WorldWideScience

Sample records for string extension learning

  1. Extensions of string theories

    Energy Technology Data Exchange (ETDEWEB)

    Amorim, R.; Barcelos-Neto, J. (Universidade Federal do Rio de Janeiro, RJ (Brazil). Inst. de Fisica)

    1993-06-01

    With the motivation that critical dimensions D[ne]4 might be suggeting that string theories have not been completely formulated, we study more general alternatives. We first consider a direct extension in the world-sheet formulation with N[sub B] bosons and N[sub F] fermions and analyze the conditions for canceling the anomaly in all possible combinations of N[sub B], N[sub F] and D. Later on we incorporate degrees of freedom of antisymmetric tensors to the previous model. The only possibility to cancel the anomaly in this case is with N[sub B]=N[sub F]=1 and the our everyday spacetime dimension D=4. (orig.).

  2. Machine-learning the string landscape

    Directory of Open Access Journals (Sweden)

    Yang-Hui He

    2017-11-01

    Full Text Available We propose a paradigm to apply machine learning various databases which have emerged in the study of the string landscape. In particular, we establish neural networks as both classifiers and predictors and train them with a host of available data ranging from Calabi–Yau manifolds and vector bundles, to quiver representations for gauge theories, using a novel framework of recasting geometrical and physical data as pixelated images. We find that even a relatively simple neural network can learn many significant quantities to astounding accuracy in a matter of minutes and can also predict hithertofore unencountered results, whereby rendering the paradigm a valuable tool in physics as well as pure mathematics.

  3. Machine-learning the string landscape

    Science.gov (United States)

    He, Yang-Hui

    2017-11-01

    We propose a paradigm to apply machine learning various databases which have emerged in the study of the string landscape. In particular, we establish neural networks as both classifiers and predictors and train them with a host of available data ranging from Calabi-Yau manifolds and vector bundles, to quiver representations for gauge theories, using a novel framework of recasting geometrical and physical data as pixelated images. We find that even a relatively simple neural network can learn many significant quantities to astounding accuracy in a matter of minutes and can also predict hithertofore unencountered results, whereby rendering the paradigm a valuable tool in physics as well as pure mathematics. Of course, this paradigm is useful not only to physicists but to also to mathematicians; for instance, could our NN be trained well enough to approximate bundle cohomology calculations? This, and a host of other examples, we will now examine.Methodology  Neural networks are known for their complexity, involving usually a complicated directed graph each node of which is a ;perceptron; (an activation function imitating a neuron) and amongst the multitude of which there are many arrows encoding input/output. Throughout this letter, we will use a rather simple multi-layer perceptron (MLP) consisting of 5 layers, three of which are hidden, with activation functions typically of the form of a logistic sigmoid or a hyperbolic tangent. The input layer is a linear layer of 100 to 1000 nodes, recognizing a tensor (as we will soon see, algebro-geometric objects such as Calabi-Yau manifolds or polytopes are generically configurations of integer tensors) and the output layer is a summation layer giving a number corresponding to a Hodge number, or to rank of a cohomology group, etc. Such an MLP can be implemented, for instance, on the latest versions of Wolfram Mathematica. With 500-1000 training rounds, the running time is merely about 5-20 minutes on an ordinary laptop. It

  4. Learning Joomla! 3 extension development

    CERN Document Server

    Plummer, Tim

    2013-01-01

    A practical guide with step-by-step examples that build on each other so you can learn by doing and get hands-on knowledge about creating your plugins, modules, and components in Joomla.""Learning Joomla! 3 Extension Development, Third Edition"" is for developers who want to create their own Joomla extensions. It is assumed you will have some basic PHP, HTML, and CSS knowledge, but you don't need any prior Joomla programming experience. This book will also be useful to people who just want to make minor customizations to existing Joomla extensions and build on the work of others in the open so

  5. Extensive Reading and Learning Style

    OpenAIRE

    Kawachi, Tomoko; 河内, 智子

    2015-01-01

    Extensive reading (ER) has been shown to be an effective approach to both improving students’ language skills and nurturing positive attitudes toward language reading and learning. However, although the approach has proven to be effective for many learners, as with any teaching approach, it does not seem to work equally well for all learners. The current study hypothesized that learning style might be a factor influencing learners’ achievement in and attitude toward ER, and investigated the r...

  6. Informing New String Programmes: Lessons Learned from an Australian Experience

    Science.gov (United States)

    Murphy, Fintan; Rickard, Nikki; Gill, Anneliese; Grimmett, Helen

    2011-01-01

    Although there are many examples of notable string programmes there has been relatively little comparative analysis of these programmes. This paper examines three benchmark string programmes (The University of Illinois String Project, The Tower Hamlets String Teaching Project and Colourstrings) alongside Music4All, an innovative string programme…

  7. Pigeons learn virtual patterned-string problems in a computerized touch screen environment.

    Science.gov (United States)

    Wasserman, Edward A; Nagasaka, Yasuo; Castro, Leyre; Brzykcy, Stephen J

    2013-09-01

    For many decades, developmental and comparative psychologists have used a variety of string tasks to assess the perceptual and cognitive capabilities of human children of different ages and different species of nonhuman animals. The most important and widely used of these problems are patterned-string tasks, in which the organism is shown two or more strings, only one of which is connected to a reward. The organism must determine which string is attached to the reward and pull it. We report a new way to implement patterned-string tasks via a computerized touch screen apparatus. Pigeons successfully learned such virtual patterned-string tasks and exhibited the same general performance profile as animals given conventional patterned-string tasks. In addition, variations in the length, separation, and alignment of the strings reliably affected the pigeons' virtual string-pulling behavior. These results not only testify to the power and versatility of our computerized string task, but they also demonstrate that pigeons can concurrently contend with a broad range of demanding patterned-string problems, thereby eliminating many alternative interpretations of their behavior. The virtual patterned-string task may thus permit expanded exploration of other species and variables which would be unlikely to be undertaken either because of inadequacies of conventional methodology or sensorimotor limitations of the studied organisms.

  8. Dogs (Canis familiaris) can learn to attend to connectivity in string pulling tasks.

    Science.gov (United States)

    Riemer, Stefanie; Müller, Corsin; Range, Friederike; Huber, Ludwig

    2014-02-01

    String pulling tasks are commonly used to investigate recognition of means-end connections. Previous studies suggested that dogs base their choice on proximity rather than connectivity (Osthaus, Lea, & Slater, 2005), nonetheless, dogs performed successfully in the related support problem (Range, Hentrup, & Virányi, 2011). To reinvestigate dogs' means-end understanding, we tested 34 Border collies in string pulling tasks in which the proximity of the reward to the connected string's end was varied. First, subjects were presented with a four-string task (four parallel perpendicular strings, one baited, with the reward in line with the correct string's end). Dogs that performed above chance in this task were tested with a curved string task, involving one straight and one curved string. When the reward was attached to the curved string, it was equidistant from both strings' ends so that choosing by proximity was not possible. Although group level performance was significantly above chance, only three of 20 dogs met criterion individually, of which one dog subsequently solved a broken string task upon its first presentation. However, the dogs seemed to be unable to overcome their proximity bias in a parallel diagonal string task where proximity of the unconnected string's end to the reward was misleading. We conclude that although dogs may not demonstrate means-end understanding spontaneously, some can learn to pay attention to connectivity when proximity is not a confounding factor. This study supports the notion that animals may apply several alternative strategies to solve physical problems, which are influenced by the test-setup.

  9. Dogs can learn to attend to connectivity in string pulling tasks

    Science.gov (United States)

    Riemer, Stefanie; Müller, Corsin; Range, Friederike; Huber, Ludwig

    2014-01-01

    String pulling tasks are commonly used to investigate recognition of means-end connections. Previous studies suggested that dogs base their choice on proximity rather than connectivity (Osthaus, Lea, & Slater, 2005), nonetheless, dogs performed successfully in the related support problem (Range, Hentrup, & Virányi, 2011). To re-investigate dogs’ means-end understanding, we tested 34 Border collies in string pulling tasks in which the proximity of the reward to the connected string’s end was varied. First, subjects were presented with a four-string task (four parallel perpendicular strings, one baited, with the reward in line with the correct string’s end). Dogs that performed above chance in this task were tested with a curved string task, involving one straight and one curved string. When the reward was attached to the curved string, it was equidistant from both strings’ ends so that choosing by proximity was not possible. While group level performance was significantly above chance, only three of 20 dogs met criterion individually, of which one dog subsequently solved a broken string task upon its first presentation. However, the dogs seemed to be unable to overcome their proximity bias in a parallel diagonal string task where proximity of the unconnected string’s end to the reward was misleading. We conclude that although dogs may not demonstrate means-end understanding spontaneously, some can learn to pay attention to connectivity when proximity is not a confounding factor. This study supports the notion that animals may apply several alternative strategies to solve physical problems, which are influenced by the test-setup. PMID:23875921

  10. Learning Tree Adjoining Grammars from structures and strings

    NARCIS (Netherlands)

    Costa Florêncio, C.

    2012-01-01

    We investigate the learnability of certain subclasses of tree adjoining grammars (TAGs). TAGs are based on two tree-tree operations, and generate structures known as derived trees. The corresponding strings form a mildly context-sensitive language. We prove that even very constrained subclasses of

  11. Principles Guiding Vocabulary Learning through Extensive Reading

    Science.gov (United States)

    Nation, Paul

    2015-01-01

    Extensive reading is one of a range of activities that can be used in a language learning course. Ideally, the choice of activities to go into a course should be guided by principles which are well supported by research. Similarly, the way each of those activities is used should be guided by well-justified principles. In this article, we look at…

  12. Relativistic classical strings. II

    International Nuclear Information System (INIS)

    Galvao, C.A.P.

    1985-01-01

    The interactions of strings with electromagnetic and gravitational fields are extensively discussed. Some concepts of differential geometry are reviewed. Strings in Kaluza-Klein manifolds are studied. (L.C.) [pt

  13. Associative Mechanisms Allow for Social Learning and Cultural Transmission of String Pulling in an Insect.

    Science.gov (United States)

    Alem, Sylvain; Perry, Clint J; Zhu, Xingfu; Loukola, Olli J; Ingraham, Thomas; Søvik, Eirik; Chittka, Lars

    2016-10-01

    Social insects make elaborate use of simple mechanisms to achieve seemingly complex behavior and may thus provide a unique resource to discover the basic cognitive elements required for culture, i.e., group-specific behaviors that spread from "innovators" to others in the group via social learning. We first explored whether bumblebees can learn a nonnatural object manipulation task by using string pulling to access a reward that was presented out of reach. Only a small minority "innovated" and solved the task spontaneously, but most bees were able to learn to pull a string when trained in a stepwise manner. In addition, naïve bees learnt the task by observing a trained demonstrator from a distance. Learning the behavior relied on a combination of simple associative mechanisms and trial-and-error learning and did not require "insight": naïve bees failed a "coiled-string experiment," in which they did not receive instant visual feedback of the target moving closer when tugging on the string. In cultural diffusion experiments, the skill spread rapidly from a single knowledgeable individual to the majority of a colony's foragers. We observed that there were several sequential sets ("generations") of learners, so that previously naïve observers could first acquire the technique by interacting with skilled individuals and, subsequently, themselves become demonstrators for the next "generation" of learners, so that the longevity of the skill in the population could outlast the lives of informed foragers. This suggests that, so long as animals have a basic toolkit of associative and motor learning processes, the key ingredients for the cultural spread of unusual skills are already in place and do not require sophisticated cognition.

  14. Dual-modality impairment of implicit learning of letter-strings versus color-patterns in patients with schizophrenia

    OpenAIRE

    Chiu, Ming-Jang; Liu, Kristina; Hsieh, Ming H; Hwu, Hai-Gwo

    2005-01-01

    Abstract Background Implicit learning was reported to be intact in schizophrenia using artificial grammar learning. However, emerging evidence indicates that artificial grammar learning is not a unitary process. The authors used dual coding stimuli and schizophrenia clinical symptom dimensions to re-evaluate the effect of schizophrenia on various components of artificial grammar learning. Methods Letter string and color pattern artificial grammar learning performances were compared between 63...

  15. Teaching Strings.

    Science.gov (United States)

    New York State Education Dept., Albany. Bureau of Secondary Curriculum Development.

    Intended primarily for use by instrumental music teachers who do not have a major concentration in strings, this guide provides pertinent basic resources, materials, teaching--learning expectation, and a general overall guide to achievement levels at various stages of development. Discussions are presented of Choosing the Proper Method Book,…

  16. The Nature of Organizational Learning in a State Extension Organization

    Science.gov (United States)

    Leuci, Mary Simon

    2012-01-01

    Our complex and rapidly changing world demands a more nimble, responsive, and flexible Extension organization. The findings from a study involving interviews across a state Cooperative Extension Service paint a picture of organizational learning in Extension. Four key dimensions of learning surfaced. Of particular importance are the application of…

  17. Adaptive Learning in Extensive Form Games and Sequential Equilibrium

    DEFF Research Database (Denmark)

    Groes, Ebbe; Jacobsen, Hans Jørgen; Sloth, Birgitte

    1999-01-01

    This paper studies adaptive learning in extensive form games and provides conditions for convergence points of adaptive learning to be sequential equilibria. Precisely, we present a set of conditions on learning sequences such that an assessment is a sequential equilibrium if and only if there is......This paper studies adaptive learning in extensive form games and provides conditions for convergence points of adaptive learning to be sequential equilibria. Precisely, we present a set of conditions on learning sequences such that an assessment is a sequential equilibrium if and only...

  18. Hybrid Teaching in Extension: Learning at the Crossroads

    Science.gov (United States)

    Hino, Jeff; Kahn, Cub

    2016-01-01

    Extension clients' learning preferences are changing, with many increasingly going online for educational content. In response, Oregon State University Extension pilot tested a training program for Extension educators to explore hybrid teaching--a methodology that could provide more flexible access to a wider audience. Hybrid teaching offers a…

  19. Strings draw theorists together

    International Nuclear Information System (INIS)

    Green, Michael

    2000-01-01

    has been learned about the non-perturbative extension of string theory now known as ''M theory'' and this has shed light on many previously mysterious aspects of quantum field theory. The range of new and potentially important developments is indeed impressive. One example is the accumulation of results on the role of ''noncommutative geometry'' in string theory. Another major theme of the meeting was the new ideas on how string theory may describe observed physics, such as the forces and particles in nature and their properties. The recent work by Lisa Randall of Princeton University and Raman Sundrum of Boston University is a variant of the ''brane world'' idea that has come to the fore over the past couple of years. According to this idea, which was reviewed by Randall at the conference, our four-dimensional universe can be thought of as a membrane (known as a three-brane) that is embedded inside a higher-dimensional universe. The number of higher dimensions is predicted by the structure of string theory. The possible consequences of this are striking. For example, in such a universe the fundamental energy scale of the theory may be much smaller than the Planck energy of 10 19 GeV. Indeed, the scale could be so small that it will be accessible to direct experimental observation using the next generation of accelerators, such as the Large Hadron Collider that is currently under construction at CERN. This theme was further developed by Steven Hawking, who conjectured on how such a universe might have evolved from the initial quantum state that preceded the big bang. One of the most exciting developments over the past few years has been in understanding how so-called Yang-Mills gauge theories - the bread and butter of the Standard Model of particle physics - are related to quantum gravity by string theory. Particularly important is the so-called ''Maldacena correspondence'', first developed by Juan Maldacena of Harvard University. This correspondence gives an explicit

  20. Extension and Higher Education Service-Learning: Toward a Community Development Service-Learning Model

    Science.gov (United States)

    Stoecker, Randy

    2014-01-01

    This article explores how on-the-ground Extension educators interface with higher education service-learning. Most service-learning in Extension has focused on precollege youth and 4-H. When we look at higher education service-learning and Extension in Wisconsin, we see that there is not as much connection as might be expected. County-based…

  1. Using Non-Extension Volunteering as an Experiential Learning Activity for Extension Professionals

    Science.gov (United States)

    Andrews, Kevin B.; Lockett, Landry L.

    2013-01-01

    Extension professionals can gain much-needed competencies in volunteer administration through experiential learning by participating in volunteer activities. Experiential learning is a means of behavior change that allows the individual learner to reflect on, abstract, and apply their experiences to new situations. This article expands on…

  2. String test

    Science.gov (United States)

    Duodenal parasites test; Giardia - string test ... To have this test, you swallow a string with a weighted gelatin capsule on the end. The string is pulled out 4 hours later. Any bile , blood, or mucus attached to ...

  3. String theory for dummies

    CERN Document Server

    Zimmerman Jones, Andrew

    2010-01-01

    Making Everything Easier!. String Theory for Dummies. Learn:. The basic concepts of this controversial theory;. How string theory builds on physics concepts;. The different viewpoints in the field;. String theory's physical implications. Andrew Zimmerman Jones. Physics Guide, About.com. with Daniel Robbins, PhD in Physics. Your plain-English guide to this complex scientific theory. String theory is one of the most complicated sciences being explored today. Not to worry though! This informative guide clearly explains the basics of this hot topic, discusses the theory's hypotheses and prediction

  4. Learning PrimeFaces extensions development

    CERN Document Server

    Jonna, Sudheer

    2014-01-01

    This book provides a step by step approach that explains the most important extension components and their features. All the major features are explained by using the JobHub application with supporting screenshots.If you are an intermediate to advanced level user (or developer) who already has a basic working knowledge of PrimeFaces, then this book is for you.The only thing you need to know is Java Server Faces(JSF).

  5. Learning investment indicators through data extension

    Science.gov (United States)

    Dvořák, Marek

    2017-07-01

    Stock prices in the form of time series were analysed using single and multivariate statistical methods. After simple data preprocessing in the form of logarithmic differences, we augmented this single variate time series to a multivariate representation. This method makes use of sliding windows to calculate several dozen of new variables using simple statistic tools like first and second moments as well as more complicated statistic, like auto-regression coefficients and residual analysis, followed by an optional quadratic transformation that was further used for data extension. These were used as a explanatory variables in a regularized logistic LASSO regression which tried to estimate Buy-Sell Index (BSI) from real stock market data.

  6. Fearless Improvisation: A Pilot Study to Analyze String Students' Confidence, Anxiety, and Attitude toward Learning Improvisation

    Science.gov (United States)

    Alexander, Michael L.

    2012-01-01

    The purpose of this study was to investigate the confidence, anxiety, and attitude of novice string student improvisers. A form of the Fennema-Sherman Mathematics Attitudes Scales, as modified for improvisation by Wehr-Flowers, was given to middle school and high school string students (N = 121) after their participation in a 4-month improvisation…

  7. Dual-modality impairment of implicit learning of letter-strings versus color-patterns in patients with schizophrenia

    Directory of Open Access Journals (Sweden)

    Hwu Hai-Gwo

    2005-12-01

    Full Text Available Abstract Background Implicit learning was reported to be intact in schizophrenia using artificial grammar learning. However, emerging evidence indicates that artificial grammar learning is not a unitary process. The authors used dual coding stimuli and schizophrenia clinical symptom dimensions to re-evaluate the effect of schizophrenia on various components of artificial grammar learning. Methods Letter string and color pattern artificial grammar learning performances were compared between 63 schizophrenic patients and 27 comparison subjects. Four symptom dimensions derived from a Chinese Positive and Negative Symptom Scale ratings were correlated with patients' artificial grammar implicit learning performances along the two stimulus dimensions. Patients' explicit memory performances were assessed by verbal paired associates and visual reproduction subtests of the Wechsler Memory Scales Revised Version to provide a contrast to their implicit memory function. Results Schizophrenia severely hindered color pattern artificial grammar learning while the disease affected lexical string artificial grammar learning to a lesser degree after correcting the influences from age, education and the performance of explicit memory function of both verbal and visual modalities. Both learning performances correlated significantly with the severity of patients' schizophrenic clinical symptom dimensions that reflect poor abstract thinking, disorganized thinking, and stereotyped thinking. Conclusion The results of this study suggested that schizophrenia affects various mechanisms of artificial grammar learning differently. Implicit learning, knowledge acquisition in the absence of conscious awareness, is not entirely intact in patients with schizophrenia. Schizophrenia affects implicit learning through an impairment of the ability of making abstractions from rules and at least in part decreasing the capacity for perceptual learning.

  8. Subsurface drill string

    Science.gov (United States)

    Casper, William L [Rigby, ID; Clark, Don T [Idaho Falls, ID; Grover, Blair K [Idaho Falls, ID; Mathewson, Rodney O [Idaho Falls, ID; Seymour, Craig A [Idaho Falls, ID

    2008-10-07

    A drill string comprises a first drill string member having a male end; and a second drill string member having a female end configured to be joined to the male end of the first drill string member, the male end having a threaded portion including generally square threads, the male end having a non-threaded extension portion coaxial with the threaded portion, and the male end further having a bearing surface, the female end having a female threaded portion having corresponding female threads, the female end having a non-threaded extension portion coaxial with the female threaded portion, and the female end having a bearing surface. Installation methods, including methods of installing instrumented probes are also provided.

  9. String theory

    International Nuclear Information System (INIS)

    Chan Hongmo.

    1987-10-01

    The paper traces the development of the String Theory, and was presented at Professor Sir Rudolf Peierls' 80sup(th) Birthday Symposium. The String theory is discussed with respect to the interaction of strings, the inclusion of both gauge theory and gravitation, inconsistencies in the theory, and the role of space-time. The physical principles underlying string theory are also outlined. (U.K.)

  10. Hyperbolic strings

    International Nuclear Information System (INIS)

    Popov, A.D.

    1991-01-01

    We introduce hyperbolic strings as closed bosonic strings with the target space R d-1,1 xT q+1,1 which has an additional time-like dimension in the internal space. The Fock spaces of the q-parametric family of standard bosonic, fermionic and heterotic strings with the target spaces of dimension n≤d+q are shown to be embedded into the Fock space of hyperbolic strings. The condition of the absence of anomaly fixes d and q for all three types of strings written in a bosonized form. (orig.)

  11. The effectiveness of extensive reading on EFL learners’ vocabulary learning: incidental versus intentional learning

    OpenAIRE

    Teng, Feng

    2015-01-01

    Forty-six students majoring in business English volunteered to take part in an extensive reading program. The learners were divided into two groups: EG, the experimental group, received instruction in methods of extensive reading plus explicit output-pushed activities, and CG, the control group, received instruction in methods of extensive reading only. This study measured the effects of extensive reading on EFL vocabulary learning, through the effects of the two different instruction methods...

  12. Introduction to strings and superstrings

    International Nuclear Information System (INIS)

    Traubenberg, M.R. de.

    1988-01-01

    We discuss the main features on the formulation of string theory that, in a primitive level, describe the hadronic phenomenon of duality. We also study an extension of the models of closed and strings with spin. Then, by using supersymmetry, it is formulated the theory of superstrings and heterotic strings with the aim of unify the fundamental interactions and matter. (M.W.O.) [pt

  13. String theory compactifications

    CERN Document Server

    Graña, Mariana

    2017-01-01

    The lectures in this book provide graduate students and non-specialist researchers with a concise introduction to the concepts and formalism required to reduce the ten-dimensional string theories to the observable four-dimensional space-time - a procedure called string compactification. The text starts with a very brief introduction to string theory, first working out its massless spectrum and showing how the condition on the number of dimensions arises. It then dwells on the different possible internal manifolds, from the simplest to the most relevant phenomenologically, thereby showing that the most elegant description is through an extension of ordinary Riemannian geometry termed generalized geometry, which was first introduced by Hitchin. Last but not least, the authors review open problems in string phenomenology, such as the embedding of the Standard Model and obtaining de Sitter solutions.

  14. Bowed Strings

    Science.gov (United States)

    Rossing, Thomas D.; Hanson, Roger J.

    In the next eight chapters, we consider some aspects of the science of bowed string instruments, old and new. In this chapter, we present a brief discussion of bowed strings, a subject that will be developed much more thoroughly in Chap. 16. Chapters 13-15 discuss the violin, the cello, and the double bass. Chapter 17 discusses viols and other historic string instruments, and Chap. 18 discusses the Hutchins-Schelleng violin octet.

  15. Public Libraries and Cooperative Extension as Community Partners for Lifelong Learning and Learning Cities

    Science.gov (United States)

    Peich, Alysia; Fletcher, Cynthia Needles

    2015-01-01

    This chapter examines the parallel histories and visions of public libraries and land-grant universities' Cooperative Extension in providing lifelong learning opportunities; it illustrates how partnerships between organizations can enhance the vibrancy of adult education in the context of learning cities.

  16. Bosonic strings

    CERN Document Server

    Jost, Jürgen

    2007-01-01

    This book presents a mathematical treatment of Bosonic string theory from the point of view of global geometry. As motivation, Jost presents the theory of point particles and Feynman path integrals. He provides detailed background material, including the geometry of Teichmüller space, the conformal and complex geometry of Riemann surfaces, and the subtleties of boundary regularity questions. The high point is the description of the partition function for Bosonic strings as a finite-dimensional integral over a moduli space of Riemann surfaces. Jost concludes with some topics related to open and closed strings and D-branes. Bosonic Strings is suitable for graduate students and researchers interested in the mathematics underlying string theory.

  17. Cosmological Quantum String Vacua and String-String Duality

    OpenAIRE

    Rey, Soo-Jong

    1996-01-01

    Implications of string-string dualities to cosmological string vacua are discussed. Cosmological vacua of classical string theories comprise of disjoint classses mapped one another by scale-factor T-duality. Each classes are, however, afflicted with initial/final cosmological singularities. It is argued that quantum string theories and string-string dualities dramatically resolve these cosmological singularities out so that disjoint classical cosmological vacua are continuously connected in a...

  18. Strings for quantumchromodynamics

    International Nuclear Information System (INIS)

    Schomerus, V.

    2007-04-01

    During the last decade, intriguing dualities between gauge and string theory have been found and explored. they provide a novel window on strongly couplde gauge physics, including QCD-like models. Based on a short historical review of modern string theory, we explain how so-called AdS/CFT dualities emerged at the end of the 1990s. Some of their concrete implications and remarkable recent progress are then illustrated for the simplest example, namely the multicolor limit of N=4 SYM theory in four dimensions. We end with a few comments on existing extensions to more realistic models and applications, in particular to the sQGP. This text is meant as a non-technical introduction to gauge/string dualities for (particle) physicists. (orig.)

  19. Magnetic strings

    International Nuclear Information System (INIS)

    Chaves, Max

    2006-01-01

    The conception of the magnetic string is presented as an infinitely thin bundle of magnetic flux lines. The magnetic strings are surrounded by a film of current that rotates around them, and are a solution of Maxwell's equations. The magnetic potential contains a line singularity, and its stability can be established topologically. A few comments are added on the possibility that they may exist at a cosmological scale as relics of the Big Bang. (author) [es

  20. Lattice strings

    International Nuclear Information System (INIS)

    Thorn, C.B.

    1988-01-01

    The possibility of studying non-perturbative effects in string theory using a world sheet lattice is discussed. The light-cone lattice string model of Giles and Thorn is studied numerically to assess the accuracy of ''coarse lattice'' approximations. For free strings a 5 by 15 lattice seems sufficient to obtain better than 10% accuracy for the bosonic string tachyon mass squared. In addition a crude lattice model simulating string like interactions is studied to find out how easily a coarse lattice calculation can pick out effects such as bound states which would qualitatively alter the spectrum of the free theory. The role of the critical dimension in obtaining a finite continuum limit is discussed. Instead of the ''gaussian'' lattice model one could use one of the vertex models, whose continuum limit is the same as a gaussian model on a torus of any radius. Indeed, any critical 2 dimensional statistical system will have a stringy continuum limit in the absence of string interactions. 8 refs., 1 fig. , 9 tabs

  1. Singleton strings

    Energy Technology Data Exchange (ETDEWEB)

    Engquist, J. [Institute for Theoretical Physics and Spinoza Institute, Utrecht University (Netherlands); Sundell, P. [INFN, Pisa (Italy); Scuola Normale Superiore, Pisa (Italy); Tamassia, L. [Instituut voor Theoretische Fysica, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium)

    2007-05-15

    The group theoretical structure underlying physics in anti de Sitter (AdS) spacetime is intrinsically different with respect to the flat case, due to the presence of special ultra-short representations, named singletons, that do not admit a flat space limit. The purpose of this collaboration is to exploit this feature in the study of string and brane dynamics in AdS spacetime, in particular while trying to establish a connection between String Theory in AdS backgrounds (in the tensionless limit) and Higher-Spin Gauge Theory. (orig.)

  2. Agriflection: A Learning Model for Agricultural Extension in South Africa

    Science.gov (United States)

    Worth, S. H.

    2006-01-01

    Prosperity--continuous and sustainable wealth creation--is an elusive goal in South African smallholder agriculture. This paper suggests that agricultural extension can facilitate realising this objective if an appropriate approach to extension can be developed. To develop such an approach requires that the definition of extension and the…

  3. String phenomenology

    CERN Document Server

    Ibáñez, Luis E

    2015-01-01

    This chapter reviews a number of topics in the field of string phenomenology, focusing on orientifold/F-theory models yielding semirealistic low-energy physics. The emphasis is on the extraction of the low-energy effective action and possible tests of specific models at the LHC.

  4. Video Analysis of a Plucked String: An Example of Problem-based Learning

    Science.gov (United States)

    Wentworth, Christopher D.; Buse, Eric

    2009-11-01

    Problem-based learning is a teaching methodology that grounds learning within the context of solving a real problem. Typically the problem initiates learning of concepts rather than simply being an application of the concept, and students take the lead in identifying what must be developed to solve the problem. Problem-based learning in upper-level physics courses can be challenging, because of the time and financial requirements necessary to generate real data. Here, we present a problem that motivates learning about partial differential equations and their solution in a mathematical methods for physics course. Students study a plucked elastic cord using high speed digital video. After creating video clips of the cord motion under different tensions they are asked to create a mathematical model. Ultimately, students develop and solve a model that includes damping effects that are clearly visible in the videos. The digital video files used in this project are available on the web at http://physics.doane.edu .

  5. Networked Learning for Agricultural Extension: A Framework for Analysis and Two Cases

    Science.gov (United States)

    Kelly, Nick; Bennett, John McLean; Starasts, Ann

    2017-01-01

    Purpose: This paper presents economic and pedagogical motivations for adopting information and communications technology (ICT)- mediated learning networks in agricultural education and extension. It proposes a framework for networked learning in agricultural extension and contributes a theoretical and case-based rationale for adopting the…

  6. Fractional bosonic strings

    Science.gov (United States)

    Diaz, Victor Alfonzo; Giusti, Andrea

    2018-03-01

    The aim of this paper is to present a simple generalization of bosonic string theory in the framework of the theory of fractional variational problems. Specifically, we present a fractional extension of the Polyakov action, for which we compute the general form of the equations of motion and discuss the connection between the new fractional action and a generalization the Nambu-Goto action. Consequently, we analyze the symmetries of the modified Polyakov action and try to fix the gauge, following the classical procedures. Then we solve the equations of motion in a simplified setting. Finally, we present a Hamiltonian description of the classical fractional bosonic string and introduce the fractional light-cone gauge. It is important to remark that, throughout the whole paper, we thoroughly discuss how to recover the known results as an "integer" limit of the presented model.

  7. The "Magic" String

    Science.gov (United States)

    Hoover, Todd F.

    2010-01-01

    The "Magic" String is a discrepant event that includes a canister with what appears to be the end of two strings protruding from opposite sides of it. Due to the way the strings are attached inside the canister, it appears as if the strings can magically switch the way they are connected. When one string end is pulled, the observer's expectation…

  8. Sigma models and renormalization of string loops

    International Nuclear Information System (INIS)

    Tseytlin, A.A.

    1989-05-01

    An extension of the ''σ-model β-functions - string equations of motion'' correspondence to the string loop level is discussed. Special emphasis is made on how the renormalization group acts in string loops and, in particular, on the renormalizability property of the generating functional Z-circumflex for string amplitudes (related to the σ model partition function integrated over moduli). Renormalization of Z-circumflex at one and two loop order is analyzed in some detail. We also discuss an approach to renormalization based on operators of insertion of topological fixtures. (author). 70 refs

  9. String Gas Cosmology

    OpenAIRE

    Brandenberger, Robert H.

    2008-01-01

    String gas cosmology is a string theory-based approach to early universe cosmology which is based on making use of robust features of string theory such as the existence of new states and new symmetries. A first goal of string gas cosmology is to understand how string theory can effect the earliest moments of cosmology before the effective field theory approach which underlies standard and inflationary cosmology becomes valid. String gas cosmology may also provide an alternative to the curren...

  10. Determinants of E-learning Acceptance among Agricultural Extension Agents in Malaysia: A Conceptual Framework

    OpenAIRE

    Mangir, Safaie; Othman, Zakirah; Udin, Zulkifli Mohamed

    2016-01-01

    The objective of this paper is to develop a framework on e-learning acceptance among agricultural extension agents in Malaysian agricultural sector. E-learning is viewed as a solution in response to the increasing need for learning and training. This paper will review past literatures for the relevant factors that influence behavioral intention for e-learning acceptance as well as the relevant behavioral theories that provide the foundation for developing research framework to illustrate the ...

  11. Closed string field theory

    International Nuclear Information System (INIS)

    Strominger, A.

    1987-01-01

    A gauge invariant cubic action describing bosonic closed string field theory is constructed. The gauge symmetries include local spacetime diffeomorphisms. The conventional closed string spectrum and trilinear couplings are reproduced after spontaneous symmetry breaking. The action S is constructed from the usual ''open string'' field of ghost number minus one half. It is given by the associator of the string field product which is non-vanishing because of associativity anomalies. S does not describe open string propagation because open string states associate and can thereby be shifted away. A field theory of closed and open strings can be obtained by adding to S the cubic open string action. (orig.)

  12. Fingerprints in Compressed Strings

    DEFF Research Database (Denmark)

    Bille, Philip; Cording, Patrick Hagge; Gørtz, Inge Li

    2013-01-01

    The Karp-Rabin fingerprint of a string is a type of hash value that due to its strong properties has been used in many string algorithms. In this paper we show how to construct a data structure for a string S of size N compressed by a context-free grammar of size n that answers fingerprint queries....... That is, given indices i and j, the answer to a query is the fingerprint of the substring S[i,j]. We present the first O(n) space data structures that answer fingerprint queries without decompressing any characters. For Straight Line Programs (SLP) we get O(logN) query time, and for Linear SLPs (an SLP...... derivative that captures LZ78 compression and its variations) we get O(loglogN) query time. Hence, our data structures has the same time and space complexity as for random access in SLPs. We utilize the fingerprint data structures to solve the longest common extension problem in query time O(logNlogℓ) and O...

  13. From cosmic string to superconducting string

    CERN Document Server

    Kim, H C; Lee, B K

    1999-01-01

    We consider the dynamical symmetry breaking of a chirally-invariant Nambu-Jona-Lasinio model in the background gravity of a local cosmic string. By analyzing the one-loop effective action, we show how a cosmic string at a very high energy scale forms a global superconducting string to the spontaneous chiral symmetry breaking at a low energy.

  14. Vocabulary Learning through Extensive Reading: A Case Study

    Science.gov (United States)

    Senoo, Yasuko; Yonemoto, Kazuhiro

    2014-01-01

    The role and importance of reading in second language vocabulary learning have been discussed by many researchers because of the richness and variety of vocabulary in written texts compared to oral discourse (Horst, 2005; Nation, 2001). However, despite the recent increase of studies in this field, there are very few studies focusing on…

  15. The role of learning networks in agricultural extension service delivery

    African Journals Online (AJOL)

    This paper seeks to present the findings of a study based on learning networks conducted in nine provinces of South Africa during 2013. The aim of the study was to establish to what extent this tool is known or used in the provinces of South Africa. The information was important in order to assist decision makers in future ...

  16. Developing Collective Learning Extension for Rapidly Evolving Information System Courses

    Science.gov (United States)

    Agarwal, Nitin; Ahmed, Faysal

    2017-01-01

    Due to rapidly evolving Information System (IS) technologies, instructors find themselves stuck in the constant game of catching up. On the same hand students find their skills obsolete almost as soon as they graduate. As part of IS curriculum and education, we need to emphasize more on teaching the students "how to learn" while keeping…

  17. Extensive Boiler Rehabilitation at TPP Bitola - Lessons Learned

    OpenAIRE

    Cingoski, Vlatko; Tanurkov, Dimitar; Papasterevski, Kosta

    2017-01-01

    Thermal Power Plant (TPP) Bitola is the largest lignite-based TPP in the Republic of Macedonia with three units put into operation in 1982, 1984 and 1988, respectively. All three units have already operated more than 200.000 hours each, therefore they are far beyond their normal life expectancy. Thus, a large-scale rehabilitation program including extensive boiler rehabilitation of all three units, lignite supply chain modernization, steam turbines, generators and control system modernizat...

  18. What do we learn about hadronic interactions at ultrahigh energies from extensive air shower observations?

    International Nuclear Information System (INIS)

    Rebel, H.

    2002-01-01

    The interpretation of extensive air shower (EAS) observations needs a sufficiently accurate knowledge of the interactions driving the cascade development in the atmosphere. While the electromagnetic and weak interaction parts do not provide principal problems, the hadronic interaction is a subject of uncertainties and debates, especially in the ultrahigh energy region extending the energy limits of man made accelerators and experimental knowledge from collider experiments. Since the EAS development is dominantly governed by soft processes, which are presently not accessible to a perturbative QCD treatment, one has to rely on QCD inspired phenomenological interaction models, in particular on string-models based on the Gribov-Regge theory like QGSJET, VENUS and SYBILL. Recent results of the EAS experiments KASCADE are scrutinized in terms of such models used as generators in the Monte Carlo EAS simulation code CORSIKA. (author)

  19. Evidence for string substructure

    International Nuclear Information System (INIS)

    Bergman, O.

    1996-06-01

    The author argues that the behavior of string theory at high temperature and high longitudinal boosts, combined with the emergence of p-branes as necessary ingredients in various string dualities, point to a possible reformulation of strings, as well as p-branes, as composites of bits. He reviews the string-bit models, and suggests generalizations to incorporate p-branes

  20. String Resonances at Hadron Colliders

    CERN Document Server

    Anchordoqui, Luis A; Dai, De-Chang; Feng, Wan-Zhe; Goldberg, Haim; Huang, Xing; Lust, Dieter; Stojkovic, Dejan; Taylor, Tomasz R

    2014-01-01

    [Abridged] We consider extensions of the standard model based on open strings ending on D-branes. Assuming that the fundamental string mass scale M_s is in the TeV range and that the theory is weakly coupled, we discuss possible signals of string physics at the upcoming HL-LHC run (3000 fb^{-1}) with \\sqrt{s} = 14 TeV, and at potential future pp colliders, HE-LHC and VLHC, operating at \\sqrt{s} = 33 and 100 TeV, respectively. In such D-brane constructions, the dominant contributions to full-fledged string amplitudes for all the common QCD parton subprocesses leading to dijets and \\gamma + jet are completely independent of the details of compactification, and can be evaluated in a parameter-free manner. We make use of these amplitudes evaluated near the first (n=1) and second (n=2) resonant poles to determine the discovery potential for Regge excitations of the quark, the gluon, and the color singlet living on the QCD stack. We show that for string scales as large as 7.1 TeV (6.1 TeV), lowest massive Regge exc...

  1. String Theory Volume 1: An Introduction to the Bosonic String and Volume 2: Superstring Theory and Beyond

    Energy Technology Data Exchange (ETDEWEB)

    Carlip, S [Department of Physics, University of California, Davis, CA 95616 (United States)

    2006-10-21

    The early 1980s, when I first learned theory, were desperate times for graduate students. We searched frantically for coherent introductions, passing tattered copies of review articles around like samizdat, struggling over obscure references to ancient models of strong interactions, and flocking to lectures-not least those by Joe Polchinski-that promised to really explain what was going on. If only this book had been around, it would have saved much grief. Volume I, The Bosonic String, offers a clear and well organized introduction to bosonic string theory. Topics range from the 'classical' (spectra, vertex operators, consistency conditions, etc.) to the 'modern' (D-branes first appear in an exercise at the end of chapter 1, noncommutative geometry shows up in chapter 8). Polchinski does not hesitate to discuss sophisticated matters-path integral measures, BRST symmetries, etc.-but his approach is pedagogical, and his writing is lucid, if sometimes a bit terse. Chapters end with problems that are sometimes difficult but never impossible. A very useful annotated bibliography directs readers to resources for further study, and a nearly 30-page glossary provides short but clear definitions of key terms. There is much here that will appeal to relativists. Polchinski uses the covariant Polyakov path integral approach to quantization from early on; he clearly distinguishes Weyl invariance from conformal invariance; he is appropriately careful about using complex coordinates on topologically nontrivial manifolds; he keeps the string world sheet metric explicit at the start instead of immediately hiding it by a gauge choice. Volume II includes an elegant introduction to anticommuting coordinates and superconformal transformations. A few conventions may cause confusion-%, Polchinski's stress-energy tensor, for instance, differs from the standard general relativistic definition by a factor of -2{pi}, and while this is briefly mentioned in the text

  2. Validating the virtual string task with the gap test.

    Science.gov (United States)

    Brzykcy, Stephen J; Wasserman, Edward A; Nagasaka, Yasuo; Perez-Acevedo, Sacha

    2014-11-01

    Relational concepts-such as connectedness-may be easy for human adults to appreciate; but, obtaining evidence of other species' understanding of connectedness has been challenging. One key test of connectedness involves an organism's responding to variants of the string task. Using a virtual string task, we gave pigeons a pair of strings from which to choose: one connected to a full dish of food and a second disconnected from another full dish of food. Our pigeons did not at first choose the connected string under conditions of non-differential reinforcement; later, the birds rapidly learned to choose the connected string under conditions of differential reinforcement. Our results replicate prior findings with real strings and food dishes, thereby demonstrating that pigeons can appreciate the connectedness between a string tether and a dish of food, and attesting to the utility and fidelity of the virtual string task.

  3. The heterotic string

    International Nuclear Information System (INIS)

    Gross, D.J.

    1986-01-01

    Traditional string theories, either bosonic or supersymmetric, came in two varieties, closed string theories and open string theories. Closed string are neutral objects which describe at low energies gravity or supergravity. Open strings have geometrically invariant ends to which charge can be attached, thereby obtaining, in addition to gravity, Yang-Mills gauge interactions. Recently a new kind of string theory was discovered--the heterotic string, which is a chiral hybrid of the closed superstring and the closed bosonic string, and which produces by an internal dynamical mechanism gauge interactions of a totally specified kind. Although this theory is found in an attempt to produce a superstring theory which would yield a low energy E/sub 8/xE/sub 8/ supersymmetric, anomaly free, gauge theory, as suggested by the anomaly cancellation mechanism of Green and Schwarz, it fits naturally into the general framework of consistent string theories

  4. Closed String Amplitudes from Gauge Fixed String Field Theory

    OpenAIRE

    Drukker, Nadav

    2002-01-01

    Closed string diagrams are derived from cubic open string field theory using a gauge fixed kinetic operator. The basic idea is to use a string propagator that does not generate a boundary to the world sheet. Using this propagator and the closed string vertex, the moduli space of closed string surfaces is covered, so closed string scattering amplitudes should be reproduced. This kinetic operator could be a gauge fixed form of the string field theory action around the closed string vacuum.

  5. A non-perturbative approach to strings

    International Nuclear Information System (INIS)

    Orland, P.

    1986-03-01

    After briefly reviewing the theory of strings in the light-cone gauge, a lattice regularized path integral for the amplitudes is discussed. The emphasis is put on a toy string model; the U(N) Veneziano model in the limit as N->infinite with g 0 2 N fixed. The lattice methods of Giles and Thorn are used extensively, but are found to require modification beyond perturbation theory. The twenty-six-dimensional toy string model is recast as a two-dimensional spin system. (orig.)

  6. std::string Append

    Science.gov (United States)

    2015-10-01

    UNCLASSIFIED AD-E403 689 Technical Report ARWSE-TR-14026 STD ::STRING APPEND Tom Nealis...DATES COVERED (From – To) 4. TITLE AND SUBTITLE STD ::STRING APPEND 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6...two or more strings together while developing a C++ application is a very common task. For std ::strings, there are two primary ways to achieve the

  7. Strings in the Sun?

    International Nuclear Information System (INIS)

    Chudnovsky, E.; Vilenkin, A.

    1988-01-01

    If light superconducting strings were formed in the early Universe, then it is very likely that now they exist in abundance in the interstellar plasma and in stars. The dynamics of such strings can be dominated by friction, so that they are ''frozen'' into the plasma. Turbulence of the plasma twists and stretches the strings, forming a stochastic string network. Such networks must generate particles and magnetic fields, and may play an important role in the physics of stars and of the Galaxy

  8. StringForce

    DEFF Research Database (Denmark)

    Barendregt, Wolmet; Börjesson, Peter; Eriksson, Eva

    2017-01-01

    In this paper, we present the forced collaborative interaction game StringForce. StringForce is developed for a special education context to support training of collaboration skills, using readily available technologies and avoiding the creation of a "mobile bubble". In order to play StringForce ...

  9. Dynamics of Carroll strings

    Energy Technology Data Exchange (ETDEWEB)

    Cardona, Biel [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Gomis, Joaquim [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain); Department of Physics, Faculty of Science, Chulalongkorn University,Bangkok 10330 (Thailand); Pons, Josep M. [Departament d’Estructura i Constituents de la Matèriaand Institut de Ciències del Cosmos (ICCUB) Facultat de Física, Universitat de Barcelona,Diagonal 647, E-08028 Barcelona, Catalonia (Spain)

    2016-07-11

    We construct the canonical action of a Carroll string doing the Carroll limit of a canonical relativistic string. We also study the Killing symmetries of the Carroll string, which close under an infinite dimensional algebra. The tensionless limit and the Carroll p-brane action are also discussed.

