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Winds and Accretion in Young StarsSep 21 2008Establishing the origin of accretion powered winds from forming stars is critical for understanding angular momentum evolution in the star-disk interaction region. Here, the high velocity component of accretion powered winds is launched and accreting ... More

Modeling T Tauri Winds from He I 10830 ProfilesNov 17 2006The high opacity of He I 10830 makes it an exceptionally sensitive probe of the inner wind geometry of accreting T Tauri stars. In this line blueshifted absorption below the continuum results from simple scattering of stellar photons, a situation which ... More

Characterizing the IYJ Excess Continuum Emission in T Tauri StarsJan 24 2011We present the first characterization of the excess continuum emission of accreting T Tauri stars between optical and near-infrared wavelengths. With nearly simultaneous spectra from 0.48 to 2.4 microns acquired with HIRES and NIRSPEC on Keck and SpeX ... More

Understanding the origin of the [OI] low-velocity component from T Tauri starsMay 28 2013The formation time, masses, and location of planets are strongly impacted by the physical mechanisms that disperse protoplanetary disks and the timescale over which protoplanetary material is cleared out. Accretion of matter onto the central star, protostellar ... More

F, G, K, M Spectral Standards in the Y Band (0.95-1.11 um)Nov 10 2009Jan 27 2010We take advantage of good atmospheric transparency and the availability of high quality instrumentation in the 1 um near-infrared atmospheric window to present a grid of F, G, K, and M spectral standards observed at high spectral resolution (R ~ 25,000). ... More

Probing T Tauri Accretion and Outflow with 1 Micron SpectroscopyApr 01 2006In a high dispersion 1 micron survey of 39 classical T Tauri stars veiling is detected in 80%, and He I 10830 and Pgamma line emission in 97% of the stars. On average, the 1 micron veiling exceeds the level expected from previously identified sources ... More

Near-Infrared Classification Spectroscopy: J-Band Spectra of Fundamental MK StandardsJan 31 2000We present a catalog of J-band spectra for 88 fundamental MK standard stars observed at a resolving power of R ~ 3000. This contribution serves as a companion atlas to the K-band spectra published by Wallace and Hinkle (1997) and the H-band atlas of Meyer ... More

Redshifted Absorption at He I 10830 as a Probe of the Accretion Geometry of T Tauri StarsJul 16 2008We probe the geometry of magnetospheric accretion in classical T Tauri stars by modeling red absorption at He I 10830 via scattering of the stellar and veiling continua. Under the assumptions that the accretion flow is an azimuthally symmetric dipole ... More

Double-peaked OI profile: a likely signature of the gaseous ring around KH 15DJun 11 2019KH 15D is a well-known spectroscopic binary because of its unique and dramatic photometric variability. The variability is explained by a circumbinary dust ring but the ring itself was never directly detected. We present a new interpretation of the double-peaked ... More

Interpreting Near Infrared Hydrogen Line Ratios in T Tauri StarsSep 17 2013Sep 19 2013In accreting young stars one of the prominent spectral features in the near infrared is the Paschen and Brackett series in emission. We examine hydrogen line ratios for 16 classical T Tauri stars from SpeX spectra and and assess the trends with veiling ... More

Near-Infrared Classification Spectroscopy: H-band Spectra of Fundamental MK StandardsAug 19 1998We present a catalogue of H-band spectra for 85 stars of approximately solar abundance observed at a resolving power of 3000 with the KPNO Mayall 4m FTS. The atlas covers spectral types O7-M5 and luminosity classes I-V as defined on the MK system. We ... More

Kinematic links and the co-evolution of MHD winds, jets, and inner disks from a high-resolution optical [OI] surveyNov 15 2018We present a survey of optical [OI] emission at 6300 \AA\ toward 65 TTauri stars at the spectral resolution of $\sim7$ km/s. Past work identified a highly blueshifted velocity component (HVC) tracing microjets, and a less blueshifted low-velocity-component ... More

Direct Measurement of Interstellar Extinction Toward Young Stars Using Atomic Hydrogen Lyman-$α$ AbsorptionDec 05 2013Interstellar reddening corrections are necessary to reconstruct the intrinsic spectral energy distributions (SEDs) of accreting protostellar systems. The stellar SED determines the heating and chemical processes that can occur in circumstellar disks. ... More

