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cond-mat/9501005
Renormalization Group results for lattice surface models
We study the phase diagram of statistical systems of closed and open interfaces built on a cubic lattice. Interacting closed interfaces can be written as Ising models, while open surfaces as Z(2) gauge systems. When the open surfaces reduce to closed interfaces with few defects, also the gauge model can be written as a...
1995-01-04
2009-10-28
[ "cond-mat", "hep-th" ]
Emilio N. M. Cirillo, Giuseppe Gonnella
cond-mat/9501006
Rigorous results on a first-order phase transition in antiferromagnetic spin-1/2 coupled chains
Some rigorous results are presented for a first-order quantum phase transition between the dimerized state and Haldane-type state (i.e., a state similar to the ground state of the one-dimensional spin-1 Heisenberg chain) in the spin-1/2 coupled chains with nearest-neighbour and next-nearest-neighbour Heisenberg interac...
1995-01-04
2016-08-31
[ "cond-mat" ]
Y. Xian
cond-mat/9501003
Giant Backscattering Peak in Angle-Resolved Andreev Reflection
It is shown analytically and by numerical simulation that the angular distribution of Andreev reflection by a disordered normal-metal -- superconductor junction has a narrow peak at the angle of incidence. The peak is higher than the well-known coherent backscattering peak in the normal state, by a large factor G/G_0 (...
1995-01-03
2007-05-23
[ "cond-mat" ]
C.W.J. Beenakker, J.A. Melsen, and P.W. Brouwer
cond-mat/9501002
Finite--Size Scaling Analysis of Generalized Mean--Field Theories
We investigate families of generalized mean--field theories that can be formulated using the Peierls--Bogoliubov inequality. For test--Hamiltonians describing mutually non--interacting subsystems of increasing size, the thermodynamics of these mean--field type systems approaches that of the infinite, fully interacting ...
1995-01-03
2016-08-31
[ "cond-mat" ]
Steffen D.~Frischat and Reimer K\"uhn
cond-mat/9501001
Self-Consistent Theory of Normal-to-Superconducting Transition
I study the normal-to-superconducting (NS) transition within the Ginzburg-Landau (GL) model, taking into account the fluctuations in the $m$-component complex order parameter $\psi\a$ and the vector potential $\vec A$ in the arbitrary dimension $d$, for any $m$. I find that the transition is of second-order and that th...
1995-01-03
2009-10-28
[ "cond-mat" ]
Leo Radzihovsky (University of Chicago)
cond-mat/9509073
Paramagnons, weak disorder and positive giant magnetoresistance
At low temperature and for finite spin scattering in a weakly disordered metal, for a certain value, predicted from our theory, of the material-dependent paramagnon interaction, the total conductivity becomes highly sensitive to the orbital effects of a finite magnetic field. As a consequence, positive giant magnetores...
1995-09-13
2008-02-03
[ "cond-mat.dis-nn", "cond-mat.str-el" ]
George Kastrinakis (University of Illinois at Urbana-Champaign)
cond-mat/9510156
Mode-Locking in Quantum-Hall-Effect Point Contacts
We study the effect of an ac drive on the current-voltage (I-V) characteristics of a tunnel junction between two fractional Quantum Hall fluids at filling $\nu ^{-1}$ an odd integer. Within the chiral Luttinger liquid model of edge states, the point contact dynamics is described by a driven damped quantum mechanical pe...
1995-10-27
2009-10-28
[ "cond-mat.mes-hall" ]
Hsiu-Hau Lin (UC Santa Barbara), Matthew P. A. Fisher (UCSB, ITP)
cond-mat/9509037
Microscopic Derivation of Magnetic Flux Density Profiles, Magnetization Hysteresis Loops, and Critical Currents in Strongly Pinned Superconductors
We present a microscopic derivation, without electrodynamical assumptions, of $B(x,y,H(t))$, $M(H(t))$, and $J_c(H(t))$, in agreement with experiments on strongly pinned superconductors, for a range of values of the density and strength of the pinning sites. We numerically solve the overdamped equations of motion % dyn...
1995-09-07
2009-10-28
[ "cond-mat.mtrl-sci", "cond-mat.supr-con", "supr-con" ]
C. Reichhardt, C. J. Olson, J. Groth, Stuart Field, and Franco Nori
cond-mat/9512157
Structure Function of Polymer Nematic Liquid Crystals: A Monte Carlo Simulation
We present a Monte Carlo simulation of a polymer nematic for varying volume fractions, concentrating on the structure function of the sample. We achieve nematic ordering with stiff polymers made of spherical monomers that would otherwise not form a nematic state. Our results are in good qualitative agreement with theor...
1995-12-22
2009-10-28
[ "cond-mat.soft" ]
Randall D. Kamien and Gary S. Grest
cond-mat/9512111
Nature of Driving Force for Protein Folding -- A Result From Analyzing the Statistical Potential
In a statistical approach to protein structure analysis, Miyazawa and Jernigan (MJ) derived a $20\times 20$ matrix of inter-residue contact energies between different types of amino acids. Using the method of eigenvalue decomposition, we find that the MJ matrix can be accurately reconstructed from its first two princip...
1995-12-14
2009-10-28
[ "cond-mat.stat-mech", "physics.bio-ph", "q-bio.BM" ]
Hao Li, Chao Tang, and Ned Wingreen (NEC Research Institute)
cond-mat/9510146
Breakdown of Landau-Ginzburg-Wilson theory for certain quantum phase transitions
The quantum ferromagnetic transition of itinerant electrons is considered. It is shown that the Landau-Ginzburg-Wilson theory described by Hertz and others breaks down due to a singular coupling between fluctuations of the conserved order parameter. This coupling induces an effective long-range interaction between the ...
1995-10-25
2009-10-28
[ "cond-mat.stat-mech" ]
T. Vojta, D. Belitz, R. Narayanan, and T.R. Kirkpatrick
cond-mat/9509063
Ferromagnetism in Hubbard Models
We present the first rigorous examples of non-singular Hubbard models which exhibit ferromagnetism at zero temperature. The models are defined in arbitrary dimensions, and are characterized by finite-ranged hoppings, dispersive bands, and finite on-site Coulomb interaction U. The picture, which goes back to Heisenberg,...
