3 research outputs found
Twistors, special relativity, conformal symmetry and minimal coupling - a review
An approach to special relativistic dynamics using the language of spinors
and twistors is presented. Exploiting the natural conformally invariant
symplectic structure of the twistor space, a model is constructed which
describes a relativistic massive, spinning and charged particle, minimally
coupled to an external electro-magnetic field. On the two-twistor phase space
the relativistic Hamiltonian dynamics is generated by a Poincare scalar
function obtained from the classical limit (appropriately defined by us) of the
second order, to an external electro-magnetic field minimally coupled, Dirac
operator. In the so defined relativistic classical limit there are no Grassman
variables. Besides, the arising equation that describes dynamics of the
relativistic spin differs significantly from the so called Thomas Bergman
Michel Telegdi equation.Comment: 39 pages, no figures, few erronous statements (not affecting anything
else in the papper) on page 23 delete
Stationary BPS solutions to dilaton-axion gravity
Stationary four-dimensional BPS solutions to gravity coupled bosonic theories
admitting a three-dimensional sigma-model representation on coset spaces are
interpreted as null geodesics of the target manifold equipped with a certain
number of harmonic maps. For asymptotically flat (or Taub-NUT) space-times such
geodesics can be directly parametrized in terms of charges saturating the
Bogomol'nyi-Gibbons-Hull bound, and classified according to the structure of
related coset matrices. We investigate in detail the ``dilaton-axion gravity''
with one vector field, and show that in the space of BPS solutions an classical symmetry is acting. Within the present formalism the
most general multicenter (IWP/Taub-NUT dyon) solutions are derived in a simple
way. We also discover a large new class of asymptotically flat solutions for
which the dilaton and axion charges are constrained only by the BPS bound. The
string metrics for these solutions are generically regular. Both the IWP class
and the new class contain massless solutions.Comment: 29 pages, Latex, no figures. To be published in Phys. Rev. D. Minor
grammatical and bibliographical change