Laboratoire Matière et Systèmes Complexes
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439600Séminaire MSC. 8 Juin 2020. Jean Colombani (ILM, Lyon) : "Coffeestain effect with pure water on a soluble substrate"
http://www.msc.univparisdiderot.fr/spip.php?article1061
http://www.msc.univparisdiderot.fr/spip.php?article106120200326T11:51:02Ztext/htmlfrMichaël BerhanuSéminaires 2020Coffeestain effect with pure water on a soluble substrate Jean Colombani Institut Lumière Matière ; Université de Lyon ; Université Claude Bernard Lyon 1 ; CNRS UMR 5306 When the sessile droplet of a complex fluid has evaporated, a ringshaped deposit is left on the substrate (the coffeestain effect). This effect is a consequence of an outward flow inside the droplet, which derives from the pinning of the triple line. We have recently shown that this effect can be observed when a pure (...)

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<div class='rss_texte'><h3 class="spip">Coffeestain effect with pure water on a soluble substrate</h3>
<p><strong><a href='https://jeancolombani.jimdofree.com/' class='spip_out' rel='external'>Jean Colombani</a></strong></p> <p><strong>Institut Lumière Matière ; Université de Lyon ; Université Claude Bernard Lyon 1 ; CNRS UMR 5306
</strong></p> <p>When the sessile droplet of a complex fluid has evaporated, a ringshaped deposit is left on the substrate (the coffeestain effect). This effect is a consequence of an outward flow inside the droplet, which derives from the pinning of the triple line. We have recently shown that this effect can be observed when a pure water drop evaporates on a fast dissolving solid, like salt. In this configuration, the dissolved salt is advected toward the pinned contact line, where the increased evaporation induces the supersaturation of the salt, which leads to the salt crystallization as a thin film, following the interface. This thin shell at the periphery of the drying drop shows shapes varying from inclined walls to hollow halftores.
We have modeled analytically our experiments to understand how the open or closed shape is selected by the droplet radius and contact angle, and to predict the order of magnitude of the shell thickness.
I will present the experimental device, the main results obtained on earth and in microgravity, the flow pattern inside the drop, the phase diagram of the shells and I will introduce briefly the analytical model.</p> <p><span class='spip_document_1205 spip_documents spip_documents_center'>
<img src='http://www.msc.univparisdiderot.fr/local/cachevignettes/L492xH312/image_ferme451d6.png' width='492' height='312' alt="" style='height:312px;width:492px;' /></span></p></div>
Theory Club Friday March 13 at 12:00 in room 412B. Alessandro Manacorda: "A numerical solution for the infinitedimensional dynamics of spheres"
http://www.msc.univparisdiderot.fr/spip.php?article1060
http://www.msc.univparisdiderot.fr/spip.php?article106020200310T21:41:22Ztext/htmlenAndrew CallanJonesSéminaires théorieA numerical solution for the infinitedimensional dynamics of spheres Alessandro Manacorda Abstract: In the last years, a Dynamical MeanField Theory (DMFT) describing the dynamics of shortrange interacting particles in infinite dimensions at equilibrium has been formulated [15]. The infinitedimensional limit of the dynamical equations, obtained as the leading order of a perturbative expansion in 1/d, leads to theoretical predictions concerning the dynamical transition and the critical (...)

