CONVERGENCE OF EIGENVALUES TO THE SUPPORT OF THE LIMITING MEASURE IN CRITICAL β MATRIX MODELS C. FAN ‡ , A. GUIONNET † , Y. SONG § , AND A. WANG] We consider the convergence of the eigenvalues to the support of the equilibrium measure in the β ensemble model under a critical condition. We show a phase transition phenomenon, namely that all eigenvalues will fall in the support of the limiting spectral measure when β > 1, whereas this always fails when β < 1. Abstract. 1. 1.1. introduction and statement of the result Denitions and Known Results. B Let be a subset of the real line. B can be chosen as the whole real line, an interval, or the union of nitely many disjoint V :B →R β > 0 be a β ensemble, i.e a sequence of ;B N N random variables (λ1 , . . . , λN ) with law µVN,β on R . The β matrix model with potential V on the set B is dened as the probability N measure on R given by intervals. For now, let be an arbitrary function, and let positive real number. In this paper, we consider the ;B dµVN,β (λ) = where V ;B ZN,β V ;B ZN,β i=1 ˆ ··· = R β ˆ Y N Ω Nβ 2 V (λi ) 1B (λi ) Y β |λi − λj | , (1.1) 1≤i<j≤N dλi e− Nβ 2 V (λi ) ;R µVN,β Y 1B (λi ) R i=1 is equal to 1, 2, or 4, values of dλi e− is the partition function V ;B ZN,β If N Y 1 β |λi − λj | . (1.2) 1≤i<j≤N is the probability measure induced on the eigen- by the probability measure dΩe− Nβ 2 Tr(V symmetric, Hermitian, and self-dual quaternionic (Ω)) on a vector space of real N ×N matrices respectively, see[Meh04]. Therefore, the β ensemble can be viewed as the natural generalization of these matrix models and we will refer to λi as eigenvalues of a "matrix model". For a ‡ Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139-4307 USA. email: cjfan@math.mit.edu. † Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139-4307 USA. email: guionnet@math.mit.edu. § Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139-4307 USA. email: yuqisong@.mit.edu. ] Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139-4307 USA. email: wandi@.mit.edu. 1 Convergence of eigenvalues to the support of the limiting measure quadratic potential, the β 2 ensemble can also be realized as the eigenvalues of tridi- agonal matrices [DE02]. Eventhough such a construction is not known for general potentials, β matrix models are natural Coulomb interaction probability measures which appear in many dierent settings. These laws have been intensively studied, both in physics and in mathematics. pirical measure of the λi 's In particular, the convergence of the em- was proved [ST97, Dei99, AGZ10], and its uctuations analyzed [Joh98, Pas06, Shc13]. Moreover, the partition functions as well as the mean Stieltjes transforms can be expanded as a function of the dimension to all orders [BIPZ78, ACKM93, ACM92, Ake96, CE06, Che06, BG11, BG13]. It turns out that both central limit theorems and all order expansions depend heavily on whether the limiting spectral measure has a connected support. Indeed, when the limiting spectral measure has a disconnected support, it turns out that even though most eigenvalues will stick into one of its connected components, some eigenvalues will randomly switch from one to the other connected components of the support even at the large dimension limit. This phenomenon can invalidate the central limit theorem in [Pas06, Shc13] and result with the presence of a Theta function in the large dimension expansion of the partition function. In the case where the limiting measure has a connected support asymptotically to S, S , and that the eigenvalues are assumed to belong even more rened information could be derived. this case, local uctuations of the λi 's Indeed, in could rst be established in the case corre- β = 1, 2 or 4 and V (x) = x2 [Meh04], then 2 to tridiagonal ensembles (all β ≥ 0 but V (x) = x ) [RRV06] and more recently for general potentials and β ≥ 0 [BEY12, BEY, Shc13, FB]. However, local ucsponding to Gaussian random matrices, tuations have not yet been studied in the case where the limiting measure has a disconnected support nor when it is critical. We shall below dene more precisely the later case but let us say already that a non-critical potential prevents the eigenvalues to deviate from the support of the limiting spectral measure as the dimension goes to innity. In fact, the later property is one of the most fundamental question when one wants to study the local uctuations of the eigenvalues. We study in this article β models with critical potentials and whether the eigenvalues stay conned in the limiting support. In fact, we exhibit an interesting phase transition; we show that if β>1 the eigenvalues stay conned whereas if β<1 some deviate towards the critical point with probability one. We postpone