Flory Exponents from a Self-Consistent Renormalization Group

The wandering exponent $\nu$ for an isotropic polymer is predicted remarkably well by a simple argument due to Flory. By considering oriented polymers living in a one-parameter family of background tangent fields, we are able to relate the wandering exponent to the exponent in the background field through an $\epsilon$-expansion. We then choose the background field to have the same correlations as the individual polymer, thus self-consistently solving for $\nu$. We find $\nu=3/(d+2)$ for $d<4$ and $\nu=1/2$ for $d\ge 4$, which is exactly the Flory result.Comment: 11 pages, Plain Tex (macros included), IASSNS-HEP-93/1

Smectic Order in Double-Twist Cylinders

I propose a double-twist texture with local smectic order, which may have been seen in recent experiments. As in the Renn-Lubensky TGB phase, the smectic order is broken only through a lattice of screw dislocations. A melted lattice of screw dislocations can produce a double-twist texture as can an unmelted lattice. In the latter case I show that geometry only allows for certain angles between smectic regions. I discuss the possibility of connecting these double-twist tubes together to form a smectic blue phase.Comment: 12 pages, plain TeX (macros included), 5 postscript figures (included). Revised version has some more text and a new figure. To appear in J. Phys. II France (1997

Poisson Bracket Formulation of Nematic Polymer Dynamics

We formulate the dynamical theory of nematic polymers, starting from a microscopic Poisson bracket approach. We find that the Poisson bracket between the nematic director and momentum depends on the (Maier-Saupe) order parameter of the nematic phase. We use this to derive reactive couplings of the nematic director to the strain rates. Additionally, we find that local dynamics breaks down as the polymers begin to overlap. We offer a physical picture for both results.Comment: Harvmac, 17 pages, 1 postscript figur

Liquids with Chiral Bond Order

I describe new phases of a chiral liquid crystal with nematic and hexatic order. I find a conical phase, similar to that of a cholesteric in an applied magnetic field for Frank elastic constants $K_2>K_3$. I discuss the role of fluctuations in the context of this phase and the possibility of satisfying the inequality for sufficiently long polymers. In addition I discuss the topological constraint relating defects in the bond order field to textures of the nematic and elucidate its physical meaning. Finally I discuss the analogy between smectic liquid crystals and chiral hexatics and propose a defect-riddled ground state, akin to the Renn-Lubensky twist grain boundary phase of chiral smectics.Comment: plain TeX, 19 Pages, four figures, uufiled and included. Minor correction and clarificatio

Local Writhing Dynamics

We present an alternative local definition of the writhe of a self-avoiding closed loop which differs from the traditional non-local definition by an integer. When studying dynamics this difference is immaterial. We employ a formula due to Aldinger, Klapper and Tabor for the change in writhe and propose a set of local, link preserving dynamics in an attempt to unravel some puzzles about actin.Comment: plain TeX, harvmac + epsf, 11 pages, 1 included eps figure. Reference adde