Results for "Christopher D. Manning"

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Deep Biaffine Attention for Neural Dependency ParsingNov 06 2016While deep learning parsing approaches have proven very successful at finding the structure of sentences, most neural dependency parsers use neural networks only for feature extraction, and then use those features in traditional parsing algorithms. In ... More
Deep Biaffine Attention for Neural Dependency ParsingNov 06 2016Nov 22 2016While deep learning parsing approaches have proven very successful at finding the structure of sentences, most neural dependency parsers use neural networks only for feature extraction, and then use those features in traditional parsing algorithms. In ... More
Simpler but More Accurate Semantic Dependency ParsingJul 03 2018While syntactic dependency annotations concentrate on the surface or functional structure of a sentence, semantic dependency annotations aim to capture between-word relationships that are more closely related to the meaning of a sentence, using graph-structured ... More
Improving Coreference Resolution by Learning Entity-Level Distributed RepresentationsJun 04 2016Jun 08 2016A long-standing challenge in coreference resolution has been the incorporation of entity-level information - features defined over clusters of mentions instead of mention pairs. We present a neural network based coreference system that produces high-dimensional ... More
Deep Reinforcement Learning for Mention-Ranking Coreference ModelsSep 27 2016Oct 31 2016Coreference resolution systems are typically trained with heuristic loss functions that require careful tuning. In this paper we instead apply reinforcement learning to directly optimize a neural mention-ranking model for coreference evaluation metrics. ... More
Deep Reinforcement Learning for Mention-Ranking Coreference ModelsSep 27 2016Coreference resolution systems are typically trained with heuristic loss functions that require careful tuning. In this paper we instead apply reinforcement learning to directly optimize a neural mention-ranking model for coreference evaluation metrics. ... More
A Copy-Augmented Sequence-to-Sequence Architecture Gives Good Performance on Task-Oriented DialogueJan 15 2017Aug 14 2017Task-oriented dialogue focuses on conversational agents that participate in user-initiated dialogues on domain-specific topics. In contrast to chatbots, which simply seek to sustain open-ended meaningful discourse, existing task-oriented agents usually ... More
Probabilistic Parsing Using Left Corner Language ModelsNov 17 1997We introduce a novel parser based on a probabilistic version of a left-corner parser. The left-corner strategy is attractive because rule probabilities can be conditioned on both top-down goals and bottom-up derivations. We develop the underlying theory ... More
Key-Value Retrieval Networks for Task-Oriented DialogueMay 15 2017Jul 14 2017Neural task-oriented dialogue systems often struggle to smoothly interface with a knowledge base. In this work, we seek to address this problem by proposing a new neural dialogue agent that is able to effectively sustain grounded, multi-domain discourse ... More
Arc-swift: A Novel Transition System for Dependency ParsingMay 12 2017Transition-based dependency parsers often need sequences of local shift and reduce operations to produce certain attachments. Correct individual decisions hence require global information about the sentence context and mistakes cause error propagation. ... More
Achieving Open Vocabulary Neural Machine Translation with Hybrid Word-Character ModelsApr 04 2016Jun 23 2016Nearly all previous work on neural machine translation (NMT) has used quite restricted vocabularies, perhaps with a subsequent method to patch in unknown words. This paper presents a novel word-character solution to achieving open vocabulary NMT. We build ... More
Graph Convolution over Pruned Dependency Trees Improves Relation ExtractionSep 26 2018Dependency trees help relation extraction models capture long-range relations between words. However, existing dependency-based models either neglect crucial information (e.g., negation) by pruning the dependency trees too aggressively, or are computationally ... More
Learning by Abstraction: The Neural State MachineJul 09 2019We introduce the Neural State Machine, seeking to bridge the gap between the neural and symbolic views of AI and integrate their complementary strengths for the task of visual reasoning. Given an image, we first predict a probabilistic graph that represents ... More
CoQA: A Conversational Question Answering ChallengeAug 21 2018Mar 29 2019Humans gather information by engaging in conversations involving a series of interconnected questions and answers. For machines to assist in information gathering, it is therefore essential to enable them to answer conversational questions. We introduce ... More
CoQA: A Conversational Question Answering ChallengeAug 21 2018Humans gather information by engaging in conversations involving a series of interconnected questions and answers. For machines to assist in information gathering, it is therefore essential to enable them to answer conversational questions. We introduce ... More
