Revisiting higher-spin gyromagnetic couplings

We analyze Bosonic, Heterotic, and Type II string theories compactified on a generic torus having constant moduli. By computing the hamiltonian giving the interaction between massive string excitations and U(1) gauge fields arising from the graviton and Kalb-Ramond field upon compactification, we derive a general formula for such couplings that turns out to be universal in all these theories. We also confirm our result by explicitly evaluating the relevant string three-point amplitudes. From this expression, we determine the gyromagnetic ratio g of massive string states coupled to both gauge-fields. For a generic mixed symmetry state, there is one gyromagnetic coupling associated with each row of the corresponding Young Tableau diagram. For all the states having zero Kaluza Klein or Winding charges, the value of g turns out to be 1. We also explicitly consider totally symmetric and mixed symmetry states (having two rows in the Young diagram) associated with the first Regge-trajectory and obtain their corresponding g value.

The harder they fall, the bigger they become: tidal trapping of strings by microstate geometries

We consider the fate of a massless (or ultra-relativistic massive) string probe propagating down the BTZ-like throat of a microstate geometry in the D1-D5 system. Far down the throat, the probe encounters large tidal forces that stretch and excite the string. The excitations are limited by the very short transit time through the region of large tidal force, leading to a controlled approximation to tidal stretching. We show that the amount of stretching is proportional to the incident energy, and that it robs the probe of the kinetic energy it would need to travel back up the throat. As a consequence, the probe is effectively trapped far down the throat and, through repeated return passes, scrambles into the ensemble of nearby microstates. We propose that this tidal trapping may lead to weak gravitational echoes.

A Submerged Floating Tube Bridge Concept for the Bjørnafjord Crossing: Marine Operations

A submerged floating tube bridge (SFTB) concept is one of the three alternatives for the Bjørnafjord crossing in Norway. Two SFTB designs have been developed: one pontoon-stabilized and one tether-stabilized. There are no submerged floating tube bridges yet built and installed. Consequently there is no direct practical experience with assembly and installation of such massive string-like structures. The purpose of this article is to describe possible means of fabrication, assembling, jointing and installation of SFTB elements and the tube-bridge itself. All major project activities have been divided into stages. Further, these stages have been subdivided into factual steps to demonstrate feasibility based on various criteria. The major construction challenge is to assembly fabricated SFTB elements into one 4580 m string in a floating condition and then to tow and install it in the fjord. The focus was to utilize existing technologies and experiences available from offshore industry to the fullest extent, so that conventional tools and methods could be applied to this new application. Possible solutions both for the tether-stabilized and pontoon-stabilized alternatives — with differences in the foundation/tether and pontoon installations and associated SFTB interfaces — have been developed.

Locally rotationally symmetric Bianchi type I massive string cosmological model with vacuum energy density and magnetic field in general relativity

A locally rotationally symmetric (LRS) Bianchi type I massive string cosmological model with vacuum energy density (Λ) and magnetic field is investigated. To get a deterministic model of the universe, we assume that shear (σ) is proportional to expansion (θ) and Λ ∼ 1/R2 as considered by Chen and Wu (Phys. Rev. D, 41, 695 (1990)) where R is a scale factor. We find that the total energy density (ρ), the particle density ρp decreases with time. The strong energy conditions as given by Hawking and Ellis (The large scale structure of space–time. Cambridge University Press, Cambridge, UK. p. 88. (1974)) are satisfied. The vacuum energy density decreases with time, which matches with astronomical observation. The model in general represents anisotropic space–time because of the presence of strings. The total energy density and string tension density decrease because of the presence of a magnetic field. Both the models have point-type singularities at T = 0 and τ = 0, respectively. The other physical aspects of the models are also discussed.