the study of the critical case β=1 to further research. Let us nally point out that the case where the poten- tial is critical, but with critical parameters tuned with the dimension so that new phenomena occur, was studied in [Cla, Eyn06]. We restrict ourselves to potentials independent of the dimension. We next describe more precisely some of the results stated above, the denition of criticality and our results. Consider the centered on line. spectral measure LN := λi . LN belongs to the set 1 N PN i=1 δλi , where δλi is the Dirac measure of probability measures on the real M1 (B) We endow this space with the weak topology. Then, LN converges almost surely. This convergence can be derived from the following large deviation result (see [BAG97], and [AGZ10, Theorem 2.6.1]) : Theorem 1.1. Assume that V is continuous and goes to innity faster than 2 log |x| ;B (if B is not bounded). The law of LN under µVN,β satises a large deviation prin2 ciple with speed N and good rate function E , where Ẽ = E − inf{E(µ), µ ∈ M1 (B)} Convergence of eigenvalues to the support of the limiting measure with β E[µ] = 2 ¨ (V (ξ) + V (η) − log |ξ − η|) dµ(ξ)dµ(η) . In other words, (1) (2) (3) Ẽ : M1 (R) → [0, ∞] possesses compact level sets {v : Ẽ(v) ≤ M } M ∈ R+ . for any open set O ⊂ M1 (B), 1 ;B (LN ∈ O) ≥ − inf Ẽ. lim inf 2 log µVN,β O N →∞ N for any closed set F ⊂ M1 (B), 1 ;B (LN ∈ F ) ≤ − inf Ẽ. lim inf 2 log µVN,β F N →∞ N The minimizers of E 3 are described as follows (see [AGZ10, (1.3) for all Lemma 2.6.2]): Theorem 1.2. E achieves its minimal value at a unique minimizer µeq . Moreover, µeq has a compact support S. In addition, there exists a constant Cβ,V such that: ( for x ∈ S for x almost everywhere in Sc ´ 2 R dµeq (ξ) ln |x − ξ| − V (x) = Cβ,V ´ 2 R dµeq (ξ) ln |x − ξ| − V (x) < Cβ,V . (1.4) Here the almost everywhere means almost everywhere with respect to Lebesgue measure. We will refer to µeq , which is compactly supported, as the equilibrium measure. ;B Remark 1.3. Theorem 1.1 and Theorem 1.2 imply that under µVN,β , LN converges to (in weak topology) to the equilibrium measure µeq almost surely. Once the existence of the equilibrium measure is established, one may explore the convergence of the eigenvalues to the support of the equilibrium measure µeq . It is shown in [BG11, BG13](also see Theorem 1.4 below) that the probability that eigenvalues escape this limiting support is governed by a large deviation principle with rate function given by J˜V ;B (x) = J V ;B (x) − Cβ,V with J V ;B ( ´ β V (x) − β dµeq (ξ) ln |x − ξ| x ∈ B\S 2 (x) = Cβ,V otherwise. (1.5) (1.6) The large deviation states as follows: Theorem 1.4. Assume V continuous and going to innity faster than 2 log |x| (in the case where B is innite). V ;B (1) J˜max is a good rate function . (2) We have large deviation estimates: for any F ⊆ B\S closed and O ⊆ B\S open, 1 β ;B ln µVN,β [∃i λi ∈ F] ≤ − inf J˜V ;B (x), N 2 x∈F 1 β ;B lim inf ln µVN,β [∃i λi ∈ O] ≥ − inf J˜V ;B (x). N →∞ N 2 x∈O lim sup N →∞ Convergence of eigenvalues to the support of the limiting measure 4 The last theorem shows that the support of the spectrum is governed by the minimizers of J˜V ;B . Denition 1.5. Assume V is continuous. We say that V is non-critical i J V ;B is positive everywhere outside of the support of µeq . A consequence of the second part of the aforementioned theorem is the following: Corollary 1.6. Let the assumptions in Theorem 1.4 hold. Assume that V is noncritical. Then ;B lim µVN,β (∃λi ∈ / A) = 0 , (1.7) N →∞ + c where A := ∪gh=1 [a− h , ah ] with min{|x − y|, x ∈ A , y ∈ S} > 0. Remark 1.7. Since the law of the eigenvalues satises a large deviation principle with rate N, the eigenvalues actually converges to the support exponentially fast (or ;B be more precisely, ∃Γ > 0, s.t, µVN,β (∃λi ∈ / A) ≤ e−ΓN ). Remark 1.8. By the denition of the partition function, Z , thus, Z ;B 1 − µVN,β (∃λi ∈ / A) = V ;A N,β V ;[b−.b+] N,β (1.7) ⇔ lim N →∞ V ;A ZN,β V ;B ZN,β = 1. (1.8) In the rest of this article we investigate what happens in the case where critical. This investigation will require the uses of precise estimates on β V is models partitions functions derived in [BG11, BG13] and to apply their results we shall make the following assumption : Assumption 1. • If • V :B→R is a continuous function independent of lim inf x→τ ∞ V (x) > 1. 