3 research outputs found
On the applicability of constrained symplectic integrators in general relativity
The purpose of this note is to point out that a naive application of
symplectic integration schemes for Hamiltonian systems with constraints such as
SHAKE or RATTLE which preserve holonomic constraints encounters difficulties
when applied to the numerical treatment of the equations of general relativity.Comment: 13 pages, change the title to be more descriptive, typos corrected,
added referenc
Asymptotic generators of fermionic charges and boundary conditions preserving supersymmetry
We use a covariant phase space formalism to give a general prescription for
defining Hamiltonian generators of bosonic and fermionic symmetries in
diffeomorphism invariant theories, such as supergravities. A simple and general
criterion is derived for a choice of boundary condition to lead to conserved
generators of the symmetries on the phase space. In particular, this provides a
criterion for the preservation of supersymmetries. For bosonic symmetries
corresponding to diffeomorphisms, our prescription coincides with the method of
Wald et al.
We then illustrate these methods in the case of certain supergravity theories
in . In minimal AdS supergravity, the boundary conditions such that the
supercharges exist as Hamiltonian generators of supersymmetry transformations
are unique within the usual framework in which the boundary metric is fixed. In
extended AdS supergravity, or more generally in the presence
of chiral matter superfields, we find that there exist many boundary conditions
preserving supersymmetry for which corresponding generators
exist. These choices are shown to correspond to a choice of certain arbitrary
boundary ``superpotentials,'' for suitably defined ``boundary superfields.'' We
also derive corresponding formulae for the conserved bosonic charges, such as
energy, in those theories, and we argue that energy is always positive, for any
supersymmetry-preserving boundary conditions. We finally comment on the
relevance and interpretation of our results within the AdS-CFT correspondence.Comment: 45 pages, Latex, no figures, v2: extended discussion of positive
energy theorem and explicit form of fermionic generators, references adde