2,034 research outputs found
N=1 Super QCD and Fractional Branes
We show how to get the one-loop beta function and the chiral anomaly of N=1
Super QCD from a stack of fractional N D3-branes localized inside the
world-volume of 2M fractional D7-branes on the orbifold C^3/(Z_2 x Z_2). They
are obtained by analyzing the classical supergravity background generated by
such a brane configuration, in the spirit of the gauge/gravity correspondence.Comment: 4 pages, LaTeX. Talk given at the IXth International Symposium on
Particles, Strings and Cosmology PASCOS '03, Mumbai-India, January 3-8 2003.
To appear in a special issue of Praman
Consistent Off-Shell Tree String Amplitudes
We give a construction of off-shell tree bosonic string amplitudes, based on
the operatorial formalism of the -string Vertex, with three external
massless states both for open and closed strings by requiring their being
projective invariant. In particular our prescription leads, in the low-energy
limit, to the three-gluon amplitude in the usual covariant gauge.Comment: 12 pages. Introductory and final parts modified in order to make them
more clear. Cosmetic changes in formulae (13) and (14). Some misprints
correcte
N=2 four-dimensional gauge theories from fractional branes
This is a pedagogical and extended version of the results published in Refs.
[1,2] and presented by the authors in various talks during the last year. We
discuss the type II D-branes (both regular and fractional) of the orbifold
R^{1,5}*R^4/Z_2, we determine their corresponding supergravity solution and
show how this can be used to study the properties of N=2 super Yang-Mills.
Supergravity is able to reproduce the perturbative moduli space of the gauge
theory, while it does not encode the non-perturbative corrections. The short
distance region of space-time, which corresponds to the infrared region of the
gauge theory, is excised by an enhancon mechanism, and more states should be
included in the low energy effective action in order to enter inside the
enhancon and recover the instanton corrections. (To be published on a Memorial
Volume commemorating Michael Marinov)Comment: 44 pages, AMS-LaTeX, no figure
Prescriptions for Off-Shell Bosonic String Amplitudes
We give, in the framework of the bosonic string theory, simple prescriptions
for computing, at tree and one-loop levels, off-shell string amplitudes for
open and closed string massless states. In particular we obtain a tree
amplitude for three open strings that in the field theory limit coincides with
the three-gluon vertex in the usual covariant gauge and two-string one-loop
amplitudes satisfying the property of transversality.Comment: 11 pages, LaTeX, to appear in the proceedings of the workshop
"Quantum Aspects of Gauge Theories, Supersymmetry and Unification", Corfu
(Greece), 20-26 September 1998. Eq. (12) and numerical factors in eqs. (13)
and (16) corrected; some minor changes and references adde
Non-perturbative effective model for the Higgs sector of the Standard Model
A non-perturbative effective model is derived for the Higgs sector of the
standard model, described by a simple scalar theory. The renormalized couplings
are determined by the derivatives of the Gaussian Effective Potential that are
known to be the sum of infinite bubble graphs contributing to the vertex
functions. A good agreement has been found with strong coupling lattice
simulations when a comparison can be made
Fractional Branes and N=1 Gauge Theories
We discuss fractional D3-branes on the orbifold C^3/Z_2*Z_2. We study the
open and the closed string spectrum on this orbifold. The corresponding N=1
theory on the brane has, generically, a U(N_1)*U(N_2)*U(N_3)*U(N_4) gauge group
with matter in the bifundamental. In particular, when only one type of brane is
present, one obtains pure N=1 Yang-Mills. We study the coupling of the branes
to the bulk fields and present the corresponding supergravity solution, valid
at large distances. By using a probe analysis, we are able to obtain the
Wilsonian beta-function for those gauge theories that possess some chiral
multiplet. Although, due to the lack of moduli, the probe technique is not
directly applicable to the case of pure N=1 Yang-Mills, we point out that the
same formula gives the correct result also for this case.Comment: 21 pages, AMS-LaTeX, v2: references added and typos correcte
Gauge theory renormalizations from the open bosonic string
We present a unified point of view on the different methods available in the
literature to extract gauge theory renormalization constants from the
low-energy limit of string theory. The Bern-Kosower method, based on an
off-shell continuation of string theory amplitudes, and the construction of
low-energy string theory effective actions for gauge particles, can both be
understood in terms of strings interacting with background gauge fields, and
thus reproduce, in the low-energy limit, the field theory results of the
background field method. We present in particular a consistent off-shell
continuation of the one-loop gluon amplitudes in the open bosonic string that
reproduces exactly the results of the background field method in the Feynman
gauge.Comment: 14 pages, latex, no figure
Printable Thin-Film Sol-Gel Lead Zirconate Titanate (PZT) Deposition Using NanoJet and Inkjet Printing Methods
Lead zirconate titanate (PZT) sub-5µm thin-films deposited using NanoJet and inkjet printing techniques will be presented. PZT, a perovskite ferroelectric ceramic, possesses both electrical and mechanical properties making it well suited for sensor and actuator applications. Large-scale and additive manufacturing of PZT deposition is currently unobtainable. A novel PZT sol-gel, therefore, comprised of an alkoxide mixture, was adapted for printing. Polyethylene glycol (PEG, 200MW) was discovered to be a superior film forming aid to the PZT sol-gel composite. PEG was added to the PZT composite to prevent film cracking upon gelation and thermal sintering. A powder-based sample of the PZT sol-gel was characterized using Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS), and Raman Spectroscopy. The Raman spectra displayed wavelength peaks around 200cm-1, 400cm-1, and 800cm-1 which indicated the desired 52/48 PZT molar ratio composite. The PZT sol-gel was printed into a thin-film using NanoJet and inkjet printing onto a cleaned stainless-steel substrate. The thin-film was thermally sintered at 700oC, and quenched in liquid nitrogen, to produce a defect-free thick film. The sub-five micron thick PZT films exhibited ferroelectric properties. This work begins to show a forward pathway for the larger scale manufacturing of device applications, such as concussion sensors, pressure sensors, and aerospace products
Anomalies and Tadpoles in Open/Closed String Duality
We discuss the role played by the divergences appearing in the interaction
between a fractional D3 brane dressed with an SU(N) gauge field and a stack of
N fractional D3 branes on the orbifolds C^2/Z_2 and C^3/(Z_2 x Z_2). In
particular we show that the logarithmic divergences in the closed string
channel, interpreted as due to twisted massless tadpoles, are mapped, under
open/closed string duality, in the logarithmic ones in the open string channel,
due to the massless states circulating in the annulus diagram and corresponding
to the one-loop divergences that one finds in the gauge theory living in the
world volume of the brane. This result provides a quantitative evidence of why
the chiral and scale anomalies of the supersymmetric and non conformal gauge
theories supported by the world volume of the branes can be inferred from
supergravity calculations.Comment: LaTeX, 8 pages. Contribution to the proceedings of the workshop of
the RTN Network "The quantum structure of space-time and the geometric nature
of fundamental interactions", Copenhagen, September 200
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