6,088 research outputs found
Quantum Geometry Phenomenology: Angle and Semiclassical States
The phenomenology for the deep spatial geometry of loop quantum gravity is
discussed. In the context of a simple model of an atom of space, it is shown
how purely combinatorial structures can affect observations. The angle operator
is used to develop a model of angular corrections to local, continuum
flat-space 3-geometries. The physical effects involve neither breaking of local
Lorentz invariance nor Planck scale suppression, but rather reply on only the
combinatorics of SU(2) recouping theory. Bhabha scattering is discussed as an
example of how the effects might be observationally accessible.Comment: 5 pages, slightly extended version of the contribution to the
Loops'11 conference proceeding
Spin-triplet paired phases inside ferromagnet induced by Hund's rule coupling and electronic correlations: Application to
We discuss a mechanism of real-space spin-triplet pairing, alternative to
that due to quantum paramagnon excitations, and demonstrate its applicability
to . Both the Hund's rule ferromagnetic exchange and
inter-electronic correlations contribute to the same extent to the equal-spin
pairing, particularly in the regime in which the weak-coupling solution does
not provide any. The theoretical results, obtained within the
orbitally-degenerate Anderson lattice model, match excellently the observed
phase diagram for with the coexistent ferromagnetic (FM1) and
superconducting (-type) phase. Additionally, weak - and -type
paired phases appear in very narrow regions near the metamaganetic (FM2
FM1) and FM1 paramagnetic first-order
phase-transition borders, respectively. The values of magnetic moments in the
FM2 and FM1 states are also reproduced correctly in a semiquantitative manner.
The Hund's metal regime is also singled out as appearing near FM1-FM2 boundary
The Electrostatic Ion Beam Trap : a mass spectrometer of infinite mass range
We study the ions dynamics inside an Electrostatic Ion Beam Trap (EIBT) and
show that the stability of the trapping is ruled by a Hill's equation. This
unexpectedly demonstrates that an EIBT, in the reference frame of the ions
works very similar to a quadrupole trap. The parallelism between these two
kinds of traps is illustrated by comparing experimental and theoretical
stability diagrams of the EIBT. The main difference with quadrupole traps is
that the stability depends only on the ratio of the acceleration and trapping
electrostatic potentials, not on the mass nor the charge of the ions. All kinds
of ions can be trapped simultaneously and since parametric resonances are
proportional to the square root of the charge/mass ratio the EIBT can be used
as a mass spectrometer of infinite mass range
Analysis of standing vertical jumps using a force platform
A force platform analysis of vertical jumping provides an engaging demonstration of the kinematics and dynamics of one-dimensional motion. The height of the jump may be calculated (1) from the flight time of the jump, (2) by applying the impulse–momentum theorem to the force–time curve, and (3) by applying the work–energy theorem to the force-displacement curve
Orthodontic Bracket Manufacturing Tolerances and Dimensional Differences between Select Self-Ligating Brackets
In all manufacturing processes there are tolerances; however, orthodontic bracket manufacturers seldom state the slot dimensional tolerances. This experiment develops a novel method of analyzing slot profile dimensions using photographs of the slot. Five points are selected along each wall, and lines are fitted to define a trapezoidal slot shape. This investigation measures slot height at the slot's top and bottom, angles between walls, slot taper, and the linearity of each wall. Slot dimensions for 30 upper right central incisor self-ligating stainless steel brackets from three manufacturers were evaluated. Speed brackets have a slot height 2% smaller than the nominal 0.559 mm size and have a slightly convergent taper. In-Ovation brackets have a divergent taper at an average angle of 1.47 degrees. In-Ovation is closest to the nominal value of slot height at the slot base and has the smallest manufacturing tolerances. Damon Q brackets are the most rectangular in shape, with nearly 90-degree corners between the slot bottom and walls. Damon slot height is on average 3% oversized
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