3,155 research outputs found
Remarks on the analytic structure of supersymmetric effective actions
We study the effective superpotential of N=1 supersymmetric gauge theories
with a mass gap, whose analytic properties are encoded in an algebraic curve.
We propose that the degree of the curve equals the number of semiclassical
branches of the gauge theory. This is true for supersymmetric QCD with one
adjoint and polynomial superpotential, where the two sheets of its
hyperelliptic curve correspond to the gauge theory pseudoconfining and higgs
branches. We verify this proposal in the new case of supersymmetric QCD with
two adjoints and superpotential V(X)+XY^2, which is the confining phase
deformation of the D_{n+2} SCFT. This theory has three kinds of classical vacua
and its curve is cubic. Each of the three sheets of the curve corresponds to
one of the three semiclassical branches of the gauge theory. We show that one
can continuously interpolate between these branches by varying the couplings
along the moduli space.Comment: 49 pages, 3 figures, harvmac; typos correcte
Industrial policies in Europe: an introduction
As guest editors of this Special Issue of PE/JEP we have selected a small number of rather detailed assessment of contemporary history of domestic industrial policies in the international context. The four papers included in this Special Issue can be seen as three case studies of
“sectoral” innovation policies (broad band, wind energy, biotechnology) with a strong emphasis on country institutional features and policy instruments, together with one “horizontal” case of industrial policy in a specific country context (innovative startups in Italy).
The heterogeneous theoretical background (industrial organization, evolutionary theory of the
firm, economics of innovation, development) provides a somewhat unifying hidden thread of
these case studies, without becoming a subject of analysis per se. This approach has been our
intentional editorial choice and we are fully aware of its limitations.
After very short non-technical summaries of the four papers (Section 1) we try to present a
rather synthetic assessment of our personal views (largely shared among us even with partial
minor disagreements) about the increasingly hot debate on the nature, limitations and desirable
perspectives of industrial policy today. We argue for a non-ideological forward-looking role of
governments as active players in helping domestic entrepreneurial resources not only to fully
exploit inherited comparative advantages but also to face structural uncertainties and discover
own potential competitive advantages in a rapidly changing international context (Section 2)
Chiral Rings, Anomalies and Electric-Magnetic Duality
We study electric-magnetic duality in the chiral ring of a supersymmetric
U(N_c) gauge theory with adjoint and fundamental matter, in presence of a
general confining phase superpotential for the adjoint and the mesons. We find
the magnetic solution corresponding to both the pseudoconfining and higgs
electric vacua. By means of the Dijkgraaf-Vafa method, we match the effective
glueball superpotentials and show that in some cases duality works exactly
offshell. We give also a picture of the analytic structure of the resolvents in
the magnetic theory, as we smoothly interpolate between different higgs vacua
on the electric side.Comment: 54 pages, harvmac. v2: typos correcte
Threshold Photo/Electro Pion Production - Working Group Summary
We summarize the pertinent experimental and theoretical developments in the
field of pion photo- and electroproduction in the threshold region. We discuss
which experiments and which calculations should be done/performed in the
future.Comment: plain TeX (macro included), 6pp, summary talk presented at the
workshop on "Chiral Dynamics: Theory and Experiments", MIT, July 25-29, 199
An electromagnetic shashlik calorimeter with longitudinal segmentation
A novel technique for longitudinal segmentation of shashlik calorimeters has
been tested in the CERN West Area beam facility. A 25 tower very fine samplings
e.m. calorimeter has been built with vacuum photodiodes inserted in the first 8
radiation lengths to sample the initial development of the shower. Results
concerning energy resolution, impact point reconstruction and electron/pion
separation are reported.Comment: 13 pages, 12 figure
Quiver Gauge Theory and Extended Electric-magnetic Duality
We construct N=1 A-D-E quiver gauge theory with the gauge kinetic term which
depends on the adjoint chiral superfields, as a low energy effective theory on
D5-branes wrapped on 2-cycles of Calabi-Yau 3-fold in IIB string theory. The
field-dependent gauge kinetic term can be engineered by introducing B-field
which holomorphically varies on the base space (complex plane) of Calabi-Yau.
We consider Weyl reflection on A-D-E node, which acts non-trivially on the
gauge kinetic term. It is known that Weyl reflection is related to N=1
electric-magnetic duality. Therefore, the non-trivial action implies an
extension of the electric-magnetic duality to the case with the field-dependent
gauge kinetic term. We show that this extended duality is consistent from the
field theoretical point of view. We also consider the duality map of the
operators.Comment: 24 pages; v2: references added, typos correcte
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