庞加莱猜想证明后最新进展文献题录 邵伟文 中国科学院国家科学图书馆 庞加莱猜想在俄罗斯数学家佩雷尔曼的三篇研究报告刊登之后被证实已经获得了证明,此后更进一步的研究进展有如下文献: Record 1 of 84 Author(s): Ni, L (Ni, Lei); Wallach, N (Wallach, Nolan) Title: On Four-Dimensional Gradient Shrinking Solitons Source: INTERNATIONAL MATHEMATICS RESEARCH NOTICES: Art. No. rnm152 2008 Abstract: In this paper, we classify the four-dimensional gradient shrinking solitons under certain curvature conditions satisfied by all solitons arising from finite-time singularities of Ricci flow on compact four-manifolds with positive isotropic curvature. As a corollary, we generalize a result of Perelman on three-dimensional gradient shrinking solitons to dimension four. Times Cited: 0 DOI: 10.1093/imrn/rnm152 Record 2 of 84 Author(s): Wang, B (Wang, Bing) Title: On the Conditions to Extend Ricci Flow Source: INTERNATIONAL MATHEMATICS RESEARCH NOTICES: Art. No. rnn012 2008 Abstract: Consider {(M-n, g(t)), 0 = t T infinity} as an unnormalized Ricci flow solution:. partial derivative g(ij)/partial derivative t = -2R(ij) for t epsilon . In further results from may be found. In particular, there we construct short time solutions to Ricci flow for a class of compact Riemannian manifolds with isolated conelike singularities. The resulting solutions satisfy a bound of this form ( the speed is bounded by c/t for some time interval t is an element of (0, T)). Times Cited: 0 DOI: 10.1093/imrn/rnn097 Record 5 of 84 Author(s): Guo, HX (Guo, Hongxin) Title: AREA GROWTH RATE OF THE LEVEL SURFACE OF THE POTENTIAL FUNCTION ON THE 3-DIMENSIONAL STEADY GRADIENT RICCI SOLITON Source: PROCEEDINGS OF THE AMERICAN MATHEMATICAL SOCIETY, 137 (6): 2093-2097 2009 Abstract: In this short note we show that on a 3-dimensional steady gradient Ricci soliton with positive curvature and which is kappa-noncollapsed on all scales, the scalar curvature and the mean curvature of the level surface of the potential function both decay linearly. Consequently we prove that the area of the level surface grows linearly. Times Cited: 0 Record 6 of 84 Author(s): Vacaru, SI (Vacaru, Sergiu I.) Title: Nonholonomic Ricci Flows, Exact Solutions in Gravity, and Symmetric and Nonsymmetric Metrics Source: INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS, 48 (2): 579-606 FEB 2009 Abstract: We provide a proof that nonholonomically constrained Ricci flows of ( pseudo) Riemannian metrics positively result into nonsymmetric metrics ( as explicit examples, we consider flows of some physically valuable exact solutions in general relativity). There are constructed and analyzed three classes of solutions of Ricci flow evolution equations defining nonholonomic deformations of Taub NUT, Schwarzschild, solitonic and pp-wave symmetric metrics into nonsymmetric ones. Times Cited: 0 DOI: 10.1007/s10773-008-9841-8 Record 7 of 84 Author(s): Freed, DS (Freed, Daniel S.) Title: REMARKS ON CHERN-SIMONS THEORY Source: BULLETIN OF THE AMERICAN MATHEMATICAL SOCIETY, 46 (2): 221-254 2009 Abstract: The classical Chern-Simons invariant is the basis for a 3-dimensional topological quantum field theory. We describe some of the mathematical structure which has been built around this and other topological field theories. We include, in the introduction and the last section, some general discussion about the current interaction between geometry and quantum theories of fields and gravity. Times Cited: 0 Record 8 of 84 Author(s): Gu, HL (Gu, Hui-Ling); Zhu, XP (Zhu, Xi-Ping) Title: The existence of Type II singularities for the Ricci flow on Sn+1 Source: COMMUNICATIONS IN ANALYSIS AND GEOMETRY, 16 (3): 467-494 JUL 2008 Abstract: In this paper, we prove the existence of Type II singularities for the Ricci flow on Sn+1 for all n = 2. This also gives an affirmative answer to the degenerate neckpinch conjecture of Hamilton . Times Cited: 0 Record 9 of 84 Author(s): Hamilton, R (Hamilton, Richard); Sesum, N (Sesum, Natasa) Title: PROPERTIES OF THE SOLUTIONS OF THE CONJUGATE HEAT EQUATIONS Source: AMERICAN JOURNAL OF MATHEMATICS, 131 (1): 153-169 FEB 2009 Abstract: In this paper we consider the class A of those solutions u(x,t) to the conjugate heat equation partial derivative/partial derivative tu = -Delta u + Ru on compact Kahler manifolds M with c(1) 0 (where g(t) changes by the unnormalized Kahler Ricci flow, blowing up at T infinity), which satisfy Perelman's differential Harnack inequality (6) on . We show A is nonempty. If vertical bar Ric (g(t))vertical bar = C/T-1, which is always true if we have a type 1 singularity, we prove the solution u(x, t) satisfies the elliptic type Harnack inequality, with the constants that are uniform in time. If the flow g(t) has a type I singularity at T. then A has exactly one element. Times Cited: 0 Record 10 of 84 Author(s): Zhang, QS (Zhang, Qi S.) Title: STRONG NONCOLLAPSING AND UNIFORM SOBOLEV INEQUALITIES FOR RICCI FLOW WITH SURGERIES Source: PACIFIC JOURNAL OF MATHEMATICS, 239 (1): 179-200 JAN 2009 Abstract: We prove a uniform Sobolev inequality for Ricci flow that is independent of the number of surgeries. As an application, under fewer assumptions, we derive a noncollapsing result stronger than Perelman's kappa-noncollapsing result with surgery. The proof is shorter and seems more accessible. The result also improves some earlier ones where the Sobolev inequality depended on the number of surgeries. Times Cited: 0 Record 11 of 84 Author(s): Suneeta, V (Suneeta, V.) Title: Investigating the off-shell stability of anti-de Sitter space in string theory Source: CLASSICAL AND QUANTUM GRAVITY, 26 (3): Art. No. 035023 FEB 7 2009 Abstract: We propose an investigation of stability of vacua in string theory by studying their stability with respect to a (suitable) world-sheet renormalization group (RG) flow. We prove the geometric stability of (Euclidean) anti-de Sitter (AdS) space (i.e., H-n) with respect to the simplest RG flow in closed string theory, the Ricci flow. AdS space is not a fixed point of the Ricci flow. We therefore choose an appropriate flow for which it is a fixed point, prove a linear stability result for AdS space with respect to this flow and then show that this implies its geometric stability with respect to the Ricci flow. The techniques used can be generalized to RG flows involving other fields. We also discuss tools from the mathematics of geometric flows that can be used to study stability of string vacua. Times Cited: 0 DOI: 10.1088/0264-9381/26/3/035023 Record 12 of 84 Author(s): Ni, L (Ni, Lei); Wallach, N (Wallach, Nolan) Title: ON A CLASSIFICATION OF GRADIENT SHRINKING SOLITONS Source: MATHEMATICAL RESEARCH LETTERS, 15 (5-6): 941-955 SEP-NOV 