342 research outputs found
On direct and crossed channel asymptotics of four-point functions in AdS/CFT correspondence
We analyse the leading logarithmic singularities in direct and crossed
channel limit of the four-point functions in dilaton-axion sector of type IIB
supergravity on in AdS/CFT correspondence. Logarithms do not cancel
in the full correlator in both channels.Comment: Revised version, typos corrected, 9 pages, no figure
Liquid chromatography-tandem mass spectrometry - Application in the clinical laboratory
This review provides a concise survey of liquid chromatography tandem mass spectrometry (LCTMS) as an emerging technology in clinical chemistry. The combination of two mass spectrometers with an interposed collision cell characterizes LCTMS as an analytical technology on its own and not just as a more specific detector for HPLC compared with conventional techniques. In LCTMS, liquid chromatography is rather used for sample preparation but not for complete resolution of compounds of interest. The instrument technology of LCTMS is complex and comparatively expensive; however, in routine use, methods are far more rugged compared to conventional chromatographic techniques and enable highthroughput analyses with very limited manual handling steps. Moreover, compared to both gas chromatographymass spectrometry (GCMS) and conventional HPLC techniques, LCTMS is substantially more versatile with respect to the spectrum of analyzable compounds. For these reasons it is likely that LCTMS will gain far more widespread use in the clinical laboratory than HPLC and GCMS ever did. In this article, the key features of LCTMS are described, method development is explained, typical fields of application are discussed, and personal experiences are related
Logarithmic conformal field theories and AdS correspondence
We generalize the Maldacena correspondence to the logarithmic conformal field
theories. We study the correspondence between field theories in
(d+1)-dimensional AdS space and the d-dimensional logarithmic conformal field
theories in the boundary of . Using this correspondence, we get the
n-point functions of the corresponding logarithmic conformal field theory in
d-dimensions.Comment: 10 pages, LaTeX. A paragraph was added. To appear in Int. J. Mod.
Phys.
Holography for fermions
The holographic interpretation is a useful tool to describe 5D field theories
in a 4D language. In particular it allows one to relate 5D AdS theories with 4D
CFTs. We elaborate on the 5D/4D dictionary for the case of fermions in AdS
with boundaries. This dictionary is quite useful to address phenomenological
issues in a very simple manner, as we show by giving some examples.Comment: 22 pages, 2 figures; v2: minor corrections, references adde
Quarkonium from the Fifth Dimension
Adding fundamental matter of mass m_Q to N=4 Yang Mills theory, we study
quarkonium, and "generalized quarkonium" containing light adjoint particles. At
large 't Hooft coupling the states of spin<=1 are anomalously light (Kruczenski
et al., hep-th/0304032). We examine their form factors, and show these hadrons
are unlike any known in QCD. By a traditional yardstick they appear infinite in
size (as with strings in flat space) but we show that this is a failure of the
yardstick. All of the hadrons are actually of finite size ~ \sqrt{g^2N}/m_Q,
regardless of their radial excitation level and of how many valence adjoint
particles they contain. Certain form factors for spin-1 quarkonia vanish in the
large-g^2N limit; thus these hadrons resemble neither the observed J/Psi
quarkonium states nor rho mesons.Comment: 57 pages, LaTeX, 5 figure
Gravitino Propagator in anti de Sitter space
We construct the gauge invariant part of the propagator for the massless
gravitino in AdS(d+1) by coupling it to a conserved current. We also derive the
propagator for the massive gravitino.Comment: 24 pages; LaTe
Linearized Gravity in Isotropic Coordinates in the Brane World
We solve the Einstein equations in the Randall-Sundrum framework using an
isotropic ansatz for the metric and obtain an exact expression to first order
in the gravitational coupling. The solution is free from metric singularities
away from the source and it satisfies the Israel matching condition on a
straight brane. At distances far away from the source and on the physical brane
this solution coincides with the 4-D Schwarzschild metric in isotropic
coordinates. Furthermore we show that the extension of the standard
Schwarzschild horizon in the bulk is tubular for any diagonal form of the
metric while there is no restriction for the extension of the Schwarzschild
horizon in isotropic coordinates.Comment: 13 pages, plain Te
Holographic Normal Ordering and Multi-particle States in the AdS/CFT Correspondence
The general correlator of composite operators of N=4 supersymmetric gauge
field theory is divergent. We introduce a means for renormalizing these
correlators by adding a boundary theory on the AdS space correcting for the
divergences. Such renormalizations are not equivalent to the standard normal
ordering of current algebras in two dimensions. The correlators contain contact
terms that contribute to the OPE; we relate them diagrammatically to
correlation functions of compound composite operators dual to multi-particle
states.Comment: 18 pages, one equation corr., further comments and refs. adde
Recovery of the Schwarzschild Metric in Theories with Localized Gravity Beyond Linear Order
We solve the Einstein equations in the Randall-Sundrum framework with a
static, spherically symmetric matter distribution on the {\it physical brane}
and obtain an approximate expression for the gravitational field outside the
source to second order in the gravitational coupling. This expression when
confined on the {\it physical brane} coincides with the standard form of the
Schwarzschild metric. Therefore, the Randall-Sundrum scenario is consistent
with the Mercury precession test of General Relativity.Comment: 17 pages, plain Tex, references added, typos correcte
Bias-induced threshold voltages shifts in thin-film organic transistors
An investigation into the stability of metal-insulator-semiconductor (MIS) transistors based on alpha-sexithiophene is reported. In particular, the kinetics of the threshold voltage shift upon application of a gate bias has been determined. The kinetics follow stretched-hyperbola-type behavior, in agreement with the formalism developed to explain metastability in amorphous-silicon thin-film transistors. Using this model, quantification of device stability is possible. Temperature-dependent measurements show that there are two processes involved in the threshold voltage shift, one occurring at Tapproximate to220 K and the other at Tapproximate to300 K. The latter process is found to be sample dependent. This suggests a relation between device stability and processing parameters. (C) 2004 American Institute of Physics
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