Summary
Statistical network modelling has focused on representing the graph as a discrete structure, namely the adjacency matrix. When assuming exchangeability of this array—which can aid in modelling, computations and theoretical analysis—the Aldous–Hoover theorem informs us that the graph is necessarily either dense or empty. We instead consider representing the graph as an exchangeable random measure and appeal to the Kallenberg representation theorem for this object. We explore using completely random measures (CRMs) to define the exchangeable random measure, and we show how our CRM construction enables us to achieve sparse graphs while maintaining the attractive properties of exchangeability. We relate the sparsity of the graph to the Levy measure defining the CRM. For a specific choice of CRM, our graphs can be tuned from dense to sparse on the basis of a single parameter. We present a scalable Hamiltonian Monte Carlo algorithm for posterior inference, which we use to analyse network properties in a range of real data sets, including networks with hundreds of thousands of nodes and millions of edges.

Sparse graphs using exchangeable random measures

This paper presents an opportunity for the uncertainty that has plagued the novel's criticism to appear as absences in the body of historical knowledge, particularly regarding the notion of life after death. Taking appearance (eg. proof of existence), as opposed to disappearance, as a universally accepted value allows this analysis to interrogate the novel's logic in relation to a variety of conventional systems whose very existence depends on the reproduction of their systems. The ineffectuality of Foucauldian disciplinary institutions in the novel establishes the threat of nonexistence. A significant relationship to Dante's Inferno is rendered, lending the appearance of language an 'enchanted' value through allusions to Dante's intentional invocation of Augustinian corporeal vision. The novel's metalanguage appears enchanted by the body of historical knowledge, particularly as the product of capitalism, discipline and Judeo-Christianity, and programmed by literary precursors William S. Burroughs, Gertrude Stein and Ernest Hemingway. Foregrounded by this complex network, an analysis of the novel’s first chapter demonstrates how an attention to appearance brings the language to life and draws the narrator, equally invested in appearance, into its realm of representation.

Will To Appear

We endow the $\sqrt{8/3}$-Liouville quantum gravity sphere with a metric space structure and show that the resulting metric measure space agrees in law with the Brownian map Recall that a Liouville quantum gravity sphere is a priori naturally parameterized by the Euclidean sphere ${\mathbf S}^2$ Previous work in this series used quantum Loewner evolution (QLE) to construct a metric $d_{\mathcal Q}$ on a countable dense subset of ${\mathbf S}^2$ Here we show that $d_{\mathcal Q}$ as extends uniquely and continuously to a metric $\bar{d}_{\mathcal Q}$ on all of ${\mathbf S}^2$ Letting $d$ denote the Euclidean metric on ${\mathbf S}^2$, we show that the identity map between $({\mathbf S}^2, d)$ and $({\mathbf S}^2, \bar{d}_{\mathcal Q})$ is as Holder continuous in both directions We establish several other properties of $({\mathbf S}^2, \bar{d}_{\mathcal Q})$, culminating in the fact that (as a random metric measure space) it agrees in law with the Brownian map We establish analogous results for the Brownian disk and plane Our proofs involve new estimates on the size and shape of QLE balls and related quantum surfaces, as well as a careful analysis of $({\mathbf S}^2, \bar{d}_{\mathcal Q})$ geodesics

Liouville quantum gravity and the Brownian map II: geodesics and continuity of the embedding

Previous works in this series have shown that an instance of a $\sqrt{8/3}$-Liouville quantum gravity (LQG) sphere has a well-defined distance function, and that the resulting metric measure space (mm-space) agrees in law with the Brownian map (TBM). In this work, we show that given just the mm-space structure, one can a.s. recover the LQG sphere. This implies that there is a canonical way to parameterize an instance of TBM by the Euclidean sphere (up to Mobius transformation). In other words, an instance of TBM has a canonical conformal structure. 
The conclusion is that TBM and the $\sqrt{8/3}$-LQG sphere are equivalent. They ultimately encode the same structure (a topological sphere with a measure, a metric, and a conformal structure) and have the same law. From this point of view, the fact that the conformal structure a.s. determines the metric and vice-versa can be understood as a property of this unified law. The results of this work also imply that the analogous facts hold for Brownian and $\sqrt{8/3}$-LQG surfaces with other topologies.