GQA: A New Dataset for Real-World Visual Reasoning and Compositional Question AnsweringFeb 25 2019May 10 2019We introduce GQA, a new dataset for real-world visual reasoning and compositional question answering, seeking to address key shortcomings of previous VQA datasets. We have developed a strong and robust question engine that leverages scene graph structures ... More
Learning by Abstraction: The Neural State MachineJul 09 2019Jul 11 2019We introduce the Neural State Machine, seeking to bridge the gap between the neural and symbolic views of AI and integrate their complementary strengths for the task of visual reasoning. Given an image, we first predict a probabilistic graph that represents ... More
A Thorough Examination of the CNN/Daily Mail Reading Comprehension TaskJun 09 2016Aug 08 2016Enabling a computer to understand a document so that it can answer comprehension questions is a central, yet unsolved goal of NLP. A key factor impeding its solution by machine learned systems is the limited availability of human-annotated data. Hermann ... More
Learning by Abstraction: The Neural State MachineJul 09 2019Jul 15 2019We introduce the Neural State Machine, seeking to bridge the gap between the neural and symbolic views of AI and integrate their complementary strengths for the task of visual reasoning. Given an image, we first predict a probabilistic graph that represents ... More
GQA: a new dataset for compositional question answering over real-world imagesFeb 25 2019We introduce GQA, a new dataset for real-world visual reasoning and compositional question answering, seeking to address key shortcomings of previous VQA datasets. We have developed a strong and robust question engine that leverages scene graph structures ... More
Sentences with Gapping: Parsing and Reconstructing Elided PredicatesApr 18 2018Sentences with gapping, such as Paul likes coffee and Mary tea, lack an overt predicate to indicate the relation between two or more arguments. Surface syntax representations of such sentences are often produced poorly by parsers, and even if correct, ... More
GQA: A New Dataset for Real-World Visual Reasoning and Compositional Question AnsweringFeb 25 2019Apr 10 2019We introduce GQA, a new dataset for real-world visual reasoning and compositional question answering, seeking to address key shortcomings of previous VQA datasets. We have developed a strong and robust question engine that leverages scene graph structures ... More
Compositional Attention Networks for Machine ReasoningMar 08 2018Apr 24 2018We present the MAC network, a novel fully differentiable neural network architecture, designed to facilitate explicit and expressive reasoning. MAC moves away from monolithic black-box neural architectures towards a design that encourages both transparency ... More
Learning Distributed Word Representations for Natural Logic ReasoningOct 15 2014Natural logic offers a powerful relational conception of meaning that is a natural counterpart to distributed semantic representations, which have proven valuable in a wide range of sophisticated language tasks. However, it remains an open question whether ... More
Tree-structured composition in neural networks without tree-structured architecturesJun 16 2015Nov 09 2015Tree-structured neural networks encode a particular tree geometry for a sentence in the network design. However, these models have at best only slightly outperformed simpler sequence-based models. We hypothesize that neural sequence models like LSTMs ... More
Recursive Neural Networks Can Learn Logical SemanticsJun 06 2014May 14 2015Tree-structured recursive neural networks (TreeRNNs) for sentence meaning have been successful for many applications, but it remains an open question whether the fixed-length representations that they learn can support tasks as demanding as logical deduction. ... More
A large annotated corpus for learning natural language inferenceAug 21 2015Understanding entailment and contradiction is fundamental to understanding natural language, and inference about entailment and contradiction is a valuable testing ground for the development of semantic representations. However, machine learning research ... More
Improved Semantic Representations From Tree-Structured Long Short-Term Memory NetworksFeb 28 2015May 30 2015Because of their superior ability to preserve sequence information over time, Long Short-Term Memory (LSTM) networks, a type of recurrent neural network with a more complex computational unit, have obtained strong results on a variety of sequence modeling ... More
SceneSeer: 3D Scene Design with Natural LanguageFeb 28 2017Designing 3D scenes is currently a creative task that requires significant expertise and effort in using complex 3D design interfaces. This effortful design process starts in stark contrast to the easiness with which people can use language to describe ... More
Universal Dependency Parsing from ScratchJan 29 2019This paper describes Stanford's system at the CoNLL 2018 UD Shared Task. We introduce a complete neural pipeline system that takes raw text as input, and performs all tasks required by the shared task, ranging from tokenization and sentence segmentation, ... More