2008 Abstract: The main purpose of this article is to provide an alternate proof to a result of Perelman on gradient shrinking solitons. Moreover in dimension three our proof generalizes Perelman's result by removing the K-non-collapsing assumption and allowing general curvature growth. The method also allows us to prove a classification result on gradient shrinking solitons with vanishing Weyl curvature tensor in high dimensions, which includes the rotationally symmetric ones. Times Cited: 2 Record 13 of 84 Author(s): Bohm, C (Boehm, Christoph); Wilking, B (Wilking, Burkhard) Title: Manifolds with positive curvature operators are space forms Source: ANNALS OF MATHEMATICS, 167 (3): 1079-1097 MAY 2008 Times Cited: 3 Record 14 of 84 Author(s): Streets, J (Streets, Jeffrey) Title: Singularities of renormalization group flows Source: JOURNAL OF GEOMETRY AND PHYSICS, 59 (1): 8-16 JAN 2009 Abstract: We discuss singularity formation in certain renormalization group flows. Special cases are the Ricci Yang-Mills and B-field flows. We point out some results suggesting that topological hypotheses can make RG flows much less singular than Ricci flow. In particular we show that for rotationally symmetric initial data on S-2 x S-1 one gets long time existence and convergence of RYM flow, in stark contrast to the case for Ricci flow . Other results are given which allow one to rule out many singularity models under strictly topological hypotheses. A conjectural picture of singularity formation for RG flow on 3-manifolds is given. (C) 2008 Elsevier B.V. All rights reserved. Times Cited: 0 DOI: 10.1016/j.geomphys.2008.08.002 Record 15 of 84 Author(s): Phong, DH (Phong, D. H.); Song, J (Song, Jian); Sturm, J (Sturm, Jacob); Weinkove, B (Weinkove, Ben) Title: The Kahler-Ricci flow with positive bisectional curvature Source: INVENTIONES MATHEMATICAE, 173 (3): 651-665 SEP 2008 Abstract: We show that the Kahler-Ricci flow on a manifold with positive first Chern class converges to a Kahler-Einstein metric assuming positive bisectional curvature and certain stability conditions. Times Cited: 0 DOI: 10.1007/s00222-008-0134-x Record 16 of 84 Author(s): Huisken, G (Huisken, Gerhard); Sinestrari, C (Sinestrari, Carlo) Title: Mean curvature flow with surgeries of two-convex hypersurfaces Source: INVENTIONES MATHEMATICAE, 175 (1): 137-221 JAN 2009 Times Cited: 0 DOI: 10.1007/s00222-008-0148-4 Record 17 of 84 Author(s): Husain, V (Husain, Viqar); Seahra, SS (Seahra, Sanjeev S.) Title: Ricci flows, wormholes and critical phenomena Source: CLASSICAL AND QUANTUM GRAVITY, 25 (22): Art. No. 222002 NOV 21 2008 Abstract: We study the evolution of wormhole geometries under the Ricci flow using numerical methods. Depending on values of initial data parameters, wormhole throats either pinch off or evolve to a monotonically growing state. The transition between these two behaviors exhibits a form of critical phenomena reminiscent of that observed in gravitational collapse. Similar results are obtained for initial data that describe space bubbles attached to asymptotically flat regions. Our numerical methods are applicable to 'matter-coupled' Ricci flows derived from conformal invariance in string theory. Times Cited: 0 DOI: 10.1088/0264-9381/25/22/222002 Record 18 of 84 Author(s): Astakhov, V (Astakhov, Vadim) Title: Mind Uploading and Resurrection of Human Consciousness Place for Science? Source: NEUROQUANTOLOGY, 6 (3): 245-261 2008 Abstract: Brain trauma often affects memories, perceptions and many other cognitive functions which all together form human mind. Modern medicine tries to provide technologies which can heal damaged brain and recover stream of consciousness. In this paper, I performed simulation experiment to analyze hypothetical process of mind recovery through uploading to an artificial environment. Neuroprosthesis, brain-computer interface or brain transplant might be the candidates for such migration. A term- Mind uploading was introduced to define process where core vital functions migrate from the human brain to an artificial environment. To simulate the process, I suggest a topological approach which is based on a formalism of information geometry. Geometrical formalism let me simulate a simple toy mind as geometrical structures. Also, it gives powerful geometrical and topological methods for analysis of the information flows in arbitrary complex system. The approach leads me to insight of using holographic analogy for the mind migration to an artificial environment. The concept of holography is well known in optics where localized 3D shape can be recorded and later reconstructed by 2D dimensional hologram. I am using that analogy to represents the toy mind functions as a geometrical shape on information manifold. Distributed holographic representation can be created for such shape. Then holographic reconstruction process provides an algorithm to reconstruct original system. Thus the migration from original to an artificial environment and back can be seen as a holography on information manifold. Interactions between brain and an artificial environment are modeled as an entropy flow which is defined as a geometrical flow on information manifold. Such flow is an analogy of holography recording for the toy mind. The opposite process of holography reconstruction is modeled by none-local Hamiltonians defined on information manifold. The simulated process illustrate a way to restore stream of consciousness which is lost due to brain damage, degeneration or decay. At the same, the simulation demonstrated that certain physical limitations will constraint such migration. Times Cited: 0 Record 19 of 84 Author(s): Chen, XX (Chen, Xiuxiong); Li, HZ (Li, Haozhao) Title: The Kahler-Ricci flow on Kahler manifolds with 2-non-negative traceless bisectional curvature operator Source: CHINESE ANNALS OF MATHEMATICS SERIES B, 29 (5): 543-556 SEP 2008 Abstract: The authors show that the 2-non-negative traceless bisectional curvature is preserved along the Kahler-Ricci flow. The positivity of Ricci curvature is also preserved along the Kahler-Ricci flow with 2-non-negative traceless bisectional curvature. As a corollary, the Kahler-Ricci flow with 2-non-negative traceless bisectional curvature will converge to a Kahler-Ricci soliton in the sense of Cheeger-Groniov-Hausdorff topology if complex dimension n = 3. Times Cited: 0 DOI: 10.1007/s11401-007-0294-9 Record 20 of 84 Author(s): Brendle, S (Brendle, Simon); Schoen, R (Schoen, Richard) Title: Manifolds with 1/4-pinched curvature are space forms Source: JOURNAL OF THE AMERICAN MATHEMATICAL SOCIETY, 22 (1): 