Electromagnetic radiation of superconducting cosmic strings
Rogozin, D. A.; Zadorozhna, L. V.
2013-12-01
Cosmic strings are relics of the early Universe which can be formed during the phase transitions of fields with spontaneously broken symmetry in the early Universe. Their existence finds support in modern superstrings theories, both in compactification models and in theories with extended additional dimensions. Strings can hold currents, effectively become electrically superconducting wires of astrophysical dimensions. Superconducting cosmic strings can serve as powerful sources of non-thermal radiation in wide energy range. Mechanisms of radiation are synchrotron, synchrotron self-Compton and inverse-Compton on CMB photons radiation of electrons accelerated by bow shock wave, created by magnetosphere of relativistically moving string in intergalactic medium (IGM). Expected fluxes of radiation from the shocked plasma around superconducting cosmic strings are calculated for strings with various tensions and for different cases of their location. Possibilities of strings detection by existing facilities are estimated.
Superconducting Electroweak Strings
Volkov, M S
2007-01-01
Classical solutions describing strings endowed with an electric charge and carrying a constant electromagnetic current are constructed within the bosonic sector of the Electroweak Theory. For any given ratio of the Higgs boson mass to W boson mass and for any Weinberg's angle, these strings comprise a family that can be parameterized by values of the current through their cross section, $I_3$, by their electric charge per unit string length, $I_0$, and by two integers. These parameters determine the electromagnetic and Z fluxes, as well as the angular momentum and momentum densities of the string. For $I_0\\to 0$ and $I_3\\to 0$ the solutions reduce to Z strings, or, for solutions with $I_0=\\pm I_3$, to the W-dressed Z strings whose existence was discussed some time ago.
Fireballs from Superconducting Cosmic Strings
Gruzinov, Andrei
2016-01-01
Thermalized fireballs should be created by cusp events on superconducting cosmic strings. This simple notion allows to reliably estimate particle emission from the cusps in a given background magnetic field. With plausible assumptions about intergalactic magnetic fields, the cusp events can produce observable fluxes of high-energy photons and neutrinos with unique signatures.
Fireballs from superconducting cosmic strings
Gruzinov, Andrei; Vilenkin, Alexander
2017-01-01
Thermalized fireballs should be created by cusp events on superconducting cosmic strings. This simple notion allows to reliably estimate particle emission from the cusps in a given background magnetic field. With plausible assumptions about intergalactic magnetic fields, the cusp events can produce observable fluxes of high-energy photons and neutrinos with unique signatures.
AUTHOR|(SzGeCERN)673023; Blanco Viñuela, Enrique
In each of eight arcs of the 27 km circumference Large Hadron Collider (LHC), 2.5 km long strings of super-conducting magnets are cooled with superfluid Helium II at 1.9 K. The temperature stabilisation is a challenging control problem due to complex non-linear dynamics of the magnets temperature and presence of multiple operational constraints. Strong nonlinearities and variable dead-times of the dynamics originate at strongly heat-flux dependent effective heat conductivity of superfluid that varies three orders of magnitude over the range of possible operational conditions. In order to improve the temperature stabilisation, a proof of concept on-line economic output-feedback Non-linear Model Predictive Controller (NMPC) is presented in this thesis. The controller is based on a novel complex first-principles distributed parameters numerical model of the temperature dynamics over a 214 m long sub-sector of the LHC that is characterized by very low computational cost of simulation needed in real-time optimizat...
CMB distortions from superconducting cosmic strings
Tashiro, Hiroyuki; Sabancilar, Eray; Vachaspati, Tanmay
2012-05-01
We reconsider the effect of electromagnetic radiation from superconducting strings on cosmic microwave background μ and y distortions and derive present (COBE-FIRAS) and future (PIXIE) constraints on the string tension, μs, and electric current, I. We show that absence of distortions of the cosmic microwave background in PIXIE will impose strong constraints on μs and I, leaving the possibility of light strings (Gμs≲10-18) or relatively weak currents (I≲10TeV).
Current discontinuities on superconducting cosmic strings
Energy Technology Data Exchange (ETDEWEB)
Troyan, E., E-mail: et@iaaru.astronautiko.org; Vlasov, Yu. V. [Moscow Institute of Physics and Technology (Russian Federation)
2011-07-15
The propagation of current perturbations on superconducting cosmic strings is considered. The conditions for the existence of discontinuities similar to shock waves have been found. The formulas relating the string parameters and the discontinuity propagation speed are derived. The current growth law in a shock wave is deduced. The propagation speeds of shock waves with arbitrary amplitudes are calculated. The reason why there are no shock waves in the case of time-like currents (in the 'electric' regime) is explained; this is attributable to the shock wave instability with respect to perturbations of the string world sheet.
CMB Distortions from Superconducting Cosmic Strings
Tashiro, Hiroyuki; Vachaspati, Tanmay
2012-01-01
We reconsider the effect of electromagnetic radiation from superconducting strings on cosmic microwave background (CMB) mu- and y-distortions and derive present (COBE-FIRAS) and future (PIXIE) constraints on the string tension, mu_s, and electric current, I. We show that absence of distortions of the CMB in PIXIE will impose strong constraints on mu_s and I, leaving the possibility of light strings (G mu_s < 10^{-18}) or relatively weak currents (I < 10 TeV).
A possible origin of superconducting currents in cosmic strings
Chavez, H; Chavez, Helder; Masperi, Luis
2002-01-01
The scattering and capture of right-handed neutrinos by an Abelian cosmic string in the SO(10) grand unification model are considered. The scattering cross-section of neutrinos per unit length due to the interaction with the gauge and Higgs fields of the string is much larger in its scaling regime than in the friction one because of the larger infrared cutoff of the former.The probability of capture in a zero mode of the string accompanied by the emission of a gauge or Higgs boson shows a resonant peak for neutrino momentum of the order of its mass. Considering the decrease of number of strings per unit comoving volume in the scaling epoch the cosmological consequences of the superconducting strings formed in this regime will be much smaller than those which could be produced already in the friction one.
Gapless superconductivity and string theory
Khlebnikov, S
2014-01-01
Coexistence of superconducting and normal components in nanowires at currents below the critical (a "mixed" state) would have important consequences for the nature and range of potential applications of these systems. From the theoretical perspective, it represents a genuine interaction effect, not seen in the mean-field theory. Here we consider properties of such a state in the gravity dual of a strongly coupled superconductor constructed from D3 and D5 branes. We find numerically uniform gapless solutions containing both components but argue that they are unstable against phase separation, as their free energies are not convex. We speculate on the possible nature of the resulting non-uniform sate ("emulsion") and draw analogies between that state and the familiar mixed state of a type II superconductor in a magnetic field.
Loops and Strings in a Superconducting Lattice Gauge Simulator
Brennen, G. K.; Pupillo, G.; Rico, E.; Stace, T. M.; Vodola, D.
2016-12-01
We propose an architecture for an analog quantum simulator of electromagnetism in 2 +1 dimensions, based on an array of superconducting fluxonium devices. The encoding is in the integer (spin-1) representation of the quantum link model formulation of compact U (1 ) lattice gauge theory. We show how to engineer Gauss' law via an ancilla mediated gadget construction, and how to tune between the strongly coupled and intermediately coupled regimes. The witnesses to the existence of the predicted confining phase of the model are provided by nonlocal order parameters from Wilson loops and disorder parameters from 't Hooft strings. We show how to construct such operators in this model and how to measure them nondestructively via dispersive coupling of the fluxonium islands to a microwave cavity mode. Numerical evidence is found for the existence of the confined phase in the ground state of the simulation Hamiltonian on a ladder geometry.
Superconducting Cosmic String with Propagating Torsion
Ferreira, C N; Garcia de Andrade, L C
2000-01-01
We show that it is possible to construct a consistent model describing a current-carrying cosmic string endowed with torsion. The torsion contribution to the gravitational force and geodesics of a test-particle moving around the SCCS are analyzed. In particular, we point out two interesting astrophysical phenomena in which the higher magnitude force we derived may play a critical role: the dynamics of compact objects orbiting the torsioned SCCS and accretion of matter onto it. The deficit angle associated to the SCCS can be obtained and compared with data from the Cosmic Background Explorer (COBE) satellite. We also derived a value for the torsion contribution to matter density fluctuations in the early Universe.
Loops and strings in a superconducting lattice gauge simulator
Brennen, G K; Rico, E; Stace, T M; Vodola, D
2015-01-01
We propose a quantum simulation of electromagnetism in (2+1) dimensions using an array of superconducting fluxonium devices. The encoding is in the integer (S=1) representation of the quantum link model formulation of compact U(1) lattice gauge theory. We show how to engineer the Gauss constraint via an ancilla mediated gadget construction and how to tune between the strongly coupled and intermediately coupled regimes. The witnesses to the existence of the predicted confining phase of the model are provided by non-local order parameters from Wilson loops and disorder parameters from 't Hooft strings and we show how to measure these operators non-destructively via dispersive coupling of the fluxonium islands to a microwave cavity mode. Evidence for existence of the confined phase in the ground state of the simulation Hamiltonian is found by DMRG calculations on a ladder geometry.
String bit models for superstring
Energy Technology Data Exchange (ETDEWEB)
Bergman, O.; Thorn, C.B.
1995-12-31
The authors extend the model of string as a polymer of string bits to the case of superstring. They mainly concentrate on type II-B superstring, with some discussion of the obstacles presented by not II-B superstring, together with possible strategies for surmounting them. As with previous work on bosonic string work within the light-cone gauge. The bit model possesses a good deal less symmetry than the continuous string theory. For one thing, the bit model is formulated as a Galilei invariant theory in (D {minus} 2) + 1 dimensional space-time. This means that Poincare invariance is reduced to the Galilei subgroup in D {minus} 2 space dimensions. Naturally the supersymmetry present in the bit model is likewise dramatically reduced. Continuous string can arise in the bit models with the formation of infinitely long polymers of string bits. Under the right circumstances (at the critical dimension) these polymers can behave as string moving in D dimensional space-time enjoying the full N = 2 Poincare supersymmetric dynamics of type II-B superstring.
Quench Protection and Powering in a String of Superconducting Magnets for the Large Hadron Collider
Krainz, G
1997-01-01
Practical experience has been attained on the LHC Test String (String~1), composed of one 3~m long superconducting twin-aperture prototype quadrupole and three 10~m long superconducting twin-aperture prototype dipoles. The protection diodes are housed in the cold mass of the short straight section. The quench protection system acts on the half-cell level. During the operation of the LHC Test String, magnet quenches have been provoked manually by firing the quench heaters or occured manually by exceeding the critical temperature or critical current density of the superconductor. Most of the data could be measured while some parameters (magnet current, diode current, average temperature, etc.) cannot be directly measured. A simulation progam has been developed to calculate the missing data. The validation of the model has been performed by comparing measured and simulated data. The modelling of the quench behaviour of the final version of the LHC magnets show that hot-spot temperatures and voltages to ground ca...
Stability Analysis of The Twisted Superconducting Semilocal Strings
Garaud, Julien
2007-01-01
We study the stability properties of the twisted vortex solutions in the semilocal Abelian Higgs model with a global $\\mathbf{SU}(2)$ invariance. This model can be viewed as the Weinberg-Salam theory in the limit where the non-Abelian gauge field decouples, or as a two component Ginzburg-Landau theory. The twisted vortices are characterized by a constant global current ${\\cal I}$, and for ${\\cal I}\\to 0$ they reduce to the semilocal strings, that is to the Abrikosov-Nielsen-Olesen vortices embedded into the semilocal model. Solutions with ${\\cal I}\
Ballonet String Model of Molecules
Directory of Open Access Journals (Sweden)
Gavril NIAC
2008-06-01
Full Text Available Strings of ballonets, modelling rows of orbitals, are assembled to molecule models by crossing them properly. The ballonets at the ends of the strings of 2, 3, 4 or 5 spheres represent bonding orbitals of hydrogen with other elements like C, N or O (the proton being inside the sphere, as well as nonbonding orbitals. The ballonets between them are modelling bonding orbitals among elements other than hydrogen - except the double bond in diborane, the atomic cores laying at the junction of two or more spheres.Advantages of elastic sphere models range from self-adjusting bond angles to resistance when closing cycles like cyclopropane or modeling double bonds.Examples comprise alkanes, including platonic hydrocarbons, ethene, acetylene, and some inorganic molecules.
String Interactions in c=1 Matrix Model
De Boer, J; Verlinde, E; Yee, J T; Boer, Jan de; Sinkovics, Annamaria; Verlinde, Erik; Yee, Jung-Tay
2004-01-01
We study string interactions in the fermionic formulation of the c=1 matrix model. We give a precise nonperturbative description of the rolling tachyon state in the matrix model, and discuss S-matrix elements of the c=1 string. As a first step to study string interactions, we compute the interaction of two decaying D0-branes in terms of free fermions. This computation is compared with the string theory cylinder diagram using the rolling tachyon ZZ boundary states.
Bursts of gravitational radiation from superconducting cosmic strings and the neutrino mass spectrum
Energy Technology Data Exchange (ETDEWEB)
Mosquera Cuesta, Herman J. [Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)]|[Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil). Lab. de Cosmologia e Fisica Experimental de Altas Energias; Morejon Gonzalez, Danays [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil)
2001-02-01
Berezinsky, Hnatyk and Vilenkin showed that superconducting cosmic strings could be central engines for cosmological gamma-ray bursts and for producing the neutrino component of ultra-high energy cosmic rays. A consequence of this mechanism would be that a detectable cusp-triggered gravitational wave burst should be release simultaneously with the {gamma}-ray surge. If contemporary measurements of both {gamma} and {nu} radiation could be made for any particular source, then the cosmological time-delay between them might be useful for putting unprecedently tight bounds on the neutrino mass spectrum. Such measurements could consistently verify or rule out the model since strictly correlated behaviour is expected for the duration of the event and for the time variability of the spectra. (author)
Brane World Models Need Low String Scale
Antoniadis, Ignatios; Calmet, Xavier
2011-01-01
Models with large extra dimensions offer the possibility of the Planck scale being of order the electroweak scale, thus alleviating the gauge hierarchy problem. We show that these models suffer from a breakdown of unitarity at around three quarters of the low effective Planck scale. An obvious candidate to fix the unitarity problem is string theory. We therefore argue that it is necessary for the string scale to appear below the effective Planck scale and that the first signature of such models would be string resonances. We further translate experimental bounds on the string scale into bounds on the effective Planck scale.
Superconductivity due to Condensation of Monopoles around RCD Strings in SU(2 Gauge Theory
Directory of Open Access Journals (Sweden)
B. S. Rajput
2010-01-01
Full Text Available The study of the condensation of monopoles and the resulting chromomagnetic superconductivity have been undertaken in restricted chromodynamics of SU(2 gauge theory. Constructing the RCD Lagrangian and the partition function for monopoles in terms of string action and the action of the current around the strings, the monopole current in RCD chromo magnetic superconductor has been derived and it has shown that in London' limit the penetration length governs the monopole density around RCD string in chromo magnetic superconductors while with finite (nonzero coherence length the leading behavior of the monopole density at large distances from the string is controlled by the coherence length and not by the penetration length.
QCD strings as constrained grassmannian sigma model
Viswanathan, K S; Viswanathan, K S; Parthasarathy, R
1995-01-01
We present calculations for the effective action of string world sheet in R3 and R4 utilizing its correspondence with the constrained Grassmannian sigma model. Minimal surfaces describe the dynamics of open strings while harmonic surfaces describe that of closed strings. The one-loop effective action for these are calculated with instanton and anti-instanton background, reprsenting N-string interactions at the tree level. The effective action is found to be the partition function of a classical modified Coulomb gas in the confining phase, with a dynamically generated mass gap.
Gauge invariant actions for string models
Energy Technology Data Exchange (ETDEWEB)
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.
A Matrix Model for Type 0 Strings
Peñalba, J P
1999-01-01
A matrix model for type 0 strings is proposed. It consists in making a non-supersymmetric orbifold projection in the Yang-Mills theory and identifying the infrared configurations of the system at infinite coupling with strings. The correct partition function is calculated. Also, the usual spectrum of branes is found. Both type A and B models are constructed. The model in a torus contains all the degrees of freedom and interpolates between the four string theories (IIA, IIB, 0A, 0B) and the M theory as different limits are taken.
On Dimer Models and Closed String Theories
Sarkar, Tapobrata
2007-01-01
We study some aspects of the recently discovered connection between dimer models and D-brane gauge theories. We argue that dimer models are also naturally related to closed string theories on non compact orbifolds of $\\BC^2$ and $\\BC^3$, via their twisted sector R charges, and show that perfect matchings in dimer models correspond to twisted sector states in the closed string theory. We also use this formalism to study the combinatorics of some unstable orbifolds of $\\BC^2$.
Lake, Matthew J
2015-01-01
The discovery of a large number of supermassive black holes at redshifts $z> 6$, when the Universe was only nine hundred million years old, has raised the fundamental question of how such massive compact objects could form in a (cosmologically) short time interval. Each of the proposed standard scenarios for black hole formation, involving rapid accretion of seed black holes, or black hole mergers, faces severe theoretical difficulties in explaining the short time formation of supermassive objects. In the present Letter, we propose an alternative scenario for the formation of supermassive black holes in the early Universe in which energy transfer from superconducting cosmic strings, piercing small seed black holes, is the main physical process leading to rapid mass increase. The increase in mass of a primordial seed black hole pierced by two antipodal strings is estimated and it is shown that this increases linearly in time. Due to the high energy transfer rate from the cosmic strings, we find that supermassi...
A rotating string model versus baryon spectra
Sonnenschein, Jacob
2014-01-01
We continue our program of describing hadrons as rotating strings with massive endpoints. In this paper we propose models of baryons and confront them with the baryon Regge trajectories. We show that these are best fitted by a model of a single string with a quark at one endpoint and a diquark at the other. This model is preferred over the Y-shaped string model with a quark at each endpoint. We show how the model follows from a stringy model of the holographic baryon which includes a baryonic vertex connected with $N_c$ strings to flavor probe branes. From fitting to baryonic data we find that there is no clear evidence for a non-zero baryonic vertex mass, but if there is such a mass it should be located at one of the string endpoints. The available baryon trajectories in the angular momentum plane $(J,M^2)$, involving light, strange, and charmed baryons, are rather well fitted when adding masses to the string endpoints, with a single universal slope $\\alp = 0.95$ GeV$^{-2}$. Most of the results for the quark...
Topological strings linking with quasiparticle exchange in superconducting Dirac semimetals
Lopes, Pedro L. e. S.; Teo, Jeffrey C. Y.; Ryu, Shinsei
2017-06-01
We demonstrate a topological classification of vortices in three-dimensional time-reversal invariant topological superconductors based on superconducting Dirac semimetals with an s -wave superconducting order parameter by means of a pair of numbers (NΦ,N ) , accounting how many units NΦ of magnetic fluxes h c /4 e and how many N chiral Majorana modes the vortex carries. From these quantities, we introduce a topological invariant, which further classifies the properties of such vortices under linking processes. While such processes are known to be related to instanton processes in a field theoretic description, we demonstrate here that they are, in fact, also equivalent to the fractional Josephson effect on junctions based at the edges of quantum spin Hall systems. This allows one to consider microscopically the effects of interactions in the linking problem. We therefore demonstrate that associated to links between vortices, one has the exchange of quasiparticles, either Majorana zero modes, or e /2 quasiparticles, which allows for a topological classification of vortices in these systems, seen to be Z8 classified. While NΦ and N are shown to be both even or odd in the weakly interacting limit, in the strongly interacting scenario one loosens this constraint. In this case, one may have further fractionalization possibilities for the vortices, whose excitations are described by SO(3) 3 -like conformal field theories with quasiparticle exchanges of more exotic types.
The strings connection: MSSM-like models from strings
Energy Technology Data Exchange (ETDEWEB)
Nilles, Hans Peter [Bethe Center for Theoretical Physics (BCTP) and Physikalisches Institut der Universitaet Bonn, Bonn (Germany)
2014-05-15
String theory constructions towards the MSSM allow us to identify some general properties that could be relevant for tests at the LHC. They originate from the geometric structure of compactification and the location of fields in extra-dimensional space. Within the framework of the heterotic MiniLandscape we extract some generic lessons for supersymmetric model building. Among them is a specific pattern of SUSY breakdown based on mirage mediation and remnants of extended supersymmetry. This leads to a split spectrum with heavy scalars of the first two families of quarks and leptons and suppressed masses for gauginos, top partners and Higgs bosons. The models exhibit some specific form of hidden supersymmetry consistent with the high mass of the Higgs boson and all presently available experimental constraints. The most compelling picture is based on precision gauge coupling unification that might be in the kinematic reach of the LHC. (orig.)
Cooling Strings of Superconducting Devices below 2 K the Helium II Bayonet Heat Exchanger
Lebrun, P; Tavian, L; Van Weelderen, R
1998-01-01
High-energy particle accelerators and colliders contain long strings of superconducting devices - acceleration RF cavities and magnets - operating at high field, which may require cooling in helium II below 2 K. In order to maintain adequate operating conditions, the applied or generated heat loads must be extracted and transported with minimum temperature difference. Conventional cooling schemes based on conductive or convective heat transport in pressurized helium II very soon reach their intrinsic limits of thermal impedance over extended lengths. We present the concept of helium II bayonet heat exchanger, which has been developed at CERN for the magnet cooling scheme of the Large Hadron Collider (LHC), and describe its specific advantages as a slim, quasi-isothermal heat sink. Experimental results obtained on several test set-ups, and a prototype magnet string have permitted to validate its performance and sizing rules, for transporting linear heat loads in the W.m-1 range over distances of several tens o...
Relativistic Model for two-band Superconductivity
Ohsaku, Tadafumi
2003-01-01
To understand the superconductivity in MgB2, several two-band models of superconductivity were proposed. In this paper, by using the relativistic fermion model, we clearize the effect of the lower band in the superconductivity.
Stochastic string models with continuous semimartingales
Bueno-Guerrero, Alberto; Moreno, Manuel; Navas, Javier F.
2015-09-01
This paper reformulates the stochastic string model of Santa-Clara and Sornette using stochastic calculus with continuous semimartingales. We present some new results, such as: (a) the dynamics of the short-term interest rate, (b) the PDE that must be satisfied by the bond price, and (c) an analytic expression for the price of a European bond call option. Additionally, we clarify some important features of the stochastic string model and show its relevance to price derivatives and the equivalence with an infinite dimensional HJM model to price European options.
Kahler stabilized, modular invariant heterotic string models
Energy Technology Data Exchange (ETDEWEB)
Gaillard, Mary K.; Gaillard, Mary K.; Nelson, Brent D.
2007-03-19
We review the theory and phenomenology of effective supergravity theories based on orbifold compactifications of the weakly-coupled heterotic string. In particular, we consider theories in which the four-dimensional theory displays target space modular invariance and where the dilatonic mode undergoes Kahler stabilization. A self-contained exposition of effective Lagrangian approaches to gaugino condensation and heterotic string theory is presented, leading to the development of the models of Binétruy, Gaillard and Wu. Various aspects of the phenomenology of this class of models are considered. These include issues of supersymmetry breaking and superpartner spectra, the role of anomalous U(1) factors, issues of flavor and R-parity conservation, collider signatures, axion physics, and early universe cosmology. For the vast majority of phenomenological considerations the theories reviewed here compare quite favorably to other string-derived models in the literature. Theoretical objections to the framework and directions for further research are identified and discussed.
Gauge Unification from Split Supersymmetric String Models
Kokorelis, Christos
2016-01-01
We discuss the unification of gauge coupling constants in non-supersymmetric open string vacua that possess the properties of Split Supersymmetry, namely the Standard Model with Higgsinos at low energies and where the Standard model spectrum is always accompanied by right handed neutrinos. These vacua achieve partial unification of two out of three (namely SU(3)$_c$, SU(2), U(1)) running gauge couplings, possess massive gauginos and light Higgsinos at low energies and also satisfy $sin^2\\theta_w (M_s) = 3/8$. These vacua are based on four dimensional orbifold $Z_3 \\times Z_3$ compactifications of string IIA orientifolds with D6-branes intersecting at angles, where the (four dimensional) chiral fermions of the Standard Model appear as opens strings streching between the intersections of seven dimensional objects the so called D6-branes.
Quantisation of the string fragmentation model
Energy Technology Data Exchange (ETDEWEB)
Artru, X.; Bowler, M.G.
1988-01-01
We quantise the classical Artu-Mennessier strong model with a Feynman sum over histories method. This procedure yields both propagation amplitudes and a Veneziano mass spectrum for mesons, with resonance poles for unstable states. Applied to the process e/sup +/e/sup -/ -> hadrons our amplitudes justify previous applications of string models and in particular the relative amplitudes for different string configurations are in agreement with a recent conjecture of Andersson and Hofmann which can account for the observed Bose-Einstein correlations in e/sup +/e/sup -/ annihilation.
Heterotic String Models in Curved Spacetime
Bars, Itzhak
1992-01-01
We explore the possibility of string theories in only four spacetime dimensions without any additional compactified dimensions. We show that, provided the theory is defined in curved spacetime that has a cosmological interpration, it is possible to construct consistent heterotic string theories based on a few non-compact current algebra cosets. We classify these models. The gauge groups that emerge fall within a remarkably narrow range and include the desirable low energy flavor symmetry of $SU(3)\\times SU(2)\\times U(1)$. The quark and lepton states, which come in color triplets and $SU(2)$ doublets, are expected to emerge in several families.
String Field Equations from Generalized Sigma Model
Energy Technology Data Exchange (ETDEWEB)
Bardakci, K.; Bernardo, L.M.
1997-01-29
We propose a new approach for deriving the string field equations from a general sigma model on the world-sheet. This approach leads to an equation which combines some of the attractive features of both the renormalization group method and the covariant beta function treatment of the massless excitations. It has the advantage of being covariant under a very general set of both local and non-local transformations in the field space. We apply it to the tachyon, massless and first massive level, and show that the resulting field equations reproduce the correct spectrum of a left-right symmetric closed bosonic string.
String coupling and interactions in type IIB matrix model
Kitazawa, Yoshihisa
2008-01-01
We investigate the interactions of closed strings in IIB matrix model. The basic interaction of the closed superstring is realized by the recombination of two intersecting strings. Such interaction is investigated in IIB matrix model via two dimensional noncommutative gauge theory in the IR limit. By estimating the probability of the recombination, we identify the string coupling g_s in IIB matrix model. We confirm that our identification is consistent with matrix string theory.
Some Exact Solutions of Magnetized viscous model in String Cosmology
Singh, C P
2012-01-01
In this paper we study anisotropic Bianchi-V universe with magnetic field and bulk viscous fluid in string cosmology. Exact solutions of the field equations are obtained by using the equation of state for a cloud of strings and a relationship between bulk viscous coefficient and expansion scalar. The bulk viscous coefficient is assumed to be inversely proportional to the expansion scalar. It is interesting to examine the effects of magnetized bulk viscous string model in early and late stages of the evolution of the universe. This paper investigates the different string models like geometrical(Nambu string), Takabayashi (p-string) and Reddy string models by taking certain physical conditions. The introduction of magnetic field or bulk viscosity or both results in rapid change in scale factors as well as in the classical potential. The presence of viscosity prevents the universe to be empty in its future evolution. The physical and geometrical aspects of each string model are discussed in detail.
Bianchi type IX string cosmological model in general relativity
Indian Academy of Sciences (India)
Raj Bali; Shuchi Dave
2001-04-01
We have investigated Bianchi type IX string cosmological models in general relativity. To get a determinate solution, we have assumed a condition ρ= i.e. rest energy density for a cloud of strings is equal to the string tension density. The various physical and geometrical aspects of the models are also discussed.
Semiclassical string spectrum in a string model dual to large N QCD
Pons, J M; Talavera, P
2004-01-01
We explore the string spectrum in the Witten QCD model by considering classical string configurations, thereby obtaining energy formulas for quantum states with large excitation quantum numbers representing glueballs and Kaluza-Klein states. In units of the string tension, the energies of all states increase as the 't Hooft coupling $\\lambda $ is decreased, except the energies of glueballs corresponding to strings lying on the horizon, which remain constant. We argue that some string solutions can be extrapolated to the small $\\lambda $ regime. We also find the classical mechanics description of supergravity glueballs in terms of point-like string configurations oscillating in the radial direction, and reproduce the glueball energy formula previously obtained by solving the equation for the dilaton fluctuation.
Local string models and moduli stabilisation
Quevedo, Fernando
2015-03-01
A brief overview is presented of the progress made during the past few years on the general structure of local models of particle physics from string theory including: moduli stabilisation, supersymmetry breaking, global embedding in compact Calabi-Yau compactifications and potential cosmological implications. Type IIB D-brane constructions and the Large Volume Scenario (LVS) are discussed in some detail emphasising the recent achievements and the main open questions.
Exotic spacetimes, superconducting strings with linear momentum, and (not quite) all that
Gleiser, R J; Gleiser, Reinaldo J.; Tiglio, Manuel H.
2000-01-01
We derive the general exact vacuum metrics associated with a stationary (non static), non rotating, cylindrically symmetric source. An analysis of the geometry described by these vacuum metrics shows that they contain a subfamily of metrics that, although admitting a consistent time orientation, display "exotic" properties, such as "trapping" of geodesics and closed causal curves through every point. The possibility that such spacetimes could be generated by a superconducting string, endowed with a neutral current and momentum, has recently been considered by Thatcher and Morgan. Our results, however, differ from those found by Thatcher and Morgan, and the discrepancy is explained. We also analyze the general possibility of constructing physical sources for the exotic metrics, and find that, under certain restrictions, they must always violate the dominant energy condition (DEC). We illustrate our results by explicitly analyzing the case of concentric shells, where we find that in all cases the external vacuu...
Dual Superconductivity in Abelian Higgs Model of QCD
Rajput, B. S.
2017-04-01
The study of generalized field associated with Abelian dyons has been undertaken and it has been demonstrated that topologically, a non-Abelian gauge theory is equivalent to a set of Abelian gauge theories supplemented by dyons which undergo condensation leading to confinement and consequently to superconducting model of QCD vacuum, where the Higgs field plays the role of a regulator only. Constructing the effective action for dyonic field in Abelian projection of QCD, it has been demonstrated that any charge (electrical or magnetic) of dyon screens its own direct potential to which it minimally couples and anti-screens the dual potential leading to dual superconductivity in accordance with generalized Meissner effect. In this Abelian projection of QCD an Abelian Higgs model (AHM) has been successfully constructed and it has been shown to incorporate dual superconductivity and confinement as the consequence of dyonic condensation. It has been demonstrated that in AHM t' Hooft loop creates the string (AHM-string) around which the monopole current under London limit leads to vanishing coherence length in the chromo-magnetic superconductor. It has also been shown that in London limit the squared density of monopole current around AHM-string has a maximum at the distance of the order of penetration length.
c=1 String as a Topological Model
Ishikawa, H
1994-01-01
The discrete states in the $c=1$ string are shown to be the physical states of a certain topological sigma model. We define a set of new fields directly from $c=1$ variables, in terms of which the BRST charge and energy-momentum tensor are rewritten as those of the topological sigma model. Remarkably, ground ring generator $x$ turns out to be a coordinate of the sigma model. All of the discrete states realize a graded ring which contains ground ring as a subset.
Energy Technology Data Exchange (ETDEWEB)
Kneipp, Marco A.C. [Universidade do Estado, Rio de Janeiro, RJ (Brazil). Dept. de Fisica Teorica; Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil). Coordenacao de Teoria de Campos e Particulas
2004-12-01
We review some recent developments on BPS string solutions and monopole confinement in the Higgs (or color) superconducting phase of N = 2 and N = 4 super Yang-Mills theories. In particular, the monopole magnetic fluxes are shown to be always integer linear combinations of string fluxes. Moreover, a bound for the threshold length of the string breaking is obtained. When the gauge group SU(N) is broken to Z{sub N}, the BPS string tension satisfies the Casimir scaling law. Furthermore, in the SU(3) case the string solutions are such that they allow the formation of a confining system with three monopoles. (author)
String Models, Stability and Regge Trajectories for Hadron States
Sharov, G S
2013-01-01
Various string models of mesons and baryons include a string carrying 2 or 3 massive points (quarks or antiquarks). Rotational states (planar uniform rotations) of these systems generate quasilinear Regge trajectories and may be used for describing excited hadron states on these trajectories. For different string models of baryon we are to solve the problem of choice between them and the stability problem for their rotational states. An unexpected result is that for the Y string baryon model these rotations are unstable with respect to small disturbances on the classical level. This instability has specific feature, disturbances grow linearly, whereas for the linear string baryon model they grow exponentially and may increase predictions for baryon's width $\\Gamma$. The classical instability of rotational states and nonstandard Regge slope are the arguments in favor of the stable simplest model of string with massive ends both for baryons and mesons. Rotational states of this model with two types of spin-orbi...
Superconducting vortices in semilocal models.
Forgács, Péter; Reuillon, Sébastien; Volkov, Mikhail S
2006-02-01
It is shown that the SU(2) semilocal model--the Abelian Higgs model with two complex scalars--admits a new class of stationary, straight string solutions carrying a persistent current and having finite energy per unit length. In the plane orthogonal to their direction they correspond to a nontrivial deformation of the embedded Abrikosov-Nielsen-Olesen (ANO) vortices by the current flowing through them. The new solutions bifurcate with the ANO vortices in the limit of vanishing current. They can be either static or stationary. In the stationary case, the relative phase of the two scalars rotates at constant velocity, giving rise to an electric field and angular momentum, while the energy remains finite. The new static vortex solutions have lower energy than the ANO vortices and could be of considerable importance in various physical systems (from condensed matter to cosmic strings).
A matrix model from string field theory
Directory of Open Access Journals (Sweden)
Syoji Zeze
2016-09-01
Full Text Available We demonstrate that a Hermitian matrix model can be derived from level truncated open string field theory with Chan-Paton factors. The Hermitian matrix is coupled with a scalar and U(N vectors which are responsible for the D-brane at the tachyon vacuum. Effective potential for the scalar is evaluated both for finite and large N. Increase of potential height is observed in both cases. The large $N$ matrix integral is identified with a system of N ZZ branes and a ghost FZZT brane.
A matrix model from string field theory
Zeze, Syoji
2016-09-01
We demonstrate that a Hermitian matrix model can be derived from level truncated open string field theory with Chan-Paton factors. The Hermitian matrix is coupled with a scalar and U(N) vectors which are responsible for the D-brane at the tachyon vacuum. Effective potential for the scalar is evaluated both for finite and large N. Increase of potential height is observed in both cases. The large N matrix integral is identified with a system of N ZZ branes and a ghost FZZT brane.
Superconducting cavity model for LEP
1979-01-01
A superconducting cavity model is being prepared for testing in a vertical cryostat.At the top of the assembly jig is H.Preis while A.Scharding adjusts some diagnostic equipment to the cavity. See also photo 7912501X.
With string model to time series forecasting
Pinčák, Richard; Bartoš, Erik
2015-10-01
Overwhelming majority of econometric models applied on a long term basis in the financial forex market do not work sufficiently well. The reason is that transaction costs and arbitrage opportunity are not included, as this does not simulate the real financial markets. Analyses are not conducted on the non equidistant date but rather on the aggregate date, which is also not a real financial case. In this paper, we would like to show a new way how to analyze and, moreover, forecast financial market. We utilize the projections of the real exchange rate dynamics onto the string-like topology in the OANDA market. The latter approach allows us to build the stable prediction models in trading in the financial forex market. The real application of the multi-string structures is provided to demonstrate our ideas for the solution of the problem of the robust portfolio selection. The comparison with the trend following strategies was performed, the stability of the algorithm on the transaction costs for long trade periods was confirmed.
An Inflationary Model in String Theory
Iizuka, N; Iizuka, Norihiro; Trivedi, Sandip P.
2004-01-01
We construct a model of inflation in string theory after carefully taking into account moduli stabilization. The setting is a warped compactification of Type IIB string theory in the presence of D3 and anti-D3-branes. The inflaton is the position of a D3-brane in the internal space. By suitably adjusting fluxes and the location of symmetrically placed anti-D3-branes, we show that at a point of enhanced symmetry, the inflaton potential V can have a broad maximum, satisfying the condition V''/V << 1 in Planck units. On starting close to the top of this potential the slow-roll conditions can be met. Observational constraints impose significant restrictions. As a first pass we show that these can be satisfied and determine the important scales in the compactification to within an order of magnitude. One robust feature is that the scale of inflation is low, H = O(10^{10}) GeV. Removing the observational constraints makes it much easier to construct a slow-roll inflationary model. Generalizations and conseque...
Hierarchic Models of Turbulence, Superfluidity and Superconductivity
Kaivarainen, A
2000-01-01
New models of Turbulence, Superfluidity and Superconductivity, based on new Hierarchic theory, general for liquids and solids (physics/0102086), have been proposed. CONTENTS: 1 Turbulence. General description; 2 Mesoscopic mechanism of turbulence; 3 Superfluidity. General description; 4 Mesoscopic scenario of fluidity; 5 Superfluidity as a hierarchic self-organization process; 6 Superfluidity in 3He; 7 Superconductivity: General properties of metals and semiconductors; Plasma oscillations; Cyclotron resonance; Electroconductivity; 8. Microscopic theory of superconductivity (BCS); 9. Mesoscopic scenario of superconductivity: Interpretation of experimental data in the framework of mesoscopic model of superconductivity.
String networks with junctions in competition models
Avelino, P. P.; Bazeia, D.; Losano, L.; Menezes, J.; de Oliveira, B. F.
2017-03-01
In this work we give specific examples of competition models, with six and eight species, whose three-dimensional dynamics naturally leads to the formation of string networks with junctions, associated with regions that have a high concentration of enemy species. We study the two- and three-dimensional evolution of such networks, both using stochastic network and mean field theory simulations. If the predation, reproduction and mobility probabilities do not vary in space and time, we find that the networks attain scaling regimes with a characteristic length roughly proportional to t 1 / 2, where t is the physical time, thus showing that the presence of junctions, on its own, does not have a significant impact on their scaling properties.
String networks with junctions in competition models
Avelino, P P; Losano, L; Menezes, J; de Oliveira, B F
2016-01-01
In this work we give specific examples of competition models, with six and eight species, whose three-dimensional dynamics naturally leads to the formation of string networks with junctions, associated with regions that have a high concentration of enemy species. We study the two- and three-dimensional evolution of such networks, both using stochastic network and mean field theory simulations. If the predation, reproduction and mobility probabilities do not vary in space and time, we find that the networks attain scaling regimes with a characteristic length roughly proportional to $t^{1/2}$, where $t$ is the physical time, thus showing that the presence of junctions, on its own, does not have a significant impact on their scaling properties.
Some exact solutions of magnetized viscous model in string cosmology
Indian Academy of Sciences (India)
C P Singh
2014-07-01
In this paper, we study anisotropic Bianchi-V Universe with magnetic field and bulk viscous fluid in string cosmology. Exact solutions of the field equations are obtained by using the equation of state (EoS) for a cloud of strings, and a relationship between bulk viscous coefficient and scalar expansion. The bulk viscous coefficient is assumed to be inversely proportional to the expansion scalar. It is interesting to examine the effects of magnetized bulk viscous string model in early and late stages of evolution of the Universe. This paper presents different string models like geometrical (Nambu string), Takabayasi (p-string) and Reddy string models by taking certain physical conditions. We discuss the nature of classical potential for viscous fluid with and without magnetic field. The presence of bulk viscosity stops the Universe from becoming empty in its future evolution. It is observed that the Universe expands with decelerated rate in the presence of viscous fluid with magnetic field whereas, it expands with marginal inflation in the presence of viscous fluid without magnetic field. The other physical and geometrical aspects of each string model are discussed in detail.
Observational Equivalence of Discrete String Models and Market Models
Kerkhof, F.L.J.; Pelsser, A.
2002-01-01
In this paper we show that, contrary to the claim made in Longsta, Santa-Clara, and Schwartz (2001a) and Longsta, Santa-Clara, and Schwartz (2001b), discrete string models are not more parsimonious than market models.In fact, they are found to be observationally equivalent.We derive that, for the es
Fermionic models with superconducting circuits
Energy Technology Data Exchange (ETDEWEB)
Las Heras, Urtzi; Garcia-Alvarez, Laura; Mezzacapo, Antonio; Lamata, Lucas [University of the Basque Country UPV/EHU, Department of Physical Chemistry, Bilbao (Spain); Solano, Enrique [University of the Basque Country UPV/EHU, Department of Physical Chemistry, Bilbao (Spain); IKERBASQUE, Basque Foundation for Science, Bilbao (Spain)
2015-12-01
We propose a method for the efficient quantum simulation of fermionic systems with superconducting circuits. It consists in the suitable use of Jordan-Wigner mapping, Trotter decomposition, and multiqubit gates, be with the use of a quantum bus or direct capacitive couplings. We apply our method to the paradigmatic cases of 1D and 2D Fermi-Hubbard models, involving couplings with nearest and next-nearest neighbours. Furthermore, we propose an optimal architecture for this model and discuss the benchmarking of the simulations in realistic circuit quantum electrodynamics setups. (orig.)
Three Family Models from the Heterotic String
Raby, S
2005-01-01
In this talk I outline work done in collaboration with R.J. Zhang and T. Kobayashi. We show how to construct the equivalent of three family orbifold GUTs in five dimensions from the heterotic string. I focus on one particular model with E(6) gauge symmetry in 5D, the third family and Higgs doublet coming from the 5D bulk and the first two families living on 4D SO(10) branes. Note the E(6) gauge symmetry is broken to Pati-Salam in 4D which subsequently breaks to the Standard Model gauge symmetry via the Higgs mechanism. The model has two flaws, one fatal and one perhaps only unaesthetic. The model has a small set of vector-like exotics with fractional electromagnetic charge. Unfortunately not all of these states obtain mass at the compactification scale. This flaw is fatal. The second problem is R parity violating interactions. These problems may be avoidable in alternate orbifold compactification schemes. It is these problems which we discuss in this talk.
Signatures of low-scale string models at the LHC
Hashi, Manami
2011-01-01
Low-scale string models, in which the string scale M_s is of the order of TeV with large extra dimensions, can solve the problems of scale hierarchy and non-renormalizable quantum gravity in the standard model. String excited states of the standard model particles are possibly observed as resonances in the dijet invariant mass distribution at the LHC. There are two properties to distinguish whether the resonances are due to low-scale string or some other "new physics". One is a characteristic angular distribution in dijet events at the resonance due to spin degeneracy of string excited states, and the other is an appearance of the second resonance at a characteristic mass of second string excited states. We investigate a possibility to observe these evidences of low-scale string models by Monte Carlo simulations with a reference value of M_s = 4 TeV at sqrt{s} = 14 TeV. It is shown that spin degeneracy at the dijet resonance can be observed by looking the chi-distribution with integrated luminosity of 20 fb^-...
Cold, warm, and composite (cool) cosmic string models
Carter, B
1994-01-01
The dynamical behaviour of a cosmic string is strongly affected by any reduction of the effective string tension $T$ below the constant value $T=m^2$ say that characterizes the simple, longitudinally Lorentz invariant, Goto Nambu string model in terms of a fixed mass scale $m$ whose magnitude depends on that of the Higgs field responsible for the existence of the string. Such a reduction occurs in the standard "hot" cosmic string model in which the effect of thermal perturbations of a simple Goto Nambu model is expressed by the formula $T^2=m^2(m^2-2\\pi\\Theta^2/3)$, where $\\Theta$ is the string temperature. A qualitatively similar though analytically more complicated tension reduction phenomenon occurs in "cold" conducting cosmic string models where the role of the temperature is played by an effective chemical potential $\\mu$ that is constructed as the magnitude of the phase $\\phi$ of a bosonic condensate of the kind whose existence was first proposed by Witten. The present article describes the construction...
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
Boundary conditions and gluing conditions for open strings and D-branes in the SL(2, R) WZWN model, corresponding to AdS , are discussed. Some boundary conditions and gluing conditions previously considered in the literature are shown to be incompatible with the variation principle. We then consi...
Bianchi-IX string cosmological model in Lyra geometry
Indian Academy of Sciences (India)
F Rahaman; S Chakraborty; N Begum; M Hossain; M Kalam
2003-06-01
A class of cosmological solutions of massive strings for the Bianchi-IX space-time are obtained within the framework of Lyra geometry. Various physical and kinematical properties of the models are discussed.
A light Z′ heterotic-string derived model
Directory of Open Access Journals (Sweden)
Alon E. Faraggi
2015-06-01
Full Text Available The existence of an extra Z′ inspired from heterotic-string theory at accessible energy scales attracted considerable interest in the particle physics literature. Surprisingly, however, the construction of heterotic-string derived models that allow for an extra Z′ to remain unbroken down to low scales has proven to be very difficult. The main reason being that the U(1 symmetries that are typically discussed in the literature are either anomalous or have to be broken at a high scale to generate light neutrino masses. In this paper we use for that purpose the self-duality property under the spinor vector duality, which was discovered in free fermionic heterotic string models. The chiral massless states in the self-dual models fill complete 27 representations of E6. The anomaly free gauge symmetry in the effective low energy field theory of our string model is SU(4C×SU(2L×SU(2R×U(1ζ, where U(1ζ is the family universal U(1 symmetry that descends from E6, and is typically anomalous in other free fermionic heterotic-string models. Our model therefore allows for the existence of a low scale Z′, which is a combination of B−L, U(1ζ and T3R. The string model is free of exotic fractionally charged states in the massless spectrum. It contains exotic SO(10 singlet states that carry fractional, non-E6 charge, with respect to U(1ζ. These non-E6 string states arise in the model due to the breaking of the E6 symmetry by discrete Wilson lines. They represent a distinct signature of the string vacua. They may provide viable dark matter candidates.
Institute of Scientific and Technical Information of China (English)
Zhang Jin-Lu; Wang Li-Na; Zhao Xing-Yu; Zhang Li-Li; Zhou Heng-Wei; Wei Lai; Huang Yi-Neng
2011-01-01
The string model for the glass transition can quantitatively describe the universal α-relaxation in glassformers. The string relaxation equation (SRE) of the model simplifies the well-known Debye and Rouse-Zimm relaxation equations at high and low enough temperatures, respectively. However, its initial condition, necessary to the further model predictions of glassy dynamics, has not been solved. In this paper, the general initial condition of the SRE for stochastically spatially configurative strings is solved exactly based on the obtained special initial condition of the SRE for straight strings in a previous paper (J. L. Zhang et al. 2010 Chin. Phya. B 19, 056403).
String networks in ZN Lotka-Volterra competition models
Avelino, P. P.; Bazeia, D.; Menezes, J.; de Oliveira, B. F.
2014-01-01
In this Letter we give specific examples of ZN Lotka-Volterra competition models leading to the formation of string networks. We show that, in order to promote coexistence, the species may arrange themselves around regions with a high number density of empty sites generated by predator-prey interactions between competing species. These configurations extend into the third dimension giving rise to string networks. We investigate the corresponding dynamics using both stochastic and mean field theory simulations, showing that the coarsening of these string networks follows a scaling law which is analogous to that found in other physical systems in condensed matter and cosmology.
