Results for "Michael Cerny Green"

total 36865took 0.11s
Organic Building Generation in MinecraftJun 11 2019This paper presents a method for generating floor plans for structures in Minecraft (Mojang 2009). Given a 3D space, it will auto-generate a building to fill that space using a combination of constrained growth and cellular automata. The result is a series ... More
General Video Game Rule GenerationJun 12 2019We introduce the General Video Game Rule Generation problem, and the eponymous software framework which will be used in a new track of the General Video Game AI (GVGAI) competition. The problem is, given a game level as input, to generate the rules of ... More
Generating Levels That Teach MechanicsJul 18 2018Oct 01 2018The automatic generation of game tutorials is a challenging AI problem. While it is possible to generate annotations and instructions that explain to the player how the game is played, this paper focuses on generating a gameplay experience that introduces ... More
Data-driven Design: A Case for Maximalist Game DesignMay 30 2018Maximalism in art refers to drawing on and combining multiple different sources for art creation, embracing the resulting collisions and heterogeneity. This paper discusses the use of maximalism in game design and particularly in data games, which are ... More
Two-step Constructive Approaches for Dungeon GenerationJun 11 2019This paper presents a two-step generative approach for creating dungeons in the rogue-like puzzle game MiniDungeons 2. Generation is split into two steps, initially producing the architectural layout of the level as its walls and floor tiles, and then ... More
Who Killed Albert Einstein? From Open Data to Murder Mystery GamesFeb 14 2018This paper presents a framework for generating adventure games from open data. Focusing on the murder mystery type of adventure games, the generator is able to transform open data from Wikipedia articles, OpenStreetMap and images from Wikimedia Commons ... More
AtDelfi: Automatically Designing Legible, Full Instructions For GamesJul 11 2018Sep 17 2018This paper introduces a fully automatic method for generating video game tutorials. The AtDELFI system (AuTomatically DEsigning Legible, Full Instructions for games) was created to investigate procedural generation of instructions that teach players how ... More
Unexpected fading of comet C/2003 T4 (LINEAR) and disintegration of C/2012 S1 (ISON)Aug 17 2014Comet C/2003 T4 (LINEAR) exhibit a large asymmetry in brightness before and after perihelion, when it became much fainter. Large non-gravitational forces shows that mass of nucleus doesn't exceed 2.51*10^11 kg, which is nearly double than previously disintegrated ... More
Modular Forms and $SL(2, {\mathbb Z})$-covariance of type IIB superstring theoryApr 30 2019The local higher-derivative interactions that enter into the low-energy expansion of the effective action of type IIB superstring theory with constant complex modulus generally violate the $U(1)$ R-symmetry of IIB supergravity by $q_U$ units. These interactions ... More
Tree Search vs Optimization Approaches for Map GenerationMar 27 2019Search-based procedural content generation uses stochastic global optimization algorithms to search spaces of game content. However, it has been found that tree search can be competitive with evolution on certain optimization problems. We investigate ... More
Generative Design in Minecraft (GDMC), Settlement Generation CompetitionMar 27 2018Jul 31 2018This paper introduces the settlement generation competition for Minecraft, the first part of the Generative Design in Minecraft challenge. The settlement generation competition is about creating Artificial Intelligence (AI) agents that can produce functional, ... More
Intentional Computational Level DesignApr 18 2019The procedural generation of levels and content in video games is a challenging AI problem. Often such generation relies on an intelligent way of evaluating the content being generated so that constraints are satisfied and/or objectives maximized. In ... More
Evolutionarily-Curated Curriculum Learning for Deep Reinforcement Learning AgentsJan 16 2019In this paper we propose a new training loop for deep reinforcement learning agents with an evolutionary generator. Evolutionary procedural content generation has been used in the creation of maps and levels for games before. Our system incorporates an ... More
Automated Playtesting with Procedural Personas through MCTS with Evolved HeuristicsFeb 19 2018This paper describes a method for generative player modeling and its application to the automatic testing of game content using archetypal player models called procedural personas. Theoretically grounded in psychological decision theory, procedural personas ... More