A New Look at T Tauri Star Forbidden Lines: MHD Driven Winds from the Inner DiskOct 08 2018Magnetohydrodynamic (MHD) and photoevaporative winds are thought to play an important role in the evolution and dispersal of planet-forming disks. We report the first high-resolution ($\Delta v\sim$6\kms) analysis of [S II] $\lambda$4068, [O I] $\lambda$5577, ... More

Organized Behavior Classification of Tweet Sets using Supervised Learning MethodsNov 29 2017During the 2016 US elections Twitter experienced unprecedented levels of propaganda and fake news through the collaboration of bots and hired persons, the ramifications of which are still being debated. This work proposes an approach to identify the presence ... More

Microblog Topic Identification using Linked Open DataApr 06 2018Jan 27 2019The extensive use of social media for sharing and obtaining information has resulted in the development of topic detection models to facilitate the comprehension of the overwhelming amount of short and distributed posts. Probabilistic topic models, such ... More

Accretion Rates for T Tauri Stars Using Nearly Simultaneous Ultraviolet and Optical SpectraMar 04 2013We analyze the accretion properties of 21 low mass T Tauri stars using a dataset of contemporaneous near ultraviolet (NUV) through optical observations obtained with the Hubble Space Telescope Imaging Spectrograph (STIS) and the ground based Small and ... More

Proceedings of the 17th Dutch-Belgian Information Retrieval WorkshopDec 11 2018This volume contains the papers presented at DIR 2018: 17th Dutch-Belgian Information Retrieval Workshop (DIR) held on November 23, 2018 in Leiden. DIR aims to serve as an international platform (with a special focus on the Netherlands and Belgium) for ... More

Ion-cyclotron waves in Solar Coronal HoleSep 07 2011We investigate the effect of the Plume/Interplume Lane (PIPL) structure of the solar Polar Coronal Hole (PCH) on the propagation characteristics of ion-cyclotron waves (ICW). The gradients of physical parameters determined by SOHO and TRACE satellites ... More

Geometric Endoscopy and Mirror SymmetryOct 31 2007Apr 05 2008The geometric Langlands correspondence has been interpreted as the mirror symmetry of the Hitchin fibrations for two dual reductive groups. This mirror symmetry, in turn, reduces to T-duality on the generic Hitchin fibers, which are smooth tori. In this ... More

The Fate of the Initial State Perturbations in Heavy Ion CollisionsMar 23 2009Aug 24 2011Heavy ion collisions at RHIC are well described by the (nearly ideal) hydrodynamics. In the present paper we study propagation of perturbations induced by moving charges (jets) on top of the expanding fireball, using hydrodynamics and (dual) magnetohydrodynamics. ... More

Toward the theory of strongly coupled Quark-Gluon PlasmaOct 10 2005Oct 10 2005We review recent progress toward understanding of sQGP. The phenomenological part includes discussion of elliptic and conical flows at RHIC. Then we proceed to first quantum mechanical studies of manybody states at $T>Tc$, the ``polymeric chains'' $\bar ... More

Toward the AdS/CFT dual of the "Little Bang"Dec 12 2011This (rather subjective) review sums up few years of work devoted to explain various aspects of high energy heavy ion collisions using the AdS/CFT correspondence. The central issue of is is formation of the trapped surface (black hole) phenomenon, seen ... More

The Problem Of Gauge TheoryDec 24 2008Jan 03 2009I sketch what it is supposed to mean to quantize gauge theory, and how this can be made more concrete in perturbation theory and also by starting with a finite-dimensional lattice approximation. Based on real experiments and computer simulations, quantum ... More

Comments On String TheoryDec 19 2002String theory avoids the ultraviolet infinities that arise in trying to quantize gravity. It is also more predictive than conventional quantum field theory, one aspect of this being the way that it contributed to the emergence of the concept of ``supersymmetry'' ... More

BPS Bound States Of D0-D6 And D0-D8 Systems In A B-FieldDec 07 2000Feb 28 2002The D0-D6 system, which is not supersymmetric in the absence of a Neveu-Schwarz B-field, becomes supersymmetric if a suitable constant B-field is turned on. On one side of the supersymmetric locus, this system has a BPS bound state, and on the other side ... More

Some Comments On String DynamicsJul 23 1995Three subjects are considered here: a self-dual non-critical string that appears in Type IIB superstring theory at points in ${\rm K3}$ moduli space where the Type IIA theory has extended gauge symmetry; a conformal field theory singularity at such points ... More

STRONG COUPLING AND THE COSMOLOGICAL CONSTANTJun 15 1995The vanishing of the cosmological constant and absence of a massless dilaton might be explained by a duality between a supersymmetric string vacuum in three dimensions and a non-supersymmetric string vacuum in four dimensions.