1995-09-12
2009-10-28
[ "cond-mat.stat-mech" ]
Hal Tasaki
cond-mat/9509069
Long-range order versus random-singlet phases in quantum antiferromagnetic systems with quenched disorder
The stability of antiferromagnetic long-range order against quenched disorder is considered. A simple model of an antiferromagnet with a spatially varying Neel temperature is shown to possess a nontrivial fixed point corresponding to long-range order that is stable unless either the order parameter or the spatial dimen...
1995-09-12
2009-10-28
[ "cond-mat.stat-mech" ]
T.R. Kirkpatrick and D. Belitz
cond-mat/9507003
Anderson-Mott transition as a quantum glass problem
We combine a recent mapping of the Anderson-Mott metal-insulator transition on a random-field problem with scaling concepts for random-field magnets to argue that disordered electrons near an Anderson-Mott transition show glass-like behavior. We first discuss attempts to interpret experimental results in terms of a con...
1995-07-03
2009-10-28
[ "cond-mat.stat-mech", "cond-mat.str-el" ]
D. Belitz and T.R. Kirkpatrick
cond-mat/9504021
Quantum ferromagnetic transition in disordered itinerant electron systems
An effective field theory is derived for the ferromagnetic transition of diffusive electrons at T=0. The static disorder which leads to diffusive electron dynamics induces an effective long-range interaction between the spins of the form 1/r^(2d-2). This leads to unusual scaling behavior at the quantum critical point, ...
1995-04-05
2016-08-31
[ "cond-mat.stat-mech", "cond-mat.str-el" ]
D. Belitz and T.R. Kirkpatrick
cond-mat/9501059
Anisotropic Scaling in Layered Aperiodic Ising Systems
The influence of a layered aperiodic modulation of the couplings on the critical behaviour of the two-dimensional Ising model is studied in the case of marginal perturbations. The aperiodicity is found to induce anisotropic scaling. The anisotropy exponent z, given by the sum of the surface magnetization scaling dimens...
1995-01-14
2009-10-28
[ "cond-mat.stat-mech" ]
B. Berche (1), P.E. Berche (1), M. Henkel (2), F. Igloi (3,4), P. Lajko (4), S. Morgan (2), L. Turban (1) ((1) Henri Poincare University, Nancy, (2) Oxford University, (3) Research Institute for Solid State Physics, Budapest, (4) University of Szeged)
cond-mat/9512169
The Hubbard Model: Introduction and Selected Rigorous Results
The Hubbard model is a "highly oversimplified model" for electrons in a solid which interact with each other through extremely short ranged repulsive (Coulomb) interaction. The Hamiltonian of the Hubbard model consists of two pieces; H_hop which describes quantum mechanical hopping of electrons, and Hint which describe...
1995-12-26
2008-02-03
[ "cond-mat.str-el" ]
Hal Tasaki
cond-mat/9508094
Magnetic pair breaking in disordered superconducting films
A theory for the effects of nonmagnetic disorder on the magnetic pair breaking rate $\alpha$ induced by paramagnetic impurities in quasi two-dimensional superconductors is presented. Within the framework of a strong-coupling theory for disordered superconductors, we find that the disorder dependence of $\alpha$ is dete...
1995-08-22
2009-10-28
[ "cond-mat.supr-con", "supr-con" ]
T.P. Devereaux and D. Belitz
cond-mat/9508027
Optical phonons along the c axis of YBa_2Cu_3O_{6+x}, for x=0.5 -> 0.95
The c-axis polarized phonon spectra of single crystals of YBCO_{6+x} have been measured for the doping range x=0.5 -> 0.95, between 10 K and 300 K. The low background electronic conductivity, determined by Kramers-Kronig analysis of the reflectance, leads to a rich phonon structure. With decreased doping the five norma...
1995-08-08
2011-02-07
[ "cond-mat.supr-con", "supr-con" ]
C.C. Homes, T. Timusk, D.A. Bonn, R. Liang and W.N. Hardy
cond-mat/9505012
Magnetic Raman Scattering in Two-Dimensional Spin-1/2 Heisenberg Antiferromagnets: Spectral Shape Anomaly and Magnetostrictive Effects
We calculate the Raman spectrum of the two-dimensional (2D) spin-1/2 Heisenberg antiferromagnet by exact diagonalization and quantum Monte Carlo techniques on clusters of up to 144 sites and, on a 16-site cluster, by considering the phonon-magnon interaction which leads to random fluctuations of the exchange integral. ...
1995-05-03
2016-08-31
[ "cond-mat.supr-con", "cond-mat.mtrl-sci" ]
Franco Nori, Roberto Merlin, Stephan Haas, Anders Sandvik, and Elbio Dagotto (The University of Michigan, Ann Arbor, and National High Magnetic Field Lab, Florida State University)
cs/9512104
Decision-Theoretic Foundations for Causal Reasoning
We present a definition of cause and effect in terms of decision-theoretic primitives and thereby provide a principled foundation for causal reasoning. Our definition departs from the traditional view of causation in that causal assertions may vary with the set of decisions available. We argue that this approach provid...
1995-12-01
2014-11-17
[ "cs.AI" ]
D. Heckerman, R. Shachter
cs/9512105
Translating between Horn Representations and their Characteristic Models
Characteristic models are an alternative, model based, representation for Horn expressions. It has been shown that these two representations are incomparable and each has its advantages over the other. It is therefore natural to ask what is the cost of translating, back and forth, between these representations. Interes...
1995-12-01
2014-11-17
[ "cs.AI" ]
R. Khardon
cs/9512107
Rule-based Machine Learning Methods for Functional Prediction
We describe a machine learning method for predicting the value of a real-valued function, given the values of multiple input variables. The method induces solutions from samples in the form of ordered disjunctive normal form (DNF) decision rules. A central objective of the method and representation is the induction of ...
