS/MS. We found that the only porin candidate that it contained was the TM0476 product. This cell fraction also had β-sheet character as determined by circular dichroism, consistent with its enrichment for OmpB. We conclude that TM0476 encodes OmpB. A phylogenetic analysis of OmpB found orthologs encoded in syntenic locations in the genomes of all but two Thermotogales species. Those without orthologs have putative isofunctional genes in their place. Phylogenetic analyses of OmpA1 revealed that each species of the Thermotogales has one or two OmpA homologs. T. maritima has two OmpA homologs, encoded by ompA1 (TM0477) and ompA2 (TM1729), both of which were found in the toga protein-enriched cell extracts. These annotations of the genes encoding toga structural proteins will guide future examinations of the structure and function of this unusual lineage-defining cell sheath
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