Two Dimensional Gauge Theories RevisitedApr 24 1992Topological gravity is equivalent to physical gravity in two dimensions in a way that is still mysterious, though by now it has been proved by Kontsevich. In this paper it is shown that a similar relation between topological and physical Yang-Mills theory ... More

Khovanov Homology And Gauge TheoryAug 15 2011Oct 02 2012In these notes, I will sketch a new approach to Khovanov homology of knots and links based on counting the solutions of certain elliptic partial differential equations in four and five dimensions. The equations are formulated on four and five-dimensional ... More

Supersymmetric Index In Four-Dimensional Gauge TheoriesJun 01 2000This paper is devoted to a systematic discussion of the supersymmetric index Tr (-1)^F for the minimal supersymmetric Yang-Mills theory -- with any simple gauge group G -- primarily in four spacetime dimensions. The index has refinements that probe confinement ... More

Space-Time Transitions in String TheoryJun 21 1993Jun 22 1993Simple mean field methods can be used to describe transitions between different space-time models in string theory. These include transitions between different Calabi-Yau manifolds, and more exotic things such as the Calabi-Yau/Landau-Ginzberg correspondence. ... More

A Note On Einstein, Bergmann, and the Fifth DimensionJan 31 2014This note is devoted to a detail concerning the work of Albert Einstein and Peter Bergmann on unified theories of electromagnetism and gravitation in five dimensions. In their paper of 1938, Einstein and Bergmann were among the first to introduce the ... More

On a fatal error in tachyonic physicsAug 10 2013A fatal error in the famous paper on tachyons by Gerald Feinberg is pointed out. The correct expressions for energy and momentum of tachyons are derived.

The Feynman $i ε$ in String TheoryJul 19 2013The Feynman $i\varepsilon$ is an important ingredient in defining perturbative scattering amplitudes in field theory. Here we describe its analog in string theory. Roughly one takes the string worldsheet to have Lorentz signature when a string is going ... More

Fermion Path Integrals And Topological PhasesAug 19 2015Dec 19 2015Symmetry-protected topological (SPT) phases of matter have been interpreted in terms of anomalies, and it has been expected that a similar picture should hold for SPT phases with fermions. Here, we describe in detail what this picture means for phases ... More

Two Lectures On The Jones Polynomial And Khovanov HomologyJan 27 2014In the first of these two lectures, I describe a gauge theory approach to understanding quantum knot invariants as Laurent polynomials in a complex variable q. The two main steps are to reinterpret three-dimensional Chern-Simons gauge theory in four dimensional ... More

Gauge topology and confinement: an updateFeb 22 2015In the instanton ensemble the fermionic zero modes collectivize and break chiral symmetry. Recent studies of resulting zero mode zone confirm its very small width and overall importance for lattice simulations. Confinement however has been related with ... More

Comment on measurement of the rotaion frequency and the magnetic field at the freezeout of heavy ion collisionsJun 09 2016We suggest other decays which can more effectively identify the effect of rotational motion and presence of the magnetic field, compared to $\Lambda,\bar\Lambda$ hyperon decayse used so far.

Memories of Julian SchwingerDec 02 2014The career and accomplishments of Julian Schwinger, who shared the Nobel Prize for physics in 1965, have been reviewed in numerous books and articles. For this reason these Memories, which seek to convey a sense of Schwinger's remarkable talents as a ... More

A universal exponent for Brownian entropic repulsionNov 25 2014We investigate the extent to which the phenomenon of Brownian entropic repulsion is universal. Consider a Brownian motion conditioned on the event $\mathcal{E}$ -- that its local time is bounded everywhere by 1. This event has probability zero and so ... More

Integrable Lattice Models From Gauge TheoryNov 02 2016These notes provide an introduction to recent work by Kevin Costello in which integrable lattice models of classical statistical mechanics in two dimensions are understood in terms of quantum gauge theory in four dimensions. This construction will be ... More

