222 research outputs found
Symmetries of pp-Waves with Distributional Profile
We generalize the classification of (non-vacuum) pp-waves \cite{JEK} based on
the Killing-algebra of the space-time by admitting distribution-valued profile
functions. Our approach is based on the analysis of the (infinite-dimensional)
group of ``normal-form-preserving'' diffeomorphisms.Comment: 10 pages, latex2e, no figures, statement about the combination of
symmetry classes of impulsive waves correcte
ADM and Bondi four-momenta for the ultrarelativistic Schwarzschild black hole
We argue that it is possible to assign Bondi as well as ADM four-momentum to
the ultrarelativistic limit of the Schwarzschild black hole in agreement to
what is expected on physical grounds: The Bondi-momentum is lightlike and equal
to the ADM-momentum up to the retarded time when particle and radiation escape
to infinity and drops to zero thereafter, leaving flat space behind.Comment: Changes in the expression used for the ADM four-momentum without
altering the result, correction of some minor typing error
Canonical Formulation of pp-waves
We construct a Hamiltonian formulation for the class of plane-fronted
gravitational waves with parallel rays (pp-waves). Because of the existence of
a light-like Killing vector, the dynamics is effectively reduced to a 2+1
evolution with "time" chosen to be light-like. In spite of the vanishing action
this allows us to geometrically identify a symplectic form as well as dynamical
Hamiltonian, thus casting the system into canonical form.Comment: To appear in the "Obregon Festschrift
Generalized Symmetries of Impulsive Gravitational Waves
We generalize previous \cite{AiBa2} work on the classification of
() symmetries of plane-fronted waves with an impulsive profile. Due
to the specific form of the profile it is possible to extend the group of
normal-form-preserving diffeomorphisms to include non-smooth transformations.
This extension entails a richer structure of the symmetry algebra generated by
the (non-smooth) Killing vectors.Comment: 18 pages, latex2e, no figure
Electric Dipole Moment of a BPS Monopole
Monopole ``superpartner'' solutions are constructed by acting with finite,
broken supersymmetry transformations on a bosonic N=2 BPS monopole. The terms
beyond first order in this construction represent the backreaction of the the
fermionic zero-mode state on the other fields. Because of the quantum nature of
the fermionic zero-modes, the superpartner solution is necessarily operator
valued. We extract the electric dipole moment operator and show that it is
proportional to the fermion zero-mode angular momentum operator with a
gyroelectric ratio g=2. The magnetic quadrupole operator is shown to vanish
identically on all states. We comment on the usefulness of the monopole
superpartner solution for a study of the long-range spin dependent dynamics of
BPS monopoles.Comment: 8 pages, references and note adde
Fermionic Wigs for AdS-Schwarzschild Black Holes
We provide the metric, the gravitino fields and the gauge fields to all
orders in the fermionic zero modes for D=5 and D=4, N=2 gauged supergravity
solutions starting from non-extremal AdS--Schwarzschild black holes. We compute
the Brown-York stress--energy tensor on the boundary of AdS_5 / AdS_4 spaces
and we discuss some implications of the fermionic corrections to perfect fluid
interpretation of the boundary theory. The complete non-linear solution, which
we denote as fermionic wig, is achieved by acting with supersymmetry
transformations upon the supergravity fields and that expansion naturally
truncates at some order in the fermionic zero modes.Comment: 27 pages, Latex2e, no figures, 3 ancillary file
Head-on collision of ultrarelativistic charges
We consider the head-on collision of two opposite-charged point particles
moving at the speed of light. Starting from the field of a single charge we
derive in a first step the field generated by uniformly accelerated charge in
the limit of infinite acceleration. From this we then calculate explicitly the
burst of radiation emitted from the head-on collision of two charges and
discuss its distributional structure. The motivation for our investigation
comes from the corresponding gravitational situation where the head-on
collision of two ultrarelativistic particles (black holes) has recently aroused
renewed interest.Comment: 4 figures, uses the AMSmat
A Note on the Symmetries of the Gravitational Field of a Massless Particle
It is shown that the metric of a massless particle obtained from boosting the
Schwarzschild metric to the velocity of light, has four Killing vectors
corresponding to an E(2)\times \RR symmetry-group. This is in agreement with
the expectations based on flat-space kinematics but is in contrast to previous
statements in the literature \cite{Schueck}. Moreover, it also goes beyond the
general Jordan-Ehlers-Kundt-(JEK)-classification of gravitational pp-waves as
given in \cite{JEK}.Comment: 10pages, amslatex, TUW-94-12 and UWThPh-1994-2
Generalized asymptotic structure of the ultrarelativistic Schwarzschild black hole
We discuss the asymptotic structure of the ultrarelativistic Schwarzschild
black hole. An explicit construction for a conformal boundary both at spatial
and null infinity is given together with the corresponding expressions for the
ADM and Bondi four-momenta.Comment: uses AMS-macros, two figure
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