Giulio Biroli

Campus Paris Saclay, Lutetia Parisorum, Île-de-France, France

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Publications (133)474.49 Total impact

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    Saroj Nandi · Giulio Biroli · Gilles Tarjus
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    ABSTRACT: Motivated by the connection between the dynamical transition predicted by the mean-field theory of glass-forming liquids and the spinodal of an Ising model in a quenched random field (RFIM) beyond mean-field, we revisit the phenomenon of spinodals in the presence of quenched disorder and develop a complete theory for it. By working at zero temperature in the quasi-statically driven RFIM, thermal fluctuations are eliminated and one can give a rigorous content to the notion of spinodal. We show that the spinodal transition is due to the depinning and the subsequent expansion of rare droplets. We work out the critical behavior, which, in any finite dimension, is very different from the mean-field one: the characteristic length diverges exponentially and the thermodynamic quantities display very mild non-analyticities much like in a Griffith phenomenon. On the basis of our results we assess the physical content and the status of the dynamical transition predicted by the mean-field theory of glassy dynamics.
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    ABSTRACT: Slow dynamics in glassy systems is often interpreted as due to thermally activated events between "metastable" states. This emphasizes the role of nonperturbative fluctuations, which is especially dramatic when these fluctuations destroy a putative phase transition predicted at the mean-field level. To gain insight into such hard problems, we consider the implementation of a generic back-and-forth process, between microscopic theory and observable behavior via effective theories, in a toy model that is simple enough to allow for a thorough investigation: the one-dimensional $\varphi^4$ theory at low temperature. We consider two ways of restricting the extent of the fluctuations, which both lead to a nonconvex effective potential (or free energy) : either through a finite-size system or by means of a running infrared cutoff within the nonperturbative Renormalization Group formalism. We discuss the physical insight one can get and the ways to treat strongly nonperturbative fluctuations in this context.
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    Elena Tarquini · Giulio Biroli · Marco Tarzia
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    ABSTRACT: This work provide a thorough study of L\'evy or heavy-tailed random matrices (LM). By analysing the self-consistent equation on the probability distribution of the diagonal elements of the resolvent we establish the equation determining the localisation transition and obtain the phase diagram of LMs. Using arguments based on super-symmetric field theory and Dyson Brownian motion we show that the eigenvalue statistics is the same one of the Gaussian Orthogonal Ensemble in the whole delocalised phase and is Poisson in the localised phase. Our numerics confirms these findings, valid in the limit of infinitely large LMs, but also reveals that the characteristic scale governing finite size effects diverges much faster than a power law approaching the transition and is already very large far from it. This leads to a very wide cross-over region in which the system looks as if it were in a mixed phase. Our results, together with the ones obtained previously, provide now a complete theory of L\'evy matrices.
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    Giulio Biroli · Chiara Cammarota
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    ABSTRACT: We develop a theory of amorphous interfaces in glass-forming liquids. We show that the statistical properties of these surfaces, which separate regions characterized by different amorphous arrangements of particles, coincide with the ones of domain walls in the random field Ising model. A major consequence of our results is that super-cooled liquids are characterized by two different static lengths: the point-to-set $\xi_{PS}$ which is a measure of the spatial extent of cooperative rearranging regions and the wandering length $\xi_\perp$ which is related to the fluctuations of their shape. We find that $\xi_\perp$ grows when approaching the glass transition but slower than $\xi_{PS}$. The wandering length increases as $s_c^{-1/2}$, where $s_c$ is the configurational entropy. Our results strengthen the relationship with the random field Ising model found in recent works. They are in agreement with previous numerical studies of amorphous interfaces and provide a theoretical framework for explaining numerical and experimental findings on pinned particle systems and static lengths in glass-forming liquids.
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    Pierfrancesco Urbani · Giulio Biroli
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    ABSTRACT: Recent works on hard spheres in the limit of infinite dimensions revealed that glass states, envisioned as meta-basins in configuration space, can break up in a multitude of separate basins at low enough temperature or high enough pressure, leading to the emergence of new kinds of soft-modes and unusual properties. In this paper we study by perturbative renormalisation group techniques the fate of this transition, which has been discovered in disordered mean-field models in the '80s. We find that the upper critical dimension d_u above which mean-field results hold is strictly larger than six and apparently non-universal, i.e. system dependent. Below d_u, we do not find any perturbative attractive fixed point (except for a tiny region of the 1RSB breaking parameter), thus showing that the transition in three dimensions either does not exist or changes nature from its mean-field counterpart. We also discuss some issues related to the low temperature full replica symmetry breaking phase found in infinite dimensions, as well as a possible relationship with the behavior of spin glasses in a field.