  10. String Theory Volume 1: An Introduction to the Bosonic String and Volume 2: Superstring Theory and Beyond

    International Nuclear Information System (INIS)

    Carlip, S

    2006-01-01

    The early 1980s, when I first learned theory, were desperate times for graduate students. We searched frantically for coherent introductions, passing tattered copies of review articles around like samizdat, struggling over obscure references to ancient models of strong interactions, and flocking to lectures-not least those by Joe Polchinski-that promised to really explain what was going on. If only this book had been around, it would have saved much grief. Volume I, The Bosonic String, offers a clear and well organized introduction to bosonic string theory. Topics range from the 'classical' (spectra, vertex operators, consistency conditions, etc.) to the 'modern' (D-branes first appear in an exercise at the end of chapter 1, noncommutative geometry shows up in chapter 8). Polchinski does not hesitate to discuss sophisticated matters-path integral measures, BRST symmetries, etc.-but his approach is pedagogical, and his writing is lucid, if sometimes a bit terse. Chapters end with problems that are sometimes difficult but never impossible. A very useful annotated bibliography directs readers to resources for further study, and a nearly 30-page glossary provides short but clear definitions of key terms. There is much here that will appeal to relativists. Polchinski uses the covariant Polyakov path integral approach to quantization from early on; he clearly distinguishes Weyl invariance from conformal invariance; he is appropriately careful about using complex coordinates on topologically nontrivial manifolds; he keeps the string world sheet metric explicit at the start instead of immediately hiding it by a gauge choice. Volume II includes an elegant introduction to anticommuting coordinates and superconformal transformations. A few conventions may cause confusion-%, Polchinski's stress-energy tensor, for instance, differs from the standard general relativistic definition by a factor of -2π, and while this is briefly mentioned in the text, it could easily be missed

  11. Gravity and strings

    CERN Document Server

    Ortín, Tomás

    2015-01-01

    Self-contained and comprehensive, this definitive new edition of Gravity and Strings is a unique resource for graduate students and researchers in theoretical physics. From basic differential geometry through to the construction and study of black-hole and black-brane solutions in quantum gravity - via all the intermediate stages - this book provides a complete overview of the intersection of gravity, supergravity, and superstrings. Now fully revised, this second edition covers an extensive array of topics, including new material on non-linear electric-magnetic duality, the electric-tensor formalism, matter-coupled supergravity, supersymmetric solutions, the geometries of scalar manifolds appearing in 4- and 5-dimensional supergravities, and much more. Covering reviews of important solutions and numerous solution-generating techniques, and accompanied by an exhaustive index and bibliography, this is an exceptional reference work.

  12. Evaluation of Online Video Usage and Learning Satisfaction: An Extension of the Technology Acceptance Model

    Science.gov (United States)

    Nagy, Judit T.

    2018-01-01

    The aim of the study was to examine the determining factors of students' video usage and their learning satisfaction relating to the supplementary application of educational videos, accessible in a Moodle environment in a Business Mathematics Course. The research model is based on the extension of "Technology Acceptance Model" (TAM), in…

  13. The Effectiveness of Extensive versus Intensive Recasts for Learning L2 Grammar

    Science.gov (United States)

    Nassaji, Hossein

    2017-01-01

    This study investigated the effects of extensive versus intensive recasts. The focus was on the effect of feedback on learning English articles, which, as nonsalient target structures, have been shown to be difficult for many second language learners. Intensive recasts were operationalized as recasts provided on article errors only, while…

  14. The Knowledge Base as an Extension of Distance Learning Reference Service

    Science.gov (United States)

    Casey, Anne Marie

    2012-01-01

    This study explores knowledge bases as extension of reference services for distance learners. Through a survey and follow-up interviews with distance learning librarians, this paper discusses their interest in creating and maintaining a knowledge base as a resource for reference services to distance learners. It also investigates their perceptions…

  15. Performance on patterned string problems by common marmosets (Callithrix jacchus)

    Science.gov (United States)

    Gagne, Matthew; Levesque, Kathryn; Nutile, Lauren; Locurto, Charles

    2012-01-01

    This experiment examined the performance of common marmosets (Callithrix jacchus) on a series of patterned string problems to assess the marmosets’ understanding of means-ends relationships. One marmoset, Jet, was exposed to a series of problems that were ordered in terms of perceived difficulty during two testings that were separated by one year. In the second testing Jet received problems that had been used during the first testing along with three new problems. Each of the new problems was designed to be an exemplar of the type of problem that Jet had experienced difficulty with in the first testing. A second marmoset, Peaches, was tested on the same set of problems given to Jet in the second testing. Results indicated that the marmosets’ performance on these problems fell into three categories. In one category, some problems were solved without evidence of trial and error learning. In a second category, there were problems in which the marmosets responded at chance levels initially but evidenced improvement as a function of extended testing. In a third category, some problems appeared to be virtually unsolvable even with extended testing. Taken together, these results indicate that the marmosets were able to learn the means-ends connection between pulling a string and obtaining food. This learning was best characterized as a trial and error process for some problem forms, while for others there appeared to be rapid learning that did not require extensive practice. The instances of rapid learning may be the result of the application of a simple spatial proximity rule in which the marmosets chose the string that was closest to an imaginary line drawn between the marmoset and the reinforcer. PMID:22576582

  16. Minimal open strings

    International Nuclear Information System (INIS)

    Hosomichi, Kazuo

    2008-01-01

    We study FZZT-branes and open string amplitudes in (p, q) minimal string theory. We focus on the simplest boundary changing operators in two-matrix models, and identify the corresponding operators in worldsheet theory through the comparison of amplitudes. Along the way, we find a novel linear relation among FZZT boundary states in minimal string theory. We also show that the boundary ground ring is realized on physical open string operators in a very simple manner, and discuss its use for perturbative computation of higher open string amplitudes.

  17. Cosmic strings and inflation

    International Nuclear Information System (INIS)

    Vishniac, E.T.

    1987-01-01

    We examine the compatibility of inflation with the cosmic string theory for galaxy formation. There is a general conflict between having sufficient string tension to effect galaxy formation, and reheating after inflation to a high enough temperature that strings may form in a thermal phase transition. To escape this conflict, we propose a class of models where the inflation is coupled to the string-producing field. The strings are formed late in inflation as the inflaton rolls towards its zero-temperature value. A large subset of these models have a novel large-scale distribution of galaxies that is fractal, displays biasing without dynamics or feedback mechanisms, and contains voids. (orig.)

  18. Closed Strings From Nothing

    International Nuclear Information System (INIS)

    Lawrence, Albion

    2001-01-01

    We study the physics of open strings in bosonic and type II string theories in the presence of unstable D-branes. When the potential energy of the open string tachyon is at its minimum, Sen has argued that only closed strings remain in the perturbative spectrum. We explore the scenario of Yi and of Bergman, Hori and Yi, who argue that the open string degrees of freedom are strongly coupled and disappear through confinement. We discuss arguments using open string field theory and worldsheet boundary RG flows, which seem to indicate otherwise. We then describe a solitonic excitation of the open string tachyon and gauge field with the charge and tension of a fundamental closed string. This requires a double scaling limit where the tachyon is taken to its minimal value and the electric field is taken to its maximum value. The resulting flux tube has an unconstrained spatial profile; and for large fundamental string charge, it appears to have light, weakly coupled open strings living in the core. We argue that the flux tube acquires a size or order α' through sigma model and string coupling effects; and we argue that confinement effects make the light degrees of freedom heavy and strongly interacting

  19. Closed Strings From Nothing

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence, Albion

    2001-07-25

    We study the physics of open strings in bosonic and type II string theories in the presence of unstable D-branes. When the potential energy of the open string tachyon is at its minimum, Sen has argued that only closed strings remain in the perturbative spectrum. We explore the scenario of Yi and of Bergman, Hori and Yi, who argue that the open string degrees of freedom are strongly coupled and disappear through confinement. We discuss arguments using open string field theory and worldsheet boundary RG flows, which seem to indicate otherwise. We then describe a solitonic excitation of the open string tachyon and gauge field with the charge and tension of a fundamental closed string. This requires a double scaling limit where the tachyon is taken to its minimal value and the electric field is taken to its maximum value. The resulting flux tube has an unconstrained spatial profile; and for large fundamental string charge, it appears to have light, weakly coupled open strings living in the core. We argue that the flux tube acquires a size or order {alpha}' through sigma model and string coupling effects; and we argue that confinement effects make the light degrees of freedom heavy and strongly interacting.

  20. The arithmetic of strings

    International Nuclear Information System (INIS)

    Freund, P.G.O.

    1988-01-01

    According to the author nobody has succeeded as yet in extracting any new numbers from string theory. This paper discusses how if one cannot get new numbers from string theory, maybe one can get new strings out of number theory. Number theory is generally regarded as the purest form of mathematics. So how can it conceivably make contact with physics which aims at describing nature? The author discusses how the connecting link of these two disciplines is provided by the compact Riemann surfaces. These appear as world sheets of interacting strings. For instance, string-string scattering at the three-loop level involves the four external strings attaching themselves to a genus three compact surface

  1. EXTENSIVE LISTENING: LET STUDENTS EXPERIENCE LEARNING BY OPTIMIZING THE USE OF AUTHENTIC MATERIALS

    Directory of Open Access Journals (Sweden)

    Yulia Hapsari

    2014-10-01

    Full Text Available In a country like Indonesia, one of challenges in learning English as a foreign language is a lack of exposure of English in its authentic sense. The use of authentic materials seems to be an option to cope with this situation. One of the ways to optimize the use of the authentic materials to trigger students to experience learning and to enhance their active involvement in the learning process is by using it in extensive listening activities. Through extensive listening by using authentic materials, students are exposed to real native speech in meaningful language use. As the result, difficulties in listening gradually disappear.  In order to put the idea into practice, the first thing to do is to set objectives of each meeting based on core vocabulary and grammar that are suitable for the learners using comprehensible input principle as the basic consideration. Second, selecting authentic materials that suit the objectives and that give exposure to formulaic language and meaningful language use. Then, preparing activities in which the instruction is reasonable and lead to sufficient practice to develop fluency. Finally, synchronize teaching activities to increase students’ motivation to learn. As a follow up activities, students are informed and eventually involved in the whole process. Thus, students experience learning and actively involved in their learning process.

  2. Open-closed string correspondence in open string field theory

    International Nuclear Information System (INIS)

    Baumgartl, M.; Sachs, I.

    2008-01-01

    We address the problem of describing different closed string backgrounds in background independent open string field theory: A shift in the closed string background corresponds to a collective excitation of open strings. As an illustration we apply the formalism to the case where the closed string background is a group manifold. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  3. Strings, texture, and inflation

    International Nuclear Information System (INIS)

    Hodges, H.M.; Primack, J.R.

    1991-01-01

    We examine mechanisms, several of which are proposed here, to generate structure formation, or to just add large-scale features, through either gauged or global cosmic strings or global texture, within the framework of inflation. We first explore the possibility that strings or texture form if there is no coupling between the topological theory and the inflaton or spacetime curvature, via (1) quantum creation, and (2) a sufficiently high reheat temperature. In addition, we examine the prospects for the inflaton field itself to generate strings or texture. Then, models with the string/texture field coupled to the curvature, and an equivalent model with coupling to the inflaton field, are considered in detail. The requirement that inflationary density fluctuations are not so large as to conflict with observations leads to a number of constraints on model parameters. We find that strings of relevance for structure formation can form in the absence of coupling to the inflaton or curvature through the process of quantum creation, but only if the strings are strongly type I, or if they are global strings. If formed after reheating, naturalness suggests that gauged cosmic strings correspond to a type-I superconductor. Similarly, gauged strings formed during inflation via conformal coupling ξ=1/6 to the spacetime curvature (in a model suggested by Yokoyama in order to evade the millisecond pulsar constraint on cosmic strings) are expected to be strongly type I

  4. Precise Analysis of String Expressions

    DEFF Research Database (Denmark)

    Christensen, Aske Simon; Møller, Anders; Schwartzbach, Michael Ignatieff

    2003-01-01

    , including statically checking the syntax of dynamically generated expressions, such as SQL queries. Our analysis constructs flow graphs from class files and generates a context-free grammar with a nonterminal for each string expression. The language of this grammar is then widened into a regular language......We perform static analysis of Java programs to answer a simple question: which values may occur as results of string expressions? The answers are summarized for each expression by a regular language that is guaranteed to contain all possible values. We present several applications of this analysis...... are automatically produced. We present extensive benchmarks demonstrating that the analysis is efficient and produces results of useful precision....

  5. Bajan Birds Pull Strings: Two Wild Antillean Species Enter the Select Club of String-Pullers.

    Science.gov (United States)

    Audet, Jean-Nicolas; Ducatez, Simon; Lefebvre, Louis

    2016-01-01

    String-pulling is one of the most popular tests in animal cognition because of its apparent complexity, and of its potential to be applied to very different taxa. In birds, the basic procedure involves a food reward, suspended from a perch by a string, which can be reached by a series of coordinated pulling actions with the beak and holding actions of the pulled lengths of string with the foot. The taxonomic distribution of species that pass the test includes several corvids, parrots and parids, but in other families, data are much spottier and the number of individuals per species that succeed is often low. To date, the association between string-pulling ability and other cognitive traits was never tested. It is generally assumed that string-pulling is a complex form of problem-solving, suggesting that performance on string-pulling and other problem-solving tasks should be correlated. Here, we show that individuals of two innovative species from Barbados, the bullfinch Loxigilla barbadensis and the Carib grackle Quiscalus lugubris fortirostris, pass the string-pulling test. Eighteen of the 42 bullfinches tested succeeded, allowing us to correlate performance on this test to that on several other behavioral measurements. Surprisingly, string-pulling in bullfinches was unrelated to shyness, neophobia, problem-solving, discrimination and reversal learning performance. Only two of 31 grackles tested succeeded, precluding correlational analyses with other measures but still, the two successful birds largely differed in their other behavioral traits.

  6. Automatic labeling of MR brain images through extensible learning and atlas forests.

    Science.gov (United States)

    Xu, Lijun; Liu, Hong; Song, Enmin; Yan, Meng; Jin, Renchao; Hung, Chih-Cheng

    2017-12-01

    Multiatlas-based method is extensively used in MR brain images segmentation because of its simplicity and robustness. This method provides excellent accuracy although it is time consuming and limited in terms of obtaining information about new atlases. In this study, an automatic labeling of MR brain images through extensible learning and atlas forest is presented to address these limitations. We propose an extensible learning model which allows the multiatlas-based framework capable of managing the datasets with numerous atlases or dynamic atlas datasets and simultaneously ensure the accuracy of automatic labeling. Two new strategies are used to reduce the time and space complexity and improve the efficiency of the automatic labeling of brain MR images. First, atlases are encoded to atlas forests through random forest technology to reduce the time consumed for cross-registration between atlases and target image, and a scatter spatial vector is designed to eliminate errors caused by inaccurate registration. Second, an atlas selection method based on the extensible learning model is used to select atlases for target image without traversing the entire dataset and then obtain the accurate labeling. The labeling results of the proposed method were evaluated in three public datasets, namely, IBSR, LONI LPBA40, and ADNI. With the proposed method, the dice coefficient metric values on the three datasets were 84.17 ± 4.61%, 83.25 ± 4.29%, and 81.88 ± 4.53% which were 5% higher than those of the conventional method, respectively. The efficiency of the extensible learning model was evaluated by state-of-the-art methods for labeling of MR brain images. Experimental results showed that the proposed method could achieve accurate labeling for MR brain images without traversing the entire datasets. In the proposed multiatlas-based method, extensible learning and atlas forests were applied to control the automatic labeling of brain anatomies on large atlas datasets or dynamic

  7. Topics in string theory

    International Nuclear Information System (INIS)

    Neveu, A.

    1986-01-01

    There exist several string models. In the first lecture, the simplest one, the open bosonic string, which turns out to live most naturally in 26 dimensions will be described in some detail. In the second lecture, the closed bosonic strings, and the open and closed 10-dimensional strings (superstrings) are reviewed. In the third lecture, various compactification schemes which have been proposed to deal with the extra space dimensions, from 4 to 10 or 26 are dealt with; in particular, the Frenkel-Kac construction which builds non-Abelian internal symmetry groups out of the compactified dimensions, and the resulting heterotic string are described. Finally, in the fourth lecture, the important problem of the second quantization of string theories, and of the underlying gauge invariance which is responsible for the possibility of dealing, in a consistent fashion, with interacting high-spin states without negative metric is addressed. 41 references, 8 figures

  8. N = 2 string amplitudes

    International Nuclear Information System (INIS)

    Ooguri, H.

    1995-08-01

    In physics, solvable models have played very important roles. Understanding a simple model in detail teaches us a lot about more complicated models in generic situations. Five years ago, C. Vafa and I found that the closed N = 2 string theory, that is a string theory with the N = 2 local supersymmetry on the worldsheet, is classically equivalent to the self-dual Einstein gravity in four spacetime dimensions. Thus this string theory is solvable at the classical level. More recently, we have examined the N = 2 string partition function for spacial compactifications, and computed it to all order in the string perturbation expansion. The fact that such computation is possible at all suggests that the N = 2 string theory is solvable even quantum mechanically

  9. Optimal Packed String Matching

    DEFF Research Database (Denmark)

    Ben-Kiki, Oren; Bille, Philip; Breslauer, Dany

    2011-01-01

    In the packed string matching problem, each machine word accommodates – characters, thus an n-character text occupies n/– memory words. We extend the Crochemore-Perrin constantspace O(n)-time string matching algorithm to run in optimal O(n/–) time and even in real-time, achieving a factor – speedup...... over traditional algorithms that examine each character individually. Our solution can be efficiently implemented, unlike prior theoretical packed string matching work. We adapt the standard RAM model and only use its AC0 instructions (i.e., no multiplication) plus two specialized AC0 packed string...

  10. Interpolating string field theories

    International Nuclear Information System (INIS)

    Zwiebach, B.

    1992-01-01

    This paper reports that a minimal area problem imposing different length conditions on open and closed curves is shown to define a one-parameter family of covariant open-closed quantum string field theories. These interpolate from a recently proposed factorizable open-closed theory up to an extended version of Witten's open string field theory capable of incorporating on shell closed strings. The string diagrams of the latter define a new decomposition of the moduli spaces of Riemann surfaces with punctures and boundaries based on quadratic differentials with both first order and second order poles

  11. 6d string chains

    Science.gov (United States)

    Gadde, Abhijit; Haghighat, Babak; Kim, Joonho; Kim, Seok; Lockhart, Guglielmo; Vafa, Cumrun

    2018-02-01

    We consider bound states of strings which arise in 6d (1,0) SCFTs that are realized in F-theory in terms of linear chains of spheres with negative self-intersections 1,2, and 4. These include the strings associated to N small E 8 instantons, as well as the ones associated to M5 branes probing A and D type singularities in M-theory or D5 branes probing ADE singularities in Type IIB string theory. We find that these bound states of strings admit (0,4) supersymmetric quiver descriptions and show how one can compute their elliptic genera.

  12. QCD and hadronic strings

    International Nuclear Information System (INIS)

    Cohen-Tannoudji, G.

    1989-01-01

    This series of lectures is devoted to review ot he connections between QCD and string theories. One reviews the phenomenological models leading to string pictures in non perturbative QCD and the string effects, related to soft gluon coherence, which arise in perturbative QCD. One tries to build a string theory which goes to QCD at the zero slope limit. A specific model, based on superstring theories is shown to agree with QCD four point amplitudes at the Born approximation and with one loop corrections. One shows how this approach can provide a theoretical framework to account for the phenomenological property of parton-hadron duality.(author)

  13. Heterotic cosmic strings

    International Nuclear Information System (INIS)

    Becker, Katrin; Becker, Melanie; Krause, Axel

    2006-01-01

    We show that all three conditions for the cosmological relevance of heterotic cosmic strings, the right tension, stability and a production mechanism at the end of inflation, can be met in the strongly coupled M-theory regime. Whereas cosmic strings generated from weakly coupled heterotic strings have the well-known problems posed by Witten in 1985, we show that strings arising from M5-branes wrapped around 4-cycles (divisors) of a Calabi-Yau in heterotic M-theory compactifications solve these problems in an elegant fashion

  14. Maximum margin classifier working in a set of strings.

    Science.gov (United States)

    Koyano, Hitoshi; Hayashida, Morihiro; Akutsu, Tatsuya

    2016-03-01

    Numbers and numerical vectors account for a large portion of data. However, recently, the amount of string data generated has increased dramatically. Consequently, classifying string data is a common problem in many fields. The most widely used approach to this problem is to convert strings into numerical vectors using string kernels and subsequently apply a support vector machine that works in a numerical vector space. However, this non-one-to-one conversion involves a loss of information and makes it impossible to evaluate, using probability theory, the generalization error of a learning machine, considering that the given data to train and test the machine are strings generated according to probability laws. In this study, we approach this classification problem by constructing a classifier that works in a set of strings. To evaluate the generalization error of such a classifier theoretically, probability theory for strings is required. Therefore, we first extend a limit theorem for a consensus sequence of strings demonstrated by one of the authors and co-workers in a previous study. Using the obtained result, we then demonstrate that our learning machine classifies strings in an asymptotically optimal manner. Furthermore, we demonstrate the usefulness of our machine in practical data analysis by applying it to predicting protein-protein interactions using amino acid sequences and classifying RNAs by the secondary structure using nucleotide sequences.

  15. Superfermionic superconformal string model

    International Nuclear Information System (INIS)

    Kudryavtsev, V.A.

    1994-01-01

    A new approach to superconformal dynamics of string interactions is formulated in terms of two-dimensional fermion fields and without boson fields commonly used in string theories. The vertex operators for emission of π-mesons are constructed within the framework of this approach. 5 refs

  16. Semilocal and electroweak strings

    NARCIS (Netherlands)

    Achucarro, A; Vachaspati, T

    We review a class of non-topological defects in the standard electroweak model, and their implications. Starting with the semilocal string, which provides a counterexample to many well-known properties of topological vortices, we discuss electroweak strings and their stability with and without

  17. Inflationary string theory?

    Indian Academy of Sciences (India)

    Furthermore, the success of this description indicates that inflation is likely to be associated with physics at energies considerably higher than the weak scale, for which string theory is arguably our most promising candidate. These observations strongly motivate a detailed search for inflation within string theory, although it ...

  18. Acoustical properties of drill strings

    Energy Technology Data Exchange (ETDEWEB)

    Drumheller, D.S.

    1988-08-01

    The recovery of petrochemical and geothermal resources requires extensive drilling of wells to increasingly greater depths. Real-time collection and telemetry of data about the drilling process while it occurs thousands of feet below the surface is an effective way of improving the efficiency of drilling operations. Unfortunately, due to hostile down-hole environments, telemetry of this data is an extremely difficult problem. Currently, commercial systems transmit data to the surface by producing pressure pulses within the portion of the drilling mud enclosed in the hollow steel drill string. Transmission rates are between two and four data bits per second. Any system capable of raising data rates without increasing the complexity of the drilling process will have significant economic impact. One alternative system is based upon acoustical carrier waves generated within the drill string itself. If developed, this method would accommodate data rates up to 100 bits per second. Unfortunately, the drill string is a periodic structure of pipe and threaded tool joints, the transmission characteristics are very complex and exhibit a banded and dispersive structure. Over the past forty years, attempts to field systems based upon this transmission method have resulted in little success. This paper examines this acoustical transmission problem in great detail. The basic principles of acoustic wave propagation in the periodic structure of the drill string are examined through theory, laboratory experiment, and field test. The results indicate the existence of frequency bands which are virtually free of attenuation and suitable for data transmission at high bit rates. 9 refs., 38 figs., 2 tabs.

  19. Open string model building

    International Nuclear Information System (INIS)

    Ishibashi, Nobuyuki; Onogi, Tetsuya

    1989-01-01

    Consistency conditions of open string theories, which can be a powerful tool in open string model building, are proposed. By making use of these conditions and assuming a simple prescription for the Chan-Paton factors, open string theories in several backgrounds are studied. We show that 1. there exist a large number of consistent bosonic open string theories on Z 2 orbifolds, 2. SO(32) type I superstring is the unique consistent model among fermionic string theories on the ten-dimensional flat Minkowski space, and 3. with our prescription for the Chan-Paton factors, there exist no consistent open superstring theories on (six-dimensional Minkowski space-time) x (Z 2 orbifold). (orig.)

  20. String-Math 2015

    CERN Document Server

    2015-01-01

    Welcome to String-Math 2015 at Sanya. The conference will be opened in December 31, 2015- January 4, 2016. String theory plays a central role in theoretical physics as a candidate for the quantum theory unifying gravity with other interactions. It has profound connections with broad branches of modern mathematics ever since the birth. In the last decades, the prosperous interaction, built upon the joint efforts from both mathematicians and physicists, has given rise to marvelous deep results in supersymmetric gauge theory, topological string, M-theory and duality on the physics side as well as in algebraic geometry, differential geometry, algebraic topology, representation theory and number theory on the mathematics side. The interplay is two-fold. The mathematics has provided powerful tools to fulfill the physical interconnection of ideas and clarify physical structures to understand the nature of string theory. On the other hand, ideas from string theory and quantum field theory have been a source of sign...

  1. Work-based learning and role extension: A match made in heaven?

    International Nuclear Information System (INIS)

    Eddy, Angela

    2010-01-01

    This paper presents, and discusses the findings from an exploratory study which examined a cohort of postgraduate therapeutic radiographer students' experiences of undertaking work-based learning to support role extension. The findings showed that three themes emerged which impacted on individual experiences: organisational issues, role and practice issues related to competence development and the individual's background and experience. The conclusions are that new models must emerge, and be evaluated, to offer appropriate support to those individuals who demonstrate the skills and ability to progress to advanced and consultant levels. Departments need to deliberate how they can effectively introduce and support role extension, giving specific consideration to study time, the number of higher level practitioners in training, as well as how to offer effective clinical supervision. Collaboration between higher education institutes and departments should enable the development of tripartite agreements to facilitate effective support for the learners.

  2. Work-based learning and role extension: A match made in heaven?

    Energy Technology Data Exchange (ETDEWEB)

    Eddy, Angela [Robert Winston Building, 11-15 Collegiate Crescent Campus, Faculty of Health and Well Being, Sheffield Hallam University, Sheffield S10 2BP (United Kingdom)], E-mail: a.eddy@shu.ac.uk

    2010-05-15

    This paper presents, and discusses the findings from an exploratory study which examined a cohort of postgraduate therapeutic radiographer students' experiences of undertaking work-based learning to support role extension. The findings showed that three themes emerged which impacted on individual experiences: organisational issues, role and practice issues related to competence development and the individual's background and experience. The conclusions are that new models must emerge, and be evaluated, to offer appropriate support to those individuals who demonstrate the skills and ability to progress to advanced and consultant levels. Departments need to deliberate how they can effectively introduce and support role extension, giving specific consideration to study time, the number of higher level practitioners in training, as well as how to offer effective clinical supervision. Collaboration between higher education institutes and departments should enable the development of tripartite agreements to facilitate effective support for the learners.

  3. String Chopping and Time-ordered Products of Linear String-localized Quantum Fields

    Science.gov (United States)

    Cardoso, Lucas T.; Mund, Jens; Várilly, Joseph C.

    2018-03-01

    For a renormalizability proof of perturbative models in the Epstein-Glaser scheme with string-localized quantum fields, one needs to know what freedom one has in the definition of time-ordered products of the interaction Lagrangian. This paper provides a first step in that direction. The basic issue is the presence of an open set of n-tuples of strings which cannot be chronologically ordered. We resolve it by showing that almost all such string configurations can be dissected into finitely many pieces which can indeed be chronologically ordered. This fixes the time-ordered products of linear field factors outside a nullset of string configurations. (The extension across the nullset, as well as the definition of time-ordered products of Wick monomials, will be discussed elsewhere).

  4. String field theory

    International Nuclear Information System (INIS)

    Kaku, M.

    1987-01-01

    In this article, the authors summarize the rapid progress in constructing string field theory actions, such as the development of the covariant BRST theory. They also present the newer geometric formulation of string field theory, from which the BRST theory and the older light cone theory can be derived from first principles. This geometric formulation allows us to derive the complete field theory of strings from two geometric principles, in the same way that general relativity and Yang-Mills theory can be derived from two principles based on global and local symmetry. The geometric formalism therefore reduces string field theory to a problem of finding an invariant under a new local gauge group they call the universal string group (USG). Thus, string field theory is the gauge theory of the universal string group in much the same way that Yang-Mills theory is the gauge theory of SU(N). The geometric formulation places superstring theory on the same rigorous group theoretical level as general relativity and gauge theory

  5. String inflation after Planck 2013

    Energy Technology Data Exchange (ETDEWEB)

    Burgess, C.P. [Department of Physics and Astronomy, McMaster University, Hamilton ON (Canada); Cicoli, M. [Dipartimento di Fisica e Astronomia, Università di Bologna, via Irnerio 46, 40126 Bologna (Italy); Quevedo, F., E-mail: cburgess@perimeterinstitute.ca, E-mail: mcicoli@ictp.it, E-mail: F.Quevedo@damtp.cam.ac.uk [Abdus Salam ICTP, Strada Costiera 11, Trieste 34014 (Italy)

    2013-11-01

    We briefly summarize the impact of the recent Planck measurements for string inflationary models, and outline what might be expected to be learned in the near future from the expected improvement in sensitivity to the primordial tensor-to-scalar ratio. We comment on whether these models provide sufficient added value to compensate for their complexity, and ask how they fare in the face of the new constraints on non-gaussianity and dark radiation. We argue that as a group the predictions made before Planck agree well with what has been seen, and draw conclusions from this about what is likely to mean as sensitivity to primordial gravitational waves improves.

  6. The Use of an e-Learning System for Agricultural Extension: A Case Study of the Rural Development Administration, Korea

    Science.gov (United States)

    Park, Duk-Byeong; Cho, Yong-Been; Lee, Minsoo

    2007-01-01

    The study explores the e-learning system of the Computer-Based Agricultural Extension Program (CBAES) and examines the differences in user satisfaction and preferences between the two systems for Agricultural Education and Extension at the Rural Development Administration (RDA) in Korea. It also describes the architecture, services, user…

  7. Duality relation between charged elastic strings and superconducting cosmic strings

    International Nuclear Information System (INIS)

    Carter, B.

    1989-01-01

    The mechanical properties of macroscopic electromagnetically coupled string models in a flat or curved background are treated using a covariant formalism allowing the construction of a duality transformation that relates the category of uniform ''electric'' string models, constructed as the (nonconducting) charged generalisation of ordinary uncoupled (violin type) elastic strings, to a category of ''magnetic'' string models comprising recently discussed varieties of ''superconducting cosmic strings''. (orig.)

  8. Final Report: "Strings 2014"

    Energy Technology Data Exchange (ETDEWEB)

    Witten, Edward

    2015-10-21

    The Strings 2014 meeting was held at Princeton University June 23-27, 2014, co-sponsored by Princeton University and the Institute for Advanced Study. The goal of the meeting was to provide a stimulating and up-to-date overview of research in string theory and its relations to other areas of physics and mathematics, ranging from geometry to quantum field theory, condensed matter physics, and more. This brief report lists committee members and speakers but contains no scientific information. Note that the talks at Strings 2014 were videotaped and are available on the conference website: http://physics.princeton.edustrings2014/Talk_titles.shtml.

  9. String theory for pedestrians

    CERN Multimedia

    CERN. Geneva

    2007-01-01

    In this 3-lecture series I will discuss the basics of string theory, some physical applications, and the outlook for the future. I will begin with the main concepts of the classical theory and the application to the study of cosmic superstrings. Then I will turn to the quantum theory and discuss applications to the investigation of hadronic spectra and the recently discovered quark-gluon plasma. I will conclude with a sketch of string models of particle physics and showing some avenues that may lead to a complete formulation of string theory.

  10. Superconducting cosmic strings

    International Nuclear Information System (INIS)

    Chudnovsky, E.M.; Field, G.B.; Spergel, D.N.; Vilenkin, A.

    1986-01-01

    Superconducting loops of string formed in the early Universe, if they are relatively light, can be an important source of relativistic particles in the Galaxy. They can be observed as sources of synchrotron radiation at centimeter wavelengths. We propose a string model for two recently discovered radio sources, the ''thread'' in the galactic center and the source G357.7-0.1, and predict that the filaments in these sources should move at relativistic speeds. We also consider superheavy superconducting strings, and the possibility that they be observed as extragalactic radio sources

  11. The effective supergravity of little string theory

    Science.gov (United States)

    Antoniadis, Ignatios; Delgado, Antonio; Markou, Chrysoula; Pokorski, Stefan

    2018-02-01

    In this work we present the minimal supersymmetric extension of the five-dimensional dilaton-gravity theory that captures the main properties of the holographic dual of little string theory. It is described by a particular gauging of N=2 supergravity coupled with one vector multiplet associated with the string dilaton, along the U(1) subgroup of SU(2) R-symmetry. The linear dilaton in the fifth coordinate solution of the equations of motion (with flat string frame metric) breaks half of the supersymmetries to N=1 in four dimensions. Interest in the linear dilaton model has lately been revived in the context of the clockwork mechanism, which has recently been proposed as a new source of exponential scale separation in field theory.

  12. String theory and the scientific method

    CERN Document Server

    Dawid, Richard

    2013-01-01

    String theory has played a highly influential role in theoretical physics for nearly three decades and has substantially altered our view of the elementary building principles of the Universe. However, the theory remains empirically unconfirmed, and is expected to remain so for the foreseeable future. So why do string theorists have such a strong belief in their theory? This book explores this question, offering a novel insight into the nature of theory assessment itself. Dawid approaches the topic from a unique position, having extensive experience in both philosophy and high-energy physics. He argues that string theory is just the most conspicuous example of a number of theories in high-energy physics where non-empirical theory assessment has an important part to play. Aimed at physicists and philosophers of science, the book does not use mathematical formalism and explains most technical terms.

  13. Cosmic strings and cosmic structure

    International Nuclear Information System (INIS)

    Albrecht, A.; Brandenberger, R.; Turok, N.

    1987-01-01

    The paper concerns the application of the theory of cosmic strings to explain the structure of the Universe. The formation of cosmic strings in the early Universe is outlined, along with the Big Bang theory, Grand Unified theories, and the first three minutes after the Big Bang. A description is given of the shaping of the Universe by cosmic strings, including the evolution of the string. The possibility for direct observation of cosmic strings is discussed. (U.K.)

  14. International conference on string theory

    CERN Document Server

    2017-01-01

    The Strings 2017 conference is part of the "Strings" series of annual conferences, that bring the entire string theory community together. It will include reviews of major developments in the field, and specialized talks on specific topics. There will also be several public lectures given by conference participants, a pre-Strings school at the Technion, and a post-Strings workshop at the Weizmann Institute.

  15. THE IMPACT OF EXTENSIVELY EXPOSING IRANIAN VERY YOUNG EFL LEARNERS TO ENGLISH MEDIA ON THEIR LEARNING PROCESS

    OpenAIRE

    Bardia Delvashi

    2017-01-01

    Teaching and learning to speak English has become increasingly important in Iran mainly due to the fact that English has been identified as one of the world’s most widely-spoken languages. Therefore, the present research attempted to probe whether extensively exposing Iranian very young EFL learners to English media has any significant effect on their learning process, operationalized as their learning growth. The study involved 60 non-native very young EFL learners at different private langu...

  16. Field theory of strings

    International Nuclear Information System (INIS)

    Ramond, P.

    1987-01-01

    We review the construction of the free equations of motion for open and closed strings in 26 dimensions, using the methods of the Florida Group. Differing from previous treatments, we argue that the constraint L 0 -anti L 0 =0 should not be imposed on all the fields of the closed string in the gauge invariant formalism; we show that it can be incorporated in the gauge invariant formalism at the price of being unable to extract the equations of motion from a Langrangian. We then describe our purely algebraic method to introduce interactions, which works equally well for open and closed strings. Quartic interactions are absent except in the Physical Gauge. Finally, we speculate on the role of the measure of the open string path functional. (orig.)

  17. The QCD Effective String

    International Nuclear Information System (INIS)

    Espriu, D.

    2003-01-01

    QCD can be described in a certain kinematical regime by an effective string theory. This string must couple to background chiral fields in a chirally invariant manner, thus taking into account the true chirally non-invariant QCD vacuum. By requiring conformal symmetry of the string and the unitarity constraint on chiral fields we reconstruct the equations of motion for the latter ones. These provide a consistent background for the propagation of the string. By further requiring locality of the effective action we recover the Lagrangian of non-linear sigma model of pion interactions. The prediction is unambiguous and parameter-free. The estimated chiral structural constants of Gasser and Leutwyler fit very well the phenomenological values. (author)

  18. Strings with zero tension

    Energy Technology Data Exchange (ETDEWEB)

    Amorim, R.; Barcelos-Neto, J.

    1988-05-01

    We describe bosonic strings by using a kind of Lagrangian compatible with the zero tension limit. The work is developed on an extended configuration space and the quantization is carried out with details.

  19. Field theory of strings

    International Nuclear Information System (INIS)

    Ramond, P.

    1986-01-01

    We review the construction of the free equations of motion for open and closed strings in 26 dimensions, using the methods of the Florida Group. Differing from previous treatments, we argue that the constraint L 0 - L 0 -bar = 0 should not be imposed on all the fields of the closed string in the gauge invariant formalism: we show that it can be incorporated in the invariant formalism at the price of being unable to extract the equations of motion from a Lagrangian. We then describe our purely algebraic method to introduce interactions, which works equally well for open and closed strings. Quartic interactions are absent except in the Physical Gauge. Finally, we speculate on the role of the measure of the open string path functional. 20 refs

  20. String Theory Rocks!

    CERN Multimedia

    2008-01-01

    String Theory supporters argue that the universe we live in has eleven dimensions, out of which three spacial dimensions and a temporal one, which define the void and the space-time environment we experience daily.

  1. Nonassociativity, Malcev algebras and string theory

    Energy Technology Data Exchange (ETDEWEB)

    Guenaydin, M. [Institute for Gravitation and the Cosmos and Physics Department, Penn State University, University Park, PA (United States); Minic, D. [Department of Physics, Virginia Tech, Blacksburg, VA (United States)

    2013-10-15

    Nonassociative structures have appeared in the study of D-branes in curved backgrounds. In recent work, string theory backgrounds involving three-form fluxes, where such structures show up, have been studied in more detail. We point out that under certain assumptions these nonassociative structures coincide with nonassociative Malcev algebras which had appeared in the quantum mechanics of systems with non-vanishing three-cocycles, such as a point particle moving in the field of a magnetic charge. We generalize the corresponding Malcev algebras to include electric as well as magnetic charges. These structures find their classical counterpart in the theory of Poisson-Malcev algebras and their generalizations. We also study their connection to Stueckelberg's generalized Poisson brackets that do not obey the Jacobi identity and point out that nonassociative string theory with a fundamental length corresponds to a realization of his goal to find a non-linear extension of quantum mechanics with a fundamental length. Similar nonassociative structures are also known to appear in the cubic formulation of closed string field theory in terms of open string fields, leading us to conjecture a natural string-field theoretic generalization of the AdS/CFT-like (holographic) duality. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Nonassociativity, Malcev algebras and string theory

    International Nuclear Information System (INIS)

    Guenaydin, M.; Minic, D.

    2013-01-01

    Nonassociative structures have appeared in the study of D-branes in curved backgrounds. In recent work, string theory backgrounds involving three-form fluxes, where such structures show up, have been studied in more detail. We point out that under certain assumptions these nonassociative structures coincide with nonassociative Malcev algebras which had appeared in the quantum mechanics of systems with non-vanishing three-cocycles, such as a point particle moving in the field of a magnetic charge. We generalize the corresponding Malcev algebras to include electric as well as magnetic charges. These structures find their classical counterpart in the theory of Poisson-Malcev algebras and their generalizations. We also study their connection to Stueckelberg's generalized Poisson brackets that do not obey the Jacobi identity and point out that nonassociative string theory with a fundamental length corresponds to a realization of his goal to find a non-linear extension of quantum mechanics with a fundamental length. Similar nonassociative structures are also known to appear in the cubic formulation of closed string field theory in terms of open string fields, leading us to conjecture a natural string-field theoretic generalization of the AdS/CFT-like (holographic) duality. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Manipulating Strings in Python

    Directory of Open Access Journals (Sweden)

    William J. Turkel

    2012-07-01

    Full Text Available This lesson is a brief introduction to string manipulation techniques in Python. Knowing how to manipulate strings plays a crucial role in most text processing tasks. If you’d like to experiment with the following lessons, you can write and execute short programs as we’ve been doing, or you can open up a Python shell / Terminal to try them out on the command line.

  4. String dynamics in QCD

    International Nuclear Information System (INIS)

    Gervais, J.L.; Neveu, A.

    1980-01-01

    Recent works of the authors on string interpretation of the Wilson loop operators in QCD are reviewed in a self-contained fashion. Although most of the results habe already appeared in print, some new material is presented in renormalization of the Wilson loop operator and on the use of light-cone expansion to derive a linear string-like equation in light-cone formalism. (orig.)

  5. String scattering amplitudes and deformed cubic string field theory

    Directory of Open Access Journals (Sweden)

    Sheng-Hong Lai

    2018-01-01

    Full Text Available We study string scattering amplitudes by using the deformed cubic string field theory which is equivalent to the string field theory in the proper-time gauge. The four-string scattering amplitudes with three tachyons and an arbitrary string state are calculated. The string field theory yields the string scattering amplitudes evaluated on the world sheet of string scattering whereas the conventional method, based on the first quantized theory brings us the string scattering amplitudes defined on the upper half plane. For the highest spin states, generated by the primary operators, both calculations are in perfect agreement. In this case, the string scattering amplitudes are invariant under the conformal transformation, which maps the string world sheet onto the upper half plane. If the external string states are general massive states, generated by non-primary field operators, we need to take into account carefully the conformal transformation between the world sheet and the upper half plane. We show by an explicit calculation that the string scattering amplitudes calculated by using the deformed cubic string field theory transform into those of the first quantized theory on the upper half plane by the conformal transformation, generated by the Schwarz–Christoffel mapping.

  6. Learning to learn with farmers : a case study of an adult learning extension project conducted in Queensland, Australia 1990 - 1995

    NARCIS (Netherlands)

    Hamilton, N.A.

    1995-01-01

    In this thesis, the relationship between the use of participatory processes in the development and use of information and knowledge and their impact on change is described and explored. This research utilises a major extension project carried out with respect to fallow management in

  7. Strings, Axions and Solitons.

    Science.gov (United States)

    Dabholkar, Atish

    This thesis is divided into two chapters. Chapter I is about the dynamics of radiating axionic strings and the lower bound on the mass of the invisible axion. It has been suggested that, without inflation, the decay of axionic strings produced after the Peccei -Quinn phase transition is the primary source of cosmic relic axions. Knowing the density of these axions would then allow the derivation of a cosmological bound on the mass of the axion. In order to obtain a sharp bound it is essential to know the spectrum of the emitted axions and the detailed motion of a global string strongly coupled to the axionic field. To this end, following the analogy with Dirac's treatment of classical radiating electrons, self-consistent renormalized equations are obtained that describe the dynamics of a radiating global string interacting with its surrounding axionic field. The numerical formalism for evolving string trajectories using these equations is described, and is applied to the case of a circular loop. It is argued that for large wavelength oscillations of cosmic string loops, the motion is well approximated by the motion of a free Nambu-Goto string with appropriate renormalization. Consequently, a lower bound of 10 ^{-3} eV on the mass of the axion is obtained. Together with the recent upperbound of 4 times 10^{-4 } eV from the supernova SN1987a, it marginally rules out the invisible axion. Chapter II is about superstrings and solitons. It is shown that the quantum renormalization of the superstring tension vanishes to all orders in string perturbation theory. A low-energy analysis of macroscopic superstrings is presented and various analogies between these superstrings and solitons in supersymmetric theories are discussed. These include the existence of exact multi-string solutions of the low -energy supergravity super-Yang-Mills equations of motion and a Bogomol'nyi bound for the energy per unit length which is saturated by these solutions. Arguments are presented that

  8. A Chern-Simons-like action for closed-string field theory

    International Nuclear Information System (INIS)

    Taylor, C.C.

    1989-01-01

    A Chern-Simons-like action is proposed for closed-string field theory. The action involves auxiliary fields of arbitrary ghost number and is defined in terms of the closed-string operations ∫, Q and *, analogous to those introduced by Witten in the construction of open-string field theory. The action is an extension of one proposed for free closed strings and bears a formal relationship to 2 + 1 gravity analogous to that between open-string field theory and (2 + 1)-dimensional Yang-Mills theory. (author)

  9. A colourful approach to string topology

    DEFF Research Database (Denmark)

    Bargheer, Tarje

    For M a compact, orientable manifold and N „ Rn􀀀1 a submanifold, we construct the cleavage operad that acts on MN through correspondences, analogous to the Cacti Operad acting on MS1 , formulating String Topology. For the unit sphere, N : Sn „ Rn􀀀1 we compute the cleavage operad...... apparent links between Knot Theory and String Topology.......For M a compact, orientable manifold and N „ Rn􀀀1 a submanifold, we construct the cleavage operad that acts on MN through correspondences, analogous to the Cacti Operad acting on MS1 , formulating String Topology. For the unit sphere, N : Sn „ Rn􀀀1 we compute the cleavage operad...... is obtained through an extension of the Cleavage Operad. Homotopically the extension is a simplication, and it adjoins a unit to the action on MSn. We nally give advantages of our geometric stance on generalizing String Topology even when N S1:We improve on equivariance of group actions on MSn, and provide...