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<div class='rss_texte'><p><strong>A numerical solution for the infinitedimensional dynamics of spheres</strong></p> <p>Alessandro Manacorda</p> <p><i>Abstract:</i>
In the last years, a Dynamical MeanField Theory (DMFT) describing the dynamics of shortrange interacting particles in infinite dimensions at equilibrium has been formulated [15]. The infinitedimensional limit of the dynamical equations, obtained as the leading order of a perturbative expansion in 1/d, leads to theoretical predictions concerning the dynamical transition and the critical exponent of the diffusivity. However, an analytical solution of the DMFT equations is out of reach. I will present a numerical solution of the dynamics through a selfconsistent algorithm, applied to hard and soft spheres, considering both overdamped and inertial dynamics [6]. The solution found confirms the theoretical predictions about the dynamical transition at high densities, and leads to new quantitative insights about the dynamical observables of the system, such as the memory kernel and the MSD. The solution for hard spheres is obtained through a nontrivial limit of the soft spheres one. The results both merge and extend kinetic theory and thermodynamics at infinite d, and represent a starting point for the study of several outofequilibrium systems [78].</p> <p>[1] T Maimbourg, J Kurchan & F Zamponi. Phys. Rev. Lett. 116 015902 (2016)
[2] J Kurchan, T Maimbourg & F Zamponi. J. Stat. Mech. 2016.3 033210 (2016)
[3] G Szamel. Phys. Rev. Lett. 119 155502 (2017)
[4] P Charbonneau et al. Annu. Rev. of Cond. Matter Phys. 8 265288 (2017)
[5] G Parisi, P Urbani & F Zamponi. Theory of Simple Glasses: Exact Solutions in Infinite Dimensions. Cambridge University Press (2020)
[6] A Manacorda, G Schehr & F Zamponi. arXiv:2002.09216 (2020)
[7] E Agoritsas, T Maimbourg & F Zamponi. J. Phys. A: Math. Theor. 52 144002 (2019)
[8] E Agoritsas, T Maimbourg & F Zamponi. J. Phys. A: Math. Theor. 52 334001 (2019)</p> <p><strong>Friday March 13 at 12:00 in room 412B</strong></p></div>
Séminaire MSC. David Martin (MSC). "MotilityInduced Solidification in roller Flocks." and
http://www.msc.univparisdiderot.fr/spip.php?article1059
http://www.msc.univparisdiderot.fr/spip.php?article105920200306T10:28:18Ztext/htmlfrMichaël BerhanuSéminaires 2020Date to be determined. MotilityInduced Solidification in roller Flocks David Martin, MSC, Université de Paris The emergence of collective motion is a wellestablished phenomenon in living systems, be it among developed organisms such as fish swarms or starling flocks, or among simpler ones such as bacteria. Although the microscopic mechanisms entailing the transition toward collective motion typically depend on the system, some features are universal, and, as such, can be captured by (...)

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<div class='rss_texte'><p>Date to be determined.</p> <h3 class="spip">MotilityInduced Solidification in roller Flocks</h3>
<p><strong><a href='http://www.msc.univparisdiderot.fr/~dmartin/' class='spip_out'>David Martin</a>, MSC, Université de Paris</strong></p> <p>The emergence of collective motion is a wellestablished phenomenon in living systems, be it among developed organisms such as fish swarms or starling flocks, or among simpler ones such as bacteria. Although the microscopic mechanisms entailing the transition toward collective motion typically depend on the system, some features are universal, and, as such, can be captured by simple microscopic models.
The Vicsek model has proven itself such a minimal description, able to predict important features of flocks further confirmed by different experimental realizations(shaken grains, rollers...). Unfortunately, it does not encompass steric effects and hence fails to describe assemblies at higher densities.</p> <p>A new physics is however expected in such cases, since repulsive forces, by themselves, can trigger phase transitions such as motilityinduced phase separation (MIPS). I will present theoretical and experimental results on how the flocking transition interplays with steric interactions at high density. In particular, I will show how active solids emerge in flocking states made by Quincke colloidal rollers. Particles in the solid are effectively arrested, but the solid collectively propagates upstream due to its rich boundary dynamics.</p> <p><span class='spip_document_1204 spip_documents spip_documents_center'>
<img src='http://www.msc.univparisdiderot.fr/local/cachevignettes/L520xH441/DMartin_e99_2_medium5df38.jpg' width='520' height='441' alt="" style='height:441px;width:520px;' /></span>
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References
[1] D. Geyer, D. Martin, J. Tailleur, D. Bartolo, arXiv:1903.01134 (2019)
[2] D. Geyer, A. Morin, D. Bartolo, Nature materials 17, 789 (2018)</p></div>
Theory Club Wednesday March 11 at 12:00 in room 412B. Yerali Gandica: "Bali ancient rice terraces: A Hamiltonian approach"
http://www.msc.univparisdiderot.fr/spip.php?article1058
http://www.msc.univparisdiderot.fr/spip.php?article105820200306T10:09:05Ztext/htmlenAndrew CallanJonesSéminaires théorieBali ancient rice terraces: A Hamiltonian approach Yerali Gandica Abstract: In this talk, I will present a Hamiltonian approach inspired by the Subak irrigation system. In a previous work, Lansing et al. [1] found out that the clustersize distribution of the rice patches in BaliSubak fields is a powerlaw function with an exponent (approx. 1.9) similar to the one found on Hamiltonian systems. The application of the methods of statistical physics to social phenomena, where the (...)

