Stationary rotating string world models with a magnetic field

Following the techniques used by Letelier and Stachel some new physically relevant stationary solutions of string cosmology with magnetic field are presented. In these solutions, the flow vector of matter has non-zero rotation and the cosmological constant is taken to be non-zero. Previously known solutions are derived as particular cases from our class of solutions. Some string models with vanishing cosmological constant are also discussed.     

Folded world sheets and the orientable string

Classical solutions for the open relativistic string with a single junction are examined and a new class of kinked solutions presented. An interpretation of the phenomena of reverse parametrisation on one arm is offered in terms of oriented chains and the consequence that this has for folded world sheets is discussed. A physical interpretation for certain junction sites is presented through interaction of the string with an external field.     

Vibration of a string wrapping and unwrapping around an obstacle

The problem of a string vibrating against a smooth obstacle is investigated in this paper. The obstacle is located at one of the boundaries and the string is assumed to wrap and unwrap around the obstacle during vibration. The wrapping of the obstacle is modeled by a series of perfectly inelastic collisions between the obstacle and adjacent segments of the string and unwrapping is assumed to be energy conserving. The geometry of the string is determined iteratively starting from an initial configuration where the string is vibrating in a single mode and is not in contact with the obstacle. The obstacle can be regarded as a passive mechanism for vibration suppression in which the energy lost during each cycle of oscillation depends on the energy content of the string at the beginning of the cycle. Numerical simulation results are provided for the string vibrating in different modes for circular- and elliptic-shaped obstacles. The loss of energy is found to be greater for higher modes of oscillation and for obstacles that induce greater length of wrapping.     

Relativistic-electron scattering on an atomic string of a crystal at ultrasmall angles of particle incidence on a string

The classical and quantum scattering of fast electrons on an atomic string of a crystal is considered at angles of particle incidence on the string that are much smaller than the critical angle of axial channeling. The investigation was performed within the simplest approximation of the continuous atomic-string potential in the form of a cutoff Coulomb potential. For this case, the azimuthal scattering of particles at an angle exceeding 180° in the plane orthogonal to the string axis is shown to be possible for all impact-parameter values. It is demonstrated that, in particle scattering on a string, an effect can occur that is similar to the Ramsauer-Townsend effect, which consists in a considerable reduction of the total cross section for slow-electron scattering on atoms.     

Transient response of a string on an elastic base

The transient response of a stretched string resting on an elastic base and subjected to impulsive end loading is treated herein. The analysis is based on the concept of a wave as a carrier of discontinuities in the field variable and its derivatives. These discontinuities are determined from a recurrence relation which is in turn generated by using a time-harmonic asymptotic series solution to the equation of motion. Numerical examples are treated where the responses of the string to delta and step function boundary loads are obtained. The results confirm the influence of the base modulus on the transient displacement, velocity and slope distributions in the string. The distortion of the transients and the discontinuities in the velocity and slope are evident from the results presented. The transient response of the string due to other boundary conditions can be obtained by using the present results.     

Modeling the eardrum as a string with distributed force

In this paper, an analytical model of the tympanic membrane is introduced where the two-dimensional tympanic membrane is reduced to a one-dimensional string. It is intended to bridge the gap between lumped-element models and finite-element models. In contrast to known lumped-element models, the model takes the distributed effect of the sound field on the tympanic membrane into account. Compared to finite-element models, it retains the advantage of a low number of parameters. The model is adjusted to forward and reverse transfer functions of the guinea-pig middle ear. Although the fitting to experimental data is not perfect, important conclusions can be drawn. For instance, the model shows that the delay of surface waves on the tympanic membrane can be different from the signal transmission delay of the tympanic membrane. In a similar vein, the standing wave ratio on the tympanic membrane and within the ear canal can considerably differ. Further, the model shows that even in a low-loss tympanic membrane the effective area, which commonly is associated with the transformer ratio in a lumped-element and some hybrid circuit models, not only is frequency-dependent, but also different for forward and reverse transduction.     

Classification of world sheet instantons and the path integral measure in string theories

A classification of world sheet instantons propagating in some internal spaces is presented. The associated path integral measure problem or θ-angles, as discussed by Wen and Witten, and by Li, is addressed.     

Bloch walls and macroscopic string states in Bethe's solution of the heisenberg ferromagnetic linear chain

We present a calculation of the lowest excited states of the Heisenberg ferromagnet in 1D for any wave vector. These turn out to be string solutions of Bethe's equations with a macroscopic number of particles in them. They are identified as generalized quantum Bloch wall states, and a simple physical picture is provided for the same.     

Dirac string rotations as a key to spin and statistics of dyons

The statistics of the dyonic wave functions in quantum mechanics is crucial in understanding both the fermionic behavior of the dually charged particles and the role played by the Dirac string. The spinstatistics connection for an electric-magnetic system is derived by treating the interchange operation as a 2π rotation of a singularity line of dyons. Furthermore, the invariance under multivalued gauge transformations and under change of canonical momentum representations is established for our method.     