Liouville quantum gravity and the Brownian map III: the conformal structure is determined

In this work, we study asymptotics of the genealogy of Galton--Watson processes conditioned on the total progeny. We consider a fixed, aperiodic and critical offspring distribution such that the rescaled Galton--Watson processes converges to a continuous-state branching process (CSBP) with a stable branching mechanism of index $\alpha \in (1, 2]$. We code the genealogy by two different processes: the contour process and the height process that Le Gall and Le Jan recently introduced \cite{LGLJ1, LGLJ1}. We show that the rescaled height process of the corresponding Galton--Watson family tree, with one ancestor and conditioned on the total progeny, converges in a functional sense, to a new process: the normalized excursion of the continuous height process associated with the $\alpha $-stable CSBP. We deduce from this convergence an analogous limit theorem for the contour process. In the Brownian case $\alpha =2$, the limiting process is the normalized Brownian excursion that codes the continuum random tree: the result is due to Aldous who used a different method.

A limit theorem for the contour process of conditioned Galton-Watson trees

The Schelling model of segregation, introduced by Schelling in 1969 as a model for residential segregation in cities, describes how populations of multiple types self-organize to form homogeneous clusters of one type. In this model, vertices in an N-dimensional lattice are initially assigned types randomly. As time evolves, the type at a vertex v has a tendency to be replaced with the most common type within distance w of v. We present the first mathematical description of the dynamical scaling limit of this model as w tends to infinity and the lattice is correspondingly rescaled. We do this by deriving an integro-differential equation for the limiting Schelling dynamics and proving almost sure existence and uniqueness of the solutions when the initial conditions are described by white noise. The evolving fields are in some sense very “rough” but we are able to make rigorous sense of the evolution. In a key lemma, we show that for certain Gaussian fields h, the supremum of the occupation density of $$h-\phi $$ at zero (taken over all 1-Lipschitz functions $$\phi $$) is almost surely finite, thereby extending a result of Bass and Burdzy. In the one dimensional case, we also describe the scaling limit of the limiting clusters obtained at time infinity, thereby resolving a conjecture of Brandt, Immorlica, Kamath, and Kleinberg.

Scaling limits of the Schelling model

Let $\gamma \in (0,2)$ and let $h$ be the random distribution on $\mathbb C$ which describes a $\gamma$-Liouville quantum gravity (LQG) cone. Also let $\kappa = 16/\gamma^2 >4$ and let $\eta$ be a whole-plane space-filling SLE$_\kappa$ curve sampled independent from $h$ and parametrized by $\gamma$-quantum mass with respect to $h$. We study a family $\{\mathcal G^\epsilon\}_{\epsilon>0}$ of planar maps associated with $(h, \eta)$ called the \textit{LQG structure graphs} (a.k.a.\ \textit{mated-CRT maps}) which we conjecture converge in probability in the scaling limit with respect to the Gromov-Hausdorff topology to a random metric space associated with $\gamma$-LQG. 
In particular, $\mathcal G^\epsilon$ is the graph whose vertex set is $\epsilon \mathbb Z$, with two such vertices $x_1,x_2\in \epsilon \mathbb Z$ connected by an edge if and only if the corresponding curve segments $\eta([x_1-\epsilon , x_1])$ and $\eta([x_2-\epsilon,x_2])$ share a non-trivial boundary arc. Due to the peanosphere description of SLE-decorated LQG due to Duplantier, Miller, and Sheffield (2014), the graph $\mathcal G^\epsilon$ can equivalently be expressed as an explicit functional of a correlated two-dimensional Brownian motion, so can be studied without any reference to SLE or LQG. 
We prove non-trivial upper and lower bounds for the cardinality of a graph-distance ball of radius $n$ in $\mathcal G^\epsilon$ which are consistent with the prediction of Watabiki (1993) for the Hausdorff dimension of LQG. Using subadditivity arguments, we also prove that there is an exponent $\chi > 0$ for which the expected graph distance between generic points in the subgraph of $\mathcal G^\epsilon$ corresponding to the segment $\eta([0,1])$ is of order $\epsilon^{-\chi + o_\epsilon(1)}$, and this distance is extremely unlikely to be larger than $\epsilon^{-\chi + o_\epsilon(1)}$.