287-307 2009 Times Cited: 0 Record 21 of 84 Author(s): Maschler, G (Maschler, Gideon) Title: Special Kahler-Ricci potentials and Ricci solitons Source: ANNALS OF GLOBAL ANALYSIS AND GEOMETRY, 34 (4): 367-380 NOV 2008 Abstract: On a manifold of dimension at least six, let (g, tau) be a pair consisting of a Kahler metric g which is locally Kahler irreducible, and a nonconstant smooth function tau. Off the zero set of tau, if the metric (g) over cap = g/tau(2) is a gradient Ricci soliton which has soliton function 1/tau, we show that (g) over cap is Kahler with respect to another complex structure, and locally of a type first described by Koiso, and also Cao. Moreover, tau is a special Kahler- Ricci potential, a notion defined in earlier works of Derdzinski and Maschler. The result extends to dimension four with additional assumptions. We also discuss a Ricci-Hessian equation, which is a generalization of the soliton equation, and observe that the set of pairs ( g, t) satisfying a Ricci-Hessian equation is invariant, in a suitable sense, under the map (g, tau) - ((g) over cap, 1/tau). Times Cited: 0 DOI: 10.1007/s10455-008-9114-z Record 22 of 84 Author(s): Barbosa, ER (Barbosa, Ezequiel R.); Montenegro , M ( Montenegro , Marcos) Title: The second Sobolev best constant along the Ricci flow Source: BULLETIN OF THE BRAZILIAN MATHEMATICAL SOCIETY, 39 (3): 427-445 SEP 2008 Abstract: In this work we present some properties satisfied by the second L-2-Riemannian Sobolev best constant along the Ricci flow on compact manifolds of dimensions n = 4. We prove that, along the Ricci flow g(t), the second best constant B-0(2, g(t)) depends continuously on t and blows-up in finite time. In certain cases, the speed of the explosion is, at least, the same one of the curvature operator. We also show that, on manifolds with positive curvature operator or pointwise 1/4-pinched curvature, one of the situations holds: B-0(2, g(t)) converges to an explicit constant or extremal functions there exists for t large. Times Cited: 0 Record 23 of 84 Author(s): Marzuoli, A (Marzuoli, Annalisa) Editor(s): Lupacchini, R; Corsi, G Title: Toy models in physics and the reasonable effectiveness of mathematics Source: DEDUCTION, COMPUTATION, EXPERIMENT: EXPLORING THE EFFECTIVENESS OF PROOF: 49-64 2008 Times Cited: 0 Record 24 of 84 Author(s): Topping, P (Topping, Peter) Title: Relating diameter and mean curvature for submanifolds of Euclidean space Source: COMMENTARII MATHEMATICI HELVETICI, 83 (3): 539-546 2008 Abstract: Given a closed in-dimensional manifold W immersed in R-n, we estimate its diameter d in terms of its mean curvature H by d = C(m)integral(M)vertical bar H vertical bar(m-1)(d mu). Times Cited: 0 Record 25 of 84 Author(s): Garfinkle, D (Garfinkle, David); Isenberg, J (Isenberg, James) Title: The modeling of degenerate neck pinch singularities in Ricci flow by Bryant solitons Source: JOURNAL OF MATHEMATICAL PHYSICS, 49 (7): Art. No. 073505 JUL 2008 Abstract: In earlier work, carrying out numerical simulations of the Ricci flows of families of rotationally symmetric geometries on S-3, we have found strong support for the contention that (at least in the rotationally symmetric case) the Ricci flow for a critical initial geometry-one which is at the transition point between initial geometries (on S-3) whose volume-normalized Ricci flows develop a singular neck pinch, and other initial geometries whose volume-normalized Ricci flows converge to a round sphere-evolves into a degenerate neck pinch. That is, we have seen in this earlier work that the Ricci flows for the critical geometries become locally cylindrical in a neighborhood of the initial pinching and have the maximum amount of curvature at one or both of the poles. Here, we explore the behavior of these flows at the poles and find strong support for the conjecture that the Bryant steady solitons accurately model this polar flow. (C) 2008 American Institute of Physics. Times Cited: 0 DOI: 10.1063/1.2948953 Record 26 of 84 Author(s): Sesum, N (Sesum, Natasa); Tian, G (Tian, Gang) Title: Bounding scalar curvature and diameter along the Kahler Ricci flow (after perelman) Source: JOURNAL OF THE INSTITUTE OF MATHEMATICS OF JUSSIEU, 7 (3): 575-587 JUL 2008 Abstract: In this short note we present a result of Perelman with detailed proof. The result states that if g(t) is the Kahler Ricci flow on a compact, Kahler manifold M with c(1)(M) 0, the scalar curvature and diameter of (M, g(t)) stay uniformly bounded along the flow, for t epsilon . The picture we give allows one to easily extend the proofs of derivative estimates and compactness of solutions to the case of a connection with torsion. We also examine gradient properties of this flow. Indeed it was shown in Oliynyk et al. (see the citation above) that the monotonicity of Perelman's F-functional extends to the case of a connection with torsion. We show that the expander entropy of Feldman, Ilmanen, and Ni also extends to the connection Ricci flow. (C) 2008 Elsevier B.V. All rights reserved. Times Cited: 0 DOI: 10.1016/j.geomphys.2008.02.010 Record 28 of 84 Author(s): Woolgar, E (Woolgar, E.) Title: Some applications of Ricci flow in physics Source: CANADIAN JOURNAL OF PHYSICS, 86 (4): 645-651 APR 2008 Abstract: I discuss certain applications of the Ricci flow in physics. I first review how it arises in the renormalization group (RG) flow of a nonlinear sigma model. I then review the concept of a Ricci soliton and recall how a soliton was used to discuss the RG flow of mass in two dimensions. I then present recent results obtained with Oliynyk on the flow of mass in higher dimensions. The final section discusses how Ricci flow may arise in general relativity, particularly for static metrics. Times Cited: 0 DOI: 10.1139/P07-146 Record 29 of 84 Author(s): Dai, XZ (Dai, Xianzhe); Wang, XD (Wang, Xiaodong); Wei, GF (Wei, Guofang) Title: On the variational stability of Kahler-Einstein metrics Source: COMMUNICATIONS IN ANALYSIS AND GEOMETRY, 15 (4): 669-693 OCT 2007 Abstract: Using spin(c) structure we prove that Kahler-Einstein metrics with non-positive scalar curvature are stable (in the direction of changes in conformal structures) as the critical points of the total scalar curvature functional. Moreover, if all infinitesimal complex deformations of the complex structure are integrable, then the Kahler-Einstein metric is a local maximal of the Yamabe invariant, and its volume is a local minimum among all metrics with scalar curvature bigger or equal to the scalar curvature of the Kahler-Einstein metric. Times Cited: 0 Record 30 of 84 Author(s): Angenent, SB (Angenent, Sigurd B.); Knopf, D (Knopf, Dan) Title: Precise asymptotics of the Ricci flow neckpinch Source: COMMUNICATIONS IN ANALYSIS AND GEOMETRY, 15 (4): 773-844 OCT 2007 Abstract: The best known finite-time local Ricci flow singularity is the neckpinch, in which a proper subset of the manifold becomes geometrically close to a portion of a shrinking cylinder. In this paper, we prove precise asymptotics for rotationally-symmetric Ricci flow neckpinches. We then compare these rigorous results with formal matched asymptotics for fully general neckpinch singularities. Times Cited: 2 Record 31 of 84 Author(s): Ecker, K (Ecker, Klaus) Title: A formula relating entropy monotonicity to Harnack inequalities Source: COMMUNICATIONS IN ANALYSIS AND GEOMETRY, 15 (5): 1025-1061 DEC 2007 Times Cited: 0 Record 32 of 84 Author(s): Castro, C (Castro, Carlos) Title: The Euclidean gravitational action as black hole entropy, singularities, and spacetime voids Source: JOURNAL OF MATHEMATICAL PHYSICS, 49 (4): Art. No. 042501 APR 2008 Abstract: We argue why the static spherically symmetric vacuum solutions of Einstein's equations described by the textbook Hilbert metric g(mu nu)(r) is not diffeomorphic to the metric g(mu nu)(vertical bar r vertical bar) corresponding to the gravitational field of a point mass delta function source at r=0. By choosing a judicious radial function R(r)=r+ 2G vertical bar M vertical bar Theta(r) involving the Heaviside step function, one has the correct boundary condition R(r=0)=0, while displacing the horizon from r= 2G vertical bar M vertical bar to a location arbitrarily close to r=0 as one desires, r(h)- 0, where stringy geometry and quantum gravitational effects begin to take place. We solve the field equations due to a delta function point mass source at r=0, and show that the Euclidean gravitational action (in h units) is precisely equal to the black hole entropy (in Planck area units). This result holds in any dimensions D = 3. In the Reissner-Nordstrom (massive charged) and Kerr-Newman black hole case (massive rotating charged) we show that the Euclidean action in a bulk domain bounded by the inner and outer horizons is the same as the black hole entropy. When one smears out the point-mass and point-charge delta function distributions by a Gaussian distribution, the area-entropy relation is modified. We postulate why these modifications should furnish the logarithmic corrections (and higher inverse powers of the area) to the entropy of these smeared black holes. To finalize, we analyze the Bars-Witten stringy black hole in 1+1 dimension and its relation to the maximal acceleration principle in phase spaces and Finsler geometries. (c) 2008 American Institute of Physics. Times Cited: 1 DOI: 10.1063/1.2898115 Record 33 of 84 Author(s): Vacaru, SI (Vacaru, Sergiu I.) Title: Nonholonomic Ricci flows. II. Evolution equations and dynamics Source: JOURNAL OF MATHEMATICAL PHYSICS, 49 (4): Art. No. 043504 APR 2008 Abstract: This is the second paper in a series of works devoted to nonholonomic Ricci flows. By imposing nonintegrable (nonholonomic) constraints on the Ricci flows of Riemannian metrics, we can model mutual transforms of generalized Finsler-Lagrange and Riemann geometries. We verify some assertions made in the first partner paper and develop a formal scheme in which the geometric constructions with Ricci flow evolution are elaborated for canonical nonlinear and linear connection structures. This scheme is applied to a study of Hamilton 's Ricci flows on nonholonomic manifolds and related Einstein spaces and Ricci solitons. The nonholonomic evolution equations are derived from Perelman's functionals which are redefined in such a form that can be adapted to the nonlinear connection structure. Next, the statistical analogy for nonholonomic Ricci flows is formulated and the corresponding thermodynamical expressions are found for compact configurations. Finally, we analyze two physical applications, the nonholonomic Ricci flows associated with evolution models for solitonic pp-wave solutions of Einstein equations, and compute the Perelman's entropy for regular Lagrange and analogous gravitational systems. (C) 2008 American Institute of Physics. Times Cited: 3 DOI: 10.1063/1.2899316 Record 34 of 84 Author(s): Futer, D (Futer, David); Kalfagianni, E (Kalfagianni, Efstratia); Purcell, JS (Purcell, Jessica S.) Title: Dehn filling, volume, and the Jones polynomial Source: JOURNAL OF DIFFERENTIAL GEOMETRY, 78 (3): 429-464 MAR 2008 Abstract: Given a hyperbolic 3-manifold with torus boundary, we bound the change in volume under a Dehn filling where all slopes have length at least 2 pi. This result is applied to give explicit diagrammatic bounds on the volumes of many knots and links, as well as their Dehn fillings and branched covers. Finally, we use this result to bound the volumes of knots in terms of the coefficients of their Jones polynomials. Times Cited: 2 Record 35 of 84 Author(s): Chu , SC ( Chu , Sun-Chin) Title: Space-time approach to perelman's L-geodesics and an analogy between Perelman's reduced volume and Huisken's monotonicity formula Source: TAIWANESE JOURNAL OF MATHEMATICS, 12 (1): 255-268 FEB 2008 Abstract: From the viewpoint of space-time geometry and the trick of space-time track, the author would like to investigate the L-geodesics, Perelman's reduced volume and Huisken's monotonicity formula. Times Cited: 0 Record 36 of 84 Author(s): Kholodenko, AL (Kholodenko, Arkady L.) Title: Towards physically motivated proofs of the Poincare and geometrization conjectures Source: JOURNAL OF GEOMETRY AND PHYSICS, 58 (2): 259-290 FEB 2008 Abstract: Although the Poincare and the geometrization conjectures were recently proved by Perelman, the proof relies heavily on properties of the Ricci flow previously investigated in great detail by Hamilton . Physical realization of such a flow can be found, for instance, in the work by Friedan . In his work the renormalization group flow for a nonlinear sigma model in 2 + epsilon dimensions was obtained and studied. For epsilon = 0, by approximating the beta-function for such a flow by the lowest order terms in the sigma model coupling constant, the equations for Ricci flow are obtained. In view of such an approximation, the existence of this type of flow in Nature is questionable. In this work, we find totally independent justification for the existence of Ricci flows in Nature. This is achieved by developing a new formalism extending the results of two-dimensional conformal field theories (CFT's) to three and higher dimensions. Equations describing