7,177 research outputs found

    Quantum Geometry Phenomenology: Angle and Semiclassical States

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    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 UGe2\mathrm{UGe}_2

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    We discuss a mechanism of real-space spin-triplet pairing, alternative to that due to quantum paramagnon excitations, and demonstrate its applicability to UGe2\mathrm{UGe_2}. 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 UGe2\mathrm{UGe_2} with the coexistent ferromagnetic (FM1) and superconducting (A1A_1-type) phase. Additionally, weak A2A_2- and AA-type paired phases appear in very narrow regions near the metamaganetic (FM2 →\rightarrow FM1) and FM1 →\rightarrow 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

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    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

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    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

    Moderate intensity cycling following eccentric contractions does not attenuate indirect markers of muscle damage.

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    Unaccustomed eccentric muscle contraction causes prolonged changes to indirect markers of muscle damage (Clarkson & Hubal, 2002). It has been proposed that active recovery therapy (ART) consisting of non-eccentric based movements may aid in the recovery process uts of moderate intensity cycling in the followin(Sayers et al., 2000). The purpose of this investigation was to compare the effect of ART on changes in one repetition maximum (1RM), dynamic muscle function, swelling, delayed onset muscle soreness (DOMS), and changes in MRI T2 relaxation times post exercise induced muscle damage (EIMD). Ten previously trained participants (at least 1 lower body resistance training session a week) were recruited from within the university community and divided in two groups: a cycling ART group (CG, n = 5) who performed three bouts of moderate intensity cycling in the four days following the EIMD protocol and a non-cycling group (NCG, n= 5) who performed no cycling in the four days following the EIMD protocol. There were no statistical differences between the two treatment groups for height, weight or age (P \u3c 0.05). The EIMD protocol reduced 1RM, muscle function, elicited DOMS and increased swelling and T2 relaxation times in both CG and NCG (P \u3c0.05). In the 96 h period post the EIMD protocol no differences were observed between CG and NCG for the magnitude of change or rate of recovery. Three bouts of cycling ART performed at 24 h intervals after an EIMD did not improve indirect markers of muscle damage
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