    Physical Review B 10/2014; 91(10). DOI:10.1103/PhysRevB.91.100202 · 3.74 Impact Factor
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    Maria Chiara Angelini · Giulio Biroli
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    ABSTRACT: By using real space renormalisation group (RG) methods we show that spin-glasses in a field display a new kind of transition in high dimensions. The corresponding critical properties and the spin-glass phase are governed by two non-perturbative zero temperature fixed points of the RG flow. We compute the critical exponents, discuss the RG flow and its relevance for three dimensional systems. The new spin-glass phase we discovered has unusual properties, which are intermediate between the ones conjectured by droplet and full replica symmetry breaking theories. These results provide a new perspective on the long-standing debate about the behaviour of spin-glasses in a field.
    Physical Review Letters 09/2014; 114(9). DOI:10.1103/PhysRevLett.114.095701 · 7.51 Impact Factor
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    Maria Chiara Angelini · Giulio Biroli
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    ABSTRACT: We introduce a new disordered system, the Super-Potts model, which is a more frustrated version of the Potts glass. Its elementary degrees of freedom are variables that can take M values and are coupled via pair-wise interactions. Its exact solution on a completely connected lattice demonstrates that for large enough M it belongs to the class of mean-field systems solved by a one step replica symmetry breaking Ansatz. Numerical simulations by the parallel tempering technique show that in three dimensions it displays a phenomenological behaviour similar to the one of glass-forming liquids. The Super-Potts glass is therefore the first long-sought disordered model allowing one to perform extensive and detailed studies of the Random First Order Transition in finite dimensions. We also discuss its behaviour for small values of M, which is similar to the one of spin-glasses in a field.
    Physical Review B 07/2014; 90(22). DOI:10.1103/PhysRevB.90.220201 · 3.74 Impact Factor
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    ABSTRACT: We analyse, using Inhomogenous Mode-Coupling Theory, the critical scaling behaviour of the dynamical susceptibility at a distance epsilon from continuous second-order glass transitions. We find that the dynamical correlation length xi behaves generically as epsilon^{-1/3} and that the upper critical dimension is equal to six. More surprisingly, we find activated dynamic scaling, where xi grows with time as [ln(t)]^2 exactly at criticality. All these results suggest a deep analogy between the glassy behaviour of attractive colloids or randomly pinned supercooled liquids and that of the Random Field Ising Model.
    Physical Review Letters 01/2014; 113(24). DOI:10.1103/PhysRevLett.113.245701 · 7.51 Impact Factor
  • Giulio Biroli · Jean-Philippe Bouchaud
    Physics 11/2013; 6. DOI:10.1103/Physics.6.128
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    Giulio Biroli · Smarajit Karmakar · Itamar Procaccia
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    ABSTRACT: The dramatic dynamic slowing down associated with the glass transition is considered by many to be related to the existence of a static length scale that grows when temperature decreases. Defining, identifying, and measuring such a length is a subtle problem. Recently, two proposals, based on very different insights regarding the relevant physics, were put forward. One approach is based on the point-to-set correlation technique and the other on the scale where the lowest eigenvalue of the Hessian matrix becomes sensitive to disorder. Here we present numerical evidence that the two approaches might result in the same identical length scale. This provides mutual support for their relevance and, at the same time, raises interesting theoretical questions, discussed in the conclusion.
    Physical Review Letters 10/2013; 111(16):165701. DOI:10.1103/PhysRevLett.111.165701 · 7.51 Impact Factor
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    ABSTRACT: We introduce an approach to derive an effective scalar field theory for the glass transition; the fluctuating field is the overlap between equilibrium configurations. We apply it to the case of constrained liquids for which the introduction of a conjugate source to the overlap field was predicted to lead to an equilibrium critical point. We show that the long-distance physics in the vicinity of this critical point is in the same universality class as that of a paradigmatic disordered model: the random-field Ising model. The quenched disorder is provided here by a reference equilibrium liquid configuration. We discuss to what extent this field-theoretical description and the mapping to the random field Ising model hold in the whole supercooled liquid regime, in particular near the glass transition.
    Physical Review Letters 09/2013; 112(17). DOI:10.1103/PhysRevLett.112.175701 · 7.51 Impact Factor