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<div class='rss_texte'><p><strong>Bali ancient rice terraces: A Hamiltonian approach</strong></p> <p>Yerali Gandica</p> <p><i>Abstract:</i>
In this talk, I will present a Hamiltonian approach inspired by the Subak irrigation system. In a previous work, Lansing et al. [1] found out that the clustersize distribution of the rice patches in BaliSubak fields is a powerlaw function with an exponent (approx. 1.9) similar to the one found on Hamiltonian systems. The application of the methods of statistical physics to social phenomena, where the interacting particles are now interacting human beings, has proved to be very fruitful in allowing for the understanding of many features of human behaviour. In this sense, Universality, which states that the emergent phenomena displayed by the collective behaviour of interacting particles depend on symmetries, dimensionality and conservation laws and not on the microscopic details of the intrinsic dynamics mechanism, seems to be present in many social situations. I will show how the beautiful mosaics characterising several ricegrowing regions in Bali Indonesia, which are the consequence of the selforganising process ruled by the Subak since the 11th century in that tropical island, can be explained by two main mechanisms behind Subak farmers' decisions. Pest stress is the local mechanism promoting order, namely, using the same schedule within neighbouring patches. On the other hand, an antiferromagnetic interaction controlled by water stress is set by a global mechanism, fixing a limit in the total number of cells in the same state. Our Subak Hamiltonian presents two phase transitions, one of them having a critical nature. I will present our first results, general conclusions and consequences of scaping from that critical balance. For the talk, first, I will briefly explain my research line, second my current works, and finally, the Hamiltonian approach.</p> <p>References [1] Adaptive selforganization of Balinese subaks. J. Stephen Lansing, Stefan Thurner, Ning Ning Chung, Aurlie CoudurierCurveur, ail Karaka, Kurt A. Fesenmyer, and Lock Yue Chew. PNAS, 114 (25) 65046509.</p> <p><strong>Wednesday March 11 at 12:00 in room 412B</strong></p></div>
Theory Club Monday March 9 at 12:00 in room 734A. Takahiro Nemoto: "Optimizing interparticle interactions using large deviation theory: from a viewpoint of Bayesian inference with regularization"
http://www.msc.univparisdiderot.fr/spip.php?article1057
http://www.msc.univparisdiderot.fr/spip.php?article105720200306T10:02:03Ztext/htmlenAndrew CallanJonesSéminaires théorieOptimizing interparticle interactions using large deviation theory: from a viewpoint of Bayesian inference with regularization Takahiro Nemoto Abstract: Bayesian inference plays a prominent role in many fields outside physics, such as quantitative political science, epidemiology and bioinformatics, where input data are typically complex, obtained in field researches or experiments. When modeling only essential properties of dynamics, as often important in statistical physics, input data (...)

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<div class='rss_texte'><p><strong>Optimizing interparticle interactions using large deviation theory: from a viewpoint of Bayesian inference with regularization</strong></p> <p>Takahiro Nemoto</p> <p><i>Abstract:</i>
Bayesian inference plays a prominent role in many fields outside physics, such as quantitative political science, epidemiology and bioinformatics, where input data are typically complex, obtained in field researches or experiments. When modeling only essential properties of dynamics, as often important in statistical physics, input data are greatly reduced to just a few variables. In such cases, the Bayesian approach results in nonunique and inconsistent outcomes that are sensitive to the prior. In this talk, I will show a regularization technique based on the large deviation theory, in order to construct a set of priors to get a unique outcome from a single timeaveraged input.</p> <p>We will then apply this Bayesian inference to active Brownian particles with repulsive interactions. In our Bayesian framework, the only input we specify is to reduce the collisions among the particles. The framework then automatically selects (additional) interparticle interactions to achieve this input in an optimal manner. With the help of the population dynamics algorithm, which is a technique used in the large deviation theory, we will perform this inference. We will find that the obtained optimal interparticle interactions produce collective motions, even if the original particles do not have any aligning interactions. In other words, the collective motion will be obtained without explicitly modeling the details of interparticle interactions, but only with a simple and practical input: reducing the collisions among particles within our Bayesian framework.</p> <p>At the end of this talk, I will describe future perspectives of application of this framework in biology and engineering.</p> <p><strong>Monday March 9 at 12:00 in room 734A</strong></p></div>
Séminaire MSC. 25 Mai 2020. Eric Bertin (Liphy, Grenoble). "Breaking of energy equipartition and spatial correlations in outofequilibrium systems."
