7,392 research outputs found
Strange magnetic moment of the nucleon and SU(3) breaking: group theoretical approach
An extended group-theoretical approach to magnetic moments of the octet
baryons is proposed with the aim of extracting the strange magnetic moment of
the nucleon. Special attention is given to flavor SU(3) breaking. In this
approach, isoscalar and isovector magnetic moments are treated separately in
view of their different behavior under SU(3) breaking. We conclude that the
anomalous magnetic moment associated with the flavor singlet current is small.
Together with the small isoscalar anomalous magnetic moment of the nucleon,
this implies suppression of the strange magnetic moment of the proton which is
found to be small and positive, mu^(s) = (0.16 \pm 0.03) mu_N in units of the
nuclear magneton.Comment: 6 pages, no figure, 6 tables, use REVTeX
On Epstein's trajectory model of non-relativistic quantum mechanics
In 1952 Bohm presented a theory about non-relativistic point-particles moving
along deterministic trajectories and showed how it reproduces the predictions
of standard quantum theory. This theory was actually presented before by de
Broglie in 1926, but Bohm's particular formulation of the theory inspired
Epstein to come up with a different trajectory model. The aim of this paper is
to examine the empirical predictions of this model. It is found that the
trajectories in this model are in general very different from those in the de
Broglie-Bohm theory. In certain cases they even seem bizarre and rather
unphysical. Nevertheless, it is argued that the model seems to reproduce the
predictions of standard quantum theory (just as the de Broglie-Bohm theory).Comment: 12 pages, no figures, LaTex; v2 minor improvement
Classical mechanics without determinism
Classical statistical particle mechanics in the configuration space can be
represented by a nonlinear Schrodinger equation. Even without assuming the
existence of deterministic particle trajectories, the resulting quantum-like
statistical interpretation is sufficient to predict all measurable results of
classical mechanics. In the classical case, the wave function that satisfies a
linear equation is positive, which is the main source of the fundamental
difference between classical and quantum mechanics.Comment: 11 pages, revised, to appear in Found. Phys. Let
Poincare Semigroup Symmetry as an Emergent Property of Unstable Systems
The notion that elementary systems correspond to irreducible representations
of the Poincare group is the starting point for this paper, which then goes on
to discuss how a semigroup for the time evolution of unstable states and
resonances could emerge from the underlying Poincare symmetry. Important tools
in this analysis are the Clebsch-Gordan coefficients for the Poincare group.Comment: 17 pages, 1 figur
Entanglement and State Preparation
When a subset of particles in an entangled state is measured, the state of
the subset of unmeasured particles is determined by the outcome of the
measurement. This first measurement may be thought of as a state preparation
for the remaining particles. In this paper, we examine how the duration of the
first measurement effects the state of the unmeasured subsystem. The state of
the unmeasured subsytem will be a pure or mixed state depending on the nature
of the measurement.
In the case of quantum teleportation we show that there is an eigenvalue
equation which must be satisfied for accurate teleportation. This equation
provides a limitation to the states that can be accurately teleported.Comment: 24 pages, 3 figures, submitted to Phys. Rev.
The free energy in a class of quantum spin systems and interchange processes
We study a class of quantum spin systems in the mean-field setting of the
complete graph. For spin the model is the Heisenberg ferromagnet,
for general spin it has a probabilistic representation
as a cycle-weighted interchange process. We determine the free energy and the
critical temperature (recovering results by T\'oth and by Penrose when
). The critical temperature is shown to coincide (as a function of
) with that of the state classical Potts model, and the phase
transition is discontinuous when .Comment: 22 page
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 Black Hole Stability in Critical Gravities
We consider extended cosmological gravities with Ricci tensor and scalar
squared terms in diverse dimensions. These theories admit solutions of Einstein
metrics, including the Schwarzschild-Tangherlini AdS black holes, whose mass
and entropy vanish at the critical point. We perform linearized analysis around
the black holes and show that in general the spectrum consists of the usual
spin-2 massless and ghost massive modes. We demonstrate that there is no
exponentially-growing tachyon mode in the black holes. At the critical point,
the massless spin-2 modes have zero energy whilst the massive spin-2 modes are
replaced by the log modes. There always exist certain linear combination of
massless and log modes that has negative energy. Thus the stability of the
black holes requires that the log modes to be truncated out by the boundary
condition.Comment: 16 pages, minor corrections, further comments and references adde
Quantum properties of classical Fisher information
The Fisher information of a quantum observable is shown to be proportional to
both (i) the difference of a quantum and a classical variance, thus providing a
measure of nonclassicality; and (ii) the rate of entropy increase under
Gaussian diffusion, thus providing a measure of robustness. The joint
nonclassicality of position and momentum observables is shown to be
complementary to their joint robustness in an exact sense.Comment: 16 page
Bohmian description of a decaying quantum system
We present a Bohmian description of a decaying quantum system. A particle is
initially confined in a region around the origin which is surrounded by a
repulsive potential barrier. The particle leaks out in time tunneling through
the barrier. We determine Bohm trajectories with which we can visualize various
features of the decaying system.Comment: 14 pages, 5 figure
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