1995-12-01
2014-11-17
[ "cs.AI" ]
S. M. Weiss, N. Indurkhya
cs/9512102
Vision-Based Road Detection in Automotive Systems: A Real-Time Expectation-Driven Approach
The main aim of this work is the development of a vision-based road detection system fast enough to cope with the difficult real-time constraints imposed by moving vehicle applications. The hardware platform, a special-purpose massively parallel system, has been chosen to minimize system production and operational cost...
1995-12-01
2009-09-25
[ "cs.AI" ]
A. Broggi, S. Berte
cs/9512106
Statistical Feature Combination for the Evaluation of Game Positions
This article describes an application of three well-known statistical methods in the field of game-tree search: using a large number of classified Othello positions, feature weights for evaluation functions with a game-phase-independent meaning are estimated by means of logistic regression, Fisher's linear discriminant...
1995-12-01
2014-11-17
[ "cs.AI" ]
M. Buro
cs/9512101
OPUS: An Efficient Admissible Algorithm for Unordered Search
OPUS is a branch and bound search algorithm that enables efficient admissible search through spaces for which the order of search operator application is not significant. The algorithm's search efficiency is demonstrated with respect to very large machine learning search spaces. The use of admissible search is of poten...
1995-12-01
2014-11-17
[ "cs.AI" ]
G. I. Webb
cs/9512103
Generalization of Clauses under Implication
In the area of inductive learning, generalization is a main operation, and the usual definition of induction is based on logical implication. Recently there has been a rising interest in clausal representation of knowledge in machine learning. Almost all inductive learning systems that perform generalization of clauses...
1995-12-01
2014-11-17
[ "cs.AI" ]
P. Idestam-Almquist
cs/9511101
Flexibly Instructable Agents
This paper presents an approach to learning from situated, interactive tutorial instruction within an ongoing agent. Tutorial instruction is a flexible (and thus powerful) paradigm for teaching tasks because it allows an instructor to communicate whatever types of knowledge an agent might need in whatever situations mi...
1995-11-01
2014-11-17
[ "cs.AI" ]
S. B. Huffman, J. E. Laird
cs/9510101
Diffusion of Context and Credit Information in Markovian Models
This paper studies the problem of ergodicity of transition probability matrices in Markovian models, such as hidden Markov models (HMMs), and how it makes very difficult the task of learning to represent long-term context for sequential data. This phenomenon hurts the forward propagation of long-term context informatio...
1995-10-01
2014-11-17
[ "cs.AI" ]
Y. Bengio, P. Frasconi
cs/9510103
Learning Membership Functions in a Function-Based Object Recognition System
Functionality-based recognition systems recognize objects at the category level by reasoning about how well the objects support the expected function. Such systems naturally associate a ``measure of goodness'' or ``membership value'' with a recognized object. This measure of goodness is the result of combining individu...
1995-10-01
2009-09-25
[ "cs.AI" ]
K. Woods, D. Cook, L. Hall, K. Bowyer, L. Stark
cs/9510102
Improving Connectionist Energy Minimization
Symmetric networks designed for energy minimization such as Boltzman machines and Hopfield nets are frequently investigated for use in optimization, constraint satisfaction and approximation of NP-hard problems. Nevertheless, finding a global solution (i.e., a global minimum for the energy function) is not guaranteed a...
1995-10-01
2014-11-17
[ "cs.AI" ]
G. Pinkas, R. Dechter
cs/9508101
Using Qualitative Hypotheses to Identify Inaccurate Data
Identifying inaccurate data has long been regarded as a significant and difficult problem in AI. In this paper, we present a new method for identifying inaccurate data on the basis of qualitative correlations among related data. First, we introduce the definitions of related data and qualitative correlations among rela...
1995-08-01
2014-11-17
[ "cs.AI" ]
Q. Zhao, T. Nishida
cs/9508102
An Integrated Framework for Learning and Reasoning
Learning and reasoning are both aspects of what is considered to be intelligence. Their studies within AI have been separated historically, learning being the topic of machine learning and neural networks, and reasoning falling under classical (or symbolic) AI. However, learning and reasoning are in many ways interdepe...
1995-08-01
2009-09-25
[ "cs.AI" ]
C. G. Giraud-Carrier, T. R. Martinez
cs/9507101
Building and Refining Abstract Planning Cases by Change of Representation Language
ion is one of the most promising approaches to improve the performance of problem solvers. In several domains abstraction by dropping sentences of a domain description -- as used in most hierarchical planners -- has proven useful. In this paper we present examples which illustrate significant drawbacks of abstraction b...
1995-07-01
2009-09-25
[ "cs.AI" ]
R. Bergmann, W. Wilke
cs/9506101
FLECS: Planning with a Flexible Commitment Strategy
There has been evidence that least-commitment planners can efficiently handle planning problems that involve difficult goal interactions. This evidence has led to the common belief that delayed-commitment is the "best" possible planning strategy. However, we recently found evidence that eager-commitment planners can ha...
1995-06-01
2009-09-25
[ "cs.AI" ]
M. Veloso, P. Stone
cs/9506102
Induction of First-Order Decision Lists: Results on Learning the Past Tense of English Verbs
This paper presents a method for inducing logic programs from examples that learns a new class of concepts called first-order decision lists, defined as ordered lists of clauses each ending in a cut. The method, called FOIDL, is based on FOIL (Quinlan, 1990) but employs intensional background knowledge and avoids the n...
1995-06-01
2008-02-03
[ "cs.AI" ]
R. J. Mooney, M. E. Califf
cs/9505104
Pac-Learning Recursive Logic Programs: Efficient Algorithms
We present algorithms that learn certain classes of function-free recursive logic programs in polynomial time from equivalence queries. In particular, we show that a single k-ary recursive constant-depth determinate clause is learnable. Two-clause programs consisting of one learnable recursive clause and one constant-d...