  10. New Developments in String Gravity and String Cosmology.A Summary Report

    OpenAIRE

    Sanchez, Norma G.

    2002-01-01

    New Developments in String Gravity and String Cosmology are reported: 1-String driven cosmology and its Predictions. 2-The primordial gravitational wave background in string cosmology. 3-Non-singular string cosmologies from Exact Conformal Field Theories. 4-Quantum Field Theory, String Temperature and the String Phase of de Sitter space-time, 5-Hawking Radiation in String Theory and the String Phase of Black Holes. 6-New Dual Relation between Quantum Field Theory regimes and String regimes in...

  11. Vertical string-pulling in green jays (Cyanocorax yncas).

    Science.gov (United States)

    Manrique, Héctor Marín; Molina, Adriano-Bruno Chaves; Posada, Sandra; Colell, Montserrat

    2017-07-01

    The cognition of green jays (Cyanocorax yncas), a non Corvus corvid species, was investigated by using the string-pulling paradigm. Five adult green jays performed a vertical string-pulling task in which they had to retrieve a worm attached to the end of a vertical hanging string while sitting on their perch. In the first experiment, three of the subjects managed to retrieve the worm by pulling on the string with their beaks and stepping on the resulting loop, and thereafter repeating this sequence until the worm was accessible. When subjects were given a choice between two strings in subsequent experiments 2-4, they chose at random between the string connected to the worm and the one connected to a slice of a wooden dowel. In experiment 5, subjects that had failed the previous discrimination series were able, nevertheless, to solve a more stringent vertical string array in which they had to pull up the whole length of the string without any visual access to the worm at the end. We discuss green jays' performance in comparison with other corvid species in which cognition has been more extensively investigated. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Neural-Network Quantum States, String-Bond States, and Chiral Topological States

    Directory of Open Access Journals (Sweden)

    Ivan Glasser

    2018-01-01

    Full Text Available Neural-network quantum states have recently been introduced as an Ansatz for describing the wave function of quantum many-body systems. We show that there are strong connections between neural-network quantum states in the form of restricted Boltzmann machines and some classes of tensor-network states in arbitrary dimensions. In particular, we demonstrate that short-range restricted Boltzmann machines are entangled plaquette states, while fully connected restricted Boltzmann machines are string-bond states with a nonlocal geometry and low bond dimension. These results shed light on the underlying architecture of restricted Boltzmann machines and their efficiency at representing many-body quantum states. String-bond states also provide a generic way of enhancing the power of neural-network quantum states and a natural generalization to systems with larger local Hilbert space. We compare the advantages and drawbacks of these different classes of states and present a method to combine them together. This allows us to benefit from both the entanglement structure of tensor networks and the efficiency of neural-network quantum states into a single Ansatz capable of targeting the wave function of strongly correlated systems. While it remains a challenge to describe states with chiral topological order using traditional tensor networks, we show that, because of their nonlocal geometry, neural-network quantum states and their string-bond-state extension can describe a lattice fractional quantum Hall state exactly. In addition, we provide numerical evidence that neural-network quantum states can approximate a chiral spin liquid with better accuracy than entangled plaquette states and local string-bond states. Our results demonstrate the efficiency of neural networks to describe complex quantum wave functions and pave the way towards the use of string-bond states as a tool in more traditional machine-learning applications.

  13. Neural-Network Quantum States, String-Bond States, and Chiral Topological States

    Science.gov (United States)

    Glasser, Ivan; Pancotti, Nicola; August, Moritz; Rodriguez, Ivan D.; Cirac, J. Ignacio

    2018-01-01

    Neural-network quantum states have recently been introduced as an Ansatz for describing the wave function of quantum many-body systems. We show that there are strong connections between neural-network quantum states in the form of restricted Boltzmann machines and some classes of tensor-network states in arbitrary dimensions. In particular, we demonstrate that short-range restricted Boltzmann machines are entangled plaquette states, while fully connected restricted Boltzmann machines are string-bond states with a nonlocal geometry and low bond dimension. These results shed light on the underlying architecture of restricted Boltzmann machines and their efficiency at representing many-body quantum states. String-bond states also provide a generic way of enhancing the power of neural-network quantum states and a natural generalization to systems with larger local Hilbert space. We compare the advantages and drawbacks of these different classes of states and present a method to combine them together. This allows us to benefit from both the entanglement structure of tensor networks and the efficiency of neural-network quantum states into a single Ansatz capable of targeting the wave function of strongly correlated systems. While it remains a challenge to describe states with chiral topological order using traditional tensor networks, we show that, because of their nonlocal geometry, neural-network quantum states and their string-bond-state extension can describe a lattice fractional quantum Hall state exactly. In addition, we provide numerical evidence that neural-network quantum states can approximate a chiral spin liquid with better accuracy than entangled plaquette states and local string-bond states. Our results demonstrate the efficiency of neural networks to describe complex quantum wave functions and pave the way towards the use of string-bond states as a tool in more traditional machine-learning applications.

  14. PT-symmetric strings

    International Nuclear Information System (INIS)

    Amore, Paolo; Fernández, Francisco M.; Garcia, Javier; Gutierrez, German

    2014-01-01

    We study both analytically and numerically the spectrum of inhomogeneous strings with PT-symmetric density. We discuss an exactly solvable model of PT-symmetric string which is isospectral to the uniform string; for more general strings, we calculate exactly the sum rules Z(p)≡∑ n=1 ∞ 1/E n p , with p=1,2,… and find explicit expressions which can be used to obtain bounds on the lowest eigenvalue. A detailed numerical calculation is carried out for two non-solvable models depending on a parameter, obtaining precise estimates of the critical values where pair of real eigenvalues become complex. -- Highlights: •PT-symmetric Hamiltonians exhibit real eigenvalues when PT symmetry is unbroken. •We study PT-symmetric strings with complex density. •They exhibit regions of unbroken PT symmetry. •We calculate the critical parameters at the boundaries of those regions. •There are exact real sum rules for some particular complex densities

  15. Windings of twisted strings

    Science.gov (United States)

    Casali, Eduardo; Tourkine, Piotr

    2018-03-01

    Twistor string models have been known for more than a decade now but have come back under the spotlight recently with the advent of the scattering equation formalism which has greatly generalized the scope of these models. A striking ubiquitous feature of these models has always been that, contrary to usual string theory, they do not admit vibrational modes and thus describe only conventional field theory. In this paper we report on the surprising discovery of a whole new sector of one of these theories which we call "twisted strings," when spacetime has compact directions. We find that the spectrum is enhanced from a finite number of states to an infinite number of interacting higher spin massive states. We describe both bosonic and world sheet supersymmetric models, their spectra and scattering amplitudes. These models have distinctive features of both string and field theory, for example they are invariant under stringy T-duality but have the high energy behavior typical of field theory. Therefore they describe a new kind of field theories in target space, sitting on their own halfway between string and field theory.

  16. Perspectives on string phenomenology

    CERN Document Server

    Kane, Gordon; Kumar, Piyush

    2015-01-01

    The remarkable recent discovery of the Higgs boson at the CERN Large Hadron Collider completed the Standard Model of particle physics and has paved the way for understanding the physics which may lie beyond it. String/M theory has emerged as a broad framework for describing a plethora of diverse physical systems, which includes condensed matter systems, gravitational systems as well as elementary particle physics interactions. If string/M theory is to be considered as a candidate theory of Nature, it must contain an effectively four-dimensional universe among its solutions that is indistinguishable from our own. In these solutions, the extra dimensions of string/M Theory are “compactified” on tiny scales which are often comparable to the Planck length. String phenomenology is the branch of string/M theory that studies such solutions, relates their properties to data, and aims to answer many of the outstanding questions of particle physics beyond the Standard Model. This book contains perspectives on stri...

  17. Non-Perturbative Nekrasov Partition Function from String Theory

    CERN Document Server

    Antoniadis, Ignatios; Hohenegger, Stefan; Narain, K S; Assi, Ahmad Zein

    2014-01-01

    We calculate gauge instanton corrections to a class of higher derivative string effective couplings introduced in [1]. We work in Type I string theory compactified on K3xT2 and realise gauge instantons in terms of D5-branes wrapping the internal space. In the field theory limit we reproduce the deformed ADHM action on a general {\\Omega}-background from which one can compute the non-perturbative gauge theory partition function using localisation. This is a non-perturbative extension of [1] and provides further evidence for our proposal of a string theory realisation of the {\\Omega}-background.

  18. Wavy strings: Black or bright?

    International Nuclear Information System (INIS)

    Kaloper, N.; Myers, R.C.; Roussel, H.

    1997-01-01

    Recent developments in string theory have brought forth considerable interest in time-dependent hair on extended objects. This novel new hair is typically characterized by a wave profile along the horizon and angular momentum quantum numbers l,m in the transverse space. In this work, we present an extensive treatment of such oscillating black objects, focusing on their geometric properties. We first give a theorem of purely geometric nature, stating that such wavy hair cannot be detected by any scalar invariant built out of the curvature and/or matter fields. However, we show that the tidal forces detected by an infalling observer diverge at the open-quotes horizonclose quotes of a black string superposed with a vibration in any mode with l≥1. The same argument applied to longitudinal (l=0) waves detects only finite leading-order tidal forces. We also provide an example with a manifestly smooth metric, proving that at least a certain class of these longitudinal waves have regular horizons. copyright 1997 The American Physical Society

  19. String field theory solution for any open string background

    Czech Academy of Sciences Publication Activity Database

    Erler, T.; Maccaferri, Carlo

    2014-01-01

    Roč. 10, Oct (2014), 1-37 ISSN 1029-8479 R&D Projects: GA ČR GBP201/12/G028 Institutional support: RVO:68378271 Keywords : tachyon condensation * string field theory * conformal field models in string theory * bosonic strings Subject RIV: BE - Theoretical Physics Impact factor: 6.111, year: 2014

  20. Interacting-string picture of the fermionic string

    International Nuclear Information System (INIS)

    Mandelstam, S.

    1986-01-01

    This report gives a review of the interacting-string picture of the Bose string. In the present lecture, the author outlines a similar treatment of the Fermionic string. The quantization of the free Fermionic string is carried out to the degrees of freedom x, representing the displacement of the string. Also presented are Grassman degrees of freedom S distributed along the string. The report pictures the fermionic string as a string of dipoles. The general picture of the interaction of such strings by joining and splitting is the same as for the Bose string. The author does not at present have the simplest formula for fermion string scattering amplitudes. A less detailed treatment is given than for the Bose string. The report sets up the functional-integration formalism, derives the analog mode, and indicates in general, terms how the conformal transformation to the z-plane may be performed. The paper concludes by stating without proof the formula for the N-article tree amplitude in the manifestly supersymmetric formalism

  1. The confining trailing string

    CERN Document Server

    Kiritsis, E; Nitti, F

    2014-01-01

    We extend the holographic trailing string picture of a heavy quark to the case of a bulk geometry dual to a confining gauge theory. We compute the classical trailing confining string solution for a static as well as a uniformly moving quark. The trailing string is infinitely extended and approaches a confining horizon, situated at a critical value of the radial coordinate, along one of the space-time directions, breaking boundary rotational invariance. We compute the equations for the fluctuations around the classical solutions, which are used to obtain boundary force correlators controlling the Langevin dynamics of the quark. The imaginary part of the correlators has a non-trivial low-frequency limit, which gives rise to a viscous friction coefficient induced by the confining vacuum. The vacuum correlators are used to define finite-temperature dressed Langevin correlators with an appropriate high-frequency behavior.

  2. The confining trailing string

    Energy Technology Data Exchange (ETDEWEB)

    Kiritsis, Elias [APC, Université Paris 7, CNRS/IN2P3, CEA/IRFU, Obs. de Paris, Sorbonne Paris Cité,Bâtiment Condorcet, F-75205, Paris Cedex 13 (UMR du CNRS 7164) (France); Theory Group, Physics Department, CERN,CH-1211, Geneva 23 (Switzerland); Crete Center for Theoretical Physics, Department of Physics, University of Crete,71003 Heraklion (Greece); Mazzanti, Liuba [Institute for Theoretical Physics and Spinoza Institute, Utrecht University,3508 TD Utrecht (Netherlands); Nitti, Francesco [APC, Université Paris 7, CNRS/IN2P3, CEA/IRFU, Obs. de Paris, Sorbonne Paris Cité,Bâtiment Condorcet, F-75205, Paris Cedex 13 (UMR du CNRS 7164) (France)

    2014-02-19

    We extend the holographic trailing string picture of a heavy quark to the case of a bulk geometry dual to a confining gauge theory. We compute the classical trailing confining string solution for a static as well as a uniformly moving quark. The trailing string is infinitely extended and approaches a confining horizon, situated at a critical value of the radial coordinate, along one of the space-time directions, breaking boundary rotational invariance. We compute the equations for the fluctuations around the classical solutions, which are used to obtain boundary force correlators controlling the Langevin dynamics of the quark. The imaginary part of the correlators has a non-trivial low-frequency limit, which gives rise to a viscous friction coefficient induced by the confining vacuum. The vacuum correlators are used to define finite-temperature dressed Langevin correlators with an appropriate high-frequency behavior.

  3. String theory meets QCD

    CERN Document Server

    Evans, N

    2003-01-01

    String theory began life in the late 1960s as an attempt to understand the properties of nuclear matter such as protons and neutrons. Although it was not successful it has since developed a life of its own as a possible theory of everything - with the potential to incorporate quantum gravity as well as the other forces of nature. However, in a remarkable about face in the last five years, it has now been discovered that string theory and the standard theory of nuclear matter - QCD - might in fact describe the same physics. This is an exciting development that was the centre of discussion at a major workshop in Seattle in February. After spending 30 years as a possible theory of everything, string theory is returning to its roots to describe the interactions of quarks and gluons. (U.K.)

  4. Deriving the four-string and open-closed string interactions from geometric string field theory

    International Nuclear Information System (INIS)

    Kaku, M.

    1990-01-01

    One of the questions concerning the covariant open string field theory is why there are two distinct BRST theories and why the four-string interaction appears in one version but not the other. The authors solve this mystery by showing that both theories are gauge-fixed versions of a higher gauge theory, called the geometric string field theory, with a new field, a string verbein e μσ νρ , which allows us to gauge the string length and σ parametrization. By fixing the gauge, the authors can derive the endpoint gauge (the covariantized light cone gauge), the midpoint gauge of Witten, or the interpolating gauge with arbitrary string length. The authors show explicitly that the four-string interaction is a gauge artifact of the geometric theory (the counterpart of the four-fermion instantaneous Coulomb term of QED). By choosing the interpolating gauge, they produce a new class of four-string interactions which smoothly interpolate between the endpoint gauge and the midpoint gauge (where it vanishes). Similarly, they can extract the closed string as a bound state of the open string, which appears in the endpoint gauge but vanishes in the midpoint gauge. Thus, the four-string and open-closed string interactions do not have to be added to the action as long as the string vierbein is included

  5. Instability of colliding metastable strings

    Energy Technology Data Exchange (ETDEWEB)

    Hiramatsu, Takashi [Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics; Eto, Minoru [Yamagata Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research

    2013-04-15

    We investigate the collision dynamics of two metastable strings which can be viewed as tube-like domain walls with winding numbers interpolating a false vacuum and a true vacuum. We find that depending on the relative angle and speed of two strings, instability of strings increases and the false vacuum is filled out by rapid expansion of the strings or of a remnant of the collision.

  6. String theory in four dimensions

    International Nuclear Information System (INIS)

    Dine, M.

    1988-01-01

    A representative sample of current ideas about how one might develop a string phenomenology is presented. Some of the obstacles which lie in between string theory and contact with experiment are described. It is hoped that this volume will provide the reader with ways of thinking about string theory in four dimensions and provide tools for asking questions about string theory and ordinary physics. 102 refs

  7. Matrix string partition function

    CERN Document Server

    Kostov, Ivan K; Kostov, Ivan K.; Vanhove, Pierre

    1998-01-01

    We evaluate quasiclassically the Ramond partition function of Euclidean D=10 U(N) super Yang-Mills theory reduced to a two-dimensional torus. The result can be interpreted in terms of free strings wrapping the space-time torus, as expected from the point of view of Matrix string theory. We demonstrate that, when extrapolated to the ultraviolet limit (small area of the torus), the quasiclassical expressions reproduce exactly the recently obtained expression for the partition of the completely reduced SYM theory, including the overall numerical factor. This is an evidence that our quasiclassical calculation might be exact.

  8. Cover array string reconstruction

    OpenAIRE

    Crochemore, Maxime; S. Iliopoulos, Costas; P. Pissis, Solon; Tischler, German

    2010-01-01

    International audience; A proper factor u of a string y is a cover of y if every letter of y is within some occurrence of u in y. The concept generalises the notion of periods of a string. An integer array C is the minimal-cover (resp. maximal-cover) array of y if C[i] is the minimal (resp. maximal) length of covers of y[0.. i], or zero if no cover exists. In this paper, we present a constructive algorithm checking the validity of an array as a minimal-cover or maximal-cover array of some str...

  9. String theory in four dimensions

    CERN Document Server

    1988-01-01

    ``String Theory in Four Dimensions'' contains a representative collection of papers dealing with various aspects of string phenomenology, including compactifications on smooth manifolds and more general conformal field theories. Together with the lucid introduction by M. Dine, this material gives the reader a good working knowledge of our present ideas for connecting string theory to nature.

  10. Why Strings? Grand Masters Series.

    Science.gov (United States)

    Klotman, Robert H.

    2000-01-01

    Discusses the reasons to teach stringed instruments: (1) strings can be adapted to the size of the child; (2) home performance material resource availability; (3) stringed music skills contribute to developing basic skills; and (4) the importance of interaction in music. (CMK)

  11. The proboscis extension reflex to evaluate learning and memory in honeybees ( Apis mellifera): some caveats

    Science.gov (United States)

    Frost, Elisabeth H.; Shutler, Dave; Hillier, Neil Kirk

    2012-09-01

    The proboscis extension reflex (PER) is widely used in a classical conditioning (Pavlovian) context to evaluate learning and memory of a variety of insect species. The literature is particularly prodigious for honeybees ( Apis mellifera) with more than a thousand publications. Imagination appears to be the only limit to the types of challenges to which researchers subject honeybees, including all the sensory modalities and a broad diversity of environmental treatments. Accordingly, some remarkable insights have been achieved using PER. However, there are several challenges to evaluating the PER literature that warrant a careful and thorough review. We assess here variation in methods that makes interpretation of studies, even those researching the same question, tenuous. We suggest that the numerous variables that might influence experimental outcomes from PER be thoroughly detailed by researchers. Moreover, the influence of individual variables on results needs to carefully evaluated, as well as among two or more variables. Our intent is to encourage investigation of the influence of numerous variables on PER results.

  12. Mobile Learning Bridging the Gap in Agricultural Extension Service Delivery: Experiences from Sokoine University of Agriculture, Tanzania

    Science.gov (United States)

    Sanga, Camilius; Mlozi, Malongo; Haug, Ruth; Tumbo, Siza

    2016-01-01

    The ubiquitous nature of mobile phones offers a noble environment where farmers can learn informally anywhere, anytime and at any location. This is an innovative way to address some of the weakness of conventional agricultural extension service. Few empirical studies have reported on the development of mobile phone application to support blended…

  13. A Vibrating String Experiment

    Science.gov (United States)

    Tsutsumanova, Gichka; Russev, Stoyan

    2013-01-01

    A simple experiment demonstrating the excitation of a standing wave in a metal string is presented here. Several tasks using the set-up are considered, which help the students to better understand the standing waves, the interaction between electric current and magnetic field and the resonance phenomena. This can serve also as a good lecture…

  14. New Z3 strings

    Directory of Open Access Journals (Sweden)

    Marco A.C. Kneipp

    2016-12-01

    Full Text Available We consider a Yang–Mills–Higgs theory with the gauge group SU(3 broken to its center Z3 by two scalar fields in the adjoint representation and obtain new Z3 strings asymptotic configurations with the gauge field and magnetic field in the direction of the step operators.

  15. On exceptional instanton strings

    NARCIS (Netherlands)

    Del Zotto, M.; Lockhart, G.

    According to a recent classification of 6d (1, 0) theories within F-theory there are only six “pure” 6d gauge theories which have a UV superconformal fixed point. The corresponding gauge groups are SU(3), SO(8), F4, E6, E7, and E8. These exceptional models have BPS strings which are also instantons

  16. Hypermultiplets and topological strings

    NARCIS (Netherlands)

    Rocek, M.; Vafa, C.; Vandoren, S.

    2005-01-01

    The c-map relates classical hypermultiplet moduli spaces in compactifications of type II strings on a Calabi-Yau threefold to vector multiplet moduli spaces via a further compactification on a circle. We give an off-shell description of the c-map in N = 2 superspace. The superspace Lagrangian for

  17. SUPERCOLLIDER: String test success

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    On 14 August at the Superconducting Supercollider (SSC) Laboratory in Ellis County, Texas, the Accelerator Systems String Test (ASST) successfully met its objective by operating a half-cell of five collider dipole magnets, one quadrupole magnet, and two spool pieces at the design current of 6500 amperes

  18. Disordered chaotic strings

    DEFF Research Database (Denmark)

    Schäfer, Mirko; Greiner, Martin

    Chaotic strings are coupled Tchebyscheff maps on a ring-network. With a well-specified empirical prescription they are able to explain the coupling constants of the standard model of elementary particle physics. This empirical relationship is tested further by introducing a tunable disorder to ch...

  19. Disordered chaotic strings

    DEFF Research Database (Denmark)

    Schäfer, Mirko; Greiner, Martin

    2011-01-01

    Chaotic strings are coupled Tchebyscheff maps on a ring-network. With a well-specified empirical prescription they are able to explain the coupling constants of the standard model of elementary particle physics. This empirical relationship is tested further by introducing a tunable disorder to ch...

  20. Help from the strings

    CERN Multimedia

    2007-01-01

    "How can the nature of basic particles be defined beyond the mechanisms presiding over their creation? Besides the standard model of particle physics - resulting from the postulations of quantum mechanics - contemporary science has pinned its hopes on the totally new unifying notion provided by the highly mathematical string theory."(2 pages)

  1. On exceptional instanton strings

    Science.gov (United States)

    Del Zotto, Michele; Lockhart, Guglielmo

    2017-09-01

    According to a recent classification of 6d (1 , 0) theories within F-theory there are only six "pure" 6d gauge theories which have a UV superconformal fixed point. The corresponding gauge groups are SU(3) , SO(8) , F 4 , E 6 , E 7, and E 8. These exceptional models have BPS strings which are also instantons for the corresponding gauge groups. For G simply-laced, we determine the 2d N=(0,4) worldsheet theories of such BPS instanton strings by a simple geometric engineering argument. These are given by a twisted S 2 compactification of the 4d N=2 theories of type H 2 , D 4 , E 6 , E 7 and E 8 (and their higher rank generalizations), where the 6d instanton number is mapped to the rank of the corresponding 4d SCFT. This determines their anomaly polynomials and, via topological strings, establishes an interesting relation among the corresponding T 2 × S 2 partition functions and the Hilbert series for moduli spaces of G instantons. Such relations allow to bootstrap the corresponding elliptic genera by modularity. As an example of such procedure, the elliptic genera for a single instanton string are determined. The same method also fixes the elliptic genus for case of one F 4 instanton. These results unveil a rather surprising relation with the Schur index of the corresponding 4d N=2 models.

  2. Lectures on strings and dualities

    International Nuclear Information System (INIS)

    Vafa, C.

    1997-01-01

    In this set of lectures I review recent developments in string theory emphasizing their non-perturbative aspects and their recently discovered duality symmetries. The goal of the lectures is to make the recent exciting developments in string theory accessible to those with no previous background in string theory who wish to join the research effort in this area. Topics covered include a brief review of string theory, its compactifications, solitons and D-branes, black hole entropy and wed of string dualities. (author)

  3. Device for balancing parallel strings

    Science.gov (United States)

    Mashikian, Matthew S.

    1985-01-01

    A battery plant is described which features magnetic circuit means in association with each of the battery strings in the battery plant for balancing the electrical current flow through the battery strings by equalizing the voltage across each of the battery strings. Each of the magnetic circuit means generally comprises means for sensing the electrical current flow through one of the battery strings, and a saturable reactor having a main winding connected electrically in series with the battery string, a bias winding connected to a source of alternating current and a control winding connected to a variable source of direct current controlled by the sensing means. Each of the battery strings is formed by a plurality of batteries connected electrically in series, and these battery strings are connected electrically in parallel across common bus conductors.

  4. Gravitational effects of global strings

    International Nuclear Information System (INIS)

    Aryal, M.; Everett, A.E.

    1986-01-01

    We have obtained the gravitational field, in the weak-field approximation, of cosmic strings formed in a phase transition in which a global symmetry is broken (global strings). The effect of this field on light rays passing a global string is found, and the resulting formation of double images and production of discontinuities in the microwave background temperature compared with the corresponding results for gauge strings. There are some differences in the case of global strings, reflecting the fact that the space surrounding such strings is not purely conical. However, the differences between gauge and global strings with masses suitable to explain galaxy formation are small, and the task of distinguishing them observationally appears difficult at best

  5. Stringing physics along

    Energy Technology Data Exchange (ETDEWEB)

    Riordan, M. [Stanford University and the University of California, Santa Cruz (United States)]. E-mail: mriordan@ucsc.edu

    2007-02-15

    In the last few decades, however, physical theory has drifted away from the professional norms advocated by Newton and other enlightenment philosophers. A vast outpouring of hypotheses has occurred under the umbrella of what is widely called string theory. But string theory is not really a 'theory' at all - at least not in the strict sense that scientists generally use the term. It is instead a dense, weedy thicket of hypotheses and conjectures badly in need of pruning. That pruning, however, can come only from observation and experiment, to which string theory (a phrase I will grudgingly continue using) is largely inaccessible. String theory was invented in the 1970s in the wake of the Standard Model of particle physics. Encouraged by the success of gauge theories of the strong, weak and electromagnetic forces, theorists tried to extend similar ideas to energy and distance scales that are orders of magnitude beyond what can be readily observed or measured. The normal, healthy intercourse between theory and experiment - which had led to the Standard Model - has broken down, and fundamental physics now finds itself in a state of crisis. So it is refreshing to hear from a theorist - one who was deeply involved with string theory and championed it in his previous book, Three Roads to Quantum Gravity - that all is not well in this closeted realm. Smolin argues from the outset that viable hypotheses must lead to observable consequences by which they can be tested and judged. String theory by its very nature does not allow for such probing, according to Smolin, and therefore it must be considered as an unprovable conjecture. Towards the end of his book, Smolin suggests other directions fundamental physics can take, particularly in the realm of quantum gravity, to resolve its crisis and reconnect with the observable world. From my perspective, he leans a bit too heavily towards highly speculative ideas such as doubly special relativity, modified Newtonian

  6. Extensions and applications of ensemble-of-trees methods in machine learning

    Science.gov (United States)

    Bleich, Justin

    Ensemble-of-trees algorithms have emerged to the forefront of machine learning due to their ability to generate high forecasting accuracy for a wide array of regression and classification problems. Classic ensemble methodologies such as random forests (RF) and stochastic gradient boosting (SGB) rely on algorithmic procedures to generate fits to data. In contrast, more recent ensemble techniques such as Bayesian Additive Regression Trees (BART) and Dynamic Trees (DT) focus on an underlying Bayesian probability model to generate the fits. These new probability model-based approaches show much promise versus their algorithmic counterparts, but also offer substantial room for improvement. The first part of this thesis focuses on methodological advances for ensemble-of-trees techniques with an emphasis on the more recent Bayesian approaches. In particular, we focus on extensions of BART in four distinct ways. First, we develop a more robust implementation of BART for both research and application. We then develop a principled approach to variable selection for BART as well as the ability to naturally incorporate prior information on important covariates into the algorithm. Next, we propose a method for handling missing data that relies on the recursive structure of decision trees and does not require imputation. Last, we relax the assumption of homoskedasticity in the BART model to allow for parametric modeling of heteroskedasticity. The second part of this thesis returns to the classic algorithmic approaches in the context of classification problems with asymmetric costs of forecasting errors. First we consider the performance of RF and SGB more broadly and demonstrate its superiority to logistic regression for applications in criminology with asymmetric costs. Next, we use RF to forecast unplanned hospital readmissions upon patient discharge with asymmetric costs taken into account. Finally, we explore the construction of stable decision trees for forecasts of

  7. Axions in String Theory

    Energy Technology Data Exchange (ETDEWEB)

    Svrcek, Peter; /Stanford U., Phys. Dept. /SLAC; Witten, Edward; /Princeton, Inst. Advanced Study

    2006-06-09

    In the context of string theory, axions appear to provide the most plausible solution of the strong CP problem. However, as has been known for a long time, in many string-based models, the axion coupling parameter Fa is several orders of magnitude higher than the standard cosmological bounds. We re-examine this problem in a variety of models, showing that Fa is close to the GUT scale or above in many models that have GUT-like phenomenology, as well as some that do not. On the other hand, in some models with Standard Model gauge fields supported on vanishing cycles, it is possible for Fa to be well below the GUT scale.

  8. The theta-structure in string theories - 1: bosonic strings

    International Nuclear Information System (INIS)

    Li Miao.

    1985-09-01

    We explored the theta-structures in bosonic string theories which are similar to those in gauge field theories. The theta-structure of string is due to the multiply connected spatial compact subspace of space-time. The work of this paper shows that there is an energy band E(theta) in the string theory and one may move the tachyon out in theory by choosing some proper theta parameters. (author)

  9. Half-string oscillator approach to string field theory

    International Nuclear Information System (INIS)

    Bordes, J.; Chan Hongmo; Nellen, L.; Tsou Sheungtsun

    1989-05-01

    We give an operator formulation of the string field theory proposed by E. Witten using half-string oscillator modes. This formalism, identifying the physical string states as infinite matrices, is developed in such a way that interactions at the level of vertices can be calculated in terms of products and traces of these matrices without relying on ill-defined manipulations of functional integrals. (author)

  10. Quantized string models

    Energy Technology Data Exchange (ETDEWEB)

    Fradkin, E.S.; Tseytlin, A.A.

    1982-10-15

    We discuss and compare the Lorentz covariant path integral quantization of the three bose string models, namely, the Nambu, Eguchi and Brink-Di Vecchai-Howe-Polyakov (BDHP) ones. Along with a critical review of the subject with some uncertainties and ambiguities clearly stated, various new results are presented. We work out the form of the BDHP string ansatz for the Wilson average and prove a formal inequivalence of the exact Nambu and BDHP models for any space-time dimension d. The above three models known to be equivalent on the classical level, are shown to be equivalent in a semiclassical approximation near a minimal surface and also in the leading 1/d-approximation for the static q-barq-potential. We analyze scattering amplitudes predicted by the BDHP string and find that when exactly calculated for d<26 they are different from the old dual ones, and possess a non-linear spectrum which may be considered as free from tachyons in the ground state.

  11. An invariant string propagator

    International Nuclear Information System (INIS)

    Cohen, A.; Moore, G.; Nelson, P.; Polchinski, J.

    1986-01-01

    The authors show that the Polyakov path integral is used to define off-shell quantities in string theory. The path integral of Polyakov gives an elegant description of strings and their interactions. However, its use has been limited to obtaining the Koba-Nielsen expressions for S-matrix elements. It is not yet clear what quantities make sense in string theory. This study shows that the path integral can be used to define off-shell quantities as well. In particular it defines a natural n-point function in loop space as the sum of all world surfaces bounded by n specific spacetime curves. The reader is referred for more detail. The report first outlines general evaluation then discusses the additional features added by boundaries. Locally, the three gauge freedoms ξ/sup a/ and δphi can be used to take g/sub ab/ (σ) to the unit matrix. Globally, this is not quite possible. In general the researchers choose a family of fiducial metrics g/sub ab/ (σ,tau), depending on a finite number of Teichmuller parameters tau, and every metric is gauge equivalent to one of these

  12. How to simulate global cosmic strings with large string tension

    Energy Technology Data Exchange (ETDEWEB)

    Klaer, Vincent B.; Moore, Guy D., E-mail: vklaer@theorie.ikp.physik.tu-darmstadt.de, E-mail: guy.moore@physik.tu-darmstadt.de [Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstraße 2, Darmstadt, D-64289 Germany (Germany)

    2017-10-01

    Global string networks may be relevant in axion production in the early Universe, as well as other cosmological scenarios. Such networks contain a large hierarchy of scales between the string core scale and the Hubble scale, ln( f {sub a} / H ) ∼ 70, which influences the network dynamics by giving the strings large tensions T ≅ π f {sub a} {sup 2} ln( f {sub a} / H ). We present a new numerical approach to simulate such global string networks, capturing the tension without an exponentially large lattice.

  13. Maximal unbordered factors of random strings

    DEFF Research Database (Denmark)

    Cording, Patrick Hagge; Knudsen, Mathias Bæk Tejs

    2016-01-01

    A border of a string is a non-empty prefix of the string that is also a suffix of the string, and a string is unbordered if it has no border. Loptev, Kucherov, and Starikovskaya [CPM 2015] conjectured the following: If we pick a string of length n from a fixed alphabet uniformly at random...

  14. From lending to learning the development and extension of public libraries

    CERN Document Server

    O'Beirne, Rónán

    2010-01-01

    From Lending to Learning provides a theoretical overview and practical guide to the functional area of delivering learning services within public libraries. It traces the development of public library service delivery and critically appraises the inherent tension between offering an educational-focused or leisure-focused library. The current and future policy directions are explored against the backdrop of the emerging learning society. A general overview of recent developments in learning theory is followed by an insight into the learning landscape. The issues and practicalities of setting up

  15. Counting Dependent and Independent Strings

    Science.gov (United States)

    Zimand, Marius

    We derive quantitative results regarding sets of n-bit strings that have different dependency or independency properties. Let C(x) be the Kolmogorov complexity of the string x. A string y has α dependency with a string x if C(y) - C(y |x) ≥ α. A set of strings {x 1, ..., x t } is pairwise α-independent if for all inot=j, C(x i ) - C(x i |x j ) ≤ α. A tuple of strings (x 1, ..., x t ) is mutually α-independent if C(x π(1) ... x π(t)) ≥ C(x 1) + ... + C(x t ) - α, for every permutation π of [t]. We show that:

  16. Quantum backreaction in string theory

    International Nuclear Information System (INIS)

    Evnin, O.

    2012-01-01

    There are situations in string theory when a finite number of string quanta induce a significant backreaction upon the background and render the perturbation theory infrared-divergent. The simplest example is D0-brane recoil under an impact by closed strings. A more physically interesting case is backreaction on the evolution of a totally compact universe due to closed string gas. Such situations necessitate qualitative amendments to the traditional formulation of string theory in a fixed classical background. In this contribution to the proceedings of the XVII European Workshop on String Theory in Padua, I review solved problems and current investigations in relation to this kind of quantum backreaction effects. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Comparing double string theory actions

    Energy Technology Data Exchange (ETDEWEB)

    De Angelis, L. [Dipartimento di Fisica, Università degli Studi “Federico II” di Napoli,Complesso Universitario Monte S. Angelo ed. 6, via Cintia, 80126 Napoli (Italy); Gionti, S.J.G. [Specola Vaticana, Vatican City, V-00120, Vatican City State and Vatican Observatory Research Group, Steward Observatory, The University Of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721 (United States); Marotta, R.; Pezzella, F. [Istituto Nazionale di Fisica Nucleare, Sezione di Napoli,Complesso Universitario di Monte S. Angelo ed. 6, via Cintia, 80126 Napoli (Italy)

    2014-04-28

    Aimed to a deeper comprehension of a manifestly T-dual invariant formulation of string theory, in this paper a detailed comparison between the non-covariant action proposed by Tseytlin and the covariant one proposed by Hull is done. These are obtained by making both the string coordinates and their duals explicitly appear, on the same footing, in the world-sheet action, so “doubling” the string coordinates along the compact dimensions. After a discussion on the nature of the constraints in both the models and the relative quantization, it results that the string coordinates and their duals behave like “non-commuting” phase space coordinates but their expressions in terms of Fourier modes generate the oscillator algebra of the standard bosonic string. A proof of the equivalence of the two formulations is given. Furthermore, open-string solutions are also discussed.

  18. Comparing double string theory actions

    International Nuclear Information System (INIS)

    De Angelis, L.; Gionti, S.J.G.; Marotta, R.; Pezzella, F.

    2014-01-01

    Aimed to a deeper comprehension of a manifestly T-dual invariant formulation of string theory, in this paper a detailed comparison between the non-covariant action proposed by Tseytlin and the covariant one proposed by Hull is done. These are obtained by making both the string coordinates and their duals explicitly appear, on the same footing, in the world-sheet action, so “doubling” the string coordinates along the compact dimensions. After a discussion on the nature of the constraints in both the models and the relative quantization, it results that the string coordinates and their duals behave like “non-commuting” phase space coordinates but their expressions in terms of Fourier modes generate the oscillator algebra of the standard bosonic string. A proof of the equivalence of the two formulations is given. Furthermore, open-string solutions are also discussed

  19. Fast Searching in Packed Strings

    DEFF Research Database (Denmark)

    Bille, Philip

    2009-01-01

    Given strings P and Q the (exact) string matching problem is to find all positions of substrings in Q matching P. The classical Knuth-Morris-Pratt algorithm [SIAM J. Comput., 1977] solves the string matching problem in linear time which is optimal if we can only read one character at the time....... However, most strings are stored in a computer in a packed representation with several characters in a single word, giving us the opportunity to read multiple characters simultaneously. In this paper we study the worst-case complexity of string matching on strings given in packed representation. Let m...... word-RAM with logarithmic word size we present an algorithm using time O(n/log(sigma) n + m + occ) Here occ is the number of occurrences of P in Q. For m = o(n) this improves the O(n) bound...

  20. Perspectives of Students’ Behavior Towards Mobile Learning (M-learning in Egypt: an Extension of the UTAUT Model

    Directory of Open Access Journals (Sweden)

    R. A. Ali

    2016-08-01

    Full Text Available The rapid development of third-generation (3G mobile technologies has led to the emergence of a new kind of learning called mobile learning (m-learning. M-learning means the use of mobile devices to access learning materials at anytime and anywhere with the aid of mobile terminals and networks. This paper explores the possibility of applying m-learning for schools in Egypt through a proposed model of acceptance factors that may affect the students’ intentions to adopt m-learning. We use the original model of Unified Theory of Acceptance and Use of Technology (UTAUT and extended it with three new factors mobility, interactivity, and enjoyment.

  1. Classical theory of radiating strings

    Science.gov (United States)

    Copeland, Edmund J.; Haws, D.; Hindmarsh, M.

    1990-01-01

    The divergent part of the self force of a radiating string coupled to gravity, an antisymmetric tensor and a dilaton in four dimensions are calculated to first order in classical perturbation theory. While this divergence can be absorbed into a renormalization of the string tension, demanding that both it and the divergence in the energy momentum tensor vanish forces the string to have the couplings of compactified N = 1 D = 10 supergravity. In effect, supersymmetry cures the classical infinities.

  2. Cosmic strings and galaxy formation

    International Nuclear Information System (INIS)

    Kibble, T.W.B.

    1986-01-01

    The evolution of a system of strings created at a phase transition early in the history of the universe is reviewed. The two possible end points are a string-dominated universe, which behaves much like a matter-dominated one, and a scaling solution, in which the persistence length of the system of strings scales with the horizon distance. The latter is the basis for a very attractive theory of galaxy formation. (Auth.)

  3. Domain Walls with Strings Attached

    Energy Technology Data Exchange (ETDEWEB)

    Shmakova, Marina

    2001-08-20

    We have constructed a bulk and brane action of IIA theory which describes a pair of BPS domain walls on S{sub 1}/Z{sub 2}, with strings attached. The walls are given by two orientifold O8-planes with coincident D8-branes and F1-D0-strings are stretched between the walls. This static configuration satisfies all matching conditions for the string and domain wall sources and has 1/4 of unbroken supersymmetry.

  4. HIV-1 coreceptor usage prediction without multiple alignments: an application of string kernels

    Directory of Open Access Journals (Sweden)

    Laviolette François

    2008-12-01

    Full Text Available Abstract Background Human immunodeficiency virus type 1 (HIV-1 infects cells by means of ligand-receptor interactions. This lentivirus uses the CD4 receptor in conjunction with a chemokine coreceptor, either CXCR4 or CCR5, to enter a target cell. HIV-1 is characterized by high sequence variability. Nonetheless, within this extensive variability, certain features must be conserved to define functions and phenotypes. The determination of coreceptor usage of HIV-1, from its protein envelope sequence, falls into a well-studied machine learning problem known as classification. The support vector machine (SVM, with string kernels, has proven to be very efficient for dealing with a wide class of classification problems ranging from text categorization to protein homology detection. In this paper, we investigate how the SVM can predict HIV-1 coreceptor usage when it is equipped with an appropriate string kernel. Results Three string kernels were compared. Accuracies of 96.35% (CCR5 94.80% (CXCR4 and 95.15% (CCR5 and CXCR4 were achieved with the SVM equipped with the distant segments kernel on a test set of 1425 examples with a classifier built on a training set of 1425 examples. Our datasets are built with Los Alamos National Laboratory HIV Databases sequences. A web server is available at http://genome.ulaval.ca/hiv-dskernel. Conclusion We examined string kernels that have been used successfully for protein homology detection and propose a new one that we call the distant segments kernel. We also show how to extract the most relevant features for HIV-1 coreceptor usage. The SVM with the distant segments kernel is currently the best method described.

  5. Analyzing the Effectiveness of Vocabulary Knowledge Scale on Learning and Enhancing Vocabulary through Extensive Reading

    Science.gov (United States)

    Iqbal, Syeda Asima; Komal, Syeda Anila

    2017-01-01

    This research is about the effectiveness of Vocabulary Knowledge Scale after extensive reading which helps in the enhancement of global language skills especially their vocabulary. This research is an endeavor to create an awareness of its significance in language acquisition through extensive reading especially focusing on vocabulary. The…

  6. Topics in string theory and quantum gravity

    CERN Document Server

    Alvarez-Gaume, Luis

    1992-01-01

    These are the lecture notes for the Les Houches Summer School on Quantum Gravity held in July 1992. The notes present some general critical assessment of other (non-string) approaches to quantum gravity, and a selected set of topics concerning what we have learned so far about the subject from string theory. Since these lectures are long (133 A4 pages), we include in this abstract the table of contents, which should help the user of the bulletin board in deciding whether to latex and print the full file. 1-FIELD THEORETICAL APPROACH TO QUANTUM GRAVITY: Linearized gravity; Supergravity; Kaluza-Klein theories; Quantum field theory and classical gravity; Euclidean approach to Quantum Gravity; Canonical quantization of gravity; Gravitational Instantons. 2-CONSISTENCY CONDITIONS: ANOMALIES: Generalities about anomalies; Spinors in 2n dimensions; When can we expect to find anomalies?; The Atiyah-Singer Index Theorem and the computation of anomalies; Examples: Green-Schwarz cancellation mechanism and Witten's SU(2) ...

  7. Splitting strings on integrable backgrounds

    International Nuclear Information System (INIS)

    Vicedo, Benoit

    2011-05-01

    We use integrability to construct the general classical splitting string solution on R x S 3 . Namely, given any incoming string solution satisfying a necessary self-intersection property at some given instant in time, we use the integrability of the worldsheet σ-model to construct the pair of outgoing strings resulting from a split. The solution for each outgoing string is expressed recursively through a sequence of dressing transformations, the parameters of which are determined by the solutions to Birkhoff factorization problems in an appropriate real form of the loop group of SL 2 (C). (orig.)

  8. String Theory in a Nutshell

    CERN Document Server

    Kiritsis, Elias

    2007-01-01

    This book is the essential new introduction to modern string theory, by one of the world's authorities on the subject. Concise, clearly presented, and up-to-date, String Theory in a Nutshell brings together the best understood and most important aspects of a theory that has been evolving since the early 1980s. A core model of physics that substitutes one-dimensional extended ""strings"" for zero-dimensional point-like particles (as in quantum field theory), string theory has been the leading candidate for a theory that would successfully unify all fundamental forces of nature, includin

  9. Evolution of cosmic string networks

    International Nuclear Information System (INIS)

    Albrecht, A.; Turok, N.; Princeton Univ., NJ

    1989-06-01

    We summarize our new results on cosmic strings. These results include: the application of non-equilibrium statistical mechanics to cosmic string evolution, a simple ''one scale'' model for the long strings which has a great deal of predictive power, results from large scale numerical simulations, and a discussion of the observational consequences of our results. An upper bond on Gμ of approximately 10 -7 emerges from the millisecond pulsar gravity wave bound. We discuss how numerical uncertainties affect this. Any changes which weaken the bound would probably also give the long strings the dominant role in producing observational consequences. 22 refs

  10. The ABCDEFG of Little Strings

    OpenAIRE

    Haouzi, Nathan; Kozçaz, Can

    2017-01-01

    Starting from type IIB string theory on an $ADE$ singularity, the (2,0) little string arises when one takes the string coupling $g_s$ to 0. In this setup, we give a unified description of the codimension-two defects of the little string, for any simple Lie algebra ${\\mathfrak{g}}$. Geometrically, these are D5 branes wrapping 2-cycles of the singularity. Equivalently, the defects are specified by a certain set of weights of $^L {\\mathfrak{g}}$, the Langlands dual of ${\\mathfrak{g}}$. As a firs...