Fivebranes and KnotsJan 17 2011Aug 11 2011We develop an approach to Khovanov homology of knots via gauge theory (previous physics-based approches involved other descriptions of the relevant spaces of BPS states). The starting point is a system of D3-branes ending on an NS5-brane with a nonzero ... More

The Josephson relation for the superfluid density in the BCS-BEC crossoverJan 29 2008Apr 23 2008The Josephson relation for the superfluid density is derived for a Fermi superfluid in the BCS-BEC crossover. This identity extends the original Josephson relation for Bose superfluids. It gives a simple exact relation between the superfluid density $\rho_s$ ... More

On Schreier unconditional sequencesMar 22 1991Let $(x_n)$ be a normalized weakly null sequence in a Banach space and let $\varep>0$. We show that there exists a subsequence $(y_n)$ with the following property: $$\hbox{ if }\ (a_i)\subseteq \IR\ \hbox{ and }\ F\subseteq \nat$$ satisfies $\min F\le ... More

The Synergy between Numerical and Perturbative Approaches to Black HolesJun 23 1998I describe approaches to the study of black hole spacetimes via numerical relativity. After a brief review of the basic formalisms and techniques used in numerical black hole simulations, I discuss a series of calculations from axisymmetry to full 3D ... More

An SYK-Like Model Without DisorderOct 31 2016Nov 03 2016Making use of known facts about "tensor models," it is possible to construct a quantum system without quenched disorder that has the same large $n$ limit for its correlation functions and thermodynamics as the SYK model. This might be useful in further ... More

Asymmetry gap in the electronic band structure of bilayer grapheneAug 09 2006Nov 02 2006A tight binding model is used to calculate the band structure of bilayer graphene in the presence of a potential difference between the layers that opens a gap $\Delta$ between the conduction and valence bands. In particular, a self consistent Hartree ... More

Gauge Theory and Langlands DualityJun 15 2009The Langlands Program was launched in the late 60s with the goal of relating Galois representations and automorphic forms. In recent years a geometric version has been developed which leads to a mysterious duality between certain categories of sheaves ... More

Free field realizations in representation theory and conformal field theoryAug 18 1994Invited lecture at the International Congress of Mathematicians, Zuerich, August 3-11, 1994 (extended version), reviews free field realizations of affine Kac-Moody and W-algebras and their applications.

Lectures on the Langlands Program and Conformal Field TheoryDec 15 2005These lecture notes give an overview of recent results in geometric Langlands correspondence which may yield applications to quantum field theory. We start with a motivated introduction to the Langlands Program, including its geometric reformulation, ... More

Five Lectures on Soliton EquationsNov 30 1997This is a self-contained review of a new approach to soliton equations of KdV type developed by the author together with B. Feigin and B. Enriquez.

A Scoring System for Continuous Glucose Monitor DataMay 12 2013As continuous glucose monitors (CGMs) are used increasingly by diabetic patients, new and intuitive tools are needed to help patients and their physicians use these streams of data to improve blood glucose management. In this paper, we propose a daily ... More

How much of the outgoing radiation can be intercepted by Schwarzschildean black holes?Sep 11 2000The Schwarzschild spacetime is for electromagnetic waves like a nonuniform medium with a varying refraction index. A fraction of an outgoing radiation scatters off the curvature of the geometry and can be intercepted by a gravitational center. The amount ... More

Global solutions of a free boundary problem for selfgravitating scalar fieldsJun 01 1995Apr 12 1996The weak cosmic censorship hypothesis can be understood as a statement that there exists a global Cauchy evolution of a selfgravitating system outside an event horizon. The resulting Cauchy problem has a free null-like inner boundary. We study a selfgravitating ... More

Heavy Ion Collisions: Achievements and ChallengesDec 29 2014Oct 28 2015A decade ago brief summary of the field could be formulated as a discovery of strongly-coupled Quark-Gluon-Plasma, sQGP, making a very good liquid with surprisingly small viscosity. Since 2010 we have LHC program, which added a lot to our understanding, ... More

A Local Resolution of the Problem of TimeSep 06 2018Sep 24 2018We here announce and outline a solution of this major and longstanding foundational problem, dealing with all seven of its heavily-interrelated local facets.

