String theory predictions for future accelerators

Physics Letters B, 1992

Recent calculations have shown that the string unification scale is naturally about two orders of magnitude larger than a typical supersymmetric grand unification scale compatible with the latest LEP data on sin20w and a3. Studying the evolution of the gauge couplings of the string derived models based on the SU (4) × SU (2) L × SU (2) a and SU ( 3 ) 3 gauge groups, we examine the conditions that make consistent the high string unification scale with the low energy phenomenology. Assuming only the content of the minimal supersymmetric standard model below a reasonable grand unification scale, we derive the constraints on the string spectrum of the above models.

Journal of High Energy Physics, 2012

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 √ s = 14 TeV. It is shown that spin degeneracy at the dijet resonance can be observed by looking the χ-distribution with integrated luminosity of 20 fb −1. It is shown that the second resonance can be observed at rather close to the first resonance in the dijet invariant mass distribution with integrated luminosity of 50 fb −1. These are inevitable signatures of low-scale string models.

Journal of High Energy Physics, 2001

We propose a framework where the string scale as well as all compact dimensions are at the electroweak scale ∼ TeV −1 . The weakness of gravity is attributed to the small value of the string coupling g s ∼ 10 −16 , presumably a remnant of the dilaton's runaway behavior, suggesting the possibility of a common solution to the hierarchy and dilaton-runaway problems. In spite of the small g s , in type II string theories with gauge interactions localized in the vicinity of NS5-branes, the standard model gauge couplings are of order one and are associated with the sizes of compact dimensions. At a TeV these theories exhibit higher dimensional and stringy behavior. The models are holographically dual to a higher dimensional non-critical string theory and this can be used to compute the experimentally accessible spectrum and self-couplings of the little strings. In spite of the stringy behavior, gravity remains weak and can be ignored at collider energies. The Damour-Polyakov mechanism is an automatic consequence of our scenario and suggests the presence of a massless conformally-coupled scalar, leading to potentially observable deviations from Einstein's theory, including violations of the equivalence principle.

Proceedings of 5th International School on Field Theory and Gravitation — PoS(ISFTG)

This is short review of tachyon condensation and open string field theory. After a brief introduction to open string theory, the SFT action is introduced and illustrated. Next comes tachyon condensation in the level truncation approach, which introduces the main topic: the description of the analytic solution and the proof of the first two conjectures by Sen. The third conjecture is discussed in the framework of vacuum SFT. Finally the subject of open-closed string duality is tackled by commenting about an attempt at showing a more explicit connection between open and closed strings.

The heterotic string-derived models in the free fermionic formulation give rise to some of the most realistic string models to date, which possess N = 1 space-time

Nuclear Physics B, 1995

We i n v estigate the eld dependence of the gauge couplings of N = 1 string vacua from the point of view of the low energy eective quantum eld theory. W e nd that eld-theoretical considerations severely constrain the form of the string loop corrections; in particular, the dilaton dependence of the gauge couplings is completely universal at the one-loop level. The moduli dependence of the string threshold corrections is also constrained, and we illustrate the power of such constraints with a detailed discussion of the orbifold vacua and the (2; 2) (Calabi-Yau) vacua of the heterotic string.

Arxiv preprint arXiv: …, 2009

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 review possible signals of string physics at the Large Hadron Collider.

We review some recent results on the calculation of renormalization constants in Yang-Mills theory using open bosonic strings. The technology of string amplitudes, supplemented with an appropriate continuation off the mass shell, can be used to compute the ultraviolet divergences of dimensionally regularized gauge theories. The results show that the infinite tension limit of string amplitudes corresponds to the background field method in field theory. (Proceedings of the Workshop "Strings, Gravity and Physics at the Planck scale ", Erice (Italy), September 1995. Preprint DFTT 82/95) 2 PAOLO DI VECCHIA ET AL.

Preface 1. Introduction 1.1. Motivation 1 1.2. Known models (interacting) 3 1.3. Aspects 4 1.4. Outline 6 2. General light cone 2.1. Actions 8 2.2. Conformal algebra 10 2.3. Poincaré algebra 13 2.4. Interactions 16 2.5. Graphs 19 2.6. Covariantized light cone 20 Exercises 23 3. General BRST 3.1. Gauge invariance and constraints 25 3.2. IGL(1) 29 3.3. OSp(1,1|2) 35 3.4. From the light cone 38 3.5. Fermions 45 3.6. More dimensions 46 Exercises 51 4. General gauge theories 4.1.

International Journal of Modern Physics A, 2012

In recent years it has been realized that in string/M theories compactified to four dimensions which satisfy cosmological constraints, it is possible to make some generic predictions for particle physics and dark matter: a non-thermal cosmological history before primordial nucleosynthesis, a scale of supersymmetry breaking which is "high" as in gravity mediation, scalar superpartners too heavy to be produced at the LHC (although gluino production is expected in many cases), and a significant fraction of dark matter in the form of axions. When the matter and gauge spectrum below the compactification scale is that of the MSSM, a robust prediction of about 125 GeV for the Higgs boson mass, predictions for various aspects of dark matter physics, as well as predictions for future precision measurements, can be made. As a prototypical example, M theory compactified on a manifold of G2 holonomy leads to a good candidate for our "string vacuum", with the TeV scale emerging from the Planck scale, a de Sitter vacuum, robust electroweak symmetry breaking, and solutions of the weak and strong CP problems. In this article we review how these and other results were derived, from the key theoretical ideas to the final phenomenological predictions.