A distance exponent for Liouville quantum gravity

The peanosphere (or "mating of trees") construction of Duplantier, Miller, and Sheffield encodes certain types of $\gamma$-Liouville quantum gravity (LQG) surfaces ($\gamma \in (0,2)$) decorated with an independent SLE$_{\kappa}$ ($\kappa = 16/\gamma^2 > 4$) in terms of a correlated two-dimensional Brownian motion and provides a framework for showing that random planar maps decorated with statistical physics models converge to LQG decorated with an SLE. Previously, the correlation for the Brownian motion was only explicitly identified as $-\cos(4\pi/\kappa)$ for $\kappa \in (4,8]$ and unknown for $\kappa > 8$. The main result of this work is that this formula holds for all $\kappa > 4$. This supplies the missing ingredient for proving convergence results of the aforementioned type for $\kappa > 8$. Our proof is based on the calculation of a certain tail exponent for SLE$_{\kappa}$ on a quantum wedge and then matching it with an exponent which is well-known for Brownian motion.

Brownian motion correlation in the peanosphere for $\kappa > 8$

We study Liouville quantum gravity (LQG) surfaces whose law has been reweighted according to nesting statistics for a conformal loop ensemble (CLE) relative to $n\in \{0,1,2,\dots\}$ marked points $z_1,\dots,z_n$. The idea is to consider a reweighting by $\prod_{B\subseteq [n]} e^{\sigma_B N_B}$, where $\sigma_B$ are real constants and $N_B$ is the number of CLE loops surrounding the points $z_i$ for $i\in B$. This is made precise via an approximation procedure where as part of the proof we derive strong spatial independence results for CLE. The reweighting induces logarithmic singularities for the Liouville field at $z_1,\dots,z_n$ with a magnitude depending explicitly on $\sigma_1,\dots,\sigma_n$. We define the partition function of the surface and explain its relationship to Liouville conformal field theory (CFT) correlation functions and a potential relationship with a CFT for CLE. In the case of $n\in\{0,1\}$ points we derive an explicit formula for the partition function. Furthermore, we obtain a recursive formula for the partition functions where we express the $n$ point partition function in terms of the partition function for disks with $k<n$ marked points, and we use this to partially determine for which values of $(\sigma_B\colon B\subseteq [n])$ the partition function is finite. The recursive formula is derived via a continuum counterpart of the peeling process on planar maps, which was earlier studied in works of Miller, Sheffield, and Werner in the setting of $n=0$ marked points. We also find an explicit formula for the generator of the Markov process describing the LQG boundary lengths in the continuum peeling process. Via an explicit calculation for this Markov process for $n=0$ we give a new proof for the law of the conformal radius of the outermost CLE loop in the unit disk around 0, which was earlier established by Schramm, Sheffield, and Wilson.

Liouville quantum gravity weighted by conformal loop ensemble nesting statistics

We prove a formula relating the Hausdorff dimension of a deterministic Borel subset of $${\mathbb {R}}$$ and the Hausdorff dimension of its image under a conformal map from the upper half-plane to a complementary connected component of an $$\hbox {SLE}_\kappa $$ curve for $$\kappa \not =4$$. Our proof is based on the relationship between SLE and Liouville quantum gravity together with the one-dimensional KPZ formula of Rhodes and Vargas (ESAIM Probab Stat 15:358–371, 2011) and the KPZ formula of Gwynne et al. (Ann Probab, 2015). As an intermediate step we prove a KPZ formula which relates the Euclidean dimension of a subset of an $$\hbox {SLE}_\kappa $$ curve for $$\kappa \in (0,4)\cup (4,8)$$ and the dimension of the same set with respect to the $$\gamma $$-quantum natural parameterization of the curve induced by an independent Gaussian free field, $$\gamma = \sqrt{\kappa }\wedge (4/\sqrt{\kappa })$$.

/pdf/dimension-transformation-formula-for-conformal-maps-into-the-hang7bfkf2.pdf

Nina Holden

Papers

Scaling limits of the Schelling model

A distance exponent for Liouville quantum gravity

Brownian motion correlation in the peanosphere for $\kappa > 8$

Liouville quantum gravity weighted by conformal loop ensemble nesting statistics

Dimension transformation formula for conformal maps into the complement of an SLE curve