Relaxations for inference in restricted Boltzmann machinesDec 21 2013Jan 02 2014We propose a relaxation-based approximate inference algorithm that samples near-MAP configurations of a binary pairwise Markov random field. We experiment on MAP inference tasks in several restricted Boltzmann machines. We also use our underlying sampler ... More
Effective Approaches to Attention-based Neural Machine TranslationAug 17 2015Sep 20 2015An attentional mechanism has lately been used to improve neural machine translation (NMT) by selectively focusing on parts of the source sentence during translation. However, there has been little work exploring useful architectures for attention-based ... More
Learning New Facts From Knowledge Bases With Neural Tensor Networks and Semantic Word VectorsJan 16 2013Mar 16 2013Knowledge bases provide applications with the benefit of easily accessible, systematic relational knowledge but often suffer in practice from their incompleteness and lack of knowledge of new entities and relations. Much work has focused on building or ... More
Compression of Neural Machine Translation Models via PruningJun 29 2016Neural Machine Translation (NMT), like many other deep learning domains, typically suffers from over-parameterization, resulting in large storage sizes. This paper examines three simple magnitude-based pruning schemes to compress NMT models, namely class-blind, ... More
Learning Language Games through InteractionJun 08 2016We introduce a new language learning setting relevant to building adaptive natural language interfaces. It is inspired by Wittgenstein's language games: a human wishes to accomplish some task (e.g., achieving a certain configuration of blocks), but can ... More
What Does BERT Look At? An Analysis of BERT's AttentionJun 11 2019Large pre-trained neural networks such as BERT have had great recent success in NLP, motivating a growing body of research investigating what aspects of language they are able to learn from unlabeled data. Most recent analysis has focused on model outputs ... More
Text to 3D Scene Generation with Rich Lexical GroundingMay 23 2015Jun 05 2015The ability to map descriptions of scenes to 3D geometric representations has many applications in areas such as art, education, and robotics. However, prior work on the text to 3D scene generation task has used manually specified object categories and ... More
A Fast Unified Model for Parsing and Sentence UnderstandingMar 19 2016Jul 29 2016Tree-structured neural networks exploit valuable syntactic parse information as they interpret the meanings of sentences. However, they suffer from two key technical problems that make them slow and unwieldy for large-scale NLP tasks: they usually operate ... More
Semi-Supervised Sequence Modeling with Cross-View TrainingSep 22 2018Unsupervised representation learning algorithms such as word2vec and ELMo improve the accuracy of many supervised NLP models, mainly because they can take advantage of large amounts of unlabeled text. However, the supervised models only learn from task-specific ... More
Textual Analogy Parsing: What's Shared and What's Compared among Analogous FactsSep 07 2018To understand a sentence like "whereas only 10% of White Americans live at or below the poverty line, 28% of African Americans do" it is important not only to identify individual facts, e.g., poverty rates of distinct demographic groups, but also the ... More
BAM! Born-Again Multi-Task Networks for Natural Language UnderstandingJul 10 2019It can be challenging to train multi-task neural networks that outperform or even match their single-task counterparts. To help address this, we propose using knowledge distillation where single-task models teach a multi-task model. We enhance this training ... More
Zero-Shot Learning Through Cross-Modal TransferJan 16 2013Mar 20 2013This work introduces a model that can recognize objects in images even if no training data is available for the objects. The only necessary knowledge about the unseen categories comes from unsupervised large text corpora. In our zero-shot framework distributional ... More
HotpotQA: A Dataset for Diverse, Explainable Multi-hop Question AnsweringSep 25 2018Existing question answering (QA) datasets fail to train QA systems to perform complex reasoning and provide explanations for answers. We introduce HotpotQA, a new dataset with 113k Wikipedia-based question-answer pairs with four key features: (1) the ... More
Learning to Summarize Radiology FindingsSep 12 2018Oct 08 2018The Impression section of a radiology report summarizes crucial radiology findings in natural language and plays a central role in communicating these findings to physicians. However, the process of generating impressions by summarizing findings is time-consuming ... More
Evaluating the word-expert approach for Named-Entity DisambiguationMar 15 2016Named Entity Disambiguation (NED) is the task of linking a named-entity mention to an instance in a knowledge-base, typically Wikipedia. This task is closely related to word-sense disambiguation (WSD), where the supervised word-expert approach has prevailed. ... More
Virtual Geometricity is RareJul 29 2014Apr 20 2015We present the results of computer experiments suggesting that the probability that a random multiword in a free group is virtually geometric decays to zero exponentially quickly in the length of the multiword. We then prove this fact.