  11. A primer on string theory

    CERN Document Server

    Schomerus, Volker

    2017-01-01

    Since its conception in the 1960s, string theory has been hailed as one of the most promising routes we have to unify quantum mechanics and general relativity. This book provides a concise introduction to string theory explaining central concepts, mathematical tools and covering recent developments in physics including compactifications and gauge/string dualities. With string theory being a multidisciplinary field interfacing with high energy physics, mathematics and quantum field theory, this book is ideal for both students with no previous knowledge of the field and scholars from other disciplines who are looking for an introduction to basic concepts.

  12. Strings, Branes and Symmetries

    International Nuclear Information System (INIS)

    Westerberg, A.

    1997-01-01

    Recent dramatic progress in the understanding of the non-perturbative structure of superstring theory shows that extended objects of various kinds, collectively referred to as p-branes, are an integral part of the theory. In this thesis, comprising an introductory text and seven appended research papers, we study various aspects of p-branes with relevance for superstring theory. The first part of the introductory text is a brief review of string theory focussing on the role of p-branes. In particular, we consider the so-called D-branes which currently are attracting a considerable amount of attention. The purpose of this part is mainly to put into context the results of paper 4, 5 and 6 concerning action functionals describing the low-energy dynamics of D-branes. The discussion of perturbative string theory given in this part of the introduction is also intended to provide some background to paper 2 which contains an application of the Reggeon-sewing approach to the construction of string vertices. The second part covers a rather different subject, namely higher-dimensional loop algebras and their cohomology, with the aim of facilitating the reading of papers 1, 3 and 7. The relation to p-branes is to be found in paper 1 where we introduce a certain higher-dimensional generalization of the loop algebra and discuss its potential applicability as a symmetry algebra for p-branes. Papers 3 and 7 are mathematically oriented out-growths of this paper addressing the issue of realizing algebras of this kind, known in physics as current algebras, in terms of pseudo differential operators (PSDOs). The main result of paper 3 is a proof of the equivalence between certain Lie-algebra cocycles on the space of second-quantizable PSDOs

  13. Drill string gas data

    Energy Technology Data Exchange (ETDEWEB)

    Siciliano, E.R.

    1998-05-12

    Data and supporting documentation were compiled and analyzed for 26 cases of gas grab samples taken during waste-tank core sampling activities between September 1, 1995 and December 31, 1997. These cases were tested against specific criteria to reduce uncertainties associated with in-tank sampling location and conditions. Of the 26 possible cases, 16 qualified as drill-string grab samples most likely to represent recently released waste gases. The data from these 16 ``confirmed`` cases were adjusted to remove non-waste gas contributions from core-sampling activities (argon or nitrogen purge), the atmospheric background, and laboratory sampler preparation (helium). The procedure for subtracting atmospheric, laboratory, and argon purge gases was unambiguous. No reliable method for determining the exact amount of nitrogen purge gas was established. Thus, the final set of ``Adjusted`` drill string gas data for the 6 nitrogen-purged cases had a greater degree of uncertainty than the final results for the 10 argon-purged cases. Including the appropriate amounts of uncertainty, this final set of data was added to the set of high-quality results from the Retained Gas Sampler (RGS), and good agreement was found for the N{sub 2}, H{sub 2}, and N{sub 2}O mole fractions sampled from common tanks. These results indicate that under favorable sampling conditions, Drill-String (DS) grab samples can provide reasonably accurate information about the dominant species of released gas. One conclusion from this set of total gas data is that the distribution of the H{sub 2} mole fractions is bimodal in shape, with an upper bound of 78%.

  14. String-inspired cosmology

    International Nuclear Information System (INIS)

    Wands, David

    2002-01-01

    I discuss cosmological models either derived from, or inspired by, string theory or M-theory. In particular, I discuss solutions in the low-energy effective theory and the role of the dilaton, moduli and antisymmetric form fields in the dimensionally reduced effective action. The pre-big-bang model is an attempt to use cosmological solutions to make observational predictions. I then discuss the effective theory of gravity found in recent braneworld models where we live on a 3-brane embedded in a five-dimensional spacetime and how the study of cosmological perturbations may enable us to test these ideas

  15. Nuclear fuel string assembly

    International Nuclear Information System (INIS)

    Ip, A.K.; Koyanagi, K.; Tarasuk, W.R.

    1976-01-01

    A method of fabricating rodded fuels suitable for use in pressure tube type reactors and in pressure vessel type reactors is described. Fuel rods are secured as an inner and an outer sub-assembly, each rod attached between mounting rings secured to the rod ends. The two sub-assemblies are telescoped together and positioned by spaced thimbles located between them to provide precise positioning while permittng differential axial movement between the sub-assemblies. Such sub-assemblies are particularly suited for mounting as bundle strings. The method provides particular advantages in the assembly of annular-section fuel pins, which includes booster fuel containing enriched fuel material. (LL)

  16. Sequestering in String Theory

    Energy Technology Data Exchange (ETDEWEB)

    Kachru, Shamit; McAllister, Liam; Sundrum, Raman

    2007-04-04

    We study sequestering, a prerequisite for flavor-blind supersymmetry breaking in several high-scale mediation mechanisms, in compactifications of type IIB string theory. We find that although sequestering is typically absent in unwarped backgrounds, strongly warped compactifications do readily sequester. The AdS/CFT dual description in terms of conformal sequestering plays an important role in our analysis, and we establish how sequestering works both on the gravity side and on the gauge theory side. We pay special attention to subtle compactification effects that can disrupt sequestering. Our result is a step toward realizing an appealing pattern of soft terms in a KKLT compactification.

  17. Sequestering in string theory

    International Nuclear Information System (INIS)

    Kachru, Shamit; McAllister, Liam; Sundrum, Raman

    2007-01-01

    We study sequestering, a prerequisite for flavor-blind supersymmetry breaking in several high-scale mediation mechanisms, in compactifications of type IIB string theory. We find that although sequestering is typically absent in unwarped backgrounds, strongly warped compactifications do readily sequester. The AdS/CFT dual description in terms of conformal sequestering plays an important role in our analysis, and we establish how sequestering works both on the gravity side and on the gauge theory side. We pay special attention to subtle compactification effects that can disrupt sequestering. Our result is a step toward realizing an appealing pattern of soft terms in a KKLT compactification

  18. Transmutations for Strings

    Directory of Open Access Journals (Sweden)

    Amin Boumenir

    2008-07-01

    Full Text Available We investigate the existence and representation of transmutations, also known as transformation operators, for strings. Using measure theory and functional analytic methods we prove their existence and study their representation. We show that in general they are not close to unity since their representation does not involve a Volterra operator but rather the eigenvalue parameter. We also obtain conditions under which the transmutation is either a bounded or a compact operator. Explicit examples show that they cannot be reduced to Volterra type operators.  

  19. New ambitwistor string theories

    Energy Technology Data Exchange (ETDEWEB)

    Casali, Eduardo [DAMTP, University of Cambridge,Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Geyer, Yvonne; Mason, Lionel; Monteiro, Ricardo [Mathematical Institute, University of Oxford,Woodstock Road, Oxford OX2 6GG (United Kingdom); Roehrig, Kai A. [DAMTP, University of Cambridge,Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

    2015-11-05

    We describe new ambitwistor string theories that give rise to the recent amplitude formulae for Einstein-Yang-Mills, (Dirac)-Born-Infeld, Galileons and others introduced by Cachazo, He and Yuan. In the case of the Einstein-Yang-Mills amplitudes, an important role is played by a novel worldsheet conformal field theory that provides the appropriate colour factors precisely without the spurious multitrace terms of earlier models that had to be ignored by hand. This is needed to obtain the correct multitrace terms that arise when Yang-Mills is coupled to gravity.

  20. CT analysis of bowed stringed instruments.

    Science.gov (United States)

    Sirr, S A; Waddle, J R

    1997-06-01

    To determine the utility of computed tomography (CT) for the noninvasive evaluation of bowed stringed instruments. Thirty-seven instruments that ranged in quality from student instruments to exquisite Stradivarius violins were analyzed with CT. Accuracy of thickness measurements was determined from 24 measurements of cross-sectional pieces sawed from a student violin. Accuracy of density measurements was determined from 328 CT attenuation measurements of 16 woods used in stringed instruments. Substantial differences of normal structure were noted between the masterpieces crafted in Cremona, Italy, and factory-produced student instruments. Unexpected defects were detected in nine of 14 instruments older than 100 years and ranged from a few wormholes (eight instruments) to many wormholes and extensive repair (one violin). CT thickness and attenuation measurements correlated well to the line of identity with actual measurements (P < .0001). Two cellos and a viola have been constructed from CT-derived information. The viola was awarded a gold medal at a recent international competition. CT provides the modern luthier and acoustic scientist with a unique tool for characterization of normal structure, defects, and repair and for accurate measurements of wood thickness and density. CT-derived information aids in the replication of original masterpieces. CT evaluation may have an important role in the valuation, insurance, and identification of valuable stringed instruments.

  1. Topological insulators and superconductors from string theory

    International Nuclear Information System (INIS)

    Ryu, Shinsei; Takayanagi, Tadashi

    2010-01-01

    Topological insulators and superconductors in different spatial dimensions and with different discrete symmetries have been fully classified recently, revealing a periodic structure for the pattern of possible types of topological insulators and superconductors, both in terms of spatial dimensions and in terms of symmetry classes. It was proposed that K theory is behind the periodicity. On the other hand, D-branes, a solitonic object in string theory, are also known to be classified by K theory. In this paper, by inspecting low-energy effective field theories realized by two parallel D-branes, we establish a one-to-one correspondence between the K-theory classification of topological insulators/superconductors and D-brane charges. In addition, the string theory realization of topological insulators and superconductors comes naturally with gauge interactions, and the Wess-Zumino term of the D-branes gives rise to a gauge field theory of topological nature, such as ones with the Chern-Simons term or the θ term in various dimensions. This sheds light on topological insulators and superconductors beyond noninteracting systems, and the underlying topological field theory description thereof. In particular, our string theory realization includes the honeycomb lattice Kitaev model in two spatial dimensions, and its higher-dimensional extensions. Increasing the number of D-branes naturally leads to a realization of topological insulators and superconductors in terms of holography (AdS/CFT).

  2. Energy in a String Wave

    Science.gov (United States)

    Ng, Chiu-king

    2010-01-01

    When one end of a taut horizontal elastic string is shaken repeatedly up and down, a transverse wave (assume sine waveform) will be produced and travel along it. College students know this type of wave motion well. They know when the wave passes by, each element of the string will perform an oscillating up-down motion, which in mechanics is termed…

  3. Experimenting with String Musical Instruments

    Science.gov (United States)

    LoPresto, Michael C.

    2012-01-01

    What follows are several investigations involving string musical instruments developed for and used in a "Science of Sound & Light" course. The experiments make use of a guitar, orchestral string instruments and data collection and graphing software. They are designed to provide students with concrete examples of how mathematical formulae, when…

  4. Cool Runnings For String 2

    CERN Multimedia

    2001-01-01

    String 2 is a series of superconducting magnets that are prototypes of those which will be installed in the LHC. It was cooled down to 1.9 Kelvin on September 14th. On Thursday last week, the dipoles of String 2 were successfully taken to nominal current, 11850 A.

  5. Differential formulation in string theories

    International Nuclear Information System (INIS)

    Guzzo, M.M.

    1987-01-01

    The equations of gauge invariance motion for theories of boson open strings and Neveu-Schwarz and Ramond superstring are derived. A construction for string theories using differential formalism, is introduced. The importance of BRST charge for constructing such theories and the necessity of introduction of auxiliary fields are verified. (M.C.K.) [pt

  6. Progress in string theory research

    CERN Document Server

    2016-01-01

    At the first look, the String Theory seems just an interesting and non-trivial application of the quantum mechanics and the special relativity to vibrating strings. By itself, the quantization of relativistic strings does not call the attention of the particle physicist as a significant paradigm shift. However, when the string quantization is performed by applying the standard rules of the perturbative Quantum Field Theory, one discovers that the strings in certain states have the same physical properties as the gravity in the flat space-time. Chapter one of this book reviews the construction of the thermal bosonic string and D-brane in the framework of the Thermo Field Dynamics (TFD). It briefly recalls the wellknown light-cone quantization of the bosonic string in the conformal gauge in flat space-time, and gives a bird’s eye view of the fundamental concepts of the TFD. Chapter two examines a visual model inspired by string theory, on the system of interacting anyons. Chapter three investigate the late-ti...

  7. Deformations of topological open strings

    NARCIS (Netherlands)

    Hofman, C.; Ma, Whee Ky

    Deformations of topological open string theories are described, with an emphasis on their algebraic structure. They are encoded in the mixed bulk-boundary correlators. They constitute the Hochschild complex of the open string algebra - the complex of multilinear maps on the boundary Hilbert space.

  8. Tadpole resummations in string theory

    International Nuclear Information System (INIS)

    Kitazawa, Noriaki

    2008-01-01

    While R-R tadpoles should be canceled for consistency, string models with broken supersymmetry generally have uncanceled NS-NS tadpoles. Their presence signals that the background does not solve the field equations, so that these models are in 'wrong' vacua. In this Letter we investigate, with reference to some prototype examples, whether the true values of physical quantities can be recovered resumming the NS-NS tadpoles, hence by an approach that is related to the analysis based on String Field Theory by open-closed duality. We show that, indeed, the positive classical vacuum energy of a Dp-brane of the bosonic string is exactly canceled by the negative contribution arising from tree-level tadpole resummation, in complete agreement with Sen's conjecture on open-string tachyon condensation and with the consequent analysis based on String Field Theory. We also show that the vanishing classical vacuum energy of the SO(8192) unoriented bosonic open-string theory does not receive any tree-level corrections from the tadpole resummation. This result is consistent with the fact that this (unstable) configuration is free from tadpoles of massless closed-string modes, although there is a tadpole of the closed string tachyon. The application of this method to superstring models with broken supersymmetry is also discussed

  9. String theory and water waves

    International Nuclear Information System (INIS)

    Iyer, Ramakrishnan; Johnson, Clifford V; Pennington, Jeffrey S

    2011-01-01

    We uncover a remarkable role that an infinite hierarchy of nonlinear differential equations plays in organizing and connecting certain c-hat <1 string theories non-perturbatively. We are able to embed the type 0A and 0B (A, A) minimal string theories into this single framework. The string theories arise as special limits of a rich system of equations underpinned by an integrable system known as the dispersive water wave hierarchy. We observe that there are several other string-like limits of the system, and conjecture that some of them are type IIA and IIB (A, D) minimal string backgrounds. We explain how these and several string-like special points arise and are connected. In some cases, the framework endows the theories with a non-perturbative definition for the first time. Notably, we discover that the Painleve IV equation plays a key role in organizing the string theory physics, joining its siblings, Painleve I and II, whose roles have previously been identified in this minimal string context.

  10. String-localized quantum fields

    International Nuclear Information System (INIS)

    Mund, Jens; Santos, Jose Amancio dos; Silva, Cristhiano Duarte; Oliveira, Erichardson de

    2009-01-01

    Full text. The principles of physics admit (unobservable) quantum fields which are localized not on points, but on strings in the sense of Mandelstam: a string emanates from a point in Minkowski space and extends to infinity in some space-like direction. This type of localization might permit the construction of new models, for various reasons: (a) in general, weaker localization implies better UV behaviour. Therefore, the class of renormalizable interactions in the string-localized has a chance to be larger than in the point-localized case; (b) for certain particle types, there are no point-localized (free) quantum fields - for example Anyons in d = 2 + 1, and Wigner's massless 'infinite spin' particles. For the latter, free string-localized quantum fields have been constructed; (c) in contrast to the point-localized case, string-localization admits covariant vector/tensor potentials for fotons and gravitons in a Hilbert space representation with positive energy. We shall present free string-localized quantum fields for various particle types, and some ideas about the perturbative construction of interacting string-localized fields. A central point will be an analogue of gauge theories, completely within a Hilbert space and without ghosts, trading gauge dependence with dependence on the direction of the localization string. In order to discuss renormalizability (item (a)), methods from microlocal analysis (wave front set and scaling degree) are needed. (author)

  11. String theory and cosmological singularities

    Indian Academy of Sciences (India)

    recent times, string theory is providing new perspectives of such singularities which may lead to an understanding of these in the standard framework of time evolution in quantum mechanics. In this article, we describe some of these approaches. Keywords. String theory; cosmological singularities. PACS Nos 11.25.

  12. String theory and particle physics

    International Nuclear Information System (INIS)

    Uranga, Angel

    2006-01-01

    I will provide a basic introduction to string theory as a unified theory of gravitational and gauge interactions. I will review recent constructions of string theory models leading at low energies to the Standard Model of particle interactions, and which include interesting new phenomenology beyond the standard model, like supersymmetry, boranes, and (possible large) extra dimensions

  13. Bianchi type I string cosmologies

    Indian Academy of Sciences (India)

    sidered to portray early universe reasonably well. Letelier [2] obtained some particular. Bianchi type I string-dust models in which at a certain epoch, strings disappear with a phase transition to an anisotropic fluid. Another Bianchi type I model has been presented by Banerjee et al [3] which obeys Takabayashi's equation of ...

  14. String theory : physics or metaphysics?

    CERN Document Server

    Veneziano, Gabriele

    2010-01-01

    I will give arguments for why the enormous progress made during the last century on understanding elementary particles and their fundamental interactions suggests strings as the truly elementary constituents of Nature. I will then address the issue of whether the string paradigm can in principle be falsified or whether it should be considered as mere metaphysics.

  15. On tadpoles and vacuum redefinitions in String Theory

    International Nuclear Information System (INIS)

    Dudas, E.; Nicolosi, M.; Pradisi, G.; Sagnotti, A.

    2005-01-01

    Tadpoles accompany, in one form or another, all attempts to realize supersymmetry breaking in String Theory, making the present constructions at best incomplete. Whereas these tadpoles are typically large, a closer look at the problem from a perturbative viewpoint has the potential of illuminating at least some of its qualitative features in String Theory. A possible scheme to this effect was proposed long ago by Fischler and Susskind, but incorporating background redefinitions in string amplitudes in a systematic fashion has long proved very difficult. In the first part of this paper, drawing from field theory examples, we thus begin to explore what one can learn by working perturbatively in a 'wrong' vacuum. While unnatural in Field Theory, this procedure presents evident advantages in String Theory, whose definition in curved backgrounds is mostly beyond reach at the present time. At the field theory level, we also identify and characterize some special choices of vacua where tadpole resummations terminate after a few contributions. In the second part we present a notable example where vacuum redefinitions can be dealt with to some extent at the full string level, providing some evidence for a new link between IIB and 0B orientifolds. We finally show that NS-NS tadpoles do not manifest themselves to lowest order in certain classes of string constructions with broken supersymmetry and parallel branes, including brane-antibrane pairs and brane supersymmetry breaking models, that therefore have UV-finite threshold corrections at one loop

  16. "Artificial grammar learning" in pigeons: a preliminary analysis.

    Science.gov (United States)

    Herbranson, Walter T; Shimp, Charles P

    2003-02-01

    An avian analogue to human artificial or synthetic grammar learning (Reber, 1967) was developed. Pigeons viewed horizontal strings of three to eight colored letters. These strings either conformed to Reber's artificial grammar or violated it in one or two locations. Pigeons categorized the letter strings as grammatical (left keypeck) or nongrammatical (right keypeck). Overall accuracy of categorization was above chance to both familiar training strings and to novel transfer strings, thereby satisfying a conventional criterion for learning an abstract concept. The results support a multiple mechanisms point of view according to which pigeons, like humans, learn both abstract concepts and specific strings, or specific parts of strings, in artificial grammar learning tasks.

  17. Poisson hierarchy of discrete strings

    Energy Technology Data Exchange (ETDEWEB)

    Ioannidou, Theodora, E-mail: ti3@auth.gr [Faculty of Civil Engineering, School of Engineering, Aristotle University of Thessaloniki, 54249, Thessaloniki (Greece); Niemi, Antti J., E-mail: Antti.Niemi@physics.uu.se [Department of Physics and Astronomy, Uppsala University, P.O. Box 803, S-75108, Uppsala (Sweden); Laboratoire de Mathematiques et Physique Theorique CNRS UMR 6083, Fédération Denis Poisson, Université de Tours, Parc de Grandmont, F37200, Tours (France); Department of Physics, Beijing Institute of Technology, Haidian District, Beijing 100081 (China)

    2016-01-28

    The Poisson geometry of a discrete string in three dimensional Euclidean space is investigated. For this the Frenet frames are converted into a spinorial representation, the discrete spinor Frenet equation is interpreted in terms of a transfer matrix formalism, and Poisson brackets are introduced in terms of the spinor components. The construction is then generalised, in a self-similar manner, into an infinite hierarchy of Poisson algebras. As an example, the classical Virasoro (Witt) algebra that determines reparametrisation diffeomorphism along a continuous string, is identified as a particular sub-algebra, in the hierarchy of the discrete string Poisson algebra. - Highlights: • Witt (classical Virasoro) algebra is derived in the case of discrete string. • Infinite dimensional hierarchy of Poisson bracket algebras is constructed for discrete strings. • Spinor representation of discrete Frenet equations is developed.

  18. Poisson hierarchy of discrete strings

    International Nuclear Information System (INIS)

    Ioannidou, Theodora; Niemi, Antti J.

    2016-01-01

    The Poisson geometry of a discrete string in three dimensional Euclidean space is investigated. For this the Frenet frames are converted into a spinorial representation, the discrete spinor Frenet equation is interpreted in terms of a transfer matrix formalism, and Poisson brackets are introduced in terms of the spinor components. The construction is then generalised, in a self-similar manner, into an infinite hierarchy of Poisson algebras. As an example, the classical Virasoro (Witt) algebra that determines reparametrisation diffeomorphism along a continuous string, is identified as a particular sub-algebra, in the hierarchy of the discrete string Poisson algebra. - Highlights: • Witt (classical Virasoro) algebra is derived in the case of discrete string. • Infinite dimensional hierarchy of Poisson bracket algebras is constructed for discrete strings. • Spinor representation of discrete Frenet equations is developed.

  19. Testing string theory at LHC?

    CERN Multimedia

    CERN. Geneva

    2002-01-01

    A theory with such mathematical beauty cannot be wrong: this is one of the main arguments in favour of string theory, which unifies all known physical theories of fundamental interactions in a single coherent description of the universe. But no one has ever observed strings, not even indirectly, nor the space of extra dimensions where they live. However there are good reasons to believe that the 'hidden' dimensions of string theory may be much larger than what we thought in the past and that they may be within experimental reach in the near future - together with the strings themselves. In my talk, I will give an elementary introduction of string theory and describe the main experimental predictions.Organiser(s): Jasper Kirkby / EP DivisionNote: Tea & coffee will be served at 16.00 hrs.

  20. Oscillons from string moduli

    Science.gov (United States)

    Antusch, Stefan; Cefalà, Francesco; Krippendorf, Sven; Muia, Francesco; Orani, Stefano; Quevedo, Fernando

    2018-01-01

    A generic feature of string compactifications is the presence of many scalar fields, called moduli. Moduli are usually displaced from their post-inflationary minimum during inflation. Their relaxation to the minimum could lead to the production of oscillons: localised, long-lived, non-linear excitations of the scalar fields. Here we discuss under which conditions oscillons can be produced in string cosmology and illustrate their production and potential phenomenology with two explicit examples: the case of an initially displaced volume modulus in the KKLT scenario and the case of a displaced blow-up Kähler modulus in the Large Volume Scenario (LVS). One, in principle, observable consequence of oscillon dynamics is the production of gravitational waves which, contrary to those produced from preheating after high scale inflation, could have lower frequencies, closer to the currently observable range. We also show that, for the considered parameter ranges, oscillating fibre and volume moduli do not develop any significant non-perturbative dynamics. Furthermore, we find that the vacua in the LVS and the KKLT scenario are stable against local overshootings of the field into the decompatification region, which provides an additional check on the longevity of these metastable configurations.

  1. Quark Confinement and Strings

    Science.gov (United States)

    't Hooft, Gerardus

    QCD was proposed as a theory for the strong interactions long before we had any idea as to how it could be that its fundamental constituents, the quarks, are never seen as physical particles. Massless gluons also do not exist as free particles. How can this be explained? The first indication that this question had to be considered in connection with the topological structure of a gauge theory came when Nielsen and Olesen observed the occurrence of stable magnetic vortex structures [1] in the Abelian Higgs model. Expanding on such ideas, the magnetic monopole solution was found [2]. Other roundabout attempts to understand confinement involve instantons. Today, we have better interpretations of these topological structures, including a general picture of the way they do lead to unbound potentials confining quarks. It is clear that these unbound potentials can be ascribed to a string-like structure of the vortices formed by the QCD field lines. Can string theory be used to analyze QCD? Many researchers think so. The leading expert on this is Sacha Polyakov. In his instructive account he adds how he experienced the course of events in Gauge Theory, emphasizing the fact that quite a few discoveries often ascribed to researchers from the West, actually were made independently by scientists from the Soviet Union…

  2. String dualities and superpotential

    International Nuclear Information System (INIS)

    Ha, Tae-Won

    2010-09-01

    The main objective of this thesis is the computation of the superpotential induced by D5- branes in the type IIB string theory and by five-branes in the heterotic string theory. Both superpotentials have the same functional form which is the chain integral of the holomorphic three-form. Using relative (co)homology we can unify the flux and brane superpotential. The chain integral can be seen as an example of the Abel-Jacobi map. We discuss many structures such as mixed Hodge structure which allows for the computation of Picard-Fuchs differential equations crucial for explicit computations. We blow up the Calabi-Yau threefold along the submanifold wrapped by the brane to obtain geometrically more appropriate configuration. The resulting geometry is non-Calabi-Yau and we have a canonically given divisor. This blown-up geometry makes it possible to restrict our attention to complex structure deformations. However, the direct computation is yet very difficult, thus the main tool for computation will be the lift of the brane configuration to a F-theory compactification. In F-theory, since complex structure, brane and, if present, bundlemoduli are all contained in the complex structure moduli space of the elliptic Calabi-Yau fourfold, the computation can be dramatically simplified. The heterotic/F-theory duality is extended to include the blow-up geometry and thereby used to give the blow-up geometry amore physical meaning. (orig.)

  3. String dualities and superpotential

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Tae-Won

    2010-09-15

    The main objective of this thesis is the computation of the superpotential induced by D5- branes in the type IIB string theory and by five-branes in the heterotic string theory. Both superpotentials have the same functional form which is the chain integral of the holomorphic three-form. Using relative (co)homology we can unify the flux and brane superpotential. The chain integral can be seen as an example of the Abel-Jacobi map. We discuss many structures such as mixed Hodge structure which allows for the computation of Picard-Fuchs differential equations crucial for explicit computations. We blow up the Calabi-Yau threefold along the submanifold wrapped by the brane to obtain geometrically more appropriate configuration. The resulting geometry is non-Calabi-Yau and we have a canonically given divisor. This blown-up geometry makes it possible to restrict our attention to complex structure deformations. However, the direct computation is yet very difficult, thus the main tool for computation will be the lift of the brane configuration to a F-theory compactification. In F-theory, since complex structure, brane and, if present, bundlemoduli are all contained in the complex structure moduli space of the elliptic Calabi-Yau fourfold, the computation can be dramatically simplified. The heterotic/F-theory duality is extended to include the blow-up geometry and thereby used to give the blow-up geometry amore physical meaning. (orig.)

  4. Parabosonic string and space-time non-commutativity

    Energy Technology Data Exchange (ETDEWEB)

    Seridi, M. A.; Belaloui, N. [Laboratoire de Physique Mathematique et Subatomique, Universite Mentouri Constantine (Algeria)

    2012-06-27

    We investigate the para-quantum extension of the bosonic strings in a non-commutative space-time. We calculate the trilinear relations between the mass-center variables and the modes and we derive the Virasoro algebra where a new anomaly term due to the non-commutativity is obtained.

  5. Twist Field as Three String Interaction Vertex in Light Cone String Field Theory

    OpenAIRE

    Kishimoto, Isao; Moriyama, Sanefumi; Teraguchi, Shunsuke

    2006-01-01

    It has been suggested that matrix string theory and light-cone string field theory are closely related. In this paper, we investigate the relation between the twist field, which represents string interactions in matrix string theory, and the three-string interaction vertex in light-cone string field theory carefully. We find that the three-string interaction vertex can reproduce some of the most important OPEs satisfied by the twist field.

  6. Oriented open-closed string theory revisited

    International Nuclear Information System (INIS)

    Zwiebach, B.

    1998-01-01

    String theory on D-brane backgrounds is open-closed string theory. Given the relevance of this fact, we give details and elaborate upon our earlier construction of oriented open-closed string field theory. In order to incorporate explicitly closed strings, the classical sector of this theory is open strings with a homotopy associative A ∞ algebraic structure. We build a suitable Batalin-Vilkovisky algebra on moduli spaces of bordered Ricmann surfaces, the construction of which involves a few subtleties arising from the open string punctures and cyclicity conditions. All vertices coupling open and closed strings through disks are described explicitly. Subalgebras of the algebra of surfaces with boundaries are used to discuss symmetries of classical open string theory induced by the closed string sector, and to write classical open string field theory on general closed string backgrounds. We give a preliminary analysis of the ghost-dilaton theorem. copyright 1998 Academic Press, Inc

  7. Exposure therapy augmentation: A review and extension of techniques informed by an inhibitory learning approach.

    Science.gov (United States)

    Weisman, Jaclyn S; Rodebaugh, Thomas L

    2018-02-01

    Although exposure therapy is often considered a gold standard behavioral intervention for pathological anxiety, questions remain surrounding the mechanisms underlying exposure interventions, and some individuals are characterized by suboptimal treatment outcomes. Recently, a formulation known as the inhibitory learning theory, which is grounded in basic science principles of extinction learning and memory, has been proposed to provide a more parsimonious mechanistic explanation for the effects of exposure than previous, habituation-based models [Craske, M.G., Kircanski, K., Zelikowsky, M., Mystkowski, J., Chowdhury, N., & Baker, A. 2008. Optimizing inhibitory learning during exposure therapy. Behaviour Research and Therapy, 46, 5-27; Craske, M.G., Treanor, M., Conway, C.C., Zbozinek, T., & Vervliet, B. 2014. Maximizing exposure therapy: An inhibitory learning approach. Behaviour Research and Therapy, 58, 10-23]. Strategies informed by this theory are proposed to maximize extinction learning by fostering the development of new, non-threat associations between stimuli in memory and enhancing the accessibility and retrieval of these safety-based associations. This comprehensive review serves as a critical examination of the empirical literature regarding major tenets of inhibitory learning theory and the potential for such techniques to augment exposure therapy for anxiety disorders. Limitations of the extant research, as well as potential future directions, are explored. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Conformal techniques in string theory and string field theory

    International Nuclear Information System (INIS)

    Giddings, S.B.

    1987-01-01

    The application of some conformal and Riemann surface techniques to string theory and string field theory is described. First a brief review of Riemann surface techniques and of the Polyakov approach to string theory is presented. This is followed by a discussion of some features of string field theory and of its Feynman rules. Specifically, it is shown that the Feynman diagrams for Witten's string field theory respect modular invariance, and in particular give a triangulation of moduli space. The Polyakov formalism is then used to derive the Feynman rules that should follow from this theory upon gauge-fixing. It should also be possible to apply this derivation to deduce the Feynman rules for other gauge-fixed string field theories. Following this, Riemann surface techniques are turned to the problem of proving the equivalence of the Polyakov and light-cone formalisms. It is first shown that the light-cone diagrams triangulate moduli space. Then the Polyakov measure is worked out for these diagrams, and shown to equal that deduced from the light-cone gauge fixed formalism. Also presented is a short description of the comparison of physical states in the two formalisms. The equivalence of the two formalisms in particular constitutes a proof of the unitarity of the Polyakov framework for the closed bosonic string

  9. Genotype List String: a grammar for describing HLA and KIR genotyping results in a text string.

    Science.gov (United States)

    Milius, R P; Mack, S J; Hollenbach, J A; Pollack, J; Heuer, M L; Gragert, L; Spellman, S; Guethlein, L A; Trachtenberg, E A; Cooley, S; Bochtler, W; Mueller, C R; Robinson, J; Marsh, S G E; Maiers, M

    2013-08-01

    Knowledge of an individual's human leukocyte antigen (HLA) genotype is essential for modern medical genetics, and is crucial for hematopoietic stem cell and solid-organ transplantation. However, the high levels of polymorphism known for the HLA genes make it difficult to generate an HLA genotype that unambiguously identifies the alleles that are present at a given HLA locus in an individual. For the last 20 years, the histocompatibility and immunogenetics community has recorded this HLA genotyping ambiguity using allele codes developed by the National Marrow Donor Program (NMDP). While these allele codes may have been effective for recording an HLA genotyping result when initially developed, their use today results in increased ambiguity in an HLA genotype, and they are no longer suitable in the era of rapid allele discovery and ultra-high allele polymorphism. Here, we present a text string format capable of fully representing HLA genotyping results. This Genotype List (GL) String format is an extension of a proposed standard for reporting killer-cell immunoglobulin-like receptor (KIR) genotype data that can be applied to any genetic data that use a standard nomenclature for identifying variants. The GL String format uses a hierarchical set of operators to describe the relationships between alleles, lists of possible alleles, phased alleles, genotypes, lists of possible genotypes, and multilocus unphased genotypes, without losing typing information or increasing typing ambiguity. When used in concert with appropriate tools to create, exchange, and parse these strings, we anticipate that GL Strings will replace NMDP allele codes for reporting HLA genotypes. © 2013 The Authors. Tissue Antigens published by John Wiley & Sons Ltd.

  10. Deterministic indexing for packed strings

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li; Skjoldjensen, Frederik Rye

    2017-01-01

    Given a string S of length n, the classic string indexing problem is to preprocess S into a compact data structure that supports efficient subsequent pattern queries. In the deterministic variant the goal is to solve the string indexing problem without any randomization (at preprocessing time...... or query time). In the packed variant the strings are stored with several character in a single word, giving us the opportunity to read multiple characters simultaneously. Our main result is a new string index in the deterministic and packed setting. Given a packed string S of length n over an alphabet σ......, we show how to preprocess S in O(n) (deterministic) time and space O(n) such that given a packed pattern string of length m we can support queries in (deterministic) time O (m/α + log m + log log σ), where α = w/log σ is the number of characters packed in a word of size w = θ(log n). Our query time...

  11. Fingerprints in compressed strings

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li; Cording, Patrick Hagge

    2017-01-01

    In this paper we show how to construct a data structure for a string S of size N compressed into a context-free grammar of size n that supports efficient Karp–Rabin fingerprint queries to any substring of S. That is, given indices i and j, the answer to a query is the fingerprint of the substring S......[i,j]. We present the first O(n) space data structures that answer fingerprint queries without decompressing any characters. For Straight Line Programs (SLP) we get O(log⁡N) query time, and for Linear SLPs (an SLP derivative that captures LZ78 compression and its variations) we get O(log⁡log⁡N) query time...

  12. Field theory and strings

    International Nuclear Information System (INIS)

    Bonara, L.; Cotta-Ramusino, P.; Rinaldi, M.

    1987-01-01

    It is well-known that type I and heterotic superstring theories have a zero mass spectrum which correspond to the field content of N=1 supergravity theory coupled to supersymmetric Yang-Mills theory in 10-D. The authors study the field theory ''per se'', in the hope that simple consistency requirements will determine the theory completely once one knows the field content inherited from string theory. The simplest consistency requirements are: N=1 supersymmetry; and absence of chiral anomalies. This is what the authors discuss in this paper here leaving undetermined the question of the range of validity of the resulting field theory. As is known, a model of N=1 supergravity (SUGRA) coupled to supersymmetric Yang-Mills (SYM) theory was known in the form given by Chapline and Manton. The coupling of SUGRA to SYM was determined by the definition of the ''field strength'' 3-form H in this paper

  13. On the Classical String Solutions and String/Field Theory Duality

    OpenAIRE

    Aleksandrova, D.; Bozhilov, P.

    2003-01-01

    We classify almost all classical string configurations, considered in the framework of the semi-classical limit of the string/gauge theory duality. Then, we describe a procedure for obtaining the conserved quantities and the exact classical string solutions in general string theory backgrounds, when the string embedding coordinates depend non-linearly on the worldsheet time parameter.

  14. String Formatting Considered Harmful for Novice Programmers

    Science.gov (United States)

    Hughes, Michael C.; Jadud, Matthew C.; Rodrigo, Ma. Mercedes T.

    2010-01-01

    In Java, "System.out.printf" and "String.format" consume a specialised kind of string commonly known as a format string. In our study of first-year students at the Ateneo de Manila University, we discovered that format strings present a substantial challenge for novice programmers. Focusing on their first laboratory we found…

  15. Test particle trajectories near cosmic strings

    Indian Academy of Sciences (India)

    We present a detailed analysis of the motion of test particle in the gravitational field of cosmic strings in different situations using the Hamilton–Jacobi (H–J) formalism. We have discussed the trajectories near static cosmic string, cosmic string in Brans–Dicke theory and cosmic string in dilaton gravity.

  16. Interaction of cosmic strings with gravitational waves

    International Nuclear Information System (INIS)

    Frolov, V.P.; Garfinkle, D.

    1990-01-01

    We find solutions of Einstein's equation representing a gravitational wave interacting with a cosmic-string traveling wave. The motion of test cosmic strings in the gravitational field of a cosmic-string traveling wave is also examined. A solution representing traveling waves on several parallel cosmic strings is also found

  17. String matching with variable length gaps

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li; Vildhøj, Hjalte Wedel

    2012-01-01

    We consider string matching with variable length gaps. Given a string T and a pattern P consisting of strings separated by variable length gaps (arbitrary strings of length in a specified range), the problem is to find all ending positions of substrings in T that match P. This problem is a basic...

  18. Introducing Inmates to Extension through Financial Education and Experiential Learning Tools

    Science.gov (United States)

    Richel, Karen

    2013-01-01

    Research shows that in order to reduce recidivism rates in prisons, financial education and other life skills should be a mandatory topic in our prison systems. By creating a learning environment conducive to the specialized needs of this audience, an inmate's ability to set goals, recognize wants and needs, maintain bank accounts, create a…

  19. Lessons Learned Developing an Extension-Based Training Program for Farm Labor Supervisors

    Science.gov (United States)

    Roka, Fritz M.; Thissen, Carlene A.; Monaghan, Paul F.; Morera, Maria C.; Galindo-Gonzalez, Sebastian; Tovar-Aguilar, Jose Antonio

    2017-01-01

    This article outlines a four-step model for developing a training program for farm labor supervisors. The model draws on key lessons learned during the development of the University of Florida Institute of Food and Agricultural Sciences Farm Labor Supervisor Training program. The program is designed to educate farm supervisors on farm labor laws…

  20. User Acceptance of YouTube for Procedural Learning: An Extension of the Technology Acceptance Model

    Science.gov (United States)

    Lee, Doo Young; Lehto, Mark R.

    2013-01-01

    The present study was framed using the Technology Acceptance Model (TAM) to identify determinants affecting behavioral intention to use YouTube. Most importantly, this research emphasizes the motives for using YouTube, which is notable given its extrinsic task goal of being used for procedural learning tasks. Our conceptual framework included two…

  1. Extensive television viewing and the development of attention and learning difficulties during adolescence.

    Science.gov (United States)

    Johnson, Jeffrey G; Cohen, Patricia; Kasen, Stephanie; Brook, Judith S

    2007-05-01

    To investigate the association of television viewing with educational and intellectual outcomes during adolescence and early adulthood. Prospective epidemiological study. Families participating in the Children in the Community Study, a prospective longitudinal investigation, were interviewed at mean offspring ages 14, 16, and 22 years. A community-based sample of 678 families from upstate New York. Television viewing, attention difficulties, learning difficulties, and educational achievement during adolescence and early adulthood. The Disorganizing Poverty Interview and age-appropriate versions of the Diagnostic Interview Schedule for Children. Frequent television viewing during adolescence was associated with elevated risk for subsequent attention and learning difficulties after family characteristics and prior cognitive difficulties were controlled. Youths who watched 1 or more hours of television per day at mean age 14 years were at elevated risk for poor homework completion, negative attitudes toward school, poor grades, and long-term academic failure. Youths who watched 3 or more hours of television per day were the most likely to experience these outcomes. In addition, youths who watched 3 or more hours of television per day were at elevated risk for subsequent attention problems and were the least likely to receive postsecondary education. There was little evidence of bidirectionality in the association of television viewing with attention and learning difficulties. Frequent television viewing during adolescence may be associated with risk for development of attention problems, learning difficulties, and adverse long-term educational outcomes.

  2. Investigating Demotivation in Learning English: An Extension to Sakai and Kikuchi's (2009) Framework

    Science.gov (United States)

    Krishnan, K. Sarojani Devi; Aziz, Jalan Raja Muda Abdul; Pathan, Zahid Hussain

    2013-01-01

    The aim of this research is to investigate the factors of demotivation in L2 learning of Pakistani undergraduates at the University of Balochistan, Quetta. A mixed-methods research design was employed in this study to explore the factors of demotivation. Quantitative data was obtained from the responses of a population of 116 first semester…

  3. Geometry, topology, and string theory

    Energy Technology Data Exchange (ETDEWEB)

    Varadarajan, Uday [Univ. of California, Berkeley, CA (United States)

    2003-01-01

    A variety of scenarios are considered which shed light upon the uses and limitations of classical geometric and topological notions in string theory. The primary focus is on situations in which D-brane or string probes of a given classical space-time see the geometry quite differently than one might naively expect. In particular, situations in which extra dimensions, non-commutative geometries as well as other non-local structures emerge are explored in detail. Further, a preliminary exploration of such issues in Lorentzian space-times with non-trivial causal structures within string theory is initiated.

  4. STRING v9.1

    DEFF Research Database (Denmark)

    Franceschini, A.; Simonovic, M.; Roth, A.

    2013-01-01

    data is desirable, including lower-quality data and/or computational predictions. The STRING database (http://string-db.org/) aims to provide such a global perspective for as many organisms as feasible. Known and predicted associations are scored and integrated, resulting in comprehensive protein...... networks covering >1100 organisms. Here, we describe the update to version 9.1 of STRING, introducing several improvements: (i) we extend the automated mining of scientific texts for interaction information, to now also include full-text articles; (ii) we entirely re-designed the algorithm for transferring...

  5. Spin chain for quantum strings

    International Nuclear Information System (INIS)

    Beisert, N.

    2005-01-01

    We review and compare the integrable structures in N=4 gauge theory and string theory on AdS 5 x S 5 . Recently, Bethe ansaetze for gauge theory/weak coupling and string theory/strong coupling were proposed to describe scaling dimensions in the su(2) subsector. Here we investigate the Bethe equations for quantum string theory, naively extrapolated to weak coupling. Excitingly, we find a spin chain Hamiltonian similar, but not equal, to the gauge theory dilatation operator. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  6. Covariant N-string amplitude

    International Nuclear Information System (INIS)

    Di Vecchia, P.; Sciuto, S.; Nakayama, R.; Petersen, J.L.; Sidenius, J.R.

    1986-11-01

    The BRST-invariant N-Reggeon vertex (for the bosonic string) previously given by us in the operator formulation is considered in more detail. In particular we present a direct derivation from the string path integral. Several crucial symmetry properties found a posteriori before, become a priori clearer in this formulation. A number of delicate points related to zero modes, cut off procedures and normal ordering prescriptions are treated in some detail. The old technique of letting the string field acquire a small dimension ε/2 → 0 + is found especially elegant. (orig.)

  7. Plucked Strings and the Harpsichord

    Science.gov (United States)

    GIORDANO, N.; WINANS, J. P.

    1999-07-01

    The excitation of a harpsichord string when it is set into motion, i.e., plucked, by a plectrum is studied. We find that the amplitude of the resulting string vibration is approximately independent of the velocity with which the key is depressed. This result is in accord with conventional wisdom, but at odds with a recent theoretical model. A more realistic theoretical treatment of the plucking process is then described, and shown to be consistent with our measurements. The experiments reveal several other interesting aspects of the plectrum-string interaction.

  8. Nonassociative gravity in string theory?

    Energy Technology Data Exchange (ETDEWEB)

    Blumenhagen, R [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, 80805 Muenchen (Germany); Plauschinn, E, E-mail: ralph.blumenhagen@mpp.mpg.d, E-mail: e.plauschinn@uu.n [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, 3508 TD Utrecht (Netherlands)

    2011-01-07

    In an on-shell conformal field theory approach, we find indications of a three-bracket structure for target space coordinates in general closed string backgrounds. This generalizes the appearance of noncommutative gauge theories for open strings in two-form backgrounds to a putative noncommutative/nonassociative gravity theory for closed strings probing curved backgrounds with non-vanishing three-form flux. Several aspects and consequences of the three-bracket structure are discussed and a new type of generalized uncertainty principle is proposed.

  9. Geometry, topology, and string theory

    International Nuclear Information System (INIS)

    Varadarajan, Uday

    2003-01-01

    A variety of scenarios are considered which shed light upon the uses and limitations of classical geometric and topological notions in string theory. The primary focus is on situations in which D-brane or string probes of a given classical space-time see the geometry quite differently than one might naively expect. In particular, situations in which extra dimensions, non-commutative geometries as well as other non-local structures emerge are explored in detail. Further, a preliminary exploration of such issues in Lorentzian space-times with non-trivial causal structures within string theory is initiated

  10. M-strings, Elliptic Genera and N=4 String Amplitudes

    CERN Document Server

    Hohenegger, Stefan

    2014-01-01

    We study mass-deformed N=2 gauge theories from various points of view. Their partition functions can be computed via three dual approaches: firstly, (p,q)-brane webs in type II string theory using Nekrasov's instanton calculus, secondly, the (refined) topological string using the topological vertex formalism and thirdly, M theory via the elliptic genus of certain M-strings configurations. We argue for a large class of theories that these approaches yield the same gauge theory partition function which we study in detail. To make their modular properties more tangible, we consider a fourth approach by connecting the partition function to the equivariant elliptic genus of R^4 through a (singular) theta-transform. This form appears naturally as a specific class of one-loop scattering amplitudes in type II string theory on T^2, which we calculate explicitly.