critical dynamics of these CFT's are examples of the Yamabe and Ricci flows realizable in Nature. Although in the original works by Perelman some physically motivated arguments can be found, their role in his proof remain rather obscure. In this paper, steps are made toward making these arguments more explicit, thus creating an opportunity for developing alternative, more physically motivated, proofs of the Poincare and geometrization conjectures. (C) 2007 Elsevier B.V. All rights reserved. Times Cited: 2 DOI: 10.1016/j.geomphys.2007.11.003 Record 37 of 84 Author(s): Wylie, W (Wylie, William) Title: Complete shrinking Ricci solitons have finite fundamental group Source: PROCEEDINGS OF THE AMERICAN MATHEMATICAL SOCIETY, 136 (5): 1803-1806 2008 Abstract: We show that if a complete Riemannian manifold supports a vector field such that the Ricci tensor plus the Lie derivative of the metric with respect to the vector field has a positive lower bound, then the fundamental group is finite. In particular, it follows that complete shrinking Ricci solitons and complete smooth metric measure spaces with a positive lower bound on the Bakry-Emery tensor have finite fundamental group. The method of proof is to generalize arguments of Garcia-Rio and Fernandez-Lopez in the compact case. Times Cited: 3 Record 38 of 84 Author(s): Buchert, T (Buchert, Thomas) Title: Dark Energy from structure: a status report Source: GENERAL RELATIVITY AND GRAVITATION, 40 (2-3): 467-527 FEB 2008 Abstract: The effective evolution of an inhomogeneous universe model in any theory of gravitation may be described in terms of spatially averaged variables. In Einstein's theory, restricting attention to scalar variables, this evolution can be modeled by solutions of a set of Friedmann equations for an effective volume scale factor, with matter and backreaction source terms. The latter can be represented by an effective scalar field (morphon field) modeling Dark Energy. The present work provides an overview over the Dark Energy debate in connection with the impact of inhomogeneities, and formulates strategies for a comprehensive quantitative evaluation of backreaction effects both in theoretical and observational cosmology. We recall the basic steps of a description of backreaction effects in relativistic cosmology that lead to refurnishing the standard cosmological equations, but also lay down a number of challenges and unresolved issues in connection with their observational interpretation. The present status of this subject is intermediate: we have a good qualitative understanding of backreaction effects pointing to a global instability of the standard model of cosmology; exact solutions and perturbative results modeling this instability lie in the right sector to explain Dark Energy from inhomogeneities. It is fair to say that, even if backreaction effects turn out to be less important than anticipated by some researchers, the concordance high-precision cosmology, the architecture of current N-body simulations, as well as standard perturbative approaches may all fall short in correctly describing the Late Universe. Times Cited: 21 DOI: 10.1007/s10714-007-0554-8 Record 39 of 84 Author(s): Behrstock, JA (Behrstock, Jason A.); Neumann, WD (Neumann, Walter D.) Title: Quasi-isometric classification of graph manifold groups Source: DUKE MATHEMATICAL JOURNAL, 141 (2): 217-240 FEB 1 2008 Abstract: We show that the fundamental groups of any two closed irreducible nongeometric graph manifolds are quasi-isometric. We also classify the quasi-isometry types of fundamental groups of graph manifolds with boundary in terms of certain finite two-colored graphs. A corollary is the quasi-isometric classification of Artin groups whose presentation graphs are trees. In particular, any two right-angled Artin groups whose presentation graphs are trees of diameter greater than 2 are quasi-isometric; further, this quasi-isometry class does not include any other right-angled Artin groups. Times Cited: 0 Record 40 of 84 Author(s): Bridson, M (Bridson, Martin); Hinkkanen, A (Hinkkanen, Aimo); Martin, G (Martin, Gaven) Title: Quasiregular self-mappings of manifolds and word hyperbolic groups Source: COMPOSITIO MATHEMATICA, 143 (6): 1613-1622 NOV 2007 Abstract: An extension of a result of Sela shows that if Gamma is a torsion-free word hyperbolic group, then the only homomorphisms Gamma-Gamma with finite-index image are the automorphisms. It follows from this result and properties of quasiregular mappings, that if M is a closed Riemannian n-manifold with negative sectional curvature (n not equal 4), then every quasiregular mapping f : M --M is a homeomorphism. In the constant-curvature case the dimension restriction is not necessary and Mostow rigidity implies that f is homotopic to an isometry. This is to be contrasted with the fact that every such manifold admits a non-homeomorphic light open self-mapping. We present similar results for more general quotients of hyperbolic space and quasiregular mappings between them. For instance, we establish that besides covering projections there are no pi(1)-injective proper quasiregular mappings f : M -- N between hyperbolic 3-manifolds M and N with non-elementary fundamental group. Times Cited: 0 DOI: 10.1112/S0010437X07003028 Record 41 of 84 Author(s): Fang, FQ (Fang, Fuquan); Zhang, YG (Zhang, Yuguang); Zhang, ZL (Zhang, Zhenlei) Title: Non-singular solutions to the normalized Ricci flow equation Source: MATHEMATISCHE ANNALEN, 340 (3): 647-674 MAR 2008 Abstract: In this paper, we study non-singular solutions to Ricci flow on a closed manifold of dimension at least 4. Amongst other things we prove that, if M is a closed 4-manifold on which the normalized Ricci flow exists for all time t 0 with uniformly bounded sectional curvature, then the Euler characteristic x( M) = 0. Moreover, the 4-manifold satisfies one of the followings (i) M is a shrinking Ricci soliton; ( ii) M admits a positive rank F-structure; ( iii) the Hitchin-Thorpe type inequality holds 2x( M) = 3| tau( M)| where x( M) (resp. tau( M)) is the Euler characteristic (resp. signature) of M. Times Cited: 1 DOI: 10.1007/s00208-007-0164-5 Record 42 of 84 Author(s): Kent, RP (Kent, Richard P.); Leininger, CJ (Leininger, Christopher J.) Editor(s): Dick, C; Gilman, J; Heinonen, J; Masur, H Title: Subgroups of mapping class groups from the geometrical viewpoint Source: In the Tradition of Ahlfors-Bers, IV, 432: 119-141 2007 Book series title: CONTEMPORARY MATHEMATICS SERIES Abstract: Once it is possible to translate any particular proof from one theory to another, then the analogy has ceased