2 ln |x| (1.9) • suppS (µeq ) is a nite union of disjoint intervals, i.e. supp (µeq ) g S = h=1 Sh , where Sh = [αh− , αh+ ]. • S(x) > 0 whenever x ∈ S, where s Q dµeq τ 0 ∈Hard (x − ατ 0 ) S(x) = π Q . dx τ ∈Soft (x − ατ ) and where • N. τ ∞ ∈ B, τ ∈ Hard (resp. τ ∈ Soft) i bτ = ατ (resp. of the form τ (bτ − ατ ) > 0). S. V extends to a holomorphic function in some open neighborhood of We want to investigate whether (1.7) still holds when the restriction on weakened so that it vanishes outside the support S. J V ;B is Our working hypothesis will be the following: Assumption 2. J˜V ;B vanishes only on the support of the equilibrium measure S c0 outside S . We also require ∂ 2 J˜V ;B (c0 ) > 0, and for technical 2 require ∂ V ≥ σ > 0 on A. and at one point reason we Convergence of eigenvalues to the support of the limiting measure 5 Main Results. Theorem 1.9. Given Assumptions 1 and 2, we have the following alternative: • when β > 1, 1.2. ;B lim µVN,β (∃λi ∈ / A) = 0, • (1.10) N →∞ when β < 1, ;B lim sup µVN,β (∃λi ∈ / A) = 1. (1.11) N →∞ The behavior below β = 1 can be illustrated with the case β = 0 where one V vanishing on a support S and at a point c0 (where its would consider a potential second derivative is positive), being strictly positive everywhere else. This corresponds to N independent variables with probability of order small neighborhood of c0 N −1/2 to belong to a (where the latter probability can be estimated by Laplace method). In this case, it is clear that some eigenvalues will lie in the neighborhood of c0 with positive probability. nomenon at β=1 The existence of a phase transition for this phe- is however new to our knowledge. It suggests that the support of the eigenvalues of matrices with real coecients corresponding to β=1 matrix models might be more sensible to perturbations of the potential than matrices with complex coecients (corresponding to β = 2). This is however apparently not supported by nite dimensional perturbations since the BBP transition [BBAP05] does not vary much between these two cases. Let us observe that our arguments c0 without changing J at these critical points |x − c0 |q for some q > 2 in the vicinity of a threshold βq depending on q (see remark could be carried similarly with several critical points similar to the phase transition. However, if the second derivative of could vanish so that c0 , J V ;B behaves as the phase transition would occur at 5.17). 1.3. Structure of the paper. In Section 2 we reduce the problem to the analysis of (2.2). (2.2) relies heavily on the estimate for the probability that M eigenvalues are contained in a small neighborhood of eigenvalues are contained in A. c0 while the rest of the N-M of the The entirety of section 5 is devoted to the proof of proposition 2.1, which gives the desired estimate for the case β >1 and Section 4 with the case β < 1. ;B ΦVN,M,β . Section 3 deals with The Appendix contains some useful results for our problem. Notation. We use the notation A . B (resp. A & B ) to denote A ≤ CB + 2 A ≥ CB − e−δN ) for some universal constant C and some δ > 0 independent of N . A ≈ B when both A . B and A & B hold. Moreover, we use A .Q B to denote A ≤ CQ B , i.e, the constant C may depend on Q. c usually denotes a small constant while C denotes a large constant. The values of these constants may change line by line. We sometimes use a 1 to denote that a is 1.4. e−δN 2 (resp. smaller than any universal constant involved in the proof. 2. Preliminary and Basic analysis M eigenvalues are contained in a small N − M of the eigenvalues are contained in A The probability that a specic subset of neighborhood of c0 shall be denoted as while the other ;B ΦVN,M,β : ;B ;B ΦVN,M,β := µVN,β (λN −M +1 , ..., λN ∈ [c0 − , c0 + ], λ1 , ...λN −M ∈ A) . (2.1) Convergence of eigenvalues to the support of the limiting measure where 6 > 0 is a small xed constant. The key to prove our main result is calculating ;B ΦVN,M,β approaches 0 as N approaches +∞. the speed at which Note that ;B ;B µVN,β (∃λi ∈ / A) = µVN,β (∃λi ∈ / (A ∪ [c0 − , c0 + ])) X V ;B µN,β (M eigenvalues are in [c0 − , c0 + ], N − M + M N X + eigenvalues are in 1≤M ≤δN N M ;B ΦVN,M,β =: P1 + P2 + P3 . Here δ>0 J Since (2.2) is a small xed constant. is a good rate function which is positive outside Theorem 1.4 implies that for any xed In other words, it is controlled by > 0 , P1 e−N c for some A ∪ [c0 − , c0 + ] P2 is controlled by e c(δ) > 0 such that in Theorem 1.1, there exists −c N 2 c > 0. LN described . Therefore we deduce that for any ;B µVN,β (∃λi ∈ / A) = P3 + O(e−c(δ)N ). Our goal, therefore, is to control the third term J , approaches 0 exponentially fast. By the large deviation principle for the law of the empirical measure Since A) >δ δ>0 (2.3) P3 . goes to innity at innity, Theorem 1.4 also shows that the probability to have an eigenvalue above some nite threehold M goes to zero exponentially fast. Therefore, we may assume without loss of generality that Thus, we are left to analyze B is a bounded set. ;B ΦVN,M,β . We prove the following upper bound in section 5: Proposition 2.1. Let Assumption 1 and 2 hold. Then, there exists a δ > 0 such that when M N ≤ δ , we have uniformly in M ≤ δN ;B ΦVN,M,β . On the other hand, N V ;A ZN,β 1 N 1 (β+1) 2 V ;B ZN,β M (β+1) 2 . (2.4) ;B . ΦVN,1,β . (2.5) The calculation is based on the precise estimate derived in [BG13] for the partition function and correlators for xed lling fraction measure, that is with given number of eigenvalues in each connected part of the support S. The proof of this proposition will be the subject of section 5. We next give the proof of our main result. 