8,458 research outputs found
Relativity of representations in quantum mechanics
Only the position representation is used in introductory quantum mechanics
and the momentum representation is not usually presented until advanced
undergraduate courses. To emphasize the relativity of the representations of
the abstract formulation of quantum mechanics, two examples of representations
related to the operators aX+(1-a)P and (XP+PX)/2 are presented.Comment: 10 pages, no figures, accepted in Am.J.Phy
Quantum mechanics in finite dimensional Hilbert space
The quantum mechanical formalism for position and momentum of a particle in a
one dimensional cyclic lattice is constructively developed. Some mathematical
features characteristic of the finite dimensional Hilbert space are compared
with the infinite dimensional case. The construction of an unbiased basis for
state determination is discussed.Comment: 14 pages, no figure
Entanglement for all quantum states
It is shown that a state that is factorizable in the Hilbert space
corresponding to some choice of degrees of freedom, becomes entangled for a
different choice of degrees of freedom. Therefore, entanglement is not a
special case but is ubiquitous in quantum systems. Simple examples are
calculated and a general proof is provided. The physical relevance of the
change of tensor product structure is mentioned.Comment: 9 page
EPR before EPR: a 1930 Einstein-Bohr thought experiment revisited
In 1930 Einstein argued against consistency of the time-energy uncertainty
relation by discussing a thought experiment involving a measurement of mass of
the box which emitted a photon. Bohr seemingly triumphed over Einstein by
arguing that the Einstein's own general theory of relativity saves the
consistency of quantum mechanics. We revisit this thought experiment from a
modern point of view at a level suitable for undergraduate readership and find
that neither Einstein nor Bohr was right. Instead, this thought experiment
should be thought of as an early example of a system demonstrating nonlocal
"EPR" quantum correlations, five years before the famous
Einstein-Podolsky-Rosen paper.Comment: 11 pages, revised, accepted for publication in Eur. J. Phy
Efficiency diagnostic and advantages of procalcitonin and C-reactive protein in the early diagnosis of sepsis
The goal of our study is to assess the diagnostic profi tability of procalcitonin (PCT) in septic shock and another biomarker as C-reactive protein (CRP). Results: Fifty-four septic patients were assessed, 66% were males; mean age, 63 years. Eighty-eight percent was diagnosed as septic shock and 11% severe sepsis. Seventy-six percent were medical patients. Positive blood cultures in 42.5%. Sepsis origin: respiratory 46%, neurological 5%,
digestive 37% and urinary 3%. Average SOFA score was 10.4.
Conclusions: PCT and CRP have the same efficiency in early sepsis diagnosis. The PCT and CRP effi ciency diagnostic together is signifi cant but small. We suggest using both with the doubt of sepsis.Ye
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