Exploring transcendentality in superstring amplitudesJun 04 2019It is well known that the low energy expansion of tree-level superstring scattering amplitudes satisfies a suitably defined version of maximum transcendentality. In this paper it is argued that there is a natural extension of this definition that applies ... More
Creating and understanding email communication networks to aid digital forensic investigationsJun 14 2018Digital forensic analysts depend on the ability to understand the social networks of the individuals they investigate. We develop a novel method for automatically constructing these networks from collected hard drives. We accomplish this by scanning the ... More
Bouchaud's model exhibits two different aging regimes in dimension oneOct 29 2002May 20 2005Let E_i be a collection of i.i.d. exponential random variables. Bouchaud's model on Z is a Markov chain X(t) whose transition rates are given by w_{ij}=\nu \exp(-\beta ((1-a)E_i-aE_j)) if i, j are neighbors in Z. We study the behavior of two correlation ... More
Generative Design in Minecraft: Chronicle ChallengeMay 14 2019We introduce the Chronicle Challenge as an optional addition to the Settlement Generation Challenge in Minecraft. One of the foci of the overall competition is adaptive procedural content generation (PCG), an arguably under-explored problem in computational ... More
Two loops in eleven dimensionsOct 06 1999Sep 19 2005The two-loop Feynman diagram contribution to the four-graviton amplitude of eleven-dimensional supergravity compactified on a two-torus, T^2, is analyzed in detail. The Schwinger parameter integrations are re-expressed as integration over the moduli space ... More
DATA AgentSep 28 2018This paper introduces DATA Agent, a system which creates murder mystery adventures from open data. In the game, the player takes on the role of a detective tasked with finding the culprit of a murder. All characters, places, and items in DATA Agent games ... More
"Press Space to Fire": Automatic Video Game Tutorial GenerationMay 30 2018We propose the problem of tutorial generation for games, i.e. to generate tutorials which can teach players to play games, as an AI problem. This problem can be approached in several ways, including generating natural language descriptions of game rules, ... More
Universality of the REM for dynamics of mean-field spin glassesJun 14 2007We consider a version of a Glauber dynamics for a p-spin Sherrington--Kirkpatrick model of a spin glass that can be seen as a time change of simple random walk on the N-dimensional hypercube. We show that, for any p>2 and any inverse temperature \beta>0, ... More
Temporal and Semantic Effects on Multisensory IntegrationJun 15 2016How do we integrate modality-specific perceptual information arising from the same physical event into a coherent percept? One possibility is that observers rely on information across perceptual modalities that shares temporal structure and/or semantic ... More
Nucleon axial, scalar, and tensor charges using lattice QCD at the physical pion massMar 15 2019May 16 2019We report on lattice QCD calculations of the nucleon isovector axial, scalar, and tensor charges. Our calculations are performed on two 2+1-flavor ensembles generated using a 2-HEX-smeared Wilson-clover action at the physical pion mass and lattice spacings ... More
Computing the nucleon charge and axial radii directly at $Q^2=0$ in lattice QCDNov 30 2017We describe a procedure for extracting momentum derivatives of nucleon matrix elements on the lattice directly at $Q^2=0$. This is based on the Rome method for computing momentum derivatives of quark propagators. We apply this procedure to extract the ... More
The Class 0 Protostar BHR71: Herschel Observations and Dust Continuum ModelsJan 03 2017We use Herschel spectrophotometry of BHR71, an embedded Class 0 protostar, to provide new constraints on its physical properties. We detect 645 (non-unique) spectral lines amongst all spatial pixels. At least 61 different spectral lines originate from ... More
Nucleon structure with pion mass down to 149 MeVNov 01 2012We present isovector nucleon observables: the axial, tensor, and scalar charges and the Dirac radius. Using the BMW clover-improved Wilson action and pion masses as low as 149 MeV, we achieve good control over chiral extrapolation to the physical point. ... More
Chandra X-ray and Hubble Space Telescope Imaging of Optically Selected kiloparsec-Scale Binary Active Galactic Nuclei I. Nature of the Nuclear Ionizing SourcesSep 24 2012Dec 14 2012Kiloparsec-scale binary active galactic nuclei (AGNs) signal active supermassive black hole (SMBH) pairs in merging galaxies. Despite their significance, unambiguously confirmed cases remain scarce and most have been discovered serendipitously. In a previous ... More
