51,766 research outputs found
Realizations of Conformal and Heisenberg Algebras in PP-wave-CFT Correspondence
We elaborate on the symmetry breaking pattern involved in the Penrose limit
of spacetimes and the corresponding limit of the CFT
dual. For d=2 we examine in detail how the symmetries contract to products of
rotation and Heisenberg algebras, both from the bulk and CFT points of view.
Using a free field realization of these algebras acting on products of
elementary fields of the CFT with SO(2) R charge +1, we show that this process
of contraction restricts all the fields to a few low angular momentum modes and
ensures that the field with R charge -1 does not appear. This provides an
understanding of several important aspects of the proposal of Berenstein,
Maldacena and Nastase. We also indicate how the contraction can be performed on
correlation functions.Comment: 24 pages, LaTe
The closed-string 3-loop amplitude and S-duality
The low-energy limit of the four-point 3-loop amplitude (including its
overall coefficient) is computed in both type IIA and IIB superstring theories
using the pure spinor formalism. The result is shown to agree with the
prediction of the coefficient for the type IIB interaction made by
Green and Vanhove based on S-duality considerations.Comment: 26 pages, harvmac. v3: factor of 3 in section 3.3 corrected, updated
abstract and dropped Z_3-symmetry argumen
Generalized CoK\"ahler Geometry and an Application to Generalized K\"ahler Structures
In this paper we define the notion of a generalized coK\"ahler structure and
prove that the product of generalized contact metric
manifolds , , where
is endowed with the product generalized complex structure induced from
and , is generalized K\"ahler if and only if are generalized coK\"ahler structures. We also prove that
products of generalized coK\"ahler and generalized K\"ahler manifolds admit a
generalized coK\"ahler structure. We use these product constructions to give
nontrivial examples of generalized coK\"ahler structures. Finally, we show the
analogs of these theorems hold in the setting of twisted generalized
geometries. We use these theorems to construct new examples of twisted
generalized K\"ahler structures on manifolds that do not admit a classical
K\"ahler structure and we give examples of twisted generalized coK\"ahler
structures on manifolds which do not admit a classical coK\"ahler structure.Comment: Final print version. To appear in Journal of Geometry and Physic
Small unmanned airborne systems to support oil and gas pipeline monitoring and mapping
Acknowledgments We thank Johan Havelaar, Aeryon Labs Inc., AeronVironment Inc. and Aeronautics Inc. for kindly permitting the use of materials in Fig. 1.Peer reviewedPublisher PD
Parabolic bundles and representations of the fundamental group
Let X be as smooth complex projective variety with Neron-Severi group
isomorphic to Z, and D an irreducible divisor with normal crossing
singularities. Assume r is equal to 2 or 3. We prove that if the fundamental
group of X doesn't have irreducible PU(r) representations, then the fundamental
group of X-D doesn't have irreducible U(r) representations. The proof uses the
non-existence of certain stable parabolic bundles. We also obtain a similar
result for GL(2) when D is smooth and X is a complex surface.Comment: 13 pages, 1 figure, LaTeX2
Light meson resonances from unitarized Chiral Perturbation Theory
We report on our recent progress in the generation of resonant behavior in
unitarized meson-meson scattering amplitudes obtained from Chiral Perturbation
Theory. These amplitudes provide simultaneously a remarkable description of the
resonance region up to 1.2 GeV as well as the low energy region, since they
respect the chiral symmetry expansion. By studying the position of the poles in
these amplitudes it is possible to determine the mass and width of the
associated resonances, as well as to get a hint on possible classification
schemes, that could be of interest for the spectroscopy of the scalar sector.Comment: Invited talk to the II International Workshop on Hadron Physics &
Effective Theories of Low Energy QCD. 25-29 September 2002. Coimbra. Portuga
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