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arXiv 0709.1629math.PRcond-mat.soft
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无序钉扎模型和共聚物:超越退火边界

Disordered pinning models and copolymers: beyond annealed bounds

Fabio Lucio Toninelli

摘要:

我们考虑一个一般的模型的无序共聚物吸附。作为特定情况,这包括由Garel等人[Europhys. Lett. 8(1989)9- 13],在各种维度上的钉扎和润湿模型,以及DNA变性的波兰-Scheraga模型。通过对分拆函数的非整数矩的估计,我们证明了自由能的一个新的变分上界。作为一个应用,我们表明,对于强无序的淬火临界点不同于退火的,例如,如果无序分布是高斯。特别地,对于具有循环指数$0<α<1/2$的钉扎模型,这意味着存在从弱无序到强无序的过渡。对于共聚物模型,在一个(限制性)条件下的基本更新的法律,我们表明,临界点与理论物理文献中通过重整化群参数预测的一致。更强的结果适用于Bodineau和Giacomin [J. Statist. 117(2004)801- 818]:在不限制基础更新定律的情况下,临界点与相应的重整化群预测相一致。

英文摘要:

We consider a general model of a disordered copolymer with adsorption. This includes, as particular cases, a generalization of the copolymer at a selective interface introduced by Garel et al. [Europhys. Lett. 8 (1989) 9--13], pinning and wetting models in various dimensions, and the Poland--Scheraga model of DNA denaturation. We prove a new variational upper bound for the free energy via an estimation of noninteger moments of the partition function. As an application, we show that for strong disorder the quenched critical point differs from the annealed one, for example, if the disorder distribution is Gaussian. In particular, for pinning models with loop exponent $0<α<1/2$ this implies the existence of a transition from weak to strong disorder. For the copolymer model, under a (restrictive) condition on the law of the underlying renewal, we show that the critical point coincides with the one predicted via renormalization group arguments in the theoretical physics literature. A stronger result holds for a "reduced wetting model" introduced by Bodineau and Giacomin [J. Statist. Phys. 117 (2004) 801--818]: without restrictions on the law of the underlying renewal, the critical point coincides with the corresponding renormalization group prediction.

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