1995-05-01
2014-11-17
[ "cs.AI" ]
W. W. Cohen
cs/9505105
Pac-learning Recursive Logic Programs: Negative Results
In a companion paper it was shown that the class of constant-depth determinate k-ary recursive clauses is efficiently learnable. In this paper we present negative results showing that any natural generalization of this class is hard to learn in Valiant's model of pac-learnability. In particular, we show that the follow...
1995-05-01
2014-11-17
[ "cs.AI" ]
W. W. Cohen
cs/9505103
Provably Bounded-Optimal Agents
Since its inception, artificial intelligence has relied upon a theoretical foundation centered around perfect rationality as the desired property of intelligent systems. We argue, as others have done, that this foundation is inadequate because it imposes fundamentally unsatisfiable requirements. As a result, there has ...
1995-05-01
2014-11-17
[ "cs.AI" ]
S. J. Russell, D. Subramanian
cs/9505102
Adaptive Load Balancing: A Study in Multi-Agent Learning
We study the process of multi-agent reinforcement learning in the context of load balancing in a distributed system, without use of either central coordination or explicit communication. We first define a precise framework in which to study adaptive load balancing, important features of which are its stochastic nature ...
1995-05-01
2014-11-17
[ "cs.AI" ]
A. Schaerf, Y. Shoham, M. Tennenholtz
cs/9505101
Using Pivot Consistency to Decompose and Solve Functional CSPs
Many studies have been carried out in order to increase the search efficiency of constraint satisfaction problems; among them, some make use of structural properties of the constraint network; others take into account semantic properties of the constraints, generally assuming that all the constraints possess the given ...
1995-05-01
2014-11-17
[ "cs.AI" ]
P. David
cs/9504101
Rerepresenting and Restructuring Domain Theories: A Constructive Induction Approach
Theory revision integrates inductive learning and background knowledge by combining training examples with a coarse domain theory to produce a more accurate theory. There are two challenges that theory revision and other theory-guided systems face. First, a representation language appropriate for the initial theory may...
1995-04-01
2008-02-03
[ "cs.AI" ]
S. K. Donoho, L. A. Rendell
cs/9503101
On the Informativeness of the DNA Promoter Sequences Domain Theory
The DNA promoter sequences domain theory and database have become popular for testing systems that integrate empirical and analytical learning. This note reports a simple change and reinterpretation of the domain theory in terms of M-of-N concepts, involving no learning, that results in an accuracy of 93.4% on the 106 ...
1995-03-01
2014-11-17
[ "cs.AI", "q-bio" ]
J. Ortega
cs/9503102
Cost-Sensitive Classification: Empirical Evaluation of a Hybrid Genetic Decision Tree Induction Algorithm
This paper introduces ICET, a new algorithm for cost-sensitive classification. ICET uses a genetic algorithm to evolve a population of biases for a decision tree induction algorithm. The fitness function of the genetic algorithm is the average cost of classification when using the decision tree, including both the cost...
1995-03-01
2009-09-25
[ "cs.AI" ]
P. D. Turney
cs/9501101
Solving Multiclass Learning Problems via Error-Correcting Output Codes
Multiclass learning problems involve finding a definition for an unknown function f(x) whose range is a discrete set containing k &gt 2 values (i.e., k ``classes''). The definition is acquired by studying collections of training examples of the form [x_i, f (x_i)]. Existing approaches to multiclass learning problems in...
1995-01-01
2014-11-17
[ "cs.AI" ]
T. G. Dietterich, G. Bakiri
cs/9501102
A Domain-Independent Algorithm for Plan Adaptation
The paradigms of transformational planning, case-based planning, and plan debugging all involve a process known as plan adaptation - modifying or repairing an old plan so it solves a new problem. In this paper we provide a domain-independent algorithm for plan adaptation, demonstrate that it is sound, complete, and sys...
1995-01-01
2014-11-17
[ "cs.AI" ]
S. Hanks, D. S. Weld
cs/9501103
Truncating Temporal Differences: On the Efficient Implementation of TD(lambda) for Reinforcement Learning
Temporal difference (TD) methods constitute a class of methods for learning predictions in multi-step prediction problems, parameterized by a recency factor lambda. Currently the most important application of these methods is to temporal credit assignment in reinforcement learning. Well known reinforcement learning alg...
1995-01-01
2008-02-03
[ "cs.AI" ]
P. Cichosz
dg-ga/9512012
Regularisable and minimal orbits for group actions in infinite dimensions
We introduce a class of regularisable infinite dimensional principal fibre bundles which includes fibre bundles arising in gauge field theories like Yang-Mills and string theory and which generalise finite dimensional Riemannian principal fibre bundles induced by an isometric action. We show that the orbits of regulari...
1995-12-22
2008-02-03
[ "dg-ga", "math.DG" ]
M.Arnaudon and S.Paycha (Institut de Recherche de Mathematique Avancee, Universite Louis Pasteur et CNRS, Strasbourg, France)
dg-ga/9512011
$L^2$-Cohomology of Geometrically Infinite Hyperbolic 3-Manifolds
We give results on the following questions about a topologically tame hyperbolic 3-manifold M : 1. Does M have nonzero square-integrable harmonic 1-forms? 2. Does zero lie in the spectrum of the Laplacian acting on (1-forms on M)/Ker(d)?
1995-12-21
2016-08-31
[ "dg-ga", "math.DG" ]
John Lott
dg-ga/9512010
Weierstrass representations for harmonic morphisms on Euclidean spaces and spheres
We construct large families of harmonic morphisms which are holomorphic with respect to Hermitian structures by finding heierarchies of Weierstrass-type representations. This enables us to find new examples of complex-valued harmonic morphisms from Euclidean spaces and spheres.
1995-12-20
2008-02-03
[ "dg-ga", "math.DG" ]
P. Baird (Brest), J.C. Wood (Leeds)
dg-ga/9512009
A closed form for unitons
Unitons, i.e.\ harmonic spheres in a unitary group, correspond to \lq uniton bundles\rq, i.e.\ holomorphic bundles over the compactified tangent space to the complex line with certain triviality and other properties. In this paper, we use a monad representation similar to Donaldson's representation of instanton bundles...
