3,937 research outputs found
Gauging internal fermionic symmetries and spin 3/2 fields
Field theoretic models possessing a global internal fermionic shift symmetry
are considered. When such a symmetry is realized locally, spin 3/2 fields
appear naturally as gauge fields. Implementation of the gauging procedure
requires not only the usual replacement of ordinary derivatives by covariant
derivatives containing the spin 3/2 fields, but also the inclusion of
additional monomials. The Higgs mechanism and the high energy Nambu-Goldstone
fermion equivalence theorem are explicitly demonstrated.Comment: 9 page
Effective Constraints for Relativistic Quantum Systems
Determining the physical Hilbert space is often considered the most difficult
but crucial part of completing the quantization of a constrained system. In
such a situation it can be more economical to use effective constraint methods,
which are extended here to relativistic systems as they arise for instance in
quantum cosmology. By side-stepping explicit constructions of states, such
tools allow one to arrive much more feasibly at results for physical
observables at least in semiclassical regimes. Several questions discussed
recently regarding effective equations and state properties in quantum
cosmology, including the spreading of states and quantum back-reaction, are
addressed by the examples studied here.Comment: 27 pages, 2 figures; v2: new appendix comparing effective constraints
and physical coherent states by an exampl
Mindfulness: Mediating the Relationship between Attachment Security and Parenting Style
The current project examines the relationships between attachment security, parenting style, and mindfulness. The level of mindfulness an individual demonstrates is argued to mediate the relationship between an individual’s attachment security and her respective parenting style. The population is composed of 35 mothers who were drawn from a university clinic setting. Measures utilized included: the Relationship Questionnaire (RQ), which measures adult attachment security, the Mindful Attention Awareness Scale (MAAS), which measures the level of mindfulness an individual demonstrates, and the Parental Authority Questionnaire – Revised (PAQ-R), which measures parenting style attitudes. Results demonstrated no significant relationships between attachment security and parenting style. In examining the relationship between attachment security and mindfulness, individuals designated securely attached demonstrated higher levels of mindfulness than their insecure counterparts. With respect to mindfulness and its relationship with parenting style, mindfulness was positively correlated with an authoritative parenting style but did not demonstrate a significant relationship with either an authoritarian or a permissive parenting style. A test of mediation was conducted to examine the relationship between attachment security and parenting style, with mindfulness as the mediator. The model evidenced a significant reduction in the relationship between attachment security and an authoritative parenting style, suggesting that mindfulness successfully mediated this relationship. Mediation was not found in the case of the permissive and authoritarian styles. Discussions of the methodological approach, the implications of these findings, and future directions for research are presented
The 5-kW arcjet power electronics
The initial design and evaluation of a 5 kW arcjet power electronics breadboard which as been integrated with a modified 1 kW design laboratory arcjet is presented. A single stage, 5 kW full bridge, pulse width modulated (PWM), power converter was developed which was phase shift regulated. The converter used metal oxide semiconductor field effect transistor (MOSFET) power switches and incorporated current mode control and an integral arcjet pulse ignition circuit. The unoptimized power efficiency was 93.5 and 93.9 percent at 5 kW and 50A output at input voltages of 130 and 150V, respectively. Line and load current regulation at 50A output was within one percent. The converter provided up to 6.6 kW to the arcjet with simulated ammonia used as a propellant
Interactive Chemical Reactivity Exploration
Elucidating chemical reactivity in complex molecular assemblies of a few
hundred atoms is, despite the remarkable progress in quantum chemistry, still a
major challenge. Black-box search methods to find intermediates and
transition-state structures might fail in such situations because of the
high-dimensionality of the potential energy surface. Here, we propose the
concept of interactive chemical reactivity exploration to effectively introduce
the chemist's intuition into the search process. We employ a haptic pointer