  11. M-strings, elliptic genera and N = 4 string amplitudes

    International Nuclear Information System (INIS)

    Hohenegger, S.; Iqbal, A.

    2014-01-01

    We study mass-deformed N = 2 gauge theories from various points of view. Their partition functions can be computed via three dual approaches: firstly, (p,q)-brane webs in type II string theory using Nekrasov's instanton calculus, secondly, the (refined) topological string using the topological vertex formalism and thirdly, M theory via the elliptic genus of certain M-strings configurations. We argue for a large class of theories that these approaches yield the same gauge theory partition function which we study in detail. To make their modular properties more tangible, we consider a fourth approach by connecting the partition function to the equivariant elliptic genus of C 2 through a (singular) theta-transform. This form appears naturally as a specific class of one-loop scattering amplitudes in type II string theory on T 2 , which we calculate explicitly. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Regulatory Approach To and Lessons Learned with Licensing of Service Life Extension at PAKS NPP

    International Nuclear Information System (INIS)

    Petofi, G.

    2012-01-01

    Paks Nuclear Power Plant of Hungary decided to extend the original design lifetime of the plant by 20 years, which expires on December 31, 2012 concerning unit 1. The Hungarian Atomic Energy Authority established the legal environments in order to license the extension using an approach similar to that followed in the United States. The regulation specifies the pre-conditions for the extension, defines the scoping and screening process for the passive and long lived systems, structures and components to be involved in the licensing and the respective methods of treatment and also determines how the active components shall be dealt with during the extended lifetime. The regulatory procedure is a two-step process including the oversight of the preparatory programme of the operator for the extension that started 4 years before the expiry of the lifetime and the licensing process itself, which is currently under way for unit 1 after the submittal of the licensee's application at the end of 2011. The first experiences with the regulatory assessment of the application are available yet and presented in this paper. (author)

  13. sigma model approach to the heterotic string theory

    International Nuclear Information System (INIS)

    Sen, A.

    1985-09-01

    Relation between the equations of motion for the massless fields in the heterotic string theory, and the conformal invariance of the sigma model describing the propagation of the heterotic string in arbitrary background massless fields is discussed. It is emphasized that this sigma model contains complete information about the string theory. Finally, we discuss the extension of the Hull-Witten proof of local gauge and Lorentz invariance of the sigma-model to higher order in α', and the modification of the transformation laws of the antisymmetric tensor field under these symmetries. Presence of anomaly in the naive N = 1/2 supersymmetry transformation is also pointed out in this context. 12 refs

  14. Charting the landscape of supercritical string theory.

    Science.gov (United States)

    Hellerman, Simeon; Swanson, Ian

    2007-10-26

    Special solutions of string theory in supercritical dimensions can interpolate in time between theories with different numbers of spacetime dimensions and different amounts of world sheet supersymmetry. These solutions connect supercritical string theories to the more familiar string duality web in ten dimensions and provide a precise link between supersymmetric and purely bosonic string theories. Dimension quenching and c duality appear to be natural concepts in string theory, giving rise to large networks of interconnected theories.

  15. Charting the Landscape of Supercritical String Theory

    International Nuclear Information System (INIS)

    Hellerman, Simeon; Swanson, Ian

    2007-01-01

    Special solutions of string theory in supercritical dimensions can interpolate in time between theories with different numbers of spacetime dimensions and different amounts of world sheet supersymmetry. These solutions connect supercritical string theories to the more familiar string duality web in ten dimensions and provide a precise link between supersymmetric and purely bosonic string theories. Dimension quenching and c duality appear to be natural concepts in string theory, giving rise to large networks of interconnected theories

  16. Matrix string theory on pp-waves

    Energy Technology Data Exchange (ETDEWEB)

    Bonelli, Giulio

    2003-06-21

    After a brief review on matrix string theory on flat backgrounds, we formulate matrix string models on different pp-wave backgrounds. This will be done both in the cases of constant and variable RR background flux for certain exact string geometries. We exhibit the non-perturbative representation of string interaction and show how the eigenvalue tunnelling drives the WKB expansion to give the usual perturbative string interaction also in supersymmetric pp-wave background cases.

  17. String theory and cosmological singularities

    Indian Academy of Sciences (India)

    time' can have a beginning or end. Well-known examples are singularities inside black holes and initial or final singularities in expanding or contracting universes. In recent times, string theory is providing new perspectives of such singularities ...

  18. Cache-oblivious string dictionaries

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting; Fagerberg, Rolf

    2006-01-01

    We present static cache-oblivious dictionary structures for strings which provide analogues of tries and suffix trees in the cache-oblivious model. Our construction takes as input either a set of strings to store, a single string for which all suffixes are to be stored, a trie, a compressed trie......, or a suffix tree, and creates a cache-oblivious data structure which performs prefix queries in O(logB n + |P|/B) I/Os, where n is the number of leaves in the trie, P is the query string, and B is the block size. This query cost is optimal for unbounded alphabets. The data structure uses linear space....

  19. String and Sticky Tape Experiments.

    Science.gov (United States)

    Edge, R. D., Ed.

    1979-01-01

    Explains how to demonstrate the fundamentals of one dimensional kinematics such as Newton's third law of motion, and collision between bodies, using simple materials of marbles, strings, sticky tape, drinking straws, and rubber bands. (GA)

  20. Spin chains and string theory.

    Science.gov (United States)

    Kruczenski, Martin

    2004-10-15

    Recently, an important test of the anti de Sitter/conformal field theory correspondence has been done using rotating strings with two angular momenta. We show that such a test can be described more generally as the agreement between two actions: one a low energy description of a spin chain appearing in the field theory side, and the other a limit of the string action in AdS5xS5. This gives a map between the mean value of the spin in the boundary theory and the position of the string in the bulk, and shows how a string action can emerge from a gauge theory in the large-N limit.

  1. Pattern recognition and string matching

    CERN Document Server

    Cheng, Xiuzhen

    2002-01-01

    The research and development of pattern recognition have proven to be of importance in science, technology, and human activity. Many useful concepts and tools from different disciplines have been employed in pattern recognition. Among them is string matching, which receives much theoretical and practical attention. String matching is also an important topic in combinatorial optimization. This book is devoted to recent advances in pattern recognition and string matching. It consists of twenty eight chapters written by different authors, addressing a broad range of topics such as those from classifica­ tion, matching, mining, feature selection, and applications. Each chapter is self-contained, and presents either novel methodological approaches or applications of existing theories and techniques. The aim, intent, and motivation for publishing this book is to pro­ vide a reference tool for the increasing number of readers who depend upon pattern recognition or string matching in some way. This includes student...

  2. String moduli inflation. An overview

    International Nuclear Information System (INIS)

    Cicoli, Michele; Quevedo, Fernando

    2011-06-01

    We present an overview of inflationary models derived from string theory focusing mostly on closed string moduli as inflatons. After a detailed discussion of the η-problem and different approaches to address it, we describe possible ways to obtain a de Sitter vacuum with all closed string moduli stabilised. We then look for inflationary directions and present some of the most promising scenarios where the inflatons are either the real or the imaginary part of Kaehler moduli. We pay particular attention on extracting potential observable implications, showing how most of the scenarios predict negligible gravitational waves and could therefore be ruled out by the Planck satellite. We conclude by briefly mentioning some open challenges in string cosmology beyond deriving just inflation. (orig.)

  3. String theory or field theory?

    International Nuclear Information System (INIS)

    Marshakov, A.V.

    2002-01-01

    The status of string theory is reviewed, and major recent developments - especially those in going beyond perturbation theory in the string theory and quantum field theory frameworks - are analyzed. This analysis helps better understand the role and place of experimental phenomena, it is emphasized that there are some insurmountable problems inherent in it - notably the impossibility to formulate the quantum theory of gravity on its basis - which prevent it from being a fundamental physical theory of the world of microscopic distances. It is this task, the creation of such a theory, which string theory, currently far from completion, is expected to solve. In spite of its somewhat vague current form, string theory has already led to a number of serious results and greatly contributed to progress in the understanding of quantum field theory. It is these developments, which are our concern in this review [ru

  4. On Field Theory of Open Strings, Tachyon Condensation and Closed Strings

    OpenAIRE

    Shatashvili, Samson L.

    2001-01-01

    I review the physical properties of different vacua in the background independent open string field theory. Talk presented at Strings 2001, Mumbai, India, http://theory.theory.tifr.res.in/strings/Proceedings/#sha-s.

  5. Black strings and classical hair

    International Nuclear Information System (INIS)

    Horowitz, G.T.; Yang, H.

    1997-01-01

    We examine the geometry near the event horizon of a family of black string solutions with traveling waves. It has previously been shown that the metric is continuous there. Contrary to expectations, we find that the geometry is not smooth, and the horizon becomes singular whenever a wave is present. Both five-dimensional and six-dimensional black strings are considered with similar results. copyright 1997 The American Physical Society

  6. Strings in the abelized picture

    International Nuclear Information System (INIS)

    Embacher, F.

    1990-01-01

    The transformation properties of the bosonic string variables under the recently discovered abelizing operator are exhibited. The intimate relation of this operator to the light-cone gauge condition is illustrated for the classical string. As an application of the formalism, the derivation of the BRST cohomology by the method of Freeman and Olive is carried over to the abelized picture, where it takes a particulary simple form. 14 refs. (Author)

  7. Semiclassical Strings in Supergravity PFT

    OpenAIRE

    Banerjee, Aritra; Biswas, Sagar; Panigrahi, Kamal L.

    2014-01-01

    Puff field theory (PFT) is an example of a non-local field theory which arises from a novel embedding of D-branes in a Melvin universe. We study several rotating and pulsating string solutions of the F-string equations of motion in the supergravity dual of the PFT. Further, we find a PP-wave geometry from this non-local spacetime by applying a Penrose limit and comment on its similarity with the maximally supersymmetric PP-wave background.

  8. Dynamics of strings between walls

    International Nuclear Information System (INIS)

    Eto, Minoru; Fujimori, Toshiaki; Nagashima, Takayuki; Nitta, Muneto; Ohashi, Keisuke; Sakai, Norisuke

    2009-01-01

    Configurations of vortex strings stretched between or ending on domain walls were previously found to be 1/4 Bogomol'nyi-Prasad-Sommerfield (BPS) states in N=2 supersymmetric gauge theories in 3+1 dimensions. Among zero modes of string positions, the center of mass of strings in each region between two adjacent domain walls is shown to be non-normalizable whereas the rests are normalizable. We study dynamics of vortex strings stretched between separated domain walls by using two methods, the moduli space (geodesic) approximation of full 1/4 BPS states and the charged particle approximation for string end points in the wall effective action. In the first method we explicitly obtain the effective Lagrangian in the strong coupling limit, which is written in terms of hypergeometric functions, and find the 90 deg. scattering for head-on collision. In the second method the domain wall effective action is assumed to be U(1) N gauge theory, and we find a good agreement between two methods for well-separated strings.

  9. String theory on the edge

    International Nuclear Information System (INIS)

    Thorlacius, L.

    1989-01-01

    Open string vacuum configurations are described in terms of a one-dimensional field theory on the worldsheet boundary. The one-dimensional path integral has direct physical interpretation as a source term for closed string fields. This means that the vacuum divergences (Mobius infinities) of the path integral must be renormalized correctly. The author shows that reparametrization invariance Ward identities, apart from specifying the equations of motion of spacetime background gauge fields, also serve to fix the renormalization scheme of the vacuum divergences. He argues that vacuum configurations of open strings correspond to Caldeira-Leggett models of dissipative quantum mechanics (DQM) evaluated at a delocalization critical point. This connection reveals that critical DQM will manifest reparametrization invariance (inherited from the conformal invariance of string theory) rather than just scale invariance. This connection should open up new ways of constructing analytic and approximate solutions of open string theory (in particular, topological solitons such as monopoles and instantons). Type I superstring theory gives rise to a supersymmetric boundary field theory. Bose-Fermi cancellation eliminates vacuum divergences but the one-loop beta function remains the same as in the bosonic theory. Reparametrization invariance Ward identities dictate a boundary state normalization which yields consistent string-loop corrections to spacetime equations of motion, in both the periodic and anti-periodic fermion sectors

  10. Experimental observation of Bethe strings

    Science.gov (United States)

    Wang, Zhe; Wu, Jianda; Yang, Wang; Bera, Anup Kumar; Kamenskyi, Dmytro; Islam, A. T. M. Nazmul; Xu, Shenglong; Law, Joseph Matthew; Lake, Bella; Wu, Congjun; Loidl, Alois

    2018-02-01

    Almost a century ago, string states—complex bound states of magnetic excitations—were predicted to exist in one-dimensional quantum magnets. However, despite many theoretical studies, the experimental realization and identification of string states in a condensed-matter system have yet to be achieved. Here we use high-resolution terahertz spectroscopy to resolve string states in the antiferromagnetic Heisenberg-Ising chain SrCo2V2O8 in strong longitudinal magnetic fields. In the field-induced quantum-critical regime, we identify strings and fractional magnetic excitations that are accurately described by the Bethe ansatz. Close to quantum criticality, the string excitations govern the quantum spin dynamics, whereas the fractional excitations, which are dominant at low energies, reflect the antiferromagnetic quantum fluctuations. Today, Bethe’s result is important not only in the field of quantum magnetism but also more broadly, including in the study of cold atoms and in string theory; hence, we anticipate that our work will shed light on the study of complex many-body systems in general.

  11. Fast searching in packed strings

    DEFF Research Database (Denmark)

    Bille, Philip

    2011-01-01

    Given strings P and Q the (exact) string matching problem is to find all positions of substrings in Q matching P. The classical Knuth–Morris–Pratt algorithm [SIAM J. Comput. 6 (2) (1977) 323–350] solves the string matching problem in linear time which is optimal if we can only read one character...... at the time. However, most strings are stored in a computer in a packed representation with several characters in a single word, giving us the opportunity to read multiple characters simultaneously. In this paper we study the worst-case complexity of string matching on strings given in packed representation....... Let m⩽n be the lengths P and Q, respectively, and let σ denote the size of the alphabet. On a standard unit-cost word-RAM with logarithmic word size we present an algorithm using timeO(nlogσn+m+occ). Here occ is the number of occurrences of P in Q. For m=o(n) this improves the O(n) bound of the Knuth...

  12. Chern-Simons couplings for dielectric F-strings in matrix string theory

    International Nuclear Information System (INIS)

    Brecher, Dominic; Janssen, Bert; Lozano, Yolanda

    2002-01-01

    We compute the non-abelian couplings in the Chern-Simons action for a set of coinciding fundamental strings in both the type IIA and type IIB Matrix string theories. Starting from Matrix theory in a weakly curved background, we construct the linear couplings of closed string fields to type IIA Matrix strings. Further dualities give a type IIB Matrix string theory and a type IIA theory of Matrix strings with winding. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  13. New expressions for string loop amplitudes leading to an ultra-simple conception of string dynamics

    International Nuclear Information System (INIS)

    Chan Hongmo; Tsou Sheungtsun; Bordes, J.; Nellen, L.

    1990-11-01

    New expressions are derived for string loop amplitudes as overlap integrals of string wave functionals. They are shown to take the form of exchange terms coming from the Bose-Einstein symmetrisation between string segments. One is thus led to the ultra-simple conception that string theory is basically free, and that 'string interactions' are due merely to the fact that strings are composite objects with Bose-Einstein segments as constituents. (author)

  14. Gravity from strings

    International Nuclear Information System (INIS)

    Deser, S.

    1987-01-01

    We obtain the Einstein action plus quadratic curvature corrections generated by closed bosonic, heterotic and supersymmetric strings by matching the four-graviton amplitude (to first order in the slope parameter and fourth power of momenta) with an effective local gravitational action. The resulting corrections are first shown to be of the Gauss-Bonnet form. It is then noted that, by the very nature of the slope expansion, the field-redefinition theorem applies. Consequently, only the curvature-squared term is determined, while squares of its contractions are explicitly seen not to contribute. This latter property has a generalization to all orders which implies that the effective gravitational action is unavoidably ghost-free. The properties of solutions to these corrected theories are then examined. First neglecting dilatons, we find the explicit 'Schwarzschild' metrics. Both asymptotically flat and de Sitter solutions are present. The latter are however shown to be unstable. The former have horizons and singularities which are respectively smaller and less violent than in Einstein gravity; the correct sign of the slope parameter also ensures absence of naked singularities. When dilatons are included, the cosmological vacua are gratifyingly excluded. (orig.)

  15. Fuzzy cognitive maps for applied sciences and engineering from fundamentals to extensions and learning algorithms

    CERN Document Server

    2014-01-01

    Fuzzy Cognitive Maps (FCM) constitute cognitive models in the form of fuzzy directed graphs consisting of two basic elements: the nodes, which basically correspond to “concepts” bearing different states of activation depending on the knowledge they represent, and the “edges” denoting the causal effects that each source node exercises on the receiving concept expressed through weights. Weights take values in the interval [-1,1], which denotes the positive, negative or neutral causal relationship between two concepts. An FCM can be typically obtained through linguistic terms, inherent to fuzzy systems, but with a structure similar to the neural networks, which facilitates data processing, and has capabilities for training and adaptation. During the last 10 years, an exponential growth of published papers in FCMs was followed showing great impact potential. Different FCM structures and learning schemes have been developed, while numerous studies report their use in many contexts with highly successful m...

  16. Remarks on stable and quasi-stable k-strings at large N

    International Nuclear Information System (INIS)

    Armoni, A.; Shifman, M.

    2003-01-01

    We discuss k-strings in the large-N Yang-Mills theory and its supersymmetric extension. Whereas the tension of the bona fide (stable) QCD string is expected to depend only on the N-ality of the representation, tensions that depend on specific representation R are often reported in the lattice literature. In particular, adjoint strings are discussed and found in certain simulations. We clarify this issue by systematically exploiting the notion of the quasi-stable strings which becomes well-defined at large N. The quasi-stable strings with representation-dependent tensions decay, but the decay rate (per unit length per unit time) is suppressed as Λ 2 F(N) where F(N) falls off as a function of N. It can be determined on the case-by-case basis. The quasi-stable strings eventually decay into stable strings whose tension indeed depends only on the N-ality. We also briefly review large-N arguments showing why the Casimir formula for the string tension cannot be correct, and present additional arguments in favor of the sine formula. Finally, we comment on the relevance of our estimates to Euclidean lattice measurements

  17. Layer Construction of 3D Topological States and String Braiding Statistics

    Directory of Open Access Journals (Sweden)

    Chao-Ming Jian

    2014-12-01

    Full Text Available While the topological order in two dimensions has been studied extensively since the discovery of the integer and fractional quantum Hall systems, topological states in three spatial dimensions are much less understood. In this paper, we propose a general formalism for constructing a large class of three-dimensional topological states by stacking layers of 2D topological states and introducing coupling between them. Using this construction, different types of topological states can be obtained, including those with only surface topological order and no bulk topological quasiparticles, and those with topological order both in the bulk and at the surface. For both classes of states, we study its generic properties and present several explicit examples. As an interesting consequence of this construction, we obtain example systems with nontrivial braiding statistics between string excitations. In addition to studying the string-string braiding in the example system, we propose a topological field-theory description for the layer-constructed systems, which captures not only the string-particle braiding statistics but also the string-string braiding statistics when the coupling is twisted. Last, we provide a proof of a general identity for Abelian string statistics and discuss an example system with non-Abelian strings.

  18. Conformal supergravity in twistor-string theory

    Energy Technology Data Exchange (ETDEWEB)

    Berkovits, Nathan [Instituto de Fisica Teorica, Universidade Estadual Paulista, Rua Pamplona 145, 01405-900, Sao Paulo, SP (Brazil)]. E-mail: nberkovi@ift.unesp.br; Witten, Edward [School of Natural Sciences, Institute for Advanced Study, Princeton NJ 08540 (United States)

    2004-08-01

    Conformal supergravity arises in presently known formulations of twistor-string theory either via closed strings or via gauge-singlet open strings. We explore this sector of twistor-string theory, relating the relevant string modes to the particles and fields of conformal supergravity. We use the twistor-string theory to compute some tree level scattering amplitudes with supergravitons. Since the supergravitons interact with the same coupling constant as the Yang-Mills fields, conformal supergravity states will contribute to loop amplitudes of Yang-Mills gluons in these theories. Those loop amplitudes will therefore not coincide with the loop amplitudes of pure super Yang-Mills theory. (author)

  19. Gravitational Lensing Signatures of Long Cosmic Strings

    CERN Document Server

    De Laix, A A; Vachaspati, T; Laix, Andrew A. de; Krauss, Lawrence M.; Vachaspati, Tanmay

    1997-01-01

    The gravitational lensing by long, wiggly cosmic strings is shown to produce a large number of lensed images of a background source. In addition to pairs of images on either side of the string, a number of small images outline the string due to small-scale structure on the string. This image pattern could provide a highly distinctive signature of cosmic strings. Since the optical depth for multiple imaging of distant quasar sources by long strings may be comparable to that by galaxies, these image patterns should be clearly observable in the next generation of redshift surveys such as the Sloan Digital Sky Survey.

  20. String Theory for Pedestrians (1/3)

    CERN Multimedia

    CERN. Geneva

    2009-01-01

    This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

  1. String Theory for Pedestrians (2/3)

    CERN Multimedia

    CERN. Geneva

    2009-01-01

    This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

  2. String Theory for Pedestrians (3/3)

    CERN Multimedia

    CERN. Geneva

    2009-01-01

    This is a non-technical rapid course on string theory. Lecture 1 is an introduction to the basics of the subject: classical and quantum strings, D(irichlet) branes and string-string dualities. In lecture 2 I will discuss string unification of the fundamental forces, covering both its successes and failures. Finally in lecture 3 I will review string models of black hole microstates, the holographic gauge/gravity duality and, if time permits, potential applications to the physics of the strong interactions.

  3. Ureteric stent placement with extraction string: no strings attached?

    Science.gov (United States)

    Bockholt, Nathan A; Wild, Trevor T; Gupta, Amit; Tracy, Chad R

    2012-12-01

    Study Type--Therapy (case series) Level of Evidence 4 What's known on the subject? and What does the study add? Of patients treated with an indwelling ureteric stent 80-90% experience lower urinary tract symptoms that are a hindrance to health-related quality of life. The prevalence of the extraction/retrieval string after ureteroscopy for stone disease and stent placement varies significantly between surgeons and published series, but the benefits of eliminating the need for a secondary procedure such as cystoscopy and stent removal, as well as the decrease in cost to the patient are well established. Published reports have not addressed the prevalence of post-procedure related events (PREs) in patients who have received an indwelling ureteric stent with the extraction/retrieval string still intact after ureteroscopy for stone disease. By analysing PREs (Emergency Room visits, unscheduled clinic visits, and telephone calls) related to their stent or procedure for patients with and without an extraction/retrieval string, the feasibility of the extraction string can be validated and the misconceptions about their use can be alleviated. • To review a retrospective ureteric stent cohort with and without extraction string to compare post-procedure related events (PRE), as ureteric stent placement after endoscopic management of urolithiasis is common, but data regarding the potential benefits or disadvantages of ureteric stent placement with extraction string are sparse. • Between June 2009 and June 2010, 293 patients underwent ureteroscopy with or without lithotripsy for stone disease. • In all, 181 patients had a unilateral procedure and underwent stent placement postoperatively. • Records were retrospectively reviewed for operative data and PRE occurring within the first 6 weeks after surgery, defined as unscheduled clinic or Emergency Room visits, or adverse event telephone calls. • Of 181 patients who underwent ureteric stent placement, 43 (23

  4. String theory inspired deformations of quantum field theories

    Science.gov (United States)

    Chiou, Dah-Wei

    In this dissertation, some extensions on field theories with deformations inspired by string theory are explored and their implications are investigated. These are: (i) noncommutative dipole field theory (DFT) and unitarity; (ii) three dimensional super Yang-Mills theory and mini-twistor string theory; (iii) massive super Yang-Mills theory and twistor string theory; and (iv) a deformation of twistor space and N = 4 super Yang-Mills theory with a chiral mass term. The DFT with fixed spacetime vectors ("dipole-vectors") is formulated for gauge theory coupled with a scalar field of adjoint charge. The argument for the violation of unitarity in field theories on a noncommutative spacetime is extended to the case of DFT: with a timelike dipole vector, 1-loop amplitudes are shown not to obey the optical theorem and thus violate unitarity. Likewise, a simple 0 + 1D quantum mechanical system with nonlocal potential of finite extent in time also gives violation of unitarity. Associated with D = 3 super Yang-Mills theory, the topological B-model is constructed for the twistor string theory, of which the target space is the (super-)mini-twistor space. As the D = 4 twistor space can be considered as a fibration over D = 3 mini-twistor space, the dimensional reduction from D = 4 to D = 3 is conducted to obtain the scattering amplitudes for D = 3 super Yang-Mills theory. The result shows that, analogous to the D = 4 case, the twistor transformed D = 3 amplitudes are supported on holomorphic curves in the (super-)mini-twistor space. Another alternative twistor description---Berkovits's open string theory---is also analyzed. By the prescription which interrelates Witten's B-model and Berkovits's open string theory, the dimensional reduction can be made for Berkovits's model as well, in which the enhanced R-symmetry Spin(7) is recognized, whereas only the subgroup SU(4) is manifest in the B-model. The extension of the twistor string theory by adding mass terms is then proposed and

  5. String Theory in a Nutshell

    International Nuclear Information System (INIS)

    Skenderis, Kostas

    2007-01-01

    The book 'String Theory in a Nutshell' by Elias Kiritsis provides a comprehensive introduction to modern string theory. String theory is the leading candidate for a theory that successfully unifies all fundamental forces of nature, including gravity. The subject has been continuously developing since the early 1970s, with classic textbooks on the subject being those of Green, Schwarz and Witten (1987) and Polchinski (1998). Since the latter was published there have been substantial developments, in particular in understanding black holes and gravity/gauge theory dualities. A textbook treatment of this important material is clearly needed, both by students and researchers in string theory and by mathematicians and physicists working in related fields. This book has a good selection of material, starting from basics and moving into classic and modern topics. In particular, Kiritsis' presentation of the basic material is complementary to that of the earlier textbooks and he includes a number of topics which are not easily found or covered adequately elsewhere, for example, loop corrections to string effective couplings. Overall the book nicely covers the major advances of the last ten years, including (non-perturbative) string dualities, black hole physics, AdS/CFT and matrix models. It provides a concise but fairly complete introduction to these subjects which can be used both by students and by researchers. Moreover the emphasis is on results that are reasonably established, as is appropriate for a textbook; concise summaries are given for subjects which are still in flux, with references to relevant reviews and papers. A positive feature of the book is that the bibliography sections at the end of each chapter provide a comprehensive guide to the literature. The bibliographies point to reviews and pedagogical papers on subjects covered in this book as well as those that were omitted. It is rare for a textbook to contain such a self-contained and detailed guide to

  6. String Theory in a Nutshell

    Energy Technology Data Exchange (ETDEWEB)

    Skenderis, Kostas [Institute of Theoretical Physics, Universiteit van Amsterdam, Valckenierstraat 65, NL-1018 XE Amsterdam (Netherlands)

    2007-11-21

    The book 'String Theory in a Nutshell' by Elias Kiritsis provides a comprehensive introduction to modern string theory. String theory is the leading candidate for a theory that successfully unifies all fundamental forces of nature, including gravity. The subject has been continuously developing since the early 1970s, with classic textbooks on the subject being those of Green, Schwarz and Witten (1987) and Polchinski (1998). Since the latter was published there have been substantial developments, in particular in understanding black holes and gravity/gauge theory dualities. A textbook treatment of this important material is clearly needed, both by students and researchers in string theory and by mathematicians and physicists working in related fields. This book has a good selection of material, starting from basics and moving into classic and modern topics. In particular, Kiritsis' presentation of the basic material is complementary to that of the earlier textbooks and he includes a number of topics which are not easily found or covered adequately elsewhere, for example, loop corrections to string effective couplings. Overall the book nicely covers the major advances of the last ten years, including (non-perturbative) string dualities, black hole physics, AdS/CFT and matrix models. It provides a concise but fairly complete introduction to these subjects which can be used both by students and by researchers. Moreover the emphasis is on results that are reasonably established, as is appropriate for a textbook; concise summaries are given for subjects which are still in flux, with references to relevant reviews and papers. A positive feature of the book is that the bibliography sections at the end of each chapter provide a comprehensive guide to the literature. The bibliographies point to reviews and pedagogical papers on subjects covered in this book as well as those that were omitted. It is rare for a textbook to contain such a self-contained and

  7. An exact bosonization rule for c = 1 noncritical string theory

    International Nuclear Information System (INIS)

    Ishibashi, Nobuyuki; Yamaguchi, Atsushi

    2007-01-01

    We construct a string field theory for c = 1 noncritical strings using the loop variables as the string field. We show how one can express the nonrelativistic free fermions which describes the theory, in terms of these string fields

  8. Topological strings from quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Grassi, Alba; Marino, Marcos [Geneve Univ. (Switzerland). Dept. de Physique Theorique et Section de Mathematique; Hatsuda, Yasuyuki [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Theory Group

    2014-12-15

    We propose a general correspondence which associates a non-perturbative quantum-mechanical operator to a toric Calabi-Yau manifold, and we conjecture an explicit formula for its spectral determinant in terms of an M-theoretic version of the topological string free energy. As a consequence, we derive an exact quantization condition for the operator spectrum, in terms of the vanishing of a generalized θ function. The perturbative part of this quantization condition is given by the Nekrasov-Shatashvili limit of the refined topological string, but there are non-perturbative corrections determined by the conventional topological string. We analyze in detail the cases of local P{sup 2}, local P{sup 1} x P{sup 1} and local F{sub 1}. In all these cases, the predictions for the spectrum agree with the existing numerical results. We also show explicitly that our conjectured spectral determinant leads to the correct spectral traces of the corresponding operators, which are closely related to topological string theory at orbifold points. Physically, our results provide a Fermi gas picture of topological strings on toric Calabi-Yau manifolds, which is fully non-perturbative and background independent. They also suggest the existence of an underlying theory of M2 branes behind this formulation. Mathematically, our results lead to precise, surprising conjectures relating the spectral theory of functional difference operators to enumerative geometry.

  9. Towards optimal packed string matching

    DEFF Research Database (Denmark)

    Ben-Kiki, Oren; Bille, Philip; Breslauer, Dany

    2014-01-01

    In the packed string matching problem, it is assumed that each machine word can accommodate up to α characters, thus an n-character string occupies n/α memory words.(a) We extend the Crochemore–Perrin constant-space O(n)-time string-matching algorithm to run in optimal O(n/α) time and even in real......-time, achieving a factor α speedup over traditional algorithms that examine each character individually. Our macro-level algorithm only uses the standard AC0 instructions of the word-RAM model (i.e. no integer multiplication) plus two specialized micro-level AC0 word-size packed-string instructions. The main word...... matching work.(b) We also consider the complexity of the packed string matching problem in the classical word-RAM model in the absence of the specialized micro-level instructions wssm and wslm. We propose micro-level algorithms for the theoretically efficient emulation using parallel algorithms techniques...

  10. Differential geometry in string models

    International Nuclear Information System (INIS)

    Alvarez, O.

    1986-01-01

    In this article the author reviews the differential geometric approach to the quantization of strings. A seminal paper demonstrates the connection between the trace anomaly and the critical dimension. The role played by the Faddeev-Popov ghosts has been instrumental in much of the subsequent work on the quantization of strings. This paper discusses the differential geometry of two dimensional surfaces and its importance in the quantization of strings. The path integral quantization approach to strings will be carefully analyzed to determine the correct effective measure for string theories. The choice of measure for the path integral is determined by differential geometric considerations. Once the measure is determined, the manifest diffeomorphism invariance of the theory will have to be broken by using the Faddeev-Popov ansatz. The gauge fixed theory is studied in detail with emphasis on the role of conformal and gravitational anomalies. In the analysis, the path integral formulation of the gauge fixed theory requires summing over all the distinct complex structures on the manifold

  11. Topological strings from quantum mechanics

    International Nuclear Information System (INIS)

    Grassi, Alba; Marino, Marcos; Hatsuda, Yasuyuki

    2014-12-01

    We propose a general correspondence which associates a non-perturbative quantum-mechanical operator to a toric Calabi-Yau manifold, and we conjecture an explicit formula for its spectral determinant in terms of an M-theoretic version of the topological string free energy. As a consequence, we derive an exact quantization condition for the operator spectrum, in terms of the vanishing of a generalized θ function. The perturbative part of this quantization condition is given by the Nekrasov-Shatashvili limit of the refined topological string, but there are non-perturbative corrections determined by the conventional topological string. We analyze in detail the cases of local P 2 , local P 1 x P 1 and local F 1 . In all these cases, the predictions for the spectrum agree with the existing numerical results. We also show explicitly that our conjectured spectral determinant leads to the correct spectral traces of the corresponding operators, which are closely related to topological string theory at orbifold points. Physically, our results provide a Fermi gas picture of topological strings on toric Calabi-Yau manifolds, which is fully non-perturbative and background independent. They also suggest the existence of an underlying theory of M2 branes behind this formulation. Mathematically, our results lead to precise, surprising conjectures relating the spectral theory of functional difference operators to enumerative geometry.

  12. String theory or field theory?

    International Nuclear Information System (INIS)

    Marshakov, Andrei V

    2002-01-01

    The status of string theory is reviewed, and major recent developments - especially those in going beyond perturbation theory in the string theory and quantum field theory frameworks - are analyzed. This analysis helps better understand the role and place of string theory in the modern picture of the physical world. Even though quantum field theory describes a wide range of experimental phenomena, it is emphasized that there are some insurmountable problems inherent in it - notably the impossibility to formulate the quantum theory of gravity on its basis - which prevent it from being a fundamental physical theory of the world of microscopic distances. It is this task, the creation of such a theory, which string theory, currently far from completion, is expected to solve. In spite of its somewhat vague current form, string theory has already led to a number of serious results and greatly contributed to progress in the understanding of quantum field theory. It is these developments which are our concern in this review. (reviews of topical problems)

  13. Ethanol-induced effects on sting extension response and punishment learning in the western honey bee (Apis mellifera.

    Directory of Open Access Journals (Sweden)

    Manuel A Giannoni-Guzmán

    Full Text Available Acute ethanol administration is associated with sedation and analgesia as well as behavioral disinhibition and memory loss but the mechanisms underlying these effects remain to be elucidated. During the past decade, insects have emerged as important model systems to understand the neural and genetic bases of alcohol effects. However, novel assays to assess ethanol's effects on complex behaviors in social or isolated contexts are necessary. Here we used the honey bee as an especially relevant model system since bees are typically exposed to ethanol in nature when collecting standing nectar crop of flowers, and there is recent evidence for independent biological significance of this exposure for social behavior. Bee's inhibitory control of the sting extension response (SER and a conditioned-place aversion assay were used to study ethanol effects on analgesia, behavioral disinhibition, and associative learning. Our findings indicate that although ethanol, in a dose-dependent manner, increases SER thresholds (analgesic effects, it disrupts the ability of honey bees to inhibit SER and to associate aversive stimuli with their environment. These results suggest that ethanol's effects on analgesia, behavioral disinhibition and associative learning are common across vertebrates and invertebrates. These results add to the use of honey bees as an ethanol model to understand ethanol's effects on complex, socially relevant behaviors.

  14. Black strings ending on horizons

    Science.gov (United States)

    Haddad, Nidal

    2012-12-01

    We construct an approximate static gravitational solution of the Einstein equations, with negative cosmological constant, describing a test black string stretching from the boundary of the Schwarzschild-AdS5 black brane toward the horizon. The construction builds on a derivative expansion method, assuming that the black brane metric changes slowly along the black string direction. We provide a solution up to second order in derivatives, and it implies, in particular, that the black string must shrink to zero size at the horizon of the black brane. In the near-horizon region of the black brane, where the two horizons intersect, we provide an exact solution of a cone that describes two intersecting horizons at different temperatures. Moreover, we show that this solution equally describes a thin and long black droplet.

  15. Cooperative strings and glassy interfaces.

    Science.gov (United States)

    Salez, Thomas; Salez, Justin; Dalnoki-Veress, Kari; Raphaël, Elie; Forrest, James A

    2015-07-07

    We introduce a minimal theory of glass formation based on the ideas of molecular crowding and resultant string-like cooperative rearrangement, and address the effects of free interfaces. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings, and we recover the Adam-Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel-Fulcher-Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangement allow us to predict a temperature-dependent expression for the cooperative length ξ of bulk relaxation. Finally, we explore the influence of sample boundaries when the system size becomes comparable to ξ. The theory is in agreement with measurements of the glass-transition temperature of thin polymer films, and allows quantification of the temperature-dependent thickness hm of the interfacial mobile layer.

  16. Quantum Inhomogeneities in String Cosmology

    CERN Document Server

    Buonanno, A; Ungarelli, C; Veneziano, Gabriele

    1998-01-01

    Within two specific string cosmology scenarios --differing in the way the pre- and post-big bang phases are joined-- we compute the size and spectral slope of various types of cosmologically amplified quantum fluctuations that arise in generic compactifications of heterotic string theory. By further imposing that these perturbations become the dominant source of energy at the onset of the radiation era, we obtain physical bounds on the background's moduli, and discuss the conditions under which both a (quasi-) scale-invariant spectrum of axionic perturbations and sufficiently large seeds for the galactic magnetic fields are generated. We also point out a potential problem with achieving the exit to the radiation era when the string coupling is near its present value.

  17. Vector superconductivity in cosmic strings

    International Nuclear Information System (INIS)

    Dvali, G.R.; Mahajan, S.M.

    1992-03-01

    We argue that in most realistic cases, the usual Witten-type bosonic superconductivity of the cosmic string is automatically (independent of the existence of superconducting currents) accompanied by the condensation of charged gauge vector bosons in the core giving rise to a new vector type superconductivity. The value of the charged vector condensate is related with the charged scalar expectation value, and vanishes only if the latter goes to zero. The mechanism for the proposed vector superconductivity, differing fundamentally from those in the literature, is delineated using the simplest realistic example of the two Higgs doublet standard model interacting with the extra cosmic string. It is shown that for a wide range of parameters, for which the string becomes scalarly superconducting, W boson condensates (the sources of vector superconductivity) are necessarily excited. (author). 14 refs

  18. The STRING database in 2011

    DEFF Research Database (Denmark)

    Szklarczyk, Damian; Franceschini, Andrea; Kuhn, Michael

    2011-01-01

    and computational prediction techniques. However, public efforts to collect and present protein interaction information have struggled to keep up with the pace of interaction discovery, partly because protein-protein interaction information can be error-prone and require considerable effort to annotate. Here, we...... present an update on the online database resource Search Tool for the Retrieval of Interacting Genes (STRING); it provides uniquely comprehensive coverage and ease of access to both experimental as well as predicted interaction information. Interactions in STRING are provided with a confidence score......, and accessory information such as protein domains and 3D structures is made available, all within a stable and consistent identifier space. New features in STRING include an interactive network viewer that can cluster networks on demand, updated on-screen previews of structural information including homology...

  19. General relativity, strings, and mathematical physics

    CERN Document Server

    Porrati, Massimo

    1999-01-01

    We give a historical review of some aspects of string theory relevant to our present understanding of general relativity, and connected with Einstein's unification program. We also point out to various mathematical fallouts of $9 string theory. (31 refs).

  20. On the string equation at c=1

    International Nuclear Information System (INIS)

    Nakatsu, Toshio.

    1994-07-01

    The analogue of the string equation which specifies the partition function of c=1 string with a compactification radius β is an element of Z ≥1 is described in the framework of Toda lattice hierarchy. (author)

  1. Learning as Search Optimization: Approximate Large Margin Methods for Structured Prediction

    OpenAIRE

    Daumé III, Hal; Marcu, Daniel

    2009-01-01

    Mappings to structured output spaces (strings, trees, partitions, etc.) are typically learned using extensions of classification algorithms to simple graphical structures (eg., linear chains) in which search and parameter estimation can be performed exactly. Unfortunately, in many complex problems, it is rare that exact search or parameter estimation is tractable. Instead of learning exact models and searching via heuristic means, we embrace this difficulty and treat the structured output pro...

  2. Introduction to field theory of strings

    International Nuclear Information System (INIS)

    Kikkawa, K.

    1987-01-01

    The field theory of bosonic string is reviewed. First, theory is treated in a light-cone gauge. After a brief survey of the first quantized theory of free string, the second quantization is discussed. All possible interactions of strings are introduced based on a smoothness condition of work sheets swept out by strings. Perturbation theory is developed. Finally a possible way to the manifest covariant formalism is discussed

  3. The STRING database in 2017

    DEFF Research Database (Denmark)

    Szklarczyk, Damian; Morris, John H; Cook, Helen

    2017-01-01

    A system-wide understanding of cellular function requires knowledge of all functional interactions between the expressed proteins. The STRING database aims to collect and integrate this information, by consolidating known and predicted protein-protein association data for a large number of organi......A system-wide understanding of cellular function requires knowledge of all functional interactions between the expressed proteins. The STRING database aims to collect and integrate this information, by consolidating known and predicted protein-protein association data for a large number...

  4. Semiclassical strings in supergravity PFT

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Aritra; Biswas, Sagar; Panigrahi, Kamal L. [Indian Institute of Technology Kharagpur, Department of Physics, Kharagpur (India)

    2014-10-15

    Puff field theory (PFT) is an example of a non-local field theory which arises from a novel embedding of D-branes in a Melvin universe. We study several rotating and pulsating string solutions of the F-string equations of motion in the supergravity dual of the PFT. Further, we find a PP-wave geometry from this non-local spacetime by applying a Penrose limit and comment on its similarity with the maximally supersymmetric PP-wave background. (orig.)

  5. Cosmic string in gravity's rainbow

    Science.gov (United States)

    Momeni, Davood; Upadhyay, Sudhaker; Myrzakulov, Yerlan; Myrzakulov, Ratbay

    2017-09-01

    In this paper, we study the various cylindrical solutions (cosmic strings) in gravity's rainbow scenario. In particular, we calculate the gravitational field equations corresponding to energy-dependent background. Further, we discuss the possible Kasner, quasi-Kasner and non-Kasner exact solutions of the field equations. In this framework, we find that quasi-Kasner solutions cannot be realized in gravity's rainbow. Assuming only time-dependent metric functions, we also analyse the time-dependent vacuum cosmic strings in gravity's rainbow, which are completely different than the other GR solutions.

  6. The Physics of "String Passing through Ice"

    Science.gov (United States)

    Mohazzabi, Pirooz

    2011-01-01

    One of the oldest yet interesting experiments related to heat and thermodynamics is placing a string on a block of ice and hanging two masses from the ends of the string. Sometime later, it is discovered that the string has passed through the ice without cutting it in half. A simple explanation of this effect is that the pressure caused by the…

  7. The Illusive Sound of a Bundengan String

    Science.gov (United States)

    Parikesit, Gea O. F.; Kusumaningtyas, Indraswari

    2017-01-01

    The acoustics of a vibrating string is frequently used as a simple example of how physics can be applied in the field of art. In this paper we describe a simple experiment and analysis using a clipped string. This experiment can generate scientific curiosity among students because the sound generated by the string seem surprising to our senses.…

  8. How Do String Majors Become Teachers?

    Science.gov (United States)

    Ha, Joy

    2015-01-01

    This study was motivated by the desire to understand how to support the development of competent and confident string instrument teachers. This research investigates early-career string instrument teachers' experiences of pre-service tertiary education and induction, and how these experiences impacted early-career string teachers' competence to…

  9. The Picture Brightens (Slightly) for String Programs

    Science.gov (United States)

    Olson, Cathy Applefeld

    2010-01-01

    It may not be the best of times for the school's string and orchestra programs, but things certainly are looking up. This article focuses on a recent report which cites the numerous positives, including an increase in the number of districts offering strings classes, a greater variety in the racial mix of strings students, and a less drastic…

  10. String solitons and T-duality

    NARCIS (Netherlands)

    Bergshoeff, Eric A.; Riccioni, Fabio

    We construct for arbitrary dimensions a universal T-duality covariant expression for the Wess-Zumino terms of supersymmetric String Solitons in toroidally compactified string theories with 32 supercharges. The worldvolume fields occurring in the effective action of these String Solitons form either

  11. Symmetries and Interactions in Matrix String Theory

    NARCIS (Netherlands)

    Hacquebord, F.H.

    1999-01-01

    This PhD-thesis reviews matrix string theory and recent developments therein. The emphasis is put on symmetries, interactions and scattering processes in the matrix model. We start with an introduction to matrix string theory and a review of the orbifold model that flows out of matrix string theory

  12. Glueballs as rotating folded closed strings

    Science.gov (United States)

    Sonnenschein, Jacob; Weissman, Dorin

    2015-12-01

    In previous papers [1, 2] we argued that mesons and baryons can be described as rotating open strings in holographic backgrounds. Now we turn to closed strings, which should be the duals of glueballs. We look at the rotating folded closed string in both flat and curved backgrounds.