Absolute versus Relational Debate: a Modern Global VersionMay 24 2018Suppose one seeks to free oneself from a symmetric absolute space by quotienting out its symmetry group. This in general however fails to erase all memory of this absolute space's symmetry properties. Stratification is one major reason for this, which ... More

Shape (In)dependent Inequalities for Triangleland's Jacobi and Democratic-Linear Ellipticity QuantititiesDec 12 2017Sides and medians are both Jacobi coordinate magnitudes, moreover then equably entering the spherical coordinates on Kendall's shape sphere and the Hopf coordinates. This motivates treating medians on the same footing as sides in triangle geometry and ... More

Alice in Triangleland: Lewis Carroll's Pillow Problem and Variants Solved on Shape Space of TrianglesNov 30 2017We provide a natural answer to Lewis Carroll's pillow problem of what is the probability that a triangle is obtuse, Prob(Obtuse). This arises by straightforward combination of a) Kendall's Theorem - that the space of all triangles is a sphere - and b) ... More

Problem of Time: Facets and Machian StrategyJun 25 2013Jul 15 2014The Problem of Time is that `time' in each of ordinary quantum theory and general relativity are mutually incompatible notions. This causes difficulties in trying to put these two theories together to form a theory of Quantum Gravity. The Problem of Time ... More

Specific PDEs for Preserved Quantities in Geometry. I. Similarities and SubgroupsSep 06 2018Sep 24 2018We provide specific PDEs for preserved quantities $Q$ in Geometry, as well as a bridge between this and specific PDEs for observables $O$ in Physics. We furthermore prove versions of four other theorems either side of this bridge: the below enumerated ... More

Machian Classical and Semiclassical Emergent TimeMay 21 2013Nov 25 2013Classical and semiclassical schemes are presented that are timeless at the primary level and recover time from Mach's `time is to be abstracted from change' principle at the emergent secondary level. The semiclassical scheme is a Machian variant of the ... More

On the Semiclassical Approach to Quantum CosmologyJan 25 2011The emergent semiclassical time approach to resolving the problem of time in quantum gravity involves heavy slow degrees of freedom providing via an approximately Hamilton-Jacobi equation an approximate timestandard with respect to which the quantum mechanics ... More

Smallest Relational Mechanics Model of Quantum CosmologyAug 13 2009Relational particle mechanics are models in which there is, overall, no time, position, orientation (nor, sometimes, scale). They are useful for whole-universe modelling - the setting for quantum cosmology. This note concerns 3 particles in 1d in shape-scale ... More

New interpretation of variational principles for gauge theories. I. Cyclic coordinate alternative to ADM splitNov 02 2007I show how there is an ambiguity in how one treats auxiliary variables in gauge theories including general relativity cast as 3 + 1 geometrodynamics. Auxiliary variables may be treated pre-variationally as multiplier coordinates or as the velocities corresponding ... More

Relational mechanics of shape and scaleJan 07 2010Feb 15 2010Relational particle mechanics models (RPM's) are useful models for the problem of time in quantum gravity and other foundational issues in quantum cosmology. Some concrete examples of scalefree RPM's have already been studied, but it is the case with ... More

Higgs portal dark matter in non-thermal cosmologiesApr 18 2018A scalar particle with a relic density set by annihilations through a Higgs portal operator is a simple and minimal possibility for dark matter. However, assuming a thermal cosmological history this model is ruled out over most of parameter space by collider ... More

A note on the Hayman-Wu theoremJul 12 2007The Hayman-Wu theorem states that the preimage of a line or circle L under a conformal mapping from the unit disc to a simply-connected domain U has total Euclidean length bounded by an absolute constant. The best possible constant is known to lie in ... More

Control of radii of convergence and extension of subanalytic functionsNov 23 2001Let g denote a real analytic function on an open subset U of Euclidean space, and let S denote the boundary points of U where g does not admit a local analytic extension. We show that if g is semialgebraic (respectively, globally subanalytic), then S ... More

Singularities in string theoryDec 01 2002String theory is a quantum theory that reproduces the results of General Relativity at long distances but is completely different at short distances. Mathematically, string theory is based on a very new -- and little understood -- framework for geometry ... More

Specific PDEs for Preserved Quantities in Geometry. III. 1-d Projective Transformations and SubgroupsSep 06 2018Sep 24 2018We extend finding geometrically-significant preserved quantities by solving specific PDEs to 1-$d$ projective transformations and subgroups. This can be viewed not only as a purely geometrical problem but also as a subcase of finding physical observables, ... More