Production mechanisms of charm hadrons in the string model
Norrbin, E; Norrbin, Emanuel; Sjöstrand, Torbjörn
1998-01-01
In the hadroproduction of charm in the context of string fragmentation, the pull of a beam remnant at the other end of a string may give a charm hadron more energy than the perturbatively produced charm quark. The collapse of a low-mass string to a single hadron is the extreme case in this direction, and gives rise to asymmetries between charm and anticharm hadron spectra. We study these phenomena, and develop models that describe the characteristics not only of the charm hadrons but also of the associated event.
String Models for the Heavy Quark-Antiquark Bound States.
Tse, Sze-Man
1988-12-01
The heavy quark-antiquark bound state is examined in the phenomenological string models. Specifically, the Nambu-Goto model and the Polyakov's smooth string model are studied in the large-D limit, D being the number of transverse space-time dimensions. The static potential V(R) is extracted in both models in the large-D limit. In the former case, this amounts to the usual saddle point calculation. In the latter case, the renormalized, physical string tension is expressed in terms of the bare string tension and the extrinsic curvature coupling. A systematic loop expansion of V(R) is developed and carried out explicitly to one loop order, with the two loops result presented without detail. For large separations R, the potential is linear in R with corrections of order 1/R. The coefficient of the 1/R Luscher term has the universal value -piD/24 to any finite order in the loop expansion. For very small separations R, the potential V(R) is also proportional to 1/R with a coefficient twice that of Luscher's term. The corrections are logarithmically small. Polyakov's smooth string model is extended to the finite temperature situation. The temperature dependence of the string tension is investigated in the large-D limit. The effective string tension is calculated to the second order in the loop expansion. At low temperature, it differs from that of the Nambu-Goto model only by terms that fall exponentially with inverse temperature. Comparison of the potential V(R) in the smooth string model with lattice gauge calculation and hadron spectroscopy data yields a consistent result.
Exact solutions to a schematic nuclear quark model and colorless superconductivity
DEFF Research Database (Denmark)
Bohr, Henrik; da Providencia, Joao
2008-01-01
-neutral states have, in general, higher energy than the ground state. A novel BCS-type formalism, which is able to describe exactly color symmetrical BCS states, is used to show that the model admits, but only as excited states, color-neutral superconductivity. Therefore, such a model, with just a pairing force......, is unrealistic as a model for the color-neutral confined phase which prevails at normal nuclear densities. Finally, the paper shows that there exists a color-neutral superconducting phase independently of whether the model is based on the pairing force or a more realistic three-body string force....
Modeling Harpsichord Plucking: The Plectrum and the String
Perng, Jack; Rossing, Thomas; Smith, Julius
2011-11-01
The harpsichord is a plucked string keyboard instrument that was popular during the Renaissance and Baroque music eras. Although it was later replaced by the more expressive piano, it has mounted a comeback due to the early music movement today. A physical model of the harpsichord's plucking mechanism is presented, detailing the plectrum-string interaction which illustrates many aspects of the harpsichord's characteristic sound.
String cosmological models in the Brans-Dicke theory for five-dimensional space-time
Institute of Scientific and Technical Information of China (English)
Koijam Manihar Singh; Kangujam Priyokumar Singh
2012-01-01
Five-dimensional space-time string cosmological models generated by a cloud of strings with particles attached to them are studied in the Brans-Dicke theory.We obtain two types of interesting models by taking up the cases of geometric strings (or Nambu strings) and p-strings (Takabayasi strings),and study their different physical and dynamical properties.The roles of the scalar field in getting different phases,such as the inflationary phase and the string-dominated phase,are discussed.An interesting feature obtained here is that in one of the models there is a "bounce" at a particular instant of its evolution.
Matrix models, topological strings, and supersymmetric gauge theories
Dijkgraaf, Robbert; Vafa, Cumrun
2002-11-01
We show that B-model topological strings on local Calabi-Yau threefolds are large- N duals of matrix models, which in the planar limit naturally give rise to special geometry. These matrix models directly compute F-terms in an associated N=1 supersymmetric gauge theory, obtained by deforming N=2 theories by a superpotential term that can be directly identified with the potential of the matrix model. Moreover by tuning some of the parameters of the geometry in a double scaling limit we recover ( p, q) conformal minimal models coupled to 2d gravity, thereby relating non-critical string theories to type II superstrings on Calabi-Yau backgrounds.
Directory of Open Access Journals (Sweden)
Eger Steffen
2016-04-01
Full Text Available We consider the isolated spelling error correction problem as a specific subproblem of the more general string-to-string translation problem. In this context, we investigate four general string-to-string transformation models that have been suggested in recent years and apply them within the spelling error correction paradigm. In particular, we investigate how a simple ‘k-best decoding plus dictionary lookup’ strategy performs in this context and find that such an approach can significantly outdo baselines such as edit distance, weighted edit distance, and the noisy channel Brill and Moore model to spelling error correction. We also consider elementary combination techniques for our models such as language model weighted majority voting and center string combination. Finally, we consider real-world OCR post-correction for a dataset sampled from medieval Latin texts.
Dense String Networks and the One Scale Model with Friction
Aulakh, Charanjit S; Soni, V; Aulakh, Charanjit S.; Nagasawa, Michiyasu; Soni, Vikram
1999-01-01
We examine the behaviour of string networks with the initial string length densities ($ \\sim T_c^2$) and velocities ($ \\sim 1$) expected on the basis of the Kibble mechanism for string formation during a second order phase transition at $T_c$ in the context of the one scale model with friction. The inclusion of friction and use of the natural initial conditions modifies the current picture of string networks in a basic way.We find that a novel transient regime takes the initially dense and fast network to a sparse (string length density $\\sim T_c^3/M_P$) and slow ($v \\sim (T_c/M_P)^{1/2}$) state in a very short time $\\sim 0.1 t_c$ (where $t_c$ is the time of the phase transition that produces the strings). This allows it to join smoothly on to the well known Kibble Regime which prevails at late times in the friction dominated epoch (with the network scale $L\\sim t^{5/4}$ while the network r.m.s velocity $v \\sim t^{1/4}$) which requires initial conditions of this magnitude. Thus essentially irrespective of str...
Muon anomalous magnetic moment in string inspired extended family models
Kephart, T W
2002-01-01
We propose a standard model minimal extension with two lepton weak SU(2) doublets and a scalar singlet to explain the deviation of the measured anomalous magnetic moment of the muon from the standard model expectation. This scheme can be naturally motivated in string inspired models such as E_6 and AdS/CFT.
Super no-scale models in string theory
Kounnas, Costas
2016-01-01
We consider "super no-scale models" in the framework of the heterotic string, where the N=4,2,1 --> 0 spontaneous breaking of supersymmetry is induced by geometrical fluxes realizing a stringy Scherk-Schwarz perturbative mechanism. Classically, these backgrounds are characterized by a boson/fermion degeneracy at the massless level, even if supersymmetry is broken. At the 1-loop level, the vacuum energy is exponentially suppressed, provided the supersymmetry breaking scale is small, m_{3/2} << M_{string}. We show that the "super no-scale string models" under consideration are free of Hagedorn-like tachyonic singularities, even when the supersymmetry breaking scale is large, m_{3/2} ~ M_{string}. The vacuum energy decreases monotonically and converges exponentially to zero, when m_{3/2} varies from M_{string} to 0. We also show that all Wilson lines associated to asymptotically free gauge symmetries are dynamically stabilized by the 1-loop effective potential, while those corresponding to non-asymtoticall...
Abelian Cosmic String in the Starobinsky model of gravity
Graça, J P Morais
2015-01-01
In this paper, I analyze numerically the behaviour of the solutions corresponding to an Abelian string in the framework of the Starobinsky model. The role played by the quadratic term in the Lagrangian density $f(R) = R + \\eta R^2$ of this model is emphasized and the results are compared with the corresponding ones obtained in the framework of Einstein's theory of gravity. I have found that the angular deficit generated by the string is lowered as the $\\eta$ parameter increases, allowing a well-behaved spacetime for a large range of values of the symmetry-breaking scale.
String networks in generalized May-Leonard models
Avelino, P P; Menezes, J; de Oliveira, B F
2013-01-01
Generalized May-Leonard models have proven to be a powerful tool in the study of the dynamics complex biological and ecological systems. In this letter we give specific examples of models leading to the formation of string networks. We show that, in order to promote coexistence, the species may arrange themselves around regions with a high number density of empty sites generated by predator-prey interactions between competing species. These configurations extend into the third dimension giving rise to string networks. We investigate the corresponding dynamics using both stochastic and mean field theory simulations, showing that the coarsening of these string networks follows a scaling law which is analogous to that found in other physical systems in condensed matter and cosmology.
Models in theory building: the case of early string theory
Energy Technology Data Exchange (ETDEWEB)
Castellani, Elena [Department of Philosophy, Florence (Italy)
2013-07-01
The history of the origins and first steps of string theory, from Veneziano's formulation of his famous scattering amplitude in 1968 to the 'first string revolution' in 1984, provides rich material for discussing traditional issues in the philosophy of science. This paper focusses on the initial phase of this history, that is the making of early string theory out of the 'dual theory of strong interactions' motivated by the aim of finding a viable theory of hadrons in the framework of the so-called S-matrix theory of the Sixties: from the first two models proposed (the Dual Resonance Model and the Shapiro-Virasoro Model) to all the subsequent endeavours to extend and complete the theory, including its string interpretation. As is the aim of this paper to show, by representing an exemplary illustration of the building of a scientific theory out of tentative and partial models this is a particularly fruitful case study for the current philosophical discussion on how to characterize a scientific model, a scientific theory, and the relation between models and theories.
String Cosmological Models in Five-Dimensional Spacetimes
Institute of Scientific and Technical Information of China (English)
Sanjay Oli
2009-01-01
We present some classes of solutions for dust matter coupled to the string cloud in five-dimensional Kaluza-Klein spacetimes. The solutions have one or two distinct singularities depending upon the sign of the constant of integration. Some of the classes of models exhibit inflation in the initial stage. The behaviour of associated parameters has been discussed in detail.
Numerical Study of the Simplest String Bit Model
Chen, Gaoli
2016-01-01
String bit models provide a possible method to formulate string as a discrete chain of point-like string bits. When the bit number $M$ is large, a chain behaves as a continuous string. We study the simplest case that has only one bosonic bit and one fermionic bit. The creation and annihilation operators are adjoint representations of $U\\left(N\\right)$ color group. We show that the supersymmetry reduces the parameter number of a Hamiltonian from seven to three and, at $N=\\infty$, ensures continuous energy spectrum, which implies the emergence of one spatial dimension. The Hamiltonian $H_{0}$ is constructed so that in large $N$ limit it produces a worldsheet spectrum with one grassmann worldsheet field. We concentrate on numerical study of the model in finite $N$. For the Hamiltonian $H_{0}$, we find that the would-be ground energy states disappear at $N=\\left(M-1\\right)/2$ for odd $M\\leq11$. Such a simple pattern is spoiled if $H$ has an additional term $\\xi\\Delta H$ which does not affect the result of $N=\\inf...
String-like dual models for scalar theories
Baadsgaard, Christian; Bjerrum-Bohr, N. E. J.; Bourjaily, Jacob; Damgaard, Poul H.
2016-12-01
We show that all tree-level amplitudes in φ p scalar field theory can be represented as the α ' → 0 limit of an SL(2, ℝ)-invariant, string-theory-like dual model integral. These dual models are constructed according to constraints that admit families of solutions. We derive these dual models, and give closed formulae for all tree-level amplitudes of any φ p scalar field theory.
Dynamics in Nonlocal Cosmological Models Derived from String Field Theory
Joukovskaya, Liudmila
2007-01-01
A general class of nonlocal cosmological models is considered. A new method for solving nonlocal Friedmann equations is proposed, and solutions of the Friedmann equations with nonlocal operator are presented. The cosmological properties of these solutions are discussed. Especially indicated is $p$-adic cosmological model in which we have obtained nonsingular bouncing solution and string field theory tachyon model in which we have obtained full solution of nonlocal Friedmann equations with $w=...
String-Like Dual Models for Scalar Theories
Baadsgaard, Christian; Bourjaily, Jacob L; Damgaard, Poul H
2016-01-01
We show that all tree-level amplitudes in $\\varphi^p$ scalar field theory can be represented as the $\\alpha'\\to0$ limit of an $SL(2,R)$-invariant, string-theory-like dual model integral. These dual models are constructed according to constraints that admit families of solutions. We derive these dual models, and give closed formulae for all tree-level amplitudes of any $\\varphi^p$ scalar field theory.
Matrix Models, Topological Strings, and Supersymmetric Gauge Theories
Dijkgraaf, R; Dijkgraaf, Robbert; Vafa, Cumrun
2002-01-01
We show that B-model topological strings on local Calabi-Yau threefolds are large N duals of matrix models, which in the planar limit naturally give rise to special geometry. These matrix models directly compute F-terms in an associated N=1 supersymmetric gauge theory, obtained by deforming N=2 theories by a superpotential term that can be directly identified with the potential of the matrix model. Moreover by tuning some of the parameters of the geometry in a double scaling limit we recover (p,q) conformal minimal models coupled to 2d gravity, thereby relating non-critical string theories to type II superstrings on Calabi-Yau backgrounds.
Matrix models, topological strings, and supersymmetric gauge theories
Energy Technology Data Exchange (ETDEWEB)
Dijkgraaf, Robbert E-mail: rhd@science.uva.nl; Vafa, Cumrun
2002-11-11
We show that B-model topological strings on local Calabi-Yau threefolds are large-N duals of matrix models, which in the planar limit naturally give rise to special geometry. These matrix models directly compute F-terms in an associated N=1 supersymmetric gauge theory, obtained by deforming N=2 theories by a superpotential term that can be directly identified with the potential of the matrix model. Moreover by tuning some of the parameters of the geometry in a double scaling limit we recover (p,q) conformal minimal models coupled to 2d gravity, thereby relating non-critical string theories to type II superstrings on Calabi-Yau backgrounds.
Bianchi type-V string cosmological models in general relativity
Indian Academy of Sciences (India)
Anil Kumar Yadav; Vineet Kumar Yadav; Lallan Yadav
2011-04-01
Bianchi type-V string cosmological models in general relativity are investigated. To get the exact solution of Einstein’s ﬁeld equations, we have taken some scale transformations used by Camci et al [Astrophys. Space Sci. 275, 391 (2001)]. It is shown that Einstein’s ﬁeld equations are solvable for any arbitrary cosmic scale function. Solutions for particular forms of cosmic scale functions are also obtained. Some physical and geometrical aspects of the models are discussed.
Nielsen, Holger B
2014-01-01
Bosonic string theory with the possibility for an arbitrary number of strings - i.e. a string ?eld theory - is formulated by a Hilbert space (a Fock space), which is just that for massless noninteracting scalars. We earlier presented this novel type of string ?eld theory, but now we show that it leads to scattering just given by the Veneziano model amplitude. Generalization to strings with fermion modes would presumably be rather easy. It is characteristic for our formulation /model that: 1) We have thrown away some null set of information compared to usual string ?eld theory, 2)Formulated in terms of our \\objects" (= the non-interacting scalars) there is no interaction and essentially no time development(Heisenberg picture), 3) so that the S-matrix is in our Hilbert space given as the unit matrix, S=1, and 4) the Veneziano scattering amplitude appear as the overlap between the initial and the ?nal state described in terms of the \\objects". 5) The integration in the Euler beta function making up the Veneziano...
Galactic dynamo seeds from non-superconducting spin-polarised strings
de Andrade, L C Garcia
2014-01-01
Earlier Enqvist and Olesen have shown that formation of ferromagnetic planar walls in vacuum at GUT scales in comoving plasmas may generate a large scale magnetic field of $B_{now}\\simeq{10^{-14}G}$. In this paper we show that starting from classical Einstein-Cartan-Maxwell strong gravity, a spin-polarised ferromagnetic cylinder gives rise to a cosmological magnetic field of the order $B_{now}\\simeq{10^{-22}G}$. Vorticity of cylinder is used to obtain galactic magnetic fields. Magnetic fields up to $B\\sim{10^{9}G}$ can be obtained from the spin density of the cylinder. If matching conditions are used cosmological magnetic fields of the order of $B\\sim{10^{-16}R\\frac{Gauss}{cm}}$ where $R$ is the radius of the cosmic strings. For a cosmic string with the radius of an hydrogen atom the cosmic magnetic field is $B\\sim{10^{-32}Gauss}$ which is enough to seed galactic dynamos.
Gauge and Matter Condensates in Realistic String Models
Kalara, S; Pages, D N
1992-01-01
We examine the inter-relationship of the superpotential containing hidden and observable matter fields and the ensuing condensates in free fermionic string models. These gauge and matter condensates of the strongly interacting hidden gauge groups play a crucial role in the determination of the physical parameters of the observable sector. Supplementing the above information with the requirement of modular invariance, we find that a generic model with only trilinear superpotential allows for a degenerate (and sometimes pathological) set of vacua. This degeneracy may be lifted by higher order terms in the superpotential. We also point out some other subtle points that may arise in calculations of this nature. We exemplify our observations by computing explicitly the modular invariant gaugino and matter condensates in the flipped $SU(5)$ string model with hidden gauge group $SO(10)\\times SU(4)$.
On the nonlinear models of the vibrating string
Watzky, Alexandre
2005-09-01
Vibrations of strings (threads, wires, cables...) are of great interest because of their various domains of application. In musical acoustics, phenomena which could have been neglected elsewhere take a particular importance since perception, which is very sensitive to nonlinear effects, is involved. Some phenomena can also be emphasized when a string is coupled to a sound-radiating structure. Reliable physical models are thus necessary to account for these phenomena, and to understand the true behavior of a vibrating string. Despite the fact that the first nonlinear models were published more than one century ago, and that accurate equations of motion can be naturally achieved within a finite displacement continuum mechanics framework, general models never received the attention they deserved, most authors focusing on particular phenomena and often settling on approximate models. This can be explained by the awkward multiplicity of the involved phenomena. The aim of this presentation is to discuss the consequences of some common assumptions and the true nature of some observed couplings. Particular attention will be paid to the preponderance of the spatial shape of the modes, which are usually underestimated with respect to their temporal form.
Stability of string defects in models of non-Abelian symmetry breaking
Thatcher, M J
1999-01-01
In this paper we describe a new type of topological defect, called a homilia string, which is stabilized via interactions with the string network. Using analytical and numerical techniques, we investigate the stability and dynamics of homilia strings, and their implications for cosmology. In SU(N) models of symmetry breaking, monopoles are identified with the intersection of two homilia strings. Due to repulsive forces, the homilia strings seperate, resulting in monopole annihilation. Homilia string loops cannot stabilize as vortons, which circumvents the adverse cosmological consequences of stable loops. In principle, measurments of the cosmic microwave background can distinguish between the smaller fluctuations induced by a homilia string network and those due to primordial cosmic strings.
Model of an LHC superconducting quadrupole magnet
Laurent Guiraud
2000-01-01
Model of a superconducting quadrupole magnet for the LHC project. These magnets are used to focus the beam by squeezing it into a smaller cross-section, a similar effect to a lens focusing light. However, each magnet only focuses the beam in one direction so alternating magnet arrangements are required to produce a fully focused beam.
Dilaton Stabilization in Three-generation Heterotic String Model
Beye, Florian; Kuwakino, Shogo
2016-01-01
We study dilaton stabilization in heterotic string models. By utilizing the asymmetric orbifold construction, we construct an explicit three-generation model whose matter content in the visible sector is the supersymmetric standard model with additional vectorlike matter. This model does not contain any geometric moduli fields except the dilaton field. Model building at a symmetry enhancement point in moduli space enlarges the rank of the hidden gauge group. By analyzing multiple hidden gauge sectors, the dilaton field is stabilized by the racetrack mechanism. We also discuss a supersymmetry breaking scenario and F-term uplifting.
Dilaton stabilization in three-generation heterotic string model
Directory of Open Access Journals (Sweden)
Florian Beye
2016-09-01
Full Text Available We study dilaton stabilization in heterotic string models. By utilizing the asymmetric orbifold construction, we construct an explicit three-generation model whose matter content in the visible sector is the supersymmetric standard model with additional vectorlike matter. This model does not contain any geometric moduli fields except the dilaton field. Model building at a symmetry enhancement point in moduli space enlarges the rank of the hidden gauge group. By analyzing multiple hidden gauge sectors, the dilaton field is stabilized by the racetrack mechanism. We also discuss a supersymmetry breaking scenario and F-term uplifting.
Dilaton stabilization in three-generation heterotic string model
Beye, Florian; Kobayashi, Tatsuo; Kuwakino, Shogo
2016-09-01
We study dilaton stabilization in heterotic string models. By utilizing the asymmetric orbifold construction, we construct an explicit three-generation model whose matter content in the visible sector is the supersymmetric standard model with additional vectorlike matter. This model does not contain any geometric moduli fields except the dilaton field. Model building at a symmetry enhancement point in moduli space enlarges the rank of the hidden gauge group. By analyzing multiple hidden gauge sectors, the dilaton field is stabilized by the racetrack mechanism. We also discuss a supersymmetry breaking scenario and F-term uplifting.
D-term Spectroscopy in Realistic Heterotic-String Models
Dedes, Athanasios
2000-01-01
The emergence of free fermionic string models with solely the MSSM charged spectrum below the string scale provides further evidence to the assertion that the true string vacuum is connected to the Z_2 x Z_2 orbifold in the vicinity of the free fermionic point in the Narain moduli space. An important property of the Z_2 x Z_2 orbifold is the cyclic permutation symmetry between the three twisted sectors. If preserved in the three generations models the cyclic permutation symmetry results in a family universal anomalous U(1)_A, which is instrumental in explaining squark degeneracy, provided that the dominant component of supersymmetry breaking arises from the U(1)_A D-term. Interestingly, the contribution of the family--universal D_A-term to the squark masses may be intra-family non-universal, and may differ from the usual (universal) boundary conditions assumed in the MSSM. We contemplate how D_A--term spectroscopy may be instrumental in studying superstring models irrespective of our ignorance of the details ...
Non Self-conjugate Strings, Singular Strings and Rigged Configurations in the Heisenberg Model
Deguchi, Tetsuo
2014-01-01
It is observed that there exists a different kind of string solutions in the isotropic Heisenberg spin 1/2 chain starting from $N=12$, where the central rapidity of the odd strings become complex making the strings non self conjugate individually. We show that there are at most (N-2)/2 singular highest weight solutions for M=4, M=5, and for N\\geq 2M and at most (N^2-6N+8)/8 singular solutions for M=6 , M=7 and for N\\geq 2M in an even length chain. Correspondence of the non self conjugate string as well as singular string solutions with the Rigged configurations is also discussed.
A matrix model for Misner universe and closed string tachyons
She, Jian-Huang
2006-01-01
We use D-instantons to probe the geometry of Misner universe, and calculate the world volume field theory action, which is of the 1+0 dimensional form and highly non-local. Turning on closed string tachyons, we see from the deformed moduli space of the D-instantons that the spacelike singularity is removed and the region near the singularity becomes a fuzzy cone, where space and time do not commute. When realized cosmologically there can be controllable trans-planckian effects. And the infinite past is now causally connected with the infinite future, thus also providing a model for big crunch/big bang transition. In the spirit of IKKT matrix theory, we propose that the D-instanton action here provides a holographic description for Misner universe and time is generated dynamically. In addition we show that winding string production from the vacua and instability of D-branes have simple uniform interpretations in this second quantized formalism.
Abelian cosmic string in the extended Starobinsky model of gravity
Graça, J P Morais
2016-01-01
We analyze numerically the behaviour of the solutions corresponding to an Abelian cosmic string taking into account an extension of the Starobinsky model, where the action of general relativity is replaced by $f(R) = R - 2\\Lambda + \\eta R^2 + \\rho R^m$, with $m > 2$. As an interesting result, we find that the angular deficit which characterizes the cosmic string decreases as the parameters $\\eta$ and $\\rho$ increase. We also find that the cosmic horizon due to the presence of a cosmological constant is affected in such a way that it can grows or shrinks, depending on the vacuum expectation value of the scalar field and on the value of the cosmological constant
A Model of Graceful Exit in String Cosmology
Brustein, Ram; Brustein, Ram; Madden, Richard
1998-01-01
We construct, for the first time, a model of graceful exit transition from a dilaton-driven inflationary phase to a decelerated Friedman-Robertson-Walker era. Exploiting a demonstration that classical corrections can stabilize a high curvature string phase while the evolution is still in the weakly coupled regime, we show that if additional terms of the type that may result from quantum corrections to the string effective action exist, and induce violation of the null energy condition, then evolution towards a decelerated Friedman-Robertson-Walker phase is possible. We also observe that stabilizing the dilaton at a fixed value, either by capture in a potential minimum or by radiation production, may require that these quantum corrections are turned off, perhaps by non-perturbative effects or higher order contributions which overturn the null energy condition violation.
A matrix model for Misner universe and closed string tachyons
Energy Technology Data Exchange (ETDEWEB)
She Jianhuang [Institute of Theoretical Physics, Chinese Academy of Science, P.O.Box 2735, Beijing 100080 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100080 (China)
2006-01-15
We use D-instantons to probe the geometry of Misner universe, and calculate the world volume field theory action, which is of the 1+0 dimensional form and highly non-local. Turning on closed string tachyons, we see from the deformed moduli space of the D-instantons that the spacelike singularity is removed and the region near the singularity becomes a fuzzy cone, where space and time do not commute. When realized cosmologically there can be controllable trans-planckian effects. And the infinite past is now causally connected with the infinite future, thus also providing a model for big crunch/big bang transition. In the spirit of IKKT matrix theory, we propose that the D-instanton action here provides a holographic description for Misner universe and time is generated dynamically. In addition we show that winding string production from the vacua and instability of D-branes have simple uniform interpretations in this second quantized formalism.
Variable Tension, Large Deflection Ideal String Model For Transverse Motions
Ciblak, Namik
2013-01-01
In this study a new approach to the problem of transverse vibrations of an ideal string is presented. Unlike previous studies, assumptions such as constant tension, inextensibility, constant crosssectional area, small deformations and slopes are all removed. The main result is that, despite such relaxations in the model, not only does the final equation remain linear, but, it is exactly the same equation obtained in classical treatments. First, an "infinitesimals" based analysis, similar to historical methods, is given. However, an alternative and much stronger approach, solely based on finite quantities, is also presented. Furthermore, it is shown that the same result can also be obtained by Lagrangian mechanics, which indicates the compatibility of the original method with those based on energy and variational principles. Another interesting result is the relation between the force distribution and string displacement in static cases, which states that the force distribution per length is proportional to th...
Model of Polyakov duality: String field theory Hamiltonians from Yang-Mills theories
Periwal, Vipul
2000-08-01
Polyakov has conjectured that Yang-Mills theory should be equivalent to a noncritical string theory. I point out, based on the work of Marchesini, Ishibashi, Kawai and collaborators, and Jevicki and Rodrigues, that the loop operator of the Yang-Mills theory is the temporal gauge string field theory Hamiltonian of a noncritical string theory. The consistency condition of the string interpretation is the zig-zag symmetry emphasized by Polyakov. I explicitly show how this works for the one-plaquette model, providing a consistent direct string interpretation of the unitary matrix model for the first time.
Bianchi Type Ⅲ String Cosmological Model with Bulk Viscosity
Institute of Scientific and Technical Information of China (English)
WANGXing-Xiang
2004-01-01
The Bianchi type Ⅲ cosmological model for a cloud string with bulk viscosity are presented. To obtain a determinate model, an equation of state ρ=kλ and a relation between metric potentials B = Cn are assumed. The physical and geometric aspects of the model are also discussed. The model describes a shearing non-rotating continuously expanding universe with a big-bang start, and the relation between the coefficient of bulk viscosity and the energy density is ζ∝ρ1/2.
Bianchi Type Ⅲ String Cosmological Model with Bulk Viscosity
Institute of Scientific and Technical Information of China (English)
WANG Xing-Xiang
2004-01-01
The Bianchi type Ⅲ cosmological model for a cloud string with bulk viscosity are presented. To obtaina determinate model, an equation of state p = κλ and a relation between metric potentials B = Cn are assumed. Thephysical and geometric aspects of the model are also discussed. The model describes a shearing non-rotating continuouslyexpanding universe with a big-bang start, and the relation between the coefficient of bulk viscosity and the energy densityis ζ∝1 p1/2.
Phenomenological Hints from a Class of String Motivated Model Constructions
Directory of Open Access Journals (Sweden)
Hans Peter Nilles
2015-01-01
Full Text Available We use string theory constructions towards the generalisation of the supersymmetric standard model of strong and electroweak interactions. Properties of the models depend crucially on the location of fields in extradimensional compact space. This allows us to extract some generic lessons for the phenomenological properties of the low energy effective action. Within this scheme we present a compelling model based on local grand unification and mirage mediation of supersymmetry breakdown. We analyse the properties of the specific model towards its possible tests at the LHC and the complementarity to direct dark matter searches.
Thermo-hydraulic Quench Propagation at the LHC Superconducting Magnet String
Rodríguez-Mateos, F; Serio, L
1998-01-01
The superconducting magnets of the LHC are protected by heaters and cold by-pass diodes. If a magnet quenches, the heaters on this magnet are fired and the magnet chain is de-excited in about two minu tes by opening dump switches in parallel to a resistor. During the time required for the discharge, adjacent magnets might quench due to thermo-hydraulic propagation in the helium bath and/or heat con duction via the bus bar. The number of quenching magnets depends on the mechanisms for the propagation. In this paper we report on quench propagation experiments from a dipole magnet to an adjacent ma gnet. The mechanism for the propagation is hot helium gas expelled from the first quenching magnet. The propagation changes with the pressure opening settings of the quench relief valves.
Poole, Charles P; Farach, Horacio A
1995-01-01
Superconductivity covers the nature of the phenomenon of superconductivity. The book discusses the fundamental principles of superconductivity; the essential features of the superconducting state-the phenomena of zero resistance and perfect diamagnetism; and the properties of the various classes of superconductors, including the organics, the buckministerfullerenes, and the precursors to the cuprates. The text also describes superconductivity from the viewpoint of thermodynamics and provides expressions for the free energy; the Ginzburg-Landau and BCS theories; and the structures of the high
Detectability of the second resonance of low-scale string models at the LHC
Hashi, Manami
2012-01-01
Low-scale string models are phenomenological models in String Theory, in which the string scale M_s is of the order of TeV. String excited states which are characteristic modes in low-scale string models can be observed as resonances in dijet invariant mass distributions at the LHC. If a new heavy resonance is discovered at the LHC, it is important to investigate whether the resonance comes from low-scale string models. In this work, two analyses are performed: One is observing higher spin degeneracy of string excited states by an angular distribution analysis on the resonance, since the string resonance consists of several degenerate states with different spins. The other is observing second string excited states by a search for a second resonance in dijet invariant mass distributions, since second string excited states have characteristic masses of sqrt{2} times of masses of first string excited states. As the result of Monte Carlo simulations assuming the 14 TeV LHC, we give required luminosities for 5 sig...
Non self-conjugate strings, singular strings and rigged configurations in the Heisenberg model
Deguchi, Tetsuo; Ranjan Giri, Pulak
2015-02-01
We observe a different type of complex solutions in the isotropic spin-1/2 Heisenberg chain starting from N = 12, where the central rapidity of some of the odd-length strings becomes complex so that not all the strings self-conjugate individually. We show that there are at most (N - 2)/2 singular solutions for M = 4, M = 5 down-spins and at most (N2 - 6N + 8)/8 singular solutions for M = 6, M = 7 down-spins in an even-length chain with N ⩾ 2M. Correspondence of the non self-conjugate string solutions and the singular string solutions to the rigged configurations has also been shown.
With string model to time series forecasting
Pinčák, Richard; Bartoš, Erik
2015-01-01
Overwhelming majority of econometric models applied on a long term basis in the financial forex market do not work sufficiently well. The reason is that transaction costs and arbitrage opportunity are not included, as this does not simulate the real financial markets. Analyses are not conducted on the non equidistant date but rather on the aggregate date, which is also not a real financial case. In this paper, we would like to show a new way how to analyze and, moreover, forecast financial ma...
From topological strings to minimal models
Energy Technology Data Exchange (ETDEWEB)
Foda, Omar [School of Mathematics and Statistics, University of Melbourne,Royal Parade, Parkville, VIC 3010 (Australia); Wu, Jian-Feng [Department of Mathematics and Statistics, Henan University,Minglun Street, Kaifeng city, Henan (China); Beijing Institute of Theoretical Physics and Mathematics,3rd Shangdi Street, Beijing (China)
2015-07-24
We glue four refined topological vertices to obtain the building block of 5D U(2) quiver instanton partition functions. We take the 4D limit of the result to obtain the building block of 4D instanton partition functions which, using the AGT correspondence, are identified with Virasoro conformal blocks. We show that there is a choice of the parameters of the topological vertices that we start with, as well as the parameters and the intermediate states involved in the gluing procedure, such that we obtain Virasoro minimal model conformal blocks.
Perturbation theory for string sigma models
Bianchi, Lorenzo
2016-01-01
In this thesis we investigate quantum aspects of the Green-Schwarz superstring in various AdS backgrounds relevant for the AdS/CFT correspondence, providing several examples of perturbative computations in the corresponding integrable sigma-models. We start by reviewing in details the supercoset construction of the superstring action in $AdS_5 \\times S^5$, pointing out the limits of this procedure for $AdS_4$ and $AdS_3$ backgrounds. For the $AdS_4 \\times CP^3$ case we give a thorough derivation of an alternative action, based on the double-dimensional reduction of eleven-dimensional super-membranes. We then consider the expansion about the BMN vacuum and the S-matrix for the scattering of worldsheet excitations in the decompactification limit. To evaluate its elements efficiently we describe a unitarity-based method resulting in a very compact formula yielding the cut-constructible part of any one-loop two-dimensional S-matrix. In the second part of this review we analyze the superstring action on $AdS_4 \\ti...
From topological strings to minimal models
Foda, Omar
2015-01-01
We glue four refined topological vertices to obtain a $U(2)$ web partition function $\\mathcal{W}_{\\, \\bf V \\, W \\, \\Delta} [q, t, R]$, where ${\\bf V}$ and ${\\bf W}$ are two pairs of Young diagrams, ${\\bf \\Delta}$ is a set of K\\"ahler parameters, $q$ and $t$ are deformation parameters, and $R$ is the radius of the $M$-theory circle. We show that there is 1. a choice of ${\\bf \\Delta}$, $q$ and $t$ as functions of $R$ and two co-prime integers $p$ and $p^{\\prime}$ , and 2. a restriction of ${\\bf V}$ and ${\\bf W}$ to partition pairs that obey $p$- and $p^{\\prime}$-dependent conditions, such that we obtain a restricted version of $\\mathcal{W}_{\\, \\bf V \\, W \\, \\Delta} [q, t, R]$ that 1. is manifestly free of non-physical singularities, and 2. reduces in the $R \\! \\rightarrow \\! 0$ limit to a building block of restricted versions of the 4D $U(2)$ quiver instanton partition functions. The latter are equal, using the AGT correspondence, to conformal blocks of Virasoro $A$-series minimal models parameterised by $p$ an...
SUSY Breaking in Local String/F-Theory Models
Blumenhagen, R; Krippendorf, S; Moster, S; Quevedo, F
2009-01-01
We investigate bulk moduli stabilisation and supersymmetry breaking in local string/F-theory models where the Standard Model is supported on a del Pezzo surface or singularity. Computing the gravity mediated soft terms on the Standard Model brane induced by bulk supersymmetry breaking in the LARGE volume scenario, we explicitly find suppressions by M_s/M_P ~ V^{-1/2} compared to M_{3/2}. This gives rise to several phenomenological scenarios, depending on the strength of perturbative corrections to the effective action and the source of de Sitter lifting, in which the soft terms are suppressed by at least M_P/V^{3/2} and may be as small as M_P/V^2. Since the gravitino mass is of order M_{3/2} ~ M_P/V, for TeV soft terms all these scenarios give a very heavy gravitino (M_{3/2} >= 10^8 GeV) and generically the lightest moduli field is also heavy enough (m >= 10 TeV) to avoid the cosmological moduli problem. For TeV soft terms, these scenarios predict a minimal value of the volume to be V ~ 10^{6-7} in string uni...
Super no-scale models in string theory
Kounnas, Costas; Partouche, Hervé
2016-12-01
We consider "super no-scale models" in the framework of the heterotic string, where the N = 4 , 2 , 1 → 0 spontaneous breaking of supersymmetry is induced by geometrical fluxes realizing a stringy Scherk-Schwarz perturbative mechanism. Classically, these backgrounds are characterized by a boson/fermion degeneracy at the massless level, even if supersymmetry is broken. At the 1-loop level, the vacuum energy is exponentially suppressed, provided the supersymmetry breaking scale is small, m3/2 ≪Mstring. We show that the "super no-scale string models" under consideration are free of Hagedorn-like tachyonic singularities, even when the supersymmetry breaking scale is large, m3/2 ≃Mstring. The vacuum energy decreases monotonically and converges exponentially to zero, when m3/2 varies from Mstring to 0. We also show that all Wilson lines associated to asymptotically free gauge symmetries are dynamically stabilized by the 1-loop effective potential, while those corresponding to non-asymptotically free gauge groups lead to instabilities and condense. The Wilson lines of the conformal gauge symmetries remain massless. When stable, the stringy super no-scale models admit low energy effective actions, where decoupling gravity yields theories in flat spacetime, with softly broken supersymmetry.
Thomas, D B
1974-01-01
A short general review is presented of the progress made in applied superconductivity as a result of work performed in connection with the high-energy physics program in Europe. The phenomenon of superconductivity and properties of superconductors of Types I and II are outlined. The main body of the paper deals with the development of niobium-titanium superconducting magnets and of radio-frequency superconducting cavities and accelerating structures. Examples of applications in and for high-energy physics experiments are given, including the large superconducting magnet for the Big European Bubble Chamber, prototype synchrotron magnets for the Super Proton Synchrotron, superconducting d.c. beam line magnets, and superconducting RF cavities for use in various laboratories. (0 refs).
Sequestered String Models: Supersymmetry Breaking and Cosmological Applications
Muia, Francesco
2016-01-01
In the present thesis I studied the phenomenology arising from a class of string models called sequestered compactifications, which were born with the aim of getting low-energy SUSY from strings. This is not an easy task if combined with cosmological constraints, since the mechanism of moduli stabilization fixes both the scale of supersymmetric particles and the scale of moduli, which tend to be of the same order. However, if on the one hand supersymmetric particles with TeV mass are desired in order to address the hierarchy problem, on the other hand the cosmological moduli problem requires the moduli to be heavier than 100 TeV. The specific setup of sequestered compactifications makes this hierarchy achievable, at least in principle: as in these models the visible sector is located on a stack of D3-branes at singularities, a physical separation between the visible degrees of freedom and the SUSY-breaking sources takes place. Such decoupling translates into a hierarchy between the scale of SUSY-breaking and ...
Resolution of overlapping ambiguity strings based on maximum entropy model
Institute of Scientific and Technical Information of China (English)
ZHANG Feng; FAN Xiao-zhong
2006-01-01
The resolution of overlapping ambiguity strings (OAS) is studied based on the maximum entropy model.There are two model outputs,where either the first two characters form a word or the last two characters form a word.The features of the model include one word in context of OAS,the current OAS and word probability relation of two kinds of segmentation results.OAS in training text is found by the combination of the FMM and BMM segmentation method.After feature tagging they are used to train the maximum entropy model.The People Daily corpus of January 1998 is used in training and testing.Experimental results show a closed test precision of 98.64% and an open test precision of 95.01%.The open test precision is 3,76% better compared with that of the precision of common word probability method.
Supersymmetric standard model from the heterotic string (II)
Energy Technology Data Exchange (ETDEWEB)
Buchmueller, W. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hamaguchi, K. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Tokyo Univ. (Japan). Dept. of Physics; Lebedev, O.; Ratz, M. [Bonn Univ. (Germany). Physikalisches Inst.
2006-06-15
We describe in detail a Z{sub 6} orbifold compactification of the heterotic E{sub 8} x E{sub 8} string which leads to the (supersymmetric) standard model gauge group and matter content. The quarks and leptons appear as three 16-plets of SO(10), two of which are localized at fixed points with local SO(10) symmetry. The model has supersymmetric vacua without exotics at low energies and is consistent with gauge coupling unification. Supersymmetry can be broken via gaugino condensation in the hidden sector. The model has large vacuum degeneracy. Certain vacua with approximate B-L symmetry have attractive phenomenological features. The top quark Yukawa coupling arises from gauge interactions and is of the order of the gauge couplings. The other Yukawa couplings are suppressed by powers of standard model singlet fields, similarly to the Froggatt-Nielsen mechanism. (Orig.)
Marino Beiras, Marcos
2001-01-01
We give an overview of the relations between matrix models and string theory, focusing on topological string theory and the Dijkgraaf--Vafa correspondence. We discuss applications of this correspondence and its generalizations to supersymmetric gauge theory, enumerative geometry and mirror symmetry. We also present a brief overview of matrix quantum mechanical models in superstring theory.
A numerical study of the string function using a primitive equation ocean model
Tyler, R. H.; Käse, R.
We use results from a primitive-equation ocean numerical model (SCRUM) to test a theoretical 'string function' formulation put forward by Tyler and Käse in another article in this issue. The string function acts as a stream function for the large-scale potential energy flow under the combined beta and topographic effects. The model results verify that large-scale anomalies propagate along the string function contours with a speed correctly given by the cross-string gradient. For anomalies having a scale similar to the Rossby radius, material rates of change in the layer mass following the string velocity are balanced by material rates of change in relative vorticity following the flow velocity. It is shown that large-amplitude anomalies can be generated when wind stress is resonant with the string function configuration.
Energy Technology Data Exchange (ETDEWEB)
Altsybeev, Igor [St. Petersburg State University (Russian Federation)
2016-01-22
In the present work, Monte-Carlo toy model with repulsing quark-gluon strings in hadron-hadron collisions is described. String repulsion creates transverse boosts for the string decay products, giving modifications of observables. As an example, long-range correlations between mean transverse momenta of particles in two observation windows are studied in MC toy simulation of the heavy-ion collisions.
Zörnig, Peter
2015-08-01
We present integer programming models for some variants of the farthest string problem. The number of variables and constraints is substantially less than that of the integer linear programming models known in the literature. Moreover, the solution of the linear programming-relaxation contains only a small proportion of noninteger values, which considerably simplifies the rounding process. Numerical tests have shown excellent results, especially when a small set of long sequences is given.
1989-07-01
SUPERCONDUCTIVITY HIGH-POWER APPLICATIONS Electric power generation/transmission Energy storage Acoustic projectors Weapon launchers Catapult Ship propulsion • • • Stabilized...temperature superconductive shields could be substantially enhanced by use of high-Tc materials. 27 28 NRAC SUPERCONDUCTIVITY SHIP PROPULSION APPLICATIONS...motor shown in the photograph. As a next step in the evolution of electric-drive ship propulsion technology, DTRC has proposed to scale up the design
The Consensus String Problem and the Complexity of Comparing Hidden Markov Models
DEFF Research Database (Denmark)
Lyngsø, Rune Bang; Pedersen, Christian Nørgaard Storm
2002-01-01
The basic theory of hidden Markov models was developed and applied to problems in speech recognition in the late 1960s, and has since then been applied to numerous problems, e.g. biological sequence analysis. Most applications of hidden Markov models are based on efficient algorithms for computing...... the probability of generating a given string, or computing the most likely path generating a given string. In this paper we consider the problem of computing the most likely string, or consensus string, generated by a given model, and its implications on the complexity of comparing hidden Markov models. We show...... that computing the consensus string, and approximating its probability within any constant factor, is NP-hard, and that the same holds for the closely related labeling problem for class hidden Markov models. Furthermore, we establish the NP-hardness of comparing two hidden Markov models under the L∞- and L1...
The Consensus String Problem and the Complexity of Comparing Hidden Markov Models
DEFF Research Database (Denmark)
Lyngsø, Rune Bang; Pedersen, Christian Nørgaard Storm
2002-01-01
The basic theory of hidden Markov models was developed and applied to problems in speech recognition in the late 1960s, and has since then been applied to numerous problems, e.g. biological sequence analysis. Most applications of hidden Markov models are based on efficient algorithms for computing...... the probability of generating a given string, or computing the most likely path generating a given string. In this paper we consider the problem of computing the most likely string, or consensus string, generated by a given model, and its implications on the complexity of comparing hidden Markov models. We show...... that computing the consensus string, and approximating its probability within any constant factor, is NP-hard, and that the same holds for the closely related labeling problem for class hidden Markov models. Furthermore, we establish the NP-hardness of comparing two hidden Markov models under the L∞- and L1...
Detailed string stability analysis for bi-directional optimal velocity model
Institute of Scientific and Technical Information of China (English)
郑亮
2015-01-01
The class of bi-directional optimal velocity models can describe the bi-directional looking effect that usually exists in the reality and is even enhanced with the development of the connected vehicle technologies. Its combined string stability condition can be obtained through the method of the ring-road based string stability analysis. However, the partial string stability about traffic fluctuation propagated backward or forward was neglected, which will be analyzed in detail in this work by the method of transfer function and its H∞norm from the viewpoint of control theory. Then, through comparing the conditions of combined and partial string stabilities, their relationships can make traffic flow be divided into three distinguishable regions, displaying various combined and partial string stability performance. Finally, the numerical experiments verify the theoretical results and find that the final displaying string stability or instability performance results from the accumulated and offset effects of traffic fluctuations propagated from different directions.
Heat string model of bi-dimensional dc Glidarc
Pellerin, S.; Richard, F.; Chapelle, J.; Cormier, J.-M.; Musiol, K.
2000-10-01
The gliding arc discharge (`Glidarc') is the subject of renewed interest in application to a variety of chemical reactions. The gliding arc creates a weakly ionized gas `string' between two horn-shaped electrodes. In this paper, we present a simple model for a bi-dimensional dc Glidarc working in air, in which the conducting zone of the discharge that is heated by the Joule effect is considered as a hot wire cooled by an air flow. Inside this wire, the heat transfer results from thermal conduction. The exchange of heat between the hot wire and the air flow is assured by convection and depends on the wire radius and the relative velocity of the arc with respect to the gas flow. The model correctly describes experimental results and allows us to predict the working parameters of the Glidarc in different experimental situations.
Spinors, strings, integrable models, and decomposed Yang-Mills theory
Ioannidou, Theodora; Jiang, Ying; Niemi, Antti J.