Nucleon electromagnetic form factors at high $Q^2$ from Wilson-clover fermionsOct 09 2018We present results on the nucleon electromagnetic form factors from Lattice QCD at momentum transfer up to about $12$~GeV$^2$. We analyze two gauge ensembles with the Wilson-clover fermion action, a lattice spacing of $a\approx 0.09$~fm and pion masses ... More
Directed random walk on the backbone of an oriented percolation clusterApr 13 2012Jun 17 2013We consider a directed random walk on the backbone of the infinite cluster generated by supercritical oriented percolation, or equivalently the space-time embedding of the ``ancestral lineage'' of an individual in the stationary discrete-time contact ... More
A rheological state diagram for rough colloids in shear flowOct 28 2016The flow of dense suspensions, glasses, and granular materials is heavily influenced by frictional interactions between constituent particles. However, neither hydrodynamics nor friction has successfully explained the full range of flow phenomena in concentrated ... More
Hadron Structure from Lattice QCDDec 15 2014Recent progress in lattice QCD calculations of nucleon structure will be presented. Calculations of nucleon matrix elements and form factors have long been difficult to reconcile with experiment, but with advances in both methodology and computing resources, ... More
Systematics in nucleon matrix element calculationsDec 26 2018The current status of calculations of simple nucleon structure observables is reviewed, with a focus on the axial charge. A major challenge is the combination of an exponentially decaying signal-to-noise ratio and the need for large source-sink separations ... More
On the Energy Decay Rate of the Fractional Wave Equation on $\mathbb{R}$ with Relatively Dense DampingApr 24 2019We establish upper bounds for the decay rate of the energy of the damped fractional wave equation when the averages of the damping coefficient on all intervals of a fixed length are bounded below. If the power of the fractional Laplacian, $s$, is between ... More
Testing the Binary Trigger Hypothesis in FUorsMay 11 2016We present observations of three FU Orionis objects (hereafter, FUors) with nonredundant aperture-mask interferometry (NRM) at 1.59 um and 2.12 um that probe for binary companions on the scale of the protoplanetary disk that feeds their accretion outbursts. ... More
High-precision calculation of the strange nucleon electromagnetic form factorsMay 07 2015May 22 2015We report a direct lattice QCD calculation of the strange nucleon electromagnetic form factors $G_E^s$ and $G_M^s$ in the kinematic range $0 \leq Q^2 \lesssim 1.2\: {\rm GeV}^2$. For the first time, both $G_E^s$ and $G_M^s$ are shown to be nonzero with ... More
Extension of ATLAST/LUVOIR's Capabilities to 5 Microns, or BeyondMay 14 2016ATLAST is a particular realization of LUVOIR, the Large Ultraviolet Optical Infrared telescope, a ~10 m diameter space telescope being defined for consideration in the 2020 Decadal Review of astronomy and astrophysics. ATLAST/LUVOIR is generally thought ... More
Controlling Excited-State Contamination in Nucleon Matrix ElementsFeb 24 2016Jan 15 2017We present a detailed analysis of methods to reduce statistical errors and excited-state contamination in the calculation of matrix elements of quark bilinear operators in nucleon states. All the calculations were done on a 2+1 flavor ensemble with lattices ... More
Space density of optically-selected type 2 quasarsJan 08 2008Feb 16 2010Type 2 quasars are luminous active galactic nuclei (AGN) whose central regions are obscured by large amounts of gas and dust. In this paper, we present a catalog of type 2 quasars from the Sloan Digital Sky Survey (SDSS), selected based on their optical ... More
Cosmic Origins Spectrograph Detection of Ne VIII Tracing Warm - Hot Gas Towards PKS 0405-123Aug 19 2010We report on the detection of Ne VIII in the HST/Cosmic Origins Spectrograph spectrum of the intervening absorption system at z = 0.495096 towards PKS 0405-123. The high S/N COS spectrum also covers absorption from H I, C III, O III, O IV and O VI associated ... More
The Analogous Structure of Accretion Flows in Supermassive and Stellar Mass Black HolesMar 06 2019Black holes grow rapidly through the accretion of gas. As the accretion rate onto a black hole decreases, the structure of its surrounding accretion flow is believed to dramatically transition from a luminous thin disc to become quasi-spherical and radiatively ... More