Geometry from Brackets ConsistencyNov 01 2018We argue for Brackets Consistency to be a `Pillar of Geometry', i.e.\ a foundational approach, other Pillars being 1) Euclid's constructive approach, 2) the algebraic approach, 3) the projective approach, and 4) the geometrical automorphism groups `Erlangen' ... More

A characterization of Leonard pairs using the parameters $\{a_i\}_{i=0}^{d}$May 20 2012Let $V$ denote a vector space with finite positive dimension. We consider an ordered pair of linear transformations $A: V\to V$ and $A^*: V\to V$ that satisfy (i) and (ii) below. (i) There exists a basis for $V$ with respect to which the matrix representing ... More

A characterization of Leonard pairs using the notion of a tailOct 31 2009Let $V$ denote a vector space with finite positive dimension. We consider an ordered pair of linear transformations $A: V\to V$ and $A^*: V\to V$ that satisfy (i) and (ii) below: (i) There exists a basis for $V$ with respect to which the matrix representing ... More

A scalar curvature bound along the conical Kähler-Ricci flowMay 08 2015Starting with a model conical K\"ahler metric, we prove a uniform scalar curvature bound for solutions to the conical K\"ahler-Ricci flow assuming a semi-ampleness type condition on the twisted canonical bundle. In the proof, we also establish uniform ... More

Towards a Formal Distributional Semantics: Simulating Logical Calculi with TensorsApr 22 2013Apr 28 2013The development of compositional distributional models of semantics reconciling the empirical aspects of distributional semantics with the compositional aspects of formal semantics is a popular topic in the contemporary literature. This paper seeks to ... More

The arithmetic of solidsApr 06 2012The set of segments, each of the next is n times bigger than the first one is a simple geometric interpretation of the set $\mathbb{N}$ of natural numbers. In this paper we investigate the opposite situation. We construct an algebraic structure similar ... More

ElementsSep 30 2015The aim of this work is to show that contemporary mathematics, including Peano arithmetic, is inconsistent, to construct firm foundations for mathematics, and to begin building on these foundations.

Value Monoids of Zero-Dimensional Valuations of Rank OneApr 13 2005Classically, Groebner bases are computed by first prescribing a set monomial order. Moss Sweedler suggested an alternative and developed a framework to perform such computations by using valuation rings in place of monomial orders. We build on these ideas ... More

Lower bounds for h-vectors of k-CM, independence and broken circuit complexesAug 24 2004We present a number of lower bounds for the h-vectors of k-CM, broken circuit and independence complexes. These lead to bounds on the coefficients of the characteristic and reliability polynomials of matroids. The main techniques are the use of series ... More

g-elements of matroid complexesOct 24 2002Let K be the face ring of the independence complex of a matroid. We show that if T is a generic linear system of parameters, then K/T satisfies a weak form of the Hard Lefschetz Theorem. As a result, the first half of the h-vector of the complex satisfies ... More

A Local Resolution of the Problem of Time. IV. Quantum outline and piecemeal ConclusionMay 15 2019Jun 09 2019In this final preliminary piecemeal treatment of local Problem of Time facets, and underlying Background Independence aspects, we first reconsider the nine local facets and aspects considered so far at the quantum level. This is essential both to appreciate ... More

A Local Resolution of the Problem of Time. II. Configurational Relationalism via a generalization of Group AveragingMay 15 2019Jun 09 2019In this article, we consider a second Problem of Time Facet. This started life as Wheeler's Thin Sandwich Problem, within the narrow context of 1) GR-as-Geometrodynamics, in particular its momentum constraint. 2) A Lagrangian variables level treatment. ... More

Steady state clusters and the Rath-Toth mean field forest fire modelSep 10 2018We introduce a random finite rooted tree $\mathcal{C}$, the steady state cluster, characterized by a recursive description: $\mathcal{C}$ is a singleton with probability $1/2$ and otherwise is obtained by joining by an edge the roots of two independent ... More

The Chern-Ricci flow on primary Hopf surfacesMay 30 2019The Hopf surfaces provide a family of minimal non-K\"ahler surfaces of class VII on which little is known about the Chern-Ricci flow. We use a construction of Gauduchon-Ornea for locally conformally K\"ahler metrics on primary Hopf surfaces of class 1 ... More