to be productive for this purpose; it would cease to be at all productive if at one point we had a meaningful and natural way of deriving both theories from a single one.... Gone is the analogy: gone are the two theories, their conflicts and their delicious reciprocal reflections, their furtive caresses, their inexplicable quarrels; alas, all is just one theory, whose majestic beauty can no longer excite us. Times Cited: 2 Record 43 of 84 Author(s): Ye, RG (Ye, Rugang) Title: On the l-function and the reduced volume of Perelman I Source: TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY, 360 (1): 507-531 2008 Abstract: The main purpose of this paper is to present a number of analytic and geometric properties of the iota- function and the reduced volume of Perelman, including in particular the monotonicity, the upper bound and the rigidities of the reduced volume. Times Cited: 0 Record 44 of 84 Author(s): Ye, RG (Ye, Rugang) Title: On the l-function and the reduced volume of Perelman II Source: TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY, 360 (1): 533-544 2008 Abstract: In this paper we present a major application of the l- function and the reduced volume of Perelman, namely their application to the analysis of the asymptotical limits of kappa- solutions of the Ricci flow. Times Cited: 0 Record 45 of 84 Author(s): Oliynyk, T (Oliynyk, T.); Suneeta, V (Suneeta, V.); Woolgar, E (Woolgar, E.) Title: Metric for gradient renormalization group flow of the worldsheet sigma model beyond first order Source: PHYSICAL REVIEW D, 76 (4): Art. No. 045001 AUG 2007 Abstract: Tseytlin has recently proposed that an action functional exists whose gradient generates to all orders in perturbation theory the renormalization group (RG) flow of the target space metric in the worldsheet sigma model. The gradient is defined with respect to a metric on the space of coupling constants which is explicitly known only to leading order in perturbation theory, but at that order is positive semidefinite, as follows from Perelman's work on the Ricci flow. This gives rise to a monotonicity formula for the flow which is expected to fail only if the beta function perturbation series fails to converge, which can happen if curvatures or their derivatives grow large. We test the validity of the monotonicity formula at next-to-leading order in perturbation theory by explicitly computing the second-order terms in the metric on the space of coupling constants. At this order, this metric is found not to be positive semidefinite. In situations where this might spoil monotonicity, derivatives of curvature become large enough for higher-order perturbative corrections to be significant. Times Cited: 3 DOI: 10.1103/PhysRevD.76.045001 Record 46 of 84 Author(s): Ni, L (Ni, Lei) Title: Mean value theorems on manifolds Source: ASIAN JOURNAL OF MATHEMATICS, 11 (2): 277-304 JUN 2007 Abstract: We derive several mean value formulae on manifolds, generalizing the classical one for harmonic functions on Euclidean spaces as well as the results of Schoen-Yau, Michael-Simon, etc, on curved Riemannian manifolds. For the heat equation a mean value theorem with respect to 'heat spheres' is proved for heat equation with respect to evolving Riemannian metrics via a space-time consideration. Some new monotonicity formulae are derived. As applications of the new local monotonicity formulae, some local regularity theorems concerning Ricci flow are proved. Times Cited: 1 Record 47 of 84 Author(s): Li, JF (Li, Jun-Fang) Title: Eigenvalues and energy functionals with monotonicity formulae under Ricci flow Source: MATHEMATISCHE ANNALEN, 338 (4): 927-946 AUG 2007 Abstract: In this note, we construct families of functionals of the type of F-functional and W- functional of Perelman. We prove that these newfunctionals are nondecreasing under the Ricci flow. As applications, we give a proof of the theorem that compact steady Ricci breathers must be Ricci-flat. Using these new functionals, we also give a new proof of Perelman's no non-trivial expanding breather theorem. Furthermore, we prove that compact expanding Ricci breathers must be Einstein by a direct method. In this note, we also extend Cao's methods of eigenvalues (in Math Ann 337(2), 2007) and improve their results. Times Cited: 1 DOI: 10.1007/s00208-007-0098-y Record 48 of 84 Author(s): Fenley, SR (Fenley, Sergio R.) Title: Laminar free hyperbolic 3-manifolds Source: COMMENTARII MATHEMATICI HELVETICI, 82 (2): 247-321 2007 Times Cited: 0 Record 49 of 84 Author(s): Kotschwar, BL (Kotschwar, Brett L.) Title: Hamilton 's gradient estimate for the heat kernel on complete manifolds Source: PROCEEDINGS OF THE AMERICAN MATHEMATICAL SOCIETY, 135 (9): 3013-3019 2007 Abstract: In this paper we extend a gradient estimate of R. Hamilton for positive solutions to the heat equation on closed manifolds to bounded positive solutions on complete, non-compact manifolds with Rc = - Kg. We accomplish this extension via a maximum principle of L. Karp and P. Li and a Berstein-type estimate on the gradient of the solution. An application of our result, together with the bounds of P. Li and S. T. Yau, yields an estimate on the gradient of the heat kernel for complete manifolds with non-negative Ricci curvature that is sharp in the order of t for the heat kernel on R-n. Times Cited: 0 Record 50 of 84 Author(s): Cao, HD (Cao, Huai-Dong); Sesum, N (Sesum, N.) Title: A compactness result for Kahler Ricci solitons Source: ADVANCES IN MATHEMATICS, 211 (2): 794-818 JUN 1 2007 Abstract: In this paper we prove a compactness result for compact Kahler Ricci gradient shrinking solitons. If (M-i, g(i)) is a sequence of Kahler Ricci solitons of real dimension n = 4, whose curvatures have uniformly bounded L-n/2 norms, whose Ricci curvatures are uniformly bounded from below and mu(g(i), 1/2)=, A (where mu is Perelman's functional), there is a subsequence (M-i, g(i)) converging to a compact orbifold (M infinity, g infinity) with finitely many isolated singularities, where g infinity is a Kahler Ricci soliton metric in an orbifold sense (satisfies a soliton equation away from singular points and smoothly extends in some gauge to a metric satisfying Kahler Ricci soliton equation in a lifting around singular points). Published by Elsevier Inc. Times Cited: 0 DOI: 10.1016/j.aim.2006.09.011 Record 51 of 84 Author(s): Ni, L (Ni, Lei) Title: A note on Perelman's LYH-type inequality Source: COMMUNICATIONS IN ANALYSIS AND GEOMETRY, 14 (5): 883-905 DEC 2006 Abstract: We give a proof to the Li-Yau-Hamilton-type inequality claimed by Perelman on the fundamental solution