Characterizing the Circumgalactic Medium of Nearby Galaxies with HST/COS and HST/STIS Absorption-Line Spectroscopy: II. Methods and ModelsApr 01 2017We present basic data and modeling for a survey of the cool, photo-ionized Circum-Galactic Medium (CGM) of low-redshift galaxies using far-UV QSO absorption line probes. This survey consists of "targeted" and "serendipitous" CGM subsamples, originally ... More
Innocent Bystanders: Carbon Stars from the Sloan Digital Sky SurveyJan 17 2013Jan 22 2013Among stars showing carbon molecular bands (C stars), the main sequence dwarfs, likely in post-mass transfer binaries, are numerically dominant in the Galaxy. Via spectroscopic selection from the Sloan Digital Sky Survey, we retrieve 1220 C stars, ~5 ... More
The Relationship Between the High Energy Continuum and Emission Lines in QSOs: A Low-Redshift SampleMar 18 1996Quasar emission lines are sensitive to both the luminosity and shape of the quasars' high energy continuum - primarily in the soft X-ray and the (obscured) extreme ultraviolet. We initiate the first large-scale, multi-line investigation of correlations ... More
DarkCapPy: Dark Matter Capture and AnnihilationAug 10 2018DarkCapPy is a Python 3/Jupyter package for calculating rates associated with dark matter capture in the Earth, annihilation into light mediators, and the subsequent observable decay of the light mediators near the surface of the Earth. The package includes ... More
Cellular algebras arising from Hecke algebras of type H_nDec 04 1997We study a finite-dimensional quotient of the Hecke algebra of type $H_n$ for general $n$, using a calculus of diagrams. This provides a basis of monomials in a certain set of generators. Using this, we prove a conjecture of C.K. Fan about the semisimplicity ... More
Will Central Counterparties become the New Rating Agencies?Nov 26 2012Nov 28 2012Central Counterparties (CCPs) are widely promoted as a requirement for safe banking with little dissent except on technical grounds (such as proliferation of CCPs). Whilst CCPs can have major operational positives, we argue that CCPs have many of the ... More
Regulatory-Optimal FundingOct 12 2013Aug 12 2014Funding is a cost to trading desks that they see as an input. Current FVA-related literature reflects this by also taking funding costs as an input, usually constant, and always risk-neutral. However, this funding curve is the output from a Treasury point ... More
The essential ideal in group cohomology does not square to zeroFeb 27 2003Sep 09 2003Let G be the Sylow 2-subgroup of the unitary group $SU_3(4)$. We find two essential classes in the mod-2 cohomology ring of G whose product is nonzero. In fact, the product is the ``last survivor'' of Benson-Carlson duality. Recent work of Pakianathan ... More
Introduction to finite mixturesMay 03 2017May 05 2018Mixture models have been around for over 150 years, as an intuitively simple and practical tool for enriching the collection of probability distributions available for modelling data. In this chapter we describe the basic ideas of the subject, present ... More
VAR and ES/CVAR Dependence on data cleaning and Data Models: Analysis and ResolutionMay 29 2014Historical (Stressed-) Value-at-Risk ((S)VAR), and Expected Shortfall (ES), are widely used risk measures in regulatory capital and Initial Margin, i.e. funding, computations. However, whilst the definitions of VAR and ES are unambiguous, they depend ... More
Warehousing Credit (CVA) Risk, Capital (KVA) and Tax (TVA) ConsequencesJul 11 2014Jan 07 2015Credit risk may be warehoused by choice, or because of limited hedging possibilities. Credit risk warehousing increases capital requirements and leaves open risk. Open risk must be priced in the physical measure, rather than the risk neutral measure, ... More
MVA: Initial Margin Valuation Adjustment by Replication and RegressionMay 02 2014Jan 12 2015Initial margin requirements are becoming an increasingly common feature of derivative markets. However, while the valuation of derivatives under collateralisation (Piterbarg 2010, Piterbarg2012), under counterparty risk with unsecured funding costs (FVA) ... More
Bredon-Poincare Duality GroupsNov 29 2013Jan 08 2014If $G$ is a group which admits a manifold model for $\mathrm{B}G$ then $G$ is a Poincar\'e duality group. We study a generalisation of Poincar\'e duality groups, introduced initially by Davis and Leary, motivated by groups $G$ with cocompact manifold ... More
Leading coefficients of Kazhdan--Lusztig polynomials and fully commutative elementsJan 10 2008Let $W$ be a Coxeter group of type $\widetilde{A}_{n-1}$. We show that the leading coefficient, $\mu(x, w)$, of the Kazhdan--Lusztig polynomial $P_{x, w}$ is always equal to 0 or 1 if $x$ is fully commutative (and $w$ is arbitrary).