3. Convergence of the eigenvalues to the limiting support S when β>1 Now, we return to the estimate in (2.3) and use the upper bound provided by Proposition 2.1 to nd P3 ≤ X 1≤M <δN N M N (β+1) ;B ΦVN,M,β . 1 + N− 2 − 1. (3.1) Convergence of eigenvalues to the support of the limiting measure 2 ;B e−cN in ΦVN,M,β , 1 ≤ M ≤ δN is β > 1, P3 goes to 0 as N approaches where we nally noted that any error of order neglectable in the above sum . Hence, when +∞. 7 This nishes the proof of the rst half of our main Theorem 1.9. 4. Escaping eigenvalues when We prove that when borhood of c0 β<1 β<1 the probability that no eigenvalues lies in the neigh- goes o zero, that is by Remark 1.8, that we have: lim N →∞ V ;A ZN,β V,B ZN,β = 0. (4.1) pVN,β that one eigenvalue exactly lies in the neighborhood of c0 . Indeed, as Ai = {λi ∈ [c0 − , c0 + ], λj ∈ A, j 6= i} are disjoint as soon as [c0 − , c0 + ] ∩ A = ∅, we have This is done by lower bounding the probability ;B pVN,β = N ΦVN,1,β . Since pVN,β ≤ 1, we deduce from (2.5) that there exists a nite constant C N which results with N V ;A ZN,β (β+1) 2 V ;B ZN,β V ;A ZN,β V ;B ZN,β ≤ CN such that ≤C, β−1 2 , so that (2.5) follows. 5. Proof of the main Proposition 2.1 Our proof is based on estimates from [BG13] on the xed lling fraction measure which will allow us to estimate precisely the probability that A, N −M eigenvalues M c0 . Let us introduce some extra notations to describe these P estimates. Let Eg := {(1 , · · · , g )| h = 1, 1 , . . . , g > 0} denote the interior of the standard g − 1 simplex. Let stay in whereas Laplace methods will be used to control the probability that eigenvalues are close to ? := (µeq (S1 ), · · · , µeq (Sg )) be the (5.1) g -tuple denoting the value of the equilibrium measure on each of the intervals that comprise the support of the equilibrium measure. Denition 5.1. Let the xed lling fraction probability measure by: ;A dµVN,,β (λ) := 1 g hY Nh Y V ;A ZN,,β h=1 Y × dλh,i 1Ah (λh,i ) e− βN 2 i=1 Y V (λh,i ) ;A dµVN,,β Y be given |λh,i − λh,j |β i 1≤i<j≤N β |λh,i − λh0 ,j | , 1≤h<h0 ≤g 1≤i≤Nh 1≤j≤Nh0 V ;A ;A where ZN,,β is the partition function. The xed lling fraction measure dµVN,,β ;A can be viewed as the probability measure induced by dµVN,β conditioned on that the number of the eigenvalues in [ah −, ah +] is xed as Nh = [N h ], 1 ≤ h ≤ g − 1, Convergence of eigenvalues to the support of the limiting measure Pg−1 Ng = N − h=1 Nh . − → N = (N1 , . . . , Ng ). 8 ;A We alternatively denote by µVN,;A− = µVN,,β for Nh = [N h ], → N ,β The following precise estimate from [BG13, Theorem 1.4] will be essential in our proof (up to corrections of order K = 0): Theorem 5.2. If V satises Assumption 1 and 2 on A, there exists t > 0 such that, uniformly for ∈ Eg that satises | − ? | < t, we have: K X β N! {k} V ;A ZN,,β = N ( 2 )N +e exp N −k F,β + o(N −K ) , h=1 (Nh )! Qg (5.2) k=−2 Here Nh := [N h ]. e is a constant depending only whether each edge is soft or {k} hard. F,β is a smooth function for close enough to ? , and at the value = ? , {−2} the derivative of F,β vanishes and its Hessian is negative denite. Moreover, the ;A law of the empirical measure LN under µVN,,β satises a large deviation principle with speed N 2 and good rate function Ẽ which is minimized at a unique probability ;A measure µeq, . In particular LN converges µVN,,β almost surely to µeq, . One can also estimate precisely the correlators of the xed fraction measure: Denition 5.3. The correlators of the xed lling fraction measure are given for x ∈ C\A : X ;A W (x) := µVN,,β { 1 }, x − λi W{−1} (x) := µeq, ( 1 ). x−λ (5.3) A consequence of [BG13, Theorem 1.3] also gives us the following theorem regarding the correlators: Theorem 5.4. [BG13] If V satises Hypotheses 1 and 2 on A, there exists t > 0 such that, uniformly for ∈ Eg and | − ? | < t, we have an expansion for the correlators: W (x) = N W{−1} (x) + O(1). (5.4) holds uniformly for x in compact regions outside A(in our case in particular near the critical point c0 ). W{−1} is smooth for close enough to ? (5.4) Remark 5.5. Alternatively, we can view [c0 − δ, c0 + δ] as a degenerate, additional cut of the support of µeq . However, even if we can achieve an analogue of Theorem 