Gauged extended supergravity without cosmological constant: no-scale structure and supersymmetry breaking

We consider the interplay of duality symmetries and gauged isometries of supergravity models giving N-extended, spontaneously broken supergravity with a no-scale structure. Some examples, motivated by superstring and M-theory compactifications are described.Comment: AMS-LaTeX, 16 pages. Invited paper to appear in the review section of the IJMP

Electromagnetic Interaction of Massive Spin-3 State from String Theory

In the given work we study an interaction of second massive state of an open boson string with the constant electromagnetic field. This state contains massive fields with spins 3 and 1. Using the method of an open string BRST quantization, we receive gauge-invariant lagrangian, describing the electromagnetic interaction of these fields. From the explicit view of transformations and lagrangian it follows that the presence of external constant e/m field leads to the mixing of the given level states. Most likely that the presence of the external field will lead to the mixing of the states at other mass string levels as well.Comment: 17 pages, LaTeX, no figure

Secondary electron yield of emissive materials for large-area micro-channel plate detectors: surface composition and film thickness dependencies

The ongoing development of Atomic Layer Deposition (ALD) enables the use of relatively inexpensive and robust borosilicate micro-channel substrates for use as Micro-Channel Plates (MCPs). The surfaces of the channels in these glass plates are functionalized to control the conductivity as well as the Secondary Electron Yield (SEY). The extensive SEY data found in literature show significant variation for a given material depending on the apparatus, the measurement procedure, and the sample preparation and handling. We present systematic studies on the effects of film thickness and surface chemical composition on SEY. We have modified an existing ultra-high vacuum apparatus containing X-ray and Ultraviolet Photoelectron Spectrometers (XPS and UPS, respectively) by adding a modified Low Energy Electron Diffraction (LEED) module for SEY measurements. With these tools, we have characterized the secondary electron emissive properties for MgO, Al2O3, and multilayered MgO/TiO2 structures to serve as electron emissive layers in the channels of the MCPs

N=4 gauged supergravity and a IIB orientifold with fluxes

We analyze the properties of a spontaneously broken D=4, N=4 supergravity without cosmological constant, obtained by gauging translational isometries of its classical scalar manifold. This theory offers a suitable low energy description of the super-Higgs phases of certain Type-IIB orientifold compactifications with 3-form fluxes turned on. We study its N=3,2,1,0 phases and their classical moduli spaces and we show that this theory is an example of no-scale extended supergravity.Comment: Misprints corrected. Version appeared on NJP 4 (2002)7

N=2 Super-Higgs, N=1 Poincare' Vacua and Quaternionic Geometry

In the context of N=2 supergravity we explain the occurrence of partial super-Higgs with vanishing vacuum energy and moduli stabilization in a model suggested by superstring compactifications on type IIB orientifolds with 3-form fluxes. The gauging of axion symmetries of the quaternionic manifold, together with the use of degenerate symplectic sections for special geometry, are the essential ingredients of the construction.Comment: 18 page