  13. Are Stopped Strings Preferred in Sad Music?

    Directory of Open Access Journals (Sweden)

    David Huron

    2017-01-01

    Full Text Available String instruments may be played either with open strings (where the string vibrates between the bridge and a hard wooden nut or with stopped strings (where the string vibrates between the bridge and a performer's finger pressed against the fingerboard. Compared with open strings, stopped strings permit the use of vibrato and exhibit a darker timbre. Inspired by research on the timbre of sad speech, we test whether there is a tendency to use stopped strings in nominally sad music. Specifically, we compare the proportion of potentially open-to-stopped strings in a sample of slow, minor-mode movements with matched major-mode movements. By way of illustration, a preliminary analysis of Samuel Barber's famous Adagio from his Opus 11 string quartet shows that the selected key (B-flat minor provides the optimum key for minimizing open string tones. However, examination of a broader controlled sample of quartet movements by Haydn, Mozart and Beethoven failed to exhibit the conjectured relationship. Instead, major-mode movements were found to avoid possible open strings more than slow minor-mode movements.

  14. Open bosonic string in background electromagnetic field

    International Nuclear Information System (INIS)

    Nesterenko, V.V.

    1987-01-01

    The classical and quantum dynamics of an open string propagating in the D-dimensional space-time in the presence of a background electromagnetic field is investigated. An important point in this consideration is the use of the generalized light-like gauge. There are considered the strings of two types; the neutral strings with charges at their ends obeying the condition q 1 +q 2 =0 and the charged strings having a net charge q 1 +q 2 ≠ 0. The consistency of theory demands that the background electric field does not exceed its critical value. The distance between the mass levels of the neutral open string decreases (1-e 2 ) times in comparison with the free string, where e is the dimensionless strength of the electric field. The magnetic field does not affect this distance. It is shown that at a classical level the squared mass of the neutral open string has a tachyonic contribution due to the motion of the string as a whole in transverse directions. The tachyonic term disappears if one considers, instead of M 2 , the string energy in a special reference frame where the projection of the total canonical momentum of the string onto the electric field vanishes. The contributions due to zero point fluctuations to the energy spectrum of the neutral string and to the Virasoro operators in the theory of charged string are found

  15. String duality and novel theories without gravity

    International Nuclear Information System (INIS)

    Kachru, Shamit

    1998-01-01

    We describe some of the novel 6d quantum field theories which have been discovered in studies of string duality. The role these theories (and their 4d descendants) may play in alleviating the vacuum degeneracy problem in string theory is reviewed. The DLCQ of these field theories is presented as one concrete way of formulating them, independent of string theory

  16. Transverse structure of the QCD string

    International Nuclear Information System (INIS)

    Meyer, Harvey B.

    2010-01-01

    The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is a particularly natural probe at next-to-leading order. Second, we derive the constraints imposed by open-closed string duality on the transverse structure of the string. We show that a total of three independent ''gravitational'' form factors characterize the transverse profile of the closed string, and obtain the interpretation of recent effective string theory calculations: the square radius of a closed string of length β defined from the slope of its gravitational form factor, is given by (d-1/2πσ)log(β/4r 0 ) in d space dimensions. This is to be compared with the well-known result that the width of the open string at midpoint grows as (d-1/2πσ)log(r/r 0 ). We also obtain predictions for transition form factors among closed-string states.

  17. Architectures and representations for string transduction

    NARCIS (Netherlands)

    Chrupala, Grzegorz

    2015-01-01

    String transduction problems are ubiquitous in natural language processing: they include transliteration, grapheme-to-phoneme conversion, text normalization and translation. String transduction can be reduced to the simpler problems of sequence labeling by expressing the target string as a sequence

  18. The issue of supersymmetry breaking in strings

    International Nuclear Information System (INIS)

    Binetruy, P.

    1989-12-01

    We discuss the central role that supersymmetry plays in string models, both in spacetime and at the level of the string world-sheet. The problems associated with supersymmetry-breaking are reviewed together with some of the attempts to solve them, in the string as well as the field theory approach

  19. General relativity invariance and string field theory

    International Nuclear Information System (INIS)

    Aref'eva, I.Ya.; Volovich, I.V.

    1987-04-01

    The general covariance principle in the string field theory is considered. The algebraic properties of the string Lie derivative are discussed. The string vielbein and spin connection are introduced and an action invariant under general co-ordinate transformation is proposed. (author). 18 refs

  20. String loop divergences and effective lagrangians

    International Nuclear Information System (INIS)

    Fischler, W.; Klebanov, I.; Susskind, L.

    1988-01-01

    We isolate logarithmic divergences from bosonic string amplitudes on a disc. These divergences are compared with 'tadpole' divergences in the effective field theory, with a covariant cosmological term implied by the counting of string coupling constants. We find an inconsistency between the two. This might be a problem in eliminating divergences from the bosonic string. (orig.)

  1. Test particle trajectories near cosmic strings

    Indian Academy of Sciences (India)

    Gauge strings have their energy concentrated in a very thin tube, the radius of which is of the order of the symmetry- breaking scale whereas the global strings are such that their energy extends to regions far beyond the central core. Strings have an important astrophysical consequence, namely, the double quasar problem ...

  2. Introduction to the theory of strings

    International Nuclear Information System (INIS)

    Peskin, M.E.

    1985-10-01

    These lectures present, from an introductory perspective, some basic aspects of the quantum theory of strings. They treat (1) the kinematics, spectrum, and scattering amplitude of the bosonic string, (2) the spectrum and supersymmetry of Green-Schwarz superstring, and (3) the identification of the underlying gauge invariances of the string theory. 43 refs

  3. Syntactic transfer in artificial grammar learning.

    Science.gov (United States)

    Beesley, T; Wills, A J; Le Pelley, M E

    2010-02-01

    In an artificial grammar learning (AGL) experiment, participants were trained with instances of one grammatical structure before completing a test phase in which they were required to discriminate grammatical from randomly created strings. Importantly, the underlying structure used to generate test strings was different from that used to generate the training strings. Despite the fact that grammatical training strings were more similar to nongrammatical test strings than they were to grammatical test strings, this manipulation resulted in a positive transfer effect, as compared with controls trained with nongrammatical strings. It is suggested that training with grammatical strings leads to an appreciation of set variance that aids the detection of grammatical test strings in AGL tasks. The analysis presented demonstrates that it is useful to conceptualize test performance in AGL as a form of unsupervised category learning.

  4. Bianchi type I string cosmologies

    Indian Academy of Sciences (India)

    By making use of Letelier's form of energy–momentum tensor for a cloud of stringdust we present some classes of solutions of general relativistic field equations which describe cosmological string-dust models in Bianchi type I space-time. Some of the classes of models obey Takabayashi's equation of state whereas a class ...

  5. Defect branes as Alice strings

    International Nuclear Information System (INIS)

    Okada, Takashi; Sakatani, Yuho

    2015-01-01

    There exist various defect-brane backgrounds in supergravity theories which arise as the low energy limit of string theories. These backgrounds typically have non-trivial monodromies, and if we move a charged probe around the center of a defect, its charge will be changed by the action of the monodromy. During the process, the charge conservation law seems to be violated. In this paper, to resolve this puzzle, we examine a dynamics of the charge changing process and show that the missing charge of the probe is transferred to the background. We then explicitly construct the resultant background after the charge transfer process by utilizing dualities. This background has the same monodromy as the original defect brane, but has an additional charge which does not have any localized source. In the literature, such a charge without localized source is known to appear in the presence of Alice strings. We argue that defect branes can in fact be regarded as a realization of Alice strings in string theory and examine the charge transfer process from that perspective.

  6. String formation beyond leading colour

    Energy Technology Data Exchange (ETDEWEB)

    Christiansen, Jesper R. [Department of Astronomy and Theoretical Physics, Lund University,Sölvegatan 14, Lund (Sweden); Theoretical Physics, CERN,CH-1211, Geneva 23 (Switzerland); Skands, Peter Z. [Theoretical Physics, CERN,CH-1211, Geneva 23 (Switzerland); School of Physics and Astronomy, Monash University,VIC-3800 (Australia)

    2015-08-03

    We present a new model for the hadronisation of multi-parton systems, in which colour correlations beyond leading N{sub C} are allowed to influence the formation of confining potentials (strings). The multiplet structure of SU(3) is combined with a minimisation of the string potential energy, to decide between which partons strings should form, allowing also for “baryonic” configurations (e.g., two colours can combine coherently to form an anticolour). In e{sup +}e{sup −}collisions, modifications to the leading-colour picture are small, suppressed by both colour and kinematics factors. But in pp collisions, multi-parton interactions increase the number of possible subleading connections, counteracting their naive 1/N{sub C}{sup 2} suppression. Moreover, those that reduce the overall string lengths are kinematically favoured. The model, which we have implemented in the PYTHIA 8 generator, is capable of reaching agreement not only with the important 〈p{sub ⊥}〉(n{sub charged}) distribution but also with measured rates (and ratios) of kaons and hyperons, in both ee and pp collisions. Nonetheless, the shape of their p{sub ⊥} spectra remains challenging to explain.

  7. Monads, strings, and M theory

    NARCIS (Netherlands)

    Hofman, C.; Park, J.-S.

    1997-01-01

    The recent developmen ts in string theory suggest that the space-time coordinates should be generalized to non-comm uting matrices. P ostulating this suggestion as the fun- damen tal geometrical principle, w e form ulate a candidate for covariant second quantized RNS superstrings as a topological

  8. Topological strings and quantum curves

    NARCIS (Netherlands)

    Hollands, L.

    2009-01-01

    This thesis presents several new insights on the interface between mathematics and theoretical physics, with a central role for Riemann surfaces. First of all, the duality between Vafa-Witten theory and WZW models is embedded in string theory. Secondly, this model is generalized to a web of

  9. String theory and cosmological singularities

    Indian Academy of Sciences (India)

    Well-known examples are singularities inside black holes and initial or final singularities in expanding or contracting universes. In recent times, string theory is providing new perspectives of such singularities which may lead to an understanding of these in the standard framework of time evolution in quantum mechanics.

  10. Probing the string winding sector

    Energy Technology Data Exchange (ETDEWEB)

    Aldazabal, Gerardo; Mayo, Martín [G. Física CAB-CNEA and CONICET, Centro Atómico Bariloche,Av. Bustillo 9500, Bariloche (Argentina); Instituto Balseiro, Centro Atómico Bariloche,Av. Bustillo 9500, Bariloche (Argentina); Nuñez, Carmen [Instituto de Astronomía y Física del Espacio (CONICET-UBA),C.C. 67 - Suc. 28, 1428 Buenos Aires (Argentina); Departamento de Física, FCEN, Universidad de Buenos Aires,C.C. 67 - Suc. 28, 1428 Buenos Aires (Argentina)

    2017-03-17

    We probe a slice of the massive winding sector of bosonic string theory from toroidal compactifications of Double Field Theory (DFT). This string subsector corresponds to states containing one left and one right moving oscillators. We perform a generalized Kaluza Klein compactification of DFT on generic 2n-dimensional toroidal constant backgrounds and show that, up to third order in fluctuations, the theory coincides with the corresponding effective theory of the bosonic string compactified on n-dimensional toroidal constant backgrounds, obtained from three-point amplitudes. The comparison between both theories is facilitated by noticing that generalized diffeomorphisms in DFT allow to fix generalized harmonic gauge conditions that help in identifying the physical degrees of freedom. These conditions manifest as conformal anomaly cancellation requirements on the string theory side. The explicit expression for the gauge invariant effective action containing the physical massless sector (gravity+antisymmetric+gauge+ scalar fields) coupled to towers of generalized Kaluza Klein massive states (corresponding to compact momentum and winding modes) is found. The action acquires a very compact form when written in terms of fields carrying O(n,n) indices, and is explicitly T-duality invariant. The global algebra associated to the generalized Kaluza Klein compactification is discussed.

  11. Genus g temperature string theory

    International Nuclear Information System (INIS)

    Murphy, P.; Sen, S.

    1989-01-01

    The geometric approach to bosonic temperature string theory for genus g is formulated in the operator approach of Vafa. It is shown that the Hagedorn temperature exists for all genus g and a conjectured genus g expression for superstring theories with temperature is constructed. (orig.)

  12. The Science of String Instruments

    CERN Document Server

    Rossing, Thomas D

    2010-01-01

    Many performing musicians, as well as instrument builders, are coming to realize the importance of understanding the science of musical instruments. This book explains how string instruments produce sound. It presents basic ideas in simple language, and it also translates some more sophisticated ideas in non-technical language. It should be of interest to performers, researchers, and instrument makers alike.

  13. String theory in the bathtub

    CERN Multimedia

    CERN. Geneva

    2014-01-01

    The presence of the surrounding medium makes their dynamics dramatically different from those of ordinary string-like objects propagating in empty space, leading to quite peculiar phenomena, observed in experiments and simulations. I will argue that the effective theory provides an optimal theoretical framework to understand such phenomena, and to make precise quantitative predictions about them.

  14. Strings, fields and critical phenomena

    International Nuclear Information System (INIS)

    Ambjoern, J.

    1987-07-01

    The connection between field theory and critical phenomena is reviewed. Emphasis is put on the use of Monte Carlo methods in the study of non-perturbative aspects of field theory. String theory is then described as a statistical theory of random surfaces and the critical behaviour is analyzed both by analytical and numerical methods. (orig.)

  15. Modified Steiner functional string action

    International Nuclear Information System (INIS)

    Baillie, C.F.; Johnston, D.A.

    1992-01-01

    It has recently been suggested by Ambartzumian et al. that the modified Steiner functional has desirable properties as an action for random surfaces and hence string world sheets. We perform a simulation of this action on a dynamically triangulated random surface to investigate this claim and find that the surfaces are in a flat phase

  16. Bianchi type I string cosmologies

    Indian Academy of Sciences (India)

    if a proper initial condition, viz., inflation is imposed on the very early universe. Various types of inflationary cosmologies are being considered and the string cosmology is one. It is generally believed that the very early universe underwent phase transitions, which gave rise to topologically stable structures; of particular ...

  17. Topological Strings and Integrable Hierarchies

    CERN Document Server

    Aganagic, M; Klemm, A D; Marino, M; Vafa, C; Aganagic, Mina; Dijkgraaf, Robbert; Klemm, Albrecht; Marino, Marcos; Vafa, Cumrun

    2006-01-01

    We consider the topological B-model on local Calabi-Yau geometries. We show how one can solve for the amplitudes by using W-algebra symmetries which encodes the symmetries of holomorphic diffeomorphisms of the Calabi-Yau. In the highly effective fermionic/brane formulation this leads to a free fermion description of the amplitudes. Furthermore we argue that topological strings on Calabi-Yau geometries provide a unifying picture connecting non-critical (super)strings, integrable hierarchies, and various matrix models. In particular we show how the ordinary matrix model, the double scaling limit of matrix models, and Kontsevich-like matrix model are all related and arise from studying branes in specific local Calabi-Yau three-folds. We also show how A-model topological string on P^1 and local toric threefolds (and in particular the topological vertex) can be realized and solved as B-model topological string amplitudes on a Calabi-Yau manifold.

  18. Ultrasensitive string-based temperature sensors

    DEFF Research Database (Denmark)

    Larsen, Tom; Schmid, Silvan; Gronberg, L.

    2011-01-01

    microstrings was measured. The relative change in resonant frequency per temperature change of -1.74 +/- 0.04%/ degrees C of the aluminum strings is more than one order of magnitude higher than of the silicon nitride strings and of comparable state-of-the-art AuPd strings.......Resonant strings are a promising concept for ultra sensitive temperature detection. We present an analytical model for the sensitivity with which we optimize the temperature response of resonant strings by varying geometry and material. The temperature sensitivity of silicon nitride and aluminum...

  19. Testing problem solving in turkey vultures (Cathartes aura) using the string-pulling test.

    Science.gov (United States)

    Ellison, Anne Margaret; Watson, Jane; Demers, Eric

    2015-01-01

    To examine problem solving in turkey vultures (Cathartes aura), six captive vultures were presented with a string-pulling task, which involved drawing a string up to access food. This test has been used to assess cognition in many bird species. A small piece of meat suspended by a string was attached to a perch. Two birds solved the problem without apparent trial-and-error learning; a third bird solved the problem after observing a successful bird, suggesting that this individual learned from the other vulture. The remaining birds failed to complete the task. The successful birds significantly reduced the time needed to solve the task from early trials compared to late trials, suggesting that they had learned to solve the problem and improved their technique. The successful vultures solved the problem in a novel way: they pulled the string through their beak with their tongue, and may have gathered the string in their crop until the food was in reach. In contrast, ravens, parrots and finches use a stepwise process; they pull the string up, tuck it under foot, and reach down to pull up another length. As scavengers, turkey vultures use their beak for tearing and ripping at carcasses, but possess large, flat, webbed feet that are ill-suited to pulling or grasping. The ability to solve this problem and the novel approach used by the turkey vultures in this study may be a result of the unique evolutionary pressures imposed on this scavenging species.

  20. String Theory and M-Theory

    Science.gov (United States)

    Becker, Katrin; Becker, Melanie; Schwarz, John H.

    String theory is one of the most exciting and challenging areas of modern theoretical physics. This book guides the reader from the basics of string theory to recent developments. It introduces the basics of perturbative string theory, world-sheet supersymmetry, space-time supersymmetry, conformal field theory and the heterotic string, before describing modern developments, including D-branes, string dualities and M-theory. It then covers string geometry and flux compactifications, applications to cosmology and particle physics, black holes in string theory and M-theory, and the microscopic origin of black-hole entropy. It concludes with Matrix theory, the AdS/CFT duality and its generalizations. This book is ideal for graduate students and researchers in modern string theory, and will make an excellent textbook for a one-year course on string theory. It contains over 120 exercises with solutions, and over 200 homework problems with solutions available on a password protected website for lecturers at www.cambridge.org/9780521860697. Comprehensive coverage of topics from basics of string theory to recent developments Ideal textbook for a one-year course in string theory Includes over 100 exercises with solutions Contains over 200 homework problems with solutions available to lecturers on-line

  1. Annotating the structure and components of a nanoparticle formulation using computable string expressions.

    Science.gov (United States)

    Thomas, Dennis G; Chikkagoudar, Satish; Chappell, Alan R; Baker, Nathan A

    2012-12-31

    Nanoparticle formulations that are being developed and tested for various medical applications are typically multi-component systems that vary in their structure, chemical composition, and function. It is difficult to compare and understand the differences between the structural and chemical descriptions of hundreds and thousands of nanoparticle formulations found in text documents. We have developed a string nomenclature to create computable string expressions that identify and enumerate the different high-level types of material parts of a nanoparticle formulation and represent the spatial order of their connectivity to each other. The string expressions are intended to be used as IDs, along with terms that describe a nanoparticle formulation and its material parts, in data sharing documents and nanomaterial research databases. The strings can be parsed and represented as a directed acyclic graph. The nodes of the graph can be used to display the string ID, name and other text descriptions of the nanoparticle formulation or its material part, while the edges represent the connectivity between the material parts with respect to the whole nanoparticle formulation. The different patterns in the string expressions can be searched for and used to compare the structure and chemical components of different nanoparticle formulations. The proposed string nomenclature is extensible and can be applied along with ontology terms to annotate the complete description of nanoparticles formulations.

  2. String theory as a Lilliputian world

    International Nuclear Information System (INIS)

    Ambjørn, J.; Makeenko, Y.

    2016-01-01

    Lattice regularizations of the bosonic string do not allow us to probe the tachyon. This has often been viewed as the reason why these theories have never managed to make any contact to standard continuum string theories when the dimension of spacetime is larger than two. We study the continuum string theory in large spacetime dimensions where simple mean field theory is reliable. By keeping carefully the cutoff we show that precisely the existence of a tachyon makes it possible to take a scaling limit which reproduces the lattice-string results. We compare this scaling limit with another scaling limit which reproduces standard continuum-string results. If the people working with lattice regularizations of string theories are akin to Gulliver they will view the standard string-world as a Lilliputian world no larger than a few lattice spacings.

  3. String theory as a Lilliputian world

    Energy Technology Data Exchange (ETDEWEB)

    Ambjørn, J., E-mail: ambjorn@nbi.dk [The Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); IMAPP, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen (Netherlands); Makeenko, Y., E-mail: makeenko@nbi.dk [The Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117218 Moscow (Russian Federation)

    2016-05-10

    Lattice regularizations of the bosonic string do not allow us to probe the tachyon. This has often been viewed as the reason why these theories have never managed to make any contact to standard continuum string theories when the dimension of spacetime is larger than two. We study the continuum string theory in large spacetime dimensions where simple mean field theory is reliable. By keeping carefully the cutoff we show that precisely the existence of a tachyon makes it possible to take a scaling limit which reproduces the lattice-string results. We compare this scaling limit with another scaling limit which reproduces standard continuum-string results. If the people working with lattice regularizations of string theories are akin to Gulliver they will view the standard string-world as a Lilliputian world no larger than a few lattice spacings.

  4. Dynamical AdS strings across horizons

    Energy Technology Data Exchange (ETDEWEB)

    Ishii, Takaaki [University of Colorado,390 UCB, Boulder, CO 80309 (United States); Murata, Keiju [Keio University,4-1-1 Hiyoshi, Yokohama 223-8521 (Japan)

    2016-03-07

    We examine the nonlinear classical dynamics of a fundamental string in anti-de Sitter spacetime. The string is dual to the flux tube between an external quark-antiquark pair in N=4 super Yang-Mills theory. We perturb the string by shaking the endpoints and compute its time evolution numerically. We find that with sufficiently strong perturbations the string continues extending and plunges into the Poincaré horizon. In the evolution, effective horizons are also dynamically created on the string worldsheet. The quark and antiquark are thus causally disconnected, and the string transitions to two straight strings. The forces acting on the endpoints vanish with a power law whose slope depends on the perturbations. The condition for this transition to occur is that energy injection exceeds the static energy between the quark-antiquark pair.

  5. Implementing and measuring safety goals and safety culture. 2. Extensive Efforts to Learn Lessons from Overseas Nuclear Power Plants

    International Nuclear Information System (INIS)

    Maki, Nobuo

    2001-01-01

    The transfer of nuclear power plant (NPP) operating experiences is one of the important measures for the safe operation of NPPs. The Institute of Nuclear Power Operations (INPO),World Association of Nuclear Operators (WANO), and Nuclear Information Center of Central Research Institute of Electric Power Industry are the organizations providing Japanese utilities with useful information on incidents and accidents that have occurred at foreign NPPs. The Kansai Electric Power Company (KEPCO) has established two organizations to make extensive efforts to learn lessons from overseas NPPs: One is the Nuclear Power Plant Maintenance Training Center (MTC), and the other is the Institute of Nuclear Safety System (INSS). This paper describes the function of these organizations in transferring knowledge and expertise to ensure the safe operation of Japanese NPPs as well as recent outcomes. MTC was set up in October 1983. Before its establishment, expertise on NPP maintenance was mainly transferred on an on-the-job basis through daily maintenance work. However, after various NPP incidents and accidents, the importance of off-site training for maintenance personnel was emphasized. MTC possesses full-sized or nearly full sized mockups of Mihama NPP Unit 3 and Takahama NPP Unit 3. Furthermore, many kinds of mechanical, electrical, and instrumental equipment are furnished for training. In 1999, more than 2400 (man/day) maintenance personnel in total had training at MTC. In the tube rupture accident of a steam generator of KEPCO's Mihama Unit 2 on February 9, 1991, the emergency core cooling system actuated for the first time in the history of NPP operation in Japan. The cause of the accident was a fault in the manufacturing process of the steam generator, which was not detected until the accident. After an in-depth evaluation of the accident, many corrective actions were taken to prevent the recurrence of a similar accident. As a part of the actions, KEPCO established INSS in March

  6. Remarks on entanglement entropy in string theory

    Science.gov (United States)

    Balasubramanian, Vijay; Parrikar, Onkar

    2018-03-01

    Entanglement entropy for spatial subregions is difficult to define in string theory because of the extended nature of strings. Here we propose a definition for bosonic open strings using the framework of string field theory. The key difference (compared to ordinary quantum field theory) is that the subregion is chosen inside a Cauchy surface in the "space of open string configurations." We first present a simple calculation of this entanglement entropy in free light-cone string field theory, ignoring subtleties related to the factorization of the Hilbert space. We reproduce the answer expected from an effective field theory point of view, namely a sum over the one-loop entanglement entropies corresponding to all the particle-excitations of the string, and further show that the full string theory regulates ultraviolet divergences in the entanglement entropy. We then revisit the question of factorization of the Hilbert space by analyzing the covariant phase-space associated with a subregion in Witten's covariant string field theory. We show that the pure gauge (i.e., BRST exact) modes in the string field become dynamical at the entanglement cut. Thus, a proper definition of the entropy must involve an extended Hilbert space, with new stringy edge modes localized at the entanglement cut.

  7. Matrix strings in weakly curved background fields

    International Nuclear Information System (INIS)

    Schiappa, Ricardo

    2001-01-01

    We investigate further the recent proposal for the form of the Matrix theory action in weak background fields. We perform DVV reduction to the multiple D0-brane action in order to find the Matrix string theory action for multiple fundamental strings in curved but weak NSNS and RR backgrounds. This matrix sigma model gives a definite prescription on how to deal with RR fields with an explicit spacetime dependence in Type II string theory. We do this both via the 9-11 flip and the chain of T and S dualities, and further check on their equivalence explicitly. In order to do so, we also discuss the implementation of S-duality in the operators of the 2-dimensional worldvolume supersymmetric gauge theory describing the Type IIB D-string. We compare the result to the known Green-Schwarz sigma model action (for one string), and use this comparison in order to discuss about possible, non-linear background curvature corrections to the Matrix string action (involving many strings), and therefore to the Matrix theory action. We illustrate the nonabelian character of our action with an example involving multiple fundamental strings in a nontrivial RR flux, where the strings are polarized into a noncommutative configuration. This corresponds to a dielectric type of effect on fundamental strings

  8. Zebra finches can use positional and transitional cues to distinguish vocal element strings.

    Science.gov (United States)

    Chen, Jiani; Ten Cate, Carel

    2015-08-01

    Learning sequences is of great importance to humans and non-human animals. Many motor and mental actions, such as singing in birds and speech processing in humans, rely on sequential learning. At least two mechanisms are considered to be involved in such learning. The chaining theory proposes that learning of sequences relies on memorizing the transitions between adjacent items, while the positional theory suggests that learners encode the items according to their ordinal position in the sequence. Positional learning is assumed to dominate sequential learning. However, human infants exposed to a string of speech sounds can learn transitional (chaining) cues. So far, it is not clear whether birds, an increasingly important model for examining vocal processing, can do this. In this study we use a Go-Nogo design to examine whether zebra finches can use transitional cues to distinguish artificially constructed strings of song elements. Zebra finches were trained with sequences differing in transitional and positional information and next tested with novel strings sharing positional and transitional similarities with the training strings. The results show that they can attend to both transitional and positional cues and that their sequential coding strategies can be biased toward transitional cues depending on the learning context. This article is part of a Special Issue entitled: In Honor of Jerry Hogan. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Persistent homology and string vacua

    Energy Technology Data Exchange (ETDEWEB)

    Cirafici, Michele [Center for Mathematical Analysis, Geometry and Dynamical Systems,Instituto Superior Técnico, Universidade de Lisboa,Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Institut des Hautes Études Scientifiques,Le Bois-Marie, 35 route de Chartres, F-91440 Bures-sur-Yvette (France)

    2016-03-08

    We use methods from topological data analysis to study the topological features of certain distributions of string vacua. Topological data analysis is a multi-scale approach used to analyze the topological features of a dataset by identifying which homological characteristics persist over a long range of scales. We apply these techniques in several contexts. We analyze N=2 vacua by focusing on certain distributions of Calabi-Yau varieties and Landau-Ginzburg models. We then turn to flux compactifications and discuss how we can use topological data analysis to extract physical information. Finally we apply these techniques to certain phenomenologically realistic heterotic models. We discuss the possibility of characterizing string vacua using the topological properties of their distributions.

  10. On noncommutative open string theories

    International Nuclear Information System (INIS)

    Russo, J.G.; Sheikh-Jabbari, M.M.

    2000-08-01

    We investigate new compactifications of OM theory giving rise to a 3+1 dimensional open string theory with noncommutative x 0 -x 1 and x 2 -x 3 coordinates. The theory can be directly obtained by starting with a D3 brane with parallel (near critical) electric and magnetic field components, in the presence of a RR scalar field. The magnetic parameter permits to interpolate continuously between the x 0 -x 1 noncommutative open string theory and the x 2 -x 3 spatial noncommutative U(N) super Yang-Mills theory. We discuss SL(2, Z) transformations of this theory. Using the supergravity description of the large N limit, we also compute corrections to the quark-antiquark Coulomb potential arising in the NCOS theory. (author)

  11. Electric drill-string telemetry

    CERN Document Server

    Carcione, J M

    2003-01-01

    We design a numerical algorithm for simulation of low-frequency electric-signal transmission through a drill string. This is represented by a transmission line with varying geometrical and electromagnetic properties versus depth, depending on the characteristics of the drill-string/formation system. These properties are implicitly modeled by the series impedance and the shunt admittance of the transmission line. The differential equations are parabolic, since at low frequencies the wave field is diffusive. We use an explicit scheme for the solution of parabolic problems, based on a Chebyshev expansion of the evolution operator and the Fourier pseudospectral method to compute the spatial derivatives. The results are verified by comparison to analytical solutions obtained for the initial-value problem with a voltage source.

  12. Wrapping rules (in) string theory

    Science.gov (United States)

    Bergshoeff, Eric A.; Riccioni, Fabio

    2018-01-01

    In this paper we show that the number of all 1/2-BPS branes in string theory compactified on a torus can be derived by universal wrapping rules whose formulation we present. These rules even apply to branes in less than ten dimensions whose ten-dimensional origin is an exotic brane. In that case the wrapping rules contain an additional combinatorial factor that is related to the highest dimension in which the ten-dimensional exotic brane, after compactification, can be realized as a standard brane. We show that the wrapping rules also apply to cases with less supersymmetry. As a specific example, we discuss the compactification of IIA/IIB string theory on ( T 4/ ℤ 2) × T n .

  13. Chronology protection in string theory

    International Nuclear Information System (INIS)

    Dyson, Lisa

    2004-01-01

    Many solutions of General Relativity appear to allow the possibility of time travel. This was initially a fascinating discovery, but geometries of this type violate causality, a basic physical law which is believed to be fundamental. Although string theory is a proposed fundamental theory of quantum gravity, geometries with closed timelike curves have resurfaced as solutions to its low energy equations of motion. In this paper, we will study the class of solutions to low energy effective supergravity theories related to the BMPV black hole and the rotating wave-D1-D5-brane system. Time travel appears to be possible in these geometries. We will attempt to build the causality violating regions and propose that stringy effects prohibit their construction. The proposed chronology protection agent for these geometries mirrors a mechanism string theory employs to resolve a class of naked singularities. (author)

  14. LHC magnet string in 1994

    CERN Multimedia

    1994-01-01

    On 6-7 December 1994, a string of powerful superconducting magnets for CERN's next particle accelerator, the Large Hadron Collider (LHC), ran successfully at 8.36 tesla for 24 hours. This magnetic field is 100 000 times that of the Earth and is required to keep beams of protons travelling on the correct circular path over 27 km at 7 TeV in the new LHC accelerator.

  15. Algebras, lattices and strings 1986

    International Nuclear Information System (INIS)

    Olive, D.

    1987-01-01

    The formulation of the string theory of unified elementary particle interactions in terms of operators in a Fock space is now seen to relate to the representation theory of certain infinite dimensional algebras. This insight has enhanced the understanding of the physical and mathematical theories involved and furthermore has led to applications in other branches of theoretical physics. A brief account of the new results is given here. (orig.)

  16. Bosonization methods in string theory

    International Nuclear Information System (INIS)

    Abdalla, E.

    1988-02-01

    The use of bosonization/fermionization techniques to convert non-linear operators of the dual, is discussed. Non abelian bosonization to the case where the central charge of the Kac-Moody algebra is not unity, is generalized. In particular, using this generalization of non-abelian bosonization, the bosonic string vertex of the compactified theory; turns out to be fundamental field of thre fermionic theory, or bound states of it thus permiting explicit computations easily. (author) [pt

  17. Apparatus and method for vibrating a casing string during cementing

    International Nuclear Information System (INIS)

    Rankin, R.E.; Rankin, K.T.

    1992-01-01

    This patent describes a method of cementing a string of casing in a well. It comprises: securing a vibrating device into the string of casing near the lower end of the string of casing; lowering the string of casing into the well to the desired depth; pumping a cement slurry down the string of casing; causing a portion of the cement slurry being pumped down the string of casing to vibrate the vibrating device; and wherein the vibrating device is secured in the string of casing by cementing the vibrating device within a sub, then securing the sub into the string of casing prior to lowering the string of casing into the well

  18. Thermal excitation spectrum from entanglement in an expanding quantum string

    Science.gov (United States)

    Berges, Jürgen; Floerchinger, Stefan; Venugopalan, Raju

    2018-03-01

    A surprising result in e+e- collisions is that the particle spectra from the string formed between the expanding quark-antiquark pair have thermal properties even though scatterings appear not to be frequent enough to explain this. We address this problem by considering the finite observable interval of a relativistic quantum string in terms of its reduced density operator by tracing over the complement region. We show how quantum entanglement in the presence of a horizon in spacetime for the causal transfer of information leads locally to a reduced mixed-state density operator. For very early proper time τ, we show that the entanglement entropy becomes extensive and scales with the rapidity. At these early times, the reduced density operator is of thermal form, with an entanglement temperature Tτ = ħ / (2 πkB τ), even in the absence of any scatterings.

  19. Supersymmetry and string theory beyond the standard model

    CERN Document Server

    Dine, Michael

    2015-01-01

    The past decade has witnessed dramatic developments in the fields of experimental and theoretical particle physics and cosmology. This fully updated second edition is a comprehensive introduction to these recent developments and brings this self-contained textbook right up to date. Brand new material for this edition includes the groundbreaking Higgs discovery, results of the WMAP and Planck experiments. Extensive discussion of theories of dynamical electroweak symmetry breaking and a new chapter on the landscape, as well as a completely rewritten coda on future directions gives readers a modern perspective on this developing field. A focus on three principle areas: supersymmetry, string theory, and astrophysics and cosmology provide the structure for this book which will be of great interest to graduates and researchers in the fields of particle theory, string theory, astrophysics and cosmology. The book contains several problems, and password-protected solutions will be available to lecturers at www.cambrid...

  20. Thermal excitation spectrum from entanglement in an expanding quantum string

    Directory of Open Access Journals (Sweden)

    Jürgen Berges

    2018-03-01

    Full Text Available A surprising result in e+e− collisions is that the particle spectra from the string formed between the expanding quark–antiquark pair have thermal properties even though scatterings appear not to be frequent enough to explain this. We address this problem by considering the finite observable interval of a relativistic quantum string in terms of its reduced density operator by tracing over the complement region. We show how quantum entanglement in the presence of a horizon in spacetime for the causal transfer of information leads locally to a reduced mixed-state density operator. For very early proper time τ, we show that the entanglement entropy becomes extensive and scales with the rapidity. At these early times, the reduced density operator is of thermal form, with an entanglement temperature Tτ=ħ/(2πkBτ, even in the absence of any scatterings.

  1. Cosmological Consequences of String Axions

    Energy Technology Data Exchange (ETDEWEB)

    Kain, Ben

    2005-12-15

    Axion fluctuations generated during inflation lead to isocurvature and non-Gaussian temperature fluctuations in the cosmic microwave background radiation. Following a previous analysis for the model independent string axion we consider the consequences of a measurement of these fluctuations for two additional string axions. We do so independent of any cosmological assumptions except for the axions being massless during inflation. The first axion has been shown to solve the strong CP problem for most compactifications of the heterotic string while the second axion, which does not solve the strong CP problem, obeys a mass formula which is independent of the axion scale. We find that if gravitational waves interpreted as arising from inflation are observed by the PLANCK polarimetry experiment with a Hubble constant during inflation of H{sub inf} {approx}> 10{sup 13} GeV the existence of the first axion is ruled out and the second axion cannot obey the scale independent mass formula. In an appendix we quantitatively justify the often held assumption that temperature corrections to the zero temperature QCD axion mass may be ignored for temperatures T {approx}< {Lambda}{sub QCD}.

  2. A different kind of string

    International Nuclear Information System (INIS)

    Caselle, Michele; Panero, Marco; Pellegrini, Roberto; Vadacchino, Davide

    2015-01-01

    In U(1) lattice gauge theory in three spacetime dimensions, the problem of confinement can be studied analytically in a semi-classical approach, in terms of a gas of monopoles with Coulomb-like interactions. In addition, this theory can be mapped to a spin model via an exact duality transformation, which allows one to perform high-precision numerical studies of the confining potential. Taking advantage of these properties, we carried out an accurate investigation of the effective string describing the low-energy properties of flux tubes in this confining gauge theory. We found striking deviations from the expected Nambu-Goto-like behavior, and, for the first time, evidence for contributions that can be described by a term proportional to the extrinsic curvature of the effective string worldsheet. Such term is allowed by Lorentz invariance, and its presence in the infrared regime of the U(1) model was indeed predicted by Polyakov several years ago. Our results show that this term scales as expected according to Polyakov’s solution, and becomes the dominant contribution to the effective string action in the continuum limit. We also demonstrate analytically that the corrections to the confining potential induced by the extrinsic curvature term can be related to the partition function of the massive perturbation of a c=1 bosonic conformal field theory. The implications of our results for SU(N) Yang-Mills theories in three and in four spacetime dimensions are discussed.

  3. Braiding knots with topological strings

    International Nuclear Information System (INIS)

    Gu, Jie

    2015-08-01

    For an arbitrary knot in a three-sphere, the Ooguri-Vafa conjecture associates to it a unique stack of branes in type A topological string on the resolved conifold, and relates the colored HOMFLY invariants of the knot to the free energies on the branes. For torus knots, we use a modified version of the topological recursion developed by Eynard and Orantin to compute the free energies on the branes from the Aganagic-Vafa spectral curves of the branes, and find they are consistent with the known colored HOMFLY knot invariants a la the Ooguri-Vafa conjecture. In addition our modified topological recursion can reproduce the correct closed string free energies, which encode the information of the background geometry. We conjecture the modified topological recursion is applicable for branes associated to hyperbolic knots as well, encouraged by the observation that the modified topological recursion yields the correct planar closed string free energy from the Aganagic-Vafa spectral curves of hyperbolic knots. This has implications for the knot theory concerning distinguishing mutant knots with colored HOMFLY invariants. Furthermore, for hyperbolic knots, we present methods to compute colored HOMFLY invariants in nonsymmetric representations of U(N). The key step in this computation is computing quantum 6j-symbols in the quantum group U q (sl N ).

  4. A different kind of string

    Science.gov (United States)

    Caselle, Michele; Panero, Marco; Pellegrini, Roberto; Vadacchino, Davide

    2015-01-01

    In U(1) lattice gauge theory in three spacetime dimensions, the problem of confinement can be studied analytically in a semi-classical approach, in terms of a gas of monopoles with Coulomb-like interactions. In addition, this theory can be mapped to a spin model via an exact duality transformation, which allows one to perform high-precision numerical studies of the confining potential. Taking advantage of these properties, we carried out an accurate investigation of the effective string describing the low-energy properties of flux tubes in this confining gauge theory. We found striking deviations from the expected Nambu-Goto-like behavior, and, for the first time, evidence for contributions that can be described by a term proportional to the extrinsic curvature of the effective string worldsheet. Such term is allowed by Lorentz invariance, and its presence in the infrared regime of the U(1) model was indeed predicted by Polyakov several years ago. Our results show that this term scales as expected according to Polyakov's solution, and becomes the dominant contribution to the effective string action in the continuum limit. We also demonstrate analytically that the corrections to the confining potential induced by the extrinsic curvature term can be related to the partition function of the massive perturbation of a c = 1 bosonic conformal field theory. The implications of our results for SU( N ) Yang-Mills theories in three and in four spacetime dimensions are discussed.

  5. A different kind of string

    Energy Technology Data Exchange (ETDEWEB)

    Caselle, Michele [Dipartimento di Fisica dell’Università di Torino and INFN - Sezione di Torino,Via P. Giuria 1, I-10125 Torino (Italy); Panero, Marco [Dipartimento di Fisica dell’Università di Torino and INFN - Sezione di Torino,Via P. Giuria 1, I-10125 Torino (Italy); Instituto de Física Téorica UAM/CSIC, Universidad Autónoma de Madrid,Calle Nicolás Cabrera 13-15, Cantoblanco E-28049 Madrid (Spain); Pellegrini, Roberto [Physics Department, Swansea University,Singleton Park, Swansea SA2 8PP (United Kingdom); Vadacchino, Davide [Dipartimento di Fisica dell’Università di Torino and INFN - Sezione di Torino,Via P. Giuria 1, I-10125 Torino (Italy)

    2015-01-20

    In U(1) lattice gauge theory in three spacetime dimensions, the problem of confinement can be studied analytically in a semi-classical approach, in terms of a gas of monopoles with Coulomb-like interactions. In addition, this theory can be mapped to a spin model via an exact duality transformation, which allows one to perform high-precision numerical studies of the confining potential. Taking advantage of these properties, we carried out an accurate investigation of the effective string describing the low-energy properties of flux tubes in this confining gauge theory. We found striking deviations from the expected Nambu-Goto-like behavior, and, for the first time, evidence for contributions that can be described by a term proportional to the extrinsic curvature of the effective string worldsheet. Such term is allowed by Lorentz invariance, and its presence in the infrared regime of the U(1) model was indeed predicted by Polyakov several years ago. Our results show that this term scales as expected according to Polyakov’s solution, and becomes the dominant contribution to the effective string action in the continuum limit. We also demonstrate analytically that the corrections to the confining potential induced by the extrinsic curvature term can be related to the partition function of the massive perturbation of a c=1 bosonic conformal field theory. The implications of our results for SU(N) Yang-Mills theories in three and in four spacetime dimensions are discussed.

  6. Resumming the string perturbation series

    Energy Technology Data Exchange (ETDEWEB)

    Grassi, Alba; Mariño, Marcos; Zakany, Szabolcs [Département de Physique Théorique et section de Mathématiques,Université de Genève, Genève, CH-1211 (Switzerland)

    2015-05-07

    We use the AdS/CFT correspondence to study the resummation of a perturbative genus expansion appearing in the type II superstring dual of ABJM theory. Although the series is Borel summable, its Borel resummation does not agree with the exact non-perturbative answer due to the presence of complex instantons. The same type of behavior appears in the WKB quantization of the quartic oscillator in Quantum Mechanics, which we analyze in detail as a toy model for the string perturbation series. We conclude that, in these examples, Borel summability is not enough for extracting non-perturbative information, due to non-perturbative effects associated to complex instantons. We also analyze the resummation of the genus expansion for topological string theory on local ℙ{sup 1}×ℙ{sup 1}, which is closely related to ABJM theory. In this case, the non-perturbative answer involves membrane instantons computed by the refined topological string, which are crucial to produce a well-defined result. We give evidence that the Borel resummation of the perturbative series requires such a non-perturbative sector.

  7. A novel string field theory solving string theory by liberating left and right movers

    International Nuclear Information System (INIS)

    Nielsen, Holger B.; Ninomiya, Masao

    2014-01-01

    We put forward ideas to a novel string field theory based on making some “objects” that essentially describe “liberated” left- and right- mover fields X L μ (τ+σ) and X R μ (τ−σ) on the string. Our novel string field theory is completely definitely different from any other string theory in as far as a “null set” of information in the string field theory Fock space has been removed relatively, to the usual string field theories. So our theory is definitely new. The main progress is that we manage to make our novel string field theory provide the correct mass square spectrum for the string. We finally suggest how to obtain the Veneziano amplitude in our model

  8. Micro string resonators as temperature sensors

    DEFF Research Database (Denmark)

    Larsen, T.; Schmid, S.; Boisen, A.

    2013-01-01

    The resonance frequency of strings is highly sensitive to temperature. In this work we have investigated the applicability of micro string resonators as temperature sensors. The resonance frequency of strings is a function of the tensile stress which is coupled to temperature by the thermal...... to the low thermal mass of the strings. A temperature resolution of 2.5×10-4 °C has been achieved with silicon nitride strings. The theoretical limit for the temperature resolution of 8×10-8 °C has not been reached yet and requires further improvement of the sensor....... expansion of the string and the frame clamping it. The sensitivity improves when the length and pre-stress are reduced and the difference in thermal expansion, Young's modulus and resonant mode are increased. At low tensile stress, the sensitivity becomes highly dependent on temperature. The investigation...

  9. String theory and quantum gravity '92

    International Nuclear Information System (INIS)

    Harvey, J.; Iengo, R.; Narain, K.S.; Randjbar Daemi, S.; Verlinde, H.