Nonequilibrium relaxation of an elastic string in a random potential

We study the nonequilibrium motion of an elastic string in a two dimensional pinning landscape using Langevin dynamics simulations. The relaxation of a line, initially flat, is characterized by a growing length L(t) separating the equilibrated short length scales from the flat long distance geometry that keeps a memory of the initial condition. We show that, in the long time limit, L(t) has a nonalgebraic growth with a universal distribution function. The distribution function of waiting times is also calculated, and related to the previous distribution. The barrier distribution is narrow enough to justify arguments based on scaling of the typical barrier.     

Creep motion of an elastic string in a random potential

We study the creep motion of an elastic string in a two-dimensional pinning landscape by means of Langevin dynamics simulations. We find that the velocity-force characteristics are well described by the creep formula predicted from phenomenological scaling arguments. We analyze the creep exponent mu and the roughness exponent zeta. Two regimes are identified: when the temperature is larger than the strength of the disorder, we find mu approximately 1/4 and zeta approximately 2/3, in agreement with the quasi-equilibrium-nucleation picture of creep motion; on the contrary, when lowering the temperature enough, the values of mu and zeta increase, showing a strong violation of the latter picture.     

Effective dynamics of an electrically charged string with a current

Equations of motion for an electrically charged string with a current in an external electromagnetic field with regard to the first correction due to the self-action are derived. It is shown that the reparameterization invariance of the free action of the string imposes constraints on the possible form of the current. The effective equations of motion are obtained for an absolutely elastic charged string in the form of a ring (circle). Equations for the external electromagnetic fields that admit stationary states of such a ring are derived. Solutions to the effective equations of motion of an absolutely elastic charged ring in the absence of external fields as well as in an external uniform magnetic field are obtained. In the latter case, the frequency at which one can observe radiation emitted by the ring is evaluated. A model of an absolutely nonstretchable charged string with a current is proposed. The effective equations of motion are derived within this model, and a class of solutions to these equations is found.     

Radio jets and galaxies as cosmic string probes

The lensing effect of a cosmic string is studied, and some new methods are proposed to detect the cosmic string. The technique for using jets as extended gravitational lensing probes was first explored by Kronberg.We use the “alignment-breaking parameter” ηG as a sensitive indicator of gravitational distortion by a wiggly cosmic string. Then, we applied the non-constant deflection angle to jets, and ηG of a specific jet is just related to the projected slope of the jet. At least three jets in the sample of Square Kilometer Array (SKA) would have significant signals (ηG>10°) if the wiggly infinite cosmic string existed. The distortion of elliptical object is also studied and used to do a statistical research on the directions of axes and ellipticities of galaxies. In the direction of the string, we find that galaxies appear to be more elliptical for an observer and the distribution of apparent ellipticity changes correspondingly. The ellipticity distribution of current SDSS spiral sample has the signalto-noise ratio up to 8.48 which is large enough for astronomical observations. The future survey, such as Large Synoptic Survey Telescope (LSST) and Dark Energy Survey (DES) would weaken the requirement of special geometry in the data processing. As a result, all kinds of distributions, including ellipticity axis distribution, would serve as probes to detect wiggly strings in the near future. In brief, if a wiggly cosmic string existed, these signals would be convenient to be observed with the future weak lensing survey or other surveys in the deep space. If there was no lensing signal in these distributions, it would give the upper limit of the abundance of infinite strings.     

Nonlocality as a feature of the physical world

Aprediction puzzle leads to a form ofnecessary realism which forces the rejection of a central tenet of the Copenhagen interpretation. This leads to reconsidering conceptual difficulties related to Bell's locality premise. It is shown that aparadox of elementary probability theory puts new light on Bell's assumption that causality and statistical independence are mutually incompatible. Nemo dat quod non habet : No one can offer more than he has ability to give; in that spirit, this paper is dedicated to the memory of J.S. Bell.     

Gravity beyond quantum theory: Electron as a closed heterotic string

The observable gravitational and electromagnetic parameters of an electron determine that its background should be the Kerr-Newman (KN) solution of the rotating black hole without horizons. This metric has a topological defect—the Kerr singular ring which, as we show, is a closed heterotic string of the Compton radius a = ?/(2m). We show that the Dirac equation emerges as a consequence of the underlying KN gravity and string theory. Regularization of the KN solution leads to a model of gravitating soliton of the oscillon type, in which the closed heterotic string is positioned on the edge rim of a disklike vacuum bubble. It is suggested that the string-like core of the electron should be experimentally observable by the novel methods of the “Deeply Virtual (nonforward) Compton scattering”.