Robust Subgraph Generation Improves Abstract Meaning Representation ParsingJun 10 2015The Abstract Meaning Representation (AMR) is a representation for open-domain rich semantics, with potential use in fields like event extraction and machine translation. Node generation, typically done using a simple dictionary lookup, is currently an ... More
Naturalizing a Programming Language via Interactive LearningApr 23 2017Our goal is to create a convenient natural language interface for performing well-specified but complex actions such as analyzing data, manipulating text, and querying databases. However, existing natural language interfaces for such tasks are quite primitive ... More
A Solvable Two-Charge Ensemble on the CircleApr 21 2014Apr 23 2014We introduce an ensemble consisting of logarithmically repelling charge one and charge two particles on the unit circle constrained so that the total charge of all particles equals $N$, but the proportion of each species of particle is allowed to vary ... More
Fermions in Rotating Reference FramesDec 02 2015Feb 24 2016Current quantisations of fermions in cylindrical coordinates are shown to be inadequate in calculating some single-particle expectation values. This paper develops an alternate quantisation, applicable to one-particle states, which is generalised to rotating ... More
Patching and Multiplicity $2^k$ for Shimura CurvesFeb 19 2019We use the Taylor--Wiles--Kisin patching method to investigate the multiplicities with which Galois representations occur in the mod $\ell$ cohomology of Shimura curves over totally real number fields. Our method relies on explicit computations of local ... More
Algorithmic detection and description of hyperbolic structures on closed 3-manifolds with solvable word problemFeb 19 2001Jan 23 2002We outline a rigorous algorithm, first suggested by Casson, for determining whether a closed orientable 3-manifold M is hyperbolic, and to compute the hyperbolic structure, if one exists. The algorithm requires that a procedure has been given to solve ... More
Tissue flow induces cell shape changes during organogenesisApr 06 2018Jul 19 2018In embryonic development, programmed cell shape changes are essential for building functional organs, but in many cases the mechanisms that precisely regulate these changes remain unknown. We propose that fluid-like drag forces generated by the motion ... More
Photon collection from a trapped ion--cavity systemDec 19 2011We present the design and implementation of a trapped ion cavity QED system. A single ytterbium ion is confined by a micron-scale ion trap inside a 2 mm optical cavity. The ion is coherently pumped by near resonant laser light while the cavity output ... More
Protostellar outflow-driven turbulenceJan 01 2007Protostellar outflows crisscross the regions of star cluster formation, stirring turbulence and altering the evolution of the forming cluster. We model the stirring of turbulent motions by protostellar outflows, building on an observation that the scaling ... More
Feedback from Protostellar Outflows in Star and Star Cluster FormationJul 13 2000Magnetic stresses collimate protostellar winds into a common distribution of force with angle. Sweeping into the ambient medium, such winds drive bipolar molecular outflows whose properties are insensitive to the distribution of ambient gas and to the ... More
Localized $L^p$-estimates for eigenfunctions: IIOct 21 2016If $(M,g)$ is a compact Riemannian manifold of dimension $n\ge 2$ we give necessary and sufficient conditions for improved $L^p(M)$-norms of eigenfunctions for all $2<p\ne p_c=\tfrac{2(n+1)}{n-1}$, the critical exponent. Since improved $L^{p_c}(M)$ bounds ... More
Remarks on formal languages and the model theory of monoidsMar 20 2018Given a monoid $(M,\cdot ,\epsilon )$ that is freely generated on a finite set $\Sigma $, it is shown that the quantifier-free definable subsets of $M$ form a proper subclass of the star-free languages over $\Sigma $. Furthermore, a subset $A\subseteq ... More