http://www.msc.univparisdiderot.fr/spip.php?article1056
http://www.msc.univparisdiderot.fr/spip.php?article105620200303T10:21:59Ztext/htmlfrMichaël BerhanuSéminaires 2020Breaking of energy equipartition and spatial correlations in outofequilibrium systems Eric Bertin, CNRS Senior Scientist Laboratoire Interdisciplinaire de Physique (LIPhy), Grenoble Abstract : Energy equipartition is a cornerstone of equilibrium statistical physics. For instance, the average kinetic energy per degree of freedom of a molecule is the same for translational and rotational motions. For (harmonic) interaction energies, equipartition of energy applies to extended modes like (...)

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<div class='rss_texte'><h3 class="spip">
Breaking of energy equipartition and spatial correlations in outofequilibrium systems</h3>
<p><strong><a href='https://wwwliphy.ujfgrenoble.fr/pagesperso/bertin/index.html' class='spip_out' rel='external'>Eric Bertin</a>, CNRS Senior Scientist </strong></p> <p><strong><a href='https://wwwliphy.univgrenoblealpes.fr/' class='spip_out' rel='external'>Laboratoire Interdisciplinaire de Physique (LIPhy)</a>, Grenoble</strong></p> <p>Abstract : Energy equipartition is a cornerstone of equilibrium statistical physics. For instance, the average kinetic energy per degree of freedom of a molecule is the same for translational and rotational motions. For (harmonic) interaction energies, equipartition of energy applies to extended modes like phonons, and not to the degrees of freedom of individual particles. Out of equilibrium, energy equipartition is in general broken, which may lead to enhanced spatial correlations. The formulation in terms of extended modes offers a natural framework to describe these phenomena. As an illustration, two driven systems of experimental relevance will be considered, an epithelial cell monolayer and an AFM cantilever heated by a laser beam. In the cell monolayer, where individual cell motility is correlated over long time scales, equipartition of energy over normal modes is strongly broken, and velocity correlations are present over distances of ten or more cell sizes.</p> <p><span class='spip_document_1203 spip_documents spip_documents_center'>
<img src='http://www.msc.univparisdiderot.fr/local/cachevignettes/L520xH514/Bertin1325a9.jpg' width='520' height='514' alt="" style='height:514px;width:520px;' /></span></p></div>
Theory Club Wednesday March 4 at 12:00 in room 646A. Thibaud Maimbourg: "Some insights on structural glasses from meanfield theory"
http://www.msc.univparisdiderot.fr/spip.php?article1055
http://www.msc.univparisdiderot.fr/spip.php?article105520200303T09:12:37Ztext/htmlenAndrew CallanJonesSéminaires théorieSome insights on structural glasses from meanfield theory Thibaud Maimbourg Abstract: Capturing the nonequilibrium dynamics of interacting systems is arguably one of the greatest challenges in modern physics, where we lack a unified and efficient description of physical phenomena, compared to equilibrium situations where thermodynamics applies. This has justified the focus on particular but paradigmatic classes of systems. One of them is glasses, which are amorphous solids with (...)