2014-07-01
This paper deals with various interrelations between strings and surfaces in three-dimensional ambient space, two-dimensional integrable models, and two-dimensional and four-dimensional decomposed SU(2) Yang-Mills theories. Initially, a spinor version of the Frenet equation is introduced in order to describe the differential geometry of static three-dimensional stringlike structures. Then its relation to the structure of the su_(2) Lie algebra valued Maurer-Cartan one-form is presented, while by introducing time evolution of the string a Lax pair is obtained, as an integrability condition. In addition, it is shown how the Lax pair of the integrable nonlinear Schrödinger equation becomes embedded into the Lax pair of the time extended spinor Frenet equation, and it is described how a spinor-based projection operator formalism can be used to construct the conserved quantities, in the case of the nonlinear Schrödinger equation. Then the Lax pair structure of the time extended spinor Frenet equation is related to properties of flat connections in a two-dimensional decomposed SU(2) Yang-Mills theory. In addition, the connection between the decomposed Yang-Mills and the Gauß-Codazzi equation that describes surfaces in three-dimensional ambient space is presented. In that context the relation between isothermic surfaces and integrable models is discussed. Finally, the utility of the Cartan approach to differential geometry is considered. In particular, the similarities between the Cartan formalism and the structure of both two-dimensional and four-dimensional decomposed SU(2) Yang-Mills theories are discussed, while the description of two-dimensional integrable models as embedded structures in the four-dimensional decomposed SU(2) Yang-Mills theory are presented.
Affleck-Dine Baryogenesis in Type IIB String Models
Allahverdi, Rouzbeh; Muia, Francesco
2016-01-01
We present a viable string embedding of Affleck-Dine baryogenesis in type IIB sequestered models where the late-time decay of the lightest modulus reheats the universe to relatively low temperatures. We show that if inflation is driven by a blow-up Kaehler modulus, the Affleck-Dine field can become tachyonic during inflation if the Kaehler metric for matter fields has an appropriate inflaton-dependent contribution. We find that the Affleck-Dine mechanism can generate the observed baryon asymmetry for natural values of the underlying parameters which lead also to successful inflation and low-energy gaugino masses in a split supersymmetry scenario. The reheating temperature from the lightest modulus decay is high enough to allow thermal Higgsino-like dark matter.
Affleck-Dine baryogenesis in type IIB string models
Allahverdi, Rouzbeh; Cicoli, Michele; Muia, Francesco
2016-06-01
We propose a possible string embedding of Affleck-Dine baryogenesis in type IIB sequestered models where the late-time decay of the lightest modulus reheats the universe to relatively low temperatures. We show that if inflation is driven by a blow-up Kähler modulus, the Affleck-Dine field can become tachyonic during inflation if the Kähler metric for matter fields has an appropriate inflaton-dependent contribution. We find that the Affleck-Dine mechanism can generate the observed baryon asymmetry for natural values of the underlying parameters which lead also to successful inflation and low-energy gaugino masses in a split supersymmetry scenario. The reheating temperature from the lightest modulus decay is high enough to allow thermal Higgsino-like dark matter.
Discussing string extensions of the Standard Model in D brane world
Di Vecchia, P
2009-01-01
In this talk we will describe the problems that one encounters when one tries to connect string theory with particle phenomenology. Then, in order to have chiral matter describing quarks and leptons, we introduce the magnetized D branes. Finally, as an explicit example of a string extension of the Standard Model, we will describe the one constructed by Ibanez, Marchesano and Rabadan.
Discussing string extensions of the Standard Model in D brane world
Energy Technology Data Exchange (ETDEWEB)
Di Vecchia, Paolo [Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen O (Denmark); NORDITA, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)
2009-01-15
In this talk we will describe the problems that one encounters when one tries to connect string theory with particle phenomenology. Then, in order to have chiral matter describing quarks and leptons, we introduce the magnetized D branes. Finally, as an explicit example of a string extension of the Standard Model, we will describe the one constructed by Ibanez, Marchesano and Rabadan.
Noncommutative-geometry model for closed bosonic strings
Sen, Siddhartha; Holman, R.
1987-01-01
It is shown how Witten's (1986) noncommutative geometry may be extended to describe the closed bosonic string. For closed strings, an explicit representation is provided of the integral operator needed to construct an action and of an associative product on string fields. The proper choice of the action of the integral operator and the associative product in order to give rise to a reasonable theory is explained, and the consequences of such a choice are discussed. It is shown that the ghost numbers of the operator and associative product can be chosen arbitrarily for both open and closed strings, and that this construct can be used as an action for interacting closed bosonic strings.
LRS Bianchi type-II string cosmological models in a modified theory of gravitation
Kanakavalli, T.; Ananda Rao, G.; Reddy, D. R. K.
2017-03-01
This paper is devoted to the investigation of spatially homogeneous anisotropic LRS Bianchi type-II cosmological models with string source in a modified theory of gravitation formulated by Harko et al. (Phys. Rev. D 84:024020, 2011) which is universally known as f( R, T) gravity. Here R is the Ricci scalar and T is the trace of the energy momentum tensor. By solving the field equation we have presented massive string and Takabyasi or p-string models in this theory. However it is interesting to note that geometric string in this space-time does not exist in this theory. Physical and geometrical properties of the strings obtained are also discussed.
Cosmological constraints on superconducting dark energy models
Keresztes, Zoltán; Harko, Tiberiu; Liang, Shi-Dong
2015-01-01
We consider cosmological tests of a scalar-vector-tensor gravitational model, in which the dark energy is included in the total action through a gauge invariant, electromagnetic type contribution. The ground state of dark energy, corresponding to a constant potential $V$ is a Bose-Einstein type condensate with spontaneously broken U(1) symmetry. In another words dark energy appears as a massive vector field emerging from a superposition of a massless vector and a scalar field, the latter corresponding to the Goldstone boson. Two particular cosmological models, corresponding to pure electric and pure magnetic type potentials, respectively are confronted with Type IA Supernovae and Hubble parameter data. In the electric case good fit is obtained along a narrow inclined stripe in the $\\Omega _{m}-\\Omega _{V}$ parameter plane, which includes the $\\Lambda $CDM limit. The other points on this admissible region represent superconducting dark energy as a sum of a cosmological constant and a time-evolving contribution...
Ketterson, John B
2008-01-01
Conceived as the definitive reference in a classic and important field of modern physics, this extensive and comprehensive handbook systematically reviews the basic physics, theory and recent advances in the field of superconductivity. Leading researchers, including Nobel laureates, describe the state-of-the-art in conventional and unconventional superconductors at a particularly opportune time, as new experimental techniques and field-theoretical methods have emerged. In addition to full-coverage of novel materials and underlying mechanisms, the handbook reflects continued intense research into electron-phone based superconductivity. Considerable attention is devoted to high-Tc superconductivity, novel superconductivity, including triplet pairing in the ruthenates, novel superconductors, such as heavy-Fermion metals and organic materials, and also granular superconductors. What’s more, several contributions address superconductors with impurities and nanostructured superconductors. Important new results on...
Integrable Models, SUSY Gauge Theories, and String Theory
Nam, S
1996-01-01
We consider the close relation between duality in N=2 SUSY gauge theories and integrable models. Vario us integrable models ranging from Toda lattices, Calogero models, spinning tops, and spin chains are re lated to the quantum moduli space of vacua of N=2 SUSY gauge theories. In particular, SU(3) gauge t heories with two flavors of massless quarks in the fundamental representation can be related to the spec tral curve of the Goryachev-Chaplygin top, which is a Nahm's equation in disguise. This can be generaliz ed to the cases with massive quarks, and N_f = 0,1,2, where a system with seven dimensional phas e space has the relevant hyperelliptic curve appear in the Painlevé test. To understand the stringy o rigin of the integrability of these theories we obtain exact nonperturbative point particle limit of ty pe II string compactified on a Calabi-Yau manifold, which gives the hyperelliptic curve of SU(2) QCD w ith N_f =1 hypermultiplet.
Superconductivity in the Kondo lattice model
Energy Technology Data Exchange (ETDEWEB)
Bodensiek, Oliver; Pruschke, Thomas [Institute for Theoretical Physics, University of Goettingen, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Zitko, Rok [Institute for Theoretical Physics, University of Goettingen, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia)
2011-07-01
We study the Kondo lattice model with an additional attractive interaction among the conduction-band electrons by means of dynamical mean-field theory in combination with the numerical renormalization group method. In the normal phase we observe a strong dependency of the low-energy scale on the attractive interaction. Thus, there exists a delicate interplay between the attractive interaction and the antiferromagnetic Kondo exchange, which results in a critical interaction, above of which the Fermi surface collapses because the spins become effectively decoupled from the conduction electrons. Additionally, we allow for a s-wave superconducting phase, which appears to be split at the point of the underlying Fermi surface collapse. We discuss the interplay between attractive interaction an Kondo exchange and its pertinence to phonons in heavy fermion physics.
Model dependence of baryon decay enhancement by cosmic strings
Fewster, C J
1993-01-01
Cosmic strings arising from GUTs can catalyse baryon decay processes with strong interaction cross sections. We examine the mechanism by which the cross section is enhanced and find that it depends strongly on the details of the distribution of gauge fields within the string core. We propose a calculational scheme for estimating wavefunction amplification factors and also a physical understanding of the nature of the enhancement process.
Asymptotic freedom in a string model of high temperature QCD
Awada, M
1995-01-01
Recently we have shown that a phase transition occurs in the leading and subleading approximation of the large N limit in rigid strings coupled to long range Kalb-Ramond interactions. The disordered phase is essentially the Nambu-Goto-Polyakov string theory while the ordered phase is a new theory. In this letter we compute the free energy per unit length of the interacting rigid string at finite temperature. We show that the mass of the winding states solves that of QCD strings in the limit of high temperature. We obtain a precise identification of the QCD coupling constant and those of the interacting rigid string. The relation we obtain is Ng_{QCD}^2 = ({8\\pi^2 (D-2)\\over 9})^2{1\\over 3\\kappa} where \\kappa = {D t \\alpha\\over \\pi \\mu_{c}} is the ratio of the extrinsic curvature coupling constant t, the Kalb-Ramond coupling constant \\alpha, and the critical string tension \\mu_{c}. The running beta function of \\kappa reproduces correctly the asymptotic behaviour of QCD.
General analysis of dark radiation in sequestered string models
Energy Technology Data Exchange (ETDEWEB)
Cicoli, Michele [ICTP,Strada Costiera 11, Trieste 34014 (Italy); Dipartimento di Fisica e Astronomia, Università di Bologna,via Irnerio 46, 40126 Bologna (Italy); INFN, Sezione di Bologna,via Irnerio 46, 40126 Bologna (Italy); Muia, Francesco [Dipartimento di Fisica e Astronomia, Università di Bologna,via Irnerio 46, 40126 Bologna (Italy); INFN, Sezione di Bologna,via Irnerio 46, 40126 Bologna (Italy)
2015-12-22
We perform a general analysis of axionic dark radiation produced from the decay of the lightest modulus in the sequestered LARGE Volume Scenario. We discuss several cases depending on the form of the Kähler metric for visible sector matter fields and the mechanism responsible for achieving a de Sitter vacuum. The leading decay channels which determine dark radiation predictions are to hidden sector axions, visible sector Higgses and SUSY scalars depending on their mass. We show that in most of the parameter space of split SUSY-like models squarks and sleptons are heavier than the lightest modulus. Hence dark radiation predictions previously obtained for MSSM-like cases hold more generally also for split SUSY-like cases since the decay channel to SUSY scalars is kinematically forbidden. However the inclusion of string loop corrections to the Kähler potential gives rise to a parameter space region where the decay channel to SUSY scalars opens up, leading to a significant reduction of dark radiation production. In this case, the simplest model with a shift-symmetric Higgs sector can suppress the excess of dark radiation ΔN{sub eff} to values as small as 0.14, in perfect agreement with current experimental bounds. Depending on the exact mass of the SUSY scalars all values in the range 0.14≲ΔN{sub eff}≲1.6 are allowed. Interestingly dark radiation overproduction can be avoided also in the absence of a Giudice-Masiero coupling.
The Simplest, String-Derivable, Supergravity Model and its Experimental Predictions
López, J; Zichichi, A
1994-01-01
We present the simplest, string-derivable, supergravity model and discuss its experimental consequences. This model is a new string-inspired flipped $SU(5)$ which unifies at the string scale $M_U=10^{18}\\GeV$ due to the introduction of an additional pair of \\r{10},\\rb{10} flipped $SU(5)$ representations which contain new intermediate scale `gap' particles. We study various model-building issues which should be addressed in string-derived incarnations of this model. We focus our study on the no-scale supergravity mechanism and explore thoroughly the three-dimensional parameter space of the model ($m_{\\tilde g},m_t,\\tan\\beta$), thus obtaining several simple relationships among the particle masses, such as: $m_{\\tilde q}\\approx m_{\\tilde g}$, $m_{\\tilde e_L}\\approx m_{\\tilde\
Bianchi type-VIh string cloud cosmological models with bulk viscosity
Tripathy, Sunil K.; Behera, Dipanjali
2010-11-01
String cloud cosmological models are studied using spatially homogeneous and anisotropic Bianchi type VIh metric in the frame work of general relativity. The field equations are solved for massive string cloud in presence of bulk viscosity. A general linear equation of state of the cosmic string tension density with the proper energy density of the universe is considered. The physical and kinematical properties of the models have been discussed in detail and the limits of the anisotropic parameter responsible for different phases of the universe are explored.
General Analysis of Dark Radiation in Sequestered String Models
Cicoli, Michele
2015-01-01
We perform a general analysis of axionic dark radiation produced from the decay of the lightest modulus in the sequestered LARGE Volume Scenario. We discuss several cases depending on the form of the Kahler metric for visible sector matter fields and the mechanism responsible for achieving a de Sitter vacuum. The leading decay channels which determine dark radiation predictions are to hidden sector axions, visible sector Higgses and SUSY scalars depending on their mass. We show that in most of the parameter space of split SUSY-like models squarks and sleptons are heavier than the lightest modulus. Hence dark radiation predictions previously obtained for MSSM-like cases hold more generally also for split SUSY-like cases since the decay channel to SUSY scalars is kinematically forbidden. However the inclusion of string loop corrections to the Kahler potential gives rise to a parameter space region where the decay channel to SUSY scalars opens up, leading to a significant reduction of dark radiation production. ...
Poole, Charles P; Creswick, Richard J; Prozorov, Ruslan
2014-01-01
Superconductivity, Third Edition is an encyclopedic treatment of all aspects of the subject, from classic materials to fullerenes. Emphasis is on balanced coverage, with a comprehensive reference list and significant graphics from all areas of the published literature. Widely used theoretical approaches are explained in detail. Topics of special interest include high temperature superconductors, spectroscopy, critical states, transport properties, and tunneling. This book covers the whole field of superconductivity from both the theoretical and the experimental point of view. This third edition features extensive revisions throughout, and new chapters on second critical field and iron based superconductors.
String networks in Z{sub N} Lotka–Volterra competition models
Energy Technology Data Exchange (ETDEWEB)
Avelino, P.P., E-mail: Pedro.Avelino@astro.up.pt [Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Bazeia, D. [Instituto de Física, Universidade de São Paulo, 05314-970 São Paulo, SP (Brazil); Departamento de Física, Universidade Federal da Paraíba, 58051-970 João Pessoa, PB (Brazil); Menezes, J. [Centro de Física do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Escola de Ciências e Tecnologia, Universidade Federal do Rio Grande do Norte, Caixa Postal 1524, 59072-970 Natal, RN (Brazil); Oliveira, B.F. de [Departamento de Física, Universidade Estadual de Maringá, Av. Colombo 5790, 87020-900 Maringá, PR (Brazil)
2014-01-17
In this Letter we give specific examples of Z{sub N} Lotka–Volterra competition models leading to the formation of string networks. We show that, in order to promote coexistence, the species may arrange themselves around regions with a high number density of empty sites generated by predator–prey interactions between competing species. These configurations extend into the third dimension giving rise to string networks. We investigate the corresponding dynamics using both stochastic and mean field theory simulations, showing that the coarsening of these string networks follows a scaling law which is analogous to that found in other physical systems in condensed matter and cosmology.
Institute of Scientific and Technical Information of China (English)
LIM; C.W.
2010-01-01
Nonlinear combination parametric resonance is investigated for an axially accelerating viscoelastic string.The governing equation of in-planar motion of the string is established by introducing a coordinate transform in the Eulerian equation of a string with moving boundaries.The string under investigation is constituted by the standard linear solid model in which the material,not partial,time derivative was used.The governing equation leads to the Mote model for transverse vibration by omitting the longitudinal component and higher order terms.The Kirchhoff model is derived from the Mote model by replacing the tension with the averaged tension over the string.The two models are respectively analyzed via the method of multiple scales for principal parametric resonance.The amplitudes and the existence conditions of steady-state response and its stability can be numerically determined.Numerical calculations demonstrate the effects of the string material parameters,the initial tension,and the axial speed fluctuation amplitude.The outcomes of the two models are qualitatively and quantitatively compared.
Directory of Open Access Journals (Sweden)
Zhanghua Lian
2015-03-01
Full Text Available Multi-stage SRV fracturing in horizontal wells is a new technology developed at home and abroad in recent years to effectively develop shale gas or low-permeability reservoirs, but on the other hand makes the mechanical environment of fracturing strings more complicated at the same time. In view of this, based on the loading features of tubing strings during the multi-stage fracturing of a horizontal well, mechanical models were established for three working cases of multiple packer setting, open differential-pressure sliding sleeve, and open ball-injection sliding sleeve under a hold-down packer. Moreover, mathematical models were respectively built for the above three cases. According to the Lame formula and Von Mises stress calculation formula for the thick-walled cylinder in the theory of elastic mechanics, a mathematical model was also established to calculate the equivalent stress for tubing string safety evaluation when the fracturing string was under the combined action of inner pressure, external squeezing force and axial stress, and another mathematical model was built for the mechanical strength and safety evaluation of multi-stage fracturing strings. In addition, a practical software was developed for the mechanical safety evaluation of horizontal well multi-stage fracturing strings according to the mathematical model developed for the mechanical calculation of the multi-packer string in horizontal wells. The research results were applied and verified in a gas well of Tahe Oilfield in the Tarim Basin with excellent effects, providing a theoretical basis and a simple and reliable technical means for optimal design and safety evaluation of safe operational parameters of multi-stage fracturing strings in horizontal wells.
SU(4) string tensions from the fat-center-vortices model
Deldar, S; Deldar, Sedigheh; Rafibakhsh, Shahnoosh
2004-01-01
Fat-Center-Vortices model has been applied to calculate potentials between static sources of various SU(4) representations. For intermediate distances, a linear potential is achieved. For this region string tensions agree better with flux tube counting than Casimir scaling especially for higher representations. In addition, our results confirm the existence of two different string tensions for non zero 4-ality representations at large distances. In this area zero 4-ality representations are screened.
Zhanghua Lian; Ying Zhang; Xu Zhao; Shidong Ding; Tiejun Lin
2015-01-01
Multi-stage SRV fracturing in horizontal wells is a new technology developed at home and abroad in recent years to effectively develop shale gas or low-permeability reservoirs, but on the other hand makes the mechanical environment of fracturing strings more complicated at the same time. In view of this, based on the loading features of tubing strings during the multi-stage fracturing of a horizontal well, mechanical models were established for three working cases of multiple packer setting, ...
Color symmetrical superconductivity in a schematic nuclear quark model
DEFF Research Database (Denmark)
Bohr, Henrik; Providencia, C.; da Providencia, J.
2010-01-01
In this letter, a novel BCS-type formalism is constructed in the framework of a schematic QCD inspired quark model, having in mind the description of color symmetrical superconducting states. In the usual approach to color superconductivity, the pairing correlations affect only the quasi......-particle states of two colors, the single-particle states of the third color remaining unaffected by the pairing correlations. In the theory of color symmetrical superconductivity here proposed, the pairing correlations affect symmetrically the quasi-particle states of the three colors and vanishing net color...
Ristad, E S; Ristad, Eric Sven; Yianilos, Peter N.
1996-01-01
In many applications, it is necessary to determine the similarity of two strings. A widely-used notion of string similarity is the edit distance: the minimum number of insertions, deletions, and substitutions required to transform one string into the other. In this report, we provide a stochastic model for string edit distance. Our stochastic model allows us to learn a string edit distance function from a corpus of examples. We illustrate the utility of our approach by applying it to the difficult problem of learning the pronunciation of words in conversational speech. In this application, we learn a string edit distance with one fourth the error rate of the untrained Levenshtein distance. Our approach is applicable to any string classification problem that may be solved using a similarity function against a database of labeled prototypes. Keywords: string edit distance, Levenshtein distance, stochastic transduction, syntactic pattern recognition, prototype dictionary, spelling correction, string correction, ...
Axially symmetric anisotropic string cosmological models in Saez-Ballester theory of gravitation
Kanakavalli, T.; Rao, G. Ananda; Reddy, D. R. K.
2017-02-01
Field equations of a scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986) are derived with the help of a spatially homogeneous axially symmetric anisotropic Bianchi type metric in the presence of cosmic string source. To obtain determinate solutions of the field equations we have used the fact that the scalar expansion is proportional to shear scalar and the equations of state which correspond to geometric, Takabayasi and massive strings. It is found that geometric and massive strings do not coexist with the Saez-Ballester Scalar field. However, Takabayasi string which survives has been determined. Also, physical discussion of the dynamical parameters of the model is presented.
A note on probabilistic models over strings: the linear algebra approach.
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.
Bianchi Type-Ⅲ String Cosmological Model with Bulk Viscosity in General Relativity
Institute of Scientific and Technical Information of China (English)
WANG Xing-Xiang
2005-01-01
The Bianchi type-Ⅲcosmological model for a cloud string with bulk viscosity are studied. To obtain a determinate solution, it is assumed that the coefficient of bulk viscosity is a power function of the scalar of expansion ζ = kθm and the shear scalar is proportional to scalar of expansion σ∝θ, which leads to the relation between metric potentials B = Cn. The physical features of the model are also discussed. It is found that the power index mhas significant influence on the string model. There is a "big bang" start in the model when m ≤ 1 but there is no the big-bang start when m ＞ 1. In the special case m = 0, the model reduces to the string model of constant coefficient of bulk viscosity that was the result previously given in the literature.
Superconductivity of heavy fermions in the Kondo lattice model
Energy Technology Data Exchange (ETDEWEB)
Sykora, Steffen [IFW Dresden (Germany); Becker, Klaus W. [Institut fuer Theoretische Physik, Technische Universitaet Dresden (Germany)
2015-07-01
Understanding of the origin of superconductivity in strongly correlated electron systems is one of the basic unresolved problems in physics. Examples for such systems are the cuprates and also the heavy-fermion metals, which are compounds with 4f and 5f electrons. In all these materials the superconducting pairing interaction is often believed to be predominantly mediated by spin fluctuations and not by phonons as in normal metals. For the Kondo-lattice model we present results, which are derived within the Projective Renormalization Method (PRM). Based on a recent study of the one-particle spectral function for the normal state we first derive an effective Hamiltonian which describes heavy fermion quasiparticle bands close to the Fermi surface. An extension to the superconducting phase leads to d-wave solutions for the superconducting order parameter in agreement with recent STM measurements.
Supersymmetry and string theory beyond the standard model
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...
Proton Stability, Gauge Coupling Unification and a Light $Z^\\prime$ in Heterotic-string Models
Faraggi, Alon E
2013-01-01
We explore the phenomenological viability of a light $Z^\\prime$ in heterotic-string models, whose existence has been motivated by proton stability arguments. A class of quasi-realistic string models that produce such a viable $Z^\\prime$ are the Left-Right Symmetric (LRS) heterotic-string models in the free fermionic formulation. A key feature of these models is that the matter charges under $U(1)_{Z^\\prime}$ do not admit an $E_6$ embedding. The light $Z^\\prime$ in the LRS heterotic-string models forbids baryon number violating operators, while allowing lepton number violating operators, hence suppressing proton decay yet allowing for sufficiently small neutrino masses via a seesaw mechanism. We show that the constraints imposed by the gauge coupling data and heterotic-string coupling unification nullify the viability of a light $Z^\\prime$ in these models. We further argue that agreement with the gauge coupling data necessitates that the $U(1)_{Z^\\prime}$ charges admit an $E_6$ embedding. We discuss how viable...
Frequency-Zooming ARMA Modeling for Analysis of Noisy String Instrument Tones
Directory of Open Access Journals (Sweden)
Paulo A. A. Esquef
2003-09-01
Full Text Available This paper addresses model-based analysis of string instrument sounds. In particular, it reviews the application of autoregressive (AR modeling to sound analysis/synthesis purposes. Moreover, a frequency-zooming autoregressive moving average (FZ-ARMA modeling scheme is described. The performance of the FZ-ARMA method on modeling the modal behavior of isolated groups of resonance frequencies is evaluated for both synthetic and real string instrument tones immersed in background noise. We demonstrate that the FZ-ARMA modeling is a robust tool to estimate the decay time and frequency of partials of noisy tones. Finally, we discuss the use of the method in synthesis of string instrument sounds.
Casimir Energy and Vacua vor Superconducting Ball in Supergravity
Burinskii, A
2002-01-01
Casimir energy for solid conducting ball is considered on the base of some finite models. One model is physical and built of a battery of parallel metallic plates. Two finite models are based on the Higgs model of superconductivity. One of them is supersymmetric and based on the Witten field model for superconducting strings. Treatment shows that contribution of Casimir energy can be very essential for superdence state in the neutron stars and nuclear matter.
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.
Flemsæter, Bjorn
2000-01-01
The temperature of the superconducting magnets for the 27 km LHC particle accelerator under construction at CERN is a control parameter with strict operating constraints imposed by (a) the maximum temperature at which the magnets can operate, (b) the cooling capacity of the cryogenic system, (c) the variability of applied heat loads and (d) the accuracy of the instrumentation. A pilot plant for studying aspects beyond single magnet testing has been constructed. This magnet test string is a 35-m full-scale model if the LHC and consists of four superconducting cryogmagnets operating in a static bath of He II at 1.9 K. An experimental investigation of the properties dynamic characteristics of the 1.9 K cooling loop of the magnet test string has been carried out. A first principle model of the system has been created. A series of experiments designed for system identification purposes have been carried out, and black box models of the system have been created on the basis on the recorded data. A Model Predictive ...
String and string-inspired phenomenology
López, J L
1994-01-01
In these lectures I review the progress made over the last few years in the subject of string and string-inspired phenomenology. I take a practical approach, thereby concentrating more on explicit examples rather than on formal developments. Topics covered include: introduction to string theory the free-fermionic formulation and its general features, generic conformal field theory properties, SU(5)\\times U(1) GUT and string model-building, supersymmetry breaking, the bottom-up approach to string-inspired models, radiative electroweak symmetry breaking, the determination of the allowed parameter space of supergravity models and the experimental constraints on this class of models, and prospects for direct and indirect tests of string-inspired models. (Lectures delivered at the XXII ITEP International Winter School of Physics, Moscow, Russia, February 22 -- March 2, 1994)
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.
Perturbation of rotational motions for string models of hadrons and stability problem
Sharov, G S
2002-01-01
Small perturbations of the classical rotational motions (the system uniform rotation) are considered for the relativistic string with massive ends and also for the q-q-q and Y baryon string models. It is shown that such a motion for the string with massive ends is stable in the linear approximation and small perturbations are presentable in the form of the series, wherein each constituent describes the standing wave with the definite frequency. These modes ensure modeling different hadron excited states. At the same time the rotational motion instability is proven for the q-q-q and Y baryon models; the exponentially growing modes are detected in the spectrum of their perturbations
New Developments in String Gravity and String Cosmology.A Summary Report
Sánchez, N 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 Curved Backgrounds, and the 'QFT/String Tango'. 7- New Coherent String States and Minimal Uncertainty Principle in WZWN models
Integrable String Models in Terms of Chiral Invariants of SU(n, SO(n, SP(n Groups
Directory of Open Access Journals (Sweden)
Victor D. Gershun
2008-05-01
Full Text Available We considered two types of string models: on the Riemmann space of string coordinates with null torsion and on the Riemman-Cartan space of string coordinates with constant torsion. We used the hydrodynamic approach of Dubrovin, Novikov to integrable systems and Dubrovin solutions of WDVV associativity equation to construct new integrable string equations of hydrodynamic type on the torsionless Riemmann space of chiral currents in first case. We used the invariant local chiral currents of principal chiral models for SU(n, SO(n, SP(n groups to construct new integrable string equations of hydrodynamic type on the Riemmann space of the chiral primitive invariant currents and on the chiral non-primitive Casimir operators as Hamiltonians in second case. We also used Pohlmeyer tensor nonlocal currents to construct new nonlocal string equation.
A Mass Dependent String-Quintessence Model at the Planck Scale
Koperski, A P
2005-01-01
A combined quantum model may be constructed from elements of string theory and that of a quintessence field. This field derives from two fundamental constants, Planck's constant and the velocity of light to give a minimum quintessence mass, dependant on the Planck scale. The quintessence mass can then be applied in string theory in place of the standard Planck mass to enable the derivation of the frequency of both matter and electromagnetic fields. The model potentially further leads to the formation of a combined matter,force and real ether vacuum fields
Directory of Open Access Journals (Sweden)
Riionheimo Janne
2003-01-01
Full Text Available We describe a technique for estimating control parameters for a plucked string synthesis model using a genetic algorithm. The model has been intensively used for sound synthesis of various string instruments but the fine tuning of the parameters has been carried out with a semiautomatic method that requires some hand adjustment with human listening. An automated method for extracting the parameters from recorded tones is described in this paper. The calculation of the fitness function utilizes knowledge of the properties of human hearing.
Topological open string amplitudes on local toric del Pezzo surfaces via remodeling the B-model
Manabe, Masahide
2009-01-01
We study topological strings on local toric del Pezzo surfaces by a method called remodeling the B-model which was recently proposed by Bouchard, Klemm, Marino and Pasquetti. For a large class of local toric del Pezzo surfaces we prove a functional formula of the Bergman kernel which is the basic constituent of the topological string amplitudes by the topological recursion relation of Eynard and Orantin. Because this formula is written as a functional of the period, we can obtain the topological string amplitudes at any point of the moduli space by a simple change of variables of the Picard-Fuchs equations for the period. By this formula and mirror symmetry we calculate the A-model amplitudes on K_{F_2}, and predict the open orbifold Gromov-Witten invariants of C^3/Z_4.
Torsional vibrations of helically buckled drill-strings: experiments and FE modelling
Kapitaniak, M.; Hamaneh, V. V.; Wiercigroch, M.
2016-05-01
This paper presents investigations of a complex drill-string vibrations on a novel experimental rig, developed by the Centre for Applied Dynamics Research at the University of Aberdeen. The rig is capable of exhibiting of all major types of drill-string vibrations, including torsional, axial and lateral modes. The importance of this work lies in the fact, that the experimental rig utilizes real industrial drill-bits and rock samples, which after careful identification of Torque On Bit (TOB) speed curves, allows to use an equivalent friction model to accommodate for both frictional and cutting components of the bit-rock interactions. Moreover, the proposed Finite Element model, after a careful calibration, is capable of replicating experimental results, for the prebuckled configuration of the drill-string. This allows us to observe the effect of winding and unwinding of the helical deformation during stick-slip motion.
A matrix model for the topological string I: Deriving the matrix model
Eynard, Bertrand; Marchal, Olivier
2010-01-01
We construct a matrix model that reproduces the topological string partition function on arbitrary toric Calabi-Yau 3-folds. This demonstrates, in accord with the BKMP "remodeling the B-model" conjecture, that Gromov-Witten invariants of any toric Calabi-Yau 3-fold can be computed in terms of the spectral invariants of a spectral curve. Moreover, it proves that the generating function of Gromov-Witten invariants is a tau-function for an integrable hierarchy. In a follow-up paper, we will explicitly construct the spectral curve of our matrix model and argue that it equals the mirror curve of the toric Calabi-Yau manifold.
C(M)LESS-THAN-1 STRING THEORY AS A CONSTRAINED TOPOLOGICAL SIGMA-MODEL
LLATAS, PM; ROY, S
1995-01-01
It has been argued by Ishikawa and Kato that by making use of a specific bosonization, c(M) = 1 string theory can be regarded as a constrained topological sigma model. We generalize their construction for any (p,q) minimal model coupled to two dimensional (2d) gravity and show that the energy-moment
Analytical & Numerical Modelings of Elliptical Superconducting Filament Magnetization
Bottura, L; Bouillault, F; Devred, Arnaud
2005-01-01
This paper deals with the two-dimensional computation of magnetization in an elliptic superconducting filament by using numerical and analytical methods. The numerical results are obtained from the finite element method and by using Bean's model. This model is well adapted for Low Tc superconductor studies. We observe the effect of the axis ratio and of the field angle to the magnetic moment per unit length at saturation, and also to the cycle of magnetization. Moreover, the current density and the distribution of the electromagnetic fields in the superconducting filament are also studied.
Experience with the String2 Cryogenic Instrumentation and Control System
Gomes, P; Blanco-Viñuela, E; Casas-Cubillos, J; Pelletier, S; Rodríguez, M A; Serio, L; Suraci, A; Vauthier, N
2005-01-01
String2 was a 120 m full-scale model of a regular cell of the LHC accelerator arc. It was composed of eight superconducting main magnets, fed by a separate cryogenic distribution line (QRL); an electrical feed box (DFB) which supported the superconducting current leads that powered the magnets [1]. Bearing an intensive experimental programme, String2 was heavily instrumented. The cryogenic instrumentation and control system, whose complexity was close to a full 3.3 km LHC sector, have already been described in [2]. String2 was a useful facility to validate design choices and to gain knowledge on installation and commissioning procedures. This paper reports on the experience of four years of designing, installation, commissioning and maintenance, and outlines the lessons learned for the LHC.
Multidimensional extremal dilatonic black holes in string-like model with cosmological term
Ivashchuk, V D
1996-01-01
A string-like model with the "cosmological constant" \\Lambda is considered. The Maki-Shiraishi multi-black-hole solution \\cite{MS1} is generalized to space-times with a Ricci-flat internal space. For \\Lambda = 0 the obtained solution in the one-black-hole case is shown to coincide with the extreme limit of the charged dilatonic black hole solution \\cite{BI,BM}. The Hawking temperature T_H for the solution \\cite{BI,BM} is presented and its extreme limit is considered. For the string value of dilatonic coupling the temperature T_H does not depend upon the internal space dimension.
CP(N-1) model on a disk and decay of a non-Abelian string
Gorsky, A.; Milekhin, A.
2013-10-01
We consider the role of quantum effects in the nonperturbative decay of the non-Abelian string with orientational moduli in nonsupersymmetric D=4 gauge theory. To this aim the effective action in the CP(N-1) model on a disk at large N has been calculated. It exhibits a phase transition at some radius, the “wrong sign” Luscher term, and a large boundary boojumlike negative contribution. The effect of the θ term and the possibility of the spontaneous creation of the non-Abelian string are briefly discussed.
The string prediction models as invariants of time series in the forex market
Pincak, R.
2013-12-01
In this paper we apply a new approach of string theory to the real financial market. The models are constructed with an idea of prediction models based on the string invariants (PMBSI). The performance of PMBSI is compared to support vector machines (SVM) and artificial neural networks (ANN) on an artificial and a financial time series. A brief overview of the results and analysis is given. The first model is based on the correlation function as invariant and the second one is an application based on the deviations from the closed string/pattern form (PMBCS). We found the difference between these two approaches. The first model cannot predict the behavior of the forex market with good efficiency in comparison with the second one which is, in addition, able to make relevant profit per year. The presented string models could be useful for portfolio creation and financial risk management in the banking sector as well as for a nonlinear statistical approach to data optimization.
Bianchi Type-I bulk viscous fluid string dust magnetized cosmological model in general relativity
Indian Academy of Sciences (India)
Raj Bali; Anjali
2004-09-01
Bianchi Type-I magnetized bulk viscous fluid string dust cosmological model is investigated. To get a determinate model, we have assumed the conditions and = constant where is the shear, the expansion in the model and the coefficient of bulk viscosity. The behaviour of the model in the presence and absence of magnetic field together with physical and geometrical aspects of the model are also discussed.
submitter Thermal, Hydraulic, and Electromagnetic Modeling of Superconducting Magnet Systems
Bottura, L
2016-01-01
Modeling techniques and tailored computational tools are becoming increasingly relevant to the design and analysis of large-scale superconducting magnet systems. Efficient and reliable tools are useful to provide an optimal forecast of the envelope of operating conditions and margins, which are difficult to test even when a prototype is available. This knowledge can be used to considerably reduce the design margins of the system, and thus the overall cost, or increase reliability during operation. An integrated analysis of a superconducting magnet system is, however, a complex matter, governed by very diverse physics. This paper reviews the wide spectrum of phenomena and provides an estimate of the time scales of thermal, hydraulic, and electromagnetic mechanisms affecting the performance of superconducting magnet systems. The analysis is useful to provide guidelines on how to divide the complex problem into building blocks that can be integrated in a design and analysis framework for a consistent multiphysic...
Anomalous superconductivity in the tJ model; moment approach
DEFF Research Database (Denmark)
Sørensen, Mads Peter; Rodriguez-Nunez, J.J.
1997-01-01
By extending the moment approach of Nolting (Z, Phys, 225 (1972) 25) in the superconducting phase, we have constructed the one-particle spectral functions (diagonal and off-diagonal) for the tJ model in any dimensions. We propose that both the diagonal and the off-diagonal spectral functions...... Hartree shift which in the end result enlarges the bandwidth of the free carriers allowing us to take relative high values of J/t and allowing superconductivity to live in the T-c-rho phase diagram, in agreement with numerical calculations in a cluster, We have calculated the static spin susceptibility......, chi(T), and the specific heat, C-v(T), within the moment approach. We find that all the relevant physical quantities show the signature of superconductivity at T-c in the form of kinks (anomalous behavior) or jumps, for low density, in agreement with recent published literature, showing a generic...
Nonlinear observer design for a nonlinear string/cable FEM model using contraction theory
DEFF Research Database (Denmark)
Turkyilmaz, Yilmaz; Jouffroy, Jerome; Egeland, Olav
Contraction theory is a recently developed nonlinear analysis tool which may be useful for solving a variety of nonlinear control problems. In this paper, using Contraction theory, a nonlinear observer is designed for a general nonlinear cable/string FEM (Finite Element Method) model. The cable...
Nonlinear observer design for a nonlinear string/cable FEM model using contraction theory
DEFF Research Database (Denmark)
Turkyilmaz, Yilmaz; Jouffroy, Jerome; Egeland, Olav
Contraction theory is a recently developed nonlinear analysis tool which may be useful for solving a variety of nonlinear control problems. In this paper, using Contraction theory, a nonlinear observer is designed for a general nonlinear cable/string FEM (Finite Element Method) model. The cable...
Modeling of wave propagation in drill strings using vibration transfer matrix methods.
Han, Je-Heon; Kim, Yong-Joe; Karkoub, Mansour
2013-09-01
In order to understand critical vibration of a drill bit such as stick-slip and bit-bounce and their wave propagation characteristics through a drill string system, it is critical to model the torsional, longitudinal, and flexural waves generated by the drill bit vibration. Here, a modeling method based on a vibration transfer matrix between two sets of structural wave variables at the ends of a constant cross-sectional, hollow, circular pipe is proposed. For a drill string system with multiple pipe sections, the total vibration transfer matrix is calculated by multiplying all individual matrices, each is obtained for an individual pipe section. Since drill string systems are typically extremely long, conventional numerical analysis methods such as a finite element method (FEM) require a large number of meshes, which makes it computationally inefficient to analyze these drill string systems numerically. The proposed "analytical" vibration transfer matrix method requires significantly low computational resources. For the validation of the proposed method, experimental and numerical data are obtained from laboratory experiments and FEM analyses conducted by using a commercial FEM package, ANSYS. It is shown that the modeling results obtained by using the proposed method are well matched with the experimental and numerical results.
Open topological strings and integrable hierarchies: Remodeling the A-model
Brini, Andrea
2011-01-01
We set up, purely in A-model terms, a novel formalism for the global solution of the open and closed topological A-model on toric Calabi-Yau threefolds. The starting point is to build on recent progress in the mathematical theory of open Gromov-Witten invariants of orbifolds; we interpret the localization formulae as relating D-brane amplitudes to closed string amplitudes perturbed with twisted masses through an analogue of the "loop insertion operator" of matrix models. We first generalize this form of open/closed string duality to general toric backgrounds in all chambers of the stringy Kaehler moduli space; secondarily, we display a neat connection of the (gauged) closed string side to tau functions of 1+1 Hamiltonian integrable hierarchies, and exploit it to provide an effective computation of open string amplitudes. In doing so, we also provide a systematic treatment of the change of flat open moduli induced by a phase transition in the closed moduli space. We test our proposal in detail by providing an ...
A Hybrid Resynthesis Model for Hammer-String Interaction of Piano Tones
Directory of Open Access Journals (Sweden)
Jensen Kristoffer
2004-01-01
Full Text Available This paper presents a source/resonator model of hammer-string interaction that produces realistic piano sound. The source is generated using a subtractive signal model. Digital waveguides are used to simulate the propagation of waves in the resonator. This hybrid model allows resynthesis of the vibration measured on an experimental setup. In particular, the nonlinear behavior of the hammer-string interaction is taken into account in the source model and is well reproduced. The behavior of the model parameters (the resonant part and the excitation part is studied with respect to the velocities and the notes played. This model exhibits physically and perceptually related parameters, allowing easy control of the sound produced. This research is an essential step in the design of a complete piano model.
The Area Law in Matrix Models for Large N QCD Strings
Anagnostopoulos, K N; Nishimura, J
2002-01-01
We study the question whether matrix models obtained in the zero volume limit of 4d Yang-Mills theories can describe large N QCD strings. The matrix model we use is a variant of the Eguchi-Kawai model in terms of Hermitian matrices, but without any twists or quenching. This model was originally proposed as a toy model of the IIB matrix model. In contrast to common expectations, we do observe the area law for Wilson loops in a significant range of scale of the loop area. Numerical simulations show that this range is stable as N increases up to 768, which strongly suggests that it persists in the large N limit. Hence the equivalence to QCD strings may hold for length scales inside a finite regime.
A matrix model for the topological string II: The spectral curve and mirror geometry
Eynard, Bertrand; Marchal, Olivier
2010-01-01
In a previous paper, we presented a matrix model reproducing the topological string partition function on an arbitrary given toric Calabi-Yau manifold. Here, we study the spectral curve of our matrix model and thus derive, upon imposing certain minimality assumptions on the spectral curve, the large volume limit of the BKMP "remodeling the B-model" conjecture, the claim that Gromov-Witten invariants of any toric Calabi-Yau 3-fold coincide with the spectral invariants of its mirror curve.
Bianchi Type-Ⅲ String Cosmological Model With Bulk Viscosity and Magnetic Field
Institute of Scientific and Technical Information of China (English)
WANG Xing-Xiang
2006-01-01
@@ The Bianchi type-Ⅲ cosmological model for a cloud string in the presence of bulk viscosity and magnetic field are presented. To obtain the determinate model it is assumed that there is an equation of state ρ = kλ and the scalar of expansion is proportional to the shear scalar θ∝σ, which leads to a relation between metric potentials B = mCn. The physical and geometric aspects of the model are also discussed. The model describes a shearing non-rotating continuously expanding universe with a big-bang start. In the absence of magnetic field, it reduces to the string model with bulk viscosity that was previously given in the literature.
Boucher, Christina; Ma, Bin
2011-02-15
Given n strings s1, …, sn each of length ℓ and a nonnegative integer d, the CLOSEST STRING problem asks to find a center string s such that none of the input strings has Hamming distance greater than d from s. Finding a common pattern in many--but not necessarily all--input strings is an important task that plays a role in many applications in bioinformatics. Although the closest string model is robust to the oversampling of strings in the input, it is severely affected by the existence of outliers. We propose a refined model, the closest string with outliers (CSWO) problem, to overcome this limitation. This new model asks for a center string s that is within Hamming distance d to at least n - k of the n input strings, where k is a parameter describing the maximum number of outliers. A CSWO solution not only provides the center string as a representative for the set of strings but also reveals the outliers of the set.We provide fixed parameter algorithms for CSWO when d and k are parameters, for both bounded and unbounded alphabets. We also show that when the alphabet is unbounded the problem is W[1]-hard with respect to n - k, ℓ, and d. Our refined model abstractly models finding common patterns in several but not all input strings. We initialize the study of the computability of this model and show that it is sensitive to different parameterizations. Lastly, we conclude by suggesting several open problems which warrant further investigation.
Golubovic, Leonardo; Knudsen, Steven
2017-01-01
We consider general problem of modeling the dynamics of objects sliding on moving strings. We introduce a powerful computational algorithm that can be used to investigate the dynamics of objects sliding along non-relativistic strings. We use the algorithm to numerically explore fundamental physics of sliding climbers on a unique class of dynamical systems, Rotating Space Elevators (RSE). Objects sliding along RSE strings do not require internal engines or propulsion to be transported from the Earth's surface into outer space. By extensive numerical simulations, we find that sliding climbers may display interesting non-linear dynamics exhibiting both quasi-periodic and chaotic states of motion. While our main interest in this study is in the climber dynamics on RSEs, our results for the dynamics of sliding object are of more general interest. In particular, we designed tools capable of dealing with strongly nonlinear phenomena involving moving strings of any kind, such as the chaotic dynamics of sliding climbers observed in our simulations.
Matrix Models of 2D String Theory in Non--trivial Backgrounds
Koetsier, Arnaud
2005-01-01
After a brief review of critical string theory in trivial backgrounds we begin with introduction to strings in non--trivial backgrounds and noncritical string theory. In particular, we relate the latter to critical string theory in a linear dilaton background. We then show how a black hole background arises from 2D string theory and discuss some of its properties. A time--dependant tachyon background is constructed by perturbing the CFT describing string theory in a linear dilaton background....
Propagation of cosmic rays through the atmosphere in the quark-gluon strings model
Erlykin, A. D.; Krutikova, N. P.; Shabelski, Y. M.
1985-01-01
The quark-gluon strings model succeeds in the description of multiple hadron production in the central rapidity region of nucleon-nucleon interctions. This model was developed for hadron-nucleus interactions and used for calculation of the cosmic ray propagation through the atmosphere. It is shown that at energies 10 to the 11th power to the 12th power eV, this model gives a satisfactory description of experimental data. But with the increase of the energy up to approximately 10 to the 14th power eV, results of calculations and of experiments begin to differ and this difference rises with the energy. It may indicate that the scaling violation in the fragmentation region of inclusive spectra for hadron-nucleus interactions is stronger than in the quark-gluon strings model.
Complexity of chromatin folding is captured by the strings and binders switch model.
Barbieri, Mariano; Chotalia, Mita; Fraser, James; Lavitas, Liron-Mark; Dostie, Josée; Pombo, Ana; Nicodemi, Mario
2012-10-02
Chromatin has a complex spatial organization in the cell nucleus that serves vital functional purposes. A variety of chromatin folding conformations has been detected by single-cell imaging and chromosome conformation capture-based approaches. However, a unified quantitative framework describing spatial chromatin organization is still lacking. Here, we explore the "strings and binders switch" model to explain the origin and variety of chromatin behaviors that coexist and dynamically change within living cells. This simple polymer model recapitulates the scaling properties of chromatin folding reported experimentally in different cellular systems, the fractal state of chromatin, the processes of domain formation, and looping out. Additionally, the strings and binders switch model reproduces the recently proposed "fractal-globule" model, but only as one of many possible transient conformations.
