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Mingchang Liu

Publications and source records attributed to Mingchang Liu.

14 recordsLinked to original sources

Gaussian free field in annulus: BPZ equations and crossing probabilities for level lines

We consider level lines of Gaussian free field (GFF) in annulus with alternating boundary conditions. We calculate the probability that all level lines cross the annulus. Such probability is given by the ratio between two partition functions. These two partition functions are constructed via Dub\'edat's regularized Dirichlet energy. We show that these partition functions are solutions to annulus Belavin-Polyakov-Zamolodchikov (BPZ) equations. In the annulus setup, the number of variables exceeds the number of BPZ equations, so the BPZ system alone does not determine the partition functions uniquely. By establishing sufficiently good control of the two partition functions constructed above, we are nevertheless able to derive the crossing probability.

math.PR

Dyson Brownian motion on a Jordan curve

Zabrodin recently proposed a generalization of Dyson Brownian motion to a setting where the particles are confined to a smooth Jordan curve in the plane. In this paper, we discuss a rigorous construction of such a process on a rectifiable Jordan curve and study some of its basic properties. Under further smoothness assumptions, we derive the associated Fokker-Planck-Kolmogorov equation, prove convergence towards the stationary Coulomb gas distribution, study large deviations at low temperature, and derive the limiting mean-field McKean--Vlasov equation in the many-particle limit.

math.PR

Uniform spanning trees and random matrix statistics

We consider a uniform spanning tree in a $\delta$-square grid approximation of a planar domain $\Omega$. For given integer $n\ge 2$, we condition the tree on the following $n$-arm event: we pick $n$ branches, emanating from $n$ points microscopically close to a given interior point, and condition them to connect to the boundary $\partial \Omega$ without intersecting. What can be said about the geometry of these branches? We derive an exact formula for the characteristic function of the total winding of the branches. A surprising consequence of this formula is that in the scaling limit, the behaviour of this function depends on the total number of branches $n$ only through its parity. We also describe the scaling limit of the branches. If $\Omega $ is the unit disc, then they hit the boundary (i.e., the unit circle) at random positions which coincide exactly with the eigenvalues of a random matrix of size $n$ drawn from the Circular Orthogonal Ensemble (COE, also called C$\beta$E with $\beta =1$). Furthermore, the branches converge to Loewner evolution driven by the circular Dyson Brownian motion with parameter $\beta = 4$ (i.e., $n$-sided radial SLE$_\kappa$ with $\kappa=2$). We thus verify a prediction made by Cardy in this setting. Along the way, we develop a flow-line (imaginary geometry) coupling of $n$-sided radial SLE$_\kappa$ with the Gaussian free field, which may be of independent interest. Surprisingly, we find that the variance of the corresponding field near the singularity also does not depend on the number $n\ge 2$ of curves. In contrast, the variance of the the winding of the curves behaves as $\kappa/n^2$, which agrees with the predictions from the physics literature made by Wieland and Wilson numerically, and by Duplantier and Binder using Coulomb gas methods -- but disagrees with a result of Kenyon.

math.PR

Tripod in uniform spanning tree and three-sided radial SLE$_2$

Fix a bounded $3$-polygon $(\Omega; x_1, x_2, x_3)$ with three marked boundary points $x_1, x_2, x_3\in\partial\Omega$ and suppose $(\Omega^{\delta}; x_1^{\delta}, x_2^{\delta}, x_3^{\delta})$ is an approximation of $(\Omega; x_1, x_2, x_3)$ on $\delta$-scaled hexagonal lattice. We consider uniform spanning tree (UST) in $\Omega^{\delta}$ with wired boundary conditions. Conditional on the event that both branches from $x_1^{\delta}$ and $x_2^{\delta}$ hit the boundary through $x_3^{\delta}$, the two branches meet at a point $\trifurcation^{\delta}$ which we call trifurcation, and the union of the three branches from $x_j^{\delta}$ to $\trifurcation^{\delta}$ form a tripod in the UST. We compute the scaling limit of the tripod: the distribution of trifurcation is absolutely continuous with respect to Lebesgue measure with explicit density; given the trifurcation, the conditional law of the tripod is three-sided radial SLE$_2$. The proof relies on construction of a new observable for trifurcation in our key lemma--Lemma~3.1--where we use Fomin's formula and the geometry of the hexagonal lattice in an essential way. Interestingly, the scaling limit of the observable for trifurcation coincides with the partition function for three-sided radial $\SLE_2$. Our result gives a probabilistic interpretation of the correlation function in CFT which has conformal weights $1$ at the three boundary points and has a spinless field of weights $(1,1)$ at the bulk point.

math.PR

Critical Ising model, Multiple SLE$_\kappa\left(\frac{\kappa-6}{2},\frac{\kappa-6}{2}\right)$ and $\beta$-Jacobi Ensemble