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    ABSTRACT: In this work, we numerically investigate a new method for the characterization of growing length scales associated with spatially heterogeneous dynamics of glass-forming liquids. This approach, motivated by the formulation of the inhomogeneous mode-coupling theory (IMCT) [Biroli, G.; et al. Phys. Rev. Lett. 2006 97, 195701], utilizes inhomogeneous molecular dynamics simulations in which the system is perturbed by a spatially modulated external potential. We show that the response of the two-point correlation function to the external field allows one to probe dynamic correlations. We examine the critical properties shown by this function, in particular, the associated dynamic correlation length, that is found to be comparable to the one extracted from standardly employed four-point correlation functions. Our numerical results are in qualitative agreement with IMCT predictions but suggest that one has to take into account fluctuations not included in this mean-field approach to reach quantitative agreement. Advantages of our approach over the more conventional one based on four-point correlation functions are discussed.
    The Journal of Physical Chemistry B 07/2013; 117(42). DOI:10.1021/jp4035419 · 3.30 Impact Factor
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    Chiara Cammarota · Giacomo Gradenigo · Giulio Biroli
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    ABSTRACT: We study the effect of confinement on glassy liquids using Random First Order Transition theory as framework. We show that the characteristic length-scale above which confinement effects become negligible is related to the point-to-set length-scale introduced to measure the spatial extent of amorphous order in super-cooled liquids. By confining below this characteristic size, the system becomes a glass. Eventually, for very small sizes, the effect of the boundary is so strong that any collective glassy behavior is wiped out. We clarify similarities and differences between the physical behaviors induced by confinement and by pinning particles outside a spherical cavity (the protocol introduced to measure the point-to-set length). Finally, we discuss possible numerical and experimental tests of our predictions.
    Physical Review Letters 05/2013; 111(10). DOI:10.1103/PhysRevLett.111.107801 · 7.51 Impact Factor
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    Atsushi Ikeda · Ludovic Berthier · Giulio Biroli
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    ABSTRACT: We characterize vibrational motion occurring at low temperatures in dense suspensions of soft repulsive spheres over a broad range of volume fractions encompassing the jamming transition at (T = 0, ϕ = ϕJ). We find that characteristic time and length scales of thermal vibrations obey critical scaling in the vicinity of the jamming transition. We show in particular that the amplitude and the time scale of dynamic fluctuations diverge symmetrically on both sides of the transition, and directly reveal a diverging correlation length. The critical region near ϕJ is divided in three different regimes separated by a characteristic temperature scale T(⋆)(ϕ) that vanishes quadratically with the distance to ϕJ. While two of them, (T < T(⋆)(ϕ), ϕ > ϕJ) and (T < T(⋆)(ϕ), ϕ < ϕJ), are described by harmonic theories developed in the zero temperature limit, the third one for T > T(⋆)(ϕ) is inherently anharmonic and displays new critical properties. We find that the quadratic scaling of T(⋆)(ϕ) is due to nonperturbative anharmonic contributions, its amplitude being orders of magnitude smaller than the perturbative prediction based on the expansion to quartic order in the interactions. Our results show that thermal vibrations in colloidal assemblies directly reveal the critical nature of the jamming transition. The critical region, however, is very narrow and has not yet been attained experimentally, even in recent specifically-dedicated experiments.
    The Journal of Chemical Physics 03/2013; 138(12):12A507. DOI:10.1063/1.4769251 · 3.12 Impact Factor
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    Giulio Biroli · Juan P Garrahan
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    ABSTRACT: We provide here a brief perspective on the glass transition field. It is an assessment, written from the point of view of theory, of where the field is and where it seems to be heading. We first give an overview of the main phenomenological characteristics, or "stylised facts," of the glass transition problem, i.e., the central observations that a theory of the physics of glass formation should aim to explain in a unified manner. We describe recent developments, with a particular focus on real space properties, including dynamical heterogeneity and facilitation, the search for underlying spatial or structural correlations, and the relation between the thermal glass transition and athermal jamming. We then discuss briefly how competing theories of the glass transition have adapted and evolved to account for such real space issues. We consider in detail two conceptual and methodological approaches put forward recently, that aim to access the fundamental critical phenomenon underlying the glass transition, be it thermodynamic or dynamic in origin, by means of biasing of ensembles, of configurations in the thermodynamic case, or of trajectories in the dynamic case. We end with a short outlook.
    The Journal of Chemical Physics 03/2013; 138(12):12A301. DOI:10.1063/1.4795539 · 3.12 Impact Factor
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    Chiara Cammarota · Giulio Biroli
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    ABSTRACT: We present a detailed analysis of glass transitions induced by pinning particles at random from an equilibrium configuration. We first develop a mean-field analysis based on the study of p-spin spherical disordered models and then obtain the three-dimensional critical behavior by the Migdal-Kadanoff real space renormalization group method. We unveil the important physical differences with the case in which particles are pinned from a random (or very high temperature) configuration. We contrast the pinning particles approach to the ones based on biasing dynamical trajectories with respect to their activity and on coupling to equilibrium configurations. Finally, we discuss numerical and experimental tests.
