Path integral representations in noncommutative quantum mechanics and noncommutative version of Berezin-Marinov action

It is known that actions of field theories on a noncommutative space-time can be written as some modified (we call them $\theta$-modified) classical actions already on the commutative space-time (introducing a star product). Then the quantization of such modified actions reproduces both space-time noncommutativity and usual quantum mechanical features of the corresponding field theory. The $\theta$-modification for arbitrary finite-dimensional nonrelativistic system was proposed by Deriglazov (2003). In the present article, we discuss the problem of constructing $\theta$-modified actions for relativistic QM. We construct such actions for relativistic spinless and spinning particles. The key idea is to extract $\theta$-modified actions of the relativistic particles from path integral representations of the corresponding noncommtative field theory propagators. We consider Klein-Gordon and Dirac equations for the causal propagators in such theories. Then we construct for the propagators path-integral representations. Effective actions in such representations we treat as $\theta$-modified actions of the relativistic particles. To confirm the interpretation, we quantize canonically these actions. Thus, we obtain the Klein-Gordon and Dirac equations in the noncommutative field theories. The $\theta$-modified action of the relativistic spinning particle is just a generalization of the Berezin-Marinov pseudoclassical action for the noncommutative case

Effect of yarn hairiness on energy consumption in rotating a ring-spun yarn package

The effect of yarn hairiness on energy consumption when rotating a ring-spun yarn package is investigated theoretically and experimentally. A theoretical model is developed to calculate the energy required to rotate hair fibers, based on hair length and number as well as package speed and size. A single spindle test rig is used to verify the theoretical prediction. The experimental results confirm the theoretical prediction that the package power increases with increased yarn hairiness level and spindle speed

Type-Decomposition of a Pseudo-Effect Algebra

The theory of direct decomposition of a centrally orthocomplete effect algebra into direct summands of various types utilizes the notion of a type-determining (TD) set. A pseudo-effect algebra (PEA) is a (possibly) noncommutative version of an effect algebra. In this article we develop the basic theory of centrally orthocomplete PEAs, generalize the notion of a TD set to PEAs, and show that TD sets induce decompositions of centrally orthocomplete PEAs into direct summands.Comment: 18 page

Spin dynamics of a trapped spin-1 Bose Gas above the Bose-Einstein transition temperature

We study collective spin oscillations in a spin-1 Bose gas above the Bose-Einstein transition temperature. Starting from the Heisenberg equation of motion, we derive a kinetic equation describing the dynamics of a thermal gas with the spin-1 degree of freedom. Applying the moment method to the kinetic equation, we study spin-wave collective modes with dipole symmetry. The dipole modes in the spin-1 system are found to be classified into the three type of modes. The frequency and damping rate are obtained as functions of the peak density. The damping rate is characterized by three relaxation times associated with collisions.Comment: 19 pages, 5 figur

Testing SUSY

If SUSY provides a solution to the hierarchy problem then supersymmetric states should not be too heavy. This requirement is quantified by a fine tuning measure that provides a quantitative test of SUSY as a solution to the hierarchy problem. The measure is useful in correlating the impact of the various experimental measurements relevant to the search for supersymmetry and also in identifying the most sensitive measurements for testing SUSY. In this paper we apply the measure to the CMSSM, computing it to two-loop order and taking account of current experimental limits and the constraint on dark matter abundance. Using this we determine the present limits on the CMSSM parameter space and identify the measurements at the LHC that are most significant in covering the remaining parameter space. Without imposing the LEP Higgs mass bound we show that the smallest fine tuning (1:13) consistent with a relic density within the WMAP bound corresponds to a Higgs mass of 114$\pm$2 GeV. Fine tuning rises rapidly for heavier Higgs.Comment: 12 pages, 7 figures; references added, figures updated for extended parameter space sca

Conductance Peak Height Correlations for a Coulomb-Blockaded Quantum Dot in a Weak Magnetic Field

We consider statistical correlations between the heights of conductance peaks corresponding to two different levels in a Coulomb-blockaded quantum dot. Correlations exist for two peaks at the same magnetic field if the field does not fully break time-reversal symmetry as well as for peaks at different values of a magnetic field that fully breaks time-reversal symmetry. Our results are also relevant to Coulomb-blockade conductance peak height statistics in the presence of weak spin-orbit coupling in a chaotic quantum dot.Comment: 5 pages, 3 figures, REVTeX 4, accepted for publication in Phys. Rev.

Simultaneous improvement of heating efficiency and mechanical strength of a self-healing thermoplastic polymer by hybridizing magnetic particles with conductive fibres

Radio-Frequency (RF) induction heating is a versatile in-situ method for contactless heating of structures by utilizing either magnetic hysteresis loss or eddy-current loss mechanism. Achieving high heating efficiency without degrading mechanical properties is a major challenge. Herein, a RF induction compatible self-healing composite was developed by hybridizing iron oxides (Fe3O4) nanoparticles with carbon fibre veils (CFVs) in poly(ethylene-co-methacrylic acid) (EMAA), which could possess both high magnetic and electrical properties. Owing to the multiscale conductive networks built by Fe3O4 nanoparticles and CFVs, the electrical conductivity of the nanocomposite was found to be higher than the linear combination of the individual contributions, thus creating a synergistic improvement in electrical conductivity and heating efficiency. Furthermore, single lap shear test results demonstrated that the combination of Fe3O4 nanoparticles and CFVs could significantly improve the bonding strength of EMAA polymer. Therefore, the hybridization of magnetic particles with conductive fibres offers a promising technology for a wide range of applications, such as self-healing, reversable bonding, and multiple use bonded composites

Magnetotransport properties of magnetic granular solids: The role of unfilled d bands

We calculate the magnetoresistance and magnetothermopower of magnetic granular solids. Contrary to previous theories of the giant magnetoresistance (GMR), we demonstrate that the unfilled d bands of magnetic grains play an essential role in the transport properties of these systems. Our results relate GMR and magnetothermopower to microscopic and geometric quantities, and provide a natural explanation for many experimentally observed features, such as the (M/Ms)2 dependence of the GMR, the giant magnetothermopower and its 1/ρ scaling behavior, and the absence of negative GMR in rare-earth-nonmagnetic structures

Equations of Motion for Massive Spin 2 Field Coupled to Gravity

We investigate the problems of consistency and causality for the equations of motion describing massive spin two field in external gravitational and massless scalar dilaton fields in arbitrary spacetime dimension. From the field theoretical point of view we consider a general classical action with non-minimal couplings and find gravitational and dilaton background on which this action describes a theory consistent with the flat space limit. In the case of pure gravitational background all field components propagate causally. We show also that the massive spin two field can be consistently described in arbitrary background by means of the lagrangian representing an infinite series in the inverse mass. Within string theory we obtain equations of motion for the massive spin two field coupled to gravity from the requirement of quantum Weyl invariance of the corresponding two dimensional sigma-model. In the lowest order in $\alpha'$ we demonstrate that these effective equations of motion coincide with consistent equations derived in field theory.Comment: 27 pages, LaTeX file, journal versio