Comments on the CMS discovery of the "Ridge" in High Multiplicity pp collisions at LHCSep 23 2010A very recent paper by the CMS collaboration \cite{cms_ridge} has created large discussion in the media, which call it important but did not explain why, in some places even calling it "unundestandable". While it is of course too soon to know what causes ... More

Quark-Gluon Plasma - New FrontiersApr 08 2008As implied by organizers, this talk is not a conference summary but rather an outline of progress/challenges/``frontiers'' of the theory. Some fundamental questions addressed are: Why is sQGP such a good liquid? Do we understand (de)confinement and what ... More

Emerging Theory of Strongly Coupled Quark-Gluon PlasmaMar 19 2007RHIC data have shown robust collective flows, including recent spectacular ``conical flow'' from quenched jets: that confirms that QGP above the critical line is in a strongly coupled regime. One way to study Non-Abelian classical strongly coupled plasmas ... More

Physics of Strongly coupled Quark-Gluon PlasmaJul 18 2008Sep 15 2008This review cover our current understanding of strongly coupled Quark-Gluon Plasma (sQGP), especially theoretical progress in (i) explaining the RHIC data by hydrodynamics, (ii) describing lattice data using electric-magnetic duality; (iii) understanding ... More

The conical flow from quenched jets in sQGPSep 05 2006Starting with a reminder of what is strongly coupled Quark-Gluon Plasma (sQGP), we proceed to recent advances in jet quenching and heavy quark diffusion, with a brief summary of various results based on AdS/CFT correspondence. The conical flow is a hydrodynamical ... More

A Cosmological Constant from Gauge Field Instantons?Jul 21 2004Although all interactions in the Standard Model generate nonzero shifts of the vacuum energy and pressure, gravity does not interact with them. Assuming (i) that the reason why it is so breaks down at some scale $M_g$ and that (ii) the instanton-induced ... More

Analytic Continuation Of Chern-Simons TheoryJan 18 2010Aug 28 2010The title of this article refers to analytic continuation of three-dimensional Chern-Simons gauge theory away from integer values of the usual coupling parameter k, to explore questions such as the volume conjecture, or analytic continuation of three-dimensional ... More

Geometric Langlands And The Equations Of Nahm And BogomolnyMay 29 2009Nov 06 2009Geometric Langlands duality relates a representation of a simple Lie group $G^\vee$ to the cohomology of a certain moduli space associated with the dual group $G$. In this correspondence, a principal $SL_2$ subgroup of $G^\vee$ makes an unexpected appearance. ... More

Mirror Symmetry, Hitchin's Equations, And Langlands DualityFeb 07 2008Geometric Langlands duality can be understood from statements of mirror symmetry that can be formulated in purely topological terms for an oriented two-manifold $C$. But understanding these statements is extremely difficult without picking a complex structure ... More

Chiral Ring Of Sp(N) And SO(N) Supersymmetric Gauge Theory In Four DimensionsFeb 25 2003Jul 17 2003The chiral ring of classical supersymmetric Yang-Mills theory with gauge group $Sp(N)$ or SO(N) is computed, extending previous work (of Cachazo, Douglas, Seiberg, and the author) for SU(N). The result is that, as has been conjectured, the ring is generated ... More

Quest For UnificationJul 09 2002The GUT-based approach to physics has been attractive since it was first put forward close to thirty years ago; it has been enriched by new ideas, notably supersymmetry and strings; and there are real hints that it is on the right track, notably from ... More

Deconstruction, G_2 Holonomy, and Doublet-Triplet SplittingJan 04 2002Jan 15 2002We describe a mechanism for using discrete symmetries to solve the doublet-triplet splitting problem of four-dimensional supersymmetric GUT's. We present two versions of the mechanism, one via ``deconstruction,'' and one in terms of M-theory compactification ... More

World-Sheet Corrections Via D-InstantonsJul 07 1999We use a D-instanton or physical gauge approach to re-derive the heterotic string worldsheet instanton contribution to the superpotential in Calabi-Yau compactification. We derive an analogous formula for worldsheet instanton corrections to the moduli ... More

Theta Dependence In The Large N Limit Of Four-Dimensional Gauge TheoriesJul 15 1998The theta dependent of pure gauge theories in four dimensions can be studied using a duality of large N gauge theories with string theory on a certain spacetime. Via this duality, one can argue that for every theta, there are infinitely many vacua that ... More