6,298 research outputs found
Chern-Simons--Antoniadis-Savvidy forms and standard supergravity
In the context of the so called the Chern--Simons--Antoniadis--Savvidy
(ChSAS) forms, we use the methods for FDA decomposition in 1-forms to construct
a four-dimensional ChSAS supergravity action for the Maxwell superalgebra. On
the another hand, we use the Extended Cartan Homotopy Formula to find a method
that allows the separation of the ChSAS action into bulk and boundary
contributions and permits the splitting of the bulk Lagrangian into pieces that
reflect the particular subspace structure of the gauge algebra.Comment: 14 page
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.
Standard General Relativity from Chern-Simons Gravity
Chern-Simons models for gravity are interesting because they provide with a
truly gauge-invariant action principle in the fiber-bundle sense. So far, their
main drawback has largely been the perceived remoteness from standard General
Relativity, based on the presence of higher powers of the curvature in the
Lagrangian (except, remarkably, for three-dimensional spacetime). Here we
report on a simple model that suggests a mechanism by which standard General
Relativity in five-dimensional spacetime may indeed emerge at a special
critical point in the space of couplings, where additional degrees of freedom
and corresponding "anomalous" Gauss-Bonnet constraints drop out from the
Chern-Simons action. To achieve this result, both the Lie algebra g and the
symmetric g-invariant tensor that define the Chern-Simons Lagrangian are
constructed by means of the Lie algebra S-expansion method with a suitable
finite abelian semigroup S. The results are generalized to arbitrary odd
dimensions, and the possible extension to the case of eleven-dimensional
supergravity is briefly discussed.Comment: 6 pages, no figures; v2: published versio
Medium Modification of the Jet Properties
In the case that a dense medium is created in a heavy ions collision,
high-E_t jets are expected to be broadened by medium-modified gluon emission.
This broadening is directly related, through geometry, to the energy loss
measured in inclusive high-p_t particle suppression. We present here the
modifications of jet observables due to the presence of a medium for the case
of azimuthal jet energy distributions and k_t-differential multiplicities
inside the jets.Comment: 4 pages, 3 postscript figures. Proceedings for Quark Matter 200
Minimal AdS-Lorentz supergravity in three-dimensions
The AdS-Lorentz superalgebra is studied and its relationship
to semigroup expansion developed. Using this mathematical tool, the invariant
tensors and Casimir operators are found. In terms of these invariants, a
three-dimensionnal Chern--Simons supergravity action with AdS-Lorentz symmetry
is constructed. The Killing spinors for a BTZ black-hole like solution of the
theory are discussed.Comment: 18 pages, matches published versio
Superposition of a static perfect fluid and a radial elecric field
We obtain a two-parameter set of solutions, which represents a spherically
symmetric space-time with a superposition of a neutral fluid and an electric
field. The electromagnetic four-potential of this Einstein-Maxwell space-time
is taken in the form A=(q/n)(r^n)dt, when n=/0 and A=q*ln(r)dt, when n=0 (where
q and n are arbitrary constants)Comment: 12 pages, RevTeX, no figure
Einstein-Chern-Simons equations on the 3-brane world
In this article it is studied the 3-brane world in the context of
five-dimensional Einstein-Chern-Simons gravity. We started by considering
Israel's junction condition for AdS-Chern-Simons gravity. Using the S-expansion
procedure, we mapped the AdS-Chern-Simons junction conditions to
Einstein-Chern-Simons gravity, allowing us to derive effective four-dimensional
Einstein-Chern-Simons field equations
Measuring The Collective Flow With Jets
In nucleus--nucleus collisions, high-pT partons interact with a dense medium,
which possesses strong collective flow components. Here, we demonstrate that
the resulting medium-induced gluon radiation does not depend solely on the
energy density of the medium, but also on the collective flow. Both components
cannot be disentangled on the basis of leading hadron spectra, but the
measurement of particle production associated to high-pT trigger particles,
jet-like correlations and jets, allows for their independent characterization.
In particular, we show that flow effects lead to a characteristic breaking of
the rotational symmetry of the average jet energy and jet multiplicity
distribution in the -plane. We argue that data on the
medium-induced broadening of jet-like particle correlations in Au+Au collisions
at RHIC provide a first evidence for a significant distortion of parton
fragmentation due to the longitudinal collective flow.Comment: 4 pages, Latex, 3 eps-figure
Dual Formulation of the Lie Algebra S-expansion Procedure
The expansion of a Lie algebra entails finding a new, bigger algebra G,
through a series of well-defined steps, from an original Lie algebra g. One
incarnation of the method, the so-called S-expansion, involves the use of a
finite abelian semigroup S to accomplish this task. In this paper we put
forward a dual formulation of the S-expansion method which is based on the dual
picture of a Lie algebra given by the Maurer-Cartan forms. The dual version of
the method is useful in finding a generalization to the case of a gauge free
differential algebra, which in turn is relevant for physical applications in,
e.g., Supergravity. It also sheds new light on the puzzling relation between
two Chern-Simons Lagrangians for gravity in 2+1 dimensions, namely the
Einstein-Hilbert Lagrangian and the one for the so-called "exotic gravity".Comment: 12 pages, no figure
- …