Light-light and heavy-light mesons in the model of QCD string with quarks at the ends
Nefediev, A V
2002-01-01
The variational einbein field method is applied to the model of the QCD string with quarks at the ends for the case of light-light and heavy-light mesons. Special attention is payed to the proper string dynamics. The correct string slope of the Regge trajectories is reproduced for light-light states which comes out from the picture of rotating string. Masses of several low-lying orbitally and radially excited states in the D, D_s, B, and B_s meson spectra are calculated and a good agreement with the experimental data as well as with recent lattice calculations is found. The role of the string correction to the interquark interaction is discussed at the example of the identification of D*'(2637) state recently claimed by DELPHI Collaboration. For the heavy-light mesons the standard constants used in Heavy Quark Effective Theory are extracted and compared to the results of other approaches.
Realistic three-generation models from SO(32) heterotic string theory
Abe, Hiroyuki; Otsuka, Hajime; Takano, Yasufumi
2015-01-01
We search for realistic supersymmetric standard-like models from SO(32) heterotic string theory on factorizable tori with multiple magnetic fluxes. Three chiral ganerations of quarks and leptons are derived from the adjoint and vector representations of SO(12) gauge groups embedded in SO(32) adjoint representation. Massless spectra of our models also include Higgs fields, which have desired Yukawa couplings to quarks and leptons at the tree-level.
Coexistence of Incommensurate Magnetism and Superconductivity in the Two-Dimensional Hubbard Model.
Yamase, Hiroyuki; Eberlein, Andreas; Metzner, Walter
2016-03-04
We analyze the competition of magnetism and superconductivity in the two-dimensional Hubbard model with a moderate interaction strength, including the possibility of incommensurate spiral magnetic order. Using an unbiased renormalization group approach, we compute magnetic and superconducting order parameters in the ground state. In addition to previously established regions of Néel order coexisting with d-wave superconductivity, the calculations reveal further coexistence regions where superconductivity is accompanied by incommensurate magnetic order.
Antiferromagnetism and d-wave superconductivity in the Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Krahl, H.C.
2007-07-25
The two-dimensional Hubbard model is a promising effective model for the electronic degrees of freedom in the copper-oxide planes of high temperature superconductors. We present a functional renormalization group approach to this model with focus on antiferromagnetism and d-wave superconductivity. In order to make the relevant degrees of freedom more explicitly accessible on all length scales, we introduce composite bosonic fields mediating the interaction between the fermions. Spontaneous symmetry breaking is reflected in a non-vanishing expectation value of a bosonic field. The emergence of a coupling in the d-wave pairing channel triggered by spin wave fluctuations is demonstrated. Furthermore, the highest temperature at which the interaction strength for the electrons diverges in the renormalization flow is calculated for both antiferromagnetism and d-wave superconductivity over a wide range of doping. This ''pseudo-critical'' temperature signals the onset of local ordering. Moreover, the temperature dependence of d-wave superconducting order is studied within a simplified model characterized by a single coupling in the d-wave pairing channel. The phase transition within this model is found to be of the Kosterlitz-Thouless type. (orig.)
Modeling of unusual nonlinear behaviors in superconducting microstrip transmission lines
Energy Technology Data Exchange (ETDEWEB)
Javadzadeh, S. Mohammad Hassan, E-mail: smh_javadzadeh@ee.sharif.edu [School of Electrical Engineering, Sharif University of Technology, P.O. Box 11365-9363, Tehran (Iran, Islamic Republic of); Farzaneh, Forouhar; Fardmanesh, Mehdi [School of Electrical Engineering, Sharif University of Technology, P.O. Box 11365-9363, Tehran (Iran, Islamic Republic of)
2013-03-15
Highlights: ► Avoiding of considering just quadratic or modulus nonlinearity. ► Proposing a nonlinear model to predict unusual nonlinear behaviors at low temperatures. ► Description of temperature dependency of nonlinear behaviors in superconducting lines. ► Analytical formulation for each parameter in our proposed model. ► Obtaining very good results which shows this model can predict unusual nonlinear behavior. -- Abstract: There are unusual nonlinear behaviors in superconducting materials, especially at low temperatures. This paper describes the procedure to reliably predict this nonlinearity in superconducting microstrip transmission lines (SMTLs). An accurate nonlinear distributed circuit model, based on simultaneously considering of both quadratic and modulus nonlinearity dependences, is proposed. All parameters of the equivalent circuit can be calculated analytically using proposed closed-form expressions. A numerical method based on Harmonic Balance approach is used to predict nonlinear phenomena like intermodulation distortions and third harmonic generations. Nonlinear analyses of the SMTLs at the different temperatures and the input powers have been presented. This proposed model can describe the unusual behaviors of the nonlinearity at low temperatures, which are frequently observed in the SMTLs.
Gauge coupling and fermion mass relations in low string scale brane models
Energy Technology Data Exchange (ETDEWEB)
Gioutsos, D.V.; Leontaris, G.K.; Rizos, J. [Ioannina University, Theoretical Physics Division, Ioannina (Greece)
2006-01-01
We analyze the gauge coupling evolution in brane inspired models with U(3) x U(2) x U(1){sup N} symmetry at the string scale. We restrict our work to the case of brane configurations with two and three abelian factors (N=2,3) and where only one Higgs doublet is coupled to down quarks and leptons and only one to the up quarks. We find that the correct hypercharge assignment of the standard model particles is reproduced for six viable models distinguished by different brane configurations. We investigate the third generation fermion mass relations and find that the correct low energy m{sub b}/m{sub {tau}} ratio can be obtained for b-{tau} Yukawa coupling equality at a string scale as low as M{sub S}{proportional_to}10{sup 3} TeV. (orig.)
Pereira, José A
2014-08-01
Theoretical models designed to test the metabolism-first hypothesis for prebiotic evolution have yield strong indications about the hypothesis validity but could sometimes use a more extensive identification between model objects and real objects towards a more meaningful interpretation of results. In an attempt to go in that direction, the string-based model SSE ("steady state evolution") was developed, where abstract molecules (strings) and catalytic interaction rules are based on some of the most important features of carbon compounds in biological chemistry. The system is open with a random inflow and outflow of strings but also with a permanent string food source. Although specific catalysis is a key aspect of the model, used to define reaction rules, the focus is on energetics rather than kinetics. Standard energy change tables were constructed and used with standard formation reactions to track energy flows through the interpretation of equilibrium constant values. Detection of metabolic networks on the reaction system was done with elementary flux mode (EFM) analysis. The combination of these model design and analysis options enabled obtaining metabolic and catalytic networks showing several central features of biological metabolism, some more clearly than in previous models: metabolic networks with stepwise synthesis, energy coupling, catalysts regulation, SN2 coupling, redox coupling, intermediate cycling, coupled inverse pathways (metabolic cycling), autocatalytic cycles and catalytic cascades. The results strongly suggest that the main biological metabolism features, including the genotype-phenotype interpretation, are caused by the principles of catalytic systems and are prior to modern genetic systems principles. It also gives further theoretical support to the thesis that the basic features of biologic metabolism are a consequence of the time evolution of a random catalyst search working on an open system with a permanent food source. The importance
AdS5×S(5) mirror model as a string sigma model.
Arutyunov, Gleb; van Tongeren, Stijn J
2014-12-31
Doing a double Wick rotation in the world sheet theory of the light cone AdS5×S(5) superstring results in an inequivalent, so-called mirror theory that plays a central role in the field of integrability in the AdS-CFT correspondence. We show that this mirror theory can be interpreted as the light cone theory of a free string on a different background. This background is related to dS5×H(5) by a double T-duality, and has hidden supersymmetry. The geometry can also be extracted from an integrable deformation of the AdS5×S(5) sigma model, and we prove the observed mirror duality of these deformed models at the bosonic level as a byproduct. While we focus on AdS5×S(5), our results apply more generally.
Cappelli, Andrea; Castellani, Elena; Colomo, Filippo; Di Vecchia, Paolo
2012-04-01
Part I. Overview: 1. Introduction and synopsis; 2. Rise and fall of the hadronic string G. Veneziano; 3. Gravity, unification, and the superstring J. H. Schwarz; 4. Early string theory as a challenging case study for philosophers E. Castellani; Part II. The Prehistory: The Analytic S-Matrix: 5. Introduction to Part II; 6. Particle theory in the sixties: from current algebra to the Veneziano amplitude M. Ademollo; 7. The path to the Veneziano model H. R. Rubinstein; 8. Two-component duality and strings P. G. O. Freund; 9. Note on the prehistory of string theory M. Gell-Mann; Part III. The Dual Resonance Model: 10. Introduction to Part III; 11. From the S-matrix to string theory P. Di Vecchia; 12. Reminiscence on the birth of string theory J. A. Shapiro; 13. Personal recollections D. Amati; 14. Early string theory at Fermilab and Rutgers L. Clavelli; 15. Dual amplitudes in higher dimensions: a personal view C. Lovelace; 16. Personal recollections on dual models R. Musto; 17. Remembering the 'supergroup' collaboration F. Nicodemi; 18. The '3-Reggeon vertex' S. Sciuto; Part IV. The String: 19. Introduction to Part IV; 20. From dual models to relativistic strings P. Goddard; 21. The first string theory: personal recollections L. Susskind; 22. The string picture of the Veneziano model H. B. Nielsen; 23. From the S-matrix to string theory Y. Nambu; 24. The analogue model for string amplitudes D. B. Fairlie; 25. Factorization in dual models and functional integration in string theory S. Mandelstam; 26. The hadronic origins of string theory R. C. Brower; Part V. Beyond the Bosonic String: 27. Introduction to Part V; 28. From dual fermion to superstring D. I. Olive; 29. Dual models with fermions: memoirs of an early string theorist P. Ramond; 30. Personal recollections A. Neveu; 31. Aspects of fermionic dual models E. Corrigan; 32. The dual quark models K. Bardakci and M. B. Halpern; 33. Remembering the dawn of relativistic strings J.-L. Gervais; 34. Early string theory in
The Fluctuating Bond Model, a Glue for Cuprate Superconductivity?
Newns, Dennis
2008-03-01
Twenty years of research have yet to produce a consensus on the origin of high temperature superconductivity (HTS). The mechanism of HTS - which originates in the CuO2 plane, common to all HTS families - can be constrained by some key experimental facts regarding superconducting and pseudogap behaviors. Superconductivity, involving a Tc of order 100 K, exhibits an unusual d-wave superconducting gap, with Fermi liquid nodal excitations, and an anomalous doping- dependent oxygen isotope shift. A ``pseudogap,'' also with d-symmetry, leads to a dip in the density of states below a characteristic temperature scale T^*, which has a negative isotope shift; we associate the pseudogap with the recently observed spatially inhomogeneous (nanometer- scale) C4 symmetry breaking. The isotope shifts and other evidence imply a key role for oxygen vibrations, but conventional BCS single-phonon coupling is essentially forbidden by symmetry and by the on-site Coulomb interaction U. In a novel approach, we introduce a model based on a strong, local, nonlinear interaction between electrons within the Cu-O-Cu bond in the CuO2 plane, and the oxygen vibrational degrees of freedom, termed the Fluctuating Bond Model (FBM) [D.M. Newns and C.C. Tsuei, Nature Physics 3, 184 (2007)]. In mean field the model predicts a phase manifesting broken C4 symmetry, with a d-type pseudogap, and an upper phase boundary in temperature, with a negative isotope shift, which we identify with T^*. An intrinsic d-wave pairing tendency is found, leading to a transition temperature dome and an anomalous isotope shift similar to that found experimentally. The softening in the oxygen vibrational frequency below Tc, seen in Raman and neutron spectra, has a natural explanation in the FBM. Recent ab initio calculations have been implemented which provide microscopic support for the model.
Experimental investigation into the degradation of model superconducting windings
Energy Technology Data Exchange (ETDEWEB)
Trusov, N.B.; Broitman, I.M.; Pleshchunov, N.N.; Samoilov, S.F.
1984-01-01
Results are reported for an investigation into degradation of critical current in model compound-treated windings fabricated from type KETV-2NT superconducting conductors with nonsteady stabilization. It is shown that the way in which the critical current depends on the heat-removal conditions and the rate of entry of current is determined by a mechanism of steady-state heat release occationed by plastic strain of the winding materials under the action of ponderomotive forces.
Models for Small-Scale Structure on Cosmic Strings: II. Scaling and its stability
Vieira, J P P; Shellard, E P S
2016-01-01
We make use of the formalism described in a previous paper [Martins {\\it et al.} Phys. Rev. D90 (2014) 043518] to address general features of wiggly cosmic string evolution. In particular, we highlight the important role played by poorly understood energy loss mechanisms and propose a simple ansatz which tackles this problem in the context of an extended velocity-dependent one-scale model. We find a general procedure to determine all the scaling solutions admitted by a specific string model and study their stability, enabling a detailed comparison with future numerical simulations. A simpler comparison with previous Goto-Nambu simulations supports earlier evidence that scaling is easier to achieve in the matter era than in the radiation era. In addition, we also find that the requirement that a scaling regime be stable seems to notably constrain the allowed range of energy loss parameters.
Higher spin holography and the AdS string sigma model
Polyakov, Dimitri
2013-05-01
We analyse the cubic spin-3 interaction in AdS space using the higher spin extension of the string-theoretic sigma-model constructed in our previous work, whose low energy limit is described by the AdS vacuum solution. We find that, in the leading order of the cosmological constant, the spin-3 correlator on the AdS4 string theory side reproduces the structure of the three-point function of composite operators, quadratic in free fields, in the dual d = 3 vector model. The cancellation of holography violating terms in d = 3 is related to the value of the Liouville background charge in d = 4. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Higher spin theories and holography’.
String states, loops and effective actions in noncommutative field theory and matrix models
Directory of Open Access Journals (Sweden)
Harold C. Steinacker
2016-09-01
Full Text Available Refining previous work by Iso, Kawai and Kitazawa, we discuss bi-local string states as a tool for loop computations in noncommutative field theory and matrix models. Defined in terms of coherent states, they exhibit the stringy features of noncommutative field theory. This leads to a closed form for the 1-loop effective action in position space, capturing the long-range non-local UV/IR mixing for scalar fields. The formalism applies to generic fuzzy spaces. The non-locality is tamed in the maximally supersymmetric IKKT or IIB model, where it gives rise to supergravity. The linearized supergravity interactions are obtained directly in position space at one loop using string states on generic noncommutative branes.
String states, loops and effective actions in noncommutative field theory and matrix models
Energy Technology Data Exchange (ETDEWEB)
Steinacker, Harold C., E-mail: harold.steinacker@univie.ac.at
2016-09-15
Refining previous work by Iso, Kawai and Kitazawa, we discuss bi-local string states as a tool for loop computations in noncommutative field theory and matrix models. Defined in terms of coherent states, they exhibit the stringy features of noncommutative field theory. This leads to a closed form for the 1-loop effective action in position space, capturing the long-range non-local UV/IR mixing for scalar fields. The formalism applies to generic fuzzy spaces. The non-locality is tamed in the maximally supersymmetric IKKT or IIB model, where it gives rise to supergravity. The linearized supergravity interactions are obtained directly in position space at one loop using string states on generic noncommutative branes.
De Sitter vacua in no-scale supergravities and Calabi-Yau string models
Covi, Laura; Gross, Christian; Louis, Jan; Palma, Gonzalo A; Scrucca, Claudio A
2008-01-01
We perform a general analysis on the possibility of obtaining metastable vacua with spontaneously broken N=1 supersymmetry and non-negative cosmological constant in the moduli sector of string models. More specifically, we study the condition under which the scalar partners of the Goldstino are non-tachyonic, which depends only on the Kahler potential. This condition is not only necessary but also sufficient, in the sense that all of the other scalar fields can be given arbitrarily large positive square masses if the superpotential is suitably tuned. We consider both heterotic and orientifold string compactifications in the large-volume limit and show that the no-scale property shared by these models severely restricts the allowed values for the `sGoldstino' masses in the superpotential parameter space. We find that a positive mass term may be achieved only for certain types of compactifications and specific Goldstino directions. Additionally, we show how subleading corrections to the Kahler potential which b...
Decoupling A and B model in open string theory Topological adventures in the world of tadpoles
Bonelli, Giulio; Tanzini, Alessandro; Yang, Jie
2009-01-01
In this paper we analyze the problem of tadpole cancellation in open topological strings. We prove that the inclusion of unorientable worldsheet diagrams guarantees a consistent decoupling of A and B model for open superstring amplitudes at all genera. This is proven by direct microscopic computation in Super Conformal Field Theory. For the B-model we explicitly calculate one loop amplitudes in terms of analytic Ray-Singer torsions of appropriate vector bundles and obtain that the decoupling corresponds to the cancellation of D-brane and orientifold charges. Local tadpole cancellation on the worldsheet then guarantees the decoupling at all loops. The holomorphic anomaly equations for open topological strings at one loop are also obtained and compared with the results of the Quillen formula.
Borel and Stokes Nonperturbative Phenomena in Topological String Theory and c=1 Matrix Models
Pasquetti, Sara
2010-01-01
We address the nonperturbative structure of topological strings and c=1 matrix models, focusing on understanding the nature of instanton effects alongside with exploring their relation to the large-order behavior of the 1/N expansion. We consider the Gaussian, Penner and Chern-Simons matrix models, together with their holographic duals, the c=1 minimal string at self-dual radius and topological string theory on the resolved conifold. We employ Borel analysis to obtain the exact all-loop multi-instanton corrections to the free energies of the aforementioned models, and show that the leading poles in the Borel plane control the large-order behavior of perturbation theory. We understand the nonperturbative effects in terms of the Schwinger effect and provide a semiclassical picture in terms of eigenvalue tunneling between critical points of the multi-sheeted matrix model effective potentials. In particular, we relate instantons to Stokes phenomena via a hyperasymptotic analysis, providing a smoothing of the nonp...
The cancellation of world-sheet anomalies in the D=10 Green-Schwarz heterotic string sigma model
Energy Technology Data Exchange (ETDEWEB)
Lechner, K. [Padua Univ. (Italy). Dipt. di Fisica; Tonin, M. [Padua Univ. (Italy). Dipt. di Fisica
1996-09-16
We determine the two-dimensional Weyl, Lorentz and {kappa}-anomalies in the D=10 Green-Schwarz heterotic string sigma model, in an SO(1,9) Lorentz-covariant background gauge, and prove their cancellation. (orig.).
Reconnection of Colliding Cosmic Strings
Hanany, A; Hanany, Amihay; Hashimoto, Koji
2005-01-01
For vortex strings in the Abelian Higgs model and D-strings in superstring theory, both of which can be regarded as cosmic strings, we give analytical study of reconnection (recombination, inter-commutation) when they collide, by using effective field theories on the strings. First, for the vortex strings, via a string sigma model, we verify analytically that the reconnection is classically inevitable for small collision velocity and small relative angle. Evolution of the shape of the reconnected strings provides an upper bound on the collision velocity in order for the reconnection to occur. These analytical results are in agreement with previous numerical results. On the other hand, reconnection of the D-strings is not classical but probabilistic. We show that a quantum calculation of the reconnection probability using a D-string action reproduces the nonperturbative nature of the worldsheet results by Jackson, Jones and Polchinski. The difference on the reconnection -- classically inevitable for the vortex...
Production of phi-mesons on nuclear targets in the Quark-Gluon String model
Arakelyan, G H; Shabelski, Yu M
2016-01-01
We consider the experimental data on phi-meson production on nuclear targets, and we find that they present unusually small shadow corrections for the inclusive density in the midrapidity region. We also give a quantitatively consistent description of both the initial energy dependence and the A-dependence of the produced phi-mesons, obtained in the frame of the Quark-Gluon String Model.
Complexity of chromatin folding is captured by the strings and binders switch model
Barbieri, Mariano; Chotalia, Mita; Fraser, James; Lavitas, Liron-Mark; Dostie, Josée; Pombo, Ana; Nicodemi, Mario
2012-01-01
Chromatin has a complex spatial organization in the cell nucleus that serves vital functional purposes. A variety of chromatin folding conformations has been detected by single-cell imaging and chromosome conformation capture-based approaches. However, a unified quantitative framework describing spatial chromatin organization is still lacking. Here, we explore the “strings and binders switch” model to explain the origin and variety of chromatin behaviors that coexist and dynamically change wi...
Sources of CP violation from E{sub 6} inspired heterotic string model
Energy Technology Data Exchange (ETDEWEB)
Boussahel, M.; Mebarki, N. [Departement de physique Faculte des sciences Universite de M' sila 28000 (Algeria); Laboratoire de Physique Mathematique et Subatomique Mentouri University, Constantine (Algeria)
2012-06-27
Sources of the weak CP violation from the SU{sub L}(3)x SU{sub R}(3)x SU{sub c}(3) subgroup of the E{sub 6} inspired heterotic string model are discussed. It is shown that the number of the Cabibo-Kobayachi-Maskawa like matrices depends on the spontaneous breakdown of the E{sub 6} gauge symmetry and/or supersymmetry.
Clancy, Dominic; Feinstein, Alexander; Lidsey, James E.; Tavakol, Reza
1999-04-01
Global symmetries of the string effective action are employed to generate tilted, homogeneous Bianchi type VIh string cosmologies from a previously known stiff perfect fluid solution to Einstein gravity. The dilaton field is not constant on the surfaces of homogeneity. The future asymptotic state of the models is interpreted as a plane wave and is itself an exact solution to the string equations of motion to all orders in the inverse string tension. An inhomogeneous generalization of the Bianchi type III model is also found.
The stochastic string model as a unifying theory of the term structure of interest rates
Bueno-Guerrero, Alberto; Moreno, Manuel; Navas, Javier F.
2016-11-01
We present the stochastic string model of Santa-Clara and Sornette (2001), as reformulated by Bueno-Guerrero et al. (2015), as a unifying theory of the continuous-time modeling of the term structure of interest rates. We provide several new results, such as: (a) an orthogonality condition for the volatilities in the Heath, Jarrow, and Morton (1992) (HJM) model, (b) the interpretation of multi-factor HJM models as approximations to a full infinite-dimensional model, (c) a result of consistency based on Hilbert spaces, and (d) a theorem for option valuation.
Infrared Dynamics of a Large N QCD Model, the Massless String Sector and Mesonic Spectra
Dasgupta, Keshav; Mia, Mohammed; Richard, Michael; Trottier, Olivier
2014-01-01
A consistency check for any UV complete model for large N QCD should be, among other things, the existence of a well-defined vector and scalar mesonic spectra. In this paper, we use our UV complete model in type IIB string theory to study the IR dynamics and use this to predict the mesonic spectra in the dual type IIA side. The advantage of this approach is two-fold: not only will this justify the consistency of the supergravity approach, but it will also give us a way to compare the IR spectra and the model with the ones proposed earlier by Sakai and Sugimoto. Interestingly, the spectra coming from the massless stringy sector are independent of the UV physics, although the massive string sector may pose certain subtleties regarding the UV contributions as well as the mappings to actual QCD. Additionally, we find that a component of the string landscape enters the picture: there are points in the landscape where the spectra can be considerably improved over the existing results in the literature. These points...
A matrix model for heterotic Spin(32)/Z sub 2 and type I string theory
Krogh, M
1999-01-01
We consider heterotic string theories in the DLCQ. We derive that the matrix model of the Spin(32)/Z sub 2 heterotic theory is the theory living on N D-strings in type I wound on a circle with no Spin(32)/Z sub 2 Wilson line on the circle. This is an O(N) gauge theory. We rederive the matrix model for the E sub 8 xE sub 8 heterotic string theory, explicitly taking care of the Wilson line around the lightlike circle. The result is the same theory as for Spin(32)/Z sub 2 except that now there is a Wilson line on the circle. We also see that the integer N labeling the sector of the O(N) matrix model is not just the momentum around the lightlike circle, but a shifted momentum depending on the Wilson line. We discuss the aspect of level matching, GSO projections and why, from the point of view of matrix theory the E sub 8 xE sub 8 theory, and not the Spin(32)/Z sub 2 , develops an 11th dimension for strong coupling. Furthermore a matrix theory for type I is derived. This is again the O(N) theory living on the D-st...
Exact string theory model of closed timelike curves and cosmological singularities
Johnson, Clifford V.; Svendsen, Harald G.
2004-12-01
We study an exact model of string theory propagating in a space-time containing regions with closed timelike curves (CTCs) separated from a finite cosmological region bounded by a big bang and a big crunch. The model is an nontrivial embedding of the Taub-NUT geometry into heterotic string theory with a full conformal field theory (CFT) definition, discovered over a decade ago as a heterotic coset model. Having a CFT definition makes this an excellent laboratory for the study of the stringy fate of CTCs, the Taub cosmology, and the Milne/Misner-type chronology horizon which separates them. In an effort to uncover the role of stringy corrections to such geometries, we calculate the complete set of α' corrections to the geometry. We observe that the key features of Taub-NUT persist in the exact theory, together with the emergence of a region of space with Euclidean signature bounded by timelike curvature singularities. Although such remarks are premature, their persistence in the exact geometry is suggestive that string theory is able to make physical sense of the Milne/Misner singularities and the CTCs, despite their pathological character in general relativity. This may also support the possibility that CTCs may be viable in some physical situations, and may be a natural ingredient in pre-big bang cosmological scenarios.
De Sitter vacua and inflation in no-scale string models
Energy Technology Data Exchange (ETDEWEB)
Gross, Christian
2009-09-15
This thesis studies the question of how de Sitter vacua and slow-roll inflation may be realized in string-motivated models. More specifically, we consider 4d N = 1 supergravity theories (without vector multiplets) with Kaehler potentials which are 'no-scale' at leading order. Such theories frequently arise in the moduli sector of string compactifications. We discuss a condition on the scalar geometry (defined by the Kaehler potential) and on the direction of supersymmetry breaking in the scalar manifold, which has to be met in order for the average of the masses of the sGoldstinos to be positive, and hence for metastable vacua to be possible. This condition also turns out to be necessary for the existence of trajectories admitting slow-roll inflation. Its implications for certain scalar manifolds which arise from Calabi-Yau string compactifications are discussed. In particular, for two-moduli models arising from compactifications of heterotic- and type IIB string theory, a simple criterion on the intersection numbers needs to be satisfied for possible de Sitter phases to exist. In addition, we show that subleading corrections breaking the no-scale property may allow the condition on the scalar geometry to be fulfilled, even when it is violated at leading order. Finally, we develop a procedure to construct superpotentials for a given viable Kaehler potential, such that the scalar potential has a realistic local minimum. We propose two-moduli models, with superpotentials which could arise from flux backgrounds and non-perturbative effects, which have a viable vacuum without employing subleading corrections or an uplifting sector. (orig.)
Testing ocean tide models using GGP superconducting gravimeter observations
Baker, T.; Bos, M.
2003-04-01
Observations from the global network of superconducting gravimeters in the Global Geodynamics Project (GGP) are used to test 10 ocean tide models (SCHW; FES94.1, 95.2, 98, 99; CSR3.0, 4.0; TPXO.5; GOT99.2b; and NAO.99b). In addition, observations are used from selected sites with LaCoste and Romberg gravimeters with electrostatic feedback, where special attention has been given to achieving a calibration accuracy of 0.1%. In Europe, there are several superconducting gravimeter stations in a relatively small area and this can be used to advantage in testing the ocean (and body) tide models and in identifying sites with anomalous observations. At some of the superconducting gravimeter sites there are anomalies in the in-phase components of the main tidal harmonics, which are due to calibration errors of up to 0.3%. It is shown that the recent ocean tide models are in better agreement with the tidal gravity observations than were the earlier models of Schwiderski and FES94.1. However, no single ocean tide model gives completely satisfactory results in all areas of the world. For example, for M2 the TPXO.5 and NAO99b models give anomalous results in Europe, whereas the FES95.2, FES98 and FES99 models give anomalous results in China and Japan. It is shown that the observations from this improved set of tidal gravity stations will provide an important test of the new ocean tide models that will be developed in the next few years. For further details see Baker, T.F. and Bos, M.S. (2003). "Validating Earth and ocean tide models using tidal gravity measurements", Geophysical Journal International, 152.
Institute of Scientific and Technical Information of China (English)
Anirudh Pradhan
2011-01-01
The present study deals with a spatially homogeneous and anisotropic Bianchi-I cosmological models representing massive strings with magnetic field and decaying vacuum energy density A. The energy-momentum tensor,as formulated by Letelier (1983), has been used to construct massive string cosmological models for which we assume the expansion scalar in the models is proportional to one of the components of shear tensor. The Einstein's field equations have been solved by applying a variation law for generalized Hubble's parameter in Bianchi-I space-time. The variation law for Hubble's parameter generates two types of solutions for the average scale factor, one is of power-law type and other is of the exponential form. Using these two forms, Einstein's field equations are solved separately that correspond to expanding singular and non-singular models of the universe respectively. We have made a comparative study of accelerating and decelerating models in the presence of string scenario. The study reveals that massive strings dominate in the decelerating universe whereas strings dominate in the accelerating universe. The strings eventually disappear from the universe for sufficiently large times, which is in agreement with current astronomical observations. The cosmological constant A is found to be a positive decreasing function of time which is corroborated by results from recent supernovae Ia observations. The physical and geometric properties of the models have been also discussed in detail.
Early structure formation with cold plus hot dark matter a success of strings plus inflation model
Battye, R A; Weller, J; Battye, Richard A.; Magueijo, Joao; Weller, Jochen
1999-01-01
Quantum fluctuations created during inflation can account for the observed matter distribution in the linear regime if the universe has two components of dark matter, one which is cold and collisionless, and the other which is hot and free streams on small scales. However, this free streaming property of the hot component prevents early structure formation, and since objects, such as damped Lyman-$\\alpha$ systems, have been observed at high redshift, it is necessary to produce more power on small scales. Here, we show that the situation can be improved substantially in models where cosmic strings are formed at the end of inflation, and in which both inflation and strings participate in the generation of structure.
LRS Bianchi Type II Massive String Cosmological Models with Magnetic Field in Lyra's Geometry
Directory of Open Access Journals (Sweden)
Raj Bali
2013-01-01
Full Text Available Bianchi type II massive string cosmological models with magnetic field and time dependent gauge function ( in the frame work of Lyra's geometry are investigated. The magnetic field is in -plane. To get the deterministic solution, we have assumed that the shear ( is proportional to the expansion (. This leads to , where and are metric potentials and is a constant. We find that the models start with a big bang at initial singularity and expansion decreases due to lapse of time. The anisotropy is maintained throughout but the model isotropizes when . The physical and geometrical aspects of the model in the presence and absence of magnetic field are also discussed.
LHC Phenomenology and Cosmology of String-Inspired Intersecting D-Brane Models
Anchordoqui, Luis A; Goldberg, Haim; Huang, Xing; Lust, Dieter; Taylor, Tomasz R; Vlcek, Brian
2012-01-01
We discuss the phenomenology and cosmology of a Standard-like Model inspired by string theory, in which the gauge fields are localized on D-branes wrapping certain compact cycles on an underlying geometry, whose intersection can give rise to chiral fermions. The energy scale associated with string physics is assumed to be near the Planck mass. To develop our program in the simplest way, we work within the construct of a minimal model with gauge-extended sector U (3)_B \\times Sp (1)_L \\times U (1)_{I_R} \\times U (1)_L. The resulting U (1) content gauges the baryon number B, the lepton number L, and a third additional abelian charge I_R which acts as the third isospin component of an SU(2)_R. All mixing angles and gauge couplings are fixed by rotation of the U(1) gauge fields to a basis diagonal in hypercharge Y and in an anomaly free linear combination of I_R and B-L. The anomalous $Z'$ gauge boson obtains a string scale St\\"uckelberg mass via a 4D version of the Green-Schwarz mechanism. To keep the realizatio...
Semiclassical models for uniform-density Cosmic Strings and Relativistic Stars
Campanelli, M; Campanelli, Manuela; Lousto, Carlos O.
1996-01-01
In this paper we show how quantum corrections, although perturbatively small, may play an important role in the analysis of the existence of some classical models. This, in fact, appears to be the case of static, uniform--density models of the interior metric of cosmic strings and neutron stars. We consider the fourth order semiclassical equations and first look for perturbative solutions in the coupling constants $\\alpha$ and $\\beta$ of the quadratic curvature terms in the effective gravitational Lagrangian. We find that there is not a consistent solution; neither for strings nor for spherical stars. We then look for non--perturbative solutions and find an explicit approximate metric for the case of straight cosmic strings. We finally analyse the contribution of the non--local terms to the renormalized energy--momentum tensor and the possibility of this terms to allow for a perturbative solution. We explicitly build up a particular renormalized energy--momentum tensor to fulfill that end. These state--depend...
Unitary-matrix models as exactly solvable string theories
Periwal, Vipul; Shevitz, Danny
1990-01-01
Exact differential equations are presently found for the scaling functions of models of unitary matrices which are solved in a double-scaling limit, using orthogonal polynomials on a circle. For the case of the simplest, k = 1 model, the Painleve II equation with constant 0 is obtained; possible nonperturbative phase transitions exist for these models. Equations are presented for k = 2 and 3, and discussed with a view to asymptotic behavior.
Unitary-matrix models as exactly solvable string theories
Periwal, Vipul; Shevitz, Danny
1990-01-01
Exact differential equations are presently found for the scaling functions of models of unitary matrices which are solved in a double-scaling limit, using orthogonal polynomials on a circle. For the case of the simplest, k = 1 model, the Painleve II equation with constant 0 is obtained; possible nonperturbative phase transitions exist for these models. Equations are presented for k = 2 and 3, and discussed with a view to asymptotic behavior.
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...
Cosmic Strings and Superstrings
Copeland, Edmund J
2009-01-01
Cosmic strings are predicted by many field-theory models, and may have been formed at a symmetry-breaking transition early in the history of the universe, such as that associated with grand unification. They could have important cosmological effects. Scenarios suggested by fundamental string theory or M-theory, in particular the popular idea of brane inflation, also strongly suggest the appearance of similar structures. Here we review the reasons for postulating the existence of cosmic strings or superstrings, the various possible ways in which they might be detected observationally, and the special features that might discriminate between ordinary cosmic strings and superstrings.
Road to room-temperature superconductivity: A universal model
Bucher, Manfred
2013-01-01
In a semiclassical view superconductivity is attributed exclusively to the advance of atoms' outer s electrons through the nuclei of neighbor atoms in a solid. The necessary progression of holes in the opposite direction has the electric and magnetic effect as if two electrons were advancing instead of each actual one. Superconductivity ceases when the associated lateral oscillation of the outer s electrons extends between neighbor atoms. If such overswing occurs already at T = 0, then the material is a normal conductor. Otherwise, lateral overswing can be caused by lattice vibrations at a critical temperature Tc or by a critical magnetic field Bc. Lateral electron oscillations are reduced - and Tc is increased - when the atoms of the outer s electrons are squeezed, be it in the bulk crystal, in a thin film, or under external pressure on the sample. The model is applied to alkali metals and alkali-doped fullerenes. Aluminum serves as an example of a simple metal with superconductivity. Application of the mode...
String fragmentation model and inclusive production of K mesons
Energy Technology Data Exchange (ETDEWEB)
Aleem, F.E.; Saleem, M.; Rafique, M. (Punjab Univ., Lahore (Pakistan))
1992-06-30
In this paper an account of the inclusive production of K mesons in electron-positron annihilation is given. The most recent measurements on the cross section are exhibited and compared with the predictions of the Lund model. The model gives a satisfactory agreement with the experimental data. The result from different experiments on cross section, the mean multiplicity per multihadronic event and various other characteristics are found to be consistent.
Institute of Scientific and Technical Information of China (English)
BALI Raj; PAREEK Umesh Kumar; PRADHAN Anirudh
2007-01-01
@@ Bianchi type-Ⅰ massive string cosmological model with magnetic field of barotropic perfect fluid distribution through the techniques used by Latelier and Stachel is investigated. To obtain the deterministic model of the universe, it is assumed that the universe is filled with barotropic perfect fluid distribution. The magnetic field is due to electric current produced along the x-axis with infinite electrical condúctivity. The behaviour of the model in the presence and absence of magnetic field together with other physical aspects is further discussed.
On spinors, strings, integrable models and decomposed Yang-Mills theory
Ioannidou, Theodora; Niemi, Antti J
2014-01-01
This paper deals with various interrelations between strings and surfaces in three dimensional ambient space, two dimensional integrable models and two dimensional and four dimensional decomposed SU(2) Yang-Mills theories. Initially, a spinor version of the Frenet equation is introduced in order to describe the differential geometry of static three dimensional string-like structures. Then its relation to the structure of the su(2) Lie algebra valued Maurer-Cartan one-form is presented; while by introducing time evolution of the string a Lax pair is obtained, as an integrability condition. In addition, it is show how the Lax pair of the integrable nonlinear Schroedinger equation becomes embedded into the Lax pair of the time extended spinor Frenet equation and it is described how a spinor based projection operator formalism can be used to construct the conserved quantities, in the case of the nonlinear Schroedinger equation. Then the Lax pair structure of the time extended spinor Frenet equation is related to ...
2-D Electromagnetic Model of Fast-Ramping Superconducting Magnets
Auchmann, B; Kurz, S; Russenschuck, Stephan
2006-01-01
Fast-ramping superconducting (SC) accelerator magnets are the subject of R&D efforts by magnet designers at various laboratories. They require modifications of magnet design tools such as the ROXIE program at CERN, i.e. models of dynamic effects in superconductors need to be implemented and validated. In this paper we present the efforts towards a dynamic 2-D simulation of fast-ramping SC magnets with the ROXIE tool. Models are introduced and simulation results are compared to measurements of the GSI001 magnet of a GSI test magnet constructed and measured at BNL.
Quench modeling of the ATLAS superconducting toroids
Gavrilin, A V; ten Kate, H H J
2001-01-01
Details of the normal zone propagation and the temperature distribution in the coils of ATLAS toroids under quench are presented. A tailor-made mathematical model and corresponding computer code enable obtainment of computational results for the propagation process over the coils in transverse (turn-to-turn) and longitudinal directions. The slow electromagnetic diffusion into the pure aluminum stabilizer of the toroid's conductor, as well as the essentially transient heat transfer through inter-turn insulation, is appropriately included in the model. The effect of nonuniform distribution of the magnetic field and the thermal links to the coil casing on the temperature gradients within the coils is analyzed in full. (5 refs).
Iteration schemes for parallelizing models of superconductivity
Energy Technology Data Exchange (ETDEWEB)
Gray, P.A. [Michigan State Univ., East Lansing, MI (United States)
1996-12-31
The time dependent Lawrence-Doniach model, valid for high fields and high values of the Ginzburg-Landau parameter, is often used for studying vortex dynamics in layered high-T{sub c} superconductors. When solving these equations numerically, the added degrees of complexity due to the coupling and nonlinearity of the model often warrant the use of high-performance computers for their solution. However, the interdependence between the layers can be manipulated so as to allow parallelization of the computations at an individual layer level. The reduced parallel tasks may then be solved independently using a heterogeneous cluster of networked workstations connected together with Parallel Virtual Machine (PVM) software. Here, this parallelization of the model is discussed and several computational implementations of varying degrees of parallelism are presented. Computational results are also given which contrast properties of convergence speed, stability, and consistency of these implementations. Included in these results are models involving the motion of vortices due to an applied current and pinning effects due to various material properties.
A Morphographemic Model for Error Correction in Nonconcatenative Strings
Bowden, T; Bowden, Tanya; Kiraz, George Anton
1995-01-01
This paper introduces a spelling correction system which integrates seamlessly with morphological analysis using a multi-tape formalism. Handling of various Semitic error problems is illustrated, with reference to Arabic and Syriac examples. The model handles errors vocalisation, diacritics, phonetic syncopation and morphographemic idiosyncrasies, in addition to Damerau errors. A complementary correction strategy for morphologically sound but morphosyntactically ill-formed words is outlined.
Non-String Pursuit towards Unified Model on the Lattice
Kawamoto, N
1999-01-01
Non-standard overview on the possible formulation towards a unified model on the lattice is presented. It is based on the generalized gauge theory which is formulated by differential forms and thus expected to fit in a simplicial manifold. We first review suggestive known results towards this direction. As a small step of concrete realization of the program, we propose a lattice Chern-Simons gravity theory which leads to the Chern-Simons gravity in the continuum limit via Ponzano-Regge model. We then summarize the quantization procedure of the generalized gauge theory and apply the formulation to the generalized topological Yang-Mills action with instanton gauge fixing. We find N=2 super Yang-Mills theory with Dirac-K{ä}hler fermions which are generated from ghosts via twisting mechanism. The Weinberg-Salam model is formulated by the generalized Yang-Mills action which includes Connes's non-commutative geometry formulation as a particular case. In the end a possible scenario to realize the program is propose...
Top quark mass in exophobic Pati-Salam heterotic string model
Energy Technology Data Exchange (ETDEWEB)
Christodoulides, Kyriakos [Dept. of Mathematical Sciences, University of Liverpool, Liverpool L69 7ZL (United Kingdom); Faraggi, Alon E., E-mail: faraggi@amtp.liv.ac.uk [Dept. of Mathematical Sciences, University of Liverpool, Liverpool L69 7ZL (United Kingdom); Rizos, John [Department of Physics, University of Ioannina, GR45110 Ioannina (Greece)
2011-08-03
We analyse the phenomenology of an exemplary exophobic Pati-Salam heterotic string vacuum, in which no exotic fractionally charged states exist in the massless string spectrum. Our model also contains the Higgs representations that are needed to break the gauge symmetry to that of the Standard Model and to generate fermion masses at the electroweak scale. We show that the requirement of a leading mass term for the heavy generation, which is not degenerate with the mass terms of the lighter generations, places an additional strong constraint on the viability of the models. In many models a top quark Yukawa may not exist at all, whereas in others two or more generations may obtain a mass term at leading order. In our exemplary model a mass term at leading order exist only for one family. Additionally, we demonstrate the existence of supersymmetric F- and D-flat directions that give heavy mass to all the colour triplets beyond those of the Standard Model and leave one pair of electroweak Higgs doublets light. Hence, below the Pati-Salam breaking scale, the matter states in our model that are charged under the observable gauge symmetries, consist solely of those of the Minimal Supersymmetric Standard Model.
Cellular Approach to Long-Range $p_t$ and Multiplicity Correlations in the String Fusion Model
Vechernin, V V
2003-01-01
The long-range $p_t$ and multiplicity($n$) correlations in high-energy nuclear collisions are studied in the framework of a simple cellular analog of the string fusion model. Two cases with local and global string fusion is considered. The $p_t$--$n$ and $n$--$n$ correlation functions and correlation coefficients are calculated analytically in some asymptotic cases using suggested Gauss approximation. It's shown that at large string density the $p_t$--$n$ and $n$--$n$ correlation coefficients are connected and the scaling takes place. The behavior of the correlations at small string density is also studied. The asymptotic results are compared with results of the numerical calculations in the framework of proposed cellular approach.
Doubled strings, negative strings and null waves
Blair, Chris D A
2016-01-01
We revisit the fundamental string (F1) solution in the doubled formalism. We show that the wave-like solution of double field theory (DFT) corresponding to the F1/pp-wave duality pair is more properly a solution of the DFT action coupled to a doubled sigma model action. The doubled string configuration which sources the pp-wave can be thought of as static gauge with the string oriented in a dual direction. We also discuss the DFT solution corresponding to a vibrating string, carrying both winding and momentum. We further show that the solution dual to the F1 in both time and space can be viewed as a "negative string" solution. Negative branes are closely connected to certain exotic string theories which involve unusual signatures for both spacetime and brane worldvolumes. In order to better understand this from the doubled point of view, we construct a variant of DFT suitable for describing theories in which the fundamental string has a Euclidean worldsheet, for which T-dualities appear to change the spacetim...
de Boer, J.; de Medeiros, P.; El-Showk, S.; Sinkovics, A.
2008-01-01
We consider an open string version of the topological twist previously proposed for sigma-models with G(2) target spaces. We determine the cohomology of open strings states and relate these to geometric deformations of calibrated submanifolds and to flat or anti-self-dual connections on such submani
Bianchi Type V magnetized string dust cosmological models with Petrov-type degenerate
Indian Academy of Sciences (India)
Raj Bali; Umesh K Pareek
2009-05-01
Bianchi Type V massive string cosmological models with free gravitational field of Petrov Type degenerate in the presence of magnetic field with variable magnetic permeability are investigated. The magnetic field is due to an electric current produced along the -axis. The 23 is the only non-vanishing component of electromagnetic field tensor . Maxwell's equations [;] = 0 and $F_{ij}^{ij} = 0$ are satisfied by 23 = constant. The behaviour of the model in the presence and absence of magnetic field and other physical aspects are also discussed.
LRS Bianchi type-I string cosmological model in f(R, T) gravity
Energy Technology Data Exchange (ETDEWEB)
Sahoo, Pradyumn [Department of Mathematics, Birla Institute of Technology and Science-Pilani, Hyderabad (India)
2016-04-15
In this study the locally rotationally symmetric (LRS) Bianchi type-I (BI) cosmological model has been investigated in the presence of one dimensional cosmic strings in f(R, T) gravity. The exact solutions of the field equations are obtained through the use of constant deceleration parameter [1] and the scalar expansion is proportional to the shear scalar. Considering the accelerating nature of the universe in the present epoch, the physical behavior of the model has been discussed. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Elliptic flow in a hadron-string cascade model at 130 GeV energy
Indian Academy of Sciences (India)
P K Sahu; A Ohnishi; M Isse; N Otuka; S C Phatak
2006-08-01
We present the analysis of elliptic flow at $\\sqrt{s} = 130$ A GeV energy in a hadron-string cascade model. We find that the final hadronic yields are qualitatively described. The elliptic flow 2 is reasonably well-described at low transverse momentum (T < 1 GeV/c) in mid-central collisions. On the other hand, this model does not explain 2 at high T or in peripheral collisions and thus generally, it underestimates the elliptic flow at RHIC energy.
Stable charged cosmic strings.
Weigel, H; Quandt, M; Graham, N
2011-03-11
We study the quantum stabilization of a cosmic string by a heavy fermion doublet in a reduced version of the standard model. We show that charged strings, obtained by populating fermionic bound state levels, become stable if the electroweak bosons are coupled to a fermion that is less than twice as heavy as the top quark. This result suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model. Numerically we find the most favorable string profile to be a simple trough in the Higgs vacuum expectation value of radius ≈10(-18) m. The vacuum remains stable in our model, because neutral strings are not energetically favored.
Renormalization group approach to a p-wave superconducting model
Energy Technology Data Exchange (ETDEWEB)
Continentino, Mucio A.; Deus, Fernanda [Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud, 150, Urca 22290-180, Rio de Janeiro, RJ (Brazil); Caldas, Heron [Departamento de Ciências Naturais, Universidade Federal de São João Del Rei, 36301-000, São João Del Rei, MG (Brazil)
2014-04-01
We present in this work an exact renormalization group (RG) treatment of a one-dimensional p-wave superconductor. The model proposed by Kitaev consists of a chain of spinless fermions with a p-wave gap. It is a paradigmatic model of great actual interest since it presents a weak pairing superconducting phase that has Majorana fermions at the ends of the chain. Those are predicted to be useful for quantum computation. The RG allows to obtain the phase diagram of the model and to study the quantum phase transition from the weak to the strong pairing phase. It yields the attractors of these phases and the critical exponents of the weak to strong pairing transition. We show that the weak pairing phase of the model is governed by a chaotic attractor being non-trivial from both its topological and RG properties. In the strong pairing phase the RG flow is towards a conventional strong coupling fixed point. Finally, we propose an alternative way for obtaining p-wave superconductivity in a one-dimensional system without spin–orbit interaction.