5.2, taking this alternate viewpoint into account, which is likely to be a dicult task, we still cannot exclude the possibility that nite eigenvalues are concentrated near the critical point c0 . Thus, we do not apply this alternate strategy. Our goal is to split ΦV,B N,M,β into components and estimate the value of each component. Then, we combine the values of the components to estimate ΦV,B N,M,β . Convergence of eigenvalues to the support of the limiting measure We start with the explicit formula for V ;B ΦN,M,β ˆ 1 = V ;B ZN,β ΦV,B N,M,β : N Y dλj e− Nβ 2 V × λi ∈A β(N −M ) − 2 dλi e |λk − λl |β N −M +1≤k<l≤N NY −M Y (λj ) [c0 −,c0 +]M j=N −M +1 ˆ 9 ( N N −M N Y V (λi )) |λi − λj |β j=N −M +1 i=1 Y × |λi − λj |β . (5.5) 1≤i<j≤N −M We want to rewrite N ;B ΦVN,M,β in terms of V ;A N −M µN −M,β , the law of the N −M eigenvalues N V ;B N −M V ;A in A. Note that ΦN,M,β is equal to µN −M,β multiplied by the law of the M eigenvalues in [c0 − , c0 + ] conditioned on the values of the N − M eigenvalues in A. Also, note that the |λk −λl |β Q N −M +1≤k<l≤N (2) term is controlled by βM (M −1) 2 . Thus, let: (N −M )! N1 +···+Ng =N −M N1 !···Ng ! P N N −M YN,M := V ;A ZN −M,β V ;B ZN,β N Ξ(η1 , · · · , ηM ) V ;A = N −M := µN −M,β ( M Y N · Z N −M V,A −−−−→ −M N −M, N N −M ,β V ;B ZN,β eβ PN −M i=1 ln |ηj −λi |− β 2 (N −M )V (ηj ) ), (5.6) j=1 ˆ LN,M [c0 −,c0 +]M where N Y Ξ(λN −M +1 , · · · , λN ) := −−−−−→ N − M := (N1 , · · · , Ng ) e− Mβ 2 V (λj ) dλj j=N −M +1 with P Ni = N − M . Then, we have: ;B ΦVN,M,β ≤ (2) βM (M −1) 2 YN,M LN,M . (5.7) When M=1, the inequality (5.7) becomes an equality: ΦV,B N,1,β = YN,1 LN,1 (5.8) (5.8) will be applied when we prove (2.5). We wish to split YN,M into components ỸN,M = FN,M GN,M , (5.9) for further analysis. We make the decomposition; YN,M = V,A ZN,β V,B ZN,β where ỸN,M , N FN,M = V ;A −M ZNN−M,β V ;A ZN −M,β , GN,M = V ;A ZN −M,β V ;A ZN,β . (5.10) FN,M LN,M and GN,M , we end up with an estimate of ỸN,M , which V,A V,B bound on YN,M as ZN,β ≤ ZN,β . It will also provide a lower bound for By estimating is an upper Φ1,M to prove (2.5). Thus one rewrites formula (5.7) as: V ;B ΦN,M,β ≤ (2) βM (M −1) 2 GN,M FN,M LN,M . (5.11) Convergence of eigenvalues to the support of the limiting measure 10 Remark 5.6. We always consider M N < δ 1.The δ should be chosen to be smaller than the constant t in Theorem 5.2, and in practice we need to make it even smaller s.t we can use Taylor expansions near the ? (see Theorem 5.2 and (5.1)). We next estimate GN,M , FN,M and LN,M . step 1: Estimating GN,M . Proposition 5.7. There exists small δ > 0, s.t when M 5.1. GN,M ≈ CM 1 N Mβ 2 eN M (inf ξ∈B J V ;B (ξ)+ β 2 ´ ≤ δN , we have V (η)dµeq (η)) . (5.12) Furthermore, there exists a nite constant C such that for all 1 ≤ M ≤ δN , CM satisfy the control 2 CM ≤ CeCM . Proof. (5.13) Proposition 5.7 follows directly from the Lemma 5.9 and Corollary 5.12 below. Remark 5.8. The term eCM does not aect the nal estimate due to the presence in (5.11). Also, M is always much smaller than N , even though M of (2) is not xed for all N . 2 βM (M −1) 2 To prove Proposition 5.7 we rst show the following Lemma. Lemma 5.9. GN,M ≈ eM N Aβ where Aβ does not depend on N or M and The value of Proof. Aβ 1 M β CM , N 2 2 CM . eCM (5.14) will be given by Corollary 5.12. By the partition function estimate from Theorem 5.2, for a suciently small δ, N (N − M )! V,A , · Z N −M − −−−→ −M N1 ! · · · Ng ! N −M, N N −M ,β N1 +···+Ng =N −M X {1} )(N −M )+e 2 {2} (β 2 ≈ exp (N − M ) F − (N − M ) . −−−→ + (N − M )F −−−−→ N −M N −M X V,A ZN −M,β = N −M N1 +···+Ng =N −M, N −M −−−−→ −M |N N −M −? |<δ (5.15) In the last step we applied the large deviation principle for the empirical measure −−−−→ −−−−→ −M LN ; in other words, the sum over all N − M such that | N N −M −? | ≥ δ is negligible. Similarly, N (N − M )! V,A ·ZN → , − N, N N1 ! · · · Ng ! N ,β N1 +···+Ng =N X β {2} {1} ≈ (N )( 2 )(N )+e exp (N )2 F → + (N )F . − → − N N X V,A ZN,β = N1 +···+Ng =N, → − |N N −? |<δ N N (5.16) Convergence of eigenvalues to the support of the limiting measure 11 LN , we need only consider − → − → −−−−→ N N N −M , suciently close to ? . By Theorem 5.2, for N N −M N suciently close to ? , F {1} and F {2} are smooth, and because the Hessian of F {2} is negative denite, {2} {2} F − F? ≈ −| − ? |2 . We point out by large deviation of the empirical measure All that is left to do is to analyze the limiting behavior of : X LK := {2} {1} K K exp((K)2 F → + (K)F → − ). − K K N1 +···+Ng =K, (5.17) → − |K K −? |<δ Here K = (N1 , · · · , Ng ) with P Ni = K . The following lemma suces to complete the proof. Lemma 5.10. {2} → ≈ exp(K 2 F∗ + KF{1} ) L− ? K (5.18) Clearly, Lemma 5.10 plus (5.15), (5.16) imply (5.14). Now we give the proof of the lemma. Proof of lemma 5.10. According to Theorem 5.2, we can nd constant c, C s.t By the smoothness of −→ s.t 1 |K K − ? | . |F{1} − F{1} | ≤ C| − ? |, ? (5.19) F{2} − F{2} ≤ −c| − ? |2 , ? (5.20) |F{2} − F{2} | ≤ C| − ? |2 . ? (5.21) F {1} and F {2} and because there exists at least one −→ K1 , 1 K , we can easily get the lower bound(using (5.19), (5.21): {2} → & exp(K 2 F∗ + KF{1} ). L− ? K (5.22) − → Next, we calculate the upper bound. Actually, since we only sum over 1 |K K −? | we only need to establish by (5.19) and (5.20) that X → − |K K −? |1 exp(−cK 2 | − → − → K K − ? |2 + CK| − ? |) . 