Search results for "General Theoretical Physics"
showing 10 items of 18 documents
On the canonical structure of higher-derivative field theories. The gravitational WZW-model
1992
Abstract A general expression for the symplectic structure of a higher-derivative lagrangian field theory is given. General relativity and the gravitational WZW-model are considered in this framework. In the second case we work out explicitly the Poisson bracket for both chiral solutions giving rise, in two different ways, to the classical exchange algebra of the SL q (2) group.
The crossover from first to second-order finite-size scaling: a numerical study
1994
We consider a particular case of the two dimensional Blume-Emery-Griffiths model to study the finite-size scaling for a field driven first-order phase transition with two coexisting phases not related by a symmetry. For low temperatures we verify the asymptotic (large volume) predictions of the rigorous theory of Borgs and Kotecky. Near the critical temperature we show that all data fit onto a unique curve, even when the correlation length ξ becomes comparable to or larger than the size of the system, provided the linear dimension L of the system is rescaled by ξ
Preparing single ultra-cold antihydrogen atoms for free-fall in GBAR
2014
We discuss an experimental approach allowing to prepare antihydrogen atoms for the GBAR experiment. We study the feasibility of all necessary experimental steps: The capture of incoming $\bar{\rm H}^{+}$ ions at keV energies in a deep linear RF trap, sympathetic cooling by laser cooled Be+ ions, transfer to a miniaturized trap and Raman sideband cooling of an ion pair to the motional ground state, and further reducing the momentum of the wavepacket by adiabatic opening of the trap. For each step, we point out the experimental challenges and discuss the efficiency and characteristic times, showing that capture and cooling are possible within a few seconds. We discuss an experimental approach…
Quantum cosmological approach to 2d dilaton gravity
1993
We study the canonical quantization of the induced 2d-gravity and the pure gravity CGHS-model on a closed spatial section. The Wheeler-DeWitt equations are solved in (spatially homogeneous) choices of the internal time variable and the space of solutions is properly truncated to provide the physical Hilbert space. We establish the quantum equivalence of both models and relate the results with the covariant phase-space quantization. We also discuss the relation between the quantum wavefunctions and the classical space-time solutions and propose the wave function representing the ground state.
BARYOGENESIS IN SUPERGRAVITY INFLATIONARY MODELS
1985
Abstract Realistic N=1 supergravity theories with a gravitino mass of order 1 TeV require a period of inflation to dilute the gravitino abundance. Moreover, if the gravitino is unstable the reheat temperature is bounded to be no greater than O(108 GeV). We show that such models may still have acceptable rates of baryosynthesis and discuss possible mechanisms.
Equivariance in topological gravity
1992
Abstract We present models of topological gravity for a variety of moduli space conditions. In four dimensions, we construct a model for self-dual gravity characterized by the moduli condition R + μν =0, and in two dimensions we treat the case of constant scalar curvature. Details are also given for both flat and Yang-Mills type moduli conditions in arbitrary dimensions. All models are based on the same fundamental multiplet which conveniently affords the construction of a complete hierarchy of observables. This approach is founded on a symmetry algebra which includes a local vector supersymmetry, in addition to a global BRST-like symmetry which is equivariant with respect to Lorentz transf…
Neutrinoless double electron capture as a tool to measure the electron neutrino mass
1983
Abstract A nucleus (Z, A) may capture two atomic electrons to become (Z − 2, A). For Majorana neutrinos this may occur with no neutrino emission, the process is a virtual mixing of the parent atom and the daughter atom with two electron holes. The process becomes real as the daughter atom de-excites. In some cases where the daughter nucleus is excited, the neutrinoless decay may be enhanced by its proximity to a virtual resonance. We identify the 112 Sn → 112 Cd transition as a good case. The no-neutrino lifetime for mν = 30 eV ranges from 1022 to 1027 years as a function of the insufficiently well determined distance to resonance. The signatures of the two- or no-neutrino modes are very di…
CP properties of the leptonic sector for majorana neutrinos
1983
Abstract The leptonic sector of the electroweak theory is analyzed for massive Majorana neutrinos. For n generations, the Majorana mass lagrangian is diagonalized using the polar reduction to guarantee physical positive masses independently of the CP properties or the choice of the phases of the fields. When CP invariance holds, the CP eigenvalues of the definite mass neutrino fields are determined without commitment to a particular phase choice. For charged current interactions, we find that the observable CP violating phases can be parametrized a la Kobayashi-Maskawa for the vertec. Extra ( n − 1) relative phases of the massive neutrino fields are significant. The extra phases are observa…
Vector supersymmetry in the universal bundle
1991
Abstract We present a vector supersymmetry for Witten-type topological gauge theories, and examine its algebra in terms of a superconnection formalism. When covariant constraints on the supercurvature are chosen, a correspondence is established with the universal bundle construction of Atiyah and Singer. The vector supersymmetry represents a certain shift operator in the curvature of the universal bundle, and can be used to generate the hierarchy of observables in these theories. This formalism should lead to the construction of vector supergravity theories, and perhaps to the gravitational analogue of the universal bundle.
On the universal bundle for gravity
1991
Abstract We construct a supergravity type theory based on a superspace whose odd directions consist of a vector, together with a scalar representing a topological BRST shift symmetry. As such, the resulting theory is a theory of topological gravity. The gravitino is interpreted as a ghost field for this shift symmetry and plays the usual role of gauge field for local supersymmetry. Our construction is within the bundle of frames approach to superspace where covariant torsion constraints are analyzed, and we find that the resulting theory contains additional fields which are not present in existing theories of topological gravity. In particular, a minimal solution exists which contains a BRS…