The range of multiplicative functions on C[x], R[x] and Z[x]Sep 25 2005Jul 13 2007Mahler's measure is generalized to create the class of {\it multiplicative distance functions}. These functions measure the complexity of polynomials based on the location of their zeros in the complex plane. Following work of S.-J. Chern and J. Vaaler ... More
Improved critical eigenfunction estimates on manifolds of nonpositive curvatureDec 11 2015We prove new improved endpoint, $L^{p_c}$, $p_c=\tfrac{2(n+1)}{n-1}$, estimates (the "kink point") for eigenfunctions on manifolds of nonpositive curvature. We do this by using energy and dispersive estimates for the wave equation as well as new improved ... More
Unitarity and microscopic acausality in a nonlocal theoryMay 06 2016May 13 2016We consider unitarity and causality in a higher-derivative theory of infinite order, where propagators fall off more quickly in the ultraviolet due to the presence of a transcendental entire function of the momentum. Like Lee-Wick theories, these field ... More
Stepping Stones to Inductive Synthesis of Low-Level Looping ProgramsNov 26 2018Inductive program synthesis, from input/output examples, can provide an opportunity to automatically create programs from scratch without presupposing the algorithmic form of the solution. For induction of general programs with loops (as opposed to loop-free ... More
Unweighted Stochastic Local Search can be Effective for Random CSP BenchmarksNov 27 2014We present ULSA, a novel stochastic local search algorithm for random binary constraint satisfaction problems (CSP). ULSA is many times faster than the prior state of the art on a widely-studied suite of random CSP benchmarks. Unlike the best previous ... More
A boundary-integral approach for the Poisson-Boltzmann equation with polarizable force fieldsOct 02 2018Implicit-solvent models are widely used to study the electrostatics in dissolved biomolecules, which are parameterized using force fields. Standard force fields treat the charge distribution with point charges, however, other force fields have emerged ... More
Estimates for the Dirichlet-wave equation and applications to nonlinear wave equationsNov 10 2003In this article we shall go over recent work in proving dispersive and Strichartz estimates for the Dirichlet-wave equation. We shall discuss applications to existence questions outside of obstacles and discuss open problems.
Bipolar molecular outflows driven by hydromagnetic protostellar windsSep 29 1999We demonstrate that magnetically-collimated protostellar winds will sweep ambient material into thin, radiative, momentum-conserving shells whose features reproduce those commonly observed in bipolar molecular outflows. We find the typical position-velocity ... More
Singularities of pluri-theta divisors in Char $p>0$Dec 09 2011We show that if $(X,\Theta)$ is a PPAV over an algebraically closed field of characteristic $p>0$ and $D\in |m\Theta|$, then $(X,\frac 1 m D)$ is a limit of strongly $F$-regular pairs and in particular ${\rm mult}_x(D)\leq m\cdot \dim X$ for any $x\in ... More
Averages over Ginibre's Ensemble of Random Real MatricesMay 02 2006We give a method for computing the ensemble average of multiplicative class functions over the Gaussian ensemble of real asymmetric matrices. These averages are expressed in terms of the Pfaffian of Gram-like antisymmetric matrices formed with respect ... More
Kakeya-Nikodym averages and $L^p$-norms of eigenfunctionsJul 28 2009Jun 14 2010We provide a necessary and sufficient condition that $L^p$-norms, $2<p<6$, of eigenfunctions of the square root of minus the Laplacian on 2-dimensional compact boundaryless Riemannian manifolds $M$ are small compared to a natural power of the eigenvalue ... More
The Partition Function of Multicomponent Log-GasesDec 31 2011We give an expression for the partition function of a one-dimensional log-gas comprised of particles of (possibly) different integer charge at inverse temperature {\beta} = 1 (restricted to the line in the presence of a neutralizing field) in terms of ... More
A derived category approach to generic vanishingAug 20 2003We prove a Generic Vanishing Theorem for coherent sheaves on an abelian variety over an algebraically closed field $k$. When $k=\CC$ this implies a conjecture of Green and Lazarsfeld.