Masses and Internal Structure of Mesons in the String Quark Model
Soloviev, L D
2000-01-01
The relativistic quantum string quark model, proposed earlier, is applied to all mesons, from pion to $\\Upsilon$, lying on the leading Regge trajectories (i.e., to the lowest radial excitations in terms of the potential quark models). The model describes the meson mass spectrum, and comparison with measured meson masses allows one to determine the parameters of the model: current quark masses, universal string tension, and phenomenological constants describing nonstring short-range interaction. The meson Regge trajectories are in general nonlinear; practically linear are only trajectories for light-quark mesons with non-zero lowest spins. The model predicts masses of many new higher-spin mesons. A new $K^*(1^-)$ meson is predicted with mass 1910 Mev. In some cases the masses of new low-spin mesons are predicted by extrapolation of the phenomenological short-range parameters in the quark masses. In this way the model predicts the mass of $\\eta_b(1S)(0^{-+})$ to be $9500\\pm 30$ MeV, and the mass of $B_c(0^-)$ t...
The 750 GeV diphoton LHC excess and Extra Z's in Heterotic-String Derived Models
Faraggi, Alon E
2016-01-01
The ATLAS and CMS collaborations recently recorded possible di-photon excess at 750 GeV and a less significant di-boson excess around 1.9 TeV. Such excesses may be produced in heterotic-string derived Z' models, where the di-photon excess may be connected with the Standard Model singlet scalar responsible for the Z' symmetry breaking, whereas the di-boson excess arises from production of the extra vector boson. Additional vector-like states in the string Z' model are instrumental to explain the relatively large width of the di-photon events and mandated by anomaly cancellation to be in the vicinity of the Z' breaking scale. Wilson line breaking of the non-Abelian gauge symmetries in the string models naturally gives rise to dark matter candidates. Future collider experiments will discriminate between the high-scale heterotic-string models, which preserve the perturbative unification paradigm indicated by the Standard Model data, versus the low scale string models. We also discuss the possibility for the produ...
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,...
Theory, modeling and simulation of superconducting qubits
Energy Technology Data Exchange (ETDEWEB)
Berman, Gennady P [Los Alamos National Laboratory; Kamenev, Dmitry I [Los Alamos National Laboratory; Chumak, Alexander [INSTIT OF PHYSICS, KIEV; Kinion, Carin [LLNL; Tsifrinovich, Vladimir [POLYTECHNIC INSTIT OF NYU
2011-01-13
We analyze the dynamics of a qubit-resonator system coupled with a thermal bath and external electromagnetic fields. Using the evolution equations for the set of Heisenberg operators that describe the whole system, we derive an expression for the resonator field, that includes the resonator-drive, the resonator-bath, and resonator-qubit interactions. The renormalization of the resonator frequency, caused by the qubit-resonator interaction, is accounted for. Using the solutions for the resonator field, we derive the equation that describes the qubit dynamics. The dependence of the qubit evolution during the measurement time on the fidelity of a single-shot measurement is studied. The relation between the fidelity and measurement time is shown explicitly. We proposed a novel adiabatic method for the phase qubit measurement. The method utilizes a low-frequency, quasi-classical resonator inductively coupled to the qubit. The resonator modulates the qubit energy, and the back reaction of the qubit causes a shift in the phase of the resonator. The resonator phase shift can be used to determine the qubit state. We have simulated this measurement taking into the account the energy levels outside the phase qubit manifold. We have shown that, for qubit frequencies in the range of 8-12GHZ, a resonator frequency of 500 MHz and a measurement time of 100 ns, the phase difference between the two qubit states is greater than 0.2 rad. This phase difference exceeds the measurement uncertainty, and can be detected using a classical phase-meter. A fidelity of 0.9999 can be achieved for a relaxation time of 0.5 ms. We also model and simulate a microstrip-SQUID amplifier of frequency about 500 MHz, which could be used to amplify the resonator oscillations in the phase qubit adiabatic measurement. The voltage gain and the amplifier noise temperature are calculated. We simulate the preparation of a generalized Bell state and compute the relaxation times required for achieving high
Theory, modeling and simulation of superconducting qubits
Energy Technology Data Exchange (ETDEWEB)
Berman, Gennady P [Los Alamos National Laboratory; Kamenev, Dmitry I [Los Alamos National Laboratory; Chumak, Alexander [INSTIT OF PHYSICS, KIEV; Kinion, Carin [LLNL; Tsifrinovich, Vladimir [POLYTECHNIC INSTIT OF NYU
2011-01-13
We analyze the dynamics of a qubit-resonator system coupled with a thermal bath and external electromagnetic fields. Using the evolution equations for the set of Heisenberg operators that describe the whole system, we derive an expression for the resonator field, that includes the resonator-drive, the resonator-bath, and resonator-qubit interactions. The renormalization of the resonator frequency, caused by the qubit-resonator interaction, is accounted for. Using the solutions for the resonator field, we derive the equation that describes the qubit dynamics. The dependence of the qubit evolution during the measurement time on the fidelity of a single-shot measurement is studied. The relation between the fidelity and measurement time is shown explicitly. We proposed a novel adiabatic method for the phase qubit measurement. The method utilizes a low-frequency, quasi-classical resonator inductively coupled to the qubit. The resonator modulates the qubit energy, and the back reaction of the qubit causes a shift in the phase of the resonator. The resonator phase shift can be used to determine the qubit state. We have simulated this measurement taking into the account the energy levels outside the phase qubit manifold. We have shown that, for qubit frequencies in the range of 8-12GHZ, a resonator frequency of 500 MHz and a measurement time of 100 ns, the phase difference between the two qubit states is greater than 0.2 rad. This phase difference exceeds the measurement uncertainty, and can be detected using a classical phase-meter. A fidelity of 0.9999 can be achieved for a relaxation time of 0.5 ms. We also model and simulate a microstrip-SQUID amplifier of frequency about 500 MHz, which could be used to amplify the resonator oscillations in the phase qubit adiabatic measurement. The voltage gain and the amplifier noise temperature are calculated. We simulate the preparation of a generalized Bell state and compute the relaxation times required for achieving high
Directory of Open Access Journals (Sweden)
Kovalenko Vladimir
2017-01-01
Full Text Available Long-range multiplicity correlations in intervals separated in pseudorapidity and azimuth are studied in the framework of string fusion approach. We applied a Monte Carlo model, in which the string configurations in the transverse plane and rapidity are simulating event-by-event. The string interaction is realized in the lattice string fusion approach with introduction of a grid in the transverse plane. We assumed that the azimuthal anisotropy of particle production is caused by parton energy loss traveling trough the media formed by clusters of fused strings : Δpt/Δx = −α(pt √η2/3, where η is a string density. In the cellular approach the Bresenham’s line algorithm has been applied. It is obtained that in AA collisions, the parton energy loss seems to play considerable role, in particular, by providing large contribution to the correlation of mean transverse momentum with multiplicity. The developed approach provides non-zero values flows in p-Pb collisions at LHC energies and produces the pattern similar to the one of the experimental di-hadron analysis.
Kovalenko, Vladimir
2017-03-01
Long-range multiplicity correlations in intervals separated in pseudorapidity and azimuth are studied in the framework of string fusion approach. We applied a Monte Carlo model, in which the string configurations in the transverse plane and rapidity are simulating event-by-event. The string interaction is realized in the lattice string fusion approach with introduction of a grid in the transverse plane. We assumed that the azimuthal anisotropy of particle production is caused by parton energy loss traveling trough the media formed by clusters of fused strings : Δpt/Δx = -α(pt √η)2/3, where η is a string density. In the cellular approach the Bresenham's line algorithm has been applied. It is obtained that in AA collisions, the parton energy loss seems to play considerable role, in particular, by providing large contribution to the correlation of mean transverse momentum with multiplicity. The developed approach provides non-zero values flows in p-Pb collisions at LHC energies and produces the pattern similar to the one of the experimental di-hadron analysis.
Leptogenesis in the Light of Super-Kamiokande Data and a Realistic String Model
Ellis, Jonathan Richard; Nanopoulos, Dimitri V; Ellis, John
1999-01-01
We discuss leptogenesis in the light of indications of neutrino masses and mixings from Super-Kamiokande and other data on atmospheric neutrinos, as well as the solar neutrino deficit. Neutrino masses and mixings consistent with these data may produce in a natural and generic way a lepton asymmetry that is suffient to provide the observed baryon asymmetry, after processing via non-perturbative electroweak effects. We illustrate this discussion in the framework of the string-derived flipped SU(5) model, using particle assignments and choices of vacuum parameters that are known to give realistic masses to quarks and charged leptons. We display one scenario for neutrino masses that also accommodates leptogenesis.
Two dimensional black-hole as a topological coset model of c=1 string theory
Mukhi, S
1993-01-01
We show that a special superconformal coset (with $\\hat c =3$) is equivalent to $c=1$ matter coupled to two dimensional gravity. This identification allows a direct computation of the correlation functions of the $c=1$ non-critical string to all genus, and at nonzero cosmological constant, directly from the continuum approach. The results agree with those of the matrix model. Moreover we connect our coset with a twisted version of a Euclidean two dimensional black hole, in which the ghost and matter systems are mixed.
Regularities in hadron systematics, Regge trajectories and a string quark model
Energy Technology Data Exchange (ETDEWEB)
Chekanov, S.V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Levchenko, B.B. [Moscow State Univ. (Russian Federation). Skobeltsyn Inst. of Nuclear Physics
2006-08-15
An empirical principle for the construction of a linear relationship between the total angular momentum and squared-mass of baryons is proposed. In order to examine linearity of the trajectories, a rigorous least-squares regression analysis was performed. Unlike the standard Regge-Chew-Frautschi approach, the constructed trajectories do not have non-linear behaviour. A similar regularity may exist for lowest-mass mesons. The linear baryonic trajectories are well described by a semi-classical picture based on a spinning relativistic string with tension. The obtained numerical solution of this model was used to extract the (di)quark masses. (orig.)
Color-symmetric superconductivity in a phenomenological QCD model
DEFF Research Database (Denmark)
Bohr, Henrik; Providencia, C.; Providencia, J. da
2009-01-01
In this paper, we construct a theory of the NJL type where superconductivity is present, and yet the superconducting state remains, in the average, color symmetric. This shows that the present approach to color superconductivity is consistent with color singletness. Indeed, quarks are free...... in the deconfined phase, but the deconfined phase itself is believed to be a color singlet. The usual description of the color superconducting state violates color singletness. On the other hand, the color superconducting state here proposed is color symmetric in the sense that an arbitrary color rotation leads...
Toda Theories, Matrix Models, Topological Strings, and N=2 Gauge Systems
Dijkgraaf, Robbert
2009-01-01
We consider the topological string partition function, including the Nekrasov deformation, for type IIB geometries with an A_{n-1} singularity over a Riemann surface. These models realize the N=2 SU(n) superconformal gauge systems recently studied by Gaiotto and collaborators. Employing large N dualities we show why the partition function of topological strings in these backgrounds is captured by the chiral blocks of A_{n-1} Toda systems and derive the dictionary recently proposed by Alday, Gaiotto and Tachikawa. For the case of genus zero Riemann surfaces, we show how these systems can also be realized by Penner-like matrix models with logarithmic potentials. The Seiberg-Witten curve can be understood as the spectral curve of these matrix models which arises holographically at large N. In this context the Nekrasov deformation maps to the beta-ensemble of generalized matrix models, that in turn maps to the Toda system with general background charge. We also point out the notion of a double holography for this...
Exploring cosmic strings: Observable effects and cosmological constraints
Sabancilar, Eray
Observation of cosmic (super)strings can serve as a useful hint to understand the fundamental theories of physics, such as grand unified theories (GUTs) and/or superstring theory. In this regard, I present new mechanisms to produce particles from cosmic (super)strings, and discuss their cosmological and observational effects in this dissertation. The first chapter is devoted to a review of the standard cosmology, cosmic (super)strings and cosmic rays. The second chapter discusses the cosmological effects of moduli. Moduli are relatively light, weakly coupled scalar fields, predicted in supersymmetric particle theories including string theory. They can be emitted from cosmic (super)string loops in the early universe. Abundance of such moduli is constrained by diffuse gamma ray background, dark matter, and primordial element abundances. These constraints put an upper bound on the string tension as strong as Gmu ≲ 10-28 for a wide range of modulus mass m. If the modulus coupling constant is stronger than gravitational strength, modulus radiation can be the dominant energy loss mechanism for the loops. Furthermore, modulus lifetimes become shorter for stronger coupling. Hence, the constraints on string tension Gmu and modulus mass m are significantly relaxed for strongly coupled moduli predicted in superstring theory. Thermal production of these particles and their possible effects are also considered. In the third chapter, moduli emitted from cosmic string cusps are studied. Highly boosted modulus bursts emanating from cusps subsequently decay into gluons and generate hadronic cascades which in turn produce large number of neutrinos. For reasonable values of the modulus mass and coupling constant, observable ultra high energy neutrino fluxes can be produced for a wide range of string tension Gmu. The fourth chapter discusses cosmic rays produced by the charged particles ejected from cusps of superconducting cosmic strings. In many particle physics theories, cosmic
Symmetry-enriched string nets: Exactly solvable models for SET phases
Heinrich, Chris; Burnell, Fiona; Fidkowski, Lukasz; Levin, Michael
2016-12-01
We construct exactly solvable models for a wide class of symmetry-enriched topological (SET) phases. Our construction applies to two-dimensional (2D) bosonic SET phases with finite unitary on-site symmetry group G and we conjecture that our models realize every phase in this class that can be described by a commuting projector Hamiltonian. Our models are designed so that they have a special property: If we couple them to a dynamical lattice gauge field with gauge group G , the resulting gauge theories are equivalent to string-net models. This property is what allows us to analyze our models in generality. As an example, we present a model for a phase with the same anyon excitations as the toric code and with a Z2 symmetry which exchanges the e and m type anyons. We further illustrate our construction with a number of additional examples.
Models of Particle Physics from Type IIB String Theory and F-theory: A Review
Maharana, Anshuman
2012-01-01
We review particle physics model building in type IIB string theory and F-theory. This is a region in the landscape where in principle many of the key ingredients required for a realistic model of particle physics can be combined successfully. We begin by reviewing moduli stabilisation within this framework and its implications for supersymmetry breaking. We then review model building tools and developments in the weakly coupled type IIB limit, for both local D3-branes at singularities and global models of intersecting D7-branes. Much of recent model building work has been in the strongly coupled regime of F-theory due to the presence of exceptional symmetries which allow for the construction of phenomenologically appealing Grand Unified Theories. We review both local and global F-theory model building starting from the fundamental concepts and tools regarding how the gauge group, matter sector and operators arise, and ranging to detailed phenomenological properties explored in the literature.
Supersymmetry and String Theory
Dine, Michael
2016-01-01
Preface to the first edition; Preface to the second edition; A note on choice of metric; Text website; Part I. Effective Field Theory: The Standard Model, Supersymmetry, Unification: 1. Before the Standard Model; 2. The Standard Model; 3. Phenomenology of the Standard Model; 4. The Standard Model as an effective field theory; 5. Anomalies, instantons and the strong CP problem; 6. Grand unification; 7. Magnetic monopoles and solitons; 8. Technicolor: a first attempt to explain hierarchies; Part II. Supersymmetry: 9. Supersymmetry; 10. A first look at supersymmetry breaking; 11. The Minimal Supersymmetric Standard Model; 12. Supersymmetric grand unification; 13. Supersymmetric dynamics; 14. Dynamical supersymmetry breaking; 15. Theories with more than four conserved supercharges; 16. More supersymmetric dynamics; 17. An introduction to general relativity; 18. Cosmology; 19. Astroparticle physics and inflation; Part III. String Theory: 20. Introduction; 21. The bosonic string; 22. The superstring; 23. The heterotic string; 24. Effective actions in ten dimensions; 25. Compactification of string theory I. Tori and orbifolds; 26. Compactification of string theory II. Calabi-Yau compactifications; 27. Dynamics of string theory at weak coupling; 28. Beyond weak coupling: non-perturbative string theory; 29. Large and warped extra dimensions; 30. The landscape: a challenge to the naturalness principle; 31. Coda: where are we headed?; Part IV. The Appendices: Appendix A. Two-component spinors; Appendix B. Goldstone's theorem and the pi mesons; Appendix C. Some practice with the path integral in field theory; Appendix D. The beta function in supersymmetric Yang-Mills theory; References; Index.
Supermassive cosmic string compactifications
Energy Technology Data Exchange (ETDEWEB)
Blanco-Pillado, Jose J.; Reina, Borja; Sousa, Kepa; Urrestilla, Jon, E-mail: josejuan.blanco@ehu.es, E-mail: borja.reina@ehu.es, E-mail: kepa.sousa@ehu.es, E-mail: jon.urrestilla@ehu.es [Department of Theoretical Physics and History of Science, University of the Basque Country UPV/EHU, 48080 Bilbao (Spain)
2014-06-01
The space-time dimensions transverse to a static straight cosmic string with a sufficiently large tension (supermassive cosmic strings) are compact and typically have a singularity at a finite distance form the core. In this paper, we discuss how the presence of multiple supermassive cosmic strings in the 4d Abelian-Higgs model can induce the spontaneous compactification of the transverse space and explicitly construct solutions where the gravitational background becomes regular everywhere. We discuss the embedding of this model in N = 1 supergravity and show that some of these solutions are half-BPS, in the sense that they leave unbroken half of the supersymmetries of the model.
Supermassive Cosmic String Compactifications
Blanco-Pillado, Jose J; Sousa, Kepa; Urrestilla, Jon
2014-01-01
The space-time dimensions transverse to a static straight cosmic string with a sufficiently large tension (supermassive cosmic strings) are compact and typically have a singularity at a finite distance form the core. In this paper, we discuss how the presence of multiple supermassive cosmic strings in the 4D Abelian-Higgs model can induce the spontaneous compactification of the transverse space and explicitly construct solutions where the gravitational background becomes regular everywhere. We discuss the embedding of this model in N=1 supergravity and show that some of these solutions are half-BPS, in the sense that they leave unbroken half of the supersymmetries of the model.
Non-singular string cosmology in a 2d Hybrid model
Florakis, Ioannis; Partouche, Herve; Toumbas, Nicolaos
2010-01-01
The existence of non-singular string cosmologies is established in a class of two-dimensional supersymmetric Hybrid models at finite temperature. The left-moving sector of the Hybrid models gives rise to 16 real (N_4=4) spacetime supercharges as in the usual superstring models. The right-moving sector is non-supersymmetric at the massless level, but is characterized by MSDS symmetry, which ensures boson/fermion degeneracy of the right-moving massive levels. Finite temperature configurations, which are free of Hagedorn instabilities, are constructed in the presence of non-trivial "gravito-magnetic" fluxes. These fluxes inject non-trivial winding charge into the thermal vacuum and restore the thermal T-duality symmetry associated with the Euclidean time circle. Thanks to the unbroken right-moving MSDS symmetry, the one-loop string partition function is exactly calculable beyond any alpha'-approximation. At the self-dual point new massless thermal states appear, sourcing localized spacelike branes, which can be ...
Mirage Models Confront the LHC: I. Kahler-Stabilized Heterotic String Theory
Kaufman, Bryan L; Gaillard, Mary K
2013-01-01
We begin the study of a class of string-motivated effective supergravity theories in light of current data from the CERN Large Hadron Collider (LHC). The case of heterotic string theory, in which the dilaton is stabilized via non-perturbative corrections to the Kahler metric, will be considered first. This model is highly constrained and therefore predictive. We find that much of the reasonable parameter space afforded to the model -- representing the strong dynamics of a presumed gaugino condensation in the hidden sector -- is now observationally disfavored by the LHC results. Most of the theoretically-motivated parameter space that remains can be probed with data that has already been collected, and most of the remainder will be definitively explored within the first year of operation at center of mass energy of 13 TeV. Expected signatures for a number of benchmark points are discussed. We find that the surviving space of the model makes a precise prediction as to the relation of many superpartner masses, a...
Heat propagation models for superconducting nanobridges at millikelvin temperatures
Blois, A.; Rozhko, S.; Hao, L.; Gallop, J. C.; Romans, E. J.
2017-01-01
Nanoscale superconducting quantum interference devices (nanoSQUIDs) most commonly use Dayem bridges as Josephson elements to reduce the loop size and achieve high spin sensitivity. Except at temperatures close to the critical temperature T c, the electrical characteristics of these bridges exhibit undesirable thermal hysteresis which complicates device operation. This makes proper thermal analysis an essential design consideration for optimising nanoSQUID performance at ultralow temperatures. However the existing theoretical models for this hysteresis were developed for micron-scale devices operating close to liquid helium temperatures, and are not fully applicable to a new generation of much smaller devices operating at significantly lower temperatures. We have therefore developed a new analytic heat model which enables a more accurate prediction of the thermal behaviour in such circumstances. We demonstrate that this model is in good agreement with experimental results measured down to 100 mK and discuss its validity for different nanoSQUID geometries.
Intuitionistic Fuzzy Automaton for Approximate String Matching
Directory of Open Access Journals (Sweden)
K.M. Ravi
2014-03-01
Full Text Available This paper introduces an intuitionistic fuzzy automaton model for computing the similarity between pairs of strings. The model details the possible edit operations needed to transform any input (observed string into a target (pattern string by providing a membership and non-membership value between them. In the end, an algorithm is given for approximate string matching and the proposed model computes the similarity and dissimilarity between the pair of strings leading to better approximation.
The role of local repulsion in superconductivity in the Hubbard-Holstein model
Lin, Chungwei; Wang, Bingnan; Teo, Koon Hoo
2017-01-01
We examine the superconducting solution in the Hubbard-Holstein model using Dynamical Mean Field Theory. The Holstein term introduces the site-independent Boson fields coupling to local electron density, and has two competing influences on superconductivity: The Boson field mediates the effective electron-electron attraction, which is essential for the S-wave electron pairing; the same coupling to the Boson fields also induces the polaron effect, which makes the system less metallic and thus suppresses superconductivity. The Hubbard term introduces an energy penalty U when two electrons occupy the same site, which is expected to suppress superconductivity. By solving the Hubbard-Holstein model using Dynamical Mean Field theory, we find that the Hubbard U can be beneficial to superconductivity under some circumstances. In particular, we demonstrate that when the Boson energy Ω is small, a weak local repulsion actually stabilizesthe S-wave superconducting state. This behavior can be understood as an interplay between superconductivity, the polaron effect, and the on-site repulsion: As the polaron effect is strong and suppresses superconductivity in the small Ω regime, the weak on-site repulsion reduces the polaron effect and effectively enhances superconductivity. Our calculation elucidates the role of local repulsion in the conventional S-wave superconductors.
Doubled strings, negative strings and null waves
Energy Technology Data Exchange (ETDEWEB)
Blair, Chris D.A. [Theoretische Natuurkunde, Vrije Universiteit Brussel, and the International Solvay Institutes,Pleinlaan 2, B-1050 Brussels (Belgium)
2016-11-08
We revisit the fundamental string (F1) solution in the doubled formalism. We show that the wave-like solution of double field theory (DFT) corresponding to the F1/pp-wave duality pair is more properly a solution of the DFT action coupled to a doubled sigma model action. The doubled string configuration which sources the pp-wave can be thought of as static gauge with the string oriented in a dual direction. We also discuss the DFT solution corresponding to a vibrating string, carrying both winding and momentum. We further show that the solution dual to the F1 in both time and space can be viewed as a “negative string” solution. Negative branes are closely connected to certain exotic string theories which involve unusual signatures for both spacetime and brane worldvolumes. In order to better understand this from the doubled point of view, we construct a variant of DFT suitable for describing theories in which the fundamental string has a Euclidean worldsheet, for which T-dualities appear to change the spacetime signature.
Energy Technology Data Exchange (ETDEWEB)
Maurya, D. Ch., E-mail: dcmaurya563@gmail.com; Zia, R., E-mail: rashidzya@gmail.com; Pradhan, A., E-mail: pradhan.anirudh@gmail.com [GLA University, Department of Mathematics, Institute of Applied Sciences and Humanities (India)
2016-10-15
We discuss a spatially homogeneous and anisotropic string cosmological models in the Brans–Dicke theory of gravitation. For a spatially homogeneous metric, it is assumed that the expansion scalar θ is proportional to the shear scalar σ. This condition leads to A = kB{sup m}, where k and m are constants. With these assumptions and also assuming a variable scale factor a = a(t), we find solutions of the Brans–Dicke field equations. Various phenomena like the Big Bang, expanding universe, and shift from anisotropy to isotropy are observed in the model. It can also be seen that in early stage of the evolution of the universe, strings dominate over particles, whereas the universe is dominated by massive strings at the late time. Some physical and geometrical behaviors of the models are also discussed and observed to be in good agreement with the recent observations of SNe la supernovae.
Bukenov, A K; Polikarpov, M I; Polley, L; Wiese, U J
1992-01-01
We develop a formalism for the quantization of topologically stable excitations in the 4-dimensional abelian lattice gauge theory. The excitations are global and local (Abrikosov-Nielsen-Olesen) strings and monopoles. The operators of creation and annihilation of string states are constructed; the string Green functions are represented as a path integral over random surfaces. Topological excitations play an important role in the early universe. In the broken symmetry phase of the $U(1)$ spin model, closed global cosmic strings arise, while in the Higgs phase of the noncompact gauge-Higgs model, local cosmic strings are present. The compact gauge-Higgs model also involves monopoles. Then the strings can break if their ends are capped by monopoles. The topology of the Euclidean string world sheets are studied by numerical simulations.
Physically Inspired Models for the Synthesis of Stiff Strings with Dispersive Waveguides
Directory of Open Access Journals (Sweden)
Testa I
2004-01-01
Full Text Available We review the derivation and design of digital waveguides from physical models of stiff systems, useful for the synthesis of sounds from strings, rods, and similar objects. A transform method approach is proposed to solve the classic fourth-order equations of stiff systems in order to reduce it to two second-order equations. By introducing scattering boundary matrices, the eigenfrequencies are determined and their dependency is discussed for the clamped, hinged, and intermediate cases. On the basis of the frequency-domain physical model, the numerical discretization is carried out, showing how the insertion of an all-pass delay line generalizes the Karplus-Strong algorithm for the synthesis of ideally flexible vibrating strings. Knowing the physical parameters, the synthesis can proceed using the generalized structure. Another point of view is offered by Laguerre expansions and frequency warping, which are introduced in order to show that a stiff system can be treated as a nonstiff one, provided that the solutions are warped. A method to compute the all-pass chain coefficients and the optimum warping curves from sound samples is discussed. Once the optimum warping characteristic is found, the length of the dispersive delay line to be employed in the simulation is simply determined from the requirement of matching the desired fundamental frequency. The regularization of the dispersion curves by means of optimum unwarping is experimentally evaluated.
One-loop and D-instanton corrections to the effective action of open string models
Energy Technology Data Exchange (ETDEWEB)
Schmidt-Sommerfeld, Maximilian
2009-07-02
Methods for the calculation of certain corrections to effective actions, which comprehend the low-energy physics of string compactifications with open strings, are explained. First the shape of such actions is describes and some examples for compactifications are presented, especially a type I string model to which a dual model on the base of the heterotic string is known. Then corrections on the gauge coupling constant and on the gauge-kinetic function are discussed. general procedures for their calculation are sketched and applied to some models. The explicitly determinded corrections depend non-holomorphically on the moduli of the compactification manifold. It is explained that this is not in disagreement on the holomorphy of the gauge-kinetic function and how the latter can be extracted from the calculated results. Next D-instantons and their influence on the low-energy action are detailedly analyzed, whereby the zero modes of the instantons and global Abelian symmetries play a central role. A formula for the caclulation of scattering matrix elements in instanton sectors is given. It is to be expected that the considered instantons contribute to the superpotential of the low-energy action. However from the formula it becomes not immediately clear, how far this is possible. The mentioned formula seems to lead to expressions, which are in disagreement to the holomorphy of the superpotential. It is shown that non-holomorphic terms partly simplify, partly are so composed that the result is in accordance with the holomorphy of the superpotential. The D-instanton calculus is then used in order to derive the ADS superpotential, which is known from field theory. That this is possible is to be considered as successful test of the instanton calculus. D-instanton corrections to the gauge-kinetic functions are considered. S duality between the type I and the heterotic string is used in order to determine how the structure of the zero modes of the relevant instantons looks
de Sitter vacua in no-scale supergravities and Calabi-Yau string models
Energy Technology Data Exchange (ETDEWEB)
Covi, L. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Warsaw Univ. (Poland). Inst. of Theoretical Physics; Gomez-Reino, M. [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Gross, C. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Louis, J. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik]|[Hamburg Univ. (Germany). Zentrum fuer Mathematische Physik; Palma, G.A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Scrucca, C.A. [Ecole Polytechnique Federale de Lausanne (Switzerland). Inst. de Th. des Phen. Phys.
2008-04-15
We perform a general analysis on the possibility of obtaining metastable vacua with spontaneously broken N = 1 supersymmetry and non-negative cosmological constant in the moduli sector of string models. More specifically, we study the condition under which the scalar partners of the Goldstino are non-tachyonic, which depends only on the Kaehler potential. This condition is not only necessary but also sufficient, in the sense that all of the other scalar fields can be given arbitrarily large positive square masses if the superpotential is suitably tuned. We consider both heterotic and orientifold string compactifications in the large-volume limit and show that the no-scale property shared by these models severely restricts the allowed values for the 'sGoldstino' masses in the superpotential parameter space. We find that a positive mass term may be achieved only for certain types of compactifications and specific Goldstino directions. Additionally, we show how subleading corrections to the Kaehler potential which break the no-scale property may allow to lift these masses. (orig.)
Explicit de Sitter flux vacua for global string models with chiral matter
Energy Technology Data Exchange (ETDEWEB)
Cicoli, Michele [Dipartimento di Fisica e Astronomia, Università di Bologna, via Irnerio 46, 40126 Bologna (Italy); INFN, Sezione di Bologna, via Irnerio 46, 40126 Bologna (Italy); ICTP, Strada Costiera 11, 34014 Trieste (Italy); Klevers, Denis [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104-6396 (United States); Krippendorf, Sven [Bethe Center for Theoretical Physics and Physikalisches Institut der Universität Bonn, Nussallee 12, 53115 Bonn (Germany); Mayrhofer, Christoph [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 19, 69120 Heidelberg (Germany); Quevedo, Fernando [ICTP, Strada Costiera 11, 34014 Trieste (Italy); DAMTP, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom); Valandro, Roberto [ICTP, Strada Costiera 11, 34014 Trieste (Italy); INFN, Sezione di Trieste, Trieste (Italy)
2014-05-05
We address the open question of performing an explicit stabilisation of all closed string moduli (including dilaton, complex structure and Kähler moduli) in fluxed type IIB Calabi-Yau compactifications with chiral matter. Using toric geometry we construct Calabi-Yau manifolds with del Pezzo singularities. D-branes located at such singularities can support the Standard Model gauge group and matter content or some close extensions. In order to control complex structure moduli stabilisation we consider Calabi-Yau manifolds which exhibit a discrete symmetry that reduces the effective number of complex structure moduli. We calculate the corresponding periods in the symplectic basis of invariant three-cycles and find explicit flux vacua for concrete examples. We compute the values of the flux superpotential and the string coupling at these vacua. Starting from these explicit complex structure solutions, we obtain AdS and dS minima where the Kähler moduli are stabilised by a mixture of D-terms, non-perturbative and perturbative α{sup ′} corrections as in the LARGE Volume Scenario. In the considered example the visible sector lives at a dP{sub 6} singularity which can be higgsed to the phenomenologically interesting class of models at the dP{sub 3} singularity.
Explicit de Sitter flux vacua for global string models with chiral matter
Cicoli, Michele; Klevers, Denis; Krippendorf, Sven; Mayrhofer, Christoph; Quevedo, Fernando; Valandro, Roberto
2014-05-01
We address the open question of performing an explicit stabilisation of all closed string moduli (including dilaton, complex structure and Kähler moduli) in fluxed type IIB Calabi-Yau compactifications with chiral matter. Using toric geometry we construct Calabi-Yau manifolds with del Pezzo singularities. D-branes located at such singularities can support the Standard Model gauge group and matter content or some close extensions. In order to control complex structure moduli stabilisation we consider Calabi-Yau manifolds which exhibit a discrete symmetry that reduces the effective number of complex structure moduli. We calculate the corresponding periods in the symplectic basis of invariant three-cycles and find explicit flux vacua for concrete examples. We compute the values of the flux superpotential and the string coupling at these vacua. Starting from these explicit complex structure solutions, we obtain AdS and dS minima where the Kähler moduli are stabilised by a mixture of D-terms, non-perturbative and perturbative α ' corrections as in the LARGE Volume Scenario. In the considered example the visible sector lives at a dP6 singularity which can be higgsed to the phenomenologically interesting class of models at the dP3 singularity.
Extra $Z^\\prime$s and $W^\\prime$s in Heterotic--String Derived Models
Faraggi, Alon E
2015-01-01
The ATLAS collaboration recently recorded possible excess in the di--boson production at the di--boson invariant mass at around 2 TeV. Such an excess may be produced if there exist additional $Z^\\prime$ and/or $W^\\prime$ at that scale. We survey the extra $Z^\\prime$s and $W^\\prime$s that may arise from semi--realistic heterotic string vacua in the free fermionic formulation in seven distinct cases including: $U(1)_{Z^\\prime}\\in SO(10)$; family universal $U(1)_{Z^\\prime}$ not in $SO(10)$; non--universal $U(1)_{Z^\\prime}$; hidden sector $U(1)$ symmetries and kinetic mixing; left--right symmetric models; Pati--Salam models; leptophobic and custodial symmetries. Each case has a distinct signature associated with the extra symmetry breaking scale. In one of the cases we explore the discovery potential at the LHC using resonant leptoproduction. Existence of extra vector boson with the reported properties will significantly constrain the space of allowed string vacua.
Searching for features of a string-inspired inflationary model with cosmological observations
Cai, Yi-Fu; Ferreira, Elisa G. M.; Hu, Bin; Quintin, Jerome
2015-12-01
The latest Planck results show a power deficit in the temperature anisotropies near ℓ≈20 in the cosmic microwave background (CMB). This observation can hardly be explained within the standard inflationary Λ -cold-dark-matter (Λ CDM ) scenario. In this paper we consider a string theory inspired inflationary model (axion monodromy inflation) with a step-like modulation in the potential which gives rise to observable signatures in the primordial perturbations. One interesting phenomenon is that the primordial scalar modes experience a sudden suppression at a critical scale when the modulation occurs. By fitting to the CMB data, we find that the model can nicely explain the ℓ≈20 power deficit anomaly as well as predict specific patterns in the temperature-polarization correlation and polarization autocorrelation spectra. Though the significance of the result is not sufficient to claim a detection, our analysis reveals that fundamental physics at extremely high energy scales, namely, some effects inspired by string theory, may be observationally testable in forthcoming cosmological experiments.
Dynamical Electroweak Symmetry Breaking in String Models with D-branes
Kitazawa, Noriaki
2009-01-01
The possibility of dynamical electroweak symmetry breaking by strong coupling gauge interaction in models with D-branes in String Theory is examined. Instead of elementary scalar Higgs doublet fields, the gauge symmetry with strong coupling (technicolor) is introduced. As the first step of this direction, a toy model, which is not fully realistic, is concretely analyzed in some detail. The model consists of D-branes and anti-D-branes at orbifold singularities in (T^2 x T^2 x T^2)/Z_3 which preserves supersymmetry. Supersymmetry is broken through the brane supersymmetry breaking. It is pointed out that the problem of large S parameter in dynamical electroweak symmetry breaking scenario may be solved by natural existence of kinetic term mixings between hypercharge U(1) gauge boson and massive anomalous U(1) gauge bosons. The problems to be solved toward constructing more realistic models are clarified in the analysis.
Positivity of Lyapunov exponents for Anderson-type models on two coupled strings
Directory of Open Access Journals (Sweden)
Hakim Boumaza
2007-03-01
Full Text Available We study two models of Anderson-type random operators on two deterministically coupled continuous strings. Each model is associated with independent, identically distributed four-by-four symplectic transfer matrices, which describe the asymptotics of solutions. In each case we use a criterion by Gol'dsheid and Margulis (i.e. Zariski denseness of the group generated by the transfer matrices in the group of symplectic matrices to prove positivity of both leading Lyapunov exponents for most energies. In each case this implies almost sure absence of absolutely continuous spectrum (at all energies in the first model and for sufficiently large energies in the second model. The methods used allow for singularly distributed random parameters, including Bernoulli distributions.
Vachaspati, Tanmay; Steer, Daniele
2015-01-01
This article, written for Scolarpedia, provides a brief introduction into the subject of cosmic strings, together with a review of their main properties, cosmological evolution and observational signatures.
A review of the microscopic modeling of the 5-dim. black hole of IIB string theory
Indian Academy of Sciences (India)
Spenta R Wadia
2001-01-01
We review the theory of the microscopic modeling of the 5-dim. black hole of type IIB string theory in terms of the 1-5 brane system. A detailed discussion of the low energy effective Lagrangian of the brane system is presented and the black hole micro-states are identiﬁed. These considerations are valid in the strong coupling regime of supergravity due to the non-renormalization of the low energy dynamics in this model. Using Maldacena duality and standard statistical mechanics methods one can account for black hole thermodynamics and calculate the absorption cross section and the Hawking radiation rates. Hence, at least in the case of this model black hole, since we can account for black hole properties within a unitary theory, there is no information paradox.
Bianchi type string cosmological models in f(R,T) gravity
Sahoo, P. K.; Mishra, B.; Sahoo, Parbati; Pacif, S. K. J.
2016-09-01
In this work we have studied Bianchi-III and - VI 0 cosmological models with string fluid source in f( R, T) gravity (T. Harko et al., Phys. Rev. D 84, 024020 (2011)), where R is the Ricci scalar and T the trace of the stress energy-momentum tensor in the context of late time accelerating expansion of the universe as suggested by the present observations. The exact solutions of the field equations are obtained by using a time-varying deceleration parameter. The universe is anisotropic and free from initial singularity. Our model initially shows acceleration for a certain period of time and then decelerates consequently. Several dynamical and physical behaviors of the model are also discussed in detail.
Superconducting, magnetic, and charge correlations in the doped two-chain Hubbard model
Asai, Y
1995-01-01
Superconducting, magnetic, and charge correlation functions and dynamic spin correlation functions of the doped two-chain Hubbard model is studied with the projector Quantum Monte carlo method and Lanczos recursion method. Of the three correlation functions, the interchain singlet superconducting correlation function is the most long range. Our data is not consistent with the Luther-Emery picture.
Modeling nonlinear problems in the mechanics of strings and rods the role of the balance laws
O'Reilly, Oliver M
2017-01-01
This book presents theories of deformable elastic strings and rods and their application to broad classes of problems. Readers will gain insights into the formulation and analysis of models for mechanical and biological systems. Emphasis is placed on how the balance laws interplay with constitutive relations to form a set of governing equations. For certain classes of problems, it is shown how a balance of material momentum can play a key role in forming the equations of motion. The first half of the book is devoted to the purely mechanical theory of a string and its applications. The second half of the book is devoted to rod theories, including Euler’s theory of the elastica, Kirchhoff ’s theory of an elastic rod, and a range of Cosserat rod theories. A variety of classic and recent applications of these rod theories are examined. Two supplemental chapters, the first on continuum mechanics of three-dimensional continua and the second on methods from variational calculus, are included to provide relevant ...
Dynamical String Tension in String Theory with Spacetime Weyl Invariance
Bars, Itzhak; Turok, Neil
2014-01-01
The fundamental string length, which is an essential part of string theory, explicitly breaks scale invariance. However, in field theory we demonstrated recently that the gravitational constant, which is directly related to the string length, can be promoted to a dynamical field if the standard model coupled to gravity (SM+GR) is lifted to a locally scale (Weyl) invariant theory. The higher gauge symmetry reveals previously unknown field patches whose inclusion turn the classically conformally invariant SM+GR into a geodesically complete theory with new cosmological and possibly further physical consequences. In this paper this concept is extended to string theory by showing how it can be Weyl lifted with a local scale symmetry acting on target space background fields. In this process the string tension (fundamental string length) is promoted to a dynamical field, in agreement with the parallel developments in field theory. We then propose a string theory in a geodesically complete cosmological stringy backgr...
Dipole model test with one superconducting coil; results analysed
Durante, M; Ferracin, P; Fessia, P; Gauthier, R; Giloux, C; Guinchard, M; Kircher, F; Manil, P; Milanese, A; Millot, J-F; Muñoz Garcia, J-E; Oberli, L; Perez, J-C; Pietrowicz, S; Rifflet, J-M; de Rijk, G; Rondeaux, F; Todesco, E; Viret, P; Ziemianski, D
2013-01-01
This report is the deliverable report 7.3.1 “Dipole model test with one superconducting coil; results analysed “. The report has four parts: “Design report for the dipole magnet”, “Dipole magnet structure tested in LN2”, “Nb3Sn strand procured for one dipole magnet” and “One test double pancake copper coil made”. The 4 report parts show that, although the magnet construction will be only completed by end 2014, all elements are present for a successful completion. Due to the importance of the project for the future of the participants and given the significant investments done by the participants, there is a full commitment to finish the project.
Dipole model test with one superconducting coil: results analysed
Bajas, H; Benda, V; Berriaud, C; Bajko, M; Bottura, L; Caspi, S; Charrondiere, M; Clément, S; Datskov, V; Devaux, M; Durante, M; Fazilleau, P; Ferracin, P; Fessia, P; Gauthier, R; Giloux, C; Guinchard, M; Kircher, F; Manil, P; Milanese, A; Millot, J-F; Muñoz Garcia, J-E; Oberli, L; Perez, J-C; Pietrowicz, S; Rifflet, J-M; de Rijk, G; Rondeaux, F; Todesco, E; Viret, P; Ziemianski, D
2013-01-01
This report is the deliverable report 7.3.1 “Dipole model test with one superconducting coil; results analysed “. The report has four parts: “Design report for the dipole magnet”, “Dipole magnet structure tested in LN2”, “Nb3Sn strand procured for one dipole magnet” and “One test double pancake copper coil made”. The 4 report parts show that, although the magnet construction will be only completed by end 2014, all elements are present for a successful completion. Due to the importance of the project for the future of the participants and given the significant investments done by the participants, there is a full commitment to finish the project.
Frampton, Paul H
2015-01-01
In this note, I recollect a two-week period in September 1968 when I factorized the Veneziano model using string variables in Chicago. Professor Yoichiro Nambu went on to calculate the N-particle dual resonance model and then to factorize it on an exponential degeneracy of states. That was in 1968 and the following year 1969 he discovered the string action. I also include some other reminiscences of Nambu who passed away on July 5, 2105.
Lake, Matthew J
2015-01-01
We outline a model of abelian-Higgs strings with variable scalar and vector core radii. In general, the functions determining the time and position-dependent core widths may be expressed as arbitrary left or right movers, of which the usual constant values are a particular solution. In this case the string may carry momentum, even if the embedding of its central axis remains fixed, and the resulting objects resemble "necklaces". Some possible astrophysical applications of lumpy strings, including as potential engines for anomalous gamma ray bursts, are also discussed.
Gold bead-strings in silica nanowires: a simple diffusion model
Energy Technology Data Exchange (ETDEWEB)
Fletcher, N H; Elliman, R G; Kim, T-H [Research School of Physics and Engineering, Australian National University, Canberra 0200 (Australia)], E-mail: neville.fletcher@anu.edu.au
2009-02-25
Silica nanowires grown from gold droplets deposited on the surface of a silicon crystal sometimes develop within them a regular series of gold beads distributed along the wire axis in what is often called either a bead-string or a pea-pod structure. This is generally attributed to a 'Rayleigh instability' driven by the surface free energy of the included gold core. Here a new model is proposed in which quasi-conical gold inclusions are developed by the diffusion-limited growth process and are subsequently modified to spherical shape by another diffusion process that is driven by surface free energy. This model provides a possible basis for detailed numerical calculations.
Searching for Features of a String Inspired Inflationary Model with Cosmological Observations
Cai, Yi-Fu; Hu, Bin; Quintin, Jerome
2015-01-01
The latest Planck results show a power deficit in the temperature anisotropies near $\\ell \\approx 20$ in the cosmic microwave background (CMB). This observation can hardly be explained within the standard inflationary $\\Lambda$-cold-dark-matter ($\\Lambda$CDM) scenario. In this Letter we consider a string theory inspired inflationary model (axion monodromy inflation) with a step-like modulation in the potential which gives rise to observable signatures in the primordial perturbations. One interesting phenomenon is that the primordial scalar modes experience a sudden suppression at a critical scale when the modulation occurs. By fitting to the CMB data, we find that the model can nicely explain the $\\ell \\approx 20$ power deficit anomaly as well as predict specific patterns in the temperature-polarization correlation and polarization autocorrelation spectra. Though the significance of the result is not sufficient to claim a detection, our analysis reveals that fundamental physics at extremely high energy scales...
Fermions on the electroweak string
Moreno, J M; Quirós, Mariano; Moreno, J M; Oaknin, D H; Quiros, M
1995-01-01
We construct a simple class of exact solutions of the electroweak theory including the naked Z--string and fermion fields. It consists in the Z--string configuration (\\phi,Z_\\theta), the {\\it time} and z components of the neutral gauge bosons (Z_{0,3},A_{0,3}) and a fermion condensate (lepton or quark) zero mode. The Z--string is not altered (no feed back from the rest of fields on the Z--string) while fermion condensates are zero modes of the Dirac equation in the presence of the Z--string background (no feed back from the {\\it time} and z components of the neutral gauge bosons on the fermion fields). For the case of the n--vortex Z--string the number of zero modes found for charged leptons and quarks is (according to previous results by Jackiw and Rossi) equal to |n|, while for (massless) neutrinos is |n|-1. The presence of fermion fields in its core make the obtained configuration a superconducting string, but their presence (as well as that of Z_{0,3},A_{0,3}) does not enhance the stability of the Z--stri...
Universality and string theory
Bachlechner, Thomas Christian
The first run at the Large Hadron Collider has deeply challenged conventional notions of naturalness, and CMB polarization experiments are about to open a new window to early universe cosmology. As a compelling candidate for the ultraviolet completion of the standard model, string theory provides a prime opportunity to study both early universe cosmology and particle physics. However, relating low energy observations to ultraviolet physics requires knowledge of the metastable states of string theory through the study of vacua. While it is difficult to directly obtain infrared data from explicit string theory constructions, string theory imposes constraints on low energy physics. The study of ensembles of low energy theories consistent with ultra-violet constraints provides insight on generic features we might expect to occur in string compactifications. In this thesis we present a statistical treatment of vacuum stability and vacuum properties in the context of random supergravity theories motivated by string theory. Early universe cosmology provides another avenue to high energy physics. From the low energy perspective large field inflation is typically considered highly unnatural: the scale relevant for the diameter of flat regions in moduli space is sub-Planckian in regions of perturbative control. To approach this problem, we consider generic Calabi-Yau compactifications of string theory and find that super-Planckian diameters of axion fundamental domains in fact arise generically. We further demonstrate that such super-Planckian flat regions are plausibly consistent with theWeak Gravity Conjecture.