1995-12-19
2008-02-03
[ "dg-ga", "math.DG" ]
Christopher Kumar Anand
dg-ga/9512008
Harmonic morphisms between almost Hermitian manifolds
We obtain conditions on the Lee form under which a holomorphic map between almost Hermitian manifolds is a harmonic map or morphism. Then we discuss under what conditions (i) the image of a holomorphic map from a cosymplectic manifold is also cosymplectic, (ii) a holomophic map with Hermitian image defines a Hermitian ...
1995-12-18
2008-02-03
[ "dg-ga", "math.DG" ]
S. Gudmundsson (Lund) and J.C. Wood (Leeds)
dg-ga/9512007
Exotic deformation quantization
We consider formal deformations of the Poisson algebra of functions (with singularities) on $T^*M$ which are Laurent polynomials of fibers. Tn the case: $\dim M=1$ ($M=S^1, {\bf R}$), there exists a non-trivial $\star$-product on this algebra non-equivalent to the standard Moyal product.
1995-12-14
2008-02-03
[ "dg-ga", "math.DG" ]
V. Ovsienko (CNRS, Luminy--Marseille FRANCE)
dg-ga/9512006
Energy of embedded surfaces invariant under Moebius tranformations, addendum
In a previous preprint we defined an energy associated to every embedding of a surface into $R^n$ or $S^n$. This energy is invariant under Moebius tranformations and the "round" sphere is its only absolute minimum. Here we sketch a proof of the compactness property for a variant of it. The details will appear elsewhere...
1995-12-13
2008-02-03
[ "dg-ga", "math.DG" ]
Stefano Demichelis
dg-ga/9512005
Quotients by complex conjugation for real complete intersection surfaces
Quotients $Y=X/conj$ by the complex conjugation $conj\: X\to X$ for complex surfaces $X$ defined over $\R$ tend to be completely decomposable when they are simply connected, i.e., split into connected sums $\#_n CP^2\#_m\barCP^2$ if $w_2(Y)\ne0$, or into $\#_n(S^2\times S^2)$ if $w_2(Y)=0$. The author proves this prope...
1995-12-11
2008-02-03
[ "dg-ga", "alg-geom", "math.AG", "math.DG" ]
S. Finashin
dg-ga/9512004
The Space of Harmonic Maps from the 2-sphere to the Complex Projective Plane
We study the topology of the space of harmonic maps from $S^2$ to \CP 2$. We prove that the subspaces consisting of maps of a fixed degree and energy are path connected. By a result of Guest and Ohnita it follows that the same is true for the space of harmonic maps to $\CP n$ for $n\geq 2$. We show that the components ...
1995-12-05
2008-02-03
[ "dg-ga", "math.DG" ]
T. Arleigh Crawford (Fields Institute)
dg-ga/9512003
The Spinor Representation of Minimal Surfaces
The spinor representation is developed and used to investigate minimal surfaces in ${\bfR}^3$ with embedded planar ends. The moduli spaces of planar-ended minimal spheres and real projective planes are determined, and new families of minimal tori and Klein bottles are given. These surfaces compactify in $S^3$ to yield ...
1995-12-04
2008-02-03
[ "dg-ga", "math.DG" ]
Rob Kusner (Mathematics, University of Massachusetts at Amherst) and Nick Schmitt (GANG, University of Massachusetts at Amherst)
dg-ga/9511018
Connected sum constructions for constant scalar curvature metrics
We give a general procedure for gluing together possibly noncompact manifolds of constant scalar curvature which satisfy an extra nondegeneracy hypothesis. Our aim is to provide a simple paradigm for making `analytic' connected sums. In particular, we can easily construct complete metrics of constant positive scalar cu...
1995-12-01
2008-02-03
[ "dg-ga", "math.DG" ]
Rafe Mazzeo (Stanford University), Daniel Pollack (University of Chicago) and Karen Uhlenbeck (University of Texas at Austin)
dg-ga/9512002
A Lefschetz formula for flows
For the geodesic flow of an odd dimensional hyperbolic manifold we prove a Lefschetz type formula. The local terms are Fuller indices of the closed orbits. The global "Frobenius operator" is the generator of the flow and its action on tangential cohomology.
1995-12-01
2008-02-03
[ "dg-ga", "math.DG" ]
Anton Deitmar
dg-ga/9512001
On the index of Dirac operators on arithmetic quotients
Using the Arthur-Selberg trace formula we express the index of a Dirac operator on an arithmetic quotient over a totally real field with at least two real embeddings as the integral over the index form plus a sum of orbital integrals. For the Euler operator these orbital integrals are shown to vanish for products of ra...
1995-12-01
2008-02-03
[ "dg-ga", "math.DG" ]
Anton Deitmar
dg-ga/9511017
A remark on positively curved manifolds of dimensions 7 and 13
Totally geodesically embeddings of infinitely many closed 7-manifolds into 13-dimensional positively curved closed Riemannian manifolds are constructed. The problems of computing pinching constants and existence of other totally geodesical embeddings are discussed.
1995-11-30
2008-02-03
[ "dg-ga", "math.DG" ]
I.A. Taimanov
dg-ga/9511016
Periodic orbits in magnetic fields and Ricci curvature of Lagrangian systems
We consider a periodic problem for the motion of a charged particle in a magnetic field. Introducing a notion of Ricci curvature for such Lagrangian systems and using the methods of the calculus of variations in the large, we prove the existence of periodic motions for such particles under a condition of positivity of ...
1995-11-30
2008-02-03
[ "dg-ga", "math.DG" ]
A. Bahri, I.A. Taimanov
dg-ga/9511015
4-Manifolds without Einstein Metrics
It is shown that there are infinitely many compact orientable smooth 4-manifolds which do not admit Einstein metrics, but nevertheless satisfy the strict Hitchin-Thorpe inequality 2 chi > 3 |tau|. The examples in question arise as non-minimal complex algebraic surfaces of general type, and the method of proof stems fro...