Gröbner bases for p-group algebrasOct 09 2009Experiment shows that the reverse length-lexicographical word ordering consistently yields far smaller Gr\"obner bases for modular p-group algebras than the length-lexicographical ordering. For the so-called Jennings word ordering, based on a special ... More
Deeply Learning DerivativesSep 06 2018Oct 17 2018This paper uses deep learning to value derivatives. The approach is broadly applicable, and we use a call option on a basket of stocks as an example. We show that the deep learning model is accurate and very fast, capable of producing valuations a million ... More
Regulatory-Compliant Derivatives Pricing is Not Risk-NeutralNov 01 2013Aug 12 2014Regulations impose idiosyncratic capital and funding costs for holding derivatives. Capital requirements are costly because derivatives desks are risky businesses; funding is costly in part because regulations increase the minimum funding tenor. Idiosyncratic ... More
XVA at the Exercise BoundaryOct 02 2016XVA is a material component of a trade valuation and hence it must impact the decision to exercise options within a given netting set. This is true for both unsecured trades and secured / cleared trades where KVA and MVA play a material role even if CVA ... More
The nil Temperley--Lieb algebra of type affine CMar 07 2017Mar 14 2019We introduce a type affine $C$ analogue of the nil Temperley--Lieb algebra, in terms of generators and relations. We show that this algebra $T(n)$, which is a quotient of the positive part of a Kac--Moody algebra of type $D_{n+1}^{(2)}$, has an easily ... More
A deterministic pseudorandom perturbation scheme for arbitrary polynomial predicatesAug 08 2013We present a symbolic perturbation scheme for arbitrary polynomial geometric predicates which combines the benefits of Emiris and Canny's simple randomized linear perturbation scheme with Yap's multiple infinitesimal scheme for general predicates. Like ... More
Searches for Compositeness at the TevatronApr 28 2000Quark-quark and quark-lepton searches for compositenss at the Fermilab Tevatron are summarized. These are of the contact-interaction variety where sqrt(s-hat) < the hypothesized mass scales, Lambda. Tevatron experiments limit a variety of compositeness ... More
Collateral-Enhanced Default RiskFeb 19 2013Changes in collateralization have been implicated in significant default (or near-default) events during the financial crisis, most notably with AIG. We have developed a framework for quantifying this effect based on moving between Merton-type and Black-Cox-type ... More
On Carlson's depth conjecture in group cohomologyJun 12 2002We establish a weak form of Carlson's conjecture on the depth of the mod-p cohomology ring of a p-group. In particular, Duflot's lower bound for the depth is tight if and only if the cohomology ring is not detected on a certain family of subgroups. The ... More
Testing Benson's Regularity ConjectureOct 11 2007Aug 13 2008D. J. Benson conjectures that the Castelnuovo-Mumford regularity of a group cohomology ring is always zero. More generally he conjectures that the cohomology ring always has a system of parameters satisfying a property he calls very strong quasi-regular. ... More
Integral traces of weak Maass forms of genus zero odd prime levelJul 08 2013Duke and the second author defined a family of linear maps from spaces of weakly holomorphic modular forms of negative integral weight and level 1 into spaces of weakly holomorphic modular forms of half integral weight and level 4 and showed that these ... More
The Geometry of Strong Koszul AlgebrasFeb 09 2017Koszul algebras with quadratic Groebner bases, called strong Koszul algebras, are studied. We introduce affine algebraic varieties whose points are in one-to-one correspondence with certain strong Koszul algebras and we investigate the connection between ... More
Compact Gravity Wave DetectorSep 04 2002Aug 06 2017An incoming gravity wave being a stress wave is a surface with intrinsic curvature. When a light beam is parallel transported on this non-Euclidian surface it acquires an excess phase which accumulates with each curcuit. We calculate the separate contributions ... More
The Maintenance of Sex: Ronald Fisher meets the Red QueenApr 10 2013Apr 23 2013Sex in higher diploids carries a two-fold cost of males that should reduce its fitness relative to cloning and result in its extinction. Instead, sex is widespread and it is clonal species that face early obsolescence. One possible reason is that sex ... More
Generalized Temperley-Lieb algebras and decorated tanglesDec 04 1997We give presentations, by means of diagrammatic generators and relations, of the analogues of the Temperley-Lieb algebras associated as Hecke algebra quotients to Coxeter graphs of type B and $D$. This generalizes Kauffman's diagram calculus for the Temperley-Lieb ... More