Clark, S. K.; Dodge, R. N.; Nybakken, G. H.
1972-01-01
The string theory was evaluated for predicting lateral tire dynamic properties as obtained from scaled model tests. The experimental data and string theory predictions are in generally good agreement using lateral stiffness and relaxation length values obtained from the static or slowly rolling tire. The results indicate that lateral forces and self-aligning torques are linearly proportional to tire lateral stiffness and to the amplitude of either steer or lateral displacement. In addition, the results show that the ratio of input excitation frequency to road speed is the proper independent variable by which frequency should be measured.
The CP(N-1) model on a Disc and Decay of a Non-Abelian String
Gorsky, A
2013-01-01
We consider the role of quantum effects in the non-perturbative decay of non-abelian string with orientational moduli in non-supersymmetric D=4 gauge theory. To this aim the effective action in the $CP(N-1)$ model on a disc at large N has been calculated. It exhibits phase transition at some radius, the "wrong sign" Luscher term and large boundary boojum-like negative contribution. The effect of $\\theta$ - term and the possibility of the spontaneous creation of the non-abelian string are briefly discussed.
Energy Technology Data Exchange (ETDEWEB)
Dijkgraaf, R. [Amsterdam Univ. (Netherlands). Dept. of Mathematics; Verlinde, E. [TH-Division, CERN, CH-1211 Geneva 23 (Switzerland)]|[Institute for Theoretical Physics, Universtity of Utrecht, 3508 TA Utrecht (Netherlands); Verlinde, H. [Institute for Theoretical Physics, University of Amsterdam, 1018 XE Amsterdam (Netherlands)
1997-09-01
Via compactification on a circle, the matrix model of M-theory proposed by Banks et al. suggests a concrete identification between the large N limit of two-dimensional N=8 supersymmetric Yang-Mills theory and type IIA string theory. In this paper we collect evidence that supports this identification. We explicitly identify the perturbative string states and their interactions, and describe the appearance of D-particle and D-membrane states. (orig.).
Dijkgraaf, R; Verlinde, Herman L
1997-01-01
Via compactification on a circle, the matrix model of M-theory proposed by Banks et al suggests a concrete identification between the large N limit of two-dimensional N=8 supersymmetric Yang-Mills theory and type IIA string theory. In this paper we collect evidence that supports this identification. We explicitly identify the perturbative string states and their interactions, and describe the appearance of D-particle and D-membrane states.
Itoyama, H
2016-01-01
This is a brief summary of an introductory lecture for students and scholars in general given by the author at Nambu Memorial Symposium which was held at Osaka City University on September 29, 2015. We review the invention of string theory by Professor Yoichiro Nambu following the discovery of the Veneziano amplitude. We also discuss Professor Nambu's proposal on string theory in the Schild gauge in 1976 which is related to the matrix model of Yang-Mills type.
Directory of Open Access Journals (Sweden)
Wenjun Huang
2017-01-01
Full Text Available Mechanical extending limit in horizontal drilling means the maximum horizontal extending length of a horizontal well under certain ground and down-hole mechanical constraint conditions. Around this concept, the constrained optimization model of mechanical extending limits is built and simplified analytical results for pick-up and slack-off operations are deduced. The horizontal extending limits for kinds of tubular strings under different drilling parameters are calculated and drawn. To improve extending limits, an optimal design model of drill strings is built and applied to a case study. The results indicate that horizontal extending limits are underestimated a lot when the effects of friction force on critical helical buckling loads are neglected. Horizontal extending limits firstly increase and tend to stable values with vertical depths. Horizontal extending limits increase faster but finally become smaller with the increase of horizontal pushing forces for tubular strings of smaller modulus-weight ratio. Sliding slack-off is the main limit operation and high axial friction is the main constraint factor constraining horizontal extending limits. A sophisticated installation of multiple tubular strings can greatly inhibit helical buckling and increase horizontal extending limits. The optimal design model is called only once to obtain design results, which greatly increases the calculation efficiency.
Numerical solution of High-kappa model of superconductivity
Energy Technology Data Exchange (ETDEWEB)
Karamikhova, R. [Univ. of Texas, Arlington, TX (United States)
1996-12-31
We present formulation and finite element approximations of High-kappa model of superconductivity which is valid in the high {kappa}, high magnetic field setting and accounts for applied magnetic field and current. Major part of this work deals with steady-state and dynamic computational experiments which illustrate our theoretical results numerically. In our experiments we use Galerkin discretization in space along with Backward-Euler and Crank-Nicolson schemes in time. We show that for moderate values of {kappa}, steady states of the model system, computed using the High-kappa model, are virtually identical with results computed using the full Ginzburg-Landau (G-L) equations. We illustrate numerically optimal rates of convergence in space and time for the L{sup 2} and H{sup 1} norms of the error in the High-kappa solution. Finally, our numerical approximations demonstrate some well-known experimentally observed properties of high-temperature superconductors, such as appearance of vortices, effects of increasing the applied magnetic field and the sample size, and the effect of applied constant current.
Blanco-Pillado, Jose J; Shlaer, Benjamin
2015-01-01
We analyze the shapes of cosmic string loops found in large-scale simulations of an expanding-universe string network. The simulation does not include gravitational back reaction, but we model that process by smoothing the loop using Lorentzian convolution. We find that loops at formation consist of generally straight segments separated by kinks. We do not see cusps or any cusp-like structure at the scale of the entire loop, although we do see very small regions of string that move with large Lorentz boosts. However, smoothing of the string almost always introduces two cusps on each loop. The smoothing process does not lead to any significant fragmentation of loops that were in non-self-intersecting trajectories before smoothing.
String theory compactifications
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.
Energy Technology Data Exchange (ETDEWEB)
Boschi, C Degli Esposti [CNR, Unita CNISM di Bologna, viale Berti-Pichat, 6/2, I-40127, Bologna (Italy); Di Dio, M; Morandi, G [Dipartimento di Fisica dell' Universita di Bologna, viale Berti-Pichat, 6/2, I-40127, Bologna (Italy); Roncaglia, M [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748, Garching (Germany)
2009-02-06
We derive the dominant contribution to the large-distance decay laws of correlation functions towards their asymptotic limits for a spin chain model that exhibits both Haldane and Neel phases in its ground-state phase diagram. The analytic results are obtained by means of an approximate mapping between a spin-1 anisotropic Hamiltonian onto a fermionic model of noninteracting Bogoliubov quasiparticles related in turn (via Jordan-Wigner transformation) to the XY spin-1/2 chain in a transverse field. This approach allows us to express the spin-1 string operators in terms of fermionic operators so that the dominant contribution to the string correlators at large distances can be computed using the technique of Toeplitz determinants. As expected, we find long-range string order both in the longitudinal and in the transverse channel in the Haldane phase, while in the Neel phase only the longitudinal order survives. In this way, the long-range string order can be explicitly related to the components of the magnetization of the XY model. Moreover, apart from the critical line, where the decay is algebraic, we find that in the gapped phases the decay is governed by an exponential tail multiplied by power-law factors. As regards the usual two points correlation functions, we show that the longitudinal one behaves in a 'dual' fashion with respect to the transverse string correlator, namely both the asymptotic values and the decay laws exchange when the transition line is crossed. For the transverse spin-spin correlator, we always find a finite characteristic length which is an unexpected feature at the critical point. The results of this analysis prove some conjectures put forward in the past. We also comment briefly on the entanglement features of the original system versus those of the effective model. The goodness of the approximation and the analytical predictions are checked versus density-matrix renormalization group calculations.
Superconductivity from doublon condensation in the ionic Hubbard model
Samanta, Abhisek; Sensarma, Rajdeep
2016-12-01
In the ionic Hubbard model, the on-site repulsion U , which drives a Mott insulator, and the ionic potential V , which drives a band insulator, compete with each other to open up a window of charge fluctuations when U ˜V . We study this model on square and cubic lattices in the limit of large U and V , with V ˜U . Using an effective Hamiltonian and a slave-boson approach with both doublons and holons, we find that the system undergoes a phase transition as a function of V from an antiferromagnetic Mott insulator to a paramagnetic insulator with strong singlet correlations, which is driven by a condensate of "neutral" doublon-holon pairs. On further increasing V , the system undergoes another phase transition to a superconducting phase driven by condensate of "charged" doublons and holons. The superfluid phase, characterized by the presence of a coherent (but gapped) fermionic quasiparticle and h c /e flux quantization, has a high Tc˜t , which shows a dome-shaped behavior as a function of V . The paramagnetic insulator phase has a deconfined U(1) gauge field and associated gapless photon excitations. We also discuss how these phases can be detected in the ultracold-atom context.
Lumped element modelling of superconducting circuits with SPICE
Baveco, Maurice Antoine
2015-01-01
In this project research is carried out aimed at benchmarking a general-purpose circuit simulation software tool (”SPICE”). The project lasted for 8 weeks, from 29 June 2015 until 21 August 2015 at Performance Evaluation section at CERN. The goal was to apply it on a model of superconducting magnets, namely the main dipole circuit (RB circuit) of the the LHC (Large Hadron Collider), developed by members of the section. Then the strengths and the flaws of the tool were investigated. Transient effects were the main simulation focus point. In the first stage a simplified RB circuit was modelled in SPICE based on subcircuits. The first results were promising but still not with a perfect agreement. After implementing more detailed subcircuits there is an improvement and promising agreement achieved between SPICE and the results of the paper (PSpice) [2]. In general there are more strengths than drawbacks of simulating with SPICE. For example, it should have a shorter simulation time than PSpice for the same mo...
Functional renormalization for antiferromagnetism and superconductivity in the Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Friederich, Simon
2010-12-08
Despite its apparent simplicity, the two-dimensional Hubbard model for locally interacting fermions on a square lattice is widely considered as a promising approach for the understanding of Cooper pair formation in the quasi two-dimensional high-T{sub c} cuprate materials. In the present work this model is investigated by means of the functional renormalization group, based on an exact flow equation for the effective average action. In addition to the fermionic degrees of freedom of the Hubbard Hamiltonian, bosonic fields are introduced which correspond to the different possible collective orders of the system, for example magnetism and superconductivity. The interactions between bosons and fermions are determined by means of the method of ''rebosonization'' (or ''flowing bosonization''), which can be described as a continuous, scale-dependent Hubbard-Stratonovich transformation. This method allows an efficient parameterization of the momentum-dependent effective two-particle interaction between fermions (four-point vertex), and it makes it possible to follow the flow of the running couplings into the regimes exhibiting spontaneous symmetry breaking, where bosonic fluctuations determine the types of order which are present on large length scales. Numerical results for the phase diagram are presented, which include the mutual influence of different, competing types of order. (orig.)
A translation invariant bipolaron in the Holstein model and superconductivity.
Lakhno, Victor
2016-01-01
Large-radius translation invariant (TI) bipolarons are considered in a one-dimensional Holstein molecular chain. Criteria of their stability are obtained. The energy of a translation invariant bipolaron is shown to be lower than that of a bipolaron with broken symmetry. The results obtained are applied to the problem of superconductivity in 1D-systems. It is shown that TI-bipolaron mechanism of Bose-Einstein condensation can support superconductivity even for infinite chain.
Duodenal parasites test; Giardia - string test ... may be a sign parasite infection such as giardia . ... Elsevier; 2017:chap 58. Hill DR, Nash TE. Giardia lamblia. In: Bennett JE, Dolin R, Blaser MJ, ...
Matrix models, 4D black holes and topological strings on non-compact Calabi-Yau manifolds
Danielsson, Ulf H.; Olsson, Martin E.; Vonk, Marcel
2004-11-01
We study the relation between c = 1 matrix models at self-dual radii and topological strings on non-compact Calabi-Yau manifolds. Particularly the special case of the deformed matrix model is investigated in detail. Using recent results on the equivalence of the partition function of topological strings and that of four dimensional BPS black holes, we are able to calculate the entropy of the black holes, using matrix models. In particular, we show how to deal with the divergences that arise as a result of the non-compactness of the Calabi-Yau. The main result is that the entropy of the black hole at zero temperature coincides with the canonical free energy of the matrix model, up to a proportionality constant given by the self-dual temperature of the matrix model.
String Theory at LHC Using Top Quarks From String Balls
Nayak, Gouranga C
2009-01-01
According to string theory, string ball is a highly excited long string which decays to standard model particles at the Hagedorn temperature with thermal spectrum. If there are extra dimensions, the string scale can be ~TeV, and we should produce string balls at CERN LHC. In this paper we study top quark production from string balls at LHC and compare with the parton fusion results at NNLO using pQCD. We find significant top quark production from string balls at LHC which is comparable to standard model NNLO results. We also find that d\\sigma/dp_T of top quarks from string balls does not decrease significantly with increase in p_T, whereas it deceases sharply in case of standard model NNLO scenario. Hence, in the absence of black hole production at LHC, an enhancement in top quark cross section and its abnormal p_T distribution can be a signature of TeV scale string physics at LHC.
Spin polarization and color superconductivity in the Nambu-Jona-Lasinio model at finite temperature
Matsuoka, Hiroaki; da Providencia, Joao; Providencia, Constancia; Yamamura, Masatoshi
2016-01-01
We investigate the possible existence of spin polarization and color superconductivity in the Nambu-Jona-Lasinio model with a tensor-type interaction at finite density and temperature. The thermodynamic potential is calculated by the functional integral method. Numerical results indicate that at low temperature and quark chemical potential the chiral condensed phase exists, and at intermediate chemical potential the color superconducting phase appears. In addition, depending on the magnitude of the tensor coupling, at large chemical potential and low temperature, a color superconducting phase and a spin polarized phase may coexist while at intermediate temperatures only the spin polarized phase occurs.
Correlation-driven d -wave superconductivity in Anderson lattice model: Two gaps
Wysokiński, Marcin M.; Kaczmarczyk, Jan; Spałek, Józef
2016-07-01
Superconductivity in heavy-fermion systems has an unconventional nature and is considered to originate from the universal features of the electronic structure. Here, the Anderson lattice model is studied by means of the full variational Gutzwiller wave function incorporating nonlocal effects of the on-site interaction. We show that the d -wave superconducting ground state can be driven solely by interelectronic correlations. The proposed microscopic mechanism leads to a multigap superconductivity with the dominant contribution due to f electrons and in the dx2-y2-wave channel. Our results rationalize several important observations for CeCoIn5.
Constructing de Sitter vacua in no-scale string models without uplifting
Energy Technology Data Exchange (ETDEWEB)
Covi, Laura [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Gomez-Reino, Marta [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Gross, Christian [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Palma, Gonzalo A. [Leiden Univ. (Netherlands). Lorentz Inst. for Theoretical Physics; Scrucca, Claudio A. [Ecole Polytechnique Federale de Lausanne (Switzerland). Inst. de Theorie des Phenomenes Physiques
2008-12-15
We develop a method for constructing metastable de Sitter vacua in N=1 supergravity models describing the no-scale volume moduli sector of Calabi-Yau string compactifications. We consider both heterotic and orientifold models. Our main guideline is the necessary condition for the existence of metastable vacua coming from the Goldstino multiplet, which constrains the allowed scalar geometries and supersymmetry-breaking directions. In the simplest non-trivial case where the volume is controlled by two moduli, this condition simplifies and turns out to be fully characterised by the intersection numbers of the Calabi-Yau manifold. We analyse this case in detail and show that once the metastability condition is satisfied it is possible to reconstruct in a systematic way the local form of the superpotential that is needed to stabilise all the fields. We apply then this procedure to construct some examples of models where the superpotential takes a realistic form allowed by flux backgrounds and gaugino condensation effects, for which a viable vacuum arises without the need of invoking corrections to the Kaehler potential breaking the noscale property or uplifting terms. We finally discuss the prospects of constructing potentially realistic models along these lines. (orig.)
String Mediated Supersymmetry Breaking
Energy Technology Data Exchange (ETDEWEB)
Brodie, John H
2001-07-25
We consider the 3+1 visible sector to live on a Hanany-Witten D-brane construction in type IIA string theory. The messenger sector consists of stretched strings from the visible brane to a hidden D6-brane in the extra spatial dimensions. In the open string channel supersymmetry is broken by gauge mediation while in the closed string channel supersymmetry is broken by gravity mediation. Hence, we call this kind of mediation ''string mediation''. We propose an extension of the Dimopoulos-Georgi theorem to brane models: only detached probe branes can break supersymmetry without generating a tachyon. Fermion masses are generated at one loop if the branes break a sufficient amount of the ten dimensional Lorentz group while scalar potentials are generated if there is a force between the visible brane and the hidden brane. Scalars can be lifted at two loops through a combination of brane bending and brane forces. We find a large class of stable non-supersymmetric brane configurations of ten dimensional string theory.
Fabrication, Testing and Modeling of the MICE Superconducting Spectrometer Solenoids
Energy Technology Data Exchange (ETDEWEB)
Virostek, S.P.; Green, M.A.; Trillaud, F.; Zisman, M.S.
2010-05-16
The Muon Ionization Cooling Experiment (MICE), an international collaboration sited at Rutherford Appleton Laboratory in the UK, will demonstrate ionization cooling in a section of realistic cooling channel using a muon beam. A five-coil superconducting spectrometer solenoid magnet will provide a 4 tesla uniform field region at each end of the cooling channel. Scintillating fiber trackers within the 400 mm diameter magnet bore tubes measure the emittance of the beam as it enters and exits the cooling channel. Each of the identical 3-meter long magnets incorporates a three-coil spectrometer magnet section and a two-coil section to match the solenoid uniform field into the other magnets of the MICE cooling channel. The cold mass, radiation shield and leads are currently kept cold by means of three two-stage cryocoolers and one single-stage cryocooler. Liquid helium within the cold mass is maintained by means of a re-condensation technique. After incorporating several design changes to improve the magnet cooling and reliability, the fabrication and acceptance testing of the spectrometer solenoids have proceeded. The key features of the spectrometer solenoid magnets, the development of a thermal model, the results of the recently completed tests, and the current status of the project are presented.
Theoretical model of superconducting spintronic SIsFS devices
Bakurskiy, S. V.; Klenov, N. V.; Soloviev, I. I.; Bol'ginov, V. V.; Ryazanov, V. V.; Vernik, I. V.; Mukhanov, O. A.; Kupriyanov, M. Yu.; Golubov, A. A.
2013-05-01
Motivated by recent progress in the development of cryogenic memory compatible with single flux quantum (SFQ) circuits, we have performed a theoretical study of magnetic SIsFS Josephson junctions, where "S" is a bulk superconductor, "s" is a thin superconducting film, "F" is a metallic ferromagnet, and "I" is an insulator. We calculate the Josephson current as a function of s and F layers thickness, temperature, and exchange energy of F film. We outline several modes of operation of these junctions and demonstrate their unique ability to have large product of a critical current IC and a normal-state resistance RN in the π state, comparable to that in superconductor-insulator-superconductor tunnel junctions commonly used in SFQ circuits. We develop a model describing switching of the Josephson critical current in these devices by external magnetic field. The results are in good agreement with the experimental data for Nb-Al/AlOx-Nb-Pd0.99Fe0.01-Nb junctions.
A matrix model for strings beyond the c=1 barrier: the spin-s Heisenberg model on random surfaces
Ambjorn, J; Sedrakyan, A
2014-01-01
We consider a spin-s Heisenberg model coupled to two-dimensional quantum gravity. We quantize the model using the Feynman path integral, summing over all possible two-dimensional geometries and spin configurations. We regularize this path integral by starting with the R-matrices defining the spin-s Heisenberg model on a regular 2d Manhattan lattice. 2d quantum gravity is included by defining the R-matrices on random Manhattan lattices and summing over these, in the same way as one sums over 2d geometries using random triangulations in non-critical string theory. We formulate a random matrix model where the partition function reproduces the annealed average of the spin-s Heisenberg model over all random Manhattan lattices. A technique is presented which reduces the random matrix integration in partition function to an integration over their eigenvalues.
Cosmic D-strings as Axionic D-term Strings
Blanco-Pillado, J J; Redi, M; Blanco-Pillado, Jose J.; Dvali, Gia; Redi, Michele
2005-01-01
In this work we derive non-singular BPS string solutions from an action that captures the essential features of a D-brane-anti-D-brane system compactified to four dimensions. The model we consider is a supersymmetric abelian Higgs model with a D-term potential coupled to an axion-dilaton multiplet. The strings in question are axionic D-term strings which we identify with the D-strings of type II string theory. In this picture the Higgs field represents the open string tachyon of the D-Dbar pair and the axion is dual to a Ramond Ramond form. The crucial term allowing the existence of non-singular BPS strings is the Fayet-Iliopoulos term, which is related to the tensions of the D-string and of the parent branes. Despite the presence of the axion, the strings are BPS and carry finite energy, due to the fact that the space gets very slowly decompactified away from the core, screening the long range axion field (or equivalently the theory approaches an infinitely weak 4D coupling). Within our 4D effective action w...
Superconductivity of Ag-added composites of Hg-1223 grained Bean model
Energy Technology Data Exchange (ETDEWEB)
Kubo, M.; Akune, T. [Department of Electrical Engineering, Kyushu Sangyo University, 2-3-1 Matsukadai, 813-8503 Fukuoka (Japan); Sakamoto, N. [Department of Electrical Engineering, Kyushu Sangyo University, 2-3-1 Matsukadai, 813-8503 Fukuoka (Japan)], E-mail: saka@te.kyusan-u.ac.jp; Khan, H.R. [Institut von Ionenstrahl und Vakuum Technologie, 73728 Esslingen (Germany); Lueders, K. [Freie Universitaet Berlin, Institut fuer Experimentalphysik, 14 Arnimallee, D-14195 Berlin (Germany)
2007-10-01
High-T{sub c} ceramics tend to lower its quality by the aging effect. The main cause of the degradation is considered to originate in the link region among the superconducting grains. The preservation and recovery of superconductivity by reinforcement of the grain boundary is an important issue for high-T{sub c} application. A quantitative analysis of the contribution due to the grain and link is necessary and the grained Bean model is proposed, where the superconducting phases are immersed in the matrix link superconductor. Difference of the superconducting characteristics of the grain, the link and grain content factor give a variety of deformation on the AC susceptibility curves. Comparing the observed data with the numerically computed model allows more clear insight between the grain and intergrain structure.
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.
Factorization of Chiral String Amplitudes
Huang, Yu-tin; Yuan, Ellis Ye
2016-01-01
We re-examine a closed-string model defined by altering the boundary conditions for one handedness of two-dimensional propagators in otherwise-standard string theory. We evaluate the amplitudes using Kawai-Lewellen-Tye factorization into open-string amplitudes. The only modification to standard string theory is effectively that the spacetime Minkowski metric changes overall sign in one open-string factor. This cancels all but a finite number of states: As found in earlier approaches, with enough supersymmetry (e.g., type II) the tree amplitudes reproduce those of the massless truncation of ordinary string theory. However, we now find for the other cases that additional fields, formerly thought to be auxiliary, describe new spin-2 states at the two adjacent mass levels (tachyonic and tardyonic). The tachyon is always a ghost, but can be avoided in the heterotic case.
Factorization of chiral string amplitudes
Huang, Yu-tin; Siegel, Warren; Yuan, Ellis Ye
2016-09-01
We re-examine a closed-string model defined by altering the boundary conditions for one handedness of two-dimensional propagators in otherwise-standard string theory. We evaluate the amplitudes using Kawai-Lewellen-Tye factorization into open-string amplitudes. The only modification to standard string theory is effectively that the spacetime Minkowski metric changes overall sign in one open-string factor. This cancels all but a finite number of states: as found in earlier approaches, with enough supersymmetry (e.g., type II) the tree amplitudes reproduce those of the massless truncation of ordinary string theory. However, we now find for the other cases that additional fields, formerly thought to be auxiliary, describe new spin-2 states at the two adjacent mass levels (tachyonic and tardyonic). The tachyon is always a ghost, but can be avoided in the heterotic case.
Institute of Scientific and Technical Information of China (English)
Zhang Xu; Wu Zhi-Zhen; Zhou Tie-Ge; He Ming; Zhao Xin-Jie; Yan Shao-Lin; Fang Lan
2011-01-01
The critical current density Jc is one of the most important parameters of high temperature superconducting films in superconducting applications, such as superconducting filter and superconducting Josephson devices. This paper presents a new model to describe inhomogeneous current distribution throughout the thickness of superconducting films applying magnetic field by solving the differential equation derived from Maxwell equation and the second London equation. Using this model, it accurately calculates the inductive third-harmonic voltage when the film applying magnetic field with the inductive measurement for Jc. The theoretic curve is consistent with the experimental results about measuring superconducting film, especially when the third-harmonic voltage just exceeds zero. The Jc value of superconducting films determined by the inductive method is also compared with results measured by four-probe transport method. The agreements between inductive method and transport method are very good.
Dyon Condensation and Dual Superconductivity in Abelian Higgs Model of QCD
Directory of Open Access Journals (Sweden)
B. S. Rajput
2010-01-01
Full Text Available Constructing the effective action for dyonic field in Abelian projection of QCD, it has been demonstrated that any charge (electrical or magnetic of dyon screens its own direct potential to which it minimally couples and antiscreens the dual potential leading to dual superconductivity in accordance with generalized Meissner effect. Taking the Abelian projection of QCD, an Abelian Higgs model, incorporating dual superconductivity and confinement, has been constructed and its representation has been obtained in terms of average of Wilson loop.
Splitting strings on integrable backgrounds
Energy Technology Data Exchange (ETDEWEB)
Vicedo, Benoit
2011-05-15
We use integrability to construct the general classical splitting string solution on R x S{sup 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 {sigma}-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{sub 2}(C). (orig.)
Nonlinear modelling in time domain numerical analysis of stringed instrument dynamics
Bielski, Paweł; Kujawa, Marcin
2017-03-01
Musical instruments are very various in terms of sound quality with their timbre shaped by materials and geometry. Materials' impact is commonly treated as dominant one by musicians, while it is unclear whether it is true or not. The research proposed in the study focuses on determining influence of both these factors on sound quality based on their impact on harmonic composition. Numerical approach has been chosen to allowed independent manipulation of geometrical and material parameters as opposed to experimental study subjected to natural randomness of instrument construction. Distinctive element of this research is precise modelling of whole instrument and treating it as one big vibrating system instead of performing modal analysis on an isolated part. Finite elements model of a stringed instrument has been built and a series of nonlinear time-domain dynamic analyses were executed to obtain displacement signals and perform subsequent spectral analysis. Precision of computations seems sufficient to determine the influence of instrument's macroscopic mechanical parameters on timbre. Further research should focus on implementation of acoustic medium in attempt to include dissipation and synchronization mechanisms. Outside the musical field this kind of research could be potentially useful in noise reduction problems.
String-Inspired Gravity through Symmetries
National Research Council Canada - National Science Library
José Antonio Belinchón
2016-01-01
We study a string-inspired cosmological model from the symmetries point of view. We start by deducing the form that each physical quantity must take so that the field equations, in the string frame, admit self-similar solutions...
Symmetries and Interactions in Matrix String Theory
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
Symmetries and Interactions in Matrix String Theory
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
Feofilov, Grigory; Kochebina, Olga
2015-01-01
Anomalous centrality evolution of two-particle angular correlations observed in Au-Au collisions at $\\sqrt{s_{NN}} = 62$ and 200 GeV and the onset of ridge structures are considered in the model of interacting quark-gluon strings. We assume that at the given energy of nucleus-nucleus collisions the critical energy density may be reached at the specific centrality. In a string percolation model this might be treated equivalently to a formation of a large cluster of strings characterized by the critical string density, with a size comparable to the whole area of interaction of two nuclei. This hypothesis allows to define some constraints on the string percolation model using data on transitional centralities in Au-Au collisions at these two energies. Results are extrapolated to the LHC energy where high string densities (exceeding the critical value) are confirmed for all classes of centralities in Pb-Pb collisions. Interaction between strings inside large clusters formed in nucleus-nucleus collisions is consid...
Agarwal, Shilpi; Pradhan, Anirudh
2010-01-01
The present study deals with a spatially homogeneous and anisotropic Bianchi-II cosmological models representing massive strings in normal gauge for Lyra's manifold by applying the variation law for generalized Hubble's parameter that yields a constant value of deceleration parameter. The variation law for Hubble's parameter generates two types of solutions for the average scale factor, one is of power-law type and other is of the exponential form. Using these two forms, Einstein's modified field equations are solved separately that correspond to expanding singular and non-singular models of the universe respectively. The energy-momentum tensor for such string as formulated by Letelier (1983) is used to construct massive string cosmological models for which we assume that the expansion ($\\theta$) in the model is proportional to the component $\\sigma^{1}_{~1}$ of the shear tensor $\\sigma^{j}_{i}$. This condition leads to $A = (BC)^{m}$, where A, B and C are the metric coefficients and m is proportionality cons...
The Minimal SUSY $B-L$ Model: Simultaneous Wilson Lines and String Thresholds
Deen, Rehan; Purves, Austin
2016-01-01
In previous work, we presented a statistical scan over the soft supersymmetry breaking parameters of the minimal SUSY $B-L$ model. For specificity of calculation, unification of the gauge parameters was enforced by allowing the two ${\\mathbb Z}_{3}\\times {\\mathbb Z}_{3}$ Wilson lines to have mass scales separated by approximately an order of magnitude. This introduced an additional "left-right" sector below the unification scale. In this paper, for three important reasons, we modify our previous analysis by demanding that the mass scales of the two Wilson lines be simultaneous and equal to an "average unification" mass $\\left$. The present analysis is 1) more "natural" than the previous calculations, which were only valid in a very specific region of the Calabi-Yau moduli space, 2) the theory is conceptually simpler in that the left-right sector has been removed and 3) in the present analysis the lack of gauge unification is due to threshold effects--particularly heavy string thresholds, which we calculate st...
The minimal SUSY B - L model: simultaneous Wilson lines and string thresholds
Deen, Rehan; Ovrut, Burt A.; Purves, Austin
2016-07-01
In previous work, we presented a statistical scan over the soft supersymmetry breaking parameters of the minimal SUSY B - L model. For specificity of calculation, unification of the gauge parameters was enforced by allowing the two Z_3× Z_3 Wilson lines to have mass scales separated by approximately an order of magnitude. This introduced an additional "left-right" sector below the unification scale. In this paper, for three important reasons, we modify our previous analysis by demanding that the mass scales of the two Wilson lines be simultaneous and equal to an "average unification" mass . The present analysis is 1) more "natural" than the previous calculations, which were only valid in a very specific region of the Calabi-Yau moduli space, 2) the theory is conceptually simpler in that the left-right sector has been removed and 3) in the present analysis the lack of gauge unification is due to threshold effects — particularly heavy string thresholds, which we calculate statistically in detail. As in our previous work, the theory is renormalization group evolved from to the electroweak scale — being subjected, sequentially, to the requirement of radiative B - L and electroweak symmetry breaking, the present experimental lower bounds on the B - L vector boson and sparticle masses, as well as the lightest neutral Higgs mass of ˜125 GeV. The subspace of soft supersymmetry breaking masses that satisfies all such constraints is presented and shown to be substantial.
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.)
Haghighat, Babak; Iqbal, Amer; Kozçaz, Can; Lockhart, Guglielmo; Vafa, Cumrun
2015-03-01
M2 branes suspended between adjacent parallel M5 branes lead to light strings, the `M-strings'. In this paper we compute the elliptic genus of M-strings, twisted by maximally allowed symmetries that preserve 2 d (2, 0) supersymmetry. In a codimension one subspace of parameters this reduces to the elliptic genus of the (4, 4) supersymmetric A n-1 quiver theory in 2 d. We contrast the elliptic genus of N M-strings with the (4, 4) sigma model on the N-fold symmetric product of . For N = 1 they are the same, but for N > 1 they are close, but not identical. Instead the elliptic genus of (4, 4) N M-strings is the same as the elliptic genus of (4, 0) sigma models on the N-fold symmetric product of , but where the right-moving fermions couple to a modification of the tangent bundle. This construction arises from a dual A n-1 quiver 6 d gauge theory with U(1) gauge groups. Moreover, we compute the elliptic genus of domain walls which separate different numbers of M2 branes on the two sides of the wall.
Haghighat, Babak; Kozcaz, Can; Lockhart, Guglielmo; Vafa, Cumrun
2013-01-01
M2 branes suspended between adjacent parallel M5 branes lead to light strings, the `M-strings'. In this paper we compute the elliptic genus of M-strings, twisted by maximally allowed symmetries that preserve 2d (2,0) supersymmetry. In a codimension one subspace of parameters this reduces to the elliptic genus of the (4,4) supersymmetric A_{n-1} quiver theory in 2d. We contrast the elliptic genus of N M-strings with the (4,4) sigma model on the N-fold symmetric product of R^4. For N=1 they are the same, but for N>1 they are close, but not identical. Instead the elliptic genus of (4,4) N M-strings is the same as the elliptic genus of (4,0) sigma models on the N-fold symmetric product of R^4, but where the right-moving fermions couple to a modification of the tangent bundle. This construction arises from a dual A_{n-1} quiver 6d gauge theory with U(1) gauge groups. Moreover we compute the elliptic genus of domain walls which separate different numbers of M2 branes on the two sides of the wall.
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo, E-mail: paolo.amore@gmail.com [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal Díaz del Castillo 340, Colima, Colima (Mexico); Fernández, Francisco M., E-mail: fernande@quimica.unlp.edu.ar [INIFTA (UNLP, CCT La Plata-CONICET), División Química Teórica, Diag. 113 y 64 (S/N), Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina); Garcia, Javier [INIFTA (UNLP, CCT La Plata-CONICET), División Química Teórica, Diag. 113 y 64 (S/N), Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina); Gutierrez, German [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal Díaz del Castillo 340, Colima, Colima (Mexico)
2014-04-15
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)≡∑{sub n=1}{sup ∞}1/E{sub n}{sup 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.
Perspectives on string phenomenology
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...
First Structure Formation. II. Cosmic String plus Hot Dark Matter Models
Energy Technology Data Exchange (ETDEWEB)
Abel, T. [Laboratory for Computational Astrophysics, National Center for Supercomputing Applications, University of Illinois at Urbana--Champaign, 405 North Mathews Avenue, Urbana, IL 61801 (United States)]|[Max-Planck-Institut fuer Astrophysik, 85748 Garching (Germany); Stebbins, A. [NASA/Fermilab Astrophysics Center, Fermilab, Box 500, Batavia, IL 60510-0500 (United States); Anninos, P. [Laboratory for Computational Astrophysics, National Center for Supercomputing Applications, University of Illinois at Urbana--Champaign, 405 North Mathews Avenue, Urbana, IL 61801 (United States); Norman, M.L. [Laboratory for Computational Astrophysics, National Center for Supercomputing Applications, University of Illinois at Urbana--Champaign, 405 North Mathews Avenue, Urbana, IL 61801 (United States)]|[Max-Planck-Institut fuer Astrophysik, 85748 Garching (Germany)
1998-12-01
We examine the structure of baryonic wakes in the cosmological fluid that would form behind grand unified theory{endash}scale cosmic strings at early times (redshifts {ital z} {approx_gt} 100) in a neutrino-dominated universe. We show, using simple analytical arguments as well as one- and two-dimensional hydrodynamical simulations, that these wakes will {ital not} be able to form interesting cosmological objects before the neutrino component collapses. The width of the baryonic wakes ({approx_lt}10 kpc comoving) is smaller than the scale of wiggles on the strings and is probably not enhanced by the wiggliness of the string network. {copyright} {ital {copyright} 1998.} {ital The American Astronomical Society}
Fermilab Tevatron and CERN LEP II probes of minimal and string-motivated supergravity models
Baer, Howard W; Kao, C; Pois, H
1995-01-01
We explore the ability of the Tevatron to probe Minimal Supersymmetry with high energy scale boundary conditions motivated by supersymmetry breaking in the context of supergravity/superstring theory. A number of boundary condition possibilities are considered: dilaton-like string boundary conditions applied at the standard GUT unification scale or alternatively at the string scale; and extreme (``no-scale'') minimal supergravity boundary conditions imposed at the GUT scale or string scale. For numerous specific cases within each scenario the sparticle spectra are computed and then fed into ISAJET 7.07 so that explicit signatures can be examined in detail. We find that, for some of the boundary condition choices, large regions of parameter space can be explored via same-sign dilepton and isolated trilepton signals. For other choices, the mass reach of Tevatron collider experiments is much more limited. We also compare mass reach of Tevatron experiments with the corresponding reach at LEP 200.
Crisan, Mircea
1989-01-01
This book discusses the most important aspects of the theory. The phenomenological model is followed by the microscopic theory of superconductivity, in which modern formalism of the many-body theory is used to treat most important problems such as superconducting alloys, coexistence of superconductivity with the magnetic order, and superconductivity in quasi-one-dimensional systems. It concludes with a discussion on models for exotic and high temperature superconductivity. Its main aim is to review, as complete as possible, the theory of superconductivity from classical models and methods up t
A multiple-field coupled resistive transition model for superconducting Nb3Sn
Yang, Lin; Ding, He; Zhang, Xin; Qiao, Li
2016-12-01
A study on the superconducting transition width as functions of the applied magnetic field and strain is performed in superconducting Nb3Sn. A quantitative, yet universal phenomenological resistivity model is proposed. The numerical simulation by the proposed model shows predicted resistive transition characteristics under variable magnetic fields and strain, which in good agreement with the experimental observations. Furthermore, a temperature-modulated magnetoresistance transition behavior in filamentary Nb3Sn conductors can also be well described by the given model. The multiple-field coupled resistive transition model is helpful for making objective determinations of the high-dimensional critical surface of Nb3Sn in the multi-parameter space, offering some preliminary information about the basic vortex-pinning mechanisms, and guiding the design of the quench protection system of Nb3Sn superconducting magnets.
The Superconducting Super Collider: A status report
Energy Technology Data Exchange (ETDEWEB)
Schwitters, R.F.
1993-04-01
The design of the Superconducting Super Collider (SSC) is briefly reviewed, including its key machine parameters. The scientific objectives are twofold: (1) investigation of high-mass, low-rate, rare phenomena beyond the standard model; and (2) investigation of processes within the domain of the standard model. Machine luminosity, a key parameter, is a function of beam brightness and current, and it must be preserved through the injector chain. Features of the various injectors are discussed. The superconducting magnet system is reviewed in terms of model magnet performance, including the highly successful Accelerator System String Test Various magnet design modifications are noted, reflecting minor changes in the collider arcs and improved installation procedures. The paper concludes with construction scenarios and priority issues for ensuring the earliest collider commissioning.
Indian Academy of Sciences (India)
S D Katore; R S Rane; K S Wankhade
2011-04-01
Bianchi type-I massive string cosmological model for perfect ﬂuid distribution in the presence of magnetic ﬁeld is investigated in Rosen’s [Gen. Relativ. Gravit. 4, 435 (1973)] bimetric theory of gravitation. To obtain the deterministic model in terms of cosmic time, we have used the condition $A = (B C)^n$, where n is a constant, between the metric potentials. The magnetic ﬁeld is due to the electric current produced along the -axis with inﬁnite electrical conductivity. Some physical and geometrical properties of the exhibited model are discussed and studied.
The minimal SUSY B−L model: simultaneous Wilson lines and string thresholds
Energy Technology Data Exchange (ETDEWEB)
Deen, Rehan; Ovrut, Burt A. [Department of Physics, University of Pennsylvania,209 South 33rd Street, Philadelphia, PA 19104-6396 (United States); Purves, Austin [Department of Physics, University of Pennsylvania,209 South 33rd Street, Philadelphia, PA 19104-6396 (United States); Department of Physics, Manhattanville College,2900 Purchase Street, Purchase, NY 10577 (United States)
2016-07-08
In previous work, we presented a statistical scan over the soft supersymmetry breaking parameters of the minimal SUSY B−L model. For specificity of calculation, unification of the gauge parameters was enforced by allowing the two ℤ{sub 3}×ℤ{sub 3} Wilson lines to have mass scales separated by approximately an order of magnitude. This introduced an additional “left-right” sector below the unification scale. In this paper, for three important reasons, we modify our previous analysis by demanding that the mass scales of the two Wilson lines be simultaneous and equal to an “average unification” mass 〈M{sub U}〉. The present analysis is 1) more “natural” than the previous calculations, which were only valid in a very specific region of the Calabi-Yau moduli space, 2) the theory is conceptually simpler in that the left-right sector has been removed and 3) in the present analysis the lack of gauge unification is due to threshold effects — particularly heavy string thresholds, which we calculate statistically in detail. As in our previous work, the theory is renormalization group evolved from 〈M{sub U}〉 to the electroweak scale — being subjected, sequentially, to the requirement of radiative B−L and electroweak symmetry breaking, the present experimental lower bounds on the B−L vector boson and sparticle masses, as well as the lightest neutral Higgs mass of ∼125 GeV. The subspace of soft supersymmetry breaking masses that satisfies all such constraints is presented and shown to be substantial.
NMR microimaging of fluid flow in model string-type reactors
Koptyug, I.V.; Kovtunov, K.V.; Gerkema, E.; Kiwi-Minskerc, L.; Sagdeev, R.Z.
2007-01-01
Magnetic resonance microimaging (MRM) was employed to obtain quantitative velocity maps of water flowing in the channels possessing unconventional cross-section shapes formed by a bundle of parallel fibers within a tubular string-type reactor. The maps obtained demonstrate the presence of large amou
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)
Pradhan, B.; Goi, S. K.; Behera, Srikanta; Parida, P. K.; Mishra, R. N.
2016-12-01
We have proposed a theoretical model for the coexistence of superconductivity (SC), antiferromagnetism (AFM) and Jahn-Teller (JT) effect in the mean field approximation for iron based superconductors. The model is solved by using Zubarev's double-time Green's function technique to get their selfconsistent gap equations. Then these gap equations are solved numerically.
Cosmic Acceleration and the String Coupling
Ellis, Jonathan Richard; Nanopoulos, Dimitri V; Ellis, John
2005-01-01
In the context of a cosmological string model describing the propagation of strings in a time-dependent Robertson-Walker background space-time, we show that the asymptotic acceleration of the Universe can be identified with the square of the string coupling. This allows for a direct measurement of the ten-dimensional string coupling using cosmological data. We conjecture that this is a generic feature of a class of non-critical string models that approach asymptotically a conformal (critical) sigma model whose target space is a four-dimensional space-time with a dilaton background that is linear in sigma-model time. The relation between the cosmic acceleration and the string coupling does not apply in critical strings with constant dilaton fields in four dimensions.
Progress in string theory research
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...
Improving cosmic string network simulations
Hindmarsh, Mark; Rummukainen, Kari; Tenkanen, Tuomas V. I.; Weir, David J.
2014-08-01
In real-time lattice simulations of cosmic strings in the Abelian Higgs model, the broken translational invariance introduces lattice artifacts; relativistic strings therefore decelerate and radiate. We introduce two different methods to construct a moving string on the lattice, and study in detail the lattice effects on moving strings. We find that there are two types of lattice artifact: there is an effective maximum speed with which a moving string can be placed on the lattice, and a moving string also slows down, with the deceleration approximately proportional to the exponential of the velocity. To mitigate this, we introduce and study an improved discretization, based on the tree-level Lüscher-Weisz action, which is found to reduce the deceleration by an order of magnitude, and to increase the string speed limit by an amount equivalent to halving the lattice spacing. The improved algorithm is expected to be very useful for 3D simulations of cosmic strings in the early Universe, where one wishes to simulate as large a volume as possible.
Improving cosmic string network simulations
Hindmarsh, Mark; Tenkanen, Tuomas V I; Weir, David J
2014-01-01
In real-time lattice simulations of cosmic strings in the Abelian Higgs model, the broken translational invariance introduces lattice artefacts; relativistic strings therefore decelerate and radiate. We introduce two different methods to construct a moving string on the lattice, and study in detail the lattice effects on moving strings. We find that there are two types of lattice artefact: there is an effective maximum speed with which a moving string can be placed on the lattice, and a moving string also slows down, with the deceleration approximately proportional to the exponential of the velocity. To mitigate this, we introduce and study an improved discretisation, based on the tree-level L\\"{u}scher-Weisz action, which is found to reduce the deceleration by an order of magnitude, and to increase the string speed limit by an amount equivalent to halving the lattice spacing. The improved algorithm is expected to be very useful for 3D simulations of cosmic strings in the early universe, where one wishes to s...
Modeling and comparison of superconducting linear actuators for highly dynamic motion
Directory of Open Access Journals (Sweden)
Bruyn B.J.H. de
2015-12-01
Full Text Available This paper presents a numerical modeling method for AC losses in highly dynamic linear actuators with high temperature superconducting (HTS tapes. The AC losses and generated force of two actuators, with different placement of the cryostats, are compared. In these actuators, the main loss component in the superconducting tapes are hysteresis losses, which result from both the non-sinusoidal phase currents and movement of the permanent magnets. The modeling method, based on the H-formulation of the magnetic fields, takes into account permanent magnetization and movement of permanent magnets. Calculated losses as function of the peak phase current of both superconducting actuators are compared to those of an equivalent non-cryogenic actuator.
Triplet FFLO superconductivity in the doped Kitaev-Heisenberg honeycomb model
Liu, Tianhan; Repellin, Cécile; Douçot, Benoît; Regnault, Nicolas; Le Hur, Karyn
2016-11-01
We provide analytical and numerical evidence of spin-triplet Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductivity in the itinerant Kitaev-Heisenberg model (antiferromagnetic Kitaev coupling and ferromagnetic Heisenberg coupling) on the honeycomb lattice around quarter filling. The strong spin-orbit coupling in our model leads to the emergence of six inversion symmetry centers for the Fermi surface at nonzero momenta in the first Brillouin zone. We show how the Cooper pairs condense into these nontrivial momenta, causing spatial modulation of the superconducting order parameter. Applying a Ginzburg-Landau expansion analysis, we find that the superconductivity has three separated degenerate ground states with three different spin-triplet pairings. Exact diagonalizations on finite clusters support this picture while ruling out a spin (charge) density wave.
Forward model theoretical basis for a superconducting imaging surface magnetoencephalography system
Energy Technology Data Exchange (ETDEWEB)
Maharajh, K [University of New Mexico, Albuquerque, NM (United States); Volegov, P L [Los Alamos National Laboratory, Los Alamos, NM (United States); Kraus, R H [Los Alamos National Laboratory, Los Alamos, NM (United States)
2004-02-21
A novel magnetoencephalography (MEG) system was designed at Los Alamos National Laboratory (LANL) that incorporates a helmet-shaped superconductor in order to increase the signal to noise ratio. The magnetic field perturbations caused by the superconducting surface must be included in the forward physics for accurate source localization. In this paper, the theoretical basis for the forward model that calculates the field of any magnetic source in the presence of an arbitrarily shaped superconducting surface is presented. Appropriate magnetic field integral equations are derived that provide a description of the physics of the forward model. These equations are derived starting from Maxwell's equations in the presence of inhomogeneous media, with the appropriate boundary conditions for a superconductor. A discretized version of this equation is then compared with known analytic solutions for simple superconducting surface geometries.
