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July 1997 Localization transition for a polymer near an interface
Erwin Bolthausen, Frank den Hollander
Ann. Probab. 25(3): 1334-1366 (July 1997). DOI: 10.1214/aop/1024404516


Consider the directed process $(i, S_i)$ where the second component is simple random walk on $\mathbb{Z} (S_0 = 0)$. Define a transformed path measure by weighting each $n$-step path with a factor $\exp [\lambda \sum_{1 \leq i \leq n}(\omega_i + h)\sign (S_i)]$. Here, $(\omega_i)_{i \geq 1}$ is an i.i.d. sequence of random variables taking values $\pm 1$ with probability 1/2 (acting as a random medium) , while $\lambda \in [0, \infty)$ and $h \in [0, 1)$ are parameters. The weight factor has a tendency to pull the path towards the horizontal, because it favors the combinations $S_i > 0, \omega_i = +1$ and $S_i < 0, \omega_i = -1$. The transformed path measure describes a heteropolymer, consisting of hydrophylic and hydrophobic monomers, near an oil-water interface.

We study the free energy of this model as $n \to \infty$ and show that there is a critical curve $\lambda \to h_c (\lambda)$ where a phase transition occurs between localized and delocalized behavior (in the vertical direction). We derive several properties of this curve, in particular, its behavior for $\lambda \downarrow 0$. To obtain this behavior, we prove that as $\lambda, h \downarrow 0$ the free energy scales to its Brownian motion analogue.


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Erwin Bolthausen. Frank den Hollander. "Localization transition for a polymer near an interface." Ann. Probab. 25 (3) 1334 - 1366, July 1997.


Published: July 1997
First available in Project Euclid: 18 June 2002

zbMATH: 0885.60022
MathSciNet: MR1457622
Digital Object Identifier: 10.1214/aop/1024404516

Primary: 60F10 , 60J15 , 82B26

Keywords: Brownian motion , large deviations , phase transition , random medium , Random walk

Rights: Copyright © 1997 Institute of Mathematical Statistics


Vol.25 • No. 3 • July 1997
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