New bounds for Szemerédi's theorem, III: A polylogarithmic bound for $r_4(N)$May 04 2017Aug 10 2017Define $r_4(N)$ to be the largest cardinality of a set $A \subset \{1,\dots,N\}$ which does not contain four elements in arithmetic progression. In 1998 Gowers proved that \[ r_4(N) \ll N(\log \log N)^{-c}\] for some absolute constant $c>0$. In 2005, ... More
Reconstructing toric quiver flag varieties from a tilting bundleJun 16 2017Oct 14 2017We prove that every toric quiver flag variety $Y$ is isomorphic to a fine moduli space of cyclic modules over the algebra $\text{End}(T)$ for some tilting bundle $T$ on $Y$. This generalises the well known fact that $\mathbb{P}^n$ can be recovered from ... More
Dirac Processes and Default RiskApr 17 2015We introduce Dirac processes, using Dirac delta functions, for short-rate-type pricing of financial derivatives. Dirac processes add spikes to the existing building blocks of diffusions and jumps. Dirac processes are Generalized Processes, which have ... More
Self-Financing Trading and the Ito-Doeblin LemmaJan 12 2015The objective of the note is to remind readers on how self-financing works in Quantitative Finance. The authors have observed continuing uncertainty on this issue which may be because it lies exactly at the intersection of stochastic calculus and finance. ... More
Efficient XVA Management: Pricing, Hedging, and Attribution using Trade-Level Regression and Global ConditioningDec 17 2014Dec 22 2014Banks must manage their trading books, not just value them. Pricing includes valuation adjustments collectively known as XVA (at least credit, funding, capital and tax), so management must also include XVA. In trading book management we focus on pricing, ... More
KVA: Capital Valuation AdjustmentMay 02 2014Oct 24 2014Credit (CVA), Debit (DVA) and Funding Valuation Adjustments (FVA) are now familiar valuation adjustments made to the value of a portfolio of derivatives to account for credit risks and funding costs. However, recent changes in the regulatory regime and ... More
Option-Based Pricing of Wrong Way Risk for CVASep 03 2016Oct 02 2016The two main issues for managing wrong way risk (WWR) for the credit valuation adjustment (CVA, i.e. WW-CVA) are calibration and hedging. Hence we start from a novel model-free worst-case approach based on static hedging of counterparty exposure with ... More
Mid-Infrared Selection of Active GalaxiesOct 21 2004Mid-infrared photometry provides a robust technique for identifying active galaxies. While the ultraviolet to mid-infrared continuum of normal galaxies is dominated by the composite stellar black body curve and peaks at approximately 1.6 microns, the ... More
A GAS OF D-INSTANTONSApr 21 1995A D-instanton is a space-time event associated with world-sheet boundaries that contributes non-perturbative effects of order $e^{-const/\kappa}$ to closed-string amplitudes. Some properties of a gas of D-instantons are discussed in this paper.
Vacuum Values for Auxiliary String FieldsApr 27 1994Apr 27 1994Auxiliary string fields are introduced in light-cone gauge string field theory in order to express contact interactions as contractions of cubic vertices. The auxiliary field in the purely closed-string bosonic theory may be given a non-zero expectation ... More
The Influence of World-Sheet Boundaries on Critical Closed String TheoryDec 14 1992This paper considers interactions between closed strings and open strings satisfying either Neumann or constant (point-like) Dirichlet boundary conditions in a BRST formalism in the critical dimension. With Neumann conditions this reproduces the well-known ... More
D-instanton partition functionsApr 20 1998Apr 30 1998Duality arguments are used to determine D-instanton contributions to certain effective interaction terms of type II supergravity theories in various dimensions. This leads to exact expressions for the partition functions of the finite N D-instanton matrix ... More
Light-cone supersymmetry and D-branesApr 16 1996$D$-brane boundary states for type II superstrings are constructed by enforcing the conditions that preserve half of the space-time supersymmetry. A light-cone coordinate frame is used where time is identified as one of the coordinates transverse to the ... More
Point-Like States for Type 2b SuperstringsMar 07 1994This paper considers closed-string states of type 2b superstring theory in which the whole string is localized at a single point in superspace. Correlation functions of these (scalar and pseudoscalar) states possess an infinite number of position-space ... More
World-volumes and string target spacesFeb 12 1996String duality suggests a fascinating juxtoposition of world-volume and target-space dynamics. This is particularly apparent in the $D$-brane description of stringy solitons that forms a major focus of this article (which is {\it not} intended to be a ... More