Völlinger, Christine; Russenschuck, Stephan
2001-01-01
Field variations in the LHC superconducting magnets, e. g. during the ramping of the magnets, induce magnetization currents in the superconducting material, the so-called persistent currents that do not decay but persist due to the lack of resistivity. This paper describes a semi-analytical hysteresis model for hard superconductors, which has been developed for the computation of the total field errors arising from persistent currents. Since the superconducting coil is surrounded by a ferromagnetic yoke structure, the persistent current model is combined with the finite element method (FEM), as the non-linear yoke can only be calculated numerically. The used finite element method is based on a reduced vector potential formulation that avoids the meshing of the coil while calculating the part of the field arising from the source currents by means of the Biot-Savart Law. The combination allows to determine persistent current induced field errors as function of the excitation and for arbitrarily shaped iron yoke...
Two-dimensional lattice gauge theories with superconducting quantum circuits
Energy Technology Data Exchange (ETDEWEB)
Marcos, D., E-mail: david.marcos@me.com [Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck (Austria); Widmer, P. [Albert Einstein Center, Institute for Theoretical Physics, Bern University, CH-3012, Bern (Switzerland); Rico, E. [IPCMS (UMR 7504) and ISIS (UMR 7006), University of Strasbourg and CNRS, 67000 Strasbourg (France); Hafezi, M. [Joint Quantum Institute, NIST/University of Maryland, College Park 20742 (United States); Department of Electrical Engineering and Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742 (United States); Rabl, P. [Institute of Atomic and Subatomic Physics, TU Wien, Stadionallee 2, 1020 Wien (Austria); Wiese, U.-J. [Albert Einstein Center, Institute for Theoretical Physics, Bern University, CH-3012, Bern (Switzerland); Zoller, P. [Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck (Austria); Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria)
2014-12-15
A quantum simulator of U(1) lattice gauge theories can be implemented with superconducting circuits. This allows the investigation of confined and deconfined phases in quantum link models, and of valence bond solid and spin liquid phases in quantum dimer models. Fractionalized confining strings and the real-time dynamics of quantum phase transitions are accessible as well. Here we show how state-of-the-art superconducting technology allows us to simulate these phenomena in relatively small circuit lattices. By exploiting the strong non-linear couplings between quantized excitations emerging when superconducting qubits are coupled, we show how to engineer gauge invariant Hamiltonians, including ring-exchange and four-body Ising interactions. We demonstrate that, despite decoherence and disorder effects, minimal circuit instances allow us to investigate properties such as the dynamics of electric flux strings, signaling confinement in gauge invariant field theories. The experimental realization of these models in larger superconducting circuits could address open questions beyond current computational capability.
Directory of Open Access Journals (Sweden)
Guoli Wang
2013-09-01
Full Text Available The finite element model of the 1000kV Ultra High Voltage (UHV AC transmission line porcelain insulator string voltage distribution and grading ring surface electric field distribution calculation has the characteristics of large size, complicated structure and various mediums. To insure the accuracy, related influencing factors should be considered to simplify the model reasonably for improving computational efficiency. A whole model and a simplified 3D finite element model of UHV AC transmission line porcelain insulator string were built. The influencing factors including tower, phase conductors, hardware fittings, yoke plate and phase interaction were considered in the analysis. And finally, the rationality of the simplified model was validated. The results comparison show that building a simplified model of three-phase bundled conductors within a certain length, simplifying the tower reasonably, omitting the hardware fittings and yoke plate and containing only single-phase insulator string model is feasible. The simplified model could replace the whole model to analyze the voltage distribution along the porcelain insulator string and the electric field distribution on the grading ring surface, and it can reduce the calculation scale, improve optimization efficiency of insulators string and grading ring parameters.
A Novel String Field Theory Solving String Theory by Liberating Left and Right Mover
Nielsen, Holger B
2012-01-01
We put forward ideas to a novel string field theory based on making some "objects" that essentially describe "liberated" left- and right- mover fields $X^{\\mu}_{L}(\\tau + \\sigma)$ and $X^{\\mu}_{R}(\\tau - \\sigma)$ on the string. The main progress is that we manage to make our novel string field theory provide the correct mass square spectrum for the string. An interesting detail is that we have to dispense of a species doubler caused by the discretization we introduced in our string field theory of the string right- and left- mover variables. We finally suggest how to obtain the Veneziano amplitude in our model.
p-adic string theories provide lattice Discretization to the ordinary string worldsheet.
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.
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…
D-Branes at Singularities A Bottom-Up Approach to the String Embedding of the Standard Model
Aldazabal, G; Quevedo, Fernando; Uranga, Angel M
2000-01-01
We propose a bottom-up approach to the building of particle physics models from string theory. Our building blocks are Type II D-branes which we combine appropriately to reproduce desirable features of a particle theory model: 1) Chirality ; 2) Standard Model group ; 3) N=1 or N=0 supersymmetry ; 4) Three quark-lepton generations. We start such a program by studying configurations of D=10, Type IIB D3-branes located at singularities. We study in detail the case of Z_N, N=1,0 supersymmetric orbifold singularities leading to the SM group or some left-right symmetricextension. In general, tadpole cancellation conditions require the presence of additional branes, e.g. D7-branes. For the N=1 supersymmetric case the unique twist leading to three quark-lepton generations is Z_3, predicting $\\sin^2\\theta_W=3/14=0.21$. The models obtained are the simplest semirealistic string models ever built. In the non-supersymmetric case there is a three-generation model for each Z_N, N>4, but the Weinberg angle is in general too ...
D-Branes at Singularities A Bottom-Up Approach to the String Embedding of the Standard Model
Aldazabal, G.; Quevedo, F.; Uranga, A.M.
2000-01-01
We propose a bottom-up approach to the building of particle physics models from string theory. Our building blocks are Type II D-branes which we combine appropriately to reproduce desirable features of a particle theory model: 1) Chirality ; 2) Standard Model group ; 3) N=1 or N=0 supersymmetry ; 4) Three quark-lepton generations. We start such a program by studying configurations of D=10, Type IIB D3-branes located at singularities. We study in detail the case of Z_N, N=1,0 supersymmetric orbifold singularities leading to the SM group or some left-right symmetricextension. In general, tadpole cancellation conditions require the presence of additional branes, e.g. D7-branes. For the N=1 supersymmetric case the unique twist leading to three quark-lepton generations is Z_3, predicting $\\sin^2\\theta_W=3/14=0.21$. The models obtained are the simplest semirealistic string models ever built. In the non-supersymmetric case there is a three-generation model for each Z_N, N>4, but the Weinberg angle is in general too ...
Institute of Scientific and Technical Information of China (English)
N. P. Gaikwad; M. S. Borkar; S. S. Charjan
2011-01-01
@@ We investigate the Bianchi type-I massive string magnetized barotropic perfect fluid cosmological model in Rosen's bimetric theory of gravitation with and without a magnetic field by applying the techniques used by Latelier(1979,1980) and Stachel(1983).To obtain a deterministic model of the universe, it is assumed that the universe is filled with barotropic perfect fluid distribution.The physical and geometrical significance of the model are discussed.By comparing our model with the model of Bali et al.(2007), it is realized that there are no big-bang and big-crunch singularities in our model and T＝0 is not the time of the big bang, whereas the model of Bali et al.starts with a big bang at T=0.Further, our model is in agreement with Bali et al.(2007) as time increases in the presence, as well as in the absence, of a magnetic field.
A double-superconducting axial bearing system for an energy storage flywheel model
Energy Technology Data Exchange (ETDEWEB)
Deng, Z; Lin, Q; Ma, G; Zheng, J; Zhang, Y; Wang, S; Wang, J [Applied Superconductivity Laboratory, Mail Stop 152, Southwest Jiaotong University, Chengdu, 610031 (China)], E-mail: jsywang@home.swjtu.edu.cn
2008-02-15
The bulk high temperature superconductors (HTSCs) with unique flux-pinning property have been applied to fabricate two superconducting axial bearings for an energy storage flywheel model. The two superconducting axial bearings are respectively fixed at two ends of the vertical rotational shaft, whose stator is composed of seven melt-textured YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) bulks with diameter of 30 mm, height of 18 mm and rotor is made of three cylindrical axial-magnetized NdFeB permanent magnets (PM) by superposition with diameter of 63 mm, height of 27 mm. The experimental results show the total levitation and lateral force produced by the two superconducting bearings are enough to levitate and stabilize the 2.4 kg rotational shaft. When the two YBCO stators were both field cooled to the liquid nitrogen temperature at respective axial distances above or below the PM rotor, the shaft could be automatically levitated between the two stators without any contact. In the case of a driving motor, it can be stably rotated along the central axis besides the resonance frequency. This double-superconducting axial bearing system can be used to demonstrate the flux-pinning property of bulk HTSC for stable levitation and suspension and the principle of superconducting flywheel energy storage system to visitors.
The 750 GeV di-photon LHC excess and extra Z's in heterotic-string derived models
Energy Technology Data Exchange (ETDEWEB)
Faraggi, Alon E. [University of Liverpool, Department of Mathematical Sciences, Liverpool (United Kingdom); Rizos, John [University of Ioannina, Department of Physics, Ioannina (Greece)
2016-03-15
The ATLAS and CMS collaborations recently recorded possible di-photon excess at 750 GeV and a less significant di-boson excess around 1.9 TeV. Such excesses may be produced in heterotic string derived Z' models, where the di-photon excess may be connected with the Standard Model singlet scalar responsible for the Z' symmetry breaking, whereas the di-boson excess arises from production of the extra vector boson. Additional vector-like states in the string Z' model are instrumental to explain the relatively large width of the di-photon events and mandated by anomaly cancellation to be in the vicinity of the Z' breaking scale. Wilson line breaking of the non-Abelian gauge symmetries in the string models naturally gives rise to dark matter candidates. Future collider experiments will discriminate between the high-scale heterotic-string models, which preserve the perturbative unification paradigm indicated by the Standard Model data, versus the low scale string models.We also discuss the possibility for the production of the diphoton events with high scale U(1){sub Z'} breaking. (orig.)
First-order superconducting transition in the inter-band model
Energy Technology Data Exchange (ETDEWEB)
Gomes da Silva, M. [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-00 Manaus, AM (Brazil); Instituto Federal de Educação Ciência e Tecnologia do Amazonas, Av. 7 de Setembro, 1975 - Centro, Manaus, AM 69020-120 (Brazil); Dinóla Neto, F., E-mail: dinola@ufam.edu.br [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-00 Manaus, AM (Brazil); Padilha, I.T. [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-00 Manaus, AM (Brazil); Ricardo de Sousa, J. [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-00 Manaus, AM (Brazil); National Institute of Science and Technology for Complex Systems, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus, AM (Brazil); Continentino, M.A. [Centro Brasileiro de Pesquisas Físicas, 22290-180 Rio de Janeiro, RJ (Brazil)
2014-04-01
The comprehension about the theoretical features of superconductivity is an interesting and fundamental topic in condensed matter physics. Several theoretical proposals were considered to describe the new classes of superconducting compounds and alloys. In this work we propose to study a non-conventional superconducting system where the Cooper pairs are formed by fermions from different bands described via two band model with hybridization. In this inter-band scenario we find a first-order phase transition at low temperatures and we observe a tricritical point in the phase diagram. In our description, the control parameter is the hybridization that can be tuned by external pressure. This fact indicates the possibility to observe discontinuities in the SC gap amplitude through applying pressure on the system.
Superconducting phase and pairing fluctuations in the half-filled two-dimensional Hubbard model.
Sentef, Michael; Werner, Philipp; Gull, Emanuel; Kampf, Arno P
2011-09-16
The two-dimensional Hubbard model exhibits superconductivity with d-wave symmetry even at half-filling in the presence of a next-nearest neighbor hopping. Using plaquette cluster dynamical mean-field theory with a continuous-time quantum Monte Carlo impurity solver, we reveal the non-Fermi liquid character of the metallic phase in proximity to the superconducting state. Specifically, the low-frequency scattering rate for momenta near (π, 0) varies nonmonotonically at low temperatures, and the dc conductivity is T linear at elevated temperatures with an upturn upon cooling. Evidence is provided that pairing fluctuations dominate the normal-conducting state even considerably above the superconducting transition temperature.
Measurement and Modeling of Magnetic Hysteresis in the LHC Superconducting Correctors
Venturini-Delsolaro, W; Chaudhari, Y; Karppinen, M; Sammut, N
2006-01-01
The Large Hadron Collider, now under construction at CERN, relies heavily on superconducting magnets for its optics layout: besides the main magnets, almost all the correcting magnets are superconducting. Along with clear advantages, this brings about complications due to the effects of persistent currents in the superconducting filaments. Corrector magnets that trim key beam parameters or compensate field errors of the main magnets (among others those due to hysteresis), are in their turn hysteretic. In this paper we present the measured magnetic hysteresis and its possible influence on accelerator operation, with particular reference to realtime compensation of dynamic effects in the main magnets, and reproducibility issues between runs. The modeling strategy as a function of the required accuracy is discussed, and two examples are presented.
Two-stage dissipation in a superconducting microbridge: experiment and modeling
Energy Technology Data Exchange (ETDEWEB)
Del Rio, L; Altshuler, E [Superconductivity Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba); Niratisairak, S; Haugen, Oe; Johansen, T H [Department of Physics, University of Oslo, 0316 Oslo (Norway); Davidson, B A [INFM-TASC Area Science Park, Basovizza (Italy); Testa, G; Sarnelli, E [Cybernetic Institute of the CNR, Via Campi Flegrei 34, 80078, Pozzuoli (Italy)
2010-08-15
Using fluorescent microthermal imaging we have investigated the origin of 'two-step' behavior in I-V curves for a current-carrying YBa{sub 2}Cu{sub 3}O{sub x} superconducting bridge. High resolution temperature maps reveal that as the applied current increases the first step in the voltage corresponds to local dissipation (hot spot), whereas the second step is associated with the onset of global dissipation throughout the entire bridge. A quantitative explanation of the experimental results is provided by a simple model for an inhomogeneous superconductor, assuming that the hot spot nucleates at a location with slightly depressed superconducting properties.
p-wave superconductivity in a two-dimensional generalized Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Millan, J. Samuel [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico (UNAM), Apartado Postal 70-360, 04510, Mexico D.F. (Mexico); Facultad de Ingenieria, UNACAR, 24180, Cd. de Carmen, Campeche (Mexico); Perez, Luis A. [Instituto de Fisica, UNAM, Apartado Postal 20-364, 01000, Mexico D.F. (Mexico); Wang Chumin [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico (UNAM), Apartado Postal 70-360, 04510, Mexico D.F. (Mexico)]. E-mail: chumin@servidor.unam.mx
2005-02-21
In this Letter, we consider a two-dimensional Hubbard model that includes a second-neighbor correlated hopping interaction, and we find a triplet p-wave superconducting ground state within the BCS formalism. A small distortion of the square-lattice right angles is introduced in order to break the degeneracy of kx+/-ky oriented p-wave pairing states. For the strong coupling limit, analytical results are obtained. An analysis of the superconducting critical temperature reveals the existence of an optimal electron density and the gap ratio exhibits a non-BCS behavior. Finally, the particular case of strontium ruthenate is examined.
Universal limiting pressure for a three-flavor color superconducting PNJL model phase diagram
Ayriyan, A; Blaschke, D; Lastowiecki, R
2016-01-01
The phase diagram of a three-flavor Polyakov-loop Nambu-Jona-Lasinio model is analyzed for the case of isospin symmetric matter with color superconducting phases. The coexistence of chiral symmetry breaking and two-flavor color superconductivity (2SC phase) and a thermodynamic instability due to the implementation of a color neutrality constraint is observed. It is suggested to use a universal hadronization pressure to estimate the phase border between hadronic and quark-gluon plasma phases. Trajectories of constant entropy per baryon are analyzed for conditions appropriate for heavy-ion collisions in the NICA-FAIR energy range.
Introduction to the relativistic string theory
Barbashov, B M
1990-01-01
This book presents a systematic and detailed account of the classical and quantum theory of the relativistic string and some of its modifications. Main attention is paid to the first-quantized string theory with possible applications to the string models of hadrons as well as to the superstring approach to unifications of all the fundamental interactions in the elementary particle physics and to the "cosmic" strings. Some new aspects are provided such as the consideration of the string in an external electromagnetic field and in the space-time of constant curvature (the de Sitter universe), th
Ultrasensitive string-based temperature sensors
DEFF Research Database (Denmark)
Larsen, Tom; Schmid, Silvan; Gronberg, L.;
2011-01-01
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...... 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....
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.
Gauge Mediation in String Theory
Kawano, Teruhiko; Ooguri, Hirosi; Ookouchi, Yutaka
2007-01-01
We show that a large class of phenomenologically viable models for gauge mediation of supersymmetry breaking based on meta-stable vacua can be realized in local Calabi–Yau compactifications of string theory.
Directory of Open Access Journals (Sweden)
Alex Elías-Zúñiga
2013-01-01
Full Text Available This work focuses on the formulation of a constitutive equation to predict Mullins and residual strain effects of buna-N, silicone, and neoprene rubber strings subjected to small transverse vibrations. The nonmonotone behavior exhibited by experimental data is captured by the proposed material model through the inclusion of a phenomenological non-monotonous softening function that depends on the strain intensity between loading and unloading cycles. It is shown that theoretical predictions compare well with uniaxial experimental data collected from transverse vibration tests.
Modeling heat transfer from quench protection heaters to superconducting cables in Nb3Sn magnets
Salmi, T; Caspi, S; Felice, H; Prestemon, S; Chlachidze, G; Kate, H H J ten
2013-01-01
We use a recently developed quench protection heater modeling tool for an analysis of heater delays in superconducting high-field Nb3Sn accelerator magnets. The results suggest that the calculated delays are consistent with experimental data, and show how the heater delay depends on the main heater design parameters.
Energy Technology Data Exchange (ETDEWEB)
Blackburn, J.A. (Department of Physics and Computing, Wilfrid Laurier University, Waterloo, ON (Canada)); Smith, H.J.T. (Department of Physics, University of Waterloo, Waterloo, ON (Canada))
1990-09-01
Software packages are now available with which complex analog electronic circuits can be simulated on desktop computers. Using Micro Cap III it is demonstrated that the modeling capabilities of such software can be extended to include {ital superconducting} networks by means of an appropriate equivalent circuit for a Josephson junction.
DEFF Research Database (Denmark)
Bech, Jakob Ilsted; Eriksen, Morten; Toussaint, F.
2000-01-01
Silver/BSCCO composite superconducting tapes are produced using BSCCO-2212 ceramic powder. The manufacturing process implies a large number of forming operations including drawing and rolling. The numerical simulation of the flat rolling process is of a great interest to anticipate the shape....../Prager-Cap plasticity model. Then these data are used to perform the simulation of the wire rolling step....
LHC Phenomenology for String Hunters
Anchordoqui, Luis A; Lüst, Dieter; Nawata, Satoshi; Stieberger, Stephan; Taylor, Tomasz R
2009-01-01
We consider extensions of the standard model based on open strings ending on D-branes, with gauge bosons due to strings attached to stacks of D-branes and chiral matter due to strings stretching between intersecting D-branes. Assuming that the fundamental string mass scale is in the TeV range and the theory is weakly coupled, we discuss possible signals of string physics at the Large Hadron Collider (LHC). In previous works, direct channel excitations of Regge recurrences in parton-parton scattering supplied the outstanding new signature. The present work considers the deviation from standard model expectations for the 4-fermion processes qq\\to qq and qq' \\to qq', in which the s-channel excitation of string resonances is absent. In this case, we find that Kaluza-Klein recurrences at masses somewhat less than the string scale generate effective 4-fermion contact terms which can significantly enhance the dijet R ratio above its QCD value of about 0.6. The simultaneous observation of a nearby resonant structure ...
Energy Technology Data Exchange (ETDEWEB)
Ashfaque, J. [University of Liverpool, Department of Mathematical Sciences, Liverpool (United Kingdom); Delle Rose, L. [University of Southampton, School of Physics and Astronomy, Southampton (United Kingdom); Faraggi, A.E. [Rutherford Appleton Laboratory, Department of Particle Physics, Chilton, Didcot (United Kingdom); Marzo, C. [Universita del Salento, Dipartimento di Matematica e Fisica ' ' Ennio De Giorgi' ' , Lecce (Italy); INFN, Lecce (Italy)
2016-10-15
A di-photon excess at the LHC can be explained as a Standard Model singlet that is produced and decays by heavy vector-like colour triplets and electroweak doublets in one-loop diagrams. The characteristics of the required spectrum are well motivated in heterotic-string constructions that allow for a light Z{sup '}. Anomaly cancellation of the U(1){sub Z'} symmetry requires the existence of the Standard Model singlet and vector-like states in the vicinity of the U(1){sub Z'} breaking scale. In this paper we show that the agreement with the gauge coupling data at one-loop is identical to the case of the Minimal Supersymmetric Standard Model, owing to cancellations between the additional states. We further show that effects arising from heavy thresholds may push the supersymmetric spectrum beyond the reach of the LHC, while maintaining the agreement with the gauge coupling data. We show that the string-inspired model can indeed produce an observable signal and discuss the feasibility of obtaining viable scalar mass spectrum. (orig.)
Ashfaque, J; Faraggi, A E; Marzo, C
2016-01-01
The di-photon excess observed at the LHC can be explained as a Standard Model singlet that is produced and decays by heavy vector-like colour triplets and electroweak doublets in one-loop diagrams. The characteristics of the required spectrum are well motivated in heterotic-string constructions that allow for a light $Z^\\prime$. Anomaly cancellation of the $U(1)_{Z^\\prime}$ symmetry requires the existence of the Standard Model singlet and vector-like states in the vicinity of the $U(1)_{Z^\\prime}$ breaking scale. In this paper we show that the agreement with the gauge coupling data at one-loop is identical to the case of the Minimal Supersymmetric Standard Model, owing to cancellations between the additional states. We further show that effects arising from heavy thresholds may push the supersymmetric spectrum beyond the reach of the LHC, while maintaining the agreement with the gauge coupling data. We show that the string inspired model can indeed account for the observed signal and discuss the feasibility o...
CMB Constraints on Cosmic Strings and Superstrings
Charnock, Tom; Copeland, Edmund J; Moss, Adam
2016-01-01
We present the first complete MCMC analysis of cosmological models with evolving cosmic (super)string networks, using the Unconnected Segment Model in the unequal-time correlator formalism. For ordinary cosmic string networks, we derive joint constraints on {\\Lambda}CDM and string network parameters, namely the string tension G{\\mu}, the loop-chopping efficiency c_r and the string wiggliness {\\alpha}. For cosmic superstrings, we obtain joint constraints on the fundamental string tension G{\\mu}_F, the string coupling g_s, the self-interaction coefficient c_s, and the volume of compact extra dimensions w. This constitutes the most comprehensive CMB analysis of {\\Lambda}CDM cosmology + strings to date. For ordinary cosmic string networks our updated constraint on the string tension is, in relativistic units, G{\\mu}<1.1x10^-7, while for cosmic superstrings our constraint on the fundamental string tension is G{\\mu}_F<2.8x10^-8, both obtained using Planck2015 temperature and polarisation data.
Balanced metrics and phenomenological aspects of heterotic string compactifications
Brelidze, Tamaz
compactifications with the MSSM spectrum. These vacua have the SU(3) C x SU(2)L x U(1)Y gauge group of the standard model augmented by additional an U(1) B-L. The B-L symmetry is spontaneously broken by a vacuum expectation value of one of the right-handed sneutrinos, which leads to U(1)B-L cosmic string solutions. We present a numerical analysis that demonstrates that boson condensates can, in principle, form for theories of this type. However, the weak Yukawa and gauge couplings of the right-handed sneutrino suggests that bosonic superconductivity will not occur in the simplest vacua in this context. Fermion superconductivity is also disallowed by the electroweak phase transition, although bound state fermion currents can exist.
Sumitomo, Yoske; Wong, Sam S C
2013-01-01
We study a racetrack model in the presence of the leading alpha'-correction in flux compactification in Type IIB string theory, for the purpose of getting conceivable de-Sitter vacua in the large compactified volume approximation. Unlike the K\\"ahler Uplift model studied previously, the alpha'-correction is more controllable for the meta-stable de-Sitter vacua in the racetrack case since the constraint on the compactified volume size is very much relaxed. We find that the vacuum energy density \\Lambda for de-Sitter vacua approaches zero exponentially as the volume grows. We also analyze properties of the probability distribution of \\Lambda in this class of models. As in other cases studied earlier, the probability distribution again peaks sharply at \\Lambda=0. We also study the Racetrack K\\"ahler Uplift model in the Swiss-Cheese type model.
Chernodub, M. N.
2011-04-01
Using an extended Nambu-Jona-Lasinio model as a low-energy effective model of QCD, we show that the vacuum in a strong external magnetic field (stronger than 1016T) experiences a spontaneous phase transition to an electromagnetically superconducting state. The unexpected superconductivity of, basically, empty space is induced by emergence of quark-antiquark vector condensates with quantum numbers of electrically charged rho mesons. The superconducting phase possesses an anisotropic inhomogeneous structure similar to a periodic Abrikosov lattice in a type-II superconductor. The superconducting vacuum is made of a new type of vortices which are topological defects in the charged vector condensates. The superconductivity is realized along the axis of the magnetic field only. We argue that this effect is absent in pure QED.
A novel string field theory solving string theory by liberating left and right movers
Energy Technology Data Exchange (ETDEWEB)
Nielsen, Holger B. [Niels Bohr Institute, University of Copenhagen,17 Belgdamsvej, DK 2100 (Denmark); Ninomiya, Masao [Okayama Institute for Quantum Physics,Kyoyama 1-9-1 Kita-ku, Okayama-city 700-0015 (Japan)
2014-05-08
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{sub L}{sup μ}(τ+σ) and X{sub R}{sup 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.
Energy Technology Data Exchange (ETDEWEB)
Ecker, Jill
2016-07-27
In this doctoral thesis, various aspects of string model building and phenomenology are investigated within the framework of Type IIA string theory on the T{sup 6}/(Z{sub 2} x Z{sub 6} x ΩR) orbifold with discrete torsion. The aim is the reproduction of supersymmetric versions of well-known particle physics models using intersecting rigid D6-branes wrapped on fractional three-cycles. The models analyzed include the minimal supersymmetric Standard Model as well as supersymmetric Pati-Salam models, left-right symmetric models and SU(5) models. Systematic computer scans test numerous combinations of intersecting D6-branes in order to detect those that give rise to the correct chiral particle content of the considered models. For each type of the afore mentioned models, concrete examples will be found which satisfy the constraints on the particle spectrum and fulfill all consistency conditions. Finally, the thesis focuses on phenomenological aspects of the particle physics models found, including the detection of massless U(1) combinations, discrete Z{sub n}-symmetries and cubic couplings such as the Yukawa couplings.
Models of high-Tc superconductivity and applications to electric generators and motors
DEFF Research Database (Denmark)
Sørensen, Mads Peter
We present the Ginzburg Landau model for mesoscopic high-Tc superconductors of complex geometry. It is shown that giant vortices can form at boundary defects. The relation between total magnetic flux penetration through the superconductor and the externally applied field is established. This is i....... This is in turn used in modelling high-Tc superconducting generators proposed for windmills in the project SuperWind (http://www.superwind.dk)....
Magnetic design and modelling of a 14 mm-period prototype superconducting undulator.
Mishra, G; Gehlot, Mona; Sharma, Geetanjali; Trillaud, Frederic
2017-03-01
The magnetic design of a ten-period (each period 14 mm) prototype superconducting undulator is reported using RADIA. The results of modelling the magnetic flux density are presented in an analytical formula. The dependence of the field integrals and phase error on the current density and undulator gap has been calculated, and temperature curves are determined for the models and are compared with earlier reported Moser-Rossmanith fits.
3D multiphysics modeling of superconducting cavities with a massively parallel simulation suite
Directory of Open Access Journals (Sweden)
Oleksiy Kononenko
2017-10-01
Full Text Available Radiofrequency cavities based on superconducting technology are widely used in particle accelerators for various applications. The cavities usually have high quality factors and hence narrow bandwidths, so the field stability is sensitive to detuning from the Lorentz force and external loads, including vibrations and helium pressure variations. If not properly controlled, the detuning can result in a serious performance degradation of a superconducting accelerator, so an understanding of the underlying detuning mechanisms can be very helpful. Recent advances in the simulation suite ace3p have enabled realistic multiphysics characterization of such complex accelerator systems on supercomputers. In this paper, we present the new capabilities in ace3p for large-scale 3D multiphysics modeling of superconducting cavities, in particular, a parallel eigensolver for determining mechanical resonances, a parallel harmonic response solver to calculate the response of a cavity to external vibrations, and a numerical procedure to decompose mechanical loads, such as from the Lorentz force or piezoactuators, into the corresponding mechanical modes. These capabilities have been used to do an extensive rf-mechanical analysis of dressed TESLA-type superconducting cavities. The simulation results and their implications for the operational stability of the Linac Coherent Light Source-II are discussed.
Silverstein, Eva
2015-01-01
Following the 2015 Planck release, we briefly comment on the status and some ongoing opportunities in the interface between inflationary cosmology, string theory, and CMB data. The constraints in the $r$-$n_s$ plane introduce a new parameter into inflationary cosmology relative to the simplest quadratic inflation model, in a direction which fits well with couplings to heavy fields as occurs in string theory. The precision of the data permits further searches for and constraints on additional model-dependent features, such as oscillatory $N$-spectra, a program requiring specific theoretically motivated shapes. Since the perturbations can easily be affected by additional sectors and couplings, null results can usefully bound such contributions. We also review the broader lessons string theory has contributed to our understanding of primordial inflation, and close with some approaches to a more complete framework. Published in a special volume of Comptes Rendus on Inflation: Theoretical and Observational Status.
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
String moduli inflation. An overview
Energy Technology Data Exchange (ETDEWEB)
Cicoli, Michele [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Quevedo, Fernando [Cambridge Univ. (United Kingdom). DAMTP/CMS; Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)
2011-06-15
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 {eta}-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.)
String moduli inflation: an overview
Energy Technology Data Exchange (ETDEWEB)
Cicoli, Michele [Deutsches Elektronen-Synchrotron DESY, Notkestrasse, 22607 Hamburg (Germany); Quevedo, Fernando, E-mail: michele.cicoli@desy.de, E-mail: F.Quevedo@damtp.cam.ac.uk [DAMTP, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)
2011-10-21
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 {eta}-problem and different approaches to address it, we describe possible ways to obtain a de Sitter vacuum with all closed string moduli stabilized. 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.
Tadpole Resummations in String Theory
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 ...
Toward A Nonperturbative Topological String
Neitzke, A
2005-01-01
We discuss three examples of nonperturbative phenomena in the topological string. First, we consider the computation of amplitudes in N = 4 super Yang-Mills theory using the B model topological string as proposed by Witten. We give an argument suggesting that the computations using connected or disconnected D-instantons of the B model are in fact equivalent. Second, we formulate a conjecture that the squared modulus of the open topological string partition function can be defined nonperturbatively as the partition function of a mixed ensemble of BPS states in d = 4. This conjecture is an extension of a recent proposal for the closed topological string. In a particular example involving a non-compact Calabi- Yau threefold, we show that the conjecture passes some basic checks, and that the square of the open topological string amplitude has a natural interpretation in terms of 2-dimensional Yang-Mills theory, again generalizing known results for the closed string case. Third, we discuss an action for an abel...
Unoriented Minimal Type 0 Strings
Carlisle, J E; Carlisle, James E; Johnson, Clifford V
2004-01-01
We define a family of string equations with perturbative expansions that admit an interpretation as an unoriented minimal string theory with background D-branes and R-R fluxes. The theory also has a well-defined non-perturbative sector and we expect it to have a continuum interpretation as an orientifold projection of the non-critical type~0A string for \\hat{c}=0, the (2,4) model. There is a second perturbative region which is consistent with an interpretation in terms of background R-R fluxes. We identify a natural parameter in the formulation that we speculate may have an interpretation as characterizing the contribution of a new type of background D-brane. There is a non-perturbative map to a family of string equations which we expect to be the \\hat{c}=0 type 0B string. The map exchanges D-branes and R-R fluxes. We present the general structure of the string equations for the (2,4k) type 0A models.
Rohrbach, F; Vesztergombi, G
1997-01-01
In the near future, the computer performance will be completely determined by how long it takes to access memory. There are bottle-necks in memory latency and memory-to processor interface bandwidth. The IRAM initiative could be the answer by putting Processor-In-Memory (PIM). Starting from the massively parallel processing concept, one reached a similar conclusion. The MPPC (Massively Parallel Processing Collaboration) project and the 8K processor ASTRA machine (Associative String Test bench for Research \\& Applications) developed at CERN \\cite{kuala} can be regarded as a forerunner of the IRAM concept. The computing power of the ASTRA machine, regarded as an IRAM with 64 one-bit processors on a 64$\\times$64 bit-matrix memory chip machine, has been demonstrated by running statistical physics algorithms: one-dimensional stochastic cellular automata, as a simple model for dynamical phase transitions. As a relevant result for physics, the damage spreading of this model has been investigated.
Indian Academy of Sciences (India)
C P Burgess
2004-12-01
The inflationary paradigm provides a robust description of the peculiar initial conditions which are required for the success of the hot Big Bang model of cosmology, as well as of the recent precision measurements of temperature fluctuations within the cosmic microwave background. 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 has (so far) proven to be a hunt for a fairly elusive quarry. This article summarizes some of the recent efforts along these lines, and draws some speculative conclusions as to what the difficulty in finding inflation might mean.
Thermodynamical string fragmentation
Fischer, Nadine; Sjöstrand, Torbjörn
2017-01-01
The observation of heavy-ion-like behaviour in pp collisions at the LHC suggests that more physics mechanisms are at play than traditionally assumed. The introduction e.g. of quark-gluon plasma or colour rope formation can describe several of the observations, but as of yet there is no established paradigm. In this article we study a few possible modifications to the Pythia event generator, which describes a wealth of data but fails for a number of recent observations. Firstly, we present a new model for generating the transverse momentum of hadrons during the string fragmentation process, inspired by thermodynamics, where heavier hadrons naturally are suppressed in rate but obtain a higher average transverse momentum. Secondly, close-packing of strings is taken into account by making the temperature or string tension environment-dependent. Thirdly, a simple model for hadron rescattering is added. The effect of these modifications is studied, individually and taken together, and compared with data mainly from the LHC. While some improvements can be noted, it turns out to be nontrivial to obtain effects as big as required, and further work is called for.
Thermodynamical String Fragmentation
Fischer, Nadine
2016-01-01
The observation of heavy-ion-like behaviour in pp collisions at the LHC suggests that more physics mechanisms are at play than traditionally assumed. The introduction e.g. of quark-gluon plasma or colour rope formation can describe several of the observations, but as of yet there is no established paradigm. In this article we study a few possible modifications to the Pythia event generator, which describes a wealth of data but fails for a number of recent observations. Firstly, we present a new model for generating the transverse momentum of hadrons during the string fragmentation process, inspired by thermodynamics, where heavier hadrons naturally are suppressed in rate but obtain a higher average transverse momentum. Secondly, close-packing of strings is taken into account by making the temperature or string tension environment-dependent. Thirdly, a simple model for hadron rescattering is added. The effect of these modifications is studied, individually and taken together, and compared with data mainly from...
Cosmic strings with twisted magnetic flux lines and wound-strings in extra dimensions
Lake, Matthew
2012-01-01
We consider a generalization of the Nielsen-Olesen ansatz, in the abelian-Higgs model, which describes strings with twisted magnetic flux lines in the vortex core. The solution does not possess cylindrical symmetry, which leads to the existence of components of conserved momentum, both around the core-axis and along the length of the string. In addition, we consider a model of F-strings with rotating, geodesic windings in the compact space of the Klebanov-Strassler geometry and determine matching conditions which ensure energy and momentum conservation when loops chop off from the long-string network. We find that the expressions for the constants of motion, which determine the macroscopic string dynamics, can be made to coincide with those for the twisted flux line string, suggesting that extra- dimensional effects for F-strings may be mimicked by field-theoretic structure in topological defects.
A Construction of String 2-Group Models using a Transgression-Regression Technique
Waldorf, Konrad
2012-01-01
In this note we present a new construction of the string group that ends optionally in two different contexts: strict diffeological 2-groups or finite-dimensional Lie 2-groups. It is canonical in the sense that no choices are involved; all the data is written down and can be looked up (at least somewhere). The basis of our construction is the basic gerbe of Gawedzki-Reis and Meinrenken. The main new insight is that under a transgression-regression procedure, the basic gerbe picks up a multiplicative structure coming from the Mickelsson product over the loop group. The conclusion of the construction is a relation between multiplicative gerbes and 2-group extensions for which we use recent work of Schommer-Pries.
Effect of excitation methods on electrical characteristics of fully superconducting generator model
Muta, Itsuya; Tsukiji, H.; Handa, N.; Hoshino, Tsutomu; Mukai, E.
1994-07-01
We have fabricated a fully superconducting generator of 20 kW class, in which both of armature and field coils are made of superconductors. Two different types of excitation system were selected and tested: a brushless excitation method consisted of 'magnetic flux pump' and a conventional excitation method equipped with collector ring and brushes. The paper describes the experimental machine model and the comparison of test results between the two different types of excitation methods.
Finite Element Model of Training in the superconducting quadrupole magnet SQ02
Energy Technology Data Exchange (ETDEWEB)
Caspi, Shlomo; Ferracin, Paolo
2007-11-01
This paper describes the use of 3D finite element models to study training in superconducting magnets. The simulations are used to examine coil displacements when the electromagnetic forces are cycled, and compute the frictional energy released during conductor motion with the resulting temperature rise. A computed training curve is then presented and discussed. The results from the numerical computations are compared with test results of the Nb{sub 3}Sn racetrack quadrupole magnet SQ02.
Field Quality of the Short Superconducting Dipole Models for the LHC
Ang, Z; Sanfilippo, S; Siemko, A; Tommasini, D; Venturini-Delsolaro, W; Walckiers, L
2002-01-01
A full characterization of the magnetic field in warm and cold conditions was performed as a part of the standard test on the LHC 1-m long superconducting dipole models. Furthermore, dedicated measurement campaigns addressed the effect of current cycles and quenches on field quality. Powering and quenches were found to generate characteristic instabilities in the geometric harmonics. Detailed results are presented on this phenomenon, as well as correlations between warm and cold measurements and field reconstructions.
Field quality of the short superconducting dipole models for the LHC
Venturini-Delsolaro, W; Bottura, L; Sanfilippo, S; Siemko, A; Tommasini, D; Walckiers, L
2002-01-01
A full characterization of the magnetic field in warm and cold conditions was performed as a part of the standard test on the LHC 1- m long superconducting dipole models. Furthermore, dedicated measurement campaigns addressed the effect of current cycles and quenches on field quality. Powering and quenches were found to generate characteristic instabilities in the geometric harmonics. Detailed results are presented on this phenomenon, as well as correlations between warm and cold measurements and field reconstructions. (9 refs).
Kim, Joonho; Lee, Kimyeong
2015-01-01
We explore 6d (1,0) superconformal field theories with SU(3) and SU(2) gauge symmetries which cascade after Higgsing to the E-string theory on a single M5 near an $E_8$ wall. Specifically, we study the 2d $\\mathcal{N}=(0,4)$ gauge theories which describe self-dual strings of these 6d theories. The self-dual strings can be also viewed as instanton string solitons of 6d Yang-Mills theories. We find the 2d anomaly-free gauge theories for self-dual strings, amending the naive ADHM gauge theories which are anomalous, and calculate their elliptic genera. While these 2d theories respect the flavor symmetry of each 6d SCFT only partially, their elliptic genera manifest the symmetry fully as these functions as BPS index are invariant in strongly coupled IR limit. Our consistent 2d (0,4) gauge theories also provide new insights on the non-linear sigma models for the instanton strings, providing novel UV completions of the small instanton singularities. Finally, we construct new 2d quiver gauge theories for the self-dua...
Cosmic Strings Stabilized by Quantum Fluctuations
Weigel, H.
2017-03-01
Fermion quantum corrections to the energy of cosmic strings are computed. A number of rather technical tools are needed to formulate this correction, and isospin and gauge invariance are employed to verify consistency of these tools. These corrections must also be included when computing the energy of strings that are charged by populating fermion bound states in its background. It is found that charged strings are dynamically stabilized in theories similar to the standard model of particle physics.
Cosmic Strings Stabilized by Quantum Fluctuations
Weigel, H
2016-01-01
We compute fermion quantum corrections to the energy of cosmic strings. A number of rather technical tools is needed to formulate this correction and we employ isospin and gauge invariance to verify consistency of these tools. These corrections must also be included when computing the energy of strings that are charged by populating fermion bound states in its background. We find that charged strings are dynamically stabilized in theories similar to the standard model of particle physics.
Exotic Non-relativistic String
Casalbuoni, Roberto; Longhi, Giorgio
2007-01-01
We construct a classical non-relativistic string model in 3+1 dimensions. The model contains a spurion tensor field that is responsible for the non-commutative structure of the model. Under double dimensional reduction the model reduces to the exotic non-relativistic particle in 2+1 dimensions.
On Exceptional Instanton Strings
Del Zotto, Michele
2016-01-01
According to a recent classification of 6d (1,0) theories within F-theory there are only 5 "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 $\\mathcal{N}=(0,4)$ 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 $\\mathcal{N}=2$ 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 $T^2 \\times S^2$ partition functions and the Hilbert series for moduli spaces of $G$ instantons. Such relations allow to bootstrap the corresponding e...
2009-03-06
needed. 5A Unicode code-point is different from a grapheme , which is closer to what end-users consider as characters. For example a character with a...dieresis (e.g., ä) is a grapheme , but could be encoded as two Unicode code points. 9 String constraint Abstract String Syntax STRCMP(s1,s2) = 0
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.
Analytical Model of Thermo-electrical Behaviour in Superconducting Resistive Core Cables
Calvi, M; Breschi, M; Coccoli, M; Granieri, P; Iriart, G; Lecci, F; Siemko, A
2006-01-01
High field superconducting Nb3Sn accelerators magnets above 14 T, for future High Energy Physics applications, call for improvements in the design of the protection system against resistive transitions. The longitudinal quench propagation velocity (vq) is one of the parameters defining the requirements of the protection. Up to now vq has been always considered as a physical parameter defined by the operating conditions (the bath temperature, cooling conditions, the magnetic field and the over all current density) and the type of superconductor and stabilizer used. It is possible to enhance the quench propagation velocity by segregating a percent of the stabilizer into the core, although keeping the total amount constant and tuning the contact resistance between the superconducting strands and the core. Analytical model and computer simulations are presented to explain the phenomenon. The consequences with respect to minimum quench energy are evidenced and the strategy to optimize the cable designed is discuss...
Realization and Modeling of Metamaterials Made of rf Superconducting Quantum-Interference Devices
Directory of Open Access Journals (Sweden)
M. Trepanier
2013-12-01
Full Text Available We have prepared meta-atoms based on radio-frequency superconducting quantum-interference devices (rf SQUIDs and examined their tunability with dc magnetic field, rf current, and temperature. rf SQUIDs are superconducting split-ring resonators in which the usual capacitance is supplemented with a Josephson junction, which introduces strong nonlinearity in the rf properties. We find excellent agreement between the data and a model that regards the Josephson junction as the resistively and capacitively shunted junction. A magnetic field tunability of 80 THz/G at 12 GHz is observed, a total tunability of 56% is achieved, and a unique electromagnetically induced transparency feature at intermediate excitation powers is demonstrated for the first time. An rf SQUID metamaterial is shown to have qualitatively the same behavior as a single rf SQUID with regard to dc flux and temperature tuning.
Superconducting correlations and thermodynamic properties in 2D square and triangular t-J model
Ogata, Masao
2006-03-01
Equal-time superconducting correlation functions of the two-dimensional t-J model on the square lattice are studied using high-temperature expansion method.[1] The sum of the pairing correlation, its spatial dependence and correlation length are obtained down to T ˜0.2t. By comparison of single-particle contributions in the correlation functions, we find effective attractive interactions between quasi-particles in dx^2-y^2-wave channel. It is shown that d-wave correlation grows rapidly at low temperatures for the doping 0.1 0 with hole doping, a rapid growth of effective d-wave paring interaction is found that indicates the resonating-valence-bond superconductivity. In contrast, when tJ. Phys. Soc. Japan 74, 1390 (2005). [2] T. Koretsune and M. Ogata, Phys. Rev. Lett. 89, 116401 (2002), and Phys. Rev. B72, 134513 (2005).
A Superconducting Levitation Transport Model System for Dynamical and Didactical Studies
Rosenzweig, St.; Reich, E.; Neu, V.; Berger, D.; Peukert, K.; Holzapfel, B.; Schultz, L.; Pospiech, G.
Superconducting levitation transport systems might become very attractive in the near future due to various reasons. The realisation of contactless systems allows e.g. extended maintenance-free operation with high efficiency since such a system only needs energy for cooling and propulsion. We established a small superconducting levitation transport model system called "SupraTrans Min" consisting of permanent magnetic rails and a levitated vehicle including four YBCO-bulk samples in a cryostat. The rail system consists of an oval shaped loop (2.90 m x 1.44 m), which was build up from individual linear and curved track modules. Inside the vehicle position variations of the superconductors are possible. By means of velocity, acceleration and temperature measurements different dynamical aspects of our complex levitation system can be investigated. We also show the broad applicability of the experimental setup for didactical studies in physics.
Digital-analog quantum simulation of generalized Dicke models with superconducting circuits
Lamata, Lucas
2017-01-01
We propose a digital-analog quantum simulation of generalized Dicke models with superconducting circuits, including Fermi- Bose condensates, biased and pulsed Dicke models, for all regimes of light-matter coupling. We encode these classes of problems in a set of superconducting qubits coupled with a bosonic mode implemented by a transmission line resonator. Via digital-analog techniques, an efficient quantum simulation can be performed in state-of-the-art circuit quantum electrodynamics platforms, by suitable decomposition into analog qubit-bosonic blocks and collective single-qubit pulses through digital steps. Moreover, just a single global analog block would be needed during the whole protocol in most of the cases, superimposed with fast periodic pulses to rotate and detune the qubits. Therefore, a large number of digital steps may be attained with this approach, providing a reduced digital error. Additionally, the number of gates per digital step does not grow with the number of qubits, rendering the simulation efficient. This strategy paves the way for the scalable digital-analog quantum simulation of many-body dynamics involving bosonic modes and spin degrees of freedom with superconducting circuits. PMID:28256559
Effect of superconducting solenoid model cores on spanwise iron magnet roll control
Britcher, C. P.
