197 research outputs found
Poisson-Lie T-plurality of three-dimensional conformally invariant sigma models II: Nondiagonal metrics and dilaton puzzle
We look for 3-dimensional Poisson-Lie dualizable sigma models that satisfy
the vanishing beta-function equations with constant dilaton field. Using the
Poisson-Lie T-plurality we then construct 3-dimensional sigma models that
correspond to various decompositions of Drinfeld double. Models with nontrivial
dilaton field may appear. It turns out that for ``traceless'' dual algebras
they satisfy the vanishing beta-function equations as well.
In certain cases the dilaton cannot be defined in some of the dual models. We
provide an explanation why this happens and give criteria predicting when it
happens.Comment: 24 pages, the published version; changes compared to v1: typos
corrected, conclusions extended, added reference
ADE-Quiver Theories and Mirror Symmetry
We show that the Higgs branch of a four-dimensional Yang-Mills theory, with
gauge and matter content summarised by an ADE quiver diagram, is identical to
the generalised Coulomb branch of a four-dimensional superconformal strongly
coupled gauge theory with ADE global symmetry. This equivalence suggests the
existence of a mirror symmetry between the quiver theories and the strongly
coupled theories.Comment: 8 pages, 4 figures. Talk delivered by UL at D.V. Volkov Memorial
Conference, July 25-29, 2000, Kharkov, to be published in the proceeding
Worldsheet boundary conditions in Poisson-Lie T-duality
We apply canonical Poisson-Lie T-duality transformations to bosonic open
string worldsheet boundary conditions, showing that the form of these
conditions is invariant at the classical level, and therefore they are
compatible with Poisson-Lie T-duality. In particular the conditions for
conformal invariance are automatically preserved, rendering also the dual model
conformal. The boundary conditions are defined in terms of a gluing matrix
which encodes the properties of D-branes, and we derive the duality map for
this matrix. We demonstrate explicitly the implications of this map for
D-branes in two non-Abelian Drinfel'd doubles.Comment: 20 pages, Latex; v2: typos and wording corrected, references added;
v3: three-dimensional example added, reference added, discussion clarified,
published versio
Topological Sigma Models with H-Flux
We investigate the topological theory obtained by twisting the N=(2,2)
supersymmetric nonlinear sigma model with target a bihermitian space with
torsion. For the special case in which the two complex structures commute, we
show that the action is a Q-exact term plus a quasi-topological term. The
quasi-topological term is locally given by a closed two-form which corresponds
to a flat gerbe-connection and generalises the usual topological term of the
A-model. Exponentiating it gives a Wilson surface, which can be regarded as a
generalization of a Wilson line. This makes the quantum theory globally
well-defined.Comment: 16 pages, Appendix added, the version to appear in JHE
String cosmology from Poisson-Lie T-dual sigma models on supermanifolds
We generalize the formulation of Poisson-Lie T-dual sigma models on manifolds
to supermanifolds. In this respect, we formulate 1+1 dimensional string
cosmological models on the Lie supergroup C^3 and its dual (A_1,1 +
2A)^0_(1,0,0), which are coupled to two fermionic fields. Then, we solve the
equations of motion of the models and show that there is a essential
singularity for the metric of the original model and its dual.Comment: 17 pages, Appendix and three references have adde
Quantum equivalence in Poisson-Lie T-duality
We prove that, general \s-models related by Poisson-Lie T-duality are
quantum equivalent under one-loop renormalization group flow. We reveal general
properties of the flows, we study the associated generalized coset models and
provide explicit examples.Comment: 16 page
Brane Boxes: Bending and Beta Functions
We study the type IIB brane box configurations recently introduced by Hanany
and Zaffaroni. We show that even at finite string coupling, one can construct
smooth configurations of branes with fairly arbitrary gauge and flavor
structure. Limiting our attention to the better understood case where NS-branes
do not intersect over a four dimensional surface gives some restrictions on the
theories, but still permits many examples, both anomalous and non-anomalous. We
give several explicit examples of such configurations and discuss what
constraints can be imposed on brane-box theories from bending considerations.
We also discuss the relation between brane bending and beta-functions for
brane-box configurations.Comment: latex, 18 pages, 8 figure
Predictors of linkage to care following community-based HIV counseling and testing in rural Kenya
Despite innovations in HIV counseling and testing (HCT), important gaps remain in understanding linkage to care. We followed a cohort diagnosed with HIV through a community-based HCT campaign that trained persons living with HIV/AIDS (PLHA) as navigators. Individual, interpersonal, and institutional predictors of linkage were assessed using survival analysis of self-reported time to enrollment. Of 483 persons consenting to follow-up, 305 (63.2%) enrolled in HIV care within 3 months. Proportions linking to care were similar across sexes, barring a sub-sample of men aged 18â25 years who were highly unlikely to enroll. Men were more likely to enroll if they had disclosed to their spouse, and women if they had disclosed to family. Women who anticipated violence or relationship breakup were less likely to link to care. Enrolment rates were significantly higher among participants receiving a PLHA visit, suggesting that a navigator approach may improve linkage from community-based HCT campaigns.Vestergaard Frandse
T-Duality and Penrose limits of spatially homogeneous and inhomogeneous cosmologies
Penrose limits of inhomogeneous cosmologies admitting two abelian Killing
vectors and their abelian T-duals are found in general. The wave profiles of
the resulting plane waves are given for particular solutions. Abelian and
non-abelian T-duality are used as solution generating techniques. Furthermore,
it is found that unlike in the case of abelian T-duality, non-abelian T-duality
and taking the Penrose limit are not commutative procedures.Comment: 16 pages, 4 figures. Discussion on non-abelian T-duality expande
Orbifolds, Penrose Limits and Supersymmetry Enhancement
We consider supersymmetric PP-wave limits for different N=1 orbifold
geometries of the five sphere S^5 and the five dimensional Einstein manifold
T^{1,1}. As there are several interesting ways to take the Penrose limits, the
PP-wave geometry can be either maximal supersymmetric N=4 or half-maximal
supersymmetric N=2. We discuss in detail the cases AdS_5 x S^5/Z_3, AdS_5 x
S^5/(Z_m x Z_n) and AdS_5 x T^{1,1}/(\Z_m \times \Z_n) and we identify the
gauge invariant operators which correspond to stringy excitations for the
different limits.Comment: 22 pages, Latex,v2:additional comments in section 2,references
update
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