Supernova Hosts for Gamma-Ray Burst Jets: Dynamical ConstraintsMar 06 2002Jul 06 2003I constrain a possible supernova origin for gamma-ray bursts by modeling the dynamical interaction between a relativistic jet and a stellar envelope surrounding it. The delay in observer's time introduced by the jet traversing the envelope should not ... More
A modified ziggurat algorithm for generating exponentially- and normally-distributed pseudorandom numbersMar 26 2014Apr 21 2014The Ziggurat Algorithm is a very fast rejection sampling method for generating PseudoRandom Numbers (PRNs) from common statistical distributions. The algorithm divides a distribution into rectangular layers that stack on top of each other (resembling ... More
The distribution of Mahler's measures of reciprocal polynomialsNov 15 2003We study the distribution of Mahler's measures of reciprocal polynomials with complex coefficients and bounded even degree. We discover that the distribution function associated to Mahler's measure restricted to monic reciprocal polynomials is a reciprocal ... More
Problems related to the concentration of eigenfunctionsOct 26 2015We survey recent results related to the concentration of eigenfunctions. We also prove some new results concerning ball-concentration, as well as showing that eigenfunctions saturating lower bounds for $L^1$-norms must also, in a measure theoretical sense, ... More
Global existence for nonlinear wave equations with multiple speedsFeb 04 2002Oct 10 2002We shall be concerned with the Cauchy problem for quasilinear systems in three space dimensions of the form \label{i.1} \partial^2_tu^I-c^2_I\Delta u^I = C^{IJK}_{abc}\partial_c u^J\partial_a\partial_b u^K + B^{IJK}_{ab}\partial_a u^J\partial_b u^K, \quad ... More
Hall Algebras as Hopf ObjectsNov 24 2010One problematic feature of Hall algebras is the fact that the standard multiplication and comultiplication maps do not satisfy the bialgebra compatibility condition in the underlying symmetric monoidal category Vect. In the past this problem has been ... More
On the Role of Massive Stars in the Support and Destruction of Giant Molecular CloudsOct 11 2001Feb 01 2002We argue that massive stars are the dominant sources of energy for the turbulent motions within giant molecular clouds, and that the primary agent of feedback is the expansion of H II regions within the cloud volume. This conclusion is suggested by the ... More
On log canonical inversion of adjunctionFeb 02 2012We prove a result on the inversion of adjunction for log canonical pairs that generalizes Kawakita's result to log canonical centers of arbitrary codimension.
Correlation Functions for β=1 Ensembles of Matrices of Odd SizeNov 08 2008Using the method of Tracy and Widom we rederive the correlation functions for \beta=1 Hermitian and real asymmetric ensembles of N x N matrices with N odd.
Localized $L^p$-estimates of eigenfunctions: A note on an article of Hezari and RivièreMar 25 2015Mar 27 2015We use a straightforward variation on a recent argument of Hezari and Rivi\`ere~\cite{HR} to obtain localized $L^p$-estimates for all exponents larger than or equal to the critical exponent $p_c=\tfrac{2(n+1)}{n-1}$. We are able to this directly by just ... More
Ensemble Averages when βis a Square IntegerAug 25 2010We give a hyperpfaffian formulation of partition functions and ensemble averages for Hermitian and circular ensembles when L is an arbitrary integer and \beta=L^2 and when L is an odd integer and \beta=L^2 +1.
Concerning Nikodym-type sets in 3-dimensional curved spacesDec 26 1999We obtain estimates for maximal functions that arise when one studies Nikodym-type sets. We also formulate a curvature condition that allows favorable estimates for these maximal functions.
