15442219
Quantum cosmological Friedman models with a massive Yang–Mills field
We prove the existence of a spectral resolution of the Wheeler–DeWitt equation when the matter field is provided by a massive Yang–Mills field. The resolution is achieved by first solving the free eigenvalue problem for the gravitational field and then the constrained eigenvalue problem for the Yang–Mills field. In the latter case, the mass of the Yang–Mills field assumes the role of the eigenvalue.
9548206
On the foliation of space-time by constant mean curvature hypersurfaces
We prove that the mean curvature $\tau$ of the slices given by a constant mean curvature foliation can be used as a time function, i.e. $\tau$ is smooth with non-vanishing gradient.
14259478
Transition from big crunch to big bang in brane cosmology
We consider branes N = I × S0, where S0 is an n–dimensional space form, not necessarily compact, in a Schwarzschild-AdS(n+2) bulk N . The branes have a big crunch singularity. If a brane is an ARW space, then, under certain conditions, there exists a smooth natural transition flow through the singularity to a reflected brane N , which has a big bang singularity and which can be viewed as a brane in a reflected Schwarzschild-AdS(n+2) bulk N . The joint branes N ∪ N can thus be naturally embedded in R × S0, hence there exists a second possibility of defining a smooth transition from big crunch to big bang by requiring that N ∪ N forms a C∞-hypersurface in R × S0. This last notion of a smooth transition also applies to branes that are not ARW spaces, allowing a wide range of possible equations of state.
55245277
A unified quantum theory II: gravity interacting with Yang-Mills and spinor fields
We quantize the interaction of gravity with Yang-Mills and spinor fields, hence offering a quantum theory incorporating all four fundamental forces of nature. Using canonical quantization we obtain solutions of the Wheeler-DeWitt equation in a vector bundle and the method of second quantization leads to a symplectic vector space $(V,\om)$ and a corresponding CCR representation for the bosonic components and a CAR representation for the fermionic part. The solution space of the Wheeler-DeWitt equation is invariant under gauge transformations and under isometries in the spacelike base space $\so$ of a given Riemannian metric $\rho_{ij}$. We also define a net of local subalgebras which satisfy four of the Haag-Kastler axioms.
14951562
The mass of a Lorentzian manifold
We define a physically reasonable mass for an asymptotically Robertson-Walker (ARW) manifold which is uniquely defined in the case of a normalized representation.
54221487
The quantization of gravity in globally hyperbolic spacetimes
We apply the ADM approach to obtain a Hamiltonian description of the Einstein-Hilbert action. In doing so we add four new ingredients: (i) We eliminate the diffeomorphism constraints. (ii) We replace the densities $\sqrt g$ by a function $\f(x,g_{ij})$ with the help of a fixed metric $\chi$ such that the Lagrangian and hence the Hamiltonian are functions. (iii) We consider the Lagrangian to be defined in a fiber bundle with base space $\so$ and fibers F(x) which can be treated as Lorentzian manifolds equipped with the Wheeler-DeWitt metric. It turns out that the fibers are globally hyperbolic. (iv) The Hamiltonian operator $H$ is a normally hyperbolic operator in the bundle acting only in the fibers and the Wheeler-DeWitt equation $Hu=0$ is a hyperbolic equation in the bundle. Since the corresponding Cauchy problem can be solved for arbitrary smooth data with compact support, we then apply the standard techniques of QFT which can be naturally modified to work in the bundle.
121817998
Electroproduction cross sections in the resonance region measured at large scattering angles
To complete data on resonance electroproduction we constructed an electron spectrometer with large angular and momentum acceptance. As a first result inclusive cross sections for an invariant hadronic mass 1.2<W<1.7 GeV and a four momentum transfer squared 0.5<Q2<1.5 (GeV/c)2 and for values of the polarization parameter 0.1<ɛ<0.25 are presented. Combining our results with the SLAC 4°-data we obtain σL/σT in the specified kinematical range.
123586923
A resonance analysis of electroproduction data
We determinedN* electromagnetic transition form factors using π- and η-electroproduction data in the resonance region published till December, 1978. We discuss problems with the results obtained by various experimental groups. The method of analysis is a modification of the procedure used by Devenish and Lyth. Using the new photoproduction results of Barbour and Crawford and the δ- and η-data published till 1978, we are able to parametrise all multipoles in a unique way and to describe the background without further high energy input. Thus a better description of the data with less assumptions is achieved. However, it is still not possible to determine more multipoles than previously.