device with force-feedback to allow the operator the direct manipulation of
structures in three dimensions along with simultaneous perception of the
quantum mechanical response upon structure modification as forces. We elaborate
on the details of how such an interactive exploration should proceed and which
technical difficulties need to be overcome. All reactivity-exploration concepts
developed for this purpose have been implemented in the Samson programming
environment.Comment: 36 pages, 14 figure
Stability of quantum states of finite macroscopic systems against classical noises, perturbations from environments, and local measurements
We study the stability of quantum states of macroscopic systems of finite
volume V, against weak classical noises (WCNs), weak perturbations from
environments (WPEs), and local measurements (LMs). We say that a pure state is
`fragile' if its decoherence rate is anomalously great, and `stable against
LMs' if the result of a LM is not affected by another LM at a distant point. By
making full use of the locality and huge degrees of freedom, we show the
following: (i) If square fluctuation of every additive operator is O(V) or less
for a pure state, then it is not fragile in any WCNs or WPEs. (ii) If square
fluctuations of some additive operators are O(V^2) for a pure state, then it is
fragile in some WCNs or WPEs. (iii) If a state (pure or mixed) has the `cluster
property,' then it is stable against LMs, and vice versa. These results have
many applications, among which we discuss the mechanism of symmetry breaking in
finite systems.Comment: 6 pages, no figure.Proof of the theorem is described in the revised
manuscrip
Non-unitary representations of the SU(2) algebra in the Dirac equation with a Coulomb potential
A novel realization of the classical SU(2) algebra is introduced for the
Dirac relativistic hydrogen atom defining a set of operators that, besides,
allow the factorization of the problem. An extra phase is needed as a new
variable in order to define the algebra. We take advantage of the operators to
solve the Dirac equation using algebraic methods. To acomplish this, a similar
path to the one used in the angular momentum case is employed; hence, the
radial eigenfuntions calculated comprise non unitary representations of the
algebra. One of the interesting properties of such non unitary representations
is that they are not labeled by integer nor by half-integer numbers as happens
in the usual angular momentum representation.Comment: 20 pages 1 eps figure in a single zipped file, submitted to J. Math.
Phy
Canonical Quantization Inside the Schwarzschild Black Hole
We propose a scheme for quantizing a scalar field over the Schwarzschild
manifold including the interior of the horizon. On the exterior, the timelike
Killing vector and on the horizon the isometry corresponding to restricted
Lorentz boosts can be used to enforce the spectral condition. For the interior
we appeal to the need for CPT invariance to construct an explicitly positive
definite operator which allows identification of positive and negative
frequencies. This operator is the translation operator corresponding to the
inexorable propagation to smaller radii as expected from the classical metric.
We also propose an expression for the propagator in the interior and express it
as a mode sum.Comment: 8 pages, LaTex. Title altered. One reference added. A few typos esp.
eq.(7),(38) corrected. To appear in Class.Q.Gra
Symplectic map description of Halley's comet dynamics
The main features of 1P/Halley chaotic dynamics can be described by a two
dimensional symplectic map. Using Mel'nikov integral we semi-analytically
determine such a map for 1P/Halley taking into account gravitational
interactions from the Sun and the eight planets. We determine the Solar system
kick function ie the energy transfer to 1P/Halley along one passage through the
Solar system. Our procedure allows to compute for each planet its contribution
to the Solar system kick function which appears to be the sum of the Keplerian
potential of the planet and of a rotating circular gravitational dipole
potential due to the Sun movement around Solar system barycenter. We test the
robustness of the symplectic Halley map by directly integrating Newton's
equations over yr around Y2K and by reconstructing the
Solar system kick function. Our results show that the Halley map with fixed
parameters gives a reliable description of comet dynamics on time scales of
yr while on a larger scales the parameters of the map are slowly
changing due to slow oscillations of orbital momentum.Comment: To be published in Physics Letter A, 8 pages, 5 figures,
supplementary material at
http://perso.utinam.cnrs.fr/~lages/publications/sm/sm21.htm
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