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[en] Coarsegraining is a systematic way of reducing the number of degrees of freedom representing a system of interest. Several coarsegraining techniques have so far been developed, such as iterative Boltzmann inversion, forcematching, and inverse Monte Carlo. However, there is no unified framework that implements these methods and allows their direct comparison. We present a versatile objectoriented toolkit for coarsegraining applications that implements these techniques and provides a flexible modular platform for the further development of coarsegraining techniques. All methods are illustrated and compared by coarsegraining the SPCE water model and liquid propane.
[en] Highlights: • We develop theory for the rovibrational spectra of extremely flexible molecules. • An extremely flexible molecule has no well-defined structure. • Protonated methane is the prototype example. • We successfully describe the nuclear motion as that of a molecular superrotor. • For the superrotor has SO(5) symmetry. This paper treats the low energy rotation-vibration problem in , an extremely flexible molecule lacking a well-defined structure. Using SO(5) symmetry it determines zeroth order energies, and complete nuclear permutation S5 symmetries, using a five-dimensional model involving rotation and two vibrations (which one might imagine as two different “cooperative” HCH bends). These two vibrations are presumed to be unhindered by the molecular potential function and their analytical form is not determined. The other ten vibrational degrees of freedom are presumed to be “rigid” (or averaged over). The general energy expression for this “rigid superrotor” is obtained as where B is the rotational constant and the non-negative integers and satisfy . The superrotor predictions agree favourably with the available experimental data. Applications of the superrotor model to extremely flexible molecules other than are discussed.
[en] supergravity is known to contain a ghost mode associated with higher-derivative terms if it contains with greater than two. We remove the ghost in supergravity by introducing auxiliary gauge field to absorb the ghost. We dub this method as the ghostbuster mechanism https://doi.org/10.1007/JHEP09(2016)106. We show that the mechanism removes the ghost supermultiplet but also terms including with , after integrating out auxiliary degrees of freedom. For pure supergravity case, there appears an instability in the resultant scalar potential. We then show that the instability of the scalar potential can be cured by introducing matter couplings in such a way that the system has a stable potential.
[en] A detailed Gitman-Lyakhovich-Tyutin analysis for higher-order topologically massive gravity is performed. The full structure of the constraints, the counting of physical degrees of freedom, and the Dirac algebra among the constraints are reported. Moreover, our analysis presents a new structure into the constraints and we compare our results with those reported in the literature where a standard Ostrogradski framework was developed.
[en] A high precision redundant robotic manipulator for overcoming contents imposed by obstacles or imposed by a highly congested work space is disclosed. One embodiment of the manipulator has four degrees of freedom and another embodiment has seven degrees of freedom. Each of the embodiments utilize a first selective compliant assembly robot arm (SCARA) configuration to provide high stiffness in the vertical plane, a second SCARA configuration to provide high stiffness in the horizontal plane. The seven degree of freedom embodiment also utilizes kinematic redundancy to provide the capability of avoiding obstacles that lie between the base of the manipulator and the end effector or link of the manipulator. These additional three degrees of freedom are added at the wrist link of the manipulator to provide pitch, yaw and roll. The seven degrees of freedom embodiment uses one revolute point per degree of freedom. For each of the revolute joints, a harmonic gear coupled to an electric motor is introduced, and together with properly designed based servo controllers provide an end point repeatability of less than 10 microns. 3 figs
[en] We provide a BRST formalism for the soft-collinear effective theory describing interactions of soft and collinear degrees of freedom in the presence of a hard interaction. In particular, we develop a BRST symmetry transformation for SCET theory. We further generalize the BRST formulation by making the transformation parameter field dependent. This establishes a mapping between several SCET actions consistently when defined in different gauge conditions. In fact, a definite structure of gauge-fixed actions corresponding to any particular gauge condition can be generated for SCET theory using our formulation.
[en] For electron-phonon Hamiltonians with the couplings linear in the phonon operators, we construct a class of unitary transformations that separate the normal modes into two groups. The modes in the first group interact with the electronic degrees of freedom directly. The modes in the second group interact directly only with the modes in the first group but not with the electronic system. These transformations can be carried out independently for different types of phonon modes, e.g., high- versus low-frequency phonon bands. This construction generalizes recently introduced transformations for systems exhibiting a conical intersection topology. The separation of the normal modes into several groups allows one to develop new approximation schemes. We apply one of such schemes to study electronic relaxation at a semiconducting polymer interface.
[en] We construct effective supergravity theories from customized constrained superfields which provide a setup consistent both for the description of inflation and the subsequent reheating processes. These theories contain the minimum degrees of freedom in the bosonic sector required for single-field inflation.
[en] An overview of the online competition, Physics Cup—IPhO2012 is given. This preceded the 43rd International Physics Olympiad and included ten problems, published monthly. Three problems, the most popular among the contestants, are discussed in detail. These problems deal with laser speckle patterns, geometrical optics and LC circuits with four degrees of freedom. The results of the competition and of the poll carried out among the contestants are used to discuss the relationship between the properties of the problems: difficulty, closeness to reality and beauty (as perceived by the contestants). (paper)