Fix $N\ge 1$ and suppose that $(\Omega;x_1,\ldots, x_{N}; x_{N+1}, x_{N+2})$ is a polygon, i.e. $\Omega$ is a simply connected domain with locally connected boundary and $x_1,\ldots,x_{N+2}$ are $N+2$ different points located counterclockwisely on $\partial\Omega$. Fix $\kappa\in (0,4)$. In this paper, we will give two different constructions of multiple $N$-SLE$_\kappa\left(\frac{\kappa-6}{2},\frac{\kappa-6}{2}\right)$ on $(\Omega;x_1,\ldots,x_{N}; x_{N+1},x_{N+2})$ and prove that they give the same law on random curves. Then, by establishing the uniqueness of multiple $N$-SLE$_\kappa\left(\frac{\kappa-6}{2},\frac{\kappa-6}{2}\right)$, we can obtain the joint law of the hitting points of multiple $N$-SLE$_\kappa\left(\frac{\kappa-6}{2},\frac{\kappa-6}{2}\right)$ with odd (resp. even) indices on $(x_{N+1}x_{N+2})$. After shrinking $x_1,\ldots,x_N$ to one point, the law of hitting points with odd (resp. even) indices converge to $\beta$-Jacobi ensemble with the conjectured relation $\beta=\frac{8}{\kappa}$. We will establish a direct connection between SLE-type curves and $\beta$-Jacobi ensemble. As an application, we consider critical Ising model on a discrete polygon $(\Omega^\delta_\delta;x^\delta_1,\ldots,x^\delta_{N}; x^\delta_{N+1},x^\delta_{N+2})$ with alternating boundary $(x^\delta_{N+2}x^\delta_{N+1})$ and free boundary $(x^\delta_{N+1}x^\delta_{N+2})$. Motivated by the partition function of multiple $N$-SLE$_\kappa\left(\frac{\kappa-6}{2},\frac{\kappa-6}{2}\right)$, we derive the scaling limit of the probability of the event that the interface $\gamma_j^\delta$ starting from $x^\delta_j$ ends at $(x^\delta_{N+1}x^\delta_{N+2})$ for all $1\le j\le N$. Moreover, we prove that given this event, the interface $(\gamma_1^\delta,\ldots,\gamma_N^\delta)$ converges to multiple $N$-SLE$_\kappa\left(\frac{\kappa-6}{2},\frac{\kappa-6}{2}\right)$ with $\kappa=3$.

math.PR

Multiple SLEs for $\kappa\in (0,8)$: Coulomb gas integrals and pure partition functions

In this article, we give an explicit relationship of SLE partition functions with Coulomb gas formalism of conformal field theory. We first construct a family of SLE$(\kappa)$ partition functions as Coulomb gas integrals and derive their various properties. In accordance with an interpretation as probabilistic correlations in loop $O(n)$ models, they are always positive when $\kappa \in (8/3,8)$, while they may have zeroes for $\kappa \le 8/3$. They also admit a Frobenius series expansion that matches with the algebraic content from CFT. Moreover, we check that at the first level of fusion, they have logarithmic asymptotic behavior when $\kappa = 8/3$ and $\kappa = 8$, in accordance with logarithmic minimal models $M(2,1)$ and $M(2,3)$, respectively. Second, we construct $\SLE_\kappa$ pure partition functions and show that they are real-analytic in $\kappa \in (0,8)$ and decay to zero as a polynomial of $(8-\kappa)$ as $\kappa \to 8$. We explicitly relate the Coulomb gas integrals and pure partition functions together in terms of the meander matrix. As a by-product, our results yield a construction of global non-simple multiple chordal SLE$(\kappa)$ measures ($\kappa \in (4,8)$) uniquely determined by their re-sampling property.

math-ph

Decomposition of Hypergeometric SLE and Reversibility

In this paper, we consider hypergeometric SLE process for $κ\in (4,8)$ and $ν>\fracκ{2}-6$. Though the definition of hypergeometric SLE process is complicated, we show that given its hitting point on a specific boundary, its conditional law can be described by SLE$_κ(\underlineρ)$ process. Based on this observation, by constructing a pair of curves, we derive the reversibility of hypergeometric SLE for $κ\in(4,8)$ and $ν>-2$.

math.PR

Hypergeometric SLE with $κ=8$: Convergence of UST and LERW in Topological Rectangles

We consider uniform spanning tree (UST) in topological rectangles with alternating boundary conditions. The Peano curves associated to the UST converge weakly to hypergeometric SLE$_8$, denoted by hSLE$_8$. From the convergence result, we obtain the continuity and reversibility of hSLE$_8$ as well as an interesting connection between SLE$_8$ and hSLE$_8$. The loop-erased random walk (LERW) branch in the UST converges weakly to SLE$_2(-1, -1; -1, -1)$. We also obtain the limiting joint distribution of the two end points of the LERW branch.