1995-11-27
2008-02-03
[ "dg-ga", "alg-geom", "math.AG", "math.DG" ]
Claude LeBrun
dg-ga/9511014
The First Eigenvalue of $P$-manifolds
Antonio Ros gave a lower bound for the first eigenvalue $\lambda_1$ of $\Delta$ of a $P$-manifold $(M, g)$ in terms of the lower bound on the Ricci curvature $Ric_M$ and asked what happened when this lower bound was achieved. In this paper we look in to this question and show that there are strong implications on the g...
1995-11-24
2008-02-03
[ "dg-ga", "math.DG" ]
Akhil Ranjan and G. Santhanam
dg-ga/9511013
Donaldson invariants for some glued manifolds
We prove that every suitable $4$-manifold with $b_1=0$ and with an embedded Riemann surface of genus $2$ is of simple type. We find a relationship between the basic classes of two of these $4$-manifolds and those of the connected sum along the Riemann surface.
1995-11-23
2008-02-03
[ "dg-ga", "math.DG" ]
Vicente Mu\~noz (Oxford University)
dg-ga/9511009
Regularized and $L^2$-Determinants
It is shown that in a tower of coverings the regularized determinant of a generalized Laplacian converges to the $L^2$-determinant. This shows generic nontriviality of analytic torsion or regularized determinants since the $L^2$-counterparts are easier to compute. We further have an "Euler product expansion" for regula...
1995-11-23
2008-02-03
[ "dg-ga", "math.DG" ]
Anton Deitmar
dg-ga/9511010
A Generalisation of Obata's theorem
In a complete Riemannian manifold $(M, g)$ if the hessian of a real valued function satisfies some suitable conditions then it restricts the geometry of $(M, g)$. In this paper we characterize all compact rank-1 symmetric spaces, as those Riemannian manifolds $(M, g)$ admitting a real valued function $u$ such that the ...
1995-11-23
2008-02-03
[ "dg-ga", "math.DG" ]
Akhil Ranjan and G. Santhanam
dg-ga/9511011
$\pi_1$ of symplectic automorphism groups and invertibles in quantum homology rings
We define a homomorphism from (a certain extension of) the fundamental group of the Hamiltonian automorphism group of a symplectic manifold to the group of invertibles in its quantum cohomology ring. The manifold must satify a technical condition similar to weak monotonicity. This revised version has been entirely re...
1995-11-23
2008-02-03
[ "dg-ga", "math.DG" ]
Paul Seidel
dg-ga/9511012
Constraints for Seiberg-Witten basic classes of glued manifolds
We use rudiments of the Seiberg-Witten gluing theory for trivial circle bundles over a Riemann surface to relate de Seiberg-Witten basic classes of two $4$-manifolds containing Riemann surfaces of the same genus and self-intersection zero with those of the $4$-manifold resulting as a connected sum along the surface. We...
1995-11-23
2008-02-03
[ "dg-ga", "math.DG" ]
Vicente Mu\~noz (Oxford University)
dg-ga/9511008
Hamiltonian torus actions on symplectic orbifolds and toric varieties
In the first part of the paper, we build a foundation for further work on Hamiltonian actions on symplectic orbifolds. Most importantly we prove the orbifold versions of the abelian connectedness and convexity theorems. In the second half, we prove that compact symplectic orbifolds with completely integrable torus ac...
1995-11-18
2008-02-03
[ "dg-ga", "math.DG" ]
Eugene Lerman (MIT, presently Univ. of Illinois at Urban-Champaign) and Susan Tolman (MIT)
dg-ga/9511007
Examples of non-Kaehler Hamiltonian torus actions
An important question with a rich history is the extent to which the symplectic category is larger than the Kaehler category. Many interesting examples of non-Kaehler symplectic manifolds have been constructed. However, sufficiently large symmetries can force a symplectic manifold to be Kaehler. In this paper, we solve...
1995-11-16
2008-02-03
[ "dg-ga", "math.DG" ]
Susan Tolman (MIT)
dg-ga/9511006
Geometric zeta-functions of locally symmetric spaces
The theory of geometric zeta functions for locally symmetric spaces as initialized by Selberg and continued by numerous mathematicians is generalized to the case of higher rank spaces. We show analytic continuation, describe the divisor in terms of tangential cohomology and in terms of group cohomology which generalize...
1995-11-10
2008-02-03
[ "dg-ga", "math.DG" ]
Anton Deitmar
dg-ga/9511005
Modified Novikov--Veselov equation and differential geometry of surfaces
Global deformations of surfaces, immersed into the Euclidean 3-space, by using the modified Novikov--Veselov equation are investigated. relation to the theory of the Willmore functional is discussed
1995-11-07
2008-02-03
[ "dg-ga", "math.DG" ]
I.A. Taimanov
dg-ga/9511004
On one family of 13-dimensional closed Riemannian positively curved manifolds
An infinite family of pairwise nonhomeomorphic 13-dimensional positively curved manifolds is constructed
1995-11-07
2008-02-03
[ "dg-ga", "math.DG" ]
Ya.V. Bazaikin
dg-ga/9511003
Complete lifts of harmonic maps and morphisms between Euclidean spaces
We introduce the complete lifts of maps between (real and complex) Euclidean spaces and study their properties concerning holomorphicity, harmonicity and horizontal weakly conformality. As applications, we are able to use this concept to characterize holomorphic maps $\phi:{\Bbb C}^{m}\supset U\longrightarrow {\Bbb C}^...
1995-11-07
2008-02-03
[ "dg-ga", "math.DG" ]
Ye-lin Ou (University of Leeds, U.K.)
dg-ga/9511002
On the classification of quadratic harmonic morphisms between Euclidean spaces
We give a classification of quadratic harmonic morphisms between Euclidean spaces (Theorem 2.4) after proving a Rank Lemma. We also find a correspondence between umbilical (Definition 2.7) quadratic harmonic morphisms and Clifford systems. In the case $ {\Bbb R}^{4}\longrightarrow {\Bbb R}^{3} $, we determine all quadr...
