11 research outputs found
Two-Twistor Space, Commuting Composite Minkowski Coordinates and Particle Dynamics
We employ the modification of the basic Penrose formula in twistor theory,
which allows to introduce commuting composite space-time coordinates. It
appears that in the course of such modification the internal symmetry SU(2) of
two-twistor system is broken to U(1). We consider the symplectic form on
two-twistor space, permitting to interpret its 16 real components as a
phase-space. After a suitable change of variables such a two-twistor phase
space is split into three mutually commuting parts, describing respectively the
standard relativistic phase space (8 degrees of freedom), the spin sector (6
degrees of freedom) and the canonical pair angle-charge describing the electric
charge sector (2 degrees of freedom). We obtain a geometric framework providing
a twistor-inspired 18-dimensional extended relativistic phase space
. In such a space we propose the action only with first class
constraints, describing the relativistic particle characterized by mass, spin
and electric charge.Comment: LaTeX 2e, 14 pages. To be published in the Proceedings of XIX-th Max
Born Symposium "Fundamental Interactions and Twistor-Like Methods", September
2004, American Institute of Physics, Proceedings Serie
Analysis of the electromagnetic radiation generated by a multipactor discharge occurring within a microwave passive component
International audienceMultipactoring is a non-linear phenomenon that appears in highpower microwave equipments operating under vacuum conditions and causes several undesirable effects. In this manuscript, a theoretical and experimental study of the RF spectrum radiated by a multipactor discharge, occurring within a realistic microwave component based on rectangular waveguides, is reported. The electromagnetic coupling of a multipactor current to the fundamental propagative mode of a uniform waveguide has been analyzed in the context of the microwave network theory. The discharge produced under a single-carrier RF voltage regime has been approached as a shunt current source exciting such a mode in a transmission-line gap-region. By means of a simple equivalent circuit, this model allows predicting the harmonics generated by the discharge occurring in a realistic passive waveguide component. Power spectrum radiated by a third order multipactor discharge has been measured in an E-plane silver-plated waveguide transformer, thus validating qualitatively the presented theory to simulate the noise generated by a single-carrier multipactor discharge
Superspace formulations of the (super)twistor string
The superspace formulation of the worldvolume action of twistor string models
is considered. It is shown that for the Berkovits-Siegel closed twistor string
such a formulation is provided by a N=4 twistor-like action of the tensionless
superstring. A similar inverse twistor transform of the open twistor string
model (Berkovits model) results in a dynamical system containing two copies of
the D=4, N=4 superspace coordinate functions, one left-moving and one
right-moving, that are glued by the boundary conditions.
We also discuss possible candidates for a tensionful superstring action
leading to the twistor string in the tensionless limit as well as
multidimensional counterparts of twistor strings in the framework of both
`standard' superspace and superspace enlarged by tensorial coordinates
(tensorial superspaces), which constitute a natural framework for massless
higher spin theories.Comment: Rev Tex, 13 pages, no figure
Spacetime scale-invariant super-p-brane actions on enlarged superspaces and the geometry of kappa-symmetry
We use the additional variables of suitably enlarged superspaces to write new
actions for extended objects, with kappa-symmetry, in such a way that the
tension emerges from them as an integration constant. Our actions correspond to
the spacetime scale-invariant ones previously considered by Bergshoeff et al.
once the worldvolume forms introduced there are reinterpreted in terms of
fields associated with the coordinates of the enlarged superspaces. It is shown
that the kappa-symmetry of the new actions is given by a certain type of right
local transformations of the extended superspace groups. Further, we also show
that the enlarged superspaces that allow for strictly invariant Wess-Zumino
terms also lead to strict kappa-invariance i.e., the Lagrangian itself (not
only the action) is both supersymmetry- and kappa-invariant.Comment: 23 pages, no figures. A clarifying comment and a reference adde