to the conjugate heat equation. The rest of the paper is devoted to improving the known differential inequalities of Li-Yau-Hamilton type via monotonicity formulae. Times Cited: 3 Record 52 of 84 Author(s): Flapan, E (Flapan, Erica); Howards, H (Howards, Hugh); Lawrence, D (Lawrence, Don); Mellor, B (Mellor, Blake) Title: Intrinsic linking and knotting of graphs in arbitrary 3-manifolds Source: ALGEBRAIC AND GEOMETRIC TOPOLOGY, 6: 1025-1035 2006 Abstract: We prove that a graph is intrinsically linked in an arbitrary 3-manifold M if and only if it is intrinsically linked in S-3. Also, assuming the Poincare Conjecture, we prove that a graph is intrinsically knotted in M if and only if it is intrinsically knotted in S-3. Times Cited: 0 DOI: 10.2140/agt.2006.6.1025 Record 53 of 84 Author(s): Atiyah, M Editor(s): Etingof, P; Retakh, V; Singer, IM Title: The interaction between geometry and physics Source: Unity of Mathematics - IN HONOR OF THE NINETIETH BIRTHDAY OF I.M. GELFAND , 244: 1-15 2006 Book series title: PROGRESS IN MATHEMATICS Times Cited: 0 Record 54 of 84 Author(s): Ma, L (Ma, Li) Title: Gradient estimates for a simple elliptic equation on complete non-compact Riemannian manifolds Source: JOURNAL OF FUNCTIONAL ANALYSIS, 241 (1): 374-382 DEC 1 2006 Abstract: In this paper, we study the local gradient estimate for the positive solution to the following equation: Delta u + au log u + bu = 0 in M, where a 0, b are real constants, M is a complete non-compact Riemannian manifold. Our result is optimal in the sense when (M, g) is a complete non-compact expanding gradient Ricci soliton. By definition, (M, g) is called an expanding gradient Ricci soliton if for some constant c 0, it satisfies that Rc = cg + D(2)f, where Rc is the Ricci curvature, and D(2)f is the Hessian of the potential function f on M. We show that for a complete non-compact Riemannian manifold (M, g), the local gradient bound of the function f = log u, where u is a positive solution to the equation above, is well controlled by some constants and the lower bound of the Ricci curvature. (C) 2006 Elsevier Inc. All rights reserved. Times Cited: 2 DOI: 10.1016/j.jfa.2006.06.006 Record 55 of 84 Author(s): Dunfield , NM (Dunfield, Nathan M.); Thurston, WP (Thurston, William P.) Title: Finite covers of random 3-manifolds Source: INVENTIONES MATHEMATICAE, 166 (3): 457-521 DEC 2006 Abstract: A 3-manifold is Haken if it contains a topologically essential surface. The Virtual Haken Conjecture posits that every irreducible 3-manifold with infinite fundamental group has a finite cover which is Haken. In this paper, we study random 3-manifolds and their finite covers in an attempt to shed light on this difficult question. In particular, we consider random Heegaard splittings by gluing two handlebodies by the result of a random walk in the mapping class group of a surface. For this model of random 3-manifold, we are able to compute the probabilities that the resulting manifolds have finite covers of particular kinds. Our results contrast with the analogous probabilities for groups coming from random balanced presentations, giving quantitative theorems to the effect that 3-manifold groups have many more finite quotients than random groups. The next natural question is whether these covers have positive betti number. For abelian covers of a fixed type over 3-manifolds of Heegaard genus 2, we show that the probability of positive betti number is 0. In fact, many of these questions boil down to questions about the mapping class group. We are led to consider the action of the mapping class group of a surface Sigma on the set of quotients pi(1)(Sigma)- Q. If Q is a simple group, we show that if the genus of Sigma is large, then this action is very mixing. In particular, the action factors through the alternating group of each orbit. This is analogous to Goldman's theorem that the action of the mapping class group on the SU(2) character variety is ergodic. Times Cited: 1 DOI: 10.1007/s0 0222-006-0001 -6 Record 56 of 84 Author(s): Ruan, QH (Ruan, Qi-Hua) Title: Bakry-Emery curvature operator and Ricci flow Source: POTENTIAL ANALYSIS, 25 (4): 399-406 DEC 2006 Abstract: In this paper, we introduce some techniques of Bakry-Emery curvature operator to Ricci flow and prove the evolution equation for the Bakry-Emery scalar curvature. As its application, we can easily derive the Perelman's entropy functional monotonicity formula. We also discuss some gradient estimates of Ricci curvature and L-2-estimates of scalar curvature. Times Cited: 1 DOI: 10.1007/s11118-006-9029-x Record 57 of 84 Author(s): Chen, BL (Chen, Bing-Long); Zhu, XP (Zhu, Xi-Ping) Title: Ricci flow with surgery on four-manifolds with positive isotropic curvature Source: JOURNAL OF DIFFERENTIAL GEOMETRY, 74 (2): 177-264 OCT 2006 Abstract: In this paper we study the Ricci flow on compact four-manifolds with positive isotropic curvature and with no essential incompressible space form. We establish a long-time existence result of the Ricci flow with surgery on four-dimensional manifolds. As a consequence, we obtain a complete proof to the main theorem of Hamilton in . During the proof we have actually provided, up to slight modifications, all necessary details for the part from Section 1 to Section 5 of Perelman's second paper on the Ricci flow to approach the Poincare conjecture. Times Cited: 4 Record 58 of 84 Author(s): Lin, WH (Lin, Wen-Hsiung) Title: Toward the Poincare Conjecture Source: TAIWANESE JOURNAL OF MATHEMATICS, 10 (5): 1109-1129 SEP 2006 Times Cited: 0 Record 59 of 84 Author(s): Chen, BL (Chen, Bing-Long); Zhu, XP (Zhu, Xi-Ping) Title: Uniqueness of the Ricci flow on complete noncompact manifolds Source: JOURNAL OF DIFFERENTIAL GEOMETRY, 74 (1): 119-154 SEP 2006 Abstract: The Ricci flow is an evolution system on metrics. For a given metric as initial data, its local existence and uniqueness on compact manifolds were first established by Hamilton . Later on, De Turck gave a simplified proof. In the later part of 80's, Shi generalized the local existence result to complete noncompact manifolds. However, the uniqueness of the solutions to the Ricci flow on complete noncompact manifolds is still an open question. In this paper, we give an affirmative answer for the uniqueness question. More precisely, we prove that the solution of the Ricci flow with bounded curvature on a complete noncompact manifold is unique. Times Cited: 3 Record 60 of 84 Author(s): Zhang, X (Zhang, Xi) Title: Compactness theorems for gradient Ricci solitons Source: JOURNAL OF GEOMETRY AND PHYSICS, 56 (12): 2481-2499 DEC 2006 