1,282 research outputs found
Euler Chern Simons Gravity from Lovelock Born Infeld Gravity
In the context of a gauge theoretical formulation, higher dimensional gravity
invariant under the AdS group is dimensionally reduced to Euler-Chern-Simons
gravity. The dimensional reduction procedure of Grignani-Nardelli [Phys. Lett.
B 300, 38 (1993)] is generalized so as to permit reducing D-dimensional Lanczos
Lovelock gravity to d=D-1 dimensions.Comment: 6 pages, no figures, accepted for publication in Phys. Lett.
The Chiral Condensate of Strongly Coupled QCD in the 't Hooft Limit
Using the recently proposed generalization to an arbitrary number of colors
of the strong coupling approach to lattice gauge
theories\cite{Grignani:2003uv}, we compute the chiral condensate of massless
QCD in the 't Hooft limit.Comment: 12 pages, revtex
Strongly coupled 't Hooft model on the lattice
A lattice strong coupling calculation of the spectrum and chiral condensate
of the 't Hooft model is presented. The agreement with the results of the
continuum theory is strikingly good even at the fourth order in the strong
coupling expansion.Comment: LATTICE99(Spin Models), talk presented by F. Berruto, 3 pages, LaTex,
espcrc2.st
New Penrose Limits and AdS/CFT
We find a new Penrose limit of AdS_5 x S^5 giving the maximally
supersymmetric pp-wave background with two explicit space-like isometries. This
is an important missing piece in studying the AdS/CFT correspondence in certain
subsectors. In particular whereas the Penrose limit giving one space-like
isometry is useful for the SU(2) sector of N=4 SYM, this new Penrose limit is
instead useful for studying the SU(2|3) and SU(1,2|3) sectors. In addition to
the new Penrose limit of AdS_5 x S^5 we also find a new Penrose limit of AdS_4
x CP^3.Comment: 30 page
Lattice Gauge Theories and the Heisenberg Antiferromagnetic Chain
We study the strongly coupled 2-flavor lattice Schwinger model and the
SU(2)-color QCD_2. The strong coupling limit, even with its inherent
nonuniversality, makes accurate predictions of the spectrum of the continuum
models and provides an intuitive picture of the gauge theory vacuum. The
massive excitations of the gauge model are computable in terms of spin-spin
correlators of the quantum Heisenberg antiferromagnetic spin-1/2 chain.Comment: Proceedings LATTICE99 (spin models), 3 page
Moving away from the Near-Horizon Attractor of the Extreme Kerr Force-Free Magnetosphere
We consider force-free magnetospheres around the extreme Kerr black hole. In
this case there is no known exact analytic solution to force free
electrodynamics which is stationary, axisymmetric and magnetically-dominated.
However, any stationary, axisymmetric and regular force-free magnetosphere in
extreme Kerr black hole approaches the same attractor solution in the
near-horizon extreme Kerr (NHEK) limit with null electromagnetic field. We show
that by moving away from the attractor solution in the NHEK region, one finds
magnetically-dominated solutions in the extreme Kerr black hole with finite
angular momentum outflow. This result is achieved using a perturbative analysis
up to the second order.Comment: 33 pages, 2 figures; v2: matches published version in JCA
Force-free magnetosphere attractors for near-horizon extreme and near-extreme limits of Kerr black hole
We propose a new approach to find magnetically-dominated force-free
magnetospheres around highly spinning black holes, relevant for models of
astrophysical jets. Employing the near-horizon extreme Kerr (NHEK) limit of the
Kerr black hole, any stationary, axisymmetric and regular force-free
magnetosphere reduces to the same attractor solution in the NHEK limit with
null electromagnetic field strength. We use this attractor solution as the
universal starting point for perturbing away from the NHEK region in the
extreme Kerr spacetime. We demonstrate that by going to second order in
perturbation theory, it is possible to find magnetically dominated
magnetospheres around the extreme Kerr black hole. Furthermore, we consider the
near-horizon near-extreme Kerr (near-NHEK) limit that provides access to a
different regime of highly spinning black holes. Also in this case we find a
novel force-free attractor, which can be used as the universal starting point
for a perturbative construction of force-free magnetospheres. Finally, we
discuss the relation between the NHEK and near-NHEK attractors.Comment: 5 pages, 1 figur
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