NOTE ON MANIFEST LORENTZ AND GENERAL COORDINATE INVARIANCE IN DUALITY SYMMETRIC MODELS.

We consider a generalization of a duality symmetric model proposed by Schwarz and Sen. It is based on enlarging the model with a dynamical vector field being a time-like component of a local Lorentz frame. This allows one to preserve the manifest Lorentz invariance of the model in flat space--time. The presence of this field is regarded as a relic of gravitational interaction which respects the general coordinate invariance in curved space--time but breaks the local Lorentz symmetry in tangent space down to its spatial subgroup.Comment: 7 pages, LaTeX file

A landscape of non-supersymmetric AdS vacua on coset manifolds

We construct new families of non-supersymmetric sourceless type IIA AdS4 vacua on those coset manifolds that also admit supersymmetric solutions. We investigate the spectrum of left-invariant modes and find that most, but not all, of the vacua are stable under these fluctuations. Generically, there are also no massless moduli.Comment: 20 pages, 11 figures, v2: added some clarifications, references, v3: corrections addressing comments refere

On Dimensional Degression in AdS(d)

We analyze the pattern of fields in d+1 dimensional anti-de Sitter space in terms of those in d dimensional anti-de Sitter space. The procedure, which is neither dimensional reduction nor dimensional compactification, is called dimensional degression. The analysis is performed group-theoretically for all totally symmetric bosonic and fermionic representations of the anti-de Sitter algebra. The field-theoretical analysis is done for a massive scalar field in AdS(d+d$^\prime$) and massless spin one-half, spin one, and spin two fields in AdS(d+1). The mass spectra of the resulting towers of fields in AdS(d) are found. For the scalar field case, the obtained results extend to the shadow sector those obtained by Metsaev in [1] by a different method.Comment: 30 page

The degenerate gravitino scenario

In this work, we explore the "degenerate gravitino" scenario where the mass difference between the gravitino and the lightest MSSM particle is much smaller than the gravitino mass itself. In this case, the energy released in the decay of the next to lightest sypersymmetric particle (NLSP) is reduced. Consequently the cosmological and astrophysical constraints on the gravitino abundance, and hence on the reheating temperature, become softer than in the usual case. On the other hand, such small mass splittings generically imply a much longer lifetime for the NLSP. We find that, in the constrained MSSM (CMSSM), for neutralino LSP or NLSP, reheating temperatures compatible with thermal leptogenesis are reached for small splittings of order 10^{-2} GeV. While for stau NLSP, temperatures of 4x10^9 GeV can be obtained even for splittings of order of tens of GeVs. This "degenerate gravitino" scenario offers a possible way out to the gravitino problem for thermal leptogenesis in supersymmetric theories.Comment: 27 pages, 10 figures and 1 table. Minor typos and references fixed. Matches published version in JCAP

The Space Filling Dirichlet 3-Brane in N=2, D=4 Superspace

We discuss a four-dimensional Volkov-Akulov supersymmetric theory on a D3-brane with N=2 supersymmetry broken down to N=1.Comment: LaTeX2e file, espcrc2.sty, 8 pages. Based on talks given at the D. V. Volkov Memorial Conference "Supersymmetry and Quantum Field Theory" (25-29 July, 2000, Kharkov, Ukraine). To be published in Nuclear Physics B Conference Supplement