Getting rid of the ghosts: a toy-model of membrane melting

Olivier Coquand

Home/Archive/arXiv

arXiv · 2605.17579

Getting rid of the ghosts: a toy-model of membrane melting

Olivier Coquand

View original source ↗Read source document ↗Export metadata ↓

Abstract

The theory of thermal fluctuations in crystalline membranes is put under scrutiny. In particular, the two critical regimes of the renormalisation group diagram, which are often left out of the discussion because of their instability in one direction, are examined in details. After studying the proper Goldstone mode counting around each of them, the properties of the fluctuations dominating the large scale spectrum are analysed. This shows that the fixed point P2 is a good candidate to describe the melting of a crystalline membrane. The properties of the melted membrane are then compared to the known properties of fluid membranes. As a byproduct of this analysis, we show that the generation of a fluid membrane by melting a bidimensional crystal allows to formulate its correlation functions without being plagued by the ghosts that inevitably show up in the usual Canham-Helfrich action relying on the Monge parametrisation.

Explore related subjects

cond-mat.soft hep-th

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Olivier Coquand. 2026-05-17. Getting rid of the ghosts: a toy-model of membrane melting. https://arxiv.org/abs/2605.17579

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Control of filament network rigidity by the condensation of crowding molecules

Understanding how liquid-liquid phase separation impacts the mechanics of filament networks is a fundamental physical problem at the heart of biological cellular processes and soft material design. While a few theoretical mechanisms have been proposed, a clear demonstration of the direct coupling of phase separation to the overall network stiffness is missing. We report experiments that reveal a universal mechanism by which the condensation of macromolecular crowders induces a rigidity transition in a model filament network. We reconstituted stiff sterically interacting helical filaments and polymeric crowders. Initially, the macromolecules were uniformly dissolved and the filaments formed bundles that assembled a rigid entangled network. Once the crowders condensed into droplets, the network structure lost its rigidity and its mechanical response weakened by an order-of-magnitude. The subsequent dissolution of the condensates was accompanied by the re-establishment of rigidity. Our results show that crowder phase separation modulates the mechanics of filament networks by tuning the osmotic pressure holding the network together. This principle may serve as a paradigm for devising dynamically tunable filamentous materials.

cond-mat.soft↗

arXiv2026

Speed up of passive tracers in mixtures with active chemical reactions

Diffusivity of passive tracers in complex mixtures is widely relevant for industrial applications and for probing biological systems. Interactions with the surrounding medium typically generate a drag force that suppresses tracer diffusion, although self-propulsion can accelerate tracers via active fluctuations. Similar effects are not understood in mixtures with particle conversion and exchange, although these are particularly relevant in biological contexts, where actively driven reactions prevail. By studying a thermodynamically consistent model of chemical reactions in mixtures, we show that reactions provide an additional relaxation pathway that suppresses interaction-induced memory, reducing the drag on tracers and restoring their diffusivity toward the value expected in the absence of solutes. Moreover, active reactions generate nonequilibrium fluctuations that can push tracer diffusivity beyond this limit, an effect we confirm with particle-based simulations. Our results identify chemical activity as a distinct route to controlling mass transport and offer a framework for interpreting microrheology experiments in chemically active mixtures.

cond-mat.soft↗

arXiv2026

Diffusion of charged rods across 3D varying section channels

We analyze the transport of rod-like particles by diffusion and drift in a three-dimensional channel with varying circular or elliptic cross section. Applying the Fick-Jacobs approximation to the transport equation of the particles' probability distribution, we derive an effective one-dimensional substitute model and the associated free energy profile. Our results show that the data for the mean first passage time of rods, once expressed as a function of the effective free energy barrier, collapse onto the same master curve as obtained for point or spherical particles. The observed universality provides a simple framework for predicting transport times of anisotropic particles in confined geometries without resolving the full multidimensional dynamics.

cond-mat.soft↗