Connections between M-theory and superstringsDec 19 1997This article reviews the non-perturbative structure of certain higher derivative terms in the type II string theory effective action and their connection to one-loop effects in eleven-dimensional supergravity compactified on a torus. New material is also ... More
Boundary Effects in String TheoryOct 04 1995Some of the properties of string theory defined on world-sheets with boundaries are reviewed. Particular emphasis is put on the possibility of identifying string configurations (\lq D-instantons' and \lq D-branes') that give rise to stringy non-perturbative ... More
Temperature Dependence of String Theory in the Presence of World-Sheet BoundariesJan 27 1992Jan 29 1992The effect of world-sheet boundaries on the temperature-dependence of bosonic string theory is studied to first order in string perturbation theory. The high- temperature behaviour of a theory with Dirichlet boundary conditions has features suggestive ... More
Interconnections between type II superstrings, M theory and N=4 supersymmetric Yang--MillsMar 15 1999These lecture notes begin with a review of the first nonleading contributions to the derivative expansion of the M theory effective action compactified on a two-torus. The form of these higher-derivative interactions is shown to follow from ten-dimensional ... More
Speculations on AdS/CFT at all orders in 1/NMar 31 1999Apr 01 1999Paper withdrawn. The argument was based on a misconception
D-instanton induced interactions on a D3-braneFeb 01 2000Feb 07 2000Non-perturbative features of the derivative expansion of the effective action of a single D3-brane are obtained by considering scattering amplitudes of open and closed strings. This motivates expressions for the coupling constant dependence of world-volume ... More
Comments on Three-BranesFeb 15 1996Feb 21 1996The Born--Infeld-like effective world-volume theory of a single 3-brane is deduced from a manifestly space-time supersymmetric description of the corresponding $D$-brane. This is shown to be invariant under $SL(2,R)$ transformations that act on the abelian ... More
Effects of D-instantonsJan 20 1997Jul 07 1997Scattering of fundamental states of type IIB supergravity and superstring theory is discussed at low orders in perturbation theory in the background of a D-instanton. The integration over fermionic zero modes in both the low energy supergravity and in ... More
Symmetry Breaking at enhanced Symmetry PointsSep 29 1995The influence of world-sheet boundary condensates on the toroidal compactification of bosonic string theories is considered. At the special points in the moduli space at which the closed-string theory possesses an enhanced unbroken $G\times G$ symmetry ... More
Broad Absorption Line QSOs Observed by the ROSAT PSPCDec 06 1995Recent results from the ROSAT All-Sky Survey (RASS) have shown that broad absorption line (BAL) QSOs are either highly absorbed or underluminous in the soft X-ray bandpass. Here, we extend this work by analyzing all known bona fide BALQSOs observed within ... More
High-frequency performance of scaled carbon nanotube array field-effect transistorsAug 03 2012We report the radio-frequency performance of carbon nanotube array transistors that have been realized through the aligned assembly of highly separated, semiconducting carbon nanotubes on a fully scalable device platform. At a gate length of 100 nm, we ... More
Periodic solutions to a mean-field model for electrocortical activityJul 04 2014We consider a continuum model of electrical signals in the human cortex, which takes the form of a system of semilinear, hyperbolic partial differential equations for the inhibitory and excitatory membrane potentials and the synaptic inputs. The coupling ... More
Episodic Accretion in Young StarsJan 14 2014In the last twenty years, the topic of episodic accretion has gained significant interest in the star formation community. It is now viewed as a common, though still poorly understood, phenomenon in low-mass star formation. The FU Orionis objects (FUors) ... More
Obtaining material identification with cosmic ray radiographyOct 23 2012The passage of muons through matter is mostly affected by their Coulomb interactions with electrons and nuclei. The muon interactions with electrons lead to continuous energy loss and stopping of muons, while their scattering off nuclei lead to angular ... More
The Herschel-PACS legacy of low-mass protostars: Properties of warm and hot gas and its origin in far-UV illuminated shocksFeb 09 2018Recent observations from Herschel allow the identification of important mechanisms responsible for the heating of gas surrounding low-mass protostars and its subsequent cooling in the far-infrared (FIR). Shocks are routinely invoked to reproduce some ... More