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<div class='rss_texte'><p><strong>Some insights on structural glasses from meanfield theory</strong></p> <p>Thibaud Maimbourg</p> <p><i>Abstract:</i>
Capturing the nonequilibrium dynamics of interacting systems is arguably one of the greatest challenges in modern physics, where we lack a unified and efficient description of physical phenomena, compared to equilibrium situations where thermodynamics applies. This has justified the focus on particular but paradigmatic classes of systems. One of them is glasses, which are amorphous solids with intriguing experimental features. They exhibit a wealth of phenomena in their outofequilibrium dynamics (through e.g. a quench or an external drive, such as a shear strain or an active selfpropulsion) at low temperatures. Another such feature occurs at even lower temperatures, where quantum effects start to play a role: thermodynamic quantities display an anomalous behaviour with respect to what one expects from standard (ordered) solids. I will first give a short overview of the meanfield theory of structural glasses, able to unify many physical situations (dense liquids, soft and hard colloids, granular materials, emulsions) and transitions in the same conceptual framework. Then I will review recent results deriving from these ideas to the abovementioned examples. Time permitting I will discuss effective Gibbs equilibrium and its breakdown in the steady state of drivendissipative interacting spin systems, modelling nuclear magnetic resonance protocols.</p> <p><strong>Wednesday March 4 at 12:00 in room 646A</strong></p></div>
Séminaire MSC. 9 Mars 2020. Michiko Shimokawa (Fukuoka Institute of Technology, Japan). "Mode Selection of Breakup of Falling Droplet in Miscible Solution."
http://www.msc.univparisdiderot.fr/spip.php?article1054
http://www.msc.univparisdiderot.fr/spip.php?article105420200302T15:54:20Ztext/htmlfrMichaël BerhanuSéminaires 2020Mode Selection of Breakup of Falling Droplet in Miscible Solution Michiko Shimokawa, Fukuoka Institute of Technology, Japan Abstract : When a droplet with a relatively high density falls into a miscible solution with a relatively low density, the droplet breaks up spontaneously. We investigated the number m of breakup in experiments with several density differences Δρ between two solutions, viscosities μ, and droplet radii r. The mode number m has a distribution even under the same (...)

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<div class='rss_texte'><h3 class="spip">Mode Selection of Breakup of Falling Droplet in Miscible Solution</h3>
<p><strong>Michiko Shimokawa, Fukuoka Institute of Technology, Japan</strong></p> <p>Abstract :
When a droplet with a relatively high density falls into a miscible solution with a relatively low density, the droplet breaks up spontaneously. We investigated the number m of breakup in experiments with several density differences Δρ between two solutions, viscosities μ, and droplet radii r. The mode number m has a distribution even under the same experimental conditions. We propose a simple model of mode selection based on the linear RayleighTaylor instability and the growing radius of a vortex ring deformed from the droplet. The model provides the probability distribution P(m) and a relationship between the nondimensional parameter G∝Δρgr3/μ2 and the average value of m, which are consistent with experimental results. This study is collaborated with Prof. Sakaguchi in Kyushu University.</p> <p><span class='spip_document_1202 spip_documents spip_documents_center'>
<img src='http://www.msc.univparisdiderot.fr/local/cachevignettes/L520xH132/Shimokawa_PhysRevFluids2019_fig3a55a0.jpg' width='520' height='132' alt="" style='height:132px;width:520px;' /></span></p></div>
Theory Club Monday March 2nd at 12:00 in room 734A. Céline Ruscher: "Residual stresses in athermally deformed amorphous solids: insight from atomistic simulations" {{Residual stresses in athermally deformed amorphous solids: insight from atomistic simulations}}
http://www.msc.univparisdiderot.fr/spip.php?article1053
http://www.msc.univparisdiderot.fr/spip.php?article105320200228T20:56:08Ztext/htmlenAndrew CallanJonesSéminaires théorieResidual stresses in athermally deformed amorphous solids: insight from atomistic simulations Céline Ruscher Abstract: Amorphous solids are yieldstress materials that flow when a sufficiently large stress is applied. The emergence of plasticity is associated with local rearrangements of particles in shear transfor mation zones (STs) which interact elastically and can organise spatially in transient or permanent shearbands. Moreover, individual STs can trigger other unstable regions in (...)

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<div class='rss_texte'><p><strong>Residual stresses in athermally deformed amorphous solids: insight from atomistic simulations</strong></p> <p>Céline Ruscher</p> <p><i>Abstract:</i>
Amorphous solids are yieldstress materials that flow when a sufficiently large stress is applied. The emergence of plasticity is associated with local rearrangements of particles in shear transfor mation zones (STs) which interact elastically and can organise spatially in transient or permanent shearbands. Moreover, individual STs can trigger other unstable regions in the glass thus causing collective failure events in the form of avalanches. In the past 5 years, significant progress has been made to link the scaling properties of avalanches to the underlying microscopic properties. Specifically, the distribution of local residual stresses x was proposed to have the form P (x) ∼ xθ in the limit of weak residual stresses [12], which introduces the exponent θ as a nontrivial scaling exponent that controls the distribution of avalanche sizes.
