184 research outputs found
On a supersymmetric completion of the R-4 term in IIB supergravity
We analyze the possibility of constructing a supersymmetric invariant that
contains the term among its components as a superpotential term in type
IIB on-shell superspace. We consider a scalar superpotential, i.e. an arbitrary
holomorphic function of a chiral scalar superfield. In general, IIB superspace
does not allow for the existence of chiral superfields, but the obstruction
vanishes for a specific superfield, the dilaton superfield. This superfield
contains all fields of type IIB supergravity among its components, and its
existence is implied by the solution of the Bianchi identities. The
construction requires the existence of an appropriate chiral measure, and we
find an obstruction to the existence of such a measure. The obstruction is
closely related to the obstruction for the existence of chiral superfields and
is non-linear in the fields. These results imply that the IIB superinvariant
related to the term is not associated with a scalar chiral
superpotential
On alpha-corrections to D-brane solutions
We discuss the computation of the leading corrections to D-brane solutions due to higher derivative terms in the corresponding low energy effective action. We develop several alternative methods for analyzing the problem. In particular, we derive an effective one-dimensional action from which the field equations for spherically symmetric two-block brane solutions can be derived, show how to obtain first order equations, and discuss a few other approaches. We integrate the equations for extremal branes and obtain the corrections in terms of integrals of the evaluation of the higher derivative terms on the lowest order solution. To obtain completely explicit results one would need to know all leading higher derivative corrections which at present are not available. One of the known higher derivative terms is the R4 term, and we obtain the corrections to the D3 brane solution due to this term alone. We note, however, that (unknown at present) higher terms depending on F5 are expected to modify our result. We analyze the thermodynamics of brane solutions when such quantum corrections are present. We find that the R^4 term induces a correction to the tension and the electric potential of the D3 brane but not to its charge, and the tension is still proportional to the electric potential times the charge. In the near-horizon limit the corrected solution becomes AdS5 times S5 with the same cosmological constant as the lowest order solution but a different value of the (constant) dilaton
On alpha ' corrections to D-brane solutions
We discuss the computation of the leading corrections to D-brane solutions
due to higher derivative terms in the corresponding low energy effective
action. We develop several alternative methods for analyzing the problem. In
particular, we derive an effective one-dimensional action from which the field
equations for spherically symmetric two-block brane solutions can be derived,
show how to obtain first order equations, and discuss a few other approaches.
We integrate the equations for extremal branes and obtain the corrections in
terms of integrals of the evaluation of the higher derivative terms on the
lowest order solution. To obtain completely explicit results one would need to
know all leading higher derivative corrections which at present are not
available. One of the known higher derivative terms is the R^4 term, and we
obtain the corrections to the D3 brane solution due to this term alone. We
note, however, that (unknown at present) higher terms depending on F_5 are
expected to modify our result. We analyze the thermodynamics of brane solutions
when such quantum corrections are present. We find that the R^4 term induces a
correction to the tension and the electric potential of the D3 brane but not to
its charge, and the tension is still proportional to the electric potential
times the charge. In the near-horizon limit the corrected solution becomes
AdS_5 \times S^5 with the same cosmological constant as the lowest order
solution but a different value of the (constant) dilaton
An exploratory study of how a Korean chaebol’s learning culture facilitates customer service
This paper explains how the organizational learning concept is used by managers in a global Korean company to promote group work, information sharing and an open communication style in order to produce a high level of customer service. Previously collected data from a set of in-depth personal interviews undertaken with three senior managers in a Korean electronics company were analyzed and interpreted using the grounded theory approach, and a number of propositions are put forward. The research findings show that managers in a chaebol deploy organizational learning to identify skilled and knowledgeable staff, and improve the organization’s capability by placing emphasis on developing harmonious, mutually oriented relationships that permeate throughout the organization. Top management demand that staff identify with government economic objectives and align the organization’s strategy accordingly so that the products produced are marketable. To achieve this, the organization fosters continual interaction among managers throughout the organization’s hierarchy. The chaebol’s organizational learning model encapsulates a “corollary” (continual communication) and “tools” (cultural influence and relationship management), and manifests in a unique strategy that allows management systems to evolve naturally
Invariant Differential Operators and Characters of the AdS_4 Algebra
The aim of this paper is to apply systematically to AdS_4 some modern tools
in the representation theory of Lie algebras which are easily generalised to
the supersymmetric and quantum group settings and necessary for applications to
string theory and integrable models. Here we introduce the necessary
representations of the AdS_4 algebra and group. We give explicitly all singular
(null) vectors of the reducible AdS_4 Verma modules. These are used to obtain
the AdS_4 invariant differential operators. Using this we display a new
structure - a diagram involving four partially equivalent reducible
representations one of which contains all finite-dimensional irreps of the
AdS_4 algebra. We study in more detail the cases involving UIRs, in particular,
the Di and the Rac singletons, and the massless UIRs. In the massless case we
discover the structure of sets of 2s_0-1 conserved currents for each spin s_0
UIR, s_0=1,3/2,... All massless cases are contained in a one-parameter
subfamily of the quartet diagrams mentioned above, the parameter being the spin
s_0. Further we give the classification of the so(5,C) irreps presented in a
diagramatic way which makes easy the derivation of all character formulae. The
paper concludes with a speculation on the possible applications of the
character formulae to integrable models.Comment: 30 pages, 4 figures, TEX-harvmac with input files: amssym.def,
amssym.tex, epsf.tex; version 2 1 reference added; v3: minor corrections;
v.4: minor corrections, v.5: minor corrections to conform with version in J.