    The Journal of Chemical Physics 03/2013; 138(12):12A547. DOI:10.1063/1.4790400 · 3.12 Impact Factor
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    ABSTRACT: We give an overview of our recent works in which the a.c. nonlinear dielectric response of an archetypical glassformer (glycerol) was measured close to its glass transition temperature T g . The purpose was to investigate the prediction that the nonlinear susceptibility is directly related to the number of dynamically correlated molecules N { corr} (T). We explain that two nonlinear susceptibilities are available, namely χ3 (3) and χ3 (1), which correspond respectively to the nonlinear cubic response at the third harmonics and at the first harmonics. We describe how to measure these nonlinear responses, even if they yield signals much smaller than that of the linear response. We show that both \vert {χ }3^{(3)}(ω,T)\vert and \vert {χ }3^{(1)}(ω,T)\vert are peaked as a function of the angular frequency ω and mainly obeys critical scaling as a function of ωτα(T), where τα(T) is the relaxation time of the liquid. Both χ3 (3) and χ3 (1) decay with the same power-law of ω beyond the peak. The height of the peak increases as the temperature approaches T g : This yields an accurate determination of the temperature dependence of N { corr} (T), once the contribution of saturation of dipoles is disentangled from that of dynamical glassy correlations.
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    ABSTRACT: We show that non-interacting disordered electrons on a Bethe lattice display a new intermediate phase which is delocalized but non-ergodic, i.e. it is characterized by Poisson instead of GOE statistics. The physical signature of this phase is a very heterogenous transport that proceeds over a few disorder dependent paths only. We show that the transition to the usual ergodic delocalized phase, which takes place for a disorder strength smaller than the one leading to the localization transition, is related to the freezing-glass transition of directed polymers in random media. The numerical study of level and eigenstate statistics, and of the singular properties of the probability distribution of the local density of states all support the existence of this new intermediate phase. Our results suggest that the localization transition may change nature in high dimensional systems.
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    Bruno Sciolla · Giulio Biroli
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    ABSTRACT: Several mean-field computations have revealed the existence of an out of equilibrium dynamical transition induced by quantum quenching an isolated system starting from its symmetry broken phase. In this work we focus on the quantum phi^4 N-component field theory. By taking into account dynamical fluctuations at the Hartree-Fock level, corresponding to the leading order of the 1/N expansion, we derive the critical properties of the dynamical transition beyond mean-field theory (including at finite temperature). We find diverging time and length-scales, dynamic scaling and aging. Finally, we unveil a relationship with coarsening, an off-equilibrium dynamical regime that can be induced by quenching from the symmetric toward the symmetry broken phase.
    Physical Review B 11/2012; 88(20). DOI:10.1103/PhysRevB.88.201110 · 3.74 Impact Factor
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    C Brun · F Ladieu · D L'hôte · G Biroli · J-P Bouchaud
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    ABSTRACT: We have measured, as a function of the age $t_a$, the aging of the nonlinear dielectric susceptibility $\chi_3$ of glycerol below the glass transition. Whereas the linear susceptibility can be accurately accounted for in terms of an age dependent relaxation time $\tau_{\alpha}(t_a)$, this scaling breaks down for $\chi_3$, suggesting an increase of the amplitude of $\chi_3$. This is a strong indication that the number $N_{corr}$ of molecules involved in relaxation events increases with $t_a$. For $T=0.96 \times T_g$, we find that $N_{corr}$ increases by $\sim 10%$ when $t_a$ varies from $1\mathrm{ks}$ to $100\mathrm{ks}$. This sheds new light on the relation between length scales and time scales in glasses.
    Physical Review Letters 10/2012; 109(17):175702. DOI:10.1103/PhysRevLett.109.175702 · 7.51 Impact Factor

Publication Stats

5k Citations
474.49 Total Impact Points

Institutions

  • 2014
    • Campus Paris Saclay
      Lutetia Parisorum, Île-de-France, France
  • 2004–2014
    • Cea Leti
      Grenoble, Rhône-Alpes, France
    • Institute of Geophysics, China Earthquake Administration
      Peping, Beijing, China
  • 1999–2014
    • French National Centre for Scientific Research
      • Laboratoire Statistique et Génome
      Lutetia Parisorum, Île-de-France, France
  • 2011–2012
    • Atomic Energy and Alternative Energies Commission
      • Institut de Physique Théorique (IPhT)
      Gif-sur-Yvette, Ile-de-France, France
  • 2002
    • Université Paris-Sud 11
      • Laboratoire de Physique Théorique et Modèles Statistiques
      Orsay, Île-de-France, France
  • 2001–2002
    • Rutgers, The State University of New Jersey
      • Department Physics and Astronomy
      New Brunswick, New Jersey, United States
  • 1999–2001
    • Ecole Normale Supérieure de Paris
      • Laboratoire de Physique Théorique
      Paris, Ile-de-France, France