1995-11-03
2008-02-03
[ "dg-ga", "math.DG" ]
Ye-lin Ou (University of Leeds, U.K.), J.C. Wood (University of Leeds, U.K.)
dg-ga/9511001
Quadratic harmonic morphisms and O-systems
We introduce O-systems (Definition \ref{DO}) of orthogonal transformations of ${\Bbb R}^{m}$, and establish $1-1$ correspondences both between equivalence classes of Clifford systems and that of O-systems, and between O-systems and orthogonal multiplications of the form $\mu :{\Bbb R}^{n} \times {\Bbb R}^{m} \longright...
1995-11-03
2008-02-03
[ "dg-ga", "math.DG" ]
Ye-lin Ou (University of Leeds, U.K.)
dg-ga/9510010
Torsions for manifolds with boundary and glueing formulas
We extend the definition of analytic and Reidemeister torsion from closed compact Riemannian manifolds to compact Riemannian manifolds with boundary $(M, \partial M)$, given a flat bundle $\Cal F$ of $\Cal A$-Hilbert modules of finite type and a decomposition of the boundary $\partial M =\partial_- M \cup \partial_+ M$...
1995-10-31
2008-02-03
[ "dg-ga", "math.DG" ]
D.Burghelea (Ohio State University),L.Friedlander (University of Arizona), T.Kappeler (Ohio State University)
dg-ga/9510009
Substantial Riemannian Submersions of S(15) with 7- dimensional fibres
In this paper we show that a substantial Riemannian submersion of S(15) with 7- dimensional fibres is congruent to the standard Hopf fibration. As a consequence we prove a slightly weak form of of the Diameter Rigidity theorem for the Cayley plane which is considerably stronger than the very recent Radius Rigidity Theo...
1995-10-31
2008-02-03
[ "dg-ga", "math.DG" ]
Akhil Ranjan (Dept of Mathematics, I.I.T. Bombay, India)
dg-ga/9510007
Sturm theory, Ghys theorem on zeroes of the Schwarzian derivative and flattening of Legendrian curves
We discuss Ghys' theorem on 4 zeroes of the Schwarzian derivative and its relation with flattening points of Legendrian curves and Sturm theory.
1995-10-26
2008-02-03
[ "dg-ga", "math.DG" ]
V. Ovsienko (CNRS, Luminy--Marseille FRANCE), S. Tabachnikov (University of Arkansas Fayetteville, USA and MPI Bonn, Germany)
dg-ga/9510008
Theorem on six vertices of a plane curve via the Sturm theory
We discuss the theorem on the existence of six points on a convex closed plane curve in which the curve has a contact of order six with the osculating conic. (This is the ``projective version'' of the well known four vertices theorem for a curve in the Euclidean plane.) We obtain this classical fact as a corollary of s...
1995-10-26
2016-08-31
[ "dg-ga", "math.DG" ]
L. Guieu, E. Mourre, V.Yu. Ovsienko (CNRS, Luminy -- Marseille, FRANCE)
dg-ga/9510006
Group systems, groupoids, and moduli spaces of parabolic bundles
Let $G$ be a Lie group, with an invariant non-degenerate symmetric bilinear form on its Lie algebra, let $\pi$ be the fundamental group of an orientable (real) surface $M$ with a finite number of punctures, and let $\bold C$ be a family of conjugacy classes in $G$, one for each puncture. A finite-dimensional constructi...
1995-10-23
2008-02-03
[ "dg-ga", "math.DG", "math.SG" ]
K. Guruprasad, J. Huebschmann, L. Jeffrey, and A. Weinstein
dg-ga/9510005
The Geometric Phase in the Three-Body Problem
Suppose that the initial triangle formed by the three moving masses of the three-body problem is similar to the triangle formed at some later time. We derive a simple integral formula for the overall rotation relating the two triangles. The formula is based on the fact that the space of similarity classes of triangles ...
1995-10-16
2016-08-31
[ "dg-ga", "math.DG" ]
Richard Montgomery (Mathematics Dept, Univ. of Calif., Santa Cruz)
dg-ga/9510004
Periodic Hamiltonian flows on four dimensional manifolds
We classify the periodic Hamiltonian flows on compact four dimensional symplectic manifolds up to isomorphism of Hamiltonian S^1 spaces. Additionally, we show that all these spaces are Kaehler, that every such space is obtained from a simple model by a sequence of symplectic blowups, and that if the fixed points are is...
1995-10-13
2008-02-03
[ "dg-ga", "math.DG" ]
Yael Karshon
dg-ga/9510002
Compact null hypersurfaces and collapsing Riemannian manifolds
Restrictions are obtained on the topology of a compact divergence-free null hypersurface in a four-dimensional Lorentzian manifold whose Ricci tensor is zero or satisfies some weaker conditions. This is done by showing that each null hypersurface of this type can be used to construct a family of three-dimensional Riema...
1995-10-06
2008-02-03
[ "dg-ga", "gr-qc", "math.DG" ]
Alan D. Rendall
dg-ga/9510003
On the space of harmonic $2$-spheres in ${\bf C}P^2$
Carrying further work of T.A. Crawford, we show that each component of the space of harmonic maps from the $2$-sphere to complex projective $2$-space of degree $d$ and energy $4 \pi E$ is a smooth closed submanifold of the space of all $C^j$ maps $(j \geq 2)$. We achieve this by showing that the Gauss transform which r...
1995-10-06
2008-02-03
[ "dg-ga", "math.DG" ]
L. Lemaire (Univ. Libre Bruxelles), J.C. Wood (Univ. Leeds, G.B)
dg-ga/9510001
The Marked Length Spectrum vs. The Laplace Spectrum on Forms on Riemannian Nilmanifolds
The subject of this paper is the relationship among the marked length spectrum, the length spectrum, the Laplace spectrum on functions, and the Laplace spectrum on forms on Riemannian nilmanifolds. In particular, we show that for a large class of three-step nilmanifolds, if a pair of nilmanifolds in this class has the ...