Phys. A: Math. Gen; v.6.: small correction and addition in subsections 4.1 &
4.
Orbifolding the Twistor String
The D-instanton expansion of the topological B-model on the supermanifold
CP(3|4) reproduces the perturbative expansion of N=4 Super Yang-Mills theory.
In this paper we consider orbifolds in the fermionic directions of CP(3|4).
This operation breaks the SU(4) R-symmetry group, reducing the amount of
supersymmetry of the gauge theory. As specific examples we take N=1 and N=2
orbifolds and obtain the corresponding superconformal quiver theories. We
discuss the D1 instanton expansion in this context and explicitly compute some
amplitudes.Comment: 24 pages, 8 figures; v2: minor correction
On the IR completion of geometries with hyperscaling violation
We study solutions to Einstein-Maxwell-dilaton gravity with a constant
magnetic flux which describe, in the holographic AdS/CFT framework, field
theories characterized by a dynamical critical exponent and a hyperscaling
violation exponent. Such solutions are known to be IR-incomplete due to the
presence of a running dilaton, which drives the theory towards strong coupling
in the IR, where quantum corrections become important. After introducing
generic corrections, in this note we examine the conditions for the emergence
of an AdS_2 x R^2 region close to the horizon, which provides an IR-completion
for the hyperscaling violating solutions. In the presence of these corrections,
we construct explicit numerical solutions where the geometry flows from AdS_4
in the UV to AdS_2 x R^2 in the deep IR, with an intermediate region which
exhbits both hyperscaling violation and Lifshitz scaling.We also provide
constraints on the structure of Einstein-Maxwell-dilaton theories that admit
such solutions, as well as an emergent AdS_2 x R^2 region in the infrared.Comment: Typos fixed, references added, improved discussio
Instanton Counting and Wall-Crossing for Orbifold Quivers
Noncommutative Donaldson-Thomas invariants for abelian orbifold singularities can be studied via the enumeration of instanton solutions in a six-dimensional noncommutative {Mathematical expression} gauge theory; this construction is based on the generalized McKay correspondence and identifies the instanton counting with the counting of framed representations of a quiver which is naturally associated with the geometry of the singularity. We extend these constructions to compute BPS partition functions for higher-rank refined and motivic noncommutative Donaldson-Thomas invariants in the Coulomb branch in terms of gauge theory variables and orbifold data. We introduce the notion of virtual instanton quiver associated with the natural symplectic charge lattice which governs the quantum wall-crossing behaviour of BPS states in this context. The McKay correspondence naturally connects our formalism with other approaches to wall-crossing based on quantum monodromy operators and cluster algebras
Anticancer Gene Transfer for Cancer Gene Therapy
Gene therapy vectors are among the treatments currently used to treat malignant tumors. Gene therapy vectors use a specific therapeutic transgene that causes death in cancer cells. In early attempts at gene therapy, therapeutic transgenes were driven by non-specific vectors which induced toxicity to normal cells in addition to the cancer cells. Recently, novel cancer specific viral vectors have been developed that target cancer cells leaving normal cells unharmed. Here we review such cancer specific gene therapy systems currently used in the treatment of cancer and discuss the major challenges and future directions in this field
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