1. K K (5.23) Clearly, (5.23) plus (5.19) and (5.20) will give the upper bound: {2} → . exp(K 2 F∗ + KF{1} ). L− ? K (5.24) Convergence of eigenvalues to the support of the limiting measure 12 To prove (5.23), let Q be a large constant such that cQ>100C, then X exp(−cK 2 | → − − → − → K K − ? |2 + CK| − ? |) K K |K K −? |1 − → − → K K 2 − ? | + CK| − ? |), exp(−cK | K K X ≤ 2 → − Q |K K −? |≤ K X + − → − → K K 2 exp(−cK | − ? | + CK| − ? |), K K 2 → − Q |K K −? |> K X .Q 1 + → − Q |K K −? |> K (5.25) − → 1 2 K exp(− cK | − ? |2 ), 2 K . 1. which proves the Lemma. Having established Lemma 5.9, we complete the proof of Proposition 5.7 by computing Aβ . As Aβ does not depend on M it is enough to prove the following lemma: Lemma 5.11. Given η0 , η00 > 0 and N large enough, 0 β GN,1 ≥ eN (−η +inf ξ∈A J (ξ)+ 2 GN,1 ≤ eN (η 00 +inf ξ∈A J (ξ)+ β 2 ´ ´ V (η)dµeq (η)) V (η)dµeq (η)) , (5.26) . Proof of the lemma almost exactly follows the same computation in the appendix A of [BG11]; For completeness, we include the proof in our Appendix, see lemma A.3. Thus, we simply take M=1 in Lemma 5.9. By Lemma 5.9, for each η 0 , η 00 > 0, and for large N, ˆ β N (−η + inf J (ξ) + V (η)dµeq (η)) ≤ N Aβ + C ln(N + 1), ξ∈A 2 ˆ β N (η 00 + inf J (ξ) + V (η)dµeq (η)) ≥ N Aβ − C ln(N + 1). ξ∈A 2 0 since we can choose η 0 , η 00 > 0 arbitrarily and also note inf J = inf J . ξ∈A Thus we get the value of ξ∈B (5.28) Aβ : Corollary 5.12. Aβ = { inf J (ξ) + ξ∈B Thus we get the value of Proposition 5.7. (5.27) Aβ ,which β 2 ˆ V (η)dµeq (η)}. (5.29) completes with Lemma 5.9, the proof of Convergence of eigenvalues to the support of the limiting measure 5.2. step 2: Estimating the product FN,M × LN,M . from above uniformly on under µV,A N,β |M | ≤ δN , To bound FN,M 13 and LN,M we wish to use concentration inequalities V on each A is not connected, This is the point where we will use the strict convexity of connected components of A, see Assumption 2. However, when the density of this measure is not strictly log-concave and standard concentration of measure results do not apply. To remedy this point, we will expand the product FN,M × LN,M in terms of the xed ling fractions ;A µVN,,β which have a strictly log-concave density under Assumption 2. Indeed we then have, see [[2.3.2], [4.4.17], [4.4.26] ] in [AGZ10] for more details, Lemma 5.13 (Concentration Inequality). Let be given. Let V be a smooth function such that V 00 (x) ≥ C > 0 for all x ∈ A. Let f be a function that is class C 1 on RN . Then h i V ;A ;A µVN,,β e(f −µN,,β (f )) . e N C kf kL , where 1 2 (5.30) v uN uX kf kL := t k∂λi f k2∞ . i=1 Remark 5.14. In practice, we only need the information of f on A, in other words we only require f to be smooth near A and kf kL in the above lemma can be replaced by kf kL(A) . To use this lemma, we write the decomposition over the feeling fractions. By the large deviation principle for the empirical measure Theorem 1.1 it is possible to restrict ourselves to the case where the feeling fractions are closed to that of the equilibrium, up to an error of order (λN −M +1 , . . . , λN ). e−N 2 . Moreover, we rst work with xed We shall prove the following upper bound Proposition 5.15. There exists > 0 so that for any λN −M +1 , · · · , λN belong to we have the following uniform estimate: [c0 − , c0 + ], 2 FN,M ΞN,M (λN −M +1 , · · · , λN ) . CeCM e ´ − βN2M V (η)dµeq (η) −N e PN j=N −M +1 J V ;B (λj ) (5.31) Proof. From the above considerations, we can write up to this small error X FN,M Ξ(λN −M +1 , · · · , λN ) ≈ −−−→ d−−−−→ , c− N −M N −M (5.32) N −M =N1 +···+Ng , −−−−→ −M |N N −M −? |<δ where • 1 −−−→ := c− N −M V ;A ZN −M,β (N − M )! , · Z V,A − −−−→ −M N1 ! · · · Ng ! N −M, N N −M ,β (5.33) • V ;A −−−→ := µ d− N −M −−−−→ −M N −M, N N −M β ( N Y j=N −M +1 e PN −M i=1 β (− β 2 V (λi )+ln |λj −λi |− 2 V (λj )) ). (5.34) . Convergence of eigenvalues to the support of the limiting measure We shall use Lemma 5.13 with f (λ1 , . . . , λN −M ) = PN i=N −M +1 gλi (λ1 , · · · 14 , λN −M ) with N X gλ (λ1 , · · · , λN −M ) := j=N −M +1 Note that kgλ k2L gλ λ is smooth for is of order N. close to As a consequence, β (− V (λ) + β ln |λ − λj|) . 