By combining atomistic simulations with the frozen matrix approach [3], we reveal here the evolution of the local residual stress distribution in a 2d binary LennardJones glass upon defor mation [4]. We find a pseudogap form P(x) ∼ xθ, in the freshly quenched state and in the early stages of deformation. After a few percent strain, however, P(x) starts to develop a plateau p0 in the small x limit which scales as p0 ∼ L−p with the system size L in agreement with results from elastoplastic models [56]. A direct comparison with the system size scaling of the stress drops shows that the statistical properties of avalanches are controlled by θ in the transient regime and the plateau exponent p in the steady state flow. The emergence of the plateau is related to the discrete nature of mechanical noise and can be explained through a meanfield model which shows p = θ in the thermodynamic limit [4].
[1] J. Lin, A. Saade, E. Lerner, A. Rosso and M. Wyart, EPL, 105, 26003 (2014).
[2] J. Lin, T. Gueudr, A. Rosso and M. Wyart, Phys. Rev. Lett. 115, 168001 (2015).
[3] P. Sollich, CECAM meeting (2011).
[4] C. Ruscher and J.Rottler, arXiv:1908.01081, (2019)
[5] E. E. Ferrero and E. A. Jagla, Soft Matter 15, 9041 (2019).
[6] B. Tyukodi, D. Vandembroucq and C. E. Maloney, Phys. Rev. E 100, 043003 (2019).</p> <p><strong>Monday March 2nd at 12:00 in room 734A</strong></p></div>
Theory Club Thursday February 27 at 13:30 in room 412B. Aurélien Grabsch: "Truncated linear statistics associated with the top eigenvalues of random matrices and application to an interface model"
http://www.msc.univparisdiderot.fr/spip.php?article1052
http://www.msc.univparisdiderot.fr/spip.php?article105220200224T18:51:18Ztext/htmlenAndrew CallanJonesSéminaires théorieTruncated linear statistics associated with the top eigenvalues of random matrices and application to an interface model Aurélien Grabsch Abstract: Since the pioneer work of Wigner, random matrix theory has been applied to many fields. Invariant ensembles, in which eigenvalues and eigenvectors are uncorrelated, have played a prominent role in physical applications. Many important physical observables take the form of linear statistics of eigenvalues $\\lambda_i\_i=1,\ldots,N$, i.e. $L = (...)

<a href="http://www.msc.univparisdiderot.fr/spip.php?rubrique331" rel="directory">Séminaires théorie</a>
<div class='rss_texte'><p><strong>Truncated linear statistics associated with the top eigenvalues of random matrices and application to an interface model</strong></p> <p>Aurélien Grabsch</p> <p><i>Abstract:</i>
Since the pioneer work of Wigner, random matrix theory has been applied to many fields. Invariant ensembles, in which eigenvalues and eigenvectors are uncorrelated, have played a prominent role in physical applications. Many important physical observables take the form of linear statistics of eigenvalues $\<i>\lambda_i\</i>_<i>i=1,\ldots,N</i>$, i.e. $L = \sum_<i>i=1</i>^N f(\lambda_i)$, where $N$ is the total number of eigenvalues and $f$ is any given function depending on the physical situation under consideration.
We have recently introduced a new type of problem: motivated by the analysis of the statistical physics of fluctuating onedimensional interfaces, we have studied the distribution of truncated linear statistics $\tilde<i>L</i>=\sum_<i>i=1</i>^K f(\lambda_i)$, where the summation is restricted to the $K < N$ largest eigenvalues.
In this talk I will analyse the distribution of these truncated linear statistics, in the limit $N \to \infty$ with $K/N$ fixed, using the Coulomb gas technique. I will show that the constraint that $\tilde<i>L</i>=\sum_<i>i=1</i>^K f(\lambda_i)$ is fixed drives an infinite order phase transition in the underlying Coulomb gas. This transition corresponds to a change in the density of the gas, from a density defined on two disjoint intervals to a single interval. In this latter case the density presents a logarithmic divergence inside the bulk.</p> <p><strong>Thursday February 27 at 13:30 in room 412B</strong></p></div>