Eigenfunction and Bochner Riesz estimates on manifolds with boundaryFeb 04 2002Mar 06 2002The purpose of this paper is to give a simple proof of sharp $L^\infty$ estimates for the eigenfunctions of the Dirichlet Laplacian on smooth compact Riemannian manifolds $(M,g)$ of dimension $n\ge 2$ with boundary $\partial M$ and then to use these estimates ... More
Remarks on recognizable subsets and local rankMar 20 2018Jun 07 2019Given a monoid $(M,\varepsilon,\cdot )$ it is shown that a subset $A\subseteq M$ is recognizable in the sense of automata theory if and only if the $\varphi $-rank of $x=x$ is zero in the first-order theory $\operatorname{Th}(M,\varepsilon ,\cdot ,A)$, ... More
Fourier transforms, generic vanishing theorems and polarizations of abelian varietiesFeb 12 1999The purpose of this paper is to give two applications of Fourier transforms and generic vanishing theorems: - we give a cohomological characterization of principal polarizations - we prove that if $X$ an abelian variety and $\Theta $ a polarization of ... More
Efficiencies of Low-Mass Star and Star Cluster FormationJul 25 2000Using a quantitative model for bipolar outflows driven by hydromagnetic protostellar winds, we calculate the efficiency of star formation assuming that available gas is either converted into stars or ejected in outflows. We estimate the efficiency of ... More
The Expulsion of Stellar Envelopes in Core-Collapse SupernovaeJul 04 1998We examine the relation between presupernova stellar structure and the distribution of ejecta in core-collapse supernovae, assuming adiabatic, spherically symmetric flow. We develop a simple yet accurate formula for the blastwave shock velocity, and demonstrate ... More
Protocols and Techniques for a Scalable Atom--Photon Quantum NetworkJun 05 2009Quantum networks based on atomic qubits and scattered photons provide a promising way to build a large-scale quantum information processor. We review quantum protocols for generating entanglement and operating gates between two distant atomic qubits, ... More
Accelerated Randomized BenchmarkingApr 21 2014Sep 24 2014Quantum information processing offers promising advances for a wide range of fields and applications, provided that we can efficiently assess the performance of the control applied in candidate systems. That is, we must be able to determine whether we ... More
Electromagnetic perturbations of a de Sitter black hole in massive gravityJan 08 2017Jan 30 2017The main purpose of this paper is to study quasinormal modes (QNM) of a black hole in massive gravity with a positive cosmological constant due to electromagnetic perturbations. A detailed study of the QNM frequencies for the electromagnetic field is ... More
Ihara's lemma for Shimura curves over totally real fields via patchingJul 13 2019We prove Ihara's lemma for the mod $l$ cohomology of Shimura curves, localised at a maximal ideal of the Hecke algebra, under a large image hypothesis on the associated Galois representation. This was proved by Diamond and Taylor, for Shimura curves over ... More
The Dust Temperature of the "Dusty" Radio Galaxy MG 1019+0535: Evidence for an OutflowSep 22 2000Sep 26 2000Radio galaxies characteristically have strong Lya emission lines. However, a few have Lya equivalent widths that are substantially weaker in relation to other emission lines. One in particular was studied by Dey etal (1995), MG 1019+0535 (z=2.765). We ... More
Virtually geometric words and Whitehead's algorithmApr 04 2009May 16 2010Motivated by a question of Gordon and Wilton, we consider the question of which collections of words are "virtually geometric". In particular, we prove that some words (e.g. bbaaccabc) are not virtually geometric.
The Bowditch boundary of $(G,\mathcal{H})$ when $G$ is hyperbolicApr 14 2015Feb 14 2019In this note we use Yaman's dynamical characterization of relative hyperbolicity to prove a theorem of Bowditch about relatively hyperbolic pairs $(G,\mathcal{H})$ with $G$ hyperbolic. Our proof additionally gives a description of the Bowditch boundary ... More
A geometrically controlled rigidity transition in a model for confluent 3D tissuesJun 08 2017Oct 22 2017The origin of rigidity in disordered materials is an outstanding open problem in statistical physics. Previously, a class of 2D cellular models has been shown to undergo a rigidity transition controlled by a mechanical parameter that specifies cell shapes. ... More
The Effects of Regional Vaccination Heterogeneity on Measles Outbreaks with France as a Case StudyAug 01 2014The rubeola virus, commonly known as measles, is one of the major causes of vaccine-preventable deaths among children worldwide. This is the case despite the fact that an effective vaccine is widely available. Even in developed countries elimination efforts ... More
Actions of certain arithmetic groups on Gromov hyperbolic spacesFeb 25 2007Jul 18 2008We study the variety of actions of a fixed (Chevalley) group on arbitrary geodesic, Gromov hyperbolic spaces. In high rank we obtain a complete classification. In rank one, we obtain some partial results and give a conjectural picture.
Third family flavor physics in an SU(3)^3 \times SU(2)_L \times U(1)_Y modelApr 26 1995We consider a model in which each family transforms under a different SU(3) color group. The low-energy effective theory is an extension of the Standard Model, with additional color octet gauge bosons $G_H$ with mass $M$ that couple preferentially to ... More
Protostellar Disks: Formation, Fragmentation, and the Brown Dwarf DesertAug 27 2004Apr 09 2005We argue that gravitational instability of typical protostellar disks is not a viable mechanism for the fragmentation into multiple systems -- binary stars, brown dwarf companions, or gas giant planets -- except at periods above roughly 20,000 years. ... More