math.PR

Decomposition of global 2-SLE for $\kappa\in (4,8)$ and an application for critical FK-Ising model

We consider global 2-SLE$_{\kappa}$ $(\eta_1, \eta_2)$ in a topological rectangle with $\kappa\in (4,8)$. We derive the law of a random hitting point of the curves and show that, conditional on this random hitting point, the pair of two curves has the same law as Gaussian free field flow lines with proper boundary data. Using a similar idea, we derive the asymptotic of the probability for $\eta_1\cap\eta_2=\emptyset$. As an application, we derive the asymptotic of the probability for the existence of two disjoint open paths in critical FK-Ising model.

math.PR

Piecewise Temperleyan dimers and a multiple SLE$_8$

We consider the dimer model on piecewise Temperleyan, simply connected domains, on families of graphs which include the square lattice as well as superposition graphs. We focus on the spanning tree $\mathcal{T}_δ$ associated to this model via Temperley's bijection, which turns out to be a Uniform Spanning Tree with singular alternating boundary conditions. Generalising the work of the second author with Peltola and Wu \cite{LiuPeltolaWuUST} we obtain a scaling limit result for $\mathcal{T}_δ$. For instance, in the simplest nontrivial case, the limit of $\mathcal{T}_δ$ is described by a pair of trees whose Peano curves are shown to converge jointly to a multiple SLE$_8$ pair. The interface between the trees is shown to be given by an SLE$_2(-1, \ldots, -1)$ curve. More generally we provide an equivalent description of the scaling limit in terms of imaginary geometry. This allows us to make use of the results developed by the first author and Laslier and Ray \cite{BLRdimers}. We deduce that, universally across these classes of graphs, the corresponding height function converges to a multiple of the Gaussian free field with boundary conditions that jump at each non-Temperleyan corner. After centering, this generalises a result of Russkikh \cite{RusskikhDimers} who proved it in the case of the square lattice. Along the way, we obtain results of independent interest on chordal hypergeometric SLE$_8$; for instance we show its law is equal to that of an SLE$_8 (\bar ρ)$ for a certain vector of force points, conditional on its hitting distribution on a specified boundary arc.

math.PR

Loop-Erased Random Walk Branch of Uniform Spanning Tree in Topological Polygons

We consider uniform spanning tree (UST) in topological polygons with $2N$ marked points on the boundary with alternating boundary conditions. In [LPW21], the authors derive the scaling limit of the Peano curve in the UST. They are variants of SLE$_8$. In this article, we derive the scaling limit of the loop-erased random walk branch (LERW) in the UST. They are variants of SLE$_2$. The conclusion is a generalization of [HLW20,Theorem 1.6] where the authors derive the scaling limit of the LERW branch of UST when $N=2$. When $N=2$, the limiting law is SLE$_2(-1,-1; -1, -1)$. However, the limiting law is nolonger in the family of SLE$_2(ρ)$ process as long as $N\ge 3$.

math.PR

Uniform Spanning Tree in Topological Polygons, Partition Functions for SLE(8), and Correlations in $c=-2$ Logarithmic CFT

We find explicit SLE(8) partition functions for the scaling limits of Peano curves in the uniform spanning tree (UST) in topological polygons with general boundary conditions. They are given in terms of Coulomb gas integral formulas, which can also be expressed in terms of determinants involving a-periods of a hyperelliptic Riemann surface. We also identify the crossing probabilities for the UST Peano curves as ratios of these partition functions. The partition functions are interpreted as correlation functions in a logarithmic conformal field theory (log-CFT) of central charge $c= -2$. Indeed, it is clear from our results that this theory is not a minimal model and exhibits logarithmic phenomena -- the limit functions have logarithmic asymptotic behavior, that we calculate explicitly. General fusion rules for them could also be inferred from the explicit formulas. The discovered algebraic structure matches the known Virasoro staggered module classification, so in this sense, we give a direct probabilistic construction for correlation functions in a log-CFT of central charge $-2$ describing the UST model.

math.PR

Scaling Limits of Crossing Probabilities in Metric Graph GFF

We consider metric graph Gaussian free field (GFF) defined on polygons of $δ\mathbb{Z}^2$ with alternating boundary data. The crossing probabilities for level-set percolation of metric graph GFF have scaling limits. When the boundary data is well-chosen, the scaling limits of crossing probabilities can be explicitly constructed as "fusion" of multiple SLE$_4$ pure partition functions.

math.PR

Reaching 7Li BEC with a Mini-Trap

A novel mm-scale Ioffe-Pritchard trap is used to achieve Bose-Einstein condensation in 7Li. The trap employs free-standing copper coils integrated onto a direct-bond copper surface electrode structure. The trap achieves a radial magnetic gradient of 420 G/cm, an axial oscillation frequency of 50 Hz and a trap depth of 66 G with a 100 A drive current and 7 W total power dissipation.

quant-ph