1985-01-01
Compared with conventional ferromagnetic fuselage cores, superconducting solenoid cores appear to offer significant reductions in the projected cost of a large wind tunnel magnetic suspension and balance system. The provision of sufficient magnetic roll torque capability has been a long-standing problem with all magnetic suspension and balance systems; and the spanwise iron magnet scheme appears to be the most powerful system available. This scheme utilizes iron cores which are installed in the wings of the model. It was anticipated that the magnetization of these cores, and hence the roll torque generated, would be affected by the powerful external magnetic field of the superconducting solenoid. A preliminary study has been made of the effect of the superconducting solenoid fuselage model core concept on the spanwise iron magnet roll torque generation schemes. Computed data for one representative configuration indicate that reductions in available roll torque occur over a range of applied magnetic field levels. These results indicate that a 30-percent increase in roll electromagnet capacity over that previously determined will be required for a representative 8-foot wind tunnel magnetic suspension and balance system design.
Digital-analog quantum simulation of generalized Dicke models with superconducting circuits
Lamata, Lucas
2017-03-01
We propose a digital-analog quantum simulation of generalized Dicke models with superconducting circuits, including Fermi- Bose condensates, biased and pulsed Dicke models, for all regimes of light-matter coupling. We encode these classes of problems in a set of superconducting qubits coupled with a bosonic mode implemented by a transmission line resonator. Via digital-analog techniques, an efficient quantum simulation can be performed in state-of-the-art circuit quantum electrodynamics platforms, by suitable decomposition into analog qubit-bosonic blocks and collective single-qubit pulses through digital steps. Moreover, just a single global analog block would be needed during the whole protocol in most of the cases, superimposed with fast periodic pulses to rotate and detune the qubits. Therefore, a large number of digital steps may be attained with this approach, providing a reduced digital error. Additionally, the number of gates per digital step does not grow with the number of qubits, rendering the simulation efficient. This strategy paves the way for the scalable digital-analog quantum simulation of many-body dynamics involving bosonic modes and spin degrees of freedom with superconducting circuits.
Dando, O; Dando, Owen; Gregory, Ruth
1998-01-01
We examine the field equations of a self-gravitating global string in low energy superstring gravity, allowing for an arbitrary coupling of the global string to the dilaton. Massive and massless dilatons are considered. For the massive dilaton the spacetime is similar to the recently discovered non-singular time-dependent Einstein self-gravitating global string, but the massless dilaton generically gives a singular spacetime, even allowing for time-dependence. We also demonstrate a time-dependent non-singular string/anti-string configuration, in which the string pair causes a compactification of two of the spatial dimensions, albeit on a very large scale.
Closed String Amplitudes from Gauge Fixed String Field Theory
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.
Closed String Amplitudes from Gauge Fixed String Field Theory
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.
On the Properties of Cosmic String Loops
Casper, Paul Henry
1996-01-01
When coupled with the prevailing ideas of cosmology, the standard model of particle physics implies that the early universe underwent a sequence of phase transitions. Such phase transitions can lead to topological defects such as magnetic monopoles, domain walls and cosmic strings. The formation and subsequent evolution of a network of cosmic strings may have played a key role in the development of the early universe. One of the most crucial elements in the evolution of the cosmic string network is the formation and decay of closed loops of cosmic string. After formation, the loops lose their energy by emitting gravitational radiation. This provides the primary energy loss mechanism for the cosmic string network. In addition, the cosmic string loops may display a number of observable features through which the cosmic string model may be constrained. In this dissertation a number of the key properties of cosmic string loops are investigated. A general method for determining the rates at which cosmic string loops radiate both energy and linear momentum is developed and implemented. Exact solutions for the radiation rates of a several new classes of loops are derived and used to test the validity of using the piecewise linear method on smooth loop trajectories. A large set of representative loop trajectories is produced using the method of loop fragmentation. These trajectories are analyzed to provide useful information on the properties of realistic cosmic string loops. The fraction of cosmic string loops which would collapse to form black holes is determined and used to place a new observational limit on the mass per unit length of cosmic strings.
String Phenomenology: Past, Present and Future Perspectives
Faraggi, Alon E
2014-01-01
The observation of a scalar resonance at the LHC, compatible with perturbative electroweak symmetry breaking, reinforces the Standard Model 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 enta...
Clément, G
1995-01-01
We construct regular multi-wormhole solutions to a gravitating \\sigma model in three space-time dimensions, and extend these solutions to cylindrical traversable wormholes in four and five dimensions. We then discuss the possibility of identifying wormhole mouths in pairs to give rise to Wheeler wormholes. Such an identification is consistent with the original field equations only in the absence of the \\sigma-model source, but with possible naked cosmic string sources. The resulting Wheeler wormhole space-times are flat outside the sources and may be asymptotically Minkowskian.
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...... of the standard model of elementary particle physics. For the electromagnetic sector it is found that already a small disorder pushes the associated energy scale of the running coupling constant far away from the result without disorder....
Hot QCD, k-strings and the adjoint monopole gas model
Altes, C P K; Altes, Chris P. Korthals; Meyer, Harvey B.
2005-01-01
When the magnetic sector of hot QCD, 3D SU(N) Yang-Mills theory, is described as a dilute gas of non-Abelian monopoles in the adjoint representation of the magnetic group, Wilson loops of N-ality k are known to obey a periodic k(N-k) law. Lattice simulations have confirmed this prediction to a few percent for N=4 and 6. We describe in detail how the magnetic flux of the monopoles produces different area laws for spatial Wilson k-loops. A simple physical argument is presented, why the predicted and observed Casimir scaling is allowed in the large-N limit by usual power-counting arguments. The same scaling is also known to hold in two-loop perturbation theory for the spatial 't Hooft loop, which measures the electric flux. We then present new lattice data for 3D N=8 k-strings as long as 3`fm' that provide further confirmation. Finally we suggest new tests in theories with spontaneous breaking and in SO(4n+2) gauge groups.
A String-Inspired Model for the Low-$\\ell$ CMB
Kitazawa, N
2015-01-01
We present a semi--analytic exploration of some low--$\\ell$ angular power spectra inspired by "Brane Supersymmetry Breaking". This mechanism splits Bose and Fermi excitations in String Theory, leaving behind an exponential potential that is just too steep for the inflaton to emerge from the initial singularity while descending it. As a result, the scalar generically bounces against the exponential wall, which typically introduces an infrared depression and a pre--inflationary peak in the power spectrum of scalar perturbations. We elaborate on a possible link between this phenomenon and the low--$\\ell$ CMB. For the first 32 multipoles, combining the hard exponential with a milder one leading to $n_s\\simeq 0.96$ and with a small gaussian bump we have attained a reduction of $\\chi^{\\,2}$ to about 46% of the standard $\\Lambda$CDM setting, with both WMAP9 and PLANCK 2013 data. This result corresponds to a $\\chi^{\\,2}/DOF$ of about 0.45, to be compared with a $\\Lambda$CDM value of about 0.85. The preferred choices ...
Zhang, Huiming; Zhang, Min; Yuan, Weijia
2017-02-01
An efficient three dimensional (3D) finite element method numerical model is proposed for superconducting coated conductors. The model is based on the T-A formulation and can be used to tackle 3D computational challenges for superconductors with high aspect ratios. By assuming a sheet approximation for the conductors, the model can speed up the computational process. The model has been validated by established analytical solutions. Two examples with complex geometries, which can hardly be simulated by the 2D model, are given. The model could be used to characterise and design large-scale applications using superconducting coated conductors, such as high field magnets and other electrical devices.
Energy Technology Data Exchange (ETDEWEB)
Ige, O.O.; Lyon, R.H.; Iwasa, Y. (Francis Bitter National Magnet Laboratory Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States))
1992-03-15
The longitudinal attenuation of impact-generated pulses in ten superconducting dipole magnets was measured at room temperature. A lumped-parameter model was constructed for the collared dipole. Using the method of nonlinear least-squares, the model was used to estimate the internal damping in the main components of the dipoles and the coupling resistances between the components: collars, inner, and outer coils. A positive correlation was found between the collar-inner coil coupling resistance and the 4.2-K performance of the magnets: the higher the coupling resistance, the fewer the number of quenches required to reach design operating current. There was virtually no correlation between any of the other internal or coupling resistances and 4.2-K performance. These observations are explained in terms of frictional slip of the inner coil against the collars causing premature quenches. The magnets are more susceptible to quenches at the collar-inner coil interface than at the collar-outer coil interface because the inner coil is subject to higher fields and forces. The experiment is potentially useful as a technique for screening high-performance superconducting magnets such as Superconducting Super Collider (SSC) dipoles at room temperature.
Applying experimental constraints to a one-dimensional model for BiS2 superconductivity
Griffith, M. A.; Foyevtsova, K.; Continentino, M. A.; Martins, G. B.
2016-10-01
Recent ARPES measurements [Sugimoto et al., Phys. Rev. B 92 (2015) 041113] have confirmed the one-dimensional character of the electronic structure of CeO0.5 F0.5 BiS2, a representative of BiS2-based superconductors. In addition, several members of this family present sizable increase in the superconducting transition temperature Tc under application of hydrostatic pressure. Motivated by these two results, we propose an effective one-dimensional three-orbital model, whose kinetic energy part, obtained through ab initio calculations, is supplemented by pair-scattering terms, which are treated at the mean-field level. We solve the gap equations self-consistently and then systematically probe which combination of pair-scattering terms gives results consistent with experiment, namely, a superconducting dome with a maximum Tc at the right chemical potential and a sizable increase in Tc when the magnitude of the hoppings is increased. For these constraints to be satisfied multi-gap superconductivity is required, in agreement with experiments, and one of the hoppings has a dominant influence over the increase of Tc with pressure.
Newhouse, Vernon L
1975-01-01
Applied Superconductivity, Volume II, is part of a two-volume series on applied superconductivity. The first volume dealt with electronic applications and radiation detection, and contains a chapter on liquid helium refrigeration. The present volume discusses magnets, electromechanical applications, accelerators, and microwave and rf devices. The book opens with a chapter on high-field superconducting magnets, covering applications and magnet design. Subsequent chapters discuss superconductive machinery such as superconductive bearings and motors; rf superconducting devices; and future prospec
String fragmentation; La fragmentation des cordes
Energy Technology Data Exchange (ETDEWEB)
Drescher, H.J.; Werner, K. [Laboratoire de Physique Subatomique et des Technologies Associees - SUBATECH, Centre National de la Recherche Scientifique, 44 - Nantes (France)
1997-10-01
The classical string model is used in VENUS as a fragmentation model. For the soft domain simple 2-parton strings were sufficient, whereas for higher energies up to LHC, the perturbative regime of the QCD gives additional soft gluons, which are mapped on the string as so called kinks, energy singularities between the leading partons. The kinky string model is chosen to handle fragmentation of these strings by application of the Lorentz invariant area law. The `kinky strings` model, corresponding to the perturbative gluons coming from pQCD, takes into consideration this effect by treating the partons and gluons on the same footing. The decay law is always the Artru-Menessier area law which is the most realistic since it is invariant to the Lorentz and gauge transformations. For low mass strings a manipulation of the rupture point is necessary if the string corresponds already to an elementary particle determined by the mass and the flavor content. By means of the fragmentation model it will be possible to simulate the data from future experiments at LHC and RHIC 3 refs.
Superconducting phases of strange quark matter in the NJL model
Paulucci, L; Ferrer, E J; de la Incera, V
2013-01-01
We analyze the color-flavor-locked phase of strange quark matter modelled by the three-flavor Nambu-Jona-Lasinio (NJL) framework with and without magnetic field and discuss some additional constraints on the stability scenario when a high magnetic field is applied. We compare the results obtained by employing the MIT Bag Model and discuss the pairing gap behavior and its influence on the equation of state.
On Approximating String Selection Problems with Outliers
Boucher, Christina; Levy, Avivit; Pritchard, David; Weimann, Oren
2012-01-01
Many problems in bioinformatics are about finding strings that approximately represent a collection of given strings. We look at more general problems where some input strings can be classified as outliers. The Close to Most Strings problem is, given a set S of same-length strings, and a parameter d, find a string x that maximizes the number of "non-outliers" within Hamming distance d of x. We prove this problem has no PTAS unless ZPP=NP, correcting a decade-old mistake. The Most Strings with Few Bad Columns problem is to find a maximum-size subset of input strings so that the number of non-identical positions is at most k; we show it has no PTAS unless P=NP. We also observe Closest to k Strings has no EPTAS unless W[1]=FPT. In sum, outliers help model problems associated with using biological data, but we show the problem of finding an approximate solution is computationally difficult.
Cai, Ang; Pixley, Jedediah; Si, Qimiao
Heavy fermion metals represent a canonical system to study superconductivity driven by quantum criticality. We are particularly motivated by the properties of CeRhIn5, which shows the characteristic features of a Kondo destruction quantum critical point (QCP) in its normal state, and has one of the highest Tc's among the heavy fermion superconductors. As a first step to study this problem within a cluster-EDMFT approach, we analyze a four-site Anderson impurity model with the antiferromagnetic spin component of the cluster coupled to a sub-Ohmic bosonic bath. We find a QCP that belongs to the same universality class as the single-site Bose-Fermi Anderson model. Together with previous work on a two-site model, our result suggests that the Kondo destruction QCP is robust as cluster size increases. More importantly, we are able to calculate the d-wave pairing susceptibility, which we find to be enhanced near the QCP. Using this model as the effective cluster model of the periodic Anderson model, we are also able to study the superconducting pairing near the Kondo-destruction QCP of the lattice model; preliminary results will be presented.
Majorana zero modes in the hopping-modulated one-dimensional p-wave superconducting model.
Gao, Yi; Zhou, Tao; Huang, Huaixiang; Huang, Ran
2015-11-20
We investigate the one-dimensional p-wave superconducting model with periodically modulated hopping and show that under time-reversal symmetry, the number of the Majorana zero modes (MZMs) strongly depends on the modulation period. If the modulation period is odd, there can be at most one MZM. However if the period is even, the number of the MZMs can be zero, one and two. In addition, the MZMs will disappear as the chemical potential varies. We derive the condition for the existence of the MZMs and show that the topological properties in this model are dramatically different from the one with periodically modulated potential.
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
Conlon, Joseph
2016-01-01
Is string theory a fraud or one of the great scientific advances? Why do so many physicists work on string theory if it cannot be tested? This book provides insight into why such a theory, with little direct experimental support, plays such a prominent role in theoretical physics. The book gives a modern and accurate account of string theory and science, explaining what string theory is, why it is regarded as so promising, and why it is hard to test.
Ooguri, H; Ooguri, Hirosi; Yin, Zheng
1996-01-01
These lecture notes are based on a course on string theories given by Hirosi Ooguri in the first week of TASI 96 Summer School at Boulder, Colorado. It is an introductory course designed to provide students with minimum knowledge before they attend more advanced courses on non-perturbative aspects of string theories in the School. The course consists of five lectures: 1. Bosonic String, 2. Toroidal Compactifications, 3. Superstrings, 4. Heterotic Strings, and 5. Orbifold Compactifications.
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...
A PROBABILISTIC APPROACH TO STRING TRANSFORMATION
Directory of Open Access Journals (Sweden)
V. Vinothh
2015-10-01
Full Text Available The string model has been applied to a wide range of problems, including spelling correction. These models consist of two components: a source model and a channel model. Very little research has gone into improving the channel model for spelling correction. We Describes a new channel model for spelling correction, based on generic string to string edits. Using this model gives significant performance improvements compared to previously proposed models. We propose a novel and probabilistic approach to string transformation, which is both accurate and efficient. In this approach includes the use of a log linear model, a method for training the model, and an algorithm for generating the top k candidates, whether there is or is not a predefined dictionary. Log linear model is defined as a conditional probability distribution of an output string and a rule set for the transformation conditioned on an input string. The string generation algorithm based on pruning is guaranteed to generate the optimal top k candidates. The proposed method is applied to correction of spelling errors in queries as well as reformulation of queries in web search. Experimental results on large scale data show that the proposed approach is very accurate and efficient improving upon existing methods in terms of accuracy and efficiency in different settings.
The social structure of experimental'' strings at Fermilab; a physics and detector driven model
Energy Technology Data Exchange (ETDEWEB)
Bodnarczuk, M.
1990-12-12
Physicists in HEP have been forced to organize large scientific projects without a well defined organizational or sociological model to guide them. In the absence of such models, what structures do experimentalists use to develop social structures in HEP In this paper, I claim that physicists organize around what they know best, the physics problems they study and the detectors and devices they study them with. After describing the advent of management'' in HEP, I use a case study of 4 Fermilab experiments as the base upon which to propose a physics and detector driven model of social structure for experiments. In addition, I show how this model can be extended to describe strings'' of experiments, where continuities of physics interests, spectrometer design, and a core group of physicists become a definable sociological unit that can exist for over 15 years. A dominate theme that emerges from my analysis is the conscious attempt on the part of experimenters to remove the uncertainties that are part of the practice of HEP.
[The string of Einthoven's string galvanometer].
Wyers, P J
1996-01-01
The Dutch physiologist Willem Einthoven (1860-1927) published in 1901 his construction of a string galvanometer. With this apparatus he opened the era for electrocardiography. As the quality of his instrument largely depended on the string of the string galvanometer it is surprising to note that in his publications Einthoven never mentioned the exact way of producing the string. However, Einthoven's hand written laboratory notes are preserved at the Museum Boerhaave in Leiden. From these notes it comes clear what problems Einthoven had with the string. To get a very thin thread of quarts he first used the method of shooting the thread as was described by Boys (1887), later the blowing method of Nichols (1894). The silvering of the thread was done first chemically, later by cathode spray. In all cases premature breaking of the thread was a nuisance. Because of these failures Einthoven might have decided not to publish any details.
Fields, Strings, Matrices and Symmetric Products
Dijkgraaf, R.
1999-01-01
In these notes we review the role played by the quantum mechanics and sigma models of symmetric product spaces in the light-cone quantization of quantum field theories, string theory and matrix theory. Lectures given at the Institute for Theoretical Physics, UC Santa Barbara, January 1998 and the Spring School on String Theory and Mathematics, Harvard University, May 1998.
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...
The series of String-Math conferences has developed into a central event on the interface between mathematics and physics related to string theory, quantum field theory and neighboring subjects. The conference will take place from July 24-28 in the main building of Hamburg university. The String-Math conference is organised by the University of Hamburg jointly with DESY Hamburg.
Cardona, Biel; Pons, Josep M
2016-01-01
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.
Energy Technology Data Exchange (ETDEWEB)
Cordero, Ruben; Granados, Victor D [Departamento de Fisica, Escuela Superior de Fisica y Matematicas del IPN, Unidad Profesional Adolfo Lopez Mateos, Edificio 9, 07738 Mexico DF (Mexico); Mota, Roberto D, E-mail: cordero@esfm.ipn.mx, E-mail: granados@esfm.ipn.mx, E-mail: rmotae@ipn.mx [Departamento de ICE de la Escuela Superior de IngenierIa Mecanica y Electrica del IPN, Unidad Culhuacan. Av. Santa Ana No 1000, San Francisco Culhuacan, Coyoacan Mexico DF, CP 04430 (Mexico)
2011-09-21
We find the full symmetries of the Wheeler-DeWitt equation for the Hawking and Page wormhole model and an axion-dilaton string cosmology. We show that the Wheeler-DeWitt Hamiltonian admits a U(1, 1) hidden symmetry for the Hawking and Page model and U(2, 1) for the axion-dilaton string cosmology. If we consider the existence of matter-energy renormalization, for each of these models we find that the Wheeler-DeWitt Hamiltonian accepts an additional SL(2, R) dynamical symmetry. In this case, we show that the SL(2, R) dynamical symmetry generators transform the states from one energy Hilbert eigensubspace to another. Some new wormhole-type solutions for both models are found.
Paraquantum strings in noncommutative space-time
Seridi, M. A.; Belaloui, N.
2015-10-01
A parabosonic string is assumed to propagate in a total noncommutative target phase space. Three models are investigated: open strings, open strings between two parallel Dp-Dq branes and closed ones. This leads to a generalization of the oscillators algebra of the string and the corresponding Virasoro algebra. The mass operator is no more diagonal in the ordinary Fock space, a redefinition of this later will modify the mass spectrum, so that, neither massless vector state nor massless tensor state are present. The restoration of the photon and the graviton imposes specific forms of the noncommutativity parameter matrices, partially removes the mass degeneracy and gives new additional ones. In particular, for the D-branes, one can have a tachyon free model with a photon state when more strict conditions on these parameters are imposed, while, the match level condition of the closed string model induces the reduction of the spectrum.
Topological strings and quantum curves
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 dualitie
Pokorski, Witold; Pokorski, Witold; Ross, Graham G.
1998-01-01
We consider the phenomenological implications of a class of compactified string theories which naturally reproduces the flavour multiplet structure of the Standard Model. The implications for gauge unification depends on which of three possibilities is realised for obtaining light Higgs multiplets. The more conventional one leads to predictions for the gauge couplings close to that of the MSSM but with an increased value of the unification scale. The other two cases offer a mechanism for bringing the prediction for the strong coupling into agreement with the measured value while still increasing the unification scale. The various possibilities lead to different expectations for the structure of the quark masses.
s- and d-wave superconductivity in a two-band model
Reyes, Daniel; Continentino, Mucio A.; Thomas, Christopher; Lacroix, Claudine
2016-10-01
Superconductivity in strongly correlated systems is a remarkable phenomenon that attracts a huge interest. The study of this problem is relevant for materials such as the high Tc oxides, pnictides and heavy fermions. In this work we study a realistic model that includes the relevant physics of superconductivity in the presence of strong Coulomb correlations. We consider a two-band model, since most of these correlated systems have electrons from at least two different atomic orbitals coexisting at their Fermi surface. The Coulomb repulsion is taken into account through a local repulsive interaction. Pairing is considered among quasi-particles in neighboring sites and we allow for different symmetries of the order parameter. In order to deal with the strong local correlations, we use the well known slave boson approach that has proved very successful for this problem. Here we are interested in obtaining the zero temperature properties of the model, specifically its phase diagram and the existence and nature of superconducting quantum critical points. We show that these can arise by increasing the mixing between the two bands. Since this can be controlled by external pressure or doping, our results have a direct relation with experiments. We show that the superconductor-to-normal transition can be either to a metal, a correlated metal or to an insulator. Also we compare the relative stability of s and d-wave paired states for different regions of parameter space and investigate the BCS-BEC crossover in the two-band lattice model as function of the strength of the pairing interaction.
Hunting for TeV Scale Strings at the LHC
Bars, Itzhak
2010-01-01
In this paper I review the possibility of TeV scale strings that may be detectable by the Large Hadron Collider (LHC). This possibility was investigated extensively in a series of phenomenological papers during 1984-1985 in connection with the Superconducting Super Collider (SSC). The work was mainly based on a model independent systematic parametrization of scattering amplitudes and cross sections, for Standard Model particles, quarks and leptons, that were assumed to behave like strings, while gluons, photons, $W^{\\pm},Z$ were taken as elementary. By using Veneziano type beta functions consistent with crossing symmetry, duality and Regge behavior, bosonic or fermionic resonances in each channel were included, while the low energy behavior was matched to effective field theory non-renormalizable interactions consistent with the Standard Model SU(3)xSU(2)xU(1) gauge symmetry as well as global flavor and family symmetries. The motivation for this approach at that time was the possible compositeness of quarks a...
Topological Strings and Integrable Hierarchies
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.
Topological Strings and Integrable Hierarchies
Aganagic, Mina; Dijkgraaf, Robbert; Klemm, Albrecht; Mariño, 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 -algebra symmetries which encode 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 an A-model topological string on P1 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.
Modeling dynamic behavior of superconducting maglev systems under external disturbances
Huang, Chen-Guang; Xue, Cun; Yong, Hua-Dong; Zhou, You-He
2017-08-01
For a maglev system, vertical and lateral displacements of the levitation body may simultaneously occur under external disturbances, which often results in changes in the levitation and guidance forces and even causes some serious malfunctions. To fully understand the effect of external disturbances on the levitation performance, in this work, we build a two-dimensional numerical model on the basis of Newton's second law of motion and a mathematical formulation derived from magnetoquasistatic Maxwell's equations together with a nonlinear constitutive relation between the electric field and the current density. By using this model, we present an analysis of dynamic behavior for two typical maglev systems consisting of an infinitely long superconductor and a guideway of different arrangements of infinitely long parallel permanent magnets. The results show that during the vertical movement, the levitation force is closely associated with the flux motion and the moving velocity of the superconductor. After being disturbed at the working position, the superconductor has a disturbance-induced initial velocity and then starts to periodically vibrate in both lateral and vertical directions. Meanwhile, the lateral and vertical vibration centers gradually drift along their vibration directions. The larger the initial velocity, the faster their vibration centers drift. However, the vertical drift of the vertical vibration center seems to be independent of the direction of the initial velocity. In addition, due to the lateral and vertical drifts, the equilibrium position of the superconductor in the maglev systems is not a space point but a continuous range.
String Resonances at Hadron Colliders
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...
From decay to complete breaking: pulling the strings in SU(2) Yang-Mills theory.
Pepe, M; Wiese, U-J
2009-05-15
We study {2Q+1} strings connecting two static charges Q in (2+1)D SU(2) Yang-Mills theory. While the fundamental {2} string between two charges Q=1/2 is unbreakable, the adjoint {3} string connecting two charges Q=1 can break. When a {4} string is stretched beyond a critical length, it decays into a {2} string by gluon pair creation. When a {5} string is stretched, it first decays into a {3} string, which eventually breaks completely. The energy of the screened charges at the ends of a string is well described by a phenomenological constituent gluon model.
Dando, Owen; Gregory, Ruth
1998-07-01
We examine the field equations of a self-gravitating global string in low energy superstring gravity, allowing for an arbitrary coupling of the global string to the dilaton. Massive and massless dilatons are considered. For the massive dilaton the spacetime is similar to the recently discovered non-singular time-dependent Einstein self-gravitating global string, but the massless dilaton generically gives a singular spacetime, even allowing for time dependence. We also demonstrate a time-dependent non-singular string-antistring configuration, in which the string pair causes a compactification of two of the spatial dimensions, albeit on a very large scale.
Rabi model as a quantum coherent heat engine: From quantum biology to superconducting circuits
2014-01-01
PHYSICAL REVIEW A 91, 023816 (2015) Rabi model as a quantum coherent heat engine: From quantum biology to superconducting circuits Ferdi Altintas,1 Ali U¨ . C. Hardal,2 and O¨ zgu¨r E. Mu¨stecaplıog˘lu2,* 1Department of Physics, Abant Izzet Baysal University, Bolu, 14280, Turkey 2Department of Physics, Koc¸ University, Sarıyer, ˙Istanbul, 34450, Turkey (Received 10 November 2014; published 12 February 2015) We propose a multilevel quantum heat engine with a working medium de...
Elastic Constants of Superconducting MgB2 from Molecular Dynamics Simulations with Shell Model
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
The elastic constants of superconducting MgB2 are calculated using a molecular dynamics method (MD)with shell model. The lattice parameters, five independent elastic constants, equations of state (EOS), Debye temperature, and bulk modulus of MgB2 are obtained. Meanwhile, the dependence of the bulk modulus B, the lattice parameters a and c, and the unit cell volume V on the applied pressure are presented. It is demonstrated that the method introduced here can well reproduce the experimental results with a reasonable accuracy.
Institute of Scientific and Technical Information of China (English)
Wang Li-Na; Zhao Xing-Yu; Zhang Li-Li; Huang Yi-Neng
2012-01-01
The relaxation dynamics of liquids is one of the fundamental problems in liquid physics,and it is also one of the key issues to understand the glass transition mechanism.It will undoubtedly provide enlightenment on understanding and calculating the relaxation dynamics if the molecular orientation flipping images and relevant microparameters of liquids are studied.In this paper,we first give five microparameters to describe the individual molecular string (MS) relaxation based on the dynamical Hamiltonian of the MS model,and then simulate the images of individual MS ensemble,and at the same time calculate the parameters of the equilibrium state.The results show that the main molecular orientation flipping image in liquids (including supercooled liquid) is similar to the random walk.In addition,two pairs of the parameters are equal,and one can be ignored compared with the other.This conclusion will effectively reduce the difficulties in calculating the individual MS relaxation based on the single-molecule orientation flipping rate of the general Glauber type,and the computer simulation time of interaction MS relaxation.Moreover,the conclusion is of reference significance for solving and simulating the multi-state MS model.
Energy Technology Data Exchange (ETDEWEB)
Faraggi, A.E. [Univ. of Florida, Gainesville, FL (United States). Dept. of Physics; Pati, J.C. [Univ. of Maryland, College Park, MD (United States). Dept. of Physics
1997-12-01
Recently a promising mechanism for supersymmetry breaking that utilizes both an anomalous U(1) gauge symmetry and an effective mass term m {approx} 1TeV of certain relevant fields has been proposed. In this paper we examine whether such a mechanism can emerge in superstring derived free fermionic models. We observe that certain three generation string solutions, though not all, lead to an anomalous U(1) which couples universally to all three families. The advantages of this three-family universality of U(1){sub A}, compared to the two-family case, proposed in earlier works, in yielding squark degeneracy, while avoiding radiative breaking of color and charge, are noted. The root cause of the flavor universality of U(1){sub A} is the cyclic permutation symmetry that characterizes the Z{sub 2} x Z{sub 2} orbifold compactification with standard embedding, realized in the free fermionic models by the NAHE set. It is shown that nonrenormalizable terms which contain hidden-sector condensates, generate the required suppression of the relevant mass term m, compared to the Planck scale. While the D-term of the family universal U(1){sub A} leads to squark degeneracy, those of the family dependent U(1)`s, remarkably enough, are found to vanish for the solutions considered, owing to minimization of the potential.
Energy Technology Data Exchange (ETDEWEB)
Faraggi, A.E. [Univ. of Florida, Gainesville, FL (United States). Dept. of Physics; Pati, J.C. [Univ. of Maryland, College Park, MD (United States). Dept. of Physics
1997-12-01
Recently a promising mechanism for supersymmetry breaking that utilizes both an anomalous U(1) gauge symmetry and an effective mass term m {approx} 1TeV of certain relevant fields has been proposed. In this paper we examine whether such a mechanism can emerge in superstring derived free fermionic models. We observe that certain three generation string solutions, though not all, lead to an anomalous U(1) which couples universally to all three families. The advantages of this three-family universality of U(1){sub A}, compared to the two-family case, proposed in earlier works, in yielding squark degeneracy, while avoiding radiative breaking of color and charge, are noted. The root cause of the flavor universality of U(1){sub A} is the cyclic permutation symmetry that characterizes the Z{sub 2} x Z{sub 2} orbifold compactification with standard embedding, realized in the free fermionic models by the NAHE set. It is shown that nonrenormalizable terms which contain hidden-sector condensates, generate the required suppression of the relevant mass term m, compared to the Planck scale. While the D-term of the family universal U(1){sub A} leads to squark degeneracy, those of the family dependent U(1)`s, remarkably enough, are found to vanish for the solutions considered, owing to minimization of the potential.
Topological open strings on orbifolds
Bouchard, Vincent; Marino, Marcos; Pasquetti, Sara
2008-01-01
We use the remodeling approach to the B-model topological string in terms of recursion relations to study open string amplitudes at orbifold points. To this end, we clarify modular properties of the open amplitudes and rewrite them in a form that makes their transformation properties under the modular group manifest. We exemplify this procedure for the C^3/Z_3 orbifold point of local P^2, where we present results for topological string amplitudes for genus zero and up to three holes, and for the one-holed torus. These amplitudes can be understood as generating functions for either open orbifold Gromov-Witten invariants of C^3/Z_3, or correlation functions in the orbifold CFT involving insertions of both bulk and boundary operators.
Dvali, Gia; Van Proeyen, A; Dvali, Gia; Van Proeyen, Antoine
2004-01-01
We study the embedding of cosmic strings, related to the Abrikosov-Nielsen-Olesen vortex solution, into d=4, N=1 supergravity. We find that the local cosmic string solution which saturates the BPS bound of supergravity with the D-term potential for the Higgs field and with the constant Fayet--Iliopoulos term, has 1/2 of supersymmetry unbroken. We observe an interesting relation between the gravitino supersymmetry transformation, positive energy condition and the deficit angle of the cosmic string. We argue that the string solutions with the magnetic flux with F-term potential cannot be supersymmetric, which leads us to a conjecture that D1-strings of string theory in the effective 4d supergravity may be described by the D-term strings, which we study in this paper.
Dinh, Minh-Chau; Ju, Chang-Hyeon; Kim, Sung-Kyu; Kim, Jin-Geun; Park, Minwon; Yu, In-Keun
2012-08-01
The combination of a high temperature superconducting DC power cable and a voltage source converter based HVDC (VSC-HVDC) creates a new option for transmitting power with multiple collection and distribution points for long distance and bulk power transmissions. It offers some greater advantages compared with HVAC or conventional HVDC transmission systems, and it is well suited for the grid integration of renewable energy sources in existing distribution or transmission systems. For this reason, a superconducting DC transmission system based HVDC transmission technologies is planned to be set up in the Jeju power system, Korea. Before applying this system to a real power system on Jeju Island, system analysis should be performed through a real time test. In this paper, a model-sized superconducting VSC-HVDC system, which consists of a small model-sized VSC-HVDC connected to a 2 m YBCO HTS DC model cable, is implemented. The authors have performed the real-time simulation method that incorporates the model-sized superconducting VSC-HVDC system into the simulated Jeju power system using Real Time Digital Simulator (RTDS). The performance analysis of the superconducting VSC-HVDC systems has been verified by the proposed test platform and the results were discussed in detail.
Energy Technology Data Exchange (ETDEWEB)
Wilczek, F. [Institute for Advanced Study, Princeton, NJ (United States)
1997-09-22
The asymptotic freedom of QCD suggests that at high density - where one forms a Fermi surface at very high momenta - weak coupling methods apply. These methods suggest that chiral symmetry is restored and that an instability toward color triplet condensation (color superconductivity) sets in. Here I attempt, using variational methods, to estimate these effects more precisely. Highlights include demonstration of a negative pressure in the uniform density chiral broken phase for any non-zero condensation, which we take as evidence for the philosophy of the MIT bag model; and demonstration that the color gap is substantial - several tens of MeV - even at modest densities. Since the superconductivity is in a pseudoscalar channel, parity is spontaneously broken.
Strings, paths, and standard tableaux
Dasmahapatra, S
1996-01-01
For the vacuum sectors of regime-III ABF models, we observe that two sets of combinatorial objects: the strings which parametrize the row-to-row transfer matrix eigenvectors, and the paths which parametrize the corner transfer matrix eigenvectors, can both be expressed in terms of the same set of standard tableaux. Furthermore, the momenta of the strings, the energies of the paths, and the charges of the tableaux are such that there is a weight-preserving bijection between the two sets of eigenvectors, wherein the tableaux play an interpolating role. This bijection is so natural, that we conjecture that it exists in general.
Fundamentals of Superconducting Nanoelectronics
Sidorenko, Anatolie
2011-01-01
This book demonstrates how the new phenomena in superconductivity on the nanometer scale (FFLO state, triplet superconductivity, Crossed Andreev Reflection, synchronized generation etc.) serve as the basis for the invention and development of novel nanoelectronic devices and systems. It demonstrates how rather complex ideas and theoretical models, like odd-pairing, non-uniform superconducting state, pi-shift etc., adequately describe the processes in real superconducting nanostructues and novel devices based on them. The book is useful for a broad audience of readers, researchers, engineers, P
Interacting Strings in Matrix String Theory
Bonelli, G.
1998-01-01
It is here explained how the Green-Schwarz superstring theory arises from Matrix String Theory. This is obtained as the strong YM-coupling limit of the theory expanded around its BPS instantonic configurations, via the identification of the interacting string diagram with the spectral curve of the relevant configuration. Both the GS action and the perturbative weight $g_s^{-\\chi}$, where $\\chi$ is the Euler characteristic of the world-sheet surface and $g_s$ the string coupling, are obtained.
Entanglement in a two-dimensional string theory
Donnelly, William
2016-01-01
What is the meaning of entanglement in a theory of extended objects such as strings? To address this question we consider entanglement entropy in the Gross-Taylor model, the string theory dual to two-dimensional Yang-Mills theory at large $N$. The string diagrams that contribute to the entanglement entropy describe open strings with endpoints anchored to the entangling surface, as first argued by Susskind. We develop a canonical theory of these open strings, and describe how closed strings are divided into open strings at the level of the Hilbert space, giving a precise state-counting interpretation to the entropy, including its leading $O(N^2)$ piece. In the process we reinterpret the sphere partition function as a thermal ensemble of of open strings whose endpoints are anchored to an object at the entangling surface that we call an E-brane.
Galtsov, D V; Volkov, M S; Davydov, Evgeny A.; Gal'tsov, Dmitri V.; Volkov, Mikhail S.
2006-01-01
We present globally regular vortex-type solutions for a pure SU(2) Yang-Mills field coupled to gravity in 3+1 dimensions. These gravitating vortices are static, cylindrically symmetric and purely magnetic, and they support a non-zero chromo-magnetic flux through their cross section. In addition, they carry a constant non-Abelian current, and so in some sense they are analogs of the superconducting cosmic strings. They have a compact central core dominated by a longitudinal magnetic field and endowed with an approximately Melvin geometry. This magnetic field component gets color screened in the exterior part of the core, outside of which the fields approach exponentially fast those of the electrovacuum Bonnor solutions with a circular magnetic field. In the far field zone the solutions are not asymptotically flat but tend to vacuum Kasner metrics.
Generalized Aubry-André-Harper model with p -wave superconducting pairing
Zeng, Qi-Bo; Chen, Shu; Lü, Rong
2016-09-01
We investigate a generalized Aubry-André-Harper (AAH) model with p -wave superconducting pairing. Both the hopping amplitudes between the nearest-neighboring lattice sites and the on-site potentials in this system are modulated by a cosine function with a periodicity of 1 /α . In the incommensurate case [α =(√{5 }-1 )/2 ] , due to the modulations on the hopping amplitudes, the critical region of this quasiperiodic system is significantly reduced and the system becomes easier to be turned from extended states to localized states. In the commensurate case (α =1 /2 ), we find that this model shows three different phases when we tune the system parameters: Su-Schrieffer-Heeger (SSH)-like trivial, SSH-like topological, and Kitaev-like topological phases. The phase diagrams and the topological quantum numbers for these phases are presented in this work. This generalized AAH model combined with superconducting pairing provides us with a useful test field for studying the phase transitions from extended states to Anderson localized states and the transitions between different topological phases.
AC loss of the short coaxial superconducting cable model made from ReBCO coated tapes
Energy Technology Data Exchange (ETDEWEB)
Souc, J; Goemoery, F; Vojenciak, M; Frolek, L [Institute of Electrical Engineering., Centre of Excellence CENG, SAS, 841 04 Bratislava (Slovakia); Isfort, D; Ehrenberg, J; Bock, J [Nexans SuperConductors GmbH, Chemiepark Knapsack 50351, Huerth (Germany); Usoskin, A; Rutt, A [EHTS GmbH and Co. KG, Alzenau, (EAS, HANAU) (Germany)], E-mail: eleksouc@savba.sk
2008-02-15
Coaxial cable model with both the core as well as the shield conductor made from high-temperature superconducting tapes of the 2nd generation was constructed. AC current was fed to the model of 0.5 m length using a cold core transformer system. The core consists of 14 EHTS YBCO tapes of 4 mm width, and its properties have been published already. Now the system was completed by the shield conductor using 16 ReBCO tapes of 10 mm width produced by Nexans. In this contribution, the properties of the shield conductor are reported in detail. The experimental data on ac transport loss are presented and compared with ac transport loss of the superconducting core. The currents in individual tapes and the total cable current was monitored using Rogowski coils. Significant non-uniformity of the current distribution was found, which is a common issue in short cable models. Therefore, the AC transport loss of the shield conductor was measured by 16 lifted loops placed along the cable, using the averaging method to extract the true loss voltage.
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.
Metastable Quivers in String Compactifications
Energy Technology Data Exchange (ETDEWEB)
Diaconescu, Duiliu-Emanuel; /Rutgers U., Piscataway; Donagi, Ron; /Pennsylvania U. /SLAC; Florea, Bogdan; /SLAC
2007-01-08
We propose a scenario for dynamical supersymmetry breaking in string compactifications based on geometric engineering of quiver gauge theories. In particular we show that the runaway behavior of fractional branes at del Pezzo singularities can be stabilized by a flux superpotential in compact models. Our construction relies on homological mirror symmetry for orientifolds.
Henrot-Versillé, Sophie; Leroy, Nicolas; Plaszczynski, Stéphane; Arnaud, Nicolas; Bizouard, Marie-Anne; Cavalier, Fabien; Christensen, Nelson; Couchot, François; Franco, Samuel; Hello, Patrice; Huet, Dominique; Kasprzack, Marie; Perdereau, Olivier; Spinelli, Marta; Tristram, Matthieu
2014-01-01
The production of a primordial stochastic gravitational-wave background by processes occuring in the early Universe is expected in a broad range of models. Observing this background would open a unique window onto the Universe's evolutionary history. Probes like the Cosmic Microwave Background (CMB) or the Baryon Acoustic Oscillations (BAO) can be used to set upper limits on the stochastic gravitational-wave background energy density $\\Omega_{GW}$ for frequencies above $10^{-15}$ Hz. We perform a profile likelihood analysis of the Planck CMB temperature anisotropies and gravitational lensing data combined with WMAP low-$\\ell$ polarization, BAO, South Pole Telescope and Atacama Cosmology Telescope data. We find that $\\Omega_{GW}h_{0}^{2} < 3.8 \\times 10^{-6}$ at 95\\% confidence level for adiabatic initial conditions which improves over the previous limit by a factor 2.3. Assuming that the primordial gravitational waves have been produced by a network of cosmic strings, we have derived exclusion limits in th...
Critical state model for magneto-elastic problem of thin superconducting disks
Huang, Chen-Guang; Yong, Hua-Dong; Zhou, You-He
2013-07-01
The magneto-elastic problem of a thin superconducting disk in a perpendicular magnetic field is analyzed with field-dependent critical current. We calculate numerically the body force distribution and discuss the field dependence of Jc on the magneto-elastic behavior during field ascent and descent for three critical state models: Bean, Kim, and exponential models. The results show that when considering a field dependence of Jc, the flux and remagnetization fronts have a larger moving speed towards the center of a disk relative to the Bean model. Simultaneously, the most dangerous stage of possible cracking for the disk will arrive early in the field decreasing stage. The magnetostriction loops are also presented during a full cycle of the applied field. It is interesting that the calculated magnetostriction loops for the Kim and exponential models are quite similar to the corresponding magnetostriction curves at low and high temperatures measured in the experiment.
On closed-string twist-field correlators and their open-string descendants
Anastasopoulos, Pascal; Richter, Robert
2011-01-01
In a recent paper we have proposed the possibility that the lightest massive string states could be identified with open strings living at intersections of D-branes forming small angles. In this note, we reconsider the relevant twist-field correlation functions and perform the analysis of the sub-dominant physical poles in the various channels. Our derivation is new in that it is based on the algebraic procedure for the construction of open string models starting from their closed-string `parents' rather than on the stress-tensor method. We also indicate possible generalizations and diverse applications of our approach.
Matrix Strings, Compactification Scales and Hagedorn Transition
Meana, M L; Meana, Marco Laucelli; Peñalba, Jesús Puente
1999-01-01
In this work we use the Matrix Model of Strings in order to extract some non-perturbative information on how the Hagedorn critical temperature arises from eleven-dimensional physics. We study the thermal behavior of M and Matrix theories on the compactification backgrounds that correspond to string models. We obtain some information that allows us to state that the Hagedorn temperature is not unique for all Matrix String models and we are also able to sketch how the $S$-duality transformation works in this framework.
Wong, C. H.; Wu, R. P. H.; Lortz, R.
2017-03-01
The dimensional crossover from a 1D fluctuating state at high temperatures to a 3D phase coherent state in the low temperature regime in two coaxial weakly-coupled cylindrical surfaces formed by two-dimensional arrays of parallel nanowires is studied via an 8-state 3D-XY model. This system serves as a model for quasi-one-dimensional superconductors in the form of bundles of weakly-coupled superconducting nanowires. A periodic variation of the dimensional crossover temperature TDC is observed when the inner superconducting cylindrical surface is rotated in the angular plane. TDC reaches a maximum when the relative angle between the cylinders is 2.81°, which corresponds to the maximum separation of nanowires between the two cylindrical surfaces. We demonstrate that the relative strength of phase fluctuations in this system is controllable by the rotational angle between the two surfaces with a strong suppression of the fluctuation strength at 2.81°. The phase fluctuations are suppressed gradually upon cooling, before they abruptly vanish below TDC. Our model thus allows us to study how phase fluctuations can be suppressed in quasi-one-dimensional superconductors in order to achieve a global phase coherent state throughout the nanowire array with zero electric resistance.
Energy Technology Data Exchange (ETDEWEB)
Wong, C.H., E-mail: ch.kh.vong@urfu.ru [Institute of Physics and Technology, Ural Federal University, Clear Water Bay, Kowloon (Russian Federation); Wu, R.P.H., E-mail: pak-hong-raymond.wu@connect.polyu.hk [Department of Applied Physics, The Hong Kong Polytechnic University (Hong Kong); Lortz, R., E-mail: lortz@ust.hk [Department of Physics, Hong Kong University of Science and Technology (Hong Kong)
2017-03-15
The dimensional crossover from a 1D fluctuating state at high temperatures to a 3D phase coherent state in the low temperature regime in two coaxial weakly-coupled cylindrical surfaces formed by two-dimensional arrays of parallel nanowires is studied via an 8-state 3D-XY model. This system serves as a model for quasi-one-dimensional superconductors in the form of bundles of weakly-coupled superconducting nanowires. A periodic variation of the dimensional crossover temperature T{sub DC} is observed when the inner superconducting cylindrical surface is rotated in the angular plane. T{sub DC} reaches a maximum when the relative angle between the cylinders is 2.81°, which corresponds to the maximum separation of nanowires between the two cylindrical surfaces. We demonstrate that the relative strength of phase fluctuations in this system is controllable by the rotational angle between the two surfaces with a strong suppression of the fluctuation strength at 2.81°. The phase fluctuations are suppressed gradually upon cooling, before they abruptly vanish below T{sub DC}. Our model thus allows us to study how phase fluctuations can be suppressed in quasi-one-dimensional superconductors in order to achieve a global phase coherent state throughout the nanowire array with zero electric resistance.
Ciotti, M.; Nijhuis, A.; Ribani, P. L.; Savoldi Richard, L.; Zanino, R.
2006-10-01
The new THELMA code, including a thermal-hydraulic (TH) and an electro-magnetic (EM) model of a cable-in-conduit conductor (CICC), has been developed. The TH model is at this stage relatively conventional, with two fluid components (He flowing in the annular cable region and He flowing in the central channel) being particular to the CICC of the International Thermonuclear Experimental Reactor (ITER), and two solid components (superconducting strands and jacket/conduit). In contrast, the EM model is novel and will be presented here in full detail. The results obtained from this first version of the code are compared with experimental results from pulsed tests of the ENEA stability experiment (ESE), showing good agreement between computed and measured deposited energy and subsequent temperature increase.