    1993-01-01

    These proceedings of the 1992 Trieste Spring School and Workshop on String Theory and Quantum Gravity contains introductions and overviews of recent work on the use of two-dimensional string inspired models in the study of black holes, a lecture on gravitational scattering at planckian energies, another on the physical properties of higher-dimensional black holes and black strings in string theory, a discussion on N=2 superconformal field theories, a lecture about the application of matrix model techniques to the study of string theory in two dimensions, and an overview of the current status and developments in string field theory. Connections with models in statistical mechanics are also discussed. These proceedings contain seven lectures and ten contributions. Refs and figs

  10. D-branes from Liouville strings

    CERN Document Server

    Ellis, Jonathan Richard; Nanopoulos, Dimitri V

    1997-01-01

    We develop quantization aspects of our Liouville approach to non-critical strings, proposing a path-integral formulation of a second quantization of string theory, that incorporates naturally the couplings of string sources to background fields. Such couplings are characteristic of macroscopic string solutions and/or D-brane theories. Resummation over world-sheet genera in the presence of stringy (\\sigma-model) soliton backgrounds, and recoil effects associated with logarithmic operators on the world sheet, play a crucial r\\^ole in inducing such sources as well-defined renormalization-group counterterms. Using our Liouville renormalization group approach, we derive the appropriate second-order equation of motion for the D brane. We discuss within this approach the appearance of open strings, whose ends carry non-trivial Chan-Paton-like quantum numbers related to the W_\\infty charges of two-dimensional string black holes.

  11. Determinants of Perceived Learning and Satisfaction in Online Business Courses: An Extension to Evaluate Differences between Qualitative and Quantitative Courses

    Science.gov (United States)

    Eastman, Jacqueline K.; Aviles, Maria; Hanna, Mark D.

    2017-01-01

    This study examined the determinants of perceived learning and satisfaction in online courses and the moderating effect of course type. For perceived learning outcomes, those students who perceive a higher level of interaction and those students who are satisfied will report higher levels of learning outcomes. There were significant differences…

  12. String and M-theory cosmology

    International Nuclear Information System (INIS)

    Copeland, E.J.

    2003-01-01

    In these lectures we review recent advances in string cosmology. Starting with the Dilaton-Moduli Cosmology (known also as the Pre Big Bang), we go on to include the effects of axion fields and address the thorny issue of the Graceful Exit in String Cosmology. This is followed by a review of density perturbations arising in string cosmology and we finish with a brief introduction to the impact moving of five branes on the Dilaton-Moduli cosmological solutions

  13. String model of black hole microstates

    International Nuclear Information System (INIS)

    Larsen, F.

    1997-01-01

    The statistical mechanics of black holes arbitrarily far from extremality is modeled by a gas of weakly interacting strings. As an effective low-energy description of black holes the string model provides several highly nontrivial consistency checks and predictions. Speculations on a fundamental origin of the model suggest surprising simplifications in nonperturbative string theory, even in the absence of supersymmetry. copyright 1997 The American Physical Society

  14. Exact solutions and singularities in string theory

    International Nuclear Information System (INIS)

    Horowitz, G.T.; Tseytlin, A.A.

    1994-01-01

    We construct two new classes of exact solutions to string theory which are not of the standard plane wave of gauged WZW type. Many of these solutions have curvature singularities. The first class includes the fundamental string solution, for which the string coupling vanishes near the singularity. This suggests that the singularity may not be removed by quantum corrections. The second class consists of hybrids of plane wave and gauged WZW solutions. We discuss a four-dimensional example in detail

  15. Time dependent viscous string cloud cosmological models

    Science.gov (United States)

    Tripathy, S. K.; Nayak, S. K.; Sahu, S. K.; Routray, T. R.

    2009-09-01

    Bianchi type-I string cosmological models are studied in Saez-Ballester theory of gravitation when the source for the energy momentum tensor is a viscous string cloud coupled to gravitational field. The bulk viscosity is assumed to vary with time and is related to the scalar expansion. The relationship between the proper energy density ρ and string tension density λ are investigated from two different cosmological models.

  16. Quantum corrections to the string Bethe ansatz

    CERN Document Server

    Hernández, R; Hernandez, Rafael; Lopez, Esperanza

    2006-01-01

    One-loop corrections to the energy of semiclassical rotating strings contain both analytic and non-analytic terms in the 't Hooft coupling. Analytic contributions agree with the prediction from the string Bethe ansatz based on the classical S-matrix, but in order to include non-analytic contributions quantum corrections are required. We find a general expression for the first quantum correction to the string Bethe ansatz.

  17. Parameterized String Matching Algorithms with Application to ...

    African Journals Online (AJOL)

    In the parameterized string matching problem, a given pattern P is said to match with a sub-string t of the text T, if there exist a bijection from the symbols of P to the symbols of t. Salmela and Tarhio solve the parameterized string matching problem in sub-linear time by applying the concept of q-gram in the Horspool algorithm ...

  18. p-adic string theories provide lattice Discretization to the ordinary string worldsheet.

    Science.gov (United States)

    Ghoshal, Debashis

    2006-10-13

    A class of models called p-adic strings is useful in understanding the tachyonic instability of string theory. These are found to be empirically related to the ordinary strings in the p-->1 limit. We propose that these models provide discretization for the string worldsheet and argue that the limit is naturally thought of as a continuum limit in the sense of the renormalization group.

  19. Matrix string models for exact (2,2) string theories in RR backgrounds

    Energy Technology Data Exchange (ETDEWEB)

    Bonelli, Giulio E-mail: gbonelli@ulb.ac.be

    2003-01-20

    We formulate matrix string models on a class of exact string backgrounds with non-constant RR-flux parameterized by a holomorphic prepotential function and with manifest (2,2) supersymmetry. This lifts these string theories to M-theory exposing the non-perturbative string interaction which is studied by generalizing the instanton asymptotic expansion, well established in the flat background case, to this more general case. We obtain also a companion matrix model with four manifest supersymmetries in eleven dimensions.

  20. The structure of arm and hand movements in a spontaneous and food rewarded on-line string-pulling task by the mouse.

    Science.gov (United States)

    Blackwell, Ashley A; Banovetz, Mark T; Qandeel; Whishaw, Ian Q; Wallace, Douglas G

    2018-06-01

    Arm and hand use by the mouse have been studied in a variety of tasks in order to understand the structure of skilled movements and motor learning, the anatomy and function of neural pathways, and to develop animal models of neurological conditions. The present study describes string-pulling by the mouse, a behavior in which a mouse uses hand-over-hand movements to pull down a string that hangs from the top of a test cage. Mice both spontaneously string-pull and also string-pull to obtain cashew nuts tied to the end of the string as food reward. To string-pull, mice sat upright and tracked the string with their nose and then made hand-over-hand movements to reel in the string. A string-pull movement consists of four arm movements (Advance to make purchase, Pull, Push to draw the string down and Lift to return the hand for the next Advance) and four hand movements (Collect to aim the hand, Overgrasp to position the hand, and Grasp to make purchase, and Release). The kinematic profiles of the string-pull movement are distinctive with each hand making similar movements at a rate of 4 cycles per second and with the Lift and Advance movements occurring at a higher speed than Pull and Push movements. The results are discussed in relation to the antecedent repertoire of mouse behavior that lends itself to string-pulling, with respect to the utility of using string-pulling to investigate motor systems and adapting string-pulling to model neurological conditions in mice. Copyright © 2018 Elsevier B.V. All rights reserved.

  1. Perturbative string theory in BRST invariant formalism

    International Nuclear Information System (INIS)

    Di Vecchia, P.; Hornfeck, K.; Frau, M.; Lerda, A.

    1988-01-01

    In this talk we present a constructive and very explicit way of calculating multiloop amplitudes in string theories. The main ingredients are the BRST invariant N String Vertex and the BRST invariant twisted propagator. This approach naturally leads to the Schottky parametrization of moduli space in terms of multipliers and fixed points of the g projective transformations which characterize a Riemann surface of genus g. The complete expression (including measure) of the multiloop corrections to the N String Vertex for the bosonic string is exhibited. (orig.)

  2. Gauge invariant actions for string models

    International Nuclear Information System (INIS)

    Banks, T.

    1986-06-01

    String models of unified interactions are elegant sets of Feynman rules for the scattering of gravitons, gauge bosons, and a host of massive excitations. The purpose of these lectures is to describe the progress towards a nonperturbative formulation of the theory. Such a formulation should make the geometrical meaning of string theory manifest and explain the many ''miracles'' exhibited by the string Feynman rules. There are some new results on gauge invariant observables, on the cosmological constant, and on the symmetries of interacting string field theory. 49 refs

  3. Pencocokan String Berdasarkan Kemiripan Ucapan (Phonetic String Matching) dalam Bahasa Inggris

    OpenAIRE

    Syaroni, Mokhamad; Munir, Rinaldi

    2009-01-01

    Perkembangan teknologi informasi dan komunikasi yang semakin pesat, mengakibatkan pencarianinformasi semakin mudah. Pencarian informasi yang tepat dan sesuai kebutuhan menjadi sangat penting. Olehkarena itu, teknik untuk memperoleh dokumen dengan isi yang sesuai dengan kebutuhan informasi sangatdiperlukan. Untuk mengetahui isi dokumen sesuai dengan kebutuhan informasi, diperlukan metode pencarianstring (string searching) isi dokumen yang bagus. Proses pencocokan string (string matching) yang ...

  4. Pencocokan String Berdasarkan Kemiripan Ucapan (Phonetic String Matching) Dalam Bahasa Inggris

    OpenAIRE

    Syaroni, Mokhamad; Munir, Rinaldi

    2005-01-01

    Perkembangan teknologi informasi dan komunikasi yang semakin pesat, mengakibatkan pencarianinformasi semakin mudah. Pencarian informasi yang tepat dan sesuai kebutuhan menjadi sangat penting. Olehkarena itu, teknik untuk memperoleh dokumen dengan isi yang sesuai dengan kebutuhan informasi sangatdiperlukan. Untuk mengetahui isi dokumen sesuai dengan kebutuhan informasi, diperlukan metode pencarianstring (string searching) isi dokumen yang bagus. Proses pencocokan string (string matching) yang ...

  5. Recent Developments in D=2 String Field Theory

    OpenAIRE

    Kaku, Michio

    1994-01-01

    In this review article, we review the recent developments in constructing string field theories that have been proposed, all of which correctly reproduce the correlation functions of two-dimensional string theory. These include: (a) free fermion field theory (b) collective string field theory (c) temporal gauge string field theory (d) non-polynomial string field theory. We analyze discrete states, the $w(\\infty)$ symmetry, and correlation functions in terms of these different string field the...

  6. An equivalence between momentum and charge in string theory

    International Nuclear Information System (INIS)

    Horne, J.H.; Horowitz, G.T.; Steif, A.R.

    1992-01-01

    It is shown that for a translationally invariant solution to string theory, spacetime duality interchanges the momentum in the symmetry direction and the axion charge per unit length. As one application, we show explicitly that charged black strings are equivalent to boosted (uncharged) black strings. The extremal black strings (which correspond to the field outside of a fundamental macroscopic string) are equivalent to plane-fronted waves describing strings moving at the speed of light

  7. A Hierarchical Network of Provably Optimal Learning Control Systems: Extensions of the Associative Control Process (ACP) Network

    Science.gov (United States)

    1993-01-01

    learning systems have been found to work well on difficult problems. Tesauro (1990, 1992) has applied these ideas successfully to the problem of play- ing...Proceedings of the American Control Conference. Boston, MA. Tesauro , G. (1990). Neurogammon: A neural-network backgammon program. Pro- Adaptive...Conference on Neural Networks, 3, 33-40. Tesauro , G. (1992). Practical issues in temporal difference learning. Machine Learning, 8(3/4), 257-277. Thrun, S

  8. Boundary string field theory and an open string one-loop

    International Nuclear Information System (INIS)

    Lee, Tae Jin; Viswanathan, K. S.; Yang, Yi

    2003-01-01

    We discuss the open string one-loop partition function in the tachyon condensation background of an unstable D-brane system. We evaluate the partition function by using the boundary-state formulation and find that it is in complete agreement with the result obtained in the boundary string field theory. This suggests that the open string higher loop diagrams may be produced consistently by using a closed string field theory, where the D-brane plays the role of a source for the closed string field

  9. On the elliptic genus of three E-strings and heterotic strings

    International Nuclear Information System (INIS)

    Cai, Wenhe; Huang, Min-xin; Sun, Kaiwen

    2015-01-01

    A precise formula for the elliptic genus of three E-strings is presented. The related refined free energy coincides with the result calculated from topological string on local half K3 Calabi-Yau threefold up to genus twelve. The elliptic genus of three heterotic strings computed from M9 domain walls matches with the result from orbifold formula to high orders. This confirms the n=3 case of the recent conjecture that n pairs of E-strings can recombine into n heterotic strings.

  10. Open strings in the SL(2, R) WZWN model with solution for a rigidly rotating string

    DEFF Research Database (Denmark)

    Lomholt, Michael Andersen; Larsen, A.L.

    2003-01-01

    then consider open string boundary conditions corresponding to a certain field-dependent gluing condition. This allows us to consider open strings with constant energy and angular momentum. Classically, these open strings naturally generalize the open strings in flat Minkowski space. For rigidly rotating open...... strings, we show that the torsion leads to a bending and an unfolding. We also derive the SL(2, R) Regge relation, which generalizes the linear Minkowski Regge relation. For "high" mass, it takes the form L ≈ ± M/H, where H is the scale of the SL(2, R) group manifold....

  11. String Motion in Fivebrane Geometry

    OpenAIRE

    Khuri, Ramzi R.; La, HoSeong

    1992-01-01

    The classical motion of a test string in the transverse space of two types of heterotic fivebrane sources is fully analyzed, for arbitrary instanton scale size. The singular case is treated as a special case and does not arise in the continuous limit of zero instanton size. We find that the orbits are either circular or open, which is a solitonic analogy with the motion of an electron around a magnetic monopole, although the system we consider is quantitatively different. We emphasize that at...

  12. A Note on Tensionless Strings in M-Theory

    OpenAIRE

    Davis, K.

    1996-01-01

    In this article we examine the appearance of tensionless strings in M-Theory. We subsequently interpret these tensionless strings in a String Theory context. In particular, we examine tensionless strings appearing in M-Theory on $S^{1}$, M-Theory on $S^{1} / {\\bf Z}_{2}$, and M-Theory on $T^{2}$; we then interpret the appearance of such strings in a String Theory context. Then we reverse this process and examine the appearance of some tensionless strings in String Theory. Subsequently we inte...

  13. Summations over equilaterally triangulated surfaces and the critical string measure

    Science.gov (United States)

    Smit, Dirk-Jan

    1992-01-01

    We propose a new approach to the summation over dynamically triangulated Riemann surfaces which does not rely on properties of the potential in a matrix model. Instead, we formulate a purely algebraic discretization of critical string path integral. This is combined with a technique which assigns to each equilateral triangulation of a two-dimensional surface a Riemann surface defined over a certain finite extension of the field of rational numbers, i.e. an arthmetic surface. Thus we establish a new formulation in which the sum over randomly triangulated surfaces defines an invariant measure on the moduli space of arithmetic surfaces. It is shown that because of this it is far from obvious that this measure for large genera approximates the measure defined by the continuum theory, i.e. Liouville theory or critical string theory. In low genus this subtlety does not exist. In the case of critical string theory we explicity compute the volume of the moduli space of arithmetic surfaces in terms of the modular height function and show that for low genus it approximates correctly the continuum measure. We also discuss a continuum limit which bears some resemblance with a double scaling limit in matrix models.

  14. Summations over equilaterally triangulated surfaces and the critical string measure

    International Nuclear Information System (INIS)

    Smit, D.J.; Lawrence Berkeley Lab., CA

    1992-01-01

    We propose a new approach to the summation over dynamically triangulated Riemann surfaces which does not rely on properties of the potential in a matrix model. Instead, we formulate a purely algebraic discretization of critical string path integral. This is combined with a technique which assigns to each equilateral triangulation of a two-dimensional surface a Riemann surface defined over a certain finite extension of the field of rational numbers, i.e. an arithmetic surface. Thus we establish a new formulated in which the sum over randomly triangulated surfaces defines an invariant measure on the moduli space of arithmetic surfaces. It is shown that because of this it is far from obvious that this measure for large genera approximates the measure defined by the continuum theory, i.e. Liouville theory or critical string theory. In low genus this subtlety does not exist. In the case of critical string theory we explicitly compute the volume of the moduli space of arithmetic surfaces in terms of the modular height function and show that for low genus it approximates correctly the continuum measure. We also discuss a continuum limit which bears some resemblance with a double scaling limit in matrix models. (orig.)

  15. BPS limit of multi- D- and DF-strings in boundary string field theory

    International Nuclear Information System (INIS)

    Go, Gyungchoon; Ishida, Akira; Kim, Yoonbai

    2007-01-01

    A BPS limit is systematically derived for straight multi- D- and DF-strings from the D3D-bar3 system in the context of boundary superstring field theory. The BPS limit is obtained in the limit of thin D(F)-strings, where the Bogomolny equation supports singular static multi-D(F)-string solutions. For the BPS multi-string configurations with arbitrary separations, BPS sum rule is fulfilled under a Gaussian type tachyon potential and reproduces exactly the descent relation. For the DF-strings ((p,q)-strings), the distribution of fundamental string charge density coincides with its energy density and the Hamiltonian density takes the BPS formula of square-root form

  16. Test particle trajectories near cosmic strings

    Indian Academy of Sciences (India)

    Phase transitions of quantum fields in the early universe produced very thin tubes of false vacuum, known as cosmic strings [1]. These are topological defects which can form when either a local or a global symmetry is spontaneously broken in a phase transition. The first one is called gauge string and the latter is called ...

  17. Hydromonochord: Visualizing String Vibration by Water Swirls

    Science.gov (United States)

    Sommer, Wilfried; Meier-Boke, Ralf; Meinzer, Nicholas

    2010-01-01

    The hydromonochord is a horizontal vibrating string that just makes contact with the surface of a water bath. The motion of the string sets up a pattern of swirls on the surface of the water, thus complementing the usual pattern of nodes and antinodes. The device is based on the traditional monochord. A water basin (Fig. 1) has two slits in the…

  18. An overview of progress in string theory

    Indian Academy of Sciences (India)

    There has been many interesting developments in string theory in last couple of years. The purpose of this article is to present a brief account of the progress made in string theory. The two invited talks by S R Das and S Mukhi in this volume contain more detailed accounts of our understanding of black hole physics and the ...

  19. Face recognition using ensemble string matching.

    Science.gov (United States)

    Chen, Weiping; Gao, Yongsheng

    2013-12-01

    In this paper, we present a syntactic string matching approach to solve the frontal face recognition problem. String matching is a powerful partial matching technique, but is not suitable for frontal face recognition due to its requirement of globally sequential representation and the complex nature of human faces, containing discontinuous and non-sequential features. Here, we build a compact syntactic Stringface representation, which is an ensemble of strings. A novel ensemble string matching approach that can perform non-sequential string matching between two Stringfaces is proposed. It is invariant to the sequential order of strings and the direction of each string. The embedded partial matching mechanism enables our method to automatically use every piece of non-occluded region, regardless of shape, in the recognition process. The encouraging results demonstrate the feasibility and effectiveness of using syntactic methods for face recognition from a single exemplar image per person, breaking the barrier that prevents string matching techniques from being used for addressing complex image recognition problems. The proposed method not only achieved significantly better performance in recognizing partially occluded faces, but also showed its ability to perform direct matching between sketch faces and photo faces.

  20. Plucked String on a Shoestring Budget

    Science.gov (United States)

    Gluck, Paul

    2009-01-01

    The physics of the plucked string has been treated in many articles and books. For our 12th-grade high school physics laboratory, we have built a cheap, simple sonometer apparatus for each pair of students on which they may investigate some interesting phenomena that arise when a string is plucked. Among these are the generation of harmonics…

  1. String field representation of the Virasoro algebra

    Czech Academy of Sciences Publication Activity Database

    Mertes, N.; Schnabl, Martin

    2016-01-01

    Roč. 2016, č. 12 (2016), 1-14, č. článku 151. ISSN 1029-8479 R&D Projects: GA ČR(CZ) GA14-31689S Institutional support: RVO:68378271 Keywords : String Held Theory * Conformal Field Models in String Theory Subject RIV: BE - Theoretical Physics Impact factor: 6.063, year: 2016

  2. EFFECTIVE ACTIONS FOR HETEROTIC STRING THEORY

    NARCIS (Netherlands)

    SUELMANN, H

    Heterotic String Theory is an attempt to construct a description of nature that is more satisfying than the Standard Model. A major problem is that it is very difficult to do explicit calculations in string theory. Therefore, it is useful to construct a 'normal' field theory that approximates HST.

  3. String Theory: Big Problem for Small Size

    Science.gov (United States)

    Sahoo, S.

    2009-01-01

    String theory is the most promising candidate theory for a unified description of all the fundamental forces that exist in nature. It provides a mathematical framework that combines quantum theory with Einstein's general theory of relativity. The typical size of a string is of the order of 10[superscript -33] cm, called the Planck length. But due…

  4. Understanding fields using strings: A review

    Indian Academy of Sciences (India)

    Understanding fields using strings: A review. SUNIL MUKHI. Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India. Abstract. In addition to being a prime candidate for a fundamental unified theory of all interactions in nature, string theory provides a natural setting to understand gauge field ...

  5. A Computer String-Grammar of English.

    Science.gov (United States)

    Sager, Naomi

    This volume is the fourth in a series of detailed reports on a working computer program for the syntactic analysis of English sentences into their component strings. The report (1) records the considerations involved in various decisions among alternative grammatical formulations and presents the word-subclasses, the linguistic strings, etc., for…

  6. Quantum Geometry of Refined Topological Strings

    NARCIS (Netherlands)

    Aganagic, M.; Cheng, M.C.N.; Dijkgraaf, R.; Kreft, D.; Vafa, C.

    2012-01-01

    We consider branes in refined topological strings. We argue that their wavefunctions satisfy a Schrödinger equation depending on multiple times and prove this in the case where the topological string has a dual matrix model description. Furthermore, in the limit where one of the equivariant

  7. Calculations in perturbative string field theory

    International Nuclear Information System (INIS)

    Thorn, C.B.

    1987-01-01

    The author discusses methods for evaluating the Feynman diagrams of string field theory, with particular emphasis on Witten's version of open string field theory. It is explained in some detail how the rules states by Giddings and Martinec for relating a given diagram to a Polyakov path integral emerge from the Feynman rules

  8. An overview of progress in string theory

    Indian Academy of Sciences (India)

    invariance of the theory. The string theories of interest to us contain massless particles in their lowest mode. For example, in 10-dimensional heterotic string theory, we have graviton, antisymmetric tensor and dilaton together with the super Yang–Mills multiplets corresponding to the gauge groups SO(32) or E x E in its ...

  9. Recent Progress in String Inflationary Cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Rey, Soo-Jong

    2003-05-23

    Super-inflation driven by dilaton/moduli kinetic energy is naturally realized in compactified string theory. Discussed are selected topics of recent development in string inflationary cosmology: kinematics of super-inflation, graceful exit triggered by quantum back reaction, and classical and quantum power spectra of density and metric perturbations.

  10. Querying and Mining Strings Made Easy

    KAUST Repository

    Sahli, Majed

    2017-10-13

    With the advent of large string datasets in several scientific and business applications, there is a growing need to perform ad-hoc analysis on strings. Currently, strings are stored, managed, and queried using procedural codes. This limits users to certain operations supported by existing procedural applications and requires manual query planning with limited tuning opportunities. This paper presents StarQL, a generic and declarative query language for strings. StarQL is based on a native string data model that allows StarQL to support a large variety of string operations and provide semantic-based query optimization. String analytic queries are too intricate to be solved on one machine. Therefore, we propose a scalable and efficient data structure that allows StarQL implementations to handle large sets of strings and utilize large computing infrastructures. Our evaluation shows that StarQL is able to express workloads of application-specific tools, such as BLAST and KAT in bioinformatics, and to mine Wikipedia text for interesting patterns using declarative queries. Furthermore, the StarQL query optimizer shows an order of magnitude reduction in query execution time.

  11. An overview of progress in string theory

    Indian Academy of Sciences (India)

    Abstract. There has been many interesting developments in string theory in last couple of years. The purpose of this article is to present a brief account of the progress made in string theory. The two invited talks by S R Das and S Mukhi in this volume contain more detailed accounts of our understanding of black hole physics ...

  12. Total cross section of highly excited strings

    International Nuclear Information System (INIS)

    Lizzi, F.; Senda, I.

    1990-01-01

    The unpolarized total cross section for the joining of two highly excited strings is calculated. The calculation is performed by taking the average overall states in the given excitation levels of the initial strings. We find that the total cross section grows with the energy and momentum of the initial states. (author). 8 refs, 1 fig

  13. String loop effect on the BRST charge

    International Nuclear Information System (INIS)

    Das, A.; Nishino, H.

    1987-07-01

    An effective BRST charge Q BRST which incorporates the string one-loop corrections is presented for the closed bosonic string in an arbitrary background. The effective σ-model action which leads to such a Q BRST is obtained and some consequences are discussed. (author). 14 refs, 1 fig

  14. Cosmic R-string in thermal history

    Energy Technology Data Exchange (ETDEWEB)

    Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Ohashi, Keisuke [Osaka City Univ. (Japan). Dept. of Mathematics and Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research

    2013-03-15

    We study stabilization of an unstable cosmic string associated with spontaneously broken U(1){sub R} symmetry, which otherwise causes a dangerous roll-over process. We demonstrate that in a gauge mediation model, messengers can receive enough corrections from the thermal plasma of the supersymmetric standard model particles to stabilize the unstable modes of the string.

  15. Confining strings revisited - a short comment

    International Nuclear Information System (INIS)

    Botelho, Luiz C.L.

    2000-03-01

    We show that Polyakov's confining string Nucl. Phys. B486, (1997) 23, is the author's previously proposed self-avoiding extrinsic strings (Luiz C.L. Botelho), Rev. Bras. Fis. 16, 279, (1986); CALTECH-preprint 68, 1444, (1987); J. Math. Phys. 30 (9), (1989), 2160). (author)

  16. Confining strings revisited - a short comment

    Energy Technology Data Exchange (ETDEWEB)

    Botelho, Luiz C.L. [Universidade Federal Rural do Rio de Janeiro, RJ (Brazil). Dept. de Fisica

    2000-03-01

    We show that Polyakov's confining string Nucl. Phys. B486, (1997) 23, is the author's previously proposed self-avoiding extrinsic strings (Luiz C.L. Botelho), Rev. Bras. Fis. 16, 279, (1986); CALTECH-preprint 68, 1444, (1987); J. Math. Phys. 30 (9), (1989), 2160. (author)

  17. String 2, test facility for the LHC

    CERN Multimedia

    Patrice Loïez

    2002-01-01

    String 2 is the long chain seen to the right, representing one complete cell of bending dipoles, focusing quadrupoles and corrector magnets. On 17 June 2002 the test string reached the nominal running current of 11 860 A and magnetic field of 8.335 T for the LHC.

  18. An investigation into the cognition behind spontaneous string pulling in New Caledonian crows.

    Directory of Open Access Journals (Sweden)

    Alex H Taylor

    Full Text Available The ability of some bird species to pull up meat hung on a string is a famous example of spontaneous animal problem solving. The "insight" hypothesis claims that this complex behaviour is based on cognitive abilities such as mental scenario building and imagination. An operant conditioning account, in contrast, would claim that this spontaneity is due to each action in string pulling being reinforced by the meat moving closer and remaining closer to the bird on the perch. We presented experienced and naïve New Caledonian crows with a novel, visually restricted string-pulling problem that reduced the quality of visual feedback during string pulling. Experienced crows solved this problem with reduced efficiency and increased errors compared to their performance in standard string pulling. Naïve crows either failed or solved the problem by trial and error learning. However, when visual feedback was available via a mirror mounted next to the apparatus, two naïve crows were able to perform at the same level as the experienced group. Our results raise the possibility that spontaneous string pulling in New Caledonian crows may not be based on insight but on operant conditioning mediated by a perceptual-motor feedback cycle.

  19. The Centre for Continuing Education and Extension Services: A Legacy of Excellence and Access to Life-long Learning

    Directory of Open Access Journals (Sweden)

    Christina Rahming-Nwosa

    2015-02-01

    Full Text Available A review of the history and evolution of the Centre for Continuing Education and Extension Services and the various programmes it has developed to support the work of the College of The Bahamas.

  20. Using Educational Theory and Research to Refine Agricultural Extension: Affordances and Barriers for Farmers' Learning and Practice Change

    Science.gov (United States)

    Sewell, A. M.; Hartnett, M. K.; Gray, D. I.; Blair, H. T.; Kemp, P. D.; Kenyon, P. R.; Morris, S. T.; Wood, B. A.

    2017-01-01

    Purpose: To examine the factors that support and hinder farmers' learning and to investigate the impact of an innovative learning program on farmers' practice change. Design/methodology/approach: Individual interviews and focus group discussions were held with 24 farmers over 20 months. Observations were made of these farmers as they participated…

  1. Strings, conformal fields and topology. An introduction

    Energy Technology Data Exchange (ETDEWEB)

    Kaku, Michio (City Coll., New York (USA). Dept. of Physics)

    1991-01-01

    String Theory has advanced at an astonishing pace in the last few years, and this book aims to acquaint the reader with the most active topics of research in the field. Building on the foundations laid in his Introduction to Superstrings, Professor Kaku discusses such topics as the classification of conformal string theories, knot theory, the Yang-Baxter relation, quantum groups, the non-polynominal closed string field theory, matrix models, and topological field theory. Several chapters review the fundamentals of string theory, making the presentation of the material self-contained while keeping overlap with the earlier book to a minimum. The book conveys the vitality of current research in string theory and places readers at its forefront. (orig.) With 40 figs. in 50 parts.

  2. Correspondence principle for black holes and strings

    International Nuclear Information System (INIS)

    Horowitz, G.T.; Polchinski, J.

    1997-01-01

    For most black holes in string theory, the Schwarzschild radius in string units decreases as the string coupling is reduced. We formulate a correspondence principle, which states that (i) when the size of the horizon drops below the size of a string, the typical black hole state becomes a typical state of strings and D-branes with the same charges, and (ii) the mass does not change abruptly during the transition. This provides a statistical interpretation of black hole entropy. This approach does not yield the numerical coefficient, but gives the correct dependence on mass and charge in a wide range of cases, including neutral black holes. copyright 1997 The American Physical Society

  3. Compressed and Practical Data Structures for Strings

    DEFF Research Database (Denmark)

    Christiansen, Anders Roy

    in the following. Finger Search in Grammar-Compressed Strings. Grammar-based compression, where one replaces a long string by a small context-free grammar that generates the string, is a simple and powerful paradigm that captures many popular compression schemes. Given a grammar, the random access problem...... string. We present new data structures that achieve optimal time for updates and queries while using space linear in the size of the optimal relative compression, for nearly all combinations of parameters. We also present solutions for restricted and extended sets of updates. To achieve these results, we...... revisit the dynamic partial sums problem and the substring concatenation problem. We present new optimal or near optimal bounds for these problems. Plugging in our new results we also immediately obtain new bounds for the string indexing for patterns with wildcards problem and the dynamic text and static...

  4. String theory of the Regge intercept.

    Science.gov (United States)

    Hellerman, S; Swanson, I

    2015-03-20

    Using the Polchinski-Strominger effective string theory in the covariant gauge, we compute the mass of a rotating string in D dimensions with large angular momenta J, in one or two planes, in fixed ratio, up to and including first subleading order in the large J expansion. This constitutes a first-principles calculation of the value for the order-J(0) contribution to the mass squared of a meson on the leading Regge trajectory in planar QCD with bosonic quarks. For open strings with Neumann boundary conditions, and for closed strings in D≥5, the order-J(0) term in the mass squared is exactly calculated by the semiclassical approximation. This term in the expansion is universal and independent of the details of the theory, assuming only D-dimensional Poincaré invariance and the absence of other infinite-range excitations on the string world volume, beyond the Nambu-Goldstone bosons.

  5. Field theory of relativistic strings: I. Trees

    International Nuclear Information System (INIS)

    Kaku, M.; Kikkawa, K.

    1985-01-01

    The authors present an entirely new kind of field theory, a field theory quantized not at space-time points, but quantized along an extended set of multilocal points on a string. This represents a significant departure from the usual quantum field theory, whose free theory represents a definite set of elementary particles, because the field theory on relativistic strings can accommodate an infinite set of linearly rising Regge trajectories. In this paper, the authors (1) present canonical quantization and the Green's function of the free string, (2) introduce three-string interactions, (3) resolve the question of multiple counting, (4) complete the counting arguments for all N-point trees, and (5) introduce four-string interactions which yield a Yang-Mills structure when the zero-slope limit is taken

  6. Knotlike cosmic strings in the early universe

    Science.gov (United States)

    Duan, Yi-shi; Liu, Xin

    2004-02-01

    In this paper, the knotlike cosmic strings in the Riemann-Cartan space-time of the early universe are discussed. It has been revealed that the cosmic strings can just originate from the zero points of the complex scalar quintessence field. In these strings we mainly study the knotlike configurations. Based on the integral of Chern-Simons 3-form a topological invariant for knotlike cosmic strings is constructed, and it is shown that this invariant is just the total sum of all the self-linking and linking numbers of the knots family. Furthermore, it is also pointed out that this invariant is preserved in the branch processes during the evolution of cosmic strings.

  7. Mirror symmetry, toric branes and topological string amplitudes as polynomials

    International Nuclear Information System (INIS)

    Alim, Murad

    2009-01-01

    The central theme of this thesis is the extension and application of mirror symmetry of topological string theory. The contribution of this work on the mathematical side is given by interpreting the calculated partition functions as generating functions for mathematical invariants which are extracted in various examples. Furthermore the extension of the variation of the vacuum bundle to include D-branes on compact geometries is studied. Based on previous work for non-compact geometries a system of differential equations is derived which allows to extend the mirror map to the deformation spaces of the D-Branes. Furthermore, these equations allow the computation of the full quantum corrected superpotentials which are induced by the D-branes. Based on the holomorphic anomaly equation, which describes the background dependence of topological string theory relating recursively loop amplitudes, this work generalizes a polynomial construction of the loop amplitudes, which was found for manifolds with a one dimensional space of deformations, to arbitrary target manifolds with arbitrary dimension of the deformation space. The polynomial generators are determined and it is proven that the higher loop amplitudes are polynomials of a certain degree in the generators. Furthermore, the polynomial construction is generalized to solve the extension of the holomorphic anomaly equation to D-branes without deformation space. This method is applied to calculate higher loop amplitudes in numerous examples and the mathematical invariants are extracted. (orig.)

  8. Mirror symmetry, toric branes and topological string amplitudes as polynomials

    Energy Technology Data Exchange (ETDEWEB)

    Alim, Murad

    2009-07-13

    The central theme of this thesis is the extension and application of mirror symmetry of topological string theory. The contribution of this work on the mathematical side is given by interpreting the calculated partition functions as generating functions for mathematical invariants which are extracted in various examples. Furthermore the extension of the variation of the vacuum bundle to include D-branes on compact geometries is studied. Based on previous work for non-compact geometries a system of differential equations is derived which allows to extend the mirror map to the deformation spaces of the D-Branes. Furthermore, these equations allow the computation of the full quantum corrected superpotentials which are induced by the D-branes. Based on the holomorphic anomaly equation, which describes the background dependence of topological string theory relating recursively loop amplitudes, this work generalizes a polynomial construction of the loop amplitudes, which was found for manifolds with a one dimensional space of deformations, to arbitrary target manifolds with arbitrary dimension of the deformation space. The polynomial generators are determined and it is proven that the higher loop amplitudes are polynomials of a certain degree in the generators. Furthermore, the polynomial construction is generalized to solve the extension of the holomorphic anomaly equation to D-branes without deformation space. This method is applied to calculate higher loop amplitudes in numerous examples and the mathematical invariants are extracted. (orig.)

  9. Towards low energy physics from the heterotic string

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, S.N.R.

    2008-06-15

    We investigate orbifold compactifications of the heterotic string, addressing in detail their construction, classification and phenomenological potential. Based on the insight gained from grand unification theories, we develop a successful strategy to search for models resembling the minimal supersymmetric extension of the standard model (MSSM) in Z{sub 6}-II orbifold compactifications. We find about 200 MSSM candidates with the gauge group and the exact spectrum of the MSSM, and supersymmetric vacua below the compactification scale. Among them, there are several models with the following realistic features: R-parity, seesaw suppressed neutrino masses, and intermediate scale of supersymmetry breakdown. (orig.)

  10. On the toroidal compactifications of bosonic strings in higher genus

    International Nuclear Information System (INIS)

    Semikhatov, A.M.

    1989-01-01

    For the bosonic string in a higher genus, compactified on the maximal torus of a simply laced Lie group, we discuss a possibility to construct an operator formalism involving only those operators that are well-defined globally over the whole Riemann surface. We find, in particular, higher genus extensions of (some combinations of) the vertex operators for the Kac-Moody algebra. This allows us to derive the relation between the Sugawara and Virasoro constructions of the energy-momentum tensor on Riemann surfaces, and to propose an operator mechanism underlying the construction of group current correlation functions in higher genus. (orig.)

  11. GPU Based N-Gram String Matching Algorithm with Score Table Approach for String Searching in Many Documents

    Science.gov (United States)

    Srinivasa, K. G.; Shree Devi, B. N.

    2017-10-01

    String searching in documents has become a tedious task with the evolution of Big Data. Generation of large data sets demand for a high performance search algorithm in areas such as text mining, information retrieval and many others. The popularity of GPU's for general purpose computing has been increasing for various applications. Therefore it is of great interest to exploit the thread feature of a GPU to provide a high performance search algorithm. This paper proposes an optimized new approach to N-gram model for string search in a number of lengthy documents and its GPU implementation. The algorithm exploits GPGPUs for searching strings in many documents employing character level N-gram matching with parallel Score Table approach and search using CUDA API. The new approach of Score table used for frequency storage of N-grams in a document, makes the search independent of the document's length and allows faster access to the frequency values, thus decreasing the search complexity. The extensive thread feature in a GPU has been exploited to enable parallel pre-processing of trigrams in a document for Score Table creation and parallel search in huge number of documents, thus speeding up the whole search process even for a large pattern size. Experiments were carried out for many documents of varied length and search strings from the standard Lorem Ipsum text on NVIDIA's GeForce GT 540M GPU with 96 cores. Results prove that the parallel approach for Score Table creation and searching gives a good speed up than the same approach executed serially.

  12. Teaching as an Intervention: Evaluating the AIAI-FTFD Teaching Model and 9 Skills of Communication In an Extension Learning Environment

    Directory of Open Access Journals (Sweden)

    Victor W. Harris

    2016-02-01

    Full Text Available Extension educators are continually seeking ways to make instruction more effective and engaging. This study evaluated the Attention, Interact, Apply, and Invite – Fact, Think, Feel, Do (AIAI-FTFD Start-to-Finish Teaching Model for human service educators in an ongoing Extension educational program to determine the effectiveness of this model in implementing the concept of “teaching as an intervention” in Extension educational programming. Specifically, the study assessed the cognitive, emotional, and intent to change behavioral learning outcomes generated by using the AIAI-FTFD teaching model while completing the 9 Important Communication Skills for Every Relationship (9 Skills program. A self-reported quantitative evaluation design was utilized to assess key objectives in the sample (n = 152. Noticeable and clearly-evident effect sizes were found in perceived knowledge gain and perceived confidence gain in the ability to implement the skills covered in the training. Subsequent discussion focuses on how the AIAI-FTFD Start-to-Finish Teaching Model can facilitate change and learning in educational settings.

  13. Highly excited strings I: Generating function

    Directory of Open Access Journals (Sweden)

    Dimitri P. Skliros

    2017-03-01

    Full Text Available This is the first of a series of detailed papers on string amplitudes with highly excited strings (HES. In the present paper we construct a generating function for string amplitudes with generic HES vertex operators using a fixed-loop momentum formalism. We generalise the proof of the chiral splitting theorem of D'Hoker and Phong to string amplitudes with arbitrary HES vertex operators (with generic KK and winding charges, polarisation tensors and oscillators in general toroidal compactifications E=RD−1,1×TDcr−D (with generic constant Kähler and complex structure target space moduli, background Kaluza–Klein (KK gauge fields and torsion. We adopt a novel approach that does not rely on a “reverse engineering” method to make explicit the loop momenta, thus avoiding a certain ambiguity pointed out in a recent paper by Sen, while also keeping the genus of the worldsheet generic. This approach will also be useful in discussions of quantum gravity and in particular in relation to black holes in string theory, non-locality and breakdown of local effective field theory, as well as in discussions of cosmic superstrings and their phenomenological relevance. We also discuss the manifestation of wave/particle (or rather wave/string duality in string theory.

  14. String Phenomenology: Past, Present and Future Perspectives

    Directory of Open Access Journals (Sweden)

    Alon E. Faraggi

    2014-04-01

    Full Text Available The observation of a scalar resonance at the Large Hadron Collider (LHC, compatible with perturbative electroweak symmetry breaking, reinforces the Standard Model (SM parameterisation of all subatomic data. The logarithmic evolution of the SM gauge and matter parameters suggests that this parameterisation remains viable up to the Planck scale, where gravitational effects are of comparable strength. String theory provides a perturbatively consistent scheme to explore how the parameters of the Standard Model may be determined from a theory of quantum gravity. The free fermionic heterotic string models provide concrete examples of exact string solutions that reproduce the spectrum of the Minimal Supersymmetric Standard Model. Contemporary studies entail the development of methods to classify large classes of models. This led to the discovery of exophobic heterotic-string vacua and the observation of spinor-vector duality, which provides an insight to the global structure of the space of (2,0 heterotic-string vacua. Future directions entail the study of the role of the massive string states in these models and their incorporation in cosmological scenarios. A complementary direction is the formulation of quantum gravity from the principle of manifest phase space duality and the equivalence postulate of quantum mechanics, which suggest that space is compact. The compactness of space, which implies intrinsic regularisation, may be tightly related to the intrinsic finite length scale, implied by string phenomenology.

  15. Document retrieval on repetitive string collections.

    Science.gov (United States)

    Gagie, Travis; Hartikainen, Aleksi; Karhu, Kalle; Kärkkäinen, Juha; Navarro, Gonzalo; Puglisi, Simon J; Sirén, Jouni

    2017-01-01

    Most of the fastest-growing string collections today are repetitive, that is, most of the constituent documents are similar to many others. As these collections keep growing, a key approach to handling them is to exploit their repetitiveness, which can reduce their space usage by orders of magnitude. We study the problem of indexing repetitive string collections in order to perform efficient document retrieval operations on them. Document retrieval problems are routinely solved by search engines on large natural language collections, but the techniques are less developed on generic string collections. The case of repetitive string collections is even less understood, and there are very few existing solutions. We develop two novel ideas, interleaved LCPs and precomputed document lists , that yield highly compressed indexes solving the problem of document listing (find all the documents where a string appears), top- k document retrieval (find the k documents where a string appears most often), and document counting (count the number of documents where a string appears). We also show that a classical data structure supporting the latter query becomes highly compressible on repetitive data. Finally, we show how the tools we developed can be combined to solve ranked conjunctive and disjunctive multi-term queries under the simple [Formula: see text] model of relevance. We thoroughly evaluate the resulting techniques in various real-life repetitiveness scenarios, and recommend the best choices for each case.

  16. Worldsheet factorization for twistor-strings

    International Nuclear Information System (INIS)

    Adamo, Tim

    2014-01-01

    We study the multiparticle factorization properties of two worldsheet theories which — at tree-level — describe the scattering of massless particles in four dimensions: the Berkovits-Witten twistor-string for N=4 super-Yang-Mills coupled to N=4 conformal supergravity, and the Skinner twistor-string for N=8 supergravity. By considering these string-like theories, we can study factorization at the level of the worldsheet before any Wick contractions or integrals have been performed; this is much simpler than considering the factorization properties of the amplitudes themselves. In Skinner’s twistor-string this entails the addition of worldsheet gravity as well as a formalism that represents all external states in a manifestly symmetric way, which we develop explicitly at genus zero. We confirm that the scattering amplitudes of Skinner’s theory, as well as the gauge theory amplitudes for the planar sector of the Berkovits-Witten theory, factorize appropriately at genus zero. In the non-planar sector, we find behavior indicative of conformal gravity in the Berkovits-Witten twistor-string. We contrast factorization in twistor-strings with the story in ordinary string theory, and also make some remarks on higher genus factorization and disconnected prescriptions

  17. Worldsheet factorization for twistor-strings

    Energy Technology Data Exchange (ETDEWEB)

    Adamo, Tim [Department of Applied Mathematics & Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

    2014-04-10

    We study the multiparticle factorization properties of two worldsheet theories which — at tree-level — describe the scattering of massless particles in four dimensions: the Berkovits-Witten twistor-string for N=4 super-Yang-Mills coupled to N=4 conformal supergravity, and the Skinner twistor-string for N=8 supergravity. By considering these string-like theories, we can study factorization at the level of the worldsheet before any Wick contractions or integrals have been performed; this is much simpler than considering the factorization properties of the amplitudes themselves. In Skinner’s twistor-string this entails the addition of worldsheet gravity as well as a formalism that represents all external states in a manifestly symmetric way, which we develop explicitly at genus zero. We confirm that the scattering amplitudes of Skinner’s theory, as well as the gauge theory amplitudes for the planar sector of the Berkovits-Witten theory, factorize appropriately at genus zero. In the non-planar sector, we find behavior indicative of conformal gravity in the Berkovits-Witten twistor-string. We contrast factorization in twistor-strings with the story in ordinary string theory, and also make some remarks on higher genus factorization and disconnected prescriptions.