2 c0 and λi , i ≤ N − M kf k2L is of order N M 2 in A, and such that λN −M +1 , . . . , λN for c0 . close to −−−→ d− N −M We rst estimate and then substitute the estimate into (5.32). By the concentration inequality, N Y −−−→ = d− N −M β e− 2 (N −M )V (λj) µV ;A −−−−→ −M N −M, N N −M ;β j=N −M +1 N Y = e −β 2 (N −M )V µV ;A N −M, ∗e CM 2 ≤ Ce ( −−−−→ N −M ;β N −M µ −−−−→ −M N −M, N N −M ;β PN −M ( e f (λi ) PN −M f (λi )−µ N −M i=1 ), N N −M, (e V ;A P −M ( N −−−−→ i=1 N −M ;β N −M f (λi )) i=1 N Y PN −M i=1 (λj) V ;A j=N −M +1 (e −β 2 N V (λj ) PN −M µV ;A )e N −M, ( −−−−→ N −M ;β N −M i=1 f (λi )) . j=N −M +1 (5.35) The last step is a consequence of concentration inequality, Lemma 5.13. We remark here in the following estimate the constant C may change line by line. Now we use the estimate of Lemma A.1, which is derived from Theorem 5.4. Indeed, since we assumed a neighborhood of A (for V analytic in a neighborhood of A, f is also analytic in [c0 − , c0 + ] at positive distance of A), so that we can use Lemma A.1 to deduce that V ;A µ −−−−→ NX −M −M N −M, N N −M ,β ( f (λi )) = (N − M )µ i=1 Next, we want to substitute −−−−→ −M eq, N N−M µ −−−−→ −M eq, N N−M by µeq (f (λ)) + O(M ). By Appendix A.1 in [BG13](i.e the smooth dependence), it is not hard to see(we point out here |µeq {f }−µ −−−−→ −M eq, N N−M (5.36) {f }| = |µeq,? {f }−µ −−−−→ −M eq, N N−M {f }| ≤ CM | µeq = µeq,? ): −−−−−→ N −M −? |. N −M (5.37) Combining (5.35), (5.32), (5.36), (5.37) gives us 2 FN,M Ξ (λN −M +1 , · · · , λN ) . CeCM ( N Y β e− 2 N V (λj ) ) j=N −M +1 × X −−−−→ ! −−−−−→ N − M ;A −−−→ exp (N − M )(µV c− − ? |) + O(M ) . eq {g} + CM | N −M N −M −M |N N −M −? |<δ (5.38) f (λi )) ), Convergence of eigenvalues to the support of the limiting measure 15 Now in order to establish our desired estimate: N Y 2 FN.M Ξ(λN −M +! , · · · , λN ) . CeCM ( CM 2 ≤ Ce ´ e β e− 2 N V (λj ) ) exp ((N − M )µeq {f }) j=N −M +1 − βN2M V (η)dµeq (η) −N e PN j=N −M +1 J V ;B (λj ) . (5.39) We need only establish the inequality: −−−−→ N −M X −−−−→ −M |N N −M −? |<δ 2 CM (N −M )| N −M −? | −−−→ e c− ≤ CeCM , N −M which is straightforward since −−−→ c− N −M (5.40) has a sub-Gaussian tail → ≤ Ce−cK c− K → − → − 2 K | K −? |2 +CK| K K −? | . (5.41) (5.41) follows from Theorem 5.4 and (5.19), (5.20), (5.21). FN,M LN,M From Proposition 5.15, we can easily obtain an upper bound on by using classical Laplace method: Proposition 5.16. Under Assumptions 1 and 2, 2 β FN,M LN,M . CeCM e− 2 N M Proof. ´ V (η)dµeq (η)−N M inf J V ;B 1 N M 2 The proof is straightforward since by Proposition 5.15 CM 2 − β 2 NM FN,M LN,M . Ce e ´ V (η)dµeq(η)−N M inf J V ;B ˆ c0 + −N J˜V ;B (x) −M β 2 V (x) e e c0 − 2 V from below, providing a term eCM J (c0 ) > 0, see [AGZ10, section 3.5.3] ˆ c0 + 1 ˜V ;B (λ) e−N J dλ ≈ √ . N c0 − where we can bound (recall we assume ˜00 , and use Laplace method for details) to get Remark 5.17. Note that if we would have assumed instead of J˜00 (c0 ) > 0 that for some q > 0 J˜00 (x) ' |x − c0 |q in a neighborhood of c0 , we would have obtained 2 β FN,M LN,M ≤ CeCM e− 2 N M ´ V (η)dµeq (η) 1 N M q and criticality would have occurred at β = 2/q. Propositions 5.16 and 5.7 give (2.4) since ;B ΦVN,M,β ≤ (2) βM (M −1) 2 ≤ C 0 (C 0 ) for some nite constant C 0. This concludes the proof. Hence, if GN,M FN,M LN,M 1 1 βM (M −1) 2 N M 2 N Mβ 2 is chosen small enough, (5.42) the result is proved. M dx Convergence of eigenvalues to the support of the limiting measure 5.3. Proof of . (2.5) Simply recall that in this case we have equality: ˆ V ;B ZN,β ΦV ;B V ;A N,M,β ZN,β When M = 1, 16 β Ξ(λN )e− 2 V (λN ) dλN . = YN,1 (5.43) [c0 −,c0 +] we combine the estimate of (5.14) and apply central limit theorem Lemma A.2. Then we get: FN,1 Ξ(λN ) ≈ e The estimate for GN,1 ´ −β 2 N V (η)dµeq (η) −J (λN ) e . (5.44) given in Proposition (5.7) holds. Thus,we get V ;B ZN,β ΦV ;B & V ;A N,1,β ZN,β & 1 ˆ ˜ e−N J (λN ) dλN , β N2 1 N β+1 2 [c0 −,c0 +] (5.45) . 6. Acknowledgments Part of this work was completed as part of the MIT SPUR program over the summer of 2013. AG was partially supported by the Simons Foundation and by NSF Grant DMS-1307704. Appendix A. Supplementary Lemmas A.1. How to make use of the correlator estimate. Here we prove the following lemma by using the estimate for correlator.This technique is standard, we include the proof for completeness.It also shows the reason why sometimes we need the assumption that a function is analytic analytic (near the A); it guarantees that we can use Stieltjes transform estimates. ;A Lemma A.1. Under the assumption in Theorem 5.4, let µVN,,β be the xed lling fractions measure, µeq, be its limiting measure, let h be a function that is holomorphic near A. Then, X ;A |µVN,,β ( h(λi )) − N µeq, (h)| . C. Proof. Using Cauchy's integral and the assumption h is holomorphic near nd a contour Γ s.t h(λ) = V ;A |µN,,β ( 1 2πi ¸ (A.1) A, we hξ . Thus Γ ξ−λ X h(λi )) − N µeq, (h)| X ;A . |Γ| sup{(|h(ξ)|)|µVN,,β ξ∈Γ 1 ξ − λi − N W−1 (ξ)|}, (A.2) . |Γ| sup{|h(ξ)||W (ξ) − N W−1 (ξ)|}. ξ∈Γ Our desired estimate follows from the expansion of the correlators given in Theorem 5.4. Convergence of eigenvalues to the support of the limiting measure A.2. Central limit for analytic functions. 