15426291
Topological amplitudes in string theory
We show that certain type II string amplitudes at genus g are given by the topological partition function Fg discussed recently by Bershadsky, Cecotti, Ooguri and Vafa. These amplitudes give rise to a term in the four-dimensional effective action of the form ΣgFgW2g, where W is the chiral superfield of N = 2 supergravitational multiplet. The holomorphic anomaly of Fg is related to non-localities of the effective action due to the propagation of massless states. This result generalizes the holomorphic anomaly of the one loop case which is known to lead to non-harmonic gravitational couplings.
14387997
N = 2 HETEROTIC SUPERSTRING AND ITS DUAL THEORY IN FIVE DIMENSIONS
Abstract We study quantum effects in five dimensions in heterotic superstring theory compactified on K 3 × S 1 and analyze the conjecture that its dual effective theory is eleven-dimensional supergravity compactified on a Calabi-Yau threefold. This theory is also equivalent to type II superstring theory compactified on the same Calabi-Yau manifold, in an appropriate large volume limit. In this limit the conifold singularity disappears and is replaced by a singularity associated to enhanced gauge symmetries, as naively expected from the heterotic description. Furthermore, we exhibit the existence of additional massless states which appear in the strong coupling regime of the heterotic theory and are related to a different type of singular points on Calabi-Yau threefolds.
120318508
Low-energy softly-broken supersymmetry
Abstract We consider supersymmetric low-energy lagrangians based on the gauge group SU(3) × SU(2) × U(1) × Ũ(1), where Ũ(1) is an additional axial group a la Fayet. Models with explicit soft breaking of supersymmetry are considered as an alternative to models with axial anomalies. We argue that soft breaking can be very efficient and illustrate this with a simple example in which the introduction of a negative mass squared term for only one scalar field leads to a phenomenologically interesting model.
120401055
Dilaton Couplings at Large Distances
Abstract The large-distance behaviour of dilaton couplings is studied within the framework of four-dimensional heterotic superstring theories. String loop corrections violate universality of dilaton and graviton couplings, increasing dilaton couplings at large distances. This implies a serious problem for string theories, unless a non-zero dilaton mass is generated.
120574302
Stability of supersymmetric ground state in chiral theories
Abstract The effective action for the scalar propagator is studied in supersymmetric chiral gauge theories. The form of the scalar potential ensures the stability of the supersymmetric ground state, even for large values of the coupling constant. It is found however, that the gluino condensation tends to destabilize the system. This may signal dynamical supersymmetry breaking.
62835109
Lectures on heterotic-type I duality
In the last couple of years, there has been remarkable progress in understanding non-perturbative aspects of string theories. The new ingredient is the discovery of various duality symmetries; these, in particular, invert the coupling constant and exchange perturbative states with non-perturbative solitonic excitations. Since inversion of the coupling involves the Planck constant ħ, duality symmetries can be realized only at the quantum level. Once the dual models are identified, non-perturbative dynamics of one model can be studied by means of the standard perturbative techniques in the other model.
136548606
Analysis of the Performance of the Eight Superconducting Quadrupoles for the Lep Low-Beta Insertions
The LEP low-beta quadrupoles are iron-free superconducting magnets having a warm bore of 120 mm in diameter, an effective length of 2 m and a nominal gradient of 36 T m−l. The coils form a two-block approximation of the cosine 2θ distribution, and are wound from monolithic multifilamentary NbTi conductor; mechanical prestress is obtained by means of aluminium shrinking rings. Following manufacture and appraisal of a prototype magnet, eight series units have been produced by industry and thoroughly tested and measured prior to installation into LEP. In this paper, a brief description of the manufacturing technique is given, and the results of tests and measurements are presented and compared with the performance expected from calculations and previous experience. The analysis reveals the tolerances on field quality which can reasonably be obtained with this type of construction.
134114230
Effect of Fast Neutron Irradiation on Current Transport Properties of HTS Materials
The effect of fast neutron irradiation with energy up to 35 MeV and integrated fluence of up to 5 x 10 cm on the current transport properties of HTS materials Bi-2212 and Bi-2223 has been studied, both at liquid nitrogen and at room temperatures. The samples irradiated were selected after verification of the stability of their superconducting properties after temperature cycling in the range of 77 K 293 K. It has been found that the irradiation by fast neutrons up to the above dose does not produce a significant degradation of critical current. The effect of room temperature annealing on the recovery of transport properties of the irradiated samples is also reported, as is a preliminary microstructure investigation of the effect of irradiation on the soldered contacts.
107865879
Progress in the system design of the inner triplet of 70 mm aperture quadrupoles for the LHC low-beta insertions
54553106
Quench performance and field quality measurements of the first LHC low-/spl beta/ quadrupole model
As part of the LHC magnet development program, CERN in collaboration with Oxford Instruments has designed, built and tested a one metre model of a 70 mm aperture low-/spl beta/ quadrupole. The magnet features a four layer coil, and is designed for 250 T/m at 1.9 K. We review the results of the magnet training and quench propagation studies performed at 4.3 K and 1.9 K, and report on the magnetic field measurements.
115712937
The polarization wigglers in LEP
Twelve strong wigglers, primarily intended to increase t.he polarization rate and level, were iustallcd in I.I?P during the 1990-91 shutdown. Al injection energy in particular, the effects of synchrotron radiat.iou in t,hesfl wigglers c.ompletely dominate those from the rest, of tlrc, rirlg. Tllikir design and commiGouing are dcscribt,d Among several applications, the substantial cont~rolled tturictl-li,ngttlf~r~irlg of which they are capable has proved to bcs import,allt, iI1 increasing the intensit,y of the LI?P beams. ‘1’11~ rnensured effects of the wigglt%rs 011 thr, beams and VafuIIril iir(’ conipared with theoretical pretlic.tious.