arXiv subjects

O. Coquand

Publications and source records attributed to O. Coquand.

12 recordsLinked to original sources

arXiv2026

The effect of water on granular liquid flows: from debris to mud flows

In this work, we show how the rheology of granular suspensions can be related to the properties of the fluctuations of the velocity field inside the medium. In particular, effective Navier-Stokes equations in the different flow regimes are constructed and compared to an actual geophysical model that was so far purely phenomenological. Then, it is shown that a direct cascade of kinetic energy is present when the flow becomes turbulent, but with a scaling law that is quantitatively very different from that of usual Newtonian fluids.

cond-mat.soft↗

arXiv2025

Energy Cascades in Driven Granular Liquids : A new Universality Class? I : Model and Symmetries

This article deals with the existence and scaling of an energy cascade in steady granular liquid flows between the scale at which the system is forced and the scale at which it dissipates energy. In particular, we examine the possible origins of a breaking of the Kolmogorov Universality class that applies to Newtonian liquids under similar conditions. In order to answer these questions, we build a generic field theory of granular liquid flows and, through a study of its symmetries, show that indeed the Kolmogorov scaling can be broken, although most of the symmetries of the Newtonian flows are preserved.

cond-mat.soft↗

arXiv2024

The Liquid-Gas Transition in Granular Matter : a Question of Effective Friction ?

This work presents a comparative study of the best models available to describe granular fluids in order to investigate the extent to which it makes sense to speak about a liquid-gas transition in a system of particles that present no attractive interactions. It is shown that the gas and the liquid correspond to regimes with clearly distinct rheological responses. A microscopic interpretation of what happens at the transition in terms of the time scales relevant to the various physical processes is also presented and put the test against numerical data. Our work calls for more experiments to test our predictions on real systems.

cond-mat.soft↗

arXiv2021

Dynamical yield criterion for granular matter from first principles

We investigate, using a recently developed model of liquid state theory describing the rheology of dense granular flows, how a yield stress appears in granular matter at the yielding transition. Our model allows us to predict an analytical equation of the corresponding dynamical yield surface, which is compared to usual models of solid fracture. In particular, this yield surface interpolates between the typical failure behaviors of soft and hard materials. This work also underlines the central role played by the effective friction coefficient at the yielding transition.

cond-mat.soft↗

arXiv2021

Wrinkling transition in quenched disordered membranes at two loops

One investigates the flat phase of quenched disordered polymerized membranes by means of a two-loop, weak-coupling computation performed near their upper critical dimension $D_{uc} = 4$, generalizing the one-loop computation of Morse, Lubensky and Grest [Phys. Rev. A 45, R2151 (1992), Phys. Rev. A 46, 1751 (1992)]. Our work confirms the existence of the finite-temperature, finite-disorder, wrinkling transition, which has been recently identified by Coquand et al. [Phys. Rev E 97, 030102 (2018)] using a nonperturbative renormalization group approach. One also points out ambiguities in the two-loop computation that prevent the exact identification of the properties of the novel fixed point associated with the wrinkling transition, which very likely requires a three-loop order approach.

cond-mat.dis-nn↗

arXiv2020

The flat phase of polymerized membranes at two-loop order

We investigate two complementary field-theoretical models describing the flat phase of polymerized - phantom - membranes by means of a two-loop, weak-coupling, perturbative approach performed near the upper critical dimension $D_{uc}=4$, extending the one-loop computation of Aronovitz and Lubensky [Phys. Rev. Lett. 60, 2634 (1988)]. We derive the renormalization group equations within the modified minimal substraction scheme, then analyze the corrections coming from two-loop with a particular attention paid to the anomalous dimension and the asymptotic infrared properties of the renormalization group flow. We finally compare our results to those provided by nonperturbative techniques used to investigate these two models.

cond-mat.stat-mech↗

arXiv2020

Temperature Expansions in the Square-Shoulder Fluid I: the Wiener-Hopf Function

We investigate the spatial structure of dense square-shoulder fluids. To this end we derive analytical perturbative solutions of the Ornstein-Zernike equation in the low- and high-temperature limits as expansions around the known hard sphere solutions. We then discuss the suitability of perturbative approaches in relation to the Ornstein-Zernike equation.

cond-mat.stat-mech↗

arXiv2020

Temperature Expansions in the Square Shoulder Fluid II: Thermodynamics

In a companion paper, we derived analytical expressions for the structure factor of the square-shoulder potential in a perturbative way around the high- and low-temperature regimes. Here, various physical properties of these solutions are derived. In particular, we investigate the large wave number sector, and relate it to the contact values of the pair-correlation function. Then, thermoelastic properties of the square-shoulder fluids are discussed.

cond-mat.soft↗

arXiv2020

Universal behaviors in the wrinkling transition of disordered membranes

The wrinkling transition experimentally identified by Mutz et al. [Phys. Rev. Lett. 67, 923 (1991)] and then thoroughly studied by Chaieb et al. [Phys. Rev. Lett. 96, 078101 (2006)] in partially polymerized lipid membranes is reconsidered. One shows that the features associated with this transition, notably the various scaling behaviors of the height-height correlation functions that have been observed, are qualitatively and quantitatively well described by a recent nonperturbative renormalization group (NPRG) approach to quenched disordered membranes by Coquand et al. [Phys. Rev E 97, 030102 (2018)]. As these behaviors are associated with fixed points of RG transformations they are universal and should also be observed in, e.g., defective graphene and graphene-like materials.

cond-mat.soft↗

arXiv2019

Spontaneous symmetry breaking and the flat phase of crystalline membranes

Crystalline membranes are one of the rare examples of bidimensional systems in which long-range order can stabilise an ordered phase in the thermodynamic limit. By a careful analysis of the Goldstone modes counting, we propose a symmetry breaking mechanism associated with the generation of the flat phase and show how it highlights the crucial role played by the crystalline lattice in the establishment of long-range order in these objects. Comparison with other symmetry breaking mechanisms in membrane physics is also used to unveil the links between symmetry breaking patterns and the physical properties of the flat phase.

cond-mat.stat-mech↗

arXiv2018

A glassy phase in quenched disordered graphene and crystalline membranes

We investigate the flat phase of $D$-dimensional crystalline membranes embedded in a $d$-dimensional space and submitted to both metric and curvature quenched disorders using a nonperturbative renormalization group approach. We identify a second order phase transition controlled by a finite-temperature, finite-disorder fixed point unreachable within the leading order of $ε=4-D$ and $1/d$ expansions. This critical point divides the flow diagram into two basins of attraction: that associated to the finite-temperature fixed point controlling the long distance behaviour of disorder-free membranes and that associated to the zero-temperature, finite-disorder fixed point. Our work thus strongly suggests the existence of a whole low-temperature glassy phase for quenched disordered graphene, graphene-like compounds and, more generally, crystalline membranes.

cond-mat.dis-nn↗

arXiv2016

The flat phase of quantum polymerized membranes

We investigate the flat phase of quantum polymerized phantom membranes by means of a nonperturbative renormalization group approach. We first implement this formalism for general quantum polymerized membranes and derive the flow equations that encompass both quantum and thermal fluctuations. We then deduce and analyze the flow equations relevant to study the flat phase and discuss their salient features : quantum to classical crossover and, in each of these regimes, strong to weak coupling crossover. We finally illustrate these features in the context of free standing graphene physics.

cond-mat.stat-mech↗