763 research outputs found
Dirac Cat States in Relativistic Landau Levels
We show that a relativistic version of Schrodinger cat states, here called
Dirac cat states, can be built in relativistic Landau levels when an external
magnetic field couples to a relativistic spin 1/2 charged particle. Under
suitable initial conditions, the associated Dirac equation produces unitarily
Dirac cat states involving the orbital quanta of the particle in a well defined
mesoscopic regime. We demonstrate that the proposed Dirac cat states have a
purely relativistic origin and cease to exist in the non-relativistic limit. In
this manner, we expect to open relativistic quantum mechanics to the rich
structures of quantum optics and quantum information.Comment: Revtex4, color figures, submitted for publicatio
The relation between the model of a crystal with defects and Plebanski's theory of gravity
In the present investigation we show that there exists a close analogy of
geometry of spacetime in GR with a structure of defects in a crystal. We
present the relation between the Kleinert's model of a crystal with defects and
Plebanski's theory of gravity. We have considered the translational defects -
dislocations, and the rotational defects - disclinations - in the 3- and
4-dimensional crystals. The 4-dimensional crystalline defects present the
Riemann-Cartan spacetime which has an additional geometric property - "torsion"
- connected with dislocations. The world crystal is a model for the gravitation
which has a new type of gauge symmetry: the Einstein's gravitation has a zero
torsion as a special gauge, while a zero connection is another equivalent gauge
with nonzero torsion which corresponds to the Einstein's theory of
"teleparallelism". Any intermediate choice of the gauge with nonzero connection
A^{IJ}_\mu is also allowed. In the present investigation we show that in the
Plebanski formulation the phase of gravity with torsion is equivalent to the
ordinary or topological gravity, and we can exclude a torsion as a separate
dynamical variable.Comment: 13 pages, 2 figure
Gauge-invariant and infrared-improved variational analysis of the Yang-Mills vacuum wave functional
We study a gauge-invariant variational framework for the Yang-Mills vacuum
wave functional. Our approach is built on gauge-averaged Gaussian trial
functionals which substantially extend previously used trial bases in the
infrared by implementing a general low-momentum expansion for the vacuum-field
dispersion (which is taken to be analytic at zero momentum). When completed by
the perturbative Yang-Mills dispersion at high momenta, this results in a
significantly enlarged trial functional space which incorporates both dynamical
mass generation and asymptotic freedom. After casting the dynamics associated
with these wave functionals into an effective action for collections of soft
vacuum-field orbits, the leading infrared improvements manifest themselves as
four-gradient interactions. Those turn out to significantly lower the minimal
vacuum energy density, thus indicating a clear overall improvement of the
vacuum description. The dimensional transmutation mechanism and the dynamically
generated mass scale remain almost quantitatively robust, however, which
ensures that our prediction for the gluon condensate is consistent with
standard values. Further results include a finite group velocity for the soft
gluonic modes due to the higher-gradient corrections and indications for a
negative differential color resistance of the Yang-Mills vacuum.Comment: 47 pages, 5 figures (vs2 contains a few minor stylistic adjustments
to match the published version
The Physical Principles of Quantum Mechanics. A critical review
The standard presentation of the principles of quantum mechanics is
critically reviewed both from the experimental/operational point and with
respect to the request of mathematical consistency and logical economy. A
simpler and more physically motivated formulation is discussed. The existence
of non commuting observables, which characterizes quantum mechanics with
respect to classical mechanics, is related to operationally testable
complementarity relations, rather than to uncertainty relations. The drawbacks
of Dirac argument for canonical quantization are avoided by a more geometrical
approach.Comment: Bibliography and section 2.1 slightly improve
The su(1,1) dynamical algebra from the Schr\"odinger ladder operators for N-dimensional systems: hydrogen atom, Mie-type potential, harmonic oscillator and pseudo-harmonic oscillator
We apply the Schr\"odinger factorization to construct the ladder operators
for hydrogen atom, Mie-type potential, harmonic oscillator and pseudo-harmonic
oscillator in arbitrary dimensions. By generalizing these operators we show
that the dynamical algebra for these problems is the Lie algebra.Comment: 10 page
Cyclotron motion and magnetic focusing in semiconductor quantum wells with spin-orbit coupling
We investigate the ballistic motion of electrons in III-V semiconductor
quantum wells with Rashba spin-orbit coupling in a perpendicular magnetic
field. Taking into account the full quantum dynamics of the problem, we explore
the modifications of classical cyclotron orbits due to spin-orbit interaction.
As a result, for electron energies comparable with the cyclotron energy the
dynamics are particularly rich and not adequately described by semiclassical
approximations. Our study is complementary to previous semiclassical approaches
concentrating on the regime of weaker fields.Comment: 14 pages, 8 figures included, version to appear in Phys. Rev.
Electron-radiation interaction in a Penning trap: beyond the dipole approximation
We investigate the physics of a single trapped electron interacting with a
radiation field without the dipole approximation. This gives new physical
insights in the so-called geonium theory.Comment: 12 pages, RevTeX, 6 figures, Approved for publication in Phys. Rev.
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