17 We want to establish estimate (sim- ilar to the xed fractals central limit theorem in section 5.5 of [BG13]). It is essentially contained in[BG13], but we write down the proof to be self-contained. we remark this h must be homomorphic near the neighborhood of A(since we want to use the correlator estimate).Then we have: Lemma A.2. Let Assumption 1 and 2 hold, and h be holomorphic near the neighborhood of A, then: ˆ X ;A µVN,β {exp( Proof. h(λi ))} ≈ exp{N h(η)dµeq (η)}. (A.3) By the large deviation principle of the limiting measure: X ;A µVN,β {exp( h(λi ))} ≈ X V ;A →µ → c− {exp( h(λi ))}. − N N X → − |N N −? |<δ First, we calculate a lower bound. Let (A.4) N, N ,β − → − → N be such that | N N − ? | < Q N and → > cQ , c− N by Jensen's Inequality: X X µV ;A {exp( h(λi ))} ≥ exp(µV ;A { h(λi )}). → − → − N N N, N ,β (A.5) N, N ,β Next, by Lemma A.1, we can deduce the estimate: X − (h)| . C. ( h(λi )) − N µeq, → |µV ;A → − N N N, N ,β (A.6) N µeq, (h) depends smoothly on (see appendix A.1 of [BG13]) and µeq,? is µeq , we have: − → N − (h) − µ (h)| . C| − ? |. (A.7) |µeq, → eq N N N Using that exactly Now , combing (A.4), (A.5), (A.6), (A.7), we get: ˆ X ;A µVN,β {exp( h(λi ))} & exp{N h(η)dµeq (η)}. (A.8) The upper bound is based on the concentration equality for (xed fractals measure) and the explicit estimate for the partition function (N )! N1 !···Ng ! · Z V ;A → − N .Basically, N, N ,β concentration inequality gives the inverse direction of Jensen's inequality. First from concentration inequality, X X µV ;A {exp( h(λi ))} . exp(µV ;A { h(λi )}). → − → − N N N, N ,β (A.9) N, N ,β Now, combine (A.4), (A.6), (A.7), (A.9), and the estimate for the partition function, we get : X ;A µVN,β {exp( h(λi )))} X . → − (A.10) − → − → N N exp(−cN 2 | − ? |2 + CN | − ? |) · exp(N µeq (h)) . N N |N N −? |<δ Thus, we nally conclude by X → − |N N −? |<δ exp(−cN 2 | − → − → N N − ? |2 + CN | − ? |) . 1. N N (A.11) Convergence of eigenvalues to the support of the limiting measure 18 A.3. lemma for GN,1 . We remark the following lemma is follows almost exactly the same argument as the analysis for YN in the appendx A.3 in[BG11]. We include the proof for completeness. Lemma A.3. Given η > 0 and N large enough, support set A = ∪gh=1 Ah , β GN,1 ≥ eN (−η+inf ξ∈A J (ξ)+ 2 ´ N (η+inf ξ∈A J (ξ)+ β 2 GN,1 ≤ e Proof. ´ V (η)dµeq (η)) V (η)dµeq (η)) , (A.12) . δ > 0. By Theorem 1.1, the probability that LN −1 is of distance greater −Γδ (N −1)2 or equal to δ from µeq is smaller than e for some Γδ > 0. Therefore, when N is large enough, 1 GN,1 Let = × ˆ 1 dλN e− V ;A ZN −1,β N −1 Y Nβ 2 V dλi e− β |λN − λi |β e− 2 V (λi ) i=1 (N −1)β V 2 Y (λi ) |λi − λj |β 1≤i<j≤N −1 ˆ µVN;A −1,β ≤ e−Γδ N −1 Y A i=1 = (λN ) dλN e − (N −1)β V 2 (λN ) − β 2 V (λN ) e N −1 Y A |λN − λi | e i=1 ˆ N2 2 ! β −β 2 V (λi ) dξe− 2 V (ξ) eβ(N −1) supd(µ,µeq )<δ (− β + V (ξ) ´ β 2 + [ln |ξ−η|− 2 V (η)]dµ(η)) . A As in [[BG11], Appendix 3], note that for all probability measures ˆ on A: ˆ ln |ξ − η|dµ(η) ≤ A ln[max(|ξ − η|, ζ)]dµ(η), A while the function on the righthand side is continuous in ˆ µ and ξ, and thus ˆ ln[max(|ξ − η|, ζ)]dµ(η) = lim ζ→0 µ A ln |ξ − η|dµeq (η). A Therefore, ˆ lim sup sup δ→0 sup 1 V (ξ) ln |ξ − η| − V (η)dµ(η) − 2 2 β ξ∈A d(µ,µeq )<δ ≤ − inf J V ;A (ξ) ξ∈A β − 2 Thus, for any η0 > 0 and 1 GN,1 N ˆ . V (η)dµeq (η) large enough, 0 β ≤ eN (η −inf ξ∈A J (ξ)− 2 ´ V (η)dµeq (η)) . (A.13) Convergence of eigenvalues to the support of the limiting measure As for the upper bound, let > 0. For any + [a− h − , ah − ], there exists 19 δ > 0 such that the following holds by Jensen's inequality: 1 GN,1 ˆ = µVN;A −1,β dλN e A ˆ ≥ µVN;A −1,β − N2β V (λN ) N −1 Y ! β −β 2 V (λi ) |λN − λi | e x+ dλN e − N2β V (λN ) N −1 Y ! β −β 2 V (λi ) , |λN − λi | e i=1 PN −1 β ´ x+ β i=1 2 x− ln |ξ−λi |dξ− 2 V (λi ) x− βN ≥ 2e− 2 V (x)−N δ µVN;A −1,β e ´ 1 Since λ → 2 C ln |ξ − λi |dξ is bounded continuous on A, LN −1 → µeq , for any given η > 0, when N large enough, 1 GN,1 ≥ 2e− βN 2 , i=1 V (x)−2N δ (N −1) e β ≥ e−N (η+inf ξ∈A J (ξ)+ 2 ´ ´ β 2 ´ x+ ( x− V (η)dµeq (η)) . by convergence of ln |ξ−η|dξ− β 2 V (η))dµeq (η) , . References [ACKM93] J. 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