1995-10-05
2008-02-03
[ "dg-ga", "math.DG" ]
Ruth Gornet (Texas Tech Univ; Lubbock, TX)
dg-ga/9509005
Notes on Seiberg-Witten Gauge Theory
These notes provide an introductory exposition of the Seiberg-Witten gauge theory. They collect the material presented in a series of seminars given by the author at the University of Milano.
1995-09-20
2008-02-03
[ "dg-ga", "hep-th", "math.DG" ]
M. Marcolli
dg-ga/9509004
On a class of K\"ahler manifolds whose geodesic flows are integrable
We study $n$-dimensional K\"ahler manifolds whose geodesic flows possess $n$ first integrals in involution that are fibrewise hermitian forms and simultaneously normalizable. Under some mild assumption, one can associate with such a manifold an $n$-dimensional commutative Lie algebra of infinitesimal automorphisms. Thi...
1995-09-20
2008-02-03
[ "dg-ga", "math.DG" ]
Kazuyoshi Kiyohara
dg-ga/9509003
Harmonic Maps with Prescribed Singularities on Unbounded Domains
The Einstein/Abelian-Yang-Mills Equations reduce in the stationary and axially symmetric case to a harmonic map with prescribed singularities $\p\colon\R^3\sm\Sigma\to\H^{k+1}_\C$ into the $(k+1)$-dimensional complex hyperbolic space. In this paper, we prove the existence and uniqueness of harmonic maps with prescribed...
1995-09-19
2014-11-17
[ "dg-ga", "gr-qc", "math.DG" ]
Gilbert Weinstein (University of Alabama at Birmingham)
dg-ga/9509002
On the Geometry of Complex Grassmann Manifold, Its Noncompact Dual and Coherent States
Different topics on the differential geometry of the complex Grassmann manifold are surveyed in relation to the coherent states. A calculation of the tangent conjugate locus and conjugate locus in the complex Grassmann manifold is presented. The proofs use the Jordan's stationary angles. Also various formulas for the d...
1995-09-08
2008-02-03
[ "dg-ga", "math.DG" ]
Stefan Berceanu
dg-ga/9509001
Affine connections on involutive G-structures
This paper is a review of the twistor theory of irreducible G-structures and affine connections. Long ago, Berger presented a very restricted list of possible irreducibly acting holonomies of torsion-free affine connections. His list was complete in the part of metric connections, while the situation with holonomies of...
1995-09-06
2008-02-03
[ "dg-ga", "math.DG" ]
Sergey A. Merkulov
dg-ga/9508014
On the Incompleteness of Berger's List of Holonomy Representations
In 1955, Berger \cite{Ber} gave a list of irreducible reductive representations which can occur as the holonomy of a torsion-free affine connection. This list was stated to be complete up to possibly a finite number of missing entries. In this paper, we show that there is, in fact, an infinite family of representations...
1995-08-30
2015-06-25
[ "dg-ga", "math.DG" ]
Quo-Shin Chi, Sergey A. Merkulov, Lorenz J. Schwachh\"ofer
dg-ga/9508013
Manin Triples for Lie Bialgebroids
In his study of Dirac structures, a notion which includes both Poisson structures and closed 2-forms, T. Courant introduced a bracket on the direct sum of vector fields and 1-forms. This bracket does not satisfy the Jacobi identity except on certain subspaces. In this paper we systematize the properties of this bracket...
1995-08-28
2008-02-03
[ "dg-ga", "math.DG", "math.SG" ]
Zhang-Ju Liu, Alan Weinstein, and Ping Xu
dg-ga/9508011
Uniton Bundles
We show that a twistor construction of Hitchin and Ward can be adapted to study unitons (harmonic spheres in a unitary group). Specifically, we show that unitons are equivalent to holomorphic bundles with extra structure over a rational ruled surface with energy given by Chern class. This equivalence allows us to confi...
1995-08-23
2008-02-03
[ "dg-ga", "math.DG" ]
Christopher Kumar Anand
dg-ga/9508012
Controlled Geometry via Smoothing
We prove that Riemannian metrics with a uniform weak norm can be smoothed to having arbitrarily high regularity. This generalizes all previous smoothing results. As a consequence we obtain a generalization of Gromov's almost flat manifold theorem. A uniform Betti number estimate is also obtained.
1995-08-23
2008-02-03
[ "dg-ga", "math.DG" ]
Peter Petersen, Guofang Wei and Rugang Ye
dg-ga/9508010
Stiefel-Whitney Classes and the Conormal Cycle of a Singular Variety
A geometric construction of Sullivan's Stiefel-Whitney homology classes of a real analytic variety $X$ is given by means of the conormal cycle of an embedding of $X$ in a smooth variety. We prove that the Stiefel-Whitney classes define additive natural transformations from certain constructible functions to homology. W...
1995-08-21
2008-02-03
[ "dg-ga", "math.DG" ]
Joseph H. G. Fu and Clint McCrory
dg-ga/9508009
The Novikov-Bott inequalities
We generalize the Novikov inequalities for 1-forms in two different directions: first, we allow non-isolated critical points (assuming that they are non-degenerate in the sense of R.Bott), and, secondly, we strengthen the inequalities by means of twisting by an arbitrary flat bundle. We also obtain an $L^2$ version of ...
1995-08-16
2016-08-31
[ "dg-ga", "math.DG" ]
Maxim Braverman and Michael Farber
dg-ga/9508008
Equivalence of Geometric and Combinatorial Dehn Functions
In this paper it is proved that if a finitely presented group acts properly discontinuously, cocompactly and by isometries on a simply connected Riemannian manifold, then the two Dehn functions, of the group and the manifold, respectively, are equivalent.
1995-08-15
2008-02-03
[ "dg-ga", "math.DG" ]
Jose Burillo (University of Utah)
dg-ga/9508007
Rank one symmetric spaces and Rigidity
In this paper we show that if the limit set is not small ,marked length spectrum determines geometric structure of rank one locally symmetric manifolds.
1995-08-14
2008-02-03
[ "dg-ga", "math.DG" ]
Inkang Kim