85 research outputs found
Delaminated areas beneath organic coating: A local electrochemical impedance approach
Local electrochemical impedance mapping was used to investigate delamination phenomena at the steel/epoxy-vinyl primer interface. The delamination occurred from an artificial defect(cutter scribing) and from ageing in a salt spray chamber. The samples were taken from the salt spray chamber after 20, 30 and 50 days of exposure. To observe delamination after ageing, the corrosion product layers were removed by a cathodic polarization at â1.5 V/SCE for 4 h. A non-aged reference sample was tested for comparison. Mapping was performed at 5 kHz. Initiation and propagation of the delamination were clearly observed. The delaminated surface areas measured by visual observations after the removal of the coating were lower than those determined by local electrochemical impedance mapping. The delamination mechanisms were discussed with reference to literature data
N=1 Super Yang-Mills Domain Walls via The Extended Veneziano Yankielowicz Theory
We investigate the vacuum structure of pure SU(N) N=1 super Yang-Mills. The
theory is expected to possess N vacua with associated domain walls. We show
that the newly extended version of the low energy effective Lagrangian for
super Yang-Mills supports the BPS domain wall solutions associated with any two
vacua aligned with the origin of the moduli space. For the two color theory the
domain wall analysis is complete. We also find new non BPS domain wall
solutions connecting any two vacua of the underling SU(N) super Yang-Mills
theory not necessarely aligned. When two vacua are aligned with the origin of
the moduli space these solutions are the BPS ones. We also discuss the generic
BPS domain wall solutions connecting any two vacua within the extended
Veneziano-Yankielowicz theory.Comment: 25 pages, 5 figures plain Late
Extending the Veneziano-Yankielowicz Effective Theory
We extend the Veneziano Yankielowicz (VY) effective theory in order to
account for ordinary glueball states. We propose a new form of the
superpotential including a chiral superfield for the glueball degrees of
freedom. When integrating it ``out'' we obtain the VY superpotential while the
N vacua of the theory naturally emerge. This fact has a counterpart in the
Dijkgraaf and Vafa geometric approach. We suggest a link of the new field with
the underlying degrees of freedom which allows us to integrate it ``in'' the VY
theory. We finally break supersymmetry by adding a gluino mass and show that
the Kahler independent part of the ``potential'' has the same form of the
ordinary Yang-Mills glueball effective potential.Comment: LaTeX, 20 page
A note on the dual of N=1 super Yang-Mills theory
We refine the dictionary of the gauge/gravity correspondence realizing N=1
super Yang-Mills by means of D5-branes wrapped on a resolved Calabi-Yau space.
This is done by fixing an ambiguity on the correct interpretation of the
holographic dual of the running gauge coupling and amounts to identify a
specific 2-cycle in the dual ten-dimensional supergravity background. In doing
so, we also discuss the role played in this context by gauge transformations in
the relevant seven-dimensional gauged supergravity. While all nice properties
of the duality are maintained, this modification of the dictionary has some
interesting physical consequences and solves a puzzle recently raised in the
literature. In this refined framework, it is also straightforward to see how
the correspondence naturally realizes a geometric transition.Comment: 11 pages, latex; minor changes and typos correcte
Gauge theories from wrapped and fractional branes
We compare two applications of the gauge/gravity correspondence to a non
conformal gauge theory, based respectively on the study of D-branes wrapped on
supersymmetric cycles and of fractional D-branes on orbifolds. We study two
brane systems whose geometry is dual to N=4, D=2+1 super Yang-Mills theory, the
first one describing D4-branes wrapped on a two-sphere inside a Calabi-Yau
two-fold and the second one corresponding to a system of fractional
D2/D6-branes on the orbifold R^4/Z_2. By probing both geometries we recover the
exact perturbative running coupling constant and metric on the moduli space of
the gauge theory. We also find a general expression for the running coupling
constant of the gauge theory in terms of the "stringy volume" of the two-cycle
which is involved in both types of brane systems.Comment: AMS-LaTeX, 35 pages, no figures. Minor typos corrected, version to
appear in NP
Fractional branes and the gravity dual of partial supersymmetry breaking
In type IIB string theory, we consider fractional D3-branes in the orbifold
background dual to four-dimensional N=2 supersymmetric Yang-Mills theory. We
find the gravitational dual description of the generation of a non-trivial
field theory potential on the Coulomb branch. When the orbifold singularity is
softened to the smooth Eguchi-Hanson space, the resulting potential induces
spontaneous partial supersymmetry breaking. We study the N=1 theory arising in
those vacua and we see how the resolved conifold geometry emerges in this way.
It will be natural to identify the size of the blown-up two-cycle of that
geometry with the inverse mass of the adjoint chiral scalar. We finally discuss
the issue of geometric transition in this context.Comment: 20 pages, no figures, references adde
Veneziano-Yankielowicz Superpotential Terms in N=1 SUSY Gauge Theories
The Veneziano-Yankielowicz glueball superpotential for an arbitrary N=1 SUSY
pure gauge theory with classical gauge group is derived using an approach
following recent work of Dijkgraaf, Vafa and others. These non-perturbative
terms, which had hitherto been included by hand in the above approach, are thus
seen to arise naturally, and the approach is rendered self-contained. By
minimising the glueball superpotential for theories with fundamental matter
added, the expected vacuum structure with gaugino condensation and chiral
symmetry breaking is obtained. Various possible extensions are also discussed.Comment: 9 page
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