339 research outputs found
The Master Field of QCD and the 'T Hooft Equation
We rewrite the action for in the light cone gauge only in terms of a
bilocal mesonic field. In this formalism the expansion can be done in a
straightforward way by a saddle point technique that determines the master
field to be identified with the vacuum expectation value of the bilocal field.
Finally we show that the equation of motion for the fluctuations around the
master field is identical with the 't Hooft meson equation.Comment: 7 pages, Latex, NORDITA-93-4
Partial N=2 --> N=1 Local Supersymmetry Breaking and Solvable Lie Algebras
Generic partial supersymmetry breaking of N=2 supergravity with zero vacuum
energy and with surviving unbroken arbitrary gauge groups is exhibited.
Specific examples are given.Comment: 5 pages, 1 LaTeX-style file, 1 TeX, 2 Postscript figures. Seminar
given at the Work-Shop on "Gauge Theories, Applied Supersymmetry and Quantum
Gravity", Imperial College, London, 5-10 July 199
Modular anomaly equation, heat kernel and S-duality in N=2 theories
We investigate epsilon-deformed N=2 superconformal gauge theories in four
dimensions, focusing on the N=2* and Nf=4 SU(2) cases. We show how the modular
anomaly equation obeyed by the deformed prepotential can be efficiently used to
derive its non-perturbative expression starting from the perturbative one. We
also show that the modular anomaly equation implies that S-duality is
implemented by means of an exact Fourier transform even for arbitrary values of
the deformation parameters, and then we argue that it is possible,
perturbatively in the deformation, to choose appropriate variables such that it
reduces to a Legendre transform.Comment: 30 pages, LeTeX2e. V2: references added, appendix B expanded, a few
typos correcte
Wrapped Magnetized Branes: Two Alternative Descriptions?
We discuss two inequivalent ways for describing magnetized D-branes wrapped N
times on a torus T^2. The first one is based on a non-abelian gauge bundle
U(N), while the second one is obtained by means of a Narain T-duality
transformation acting on a theory with non-magnetized branes. We construct in
both descriptions the boundary state and the open string vertices and show that
they give rise to different string amplitudes. In particular, the description
based on the gauge bundle has open string vertex operators with momentum
dependent Chan-Paton factors.Comment: 60 pages, LaTe
An Integrated Analytical Approach for the Characterization of Probiotic Strains in Food Supplements
Research surrounding health benefits from probiotics is becoming popular because of the increasing demand for safer products with protective and therapeutic effects. Proven benefits are species- or genus-specific; however, no certified assays are available for their characterization and quantification at the strain level in the food supplement industry. The objective of this study was to develop a strain-specific Real-time quantitative polymerase chain reaction (RT-qPCR)-based method to be implemented in routine tests for the identification and quantification of Bifidobacterium longum, Bifidobacterium animalis spp. lactis, Lactobacillus paracasei, Lactobacillus rhamnosus, Lactobacillus casei, Bifidobacterium breve, Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus helveticus, starting from a powder mixture of food supplements. The method optimization was carried out in combination with flow cytometry to compare results between the two strategies and implement the analytical workflow with the information also regarding cell viability. These assays were validated in accordance with the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) criteria using the plate count enumeration as the gold standard reference. Briefly, probiotic DNAs were extracted from two powder food supplements. Strain-specific primers targeting unique sequence regions of 16S RNA were identified and amplified by RT-qPCR. Primers were tested for specificity, sensitivity, and efficiency. Both RT-qPCR and flow-cytometry methods described in our work for the quantification and identification of Lactobacillus and Bifidobacterium strains were specific, sensitive, and precise, showing better performances with respect to the morphological colony identification. This work demonstrated that RT-qPCR can be implemented in the quality control workflow of commercial probiotic products giving more standardized and effective results regarding species discrimination
Superparticle and superstring in AdS_3 x S^3 Ramond-Ramond background in light-cone gauge
We discuss superparticle and superstring dynamics in AdS_3 x S^3 supported by
R-R 3-form background using light-cone gauge approach. Starting with the
superalgebra psu(1,1|2) + psu(1,1|2) representing the basic symmetry of this
background we find the light-cone superparticle Hamiltonian. We determine the
harmonic decomposition of light-cone superfield describing fluctuations of type
IIB supergravity fields expanded near AdS_3 x S^3 background and compute the
corresponding Kaluza-Klein spectrum. We fix the fermionic and bosonic
light-cone gauges in the covariant Green-Schwarz AdS_3 x S^3 superstring action
and find the light-cone string Hamiltonian. We also obtain a realization of the
generators of psu(1,1|2) + psu(1,1|2) in terms of the superstring 2-d fields in
the light-cone gauge.Comment: 32 pages, late
Strings in an arbitrary constant magnetic field with arbitrary constant metric and stringy form factors
We quantize the open string in an arbitrary constant magnetic field with a
non factorized metric on a torus. We then discuss carefully the vertexes which
describe the emission of dipole open strings and closed strings in the non
compact limit. Finally we compute various stringy form factors which in the
compact case induces a Kaehler and complex structure dependence and suppression
of some amplitudes with KK states.Comment: 45 page
Two dimensional QCD and abelian bosonization
A bosonized action, that reproduces the structure of the 't Hooft equation
for in the large- limit, up to regularization dependent terms, is
derived.Comment: paper revised, several signs and coefficients corrected. A comment on
regularization dependence and several references adde
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