  18. Using the MoodleReader as an Extensive Reading Tool and Its Effect on Iranian EFL Students' Incidental Vocabulary Learning

    Science.gov (United States)

    Alavi, Sepideh; Keyvanshekouh, Afsaneh

    2012-01-01

    The present study focused on using the MoodleReader to promote extensive reading (ER) in an Iranian EFL context, emphasizing its effect on students' incidental vocabulary acquisition. Thirty eight Shiraz University sophomores were assigned to experimental and control groups. The experimental group used the MoodleReader for their ER program, while…

  19. Improving Healthy Living Youth Development Program Outreach in Extension: Lessons Learned from the 4-H Health Rocks! Program

    Science.gov (United States)

    Kumaran, Muthusami; Fogarty, Kate; Fung, Whitney M.; Terminello, Amanda

    2015-01-01

    This article discusses a qualitative evaluation of the Florida 4-H Health Rocks! program aimed at youth alcohol, tobacco, and other drug use prevention. A questionnaire was distributed to Extension professionals across Florida to gain insight into the strengths and barriers they faced with programming. Programmatic strengths included targeting a…

  20. String-Corrected Black Holes

    Energy Technology Data Exchange (ETDEWEB)

    Hubeny, V.

    2005-01-12

    We investigate the geometry of four dimensional black hole solutions in the presence of stringy higher curvature corrections to the low energy effective action. For certain supersymmetric two charge black holes these corrections drastically alter the causal structure of the solution, converting seemingly pathological null singularities into timelike singularities hidden behind a finite area horizon. We establish, analytically and numerically, that the string-corrected two-charge black hole metric has the same Penrose diagram as the extremal four-charge black hole. The higher derivative terms lead to another dramatic effect--the gravitational force exerted by a black hole on an inertial observer is no longer purely attractive. The magnitude of this effect is related to the size of the compactification manifold.

  1. The birth of string theory

    CERN Document Server

    Castellani, Elena; Colomo, Filippo; Di Vecchia, Paolo

    2012-01-01

    String theory is currently the best candidate for a unified theory of all forces and all forms of matter in nature. As such, it has become a focal point for physical and philosophical discussions. This unique book explores the history of the theory's early stages of development, as told by its main protagonists. The book journeys from the first version of the theory (the so-called dual resonance model) in the late sixties, as an attempt to describe the physics of strong interactions outside the framework of quantum field theory, to its reinterpretation around the mid-seventies as a quantum theory of gravity unified with the other forces, and its successive developments up to the superstring revolution in 1984. Providing important background information to current debates on the theory, this book is essential reading for students and researchers in physics, as well as historians and philosophers of science.

  2. Graviton spectra in string cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Galluccio, Massimo [Osservatorio Astronomico di Roma (Roma-IT); Litterio, Marco [Istituto Astronomico dell' Universita (Roma-IT); Occhionero, Franco [Osservatorio Astronomico di Roma (Roma-IT)

    1996-08-01

    We propose to uncover the signature of a stringy era in the primordial Universe by searching for a prominent peak in the relic graviton spectrum. This feature, which in our specific model terminates an ω³ increase and initiates an ω⁻⁷ decrease, is induced during the so far overlooked bounce of the scale factor between the collapsing deflationary era (or pre-Big Bang) and the expanding inflationary era (or post-Big Bang). We evaluate both analytically and numerically the frequency and the intensity of the peak and we show that they may likely fall in the realm of the new generation of interferometric detectors. The existence of a peak is at variance with ordinarily monotonic (either increasing or decreasing) graviton spectra of canonical cosmologies; its detection would therefore offer strong support to string cosmology.

  3. Optimal shapes of compact strings

    International Nuclear Information System (INIS)

    Maritan, A.; Micheletti, C.; Trovato, A.; Banavar, J.R.

    2000-07-01

    Optimal geometrical arrangements, such as the stacking of atoms, are of relevance in diverse disciplines. A classic problem is the determination of the optimal arrangement of spheres in three dimensions in order to achieve the highest packing fraction; only recently has it been proved that the answer for infinite systems is a face-centred-cubic lattice. This simply stated problem has had a profound impact in many areas, ranging from the crystallization and melting of atomic systems, to optimal packing of objects and subdivision of space. Here we study an analogous problem-that of determining the optimal shapes of closely packed compact strings. This problem is a mathematical idealization of situations commonly encountered in biology, chemistry and physics, involving the optimal structure of folded polymeric chains. We find that, in cases where boundary effects are not dominant, helices with a particular pitch-radius ratio are selected. Interestingly, the same geometry is observed in helices in naturally-occurring proteins. (author)

  4. Whiteheadian Actual Entitities and String Theory

    Science.gov (United States)

    Bracken, Joseph A.

    2012-06-01

    In the philosophy of Alfred North Whitehead, the ultimate units of reality are actual entities, momentary self-constituting subjects of experience which are too small to be sensibly perceived. Their combination into "societies" with a "common element of form" produces the organisms and inanimate things of ordinary sense experience. According to the proponents of string theory, tiny vibrating strings are the ultimate constituents of physical reality which in harmonious combination yield perceptible entities at the macroscopic level of physical reality. Given that the number of Whiteheadian actual entities and of individual strings within string theory are beyond reckoning at any given moment, could they be two ways to describe the same non-verifiable foundational reality? For example, if one could establish that the "superject" or objective pattern of self- constitution of an actual entity vibrates at a specific frequency, its affinity with the individual strings of string theory would be striking. Likewise, if one were to claim that the size and complexity of Whiteheadian 'societies" require different space-time parameters for the dynamic interrelationship of constituent actual entities, would that at least partially account for the assumption of 10 or even 26 instead of just 3 dimensions within string theory? The overall conclusion of this article is that, if a suitably revised understanding of Whiteheadian metaphysics were seen as compatible with the philosophical implications of string theory, their combination into a single world view would strengthen the plausibility of both schemes taken separately. Key words: actual entities, subject/superjects, vibrating strings, structured fields of activity, multi-dimensional physical reality.

  5. Planckian axions in string theory

    International Nuclear Information System (INIS)

    Bachlechner, Thomas C.; Long, Cody; McAllister, Liam

    2015-01-01

    We argue that super-Planckian diameters of axion fundamental domains can arise in Calabi-Yau compactifications of string theory. In a theory with N axions θ i , the fundamental domain is a polytope defined by the periodicities of the axions, via constraints of the form −π√N. This result is robust in the presence of P>N constraints, while for P=N the diameter is further enhanced by eigenvector delocalization to N 3/2 f N . We directly verify our results in explicit Calabi-Yau compactifications of type IIB string theory. In the classic example with h 1,1 =51 where parametrically controlled moduli stabilization was demonstrated by Denef et al. in http://dx.doi.org/10.4310/ATMP.2005.v9.n6.a1, the largest metric eigenvalue obeys f N ≈0.013M pl . The random matrix analysis then predicts, and we exhibit, axion diameters ≈M pl for the precise vacuum parameters found in http://dx.doi.org/10.4310/ATMP.2005.v9.n6.a1. Our results provide a framework for pursuing large-field axion inflation in well-understood flux vacua.

  6. Protein Analysis Meets Visual Word Recognition: A Case for String Kernels in the Brain

    Science.gov (United States)

    Hannagan, Thomas; Grainger, Jonathan

    2012-01-01

    It has been recently argued that some machine learning techniques known as Kernel methods could be relevant for capturing cognitive and neural mechanisms (Jakel, Scholkopf, & Wichmann, 2009). We point out that "String kernels," initially designed for protein function prediction and spam detection, are virtually identical to one contending proposal…

  7. String gravity and cosmology some new ideas

    CERN Document Server

    Kiritsis, Elias; Kiritsis, Elias; Kounnas, Costas

    1997-01-01

    String theory provides the only consistent framework so far that unifies all interactions including gravity. We discuss gravity and cosmology in string theory. Conventional notions from general relativity like geometry, topology etc. are well defined only as low energy approximations in string theory. At small distances physics deviates from the field theoretic intuition. We present several examples of purely stringy phenomena which imply that the physics at strong curvatures can be quite different from what one might expect from field theory. They indicate new possibilities in the context of quantum cosmology.

  8. Systems and methods for photovoltaic string protection

    Energy Technology Data Exchange (ETDEWEB)

    Krein, Philip T.; Kim, Katherine A.; Pilawa-Podgurski, Robert C. N.

    2017-10-25

    A system and method includes a circuit for protecting a photovoltaic string. A bypass switch connects in parallel to the photovoltaic string and a hot spot protection switch connects in series with the photovoltaic string. A first control signal controls opening and closing of the bypass switch and a second control signal controls opening and closing of the hot spot protection switch. Upon detection of a hot spot condition the first control signal closes the bypass switch and after the bypass switch is closed the second control signal opens the hot spot protection switch.

  9. Quantum consistency of open string theories

    International Nuclear Information System (INIS)

    Govaerts, J.

    1989-01-01

    We discuss how Virasoro anomalies in open string theories uniquely select the gauge group SO(2 D/2 ) independently of any regularisation, although the cancellation of these anomalies does not occur in tachyonic theories, and regulators can always be chosen to make these theories (one-loop) finite for any SO(n) and USp(n) gauge group. The discussion is mainly restricted to open bosonic strings. These results open new perspectives for the recent suggestion made by Sagnotti, the generalisations of which allow for the construction of new open string theories in less than ten dimensions. (orig.)

  10. Open string decoupling and tachyon condensation

    International Nuclear Information System (INIS)

    Chalmers, G.

    2001-01-01

    The amplitudes in perturbative open string theory are examined as functions of the tachyon condensate parameter. The boundary state formalism demonstrates the decoupling of the open string modes at the non-perturbative minima of the tachyon potential via a degeneration of open world-sheets and identifies an independence of the coupling constants g s and g YM at general values of the tachyon condensate. The closed sector is generated at the quantum level; it is also generated at the classical level through the condensation of the propagating open string modes on the D-brane degrees of freedom.

  11. The String and the Cosmic Bounce

    Directory of Open Access Journals (Sweden)

    Bozza V.

    2014-04-01

    Full Text Available String theory introduces a new fundamental scale (the string length that is expected to regularize the singularities of classical general relativity. In a cosmological context, the Big Bang is no longer regarded as the beginning of time, but just a transition between a Pre-Big Bang collapse phase and the current expansion. We will review old and recent attempts to build consistent bouncing cosmologies inspired to string theories, discussing their solved and unsolved problems, focussing on the observables that may distinguish them from standard inflationary scenarios.

  12. A hybrid metaheuristic for closest string problem.

    Science.gov (United States)

    Mousavi, Sayyed Rasoul

    2011-01-01

    The Closest String Problem (CSP) is an optimisation problem, which is to obtain a string with the minimum distance from a number of given strings. In this paper, a new metaheuristic algorithm is investigated for the problem, whose main feature is relatively high speed in obtaining good solutions, which is essential when the input size is large. The proposed algorithm is compared with four recent algorithms suggested for the problem, outperforming them in more than 98% of the cases. It is also remarkably faster than all of them, running within 1 s in most of the experimental cases.

  13. Big bang models in string theory

    Energy Technology Data Exchange (ETDEWEB)

    Craps, Ben [Theoretische Natuurkunde, Vrije Universiteit Brussel and The International Solvay Institutes Pleinlaan 2, B-1050 Brussels (Belgium)

    2006-11-07

    These proceedings are based on lectures delivered at the 'RTN Winter School on Strings, Supergravity and Gauge Theories', CERN, 16-20 January 2006. The school was mainly aimed at PhD students and young postdocs. The lectures start with a brief introduction to spacetime singularities and the string theory resolution of certain static singularities. Then they discuss attempts to resolve cosmological singularities in string theory, mainly focusing on two specific examples: the Milne orbifold and the matrix big bang.

  14. String Analysis as an Abstract Interpretation

    Science.gov (United States)

    Kim, Se-Won; Choe, Kwang-Moo

    We formalize a string analysis within abstract interpretation framework. The abstraction of strings is given as a conjunction of predicates that describes the common configuration changes on the reference pushdown automaton while processing the strings. We also present a family of pushdown automata called ɛ bounded pushdown automata. This family covers all context-free languages, and by using this family of pushdown automata, we can prevent abstract values from becoming infinite conjunctions and guarantee that the operations required in the analyzer are computable.

  15. Affinity Strings: Enterprise Data for Resource Recommendations

    Directory of Open Access Journals (Sweden)

    Shane Nackerud

    2008-12-01

    Full Text Available The University of Minnesota Libraries have created a MyLibrary portal, with databases and e-journals targeted to users, based on their affiliations. The University's enterprise authentication system provides an "affinity string", now used to personalize the MyLibrary portal. This affinity string automates discovery of a user's relationship to the University--describing a user's academic department and degree program or position at the University. Affinity strings also provide the Libraries with an anonymized view of resource usage, allowing data collection that respects users' privacy and lays the groundwork for automated recommendation of relevant resources based on the practices and habits of their peers.

  16. A gluing operator for the ambitwistor string

    Science.gov (United States)

    Roehrig, Kai A.; Skinner, David

    2018-01-01

    We present a new operator in the ambitwistor string which glues together correlators with fewer points or of lower genus. It underpins the recursive construction of tree-level CHY scattering amplitudes by Dolan & Goddard, as well as the computation of loop integrands on a Riemann sphere by Geyer et al. The gluing operator is a tractable object due to the finiteness of the spectrum. In particular, we demonstrate how it gives rise to the complete one-loop integrand in SYM and SUGRA. The operator is conjectured to be the path integral incarnation of the ambitwistor string propagator, and to coincide with the field theory limit of the standard string theory propagator.

  17. Observation of Motion of Bowed Strings and Resonant Strings in Violin Performances

    Science.gov (United States)

    Matsutani, Akihiro

    2013-10-01

    The motion of a bowed string and a resonant string of a violin were simultaneously observed for the first time. The results of the direct observation of string motion in double stops and harmonics are also presented. The importance of the resonance was experimentally demonstrated from these observations. It is suggested that players should take account of the resonance and ideal Helmholtz motion in violin performances.

  18. Implementation of Karp-Rabin string matching algorithm in reconfigurable hardware for network intrusion prevention system

    Science.gov (United States)

    Botwicz, Jakub; Buciak, Piotr; Sapiecha, Piotr

    2006-03-01

    Intrusion Prevention Systems (IPSs) have become widely recognized as a powerful tool and an important element of IT security safeguards. The essential feature of network IPSs is searching through network packets and matching multiple strings, that are fingerprints of known attacks. String matching is highly resource consuming and also the most significant bottleneck of IPSs. In this article an extension of the classical Karp-Rabin algorithm and its implementation architectures were examined. The result is a software, which generates a source code of a string matching module in hardware description language, that could be easily used to create an Intrusion Prevention System implemented in reconfigurable hardware. The prepared module matches the complete set of Snort IPS signatures achieving throughput of over 2 Gbps on an Altera Stratix I1 evaluation board. The most significant advantage of the proposed architecture is that the update of the patterns database does not require reconfiguration of the circuitry.

  19. Spinning strings in AdS3×S3 with NS–NS flux

    Directory of Open Access Journals (Sweden)

    Rafael Hernández

    2014-11-01

    Full Text Available The sigma model describing closed strings rotating in AdS3×S3 is known to reduce to the one-dimensional Neumann–Rosochatius integrable system. In this article we show that closed spinning strings in AdS3×S3×T4 in the presence of NS–NS three-form flux can be described by an extension of the Neumann–Rosochatius system. We consider closed strings rotating with one spin in AdS3 and two different angular momenta in S3. For a class of solutions with constant radii we find the dependence of the classical energy on the spin and the angular momenta as an expansion in the square of the 't Hooft coupling of the theory.

  20. No extensive experience in open procedures is needed to learn lobectomy by video-assisted thoracic surgery

    DEFF Research Database (Denmark)

    Konge, Lars; Petersen, René Horsleben; Hansen, Henrik Jessen

    2012-01-01

    Lobectomies done by video-assisted thoracic surgery (VATS) result in fewer complications and less pain and save total costs compared with the traditional approach. However, the majority of procedures are still performed via open thoracotomies, because VATS lobectomy is considered difficult to learn...

  1. Predicting User Acceptance of Collaborative Technologies: An Extension of the Technology Acceptance Model for E-Learning

    Science.gov (United States)

    Cheung, Ronnie; Vogel, Doug

    2013-01-01

    Collaborative technologies support group work in project-based environments. In this study, we enhance the technology acceptance model to explain the factors that influence the acceptance of Google Applications for collaborative learning. The enhanced model was empirically evaluated using survey data collected from 136 students enrolled in a…

  2. Advances in String Theory in Curved Backgrounds: A Synthesis Report

    OpenAIRE

    Sanchez, Norma G.

    2003-01-01

    A synthetic report of the advances in the study of classical and quantum string dynamics in curved backgrounds is provided, namely: the new feature of multistring solutions; the effect of a cosmological constant and of spacial curvature on classical and quantum strings; classical splitting of fundamental strings;the general string evolution in constant curvature spacetimes;the conformal invariant effects;strings on plane waves, shock waves and spacetime singularities and its spectrum. New dev...

  3. Multi-branes boundary states with open string interactions

    International Nuclear Information System (INIS)

    Pesando, Igor

    2008-01-01

    We derive boundary states which describe configurations of multiple parallel branes with arbitrary open string states interactions in bosonic string theory. This is obtained by a careful discussion of the factorization of open/closed string states amplitudes taking care of cycles needed by ensuring vertices commutativity: in particular the discussion reveals that already at the tree level open string knows of the existence of closed string

  4. Hagedorn Behavior of Little String Theories from string corrections to NS5-branes

    DEFF Research Database (Denmark)

    Harmark, Troels; Obers, N. A.

    2000-01-01

    We examine the Hagedorn behavior of little string theory using its conjectured duality with near-horizon NS5-branes. In particular, by studying the string-corrected NS5-brane supergravity solution, it is shown that tree-level corrections to the temperature vanish, while the leading one-loop string...... correction generates the correct temperature dependence of the entropy near the Hagedorn temperature. Finally, the Hagedorn behavior of ODp-brane theories, which are deformed versions of little string theory, is considered via their supergravity duals....

  5. Closed string fields as parameters of extra gauge symmetry of open string field theory

    International Nuclear Information System (INIS)

    Aref'eva, I. Ya.; Chekhov, L.O.

    1987-05-01

    A gauge invariant action for mixed system of closed and open bosonic strings is considered. We notice that in the open string sector a gauge group parametrized by closed string states does act. In the description of mixed system the open-to-closed transition operator plays a crucial role. We show that this transition operator is an intertwining operator between BRST charges for closed and open string. The closed-open-open analogue of Caneschi-Schwimmer-Veneziano amplitude is presented and the triple application of the transition operator to all the tree legs of the open CVS vertex is also discussed. (author). 20 refs, 3 figs

  6. Quark mass correction to the string potential

    International Nuclear Information System (INIS)

    Lambiase, G.; Nesterenko, V.V.

    1995-01-01

    A consistent method for calculating the interquark potential generated by the relativistic string with massive ends is proposed. In this approach the interquark potential in the model of the Nambu-Goto string with point-like masses at its ends is calculated. At first the calculation is done in the one-loop approximation and then the variational estimation is performed. The quark mass correction results in decreasing the critical distance (deconfinement radius). When quark mass decreases the critical distance also decreases. For obtaining a finite result under summation over eigenfrequencies of the Nambu-Goto string with massive ends a suitable mode-by-mode subtraction is proposed. This renormalization procedure proves to be completely unique. In the framework of the developed approach the one-loop interquark potential in the model of the relativistic string with rigidity is also calculated. 34 refs., 2 figs

  7. Renormalizability of Open Bosonic Thermal Strings

    OpenAIRE

    Haruo, FUJISAKI; Koichi, NAKAGAWA; Department of Physics, Rikkyo University; Department of Physics, Rikkyo University

    1989-01-01

    The thermal stability of renormalization of open bosonic strings is exemplified through the Neveu-Scherk regularization of the planar tachyon self-energy within the framework of the thermofield dynamics.

  8. Gauge/string duality and hadronic physics

    OpenAIRE

    Boschi-Filho, Henrique; Braga, Nelson R. F.

    2006-01-01

    We review some recent results on phenomenological approaches to strong interactions inspired in gauge/string duality. In particular, we discuss how such models lead to very good estimates for hadronic masses.

  9. Introduction to string and superstring theory II

    International Nuclear Information System (INIS)

    Peskin, M.E.

    1987-03-01

    Conformal field theory is reviewed, then conformal invariance is used to rederive the basic results on the embedding dimensionality for bosonic and fermionic strings. The spectrum of the bosonic and the computation of scattering amplitudes are discussed. The formalism used is extended to clarify the origin of Yang-Mills gauge invariance in the open bosonic string theory. The question of the general-coordinate gauge invariance of string theory is addressed, presenting two disparate viewpoints on this question. A brief introduction is then given of the reduction from the idealized string theory in 10 extended dimensions to more realistic solutions in which all but 4 of these dimensions are compactified. The state of knowledge about the space-time supersymmetry of the superstring from the covariant viewpoint is outlined. An approach for identifying possible 6-dimensional spaces which might represent the form of the compact dimensions is discussed, and the orbifold scheme of compactification is presented. 77 refs., 18 figs

  10. Instantons, hypermultiplets and the heterotic string

    International Nuclear Information System (INIS)

    Halmagyi, Nick; Melnikov, Ilarion V.; Sethi, Savdeep

    2007-01-01

    Hypermultiplet couplings in type IIA string theory on a Calabi-Yau space can be quantum corrected by D2-brane instantons wrapping special Lagrangian cycles. On the other hand, hypermultiplet couplings in the heterotic string on a K3 surface are corrected by world-sheet instantons wrapping curves. In a class of examples, we relate these two sets of instanton corrections. We first present an analogue of the c-map for the heterotic string via a dual flux compactification of M-theory. Using this duality, we propose two ways of capturing quantum corrections to hypermultiplets. We then use the orientifold limit of certain F-theory compactifications to relate curves in K3 to special Lagrangians in dual type IIA compactifications. We conclude with some results from perturbative string theory for hypermultiplet F-terms and a conjecture about the topology of brane instantons

  11. Pinching parameters for open (super) strings

    Science.gov (United States)

    Playle, Sam; Sciuto, Stefano

    2018-02-01

    We present an approach to the parametrization of (super) Schottky space obtained by sewing together three-punctured discs with strips. Different cubic ribbon graphs classify distinct sets of pinching parameters; we show how they are mapped onto each other. The parametrization is particularly well-suited to describing the region within (super) moduli space where open bosonic or Neveu-Schwarz string propagators become very long and thin, which dominates the IR behaviour of string theories. We show how worldsheet objects such as the Green's function converge to graph theoretic objects such as the Symanzik polynomials in the α ' → 0 limit, allowing us to see how string theory reproduces the sum over Feynman graphs. The (super) string measure takes on a simple and elegant form when expressed in terms of these parameters.

  12. Casimir energy for a piecewise uniform string

    International Nuclear Information System (INIS)

    Brevik, I.; Nielsen, H.B.

    1989-07-01

    The Casimir energy for the transverse oscillations of a piecewise uniform closed string is calculated. The string consists of two parts I and II, endowed in general with different tensions and mass densities, although adjusted in such a way that the velocity of sound always equals the velocity of light. The dispersion equation is worked out under general conditions, and the frequency spectrum is determined in special cases. When the ratio L II /L I between the string lengths is an integer, it is in principle possible to determine the frequency spectrum through solving algebraic equations of increasingly high degree. The Casimir energy relative to the uniform string is in general found to be negative, although in the special case L I =L II the energy is equal to zero. Delicate points in the regularization procedure are discussed; they point toward an anomaly in the theory. (orig.)

  13. Matrix Models and String World Sheet Duality

    OpenAIRE

    de Alwis, S. P.

    1997-01-01

    The scaling limit used recently to derive matrix models, and a certain analyticity assumption, are invoked to argue that the agreement between some matrix model calculations and supergravity is a consequence of string world sheet duality.

  14. The dual faces of string theory

    CERN Document Server

    Kiritsis, Elias

    1993-01-01

    Duality symmetries for strings moving in non-trivial spacetime backgrounds are analysed. It is shown that, for backgrounds generated from compact WZW and coset models, such duality symmetries are exact to all orders in string perturbation theory. A global treatment of duality symmetries is given, by associating them to the known symmetries of affine current algebras (affine-Weyl group and external automorphisms). It is argued that self-duality symmetries of WZW and coset models generate the duality symmetries of their moduli space. Some remarks are presented, concerning the survival of such symmetries in the non-compact case. The implications of duality symmetries for string dynamics in non-trivial/singular spacetimes are discussed. (Talk given at the "Strings 93" Conference at Berkeley, May 1993)

  15. Witten Genus and String Complete Intersections

    OpenAIRE

    Chen, Qingtao; Han, Fei

    2006-01-01

    In this note, we prove that the Witten genus of nonsingular string complete intersections in product of complex projective spaces vanishes. Our result generalizes a known result of Landweber and Stong (cf. [HBJ]).

  16. Academic Training: String Theory for Pedestrians

    CERN Multimedia

    2007-01-01

    2006-2007 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 29, 30, 31 January 2007, from 11:00 to 12:00 Main Auditorium, bldg. 500 on 29 and 30 January, TH Auditorium, Bldg 4, 3-006, on 31 January String Theory for Pedestrians B. ZWIEBACH, MIT, Cambridge, USA In this 3-lecture series I will discuss the basics of string theory, some physical applications, and the outlook for the future. I will begin with the main concepts of the classical theory and the application to the study of cosmic superstrings. Then I will turn to the quantum theory and discuss applications to the investigation of hadronic spectra and the recently discovered quark-gluon plasma. I will conclude with a sketch of string models of particle physics and showing some avenues that may lead to a complete formulation of string theory.

  17. Introduction to string and superstring theory II

    Energy Technology Data Exchange (ETDEWEB)

    Peskin, M.E.

    1987-03-01

    Conformal field theory is reviewed, then conformal invariance is used to rederive the basic results on the embedding dimensionality for bosonic and fermionic strings. The spectrum of the bosonic and the computation of scattering amplitudes are discussed. The formalism used is extended to clarify the origin of Yang-Mills gauge invariance in the open bosonic string theory. The question of the general-coordinate gauge invariance of string theory is addressed, presenting two disparate viewpoints on this question. A brief introduction is then given of the reduction from the idealized string theory in 10 extended dimensions to more realistic solutions in which all but 4 of these dimensions are compactified. The state of knowledge about the space-time supersymmetry of the superstring from the covariant viewpoint is outlined. An approach for identifying possible 6-dimensional spaces which might represent the form of the compact dimensions is discussed, and the orbifold scheme of compactification is presented. 77 refs., 18 figs. (LEW)

  18. Effective string theory and QCD scattering amplitudes

    International Nuclear Information System (INIS)

    Makeenko, Yuri

    2011-01-01

    QCD string is formed at distances larger than the confinement scale and can be described by the Polchinski-Strominger effective string theory with a nonpolynomial action, which has nevertheless a well-defined semiclassical expansion around a long-string ground state. We utilize modern ideas about the Wilson-loop/scattering-amplitude duality to calculate scattering amplitudes and show that the expansion parameter in the effective string theory is small in the Regge kinematical regime. For the amplitudes we obtain the Regge behavior with a linear trajectory of the intercept (d-2)/24 in d dimensions, which is computed semiclassically as a momentum-space Luescher term, and discuss an application to meson scattering amplitudes in QCD.

  19. The approximability of the String Barcoding problem

    Directory of Open Access Journals (Sweden)

    Rizzi Romeo

    2006-08-01

    Full Text Available Abstract The String Barcoding (SBC problem, introduced by Rash and Gusfield (RECOMB, 2002, consists in finding a minimum set of substrings that can be used to distinguish between all members of a set of given strings. In a computational biology context, the given strings represent a set of known viruses, while the substrings can be used as probes for an hybridization experiment via microarray. Eventually, one aims at the classification of new strings (unknown viruses through the result of the hybridization experiment. In this paper we show that SBC is as hard to approximate as Set Cover. Furthermore, we show that the constrained version of SBC (with probes of bounded length is also hard to approximate. These negative results are tight.

  20. σ-models and string theories

    International Nuclear Information System (INIS)

    Randjbar-Daemi, S.

    1987-01-01

    The propagation of closed bosonic strings interacting with background gravitational and dilaton fields is reviewed. The string is treated as a quantum field theory on a compact 2-dimensional manifold. The question is posed as to how the conditions for the vanishing trace anomaly and the ensuing background field equations may depend on global features of the manifold. It is shown that to the leading order in σ-model perturbation theory the string loop effects do not modify the gravitational and the dilaton field equations. However for the purely bosonic strings new terms involving the modular parameter of the world sheet are induced by quantum effects which can be absorbed into a re-definition of the background fields. The authors also discuss some aspects of several regularization schemes such as dimensional, Pauli-Villars and the proper-time cut off in an appendix

  1. ABCD of Beta Ensembles and Topological Strings

    CERN Document Server

    Krefl, Daniel

    2012-01-01

    We study beta-ensembles with Bn, Cn, and Dn eigenvalue measure and their relation with refined topological strings. Our results generalize the familiar connections between local topological strings and matrix models leading to An measure, and illustrate that all those classical eigenvalue ensembles, and their topological string counterparts, are related one to another via various deformations and specializations, quantum shifts and discrete quotients. We review the solution of the Gaussian models via Macdonald identities, and interpret them as conifold theories. The interpolation between the various models is plainly apparent in this case. For general polynomial potential, we calculate the partition function in the multi-cut phase in a perturbative fashion, beyond tree-level in the large-N limit. The relation to refined topological string orientifolds on the corresponding local geometry is discussed along the way.

  2. A note on probabilistic models over strings: the linear algebra approach.

    Science.gov (United States)

    Bouchard-Côté, Alexandre

    2013-12-01

    Probabilistic models over strings have played a key role in developing methods that take into consideration indels as phylogenetically informative events. There is an extensive literature on using automata and transducers on phylogenies to do inference on these probabilistic models, in which an important theoretical question is the complexity of computing the normalization of a class of string-valued graphical models. This question has been investigated using tools from combinatorics, dynamic programming, and graph theory, and has practical applications in Bayesian phylogenetics. In this work, we revisit this theoretical question from a different point of view, based on linear algebra. The main contribution is a set of results based on this linear algebra view that facilitate the analysis and design of inference algorithms on string-valued graphical models. As an illustration, we use this method to give a new elementary proof of a known result on the complexity of inference on the "TKF91" model, a well-known probabilistic model over strings. Compared to previous work, our proving method is easier to extend to other models, since it relies on a novel weak condition, triangular transducers, which is easy to establish in practice. The linear algebra view provides a concise way of describing transducer algorithms and their compositions, opens the possibility of transferring fast linear algebra libraries (for example, based on GPUs), as well as low rank matrix approximation methods, to string-valued inference problems.

  3. String field theory in curved space

    International Nuclear Information System (INIS)

    Kikkawa, Keiji; Maeno, Masahiro; Sawada, Shiro

    1988-01-01

    The purely cubic action in the string field theory is shown to provide a set of equations of motion for background fields which agree to those obtained by the vanishing condition of β-functions in the non-linear sigma model. Using the sigma model as an auxiliary tool, a systematic method for solving the string field theory in curved space is proposed. (author)

  4. Hard scattering and gauge/string duality.

    Science.gov (United States)

    Polchinski, Joseph; Strassler, Matthew J

    2002-01-21

    We consider high-energy fixed-angle scattering of glueballs in confining gauge theories that have supergravity duals. Although the effective description is in terms of the scattering of strings, we find that the amplitudes are hard (power law). This is a consequence of the warped geometry of the dual theory, which has the effect that in an inertial frame the string process is never in the soft regime. At small angle we find hard and Regge behaviors in different kinematic regions.

  5. String Stretching, Frequency Modulation, and Banjo Clang

    OpenAIRE

    Politzer, David

    2014-01-01

    The banjo’s floating bridge, string break angle, and flexible drumhead all contribute to substantial audio range frequency modulation. From the world of electronic music synthesis, it is known that modulating higher frequency sounds with lower acoustic frequencies leads to metallic and bell-like tone. The mechanics of the banjo does just that quite naturally, modulating fundamentals and harmonics with the motion of the bridge. In technical terms, with a floating bridge, string stretching is f...

  6. Electron string phenomenon: physics and use

    Science.gov (United States)

    Donets, Evgeny D.

    2004-01-01

    Electron string phenomenon arises as a result of phase transition of a state of multiply reflected electron beam to this new discovered state of one component electron plasma and can be easily observed in the reflex mode of EBIS operation. The transition goes via a strong instability, which causes considerable electron energy spread, which in its turn suppresses the instability. Electron string state is a stationary state of hot pure electron plasma, which is heated by injected electron beam and cooled because of electron loses. Electron string is quiet in broad regions of experimental parameters, so that it is used for confinement and ionization of positive ions by electron impact to highly charge states similar to electron beams in EBIS. Application of electron strings instead of electron beams for ion production allows to save about 99% of electric power of electron beam and simultaneously to improve reliability of an ion source considerably. The JINR EBIS `Krion-2' in the string mode of operation is used for production of N7+, Ar16+ and Fe24+ ion beams and their acceleration to relativistic energies on the facility of the JINR super conducting one turn injection synchrotron `Nuklotron'. The tubular electron string possibly can exist and it is under study now theoretically and experiments are prepared now. Estimations show that a Tubular Electron String Ion Source (TESIS) could have up to three orders of magnitude higher ion output then a Linear one (LESIS). In frames of nuclear astrophysics electron strings can be used for research of fusion nuclear reactions at low energies in conditions when both beam and target nuclei do not carry orbital electrons. The project NARITA — Nuclear Astrophysics Researches in an Ion Trap Apparatus is proposed. Polarization effects also can be studied.

  7. String field theory in the Siegel gauge

    International Nuclear Information System (INIS)

    Bochicchio, M.

    1987-01-01

    We specialize the gauge-fixing procedure for the Witten action of the open bosonic string, given in a preceding paper, choosing the Siegel gauge. We find that the BRST-invariant gauge-fixed action is the gauge invariant one with ghost number unrestricted plus a gauge-fixing term. The BRST invariance of the measure in the functional integral is briefly discussed. As a technical tool the Hodge dual of a string functional is defined. (orig.)

  8. Strings, Fivebranes and an Expanding Universe

    OpenAIRE

    Khuri, Ramzi R.; Pokotilov, Andriy

    2002-01-01

    It was recently shown that velocity-dependent forces between parallel fundamental strings moving apart in a $D-$dimensional spacetime implied an accelerating expanding universe in $D-1$-dimensional space-time. Exact solutions were obtained for the early time expansion in $D=5,6$. Here we show that this result also holds for fundamental strings in the background of a fivebrane, and argue that the feature of an accelerating universe would hold for more general $p$-brane-seeded models.

  9. Towards natural inflation in string theory

    International Nuclear Information System (INIS)

    Ben-Dayan, Ido; Pedro, Francisco G.; Westphal, Alexander

    2014-07-01

    We provide type IIB string embeddings of two axion variants of natural inflation. We use a combination of RR 2 form axions as the inflaton field and have its potential generated by non perturbative effects in the superpotential. Besides giving rise to inflation, the models developed take into account the stabilization of the compact space, both in the KKLT and large volume scenario regimes, an essential condition for any semi-realistic model of string inflation.

  10. Some properties of a Δ-string

    International Nuclear Information System (INIS)

    Dzhunushaliev, V

    2003-01-01

    The properties of 5D gravitational flux tubes are considered. With the cross section and fifth dimension in the Planck region, such tubes can be considered as stringlike objects, namely Δ-strings. A model of attachment of Δ-string to a spacetime is offered. It is shown that the attachment point is a model of an electric charge for an observer living in the spacetime. The magnetic charges are forbidden in this model

  11. String effective actions, dualities, and generating solutions

    NARCIS (Netherlands)

    Chemissany, Wissam Ali

    2008-01-01

    This thesis covers in general two separate topics: the string e®ective actions and the geodesic motion of brane solutions. The main theme of the ¯rst topic, i.e., the string e®ective actions, is the construction of the abelian D-brane e®ective action. In the limit of constant ¯eld strengths this

  12. Electron string phenomenon: physics and use

    International Nuclear Information System (INIS)

    Donets, Evgeny D

    2004-01-01

    Electron string phenomenon arises as a result of phase transition of a state of multiply reflected electron beam to this new discovered state of one component electron plasma and can be easily observed in the reflex mode of EBIS operation. The transition goes via a strong instability, which causes considerable electron energy spread, which in its turn suppresses the instability. Electron string state is a stationary state of hot pure electron plasma, which is heated by injected electron beam and cooled because of electron loses. Electron string is quiet in broad regions of experimental parameters, so that it is used for confinement and ionization of positive ions by electron impact to highly charge states similar to electron beams in EBIS. Application of electron strings instead of electron beams for ion production allows to save about 99% of electric power of electron beam and simultaneously to improve reliability of an ion source considerably. The JINR EBIS 'Krion-2' in the string mode of operation is used for production of N 7+ , Ar 16+ and Fe 24+ ion beams and their acceleration to relativistic energies on the facility of the JINR super conducting one turn injection synchrotron 'Nuklotron'. The tubular electron string possibly can exist and it is under study now theoretically and experiments are prepared now. Estimations show that a Tubular Electron String Ion Source (TESIS) could have up to three orders of magnitude higher ion output then a Linear one (LESIS). In frames of nuclear astrophysics electron strings can be used for research of fusion nuclear reactions at low energies in conditions when both beam and target nuclei do not carry orbital electrons. The project NARITA - Nuclear Astrophysics Researches in an Ion Trap Apparatus is proposed. Polarization effects also can be studied

  13. Quantum string test of nonconformal holography

    Energy Technology Data Exchange (ETDEWEB)

    Chen-Lin, Xinyi; Medina-Rincon, Daniel; Zarembo, Konstantin [Nordita, Stockholm University and KTH Royal Institute of Technology,Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden); Department of Physics and Astronomy, Uppsala University,SE-751 08 Uppsala (Sweden)

    2017-04-18

    We compute Lüscher corrections to the effective string tension in the Pilch-Warner background, holographically dual to N=2{sup ∗} supersymmetric Yang-Mills theory. The same quantity can be calculated directly from field theory by solving the localization matrix model at large-N. We find complete agreement between the field-theory predictions and explicit string-theory calculation at strong coupling.

  14. Fast algorithms for approximate circular string matching.

    Science.gov (United States)

    Barton, Carl; Iliopoulos, Costas S; Pissis, Solon P

    2014-03-22

    Circular string matching is a problem which naturally arises in many biological contexts. It consists in finding all occurrences of the rotations of a pattern of length m in a text of length n. There exist optimal average-case algorithms for exact circular string matching. Approximate circular string matching is a rather undeveloped area. In this article, we present a suboptimal average-case algorithm for exact circular string matching requiring time O(n). Based on our solution for the exact case, we present two fast average-case algorithms for approximate circular string matching with k-mismatches, under the Hamming distance model, requiring time O(n) for moderate values of k, that is k=O(m/logm). We show how the same results can be easily obtained under the edit distance model. The presented algorithms are also implemented as library functions. Experimental results demonstrate that the functions provided in this library accelerate the computations by more than three orders of magnitude compared to a naïve approach. We present two fast average-case algorithms for approximate circular string matching with k-mismatches; and show that they also perform very well in practice. The importance of our contribution is underlined by the fact that the provided functions may be seamlessly integrated into any biological pipeline. The source code of the library is freely available at http://www.inf.kcl.ac.uk/research/projects/asmf/.

  15. Transplanckian censorship and global cosmic strings

    Energy Technology Data Exchange (ETDEWEB)

    Dolan, Matthew J. [ARC Centre of Excellence for Particle Physics at the Terascale,School of Physics, University of Melbourne,Melbourne, 3010 (Australia); Draper, Patrick; Kozaczuk, Jonathan; Patel, Hiren [Amherst Center for Fundamental Interactions, Department of Physics,University of Massachusetts,Amherst, MA 01003 (United States)

    2017-04-21

    Large field excursions are required in a number of axion models of inflation. These models also possess global cosmic strings, around which the axion follows a path mirroring the inflationary trajectory. Cosmic strings are thus an interesting theoretical laboratory for the study of transplanckian field excursions. We describe connections between various effective field theory models of axion monodromy and study the classical spacetimes around their supercritical cosmic strings. For small decay constants fM{sub p}/f, the EFT is under control and the string cores undergo topological inflation, which may be either of exponential or power-law type. We show that the exterior spacetime is nonsingular and equivalent to a decompactifying cigar geometry, with the radion rolling in a potential generated by axion flux. Signals are able to circumnavigate infinite straight strings in finite but exponentially long time, t∼e{sup Δa/M{sub p}}. For finite loops of supercritical string in asymptotically flat space, we argue that if topological inflation occurs, then topological censorship implies transplanckian censorship, or that external observers are forbidden from threading the loop and observing the full excursion of the axion.

  16. Cosmic strings in unified gauge theories

    International Nuclear Information System (INIS)

    Everett, A.E.

    1981-01-01

    Some spontaneously broken gauge theories can give rise to stringlike vacuum structures (vortices). It has been pointed out by Vilenkin that in grand unified theories these can be sufficiently massive to have cosmological implications, e.g., in explaining the formation of galaxies. The circumstances in which such structures occur are examined. They do not occur in the simplest grand unified theories, but can occur in some more elaborate models which have been proposed. The cross section for the scattering of elementary particles by strings is estimated. This is used to evaluate the effect of collisions on the dynamics of a collapsing circular string, with particular attention to the question of whether energy dissipation by collision can reduce the rate of formation of black holes by collapsed strings, which may be unacceptably large in models where strings occur. It is found that the effect of collisions is not important in the case of grand unified strings, although it can be important for lighter strings

  17. Zero-point length from string fluctuations

    International Nuclear Information System (INIS)

    Fontanini, Michele; Spallucci, Euro; Padmanabhan, T.

    2006-01-01

    One of the leading candidates for quantum gravity, viz. string theory, has the following features incorporated in it. (i) The full spacetime is higher-dimensional, with (possibly) compact extra-dimensions; (ii) there is a natural minimal length below which the concept of continuum spacetime needs to be modified by some deeper concept. On the other hand, the existence of a minimal length (zero-point length) in four-dimensional spacetime, with obvious implications as UV regulator, has been often conjectured as a natural aftermath of any correct quantum theory of gravity. We show that one can incorporate the apparently unrelated pieces of information-zero-point length, extra-dimensions, string T-duality-in a consistent framework. This is done in terms of a modified Kaluza-Klein theory that interpolates between (high-energy) string theory and (low-energy) quantum field theory. In this model, the zero-point length in four dimensions is a 'virtual memory' of the length scale of compact extra-dimensions. Such a scale turns out to be determined by T-duality inherited from the underlying fundamental string theory. From a low energy perspective short distance infinities are cutoff by a minimal length which is proportional to the square root of the string slope, i.e., α ' . Thus, we bridge the gap between the string theory domain and the low energy arena of point-particle quantum field theory

  18. Bosonization and current algebra of spinning strings

    International Nuclear Information System (INIS)

    Stern, A.

    1996-01-01

    We write down a general geometric action principle for spinning strings in d-dimensional Minkowski space, which is formulated without the use of Grassmann coordinates. Instead, it is constructed in terms of the pull-back of a left invariant Maurer-Cartan form on the d-dimensional Poincare group to the world-sheet. The system contains some interesting special cases. Among them are the Nambu string (as well as, null and tachyonic strings) where the spin vanishes, and also the case of a string with a spin current - but no momentum current. We find the general form for the Virasoro generators, and show that they are first class constraints in the Hamiltonian formulation of the theory. The current algebra associated with the momentum and angular momentum densities are shown, in general, to contain rather complicated anomaly terms which obstruct quantization. As expected, the anomalies vanish when one specializes to the case of the Nambu string, and there one simply recovers the algebra associated with the Poincare loop group. We speculate that there exist other cases where the anomalies vanish, and that these cases give the bosonization of the known pseudoclassical formulations of spinning strings. (orig.)

  19. String pair production in non homogeneous backgrounds

    International Nuclear Information System (INIS)

    Bolognesi, S.; Rabinovici, E.; Tallarita, G.

    2016-01-01

    We consider string pair production in non homogeneous electric backgrounds. We study several particular configurations which can be addressed with the Euclidean world-sheet instanton technique, the analogue of the world-line instanton for particles. In the first case the string is suspended between two D-branes in flat space-time, in the second case the string lives in AdS and terminates on one D-brane (this realizes the holographic Schwinger effect). In some regions of parameter space the result is well approximated by the known analytical formulas, either the particle pair production in non-homogeneous background or the string pair production in homogeneous background. In other cases we see effects which are intrinsically stringy and related to the non-homogeneity of the background. The pair production is enhanced already for particles in time dependent electric field backgrounds. The string nature enhances this even further. For spacial varying electrical background fields the string pair production is less suppressed than the rate of particle pair production. We discuss in some detail how the critical field is affected by the non-homogeneity, for both time and space dependent electric field backgrouds. We also comment on what could be an interesting new prediction for the small field limit. The third case we consider is pair production in holographic confining backgrounds with homogeneous and non-homogeneous fields.

  20. The illusive sound of a Bundengan string

    Science.gov (United States)

    Parikesit, Gea O. F.; Kusumaningtyas, Indraswari

    2017-09-01

    The acoustics of a vibrating string is frequently used as a simple example of how physics can be applied in the field of art. In this paper we describe a simple experiment and analysis using a clipped string. This experiment can generate scientific curiosity among students because the sound generated by the string seem surprising to our senses. The first surprise comes from the gong-like sounds produced by the string, which we usually associate with metallic instruments rather than string instruments. The second surprise comes from the fact that when we shift the clip we perceive an increase of pitch, even though the measured value of the frequency with the maximum amplitude is actually decreased. We use high-speed video recording as well as audio spectral analysis to elucidate the physics behind these two surprises. A set of student activities is prepared to help them follow up their curiosity. Students can make their own clipped string, which is found in Indonesia in an instrument called Bundengan, by setting up their own prepared piano as invented by John Cage.