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PACS. 65.50 -Thermodynamic properties and entropy. PACS. 71.25 -Nonlocalized single-particle electronic states. PACS. 36.20 -Macromolecules and polymer molecules.Abstract. -The conformation properties of a single polyacetylene chain in solution has been studied as a function of the degree of doping and temperature. We have performed Monte Carlo simulations, using the Hiickel Hamiltonian and accounting for excluded-volume effects. The extra electrons added to the chain by doping are shown to influence the stiffness of the chain mainly by introducing long-range intra-polymer repulsion. The conjugation length and the persistence length are both strongly temperature dependent, but the persistence length also depends heavily on the degree of doping.

Leading and subleading twist transverse momentum dependent parton distribution functions (TMDs) are studied in a quark model framework provided by the bag model. A complete set of relations among different TMDs is derived, and the question is discussed how model-(in)dependent such relations are. A connection of the pretzelosity distribution and quark orbital angular momentum is derived. Numerical results are presented, and applications for phenomenology discussed. In particular, it is shown that in the valence-x region the bag model supports a Gaussian Ansatz for the transverse momentum dependence of TMDs.

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