Abstract: In this paper, we prove a compactness theorem for gradient Ricci solitons. Let (M-alpha, g(alpha)) be a sequence of compact gradient Ricci solitons of dimension n 4, whose curvatures have uniformly bounded L-n/(2) norms, whose Ricci curvatures are uniformly bounded from below, with uniformly lower bounded volume and with uniformly upper bounded diameter; then there must exist a subsequence (M-alpha, g(alpha)) converging to a compact orbifold (M-infinity, g(infinity)) with finitely many isolated singularities, where g(infinity) is a gradient Ricci solliton metric in an orbifold sense. (c) 2006 Elsevier B.V. All rights reserved. Times Cited: 0 DOI: 10.1016/j.geomphys.2006.01.004 Record 61 of 84 Author(s): Sesum, N (Sesum, Natasa) Title: Convergence of the Ricci flow toward a soliton Source: COMMUNICATIONS IN ANALYSIS AND GEOMETRY, 14 (2): 283-343 MAR 2006 Abstract: We will consider a tau-flow, given by the equation d/dt g(ij) = -2R(ij) + 1/tau g(ij) on a closed manifold M, for all times t is an element of to resolve William Thurston's Geometrization Conjecture for closed 3-manifolds by completing the program begun by Richard Hamilton. It is still too early to give an accurate and fair assessment of the full impact of Perelman's work. But in order to aid the many mathematicians who may be inspired by that work to look more closely at the Ricci flow, this does seem like an appropriate time to write a brief and purely expository introduction to the topic, intended for the non-expert. Readers desiring more information are encouraged to read the more advanced survey articles and , as well as to consult; Hamilton's and Perelman's original papers. Times Cited: 0 Record 79 of 84 Author(s): Ni, L Title: A monotonicity formula on complete Kahler manifolds with nonnegative bisectional curvature Source: JOURNAL OF THE AMERICAN MATHEMATICAL SOCIETY, 17 (4): 909-946 2004 Times Cited: 5 Record 80 of 84 Author(s): Angenent, S; Knopf, D Title: An example of neckpinching for Ricci Flow on Sn+1 Source: MATHEMATICAL RESEARCH LETTERS, 11 (4): 493-518 JUL 2004 Abstract: We give an example of a class of metrics on Sn+1 that evolve under the Ricci Flow into a neckpinch. We show that the solution has a Type I singularity, and that the length of the neck, i.e. the region where \Rm\ similar to (T-t)(-1), is bounded from below by croot (T - t) \ log(T - t) \ for some c 0. Times Cited: 7 Record 81 of 84 Author(s): Ni, L Title: The entropy formula for linear heat equation Source: JOURNAL OF GEOMETRIC ANALYSIS, 14 (1): 87-100 2004 Abstract: Me derive the entropy formula for the linear heat equation on general Riemannian manifolds and prove that it is monotone non-increasing on manifolds with nonnegative Ricci curvature. As applications, we study the relation between the value of entropy and the volume of balls of various scales. The results are simpler version, without Ricci flow, of Perelman's recent results on volume non-collapsing for Ricci flow oil compact manifolds. We also prove that if the entrop for the heal kernel achieves its maximum value zero at some positive time, oil any complete Riamannian manifold with nonnegative Ricci curvature if and only if the manifold is isometric to the Euclidean space. Times Cited: 8 Record 82 of 84 Author(s): Ni, L Title: The entropy formula for linear heat equation (vol 14, pg 87, 2004) Source: JOURNAL OF GEOMETRIC ANALYSIS, 14 (2): 369-374 2004 Abstract: We add two sections to and answer some questions asked there. In the first section we give another derivation of Theorem 1.1 of , which reveals the relation between the entropy formula, (1.4) of , and the well-known Li-Yau's gradient estimate. As a by-product we obtain the sharp estimates on 'Nash's entropy' for manifolds with nonnegative Ricci curvature. We also show that the equality holds in Li-Yau's gradient estimate, for some positive solution to the heat equation, at some positive time, implies that the complete Riemannian manifold with nonnegative Ricci curvature is isometric to R-n. In the second section we derive a dual entropy formula which, to some degree, connects Hamilton 's entropy, with Perelman's entropy in the case of Riemann surfaces. Times Cited: 6 Record 83 of 84 Author(s): Glickenstein, D Title: Precompactness of solutions to the Ricci flow in the absence of injectivity radius estimates Source: GEOMETRY TOPOLOGY, 7: 487-510 2003 Abstract: Consider a sequence of pointed n-dimensional complete Riemannian manifolds {(M-i; g(i)( t); O-i) g such that t is an element of are solutions to the Ricci flow and g(i)( t) have uniformly bounded curvatures and derivatives of curvatures. Richard Hamilton showed that if the initial injectivity radii are uniformly bounded below then there is a subsequence which converges to an n-dimensional solution to the Ricci flow. We prove a generalization of this theorem where the initial metrics may collapse. Without injectivity radius bounds we must allow for convergence in the Gromov-Hausdorff sense to a space which is not a manifold but only a metric space. We then look at the local geometry of the limit to understand how it relates to the Ricci flow. Times Cited: 5 Record 84 of 84 Author(s): Chow, B Title: On an alternate proof of Hamilton 's Matrix Harnack inequality of Li-Yau type for the Ricci Flow Source: INDIANA UNIVERSITY MATHEMATICS JOURNAL, 52 (4): 863-873 2003 Abstract: Based on a suggestion of Richard Hamilton, we propose an alternate proof of his matrix Harnack inequality for solutions of the Ricci flow with positive curvature operator. This Harnack inequality says that a certain endomorphism, consisting of an expression in the curvature and its first two covariant derivatives, of the bundle of 2-forms Whitney sum 1-forms is nonnegative. The idea is to consider the 2-form which minimizes the associated quadratic form to obtain a symmetric 2-tensor. A long but relatively straightforward computation implies this 2-tensor is a supersolution to the heat-type equation. An application of the maximum principle should then imply the result. Times Cited: 0 附: 佩雷尔曼的研究报告: 1. arXiv:math/0307245 Title: Finite extinction time for the solutions to the Ricci flow on certain three-manifolds Authors: Grisha Perelman Comments: 7 pages Subjects: Differential Geometry (math.DG) 2. arXiv:math/0303109 Title: Ricci flow with surgery on three-manifolds Authors: Grisha Perelman Comments: 22 pages Subjects: Differential Geometry (math.DG) 3. arXiv:math/0211159 Title: The entropy formula for the Ricci flow and its geometric applications Authors: Grisha Perelman Comments: 39 pages Subjects: Differential Geometry (math.DG)