135 research outputs found
Effective Superpotentials via Konishi Anomaly
We use Ward identities derived from the generalized Konishi anomaly in order
to compute effective superpotentials for SU(N), SO(N) and
supersymmetric gauge theories coupled to matter in various representations. In
particular we focus on cubic and quartic tree level superpotentials. With this
technique higher order corrections to the perturbative part of the effective
superpotential can be easily evaluated.Comment: 17 pages, harvma
Black-holes, topological strings and large N phase transitions
The counting of microstates of BPS black-holes on local Calabi-Yau of the
form is explored
by computing the partition function of q-deformed Yang-Mills theory on .
We obtain, at finite , the instanton expansion of the gauge theory. It can
be written exactly as the partition function for U(N) Chern-Simons gauge theory
on a Lens space, summed over all non-trivial vacua, plus a tower of
non-perturbative instanton contributions. In the large limit we find a
peculiar phase structure in the model. At weak string coupling the theory
reduces to the trivial sector and the topological string partition function on
the resolved conifold is reproduced in this regime. At a certain critical
point, instantons are enhanced and the theory undergoes a phase transition into
a strong coupling regime. The transition from the strong coupling phase to the
weak coupling phase is of third order.Comment: 16 pages, 3 figures; Invited talk given at QG05, Cala Gonone (Italy),
September 200
Instanton Counting and Wall-Crossing for Orbifold Quivers
Noncommutative Donaldson-Thomas invariants for abelian orbifold singularities can be studied via the enumeration of instanton solutions in a six-dimensional noncommutative {Mathematical expression} gauge theory; this construction is based on the generalized McKay correspondence and identifies the instanton counting with the counting of framed representations of a quiver which is naturally associated with the geometry of the singularity. We extend these constructions to compute BPS partition functions for higher-rank refined and motivic noncommutative Donaldson-Thomas invariants in the Coulomb branch in terms of gauge theory variables and orbifold data. We introduce the notion of virtual instanton quiver associated with the natural symplectic charge lattice which governs the quantum wall-crossing behaviour of BPS states in this context. The McKay correspondence naturally connects our formalism with other approaches to wall-crossing based on quantum monodromy operators and cluster algebras
Matrix Models of Noncommutative (2d+1) Lattice Gauge Theories
We investigate the problem of mapping, through the Morita equivalence, odd
dimensional noncommutative lattice gauge theories onto suitable matrix models.
We specialize our analysis to noncommutative three dimensional QED (NCQED) and
scalar QED (NCSQED), for which we explicitly build the corresponding Matrix
Model.Comment: 13 pages, LaTeX, no Figure
Spacetime Properties of ZZ D-Branes
We study the tachyon and the RR field sourced by the ZZ D-branes in
type 0 theories using three methods. We first use the mini-superspace
approximation of the closed string wave functions of the tachyon and the RR
scalar to probe these fields. These wave functions are then extended beyond the
mini-superspace approximation using mild assumptions which are motivated by the
properties of the corresponding wave functions in the mini-superspace limit.
These are then used to probe the tachyon and the RR field sourced. Finally we
study the space time fields sourced by the ZZ D-branes using the FZZT
brane as a probe. In all the three methods we find that the tension of the
ZZ brane is times the tension of the ZZ brane. The RR
charge of these branes is non-zero only for the case of both and odd,
in which case it is identical to the charge of the brane. As a
consistency check we also verify that the space time fields sourced by the
branes satisfy the corresponding equations of motion.Comment: 32 pages, 4 figures. Clarifications on the principal characterization
of ZZ branes added. Reference adde
Area-preserving diffeomorphisms in gauge theory on a non-commutative plane: a lattice study
We consider Yang-Mills theory with the U(1) gauge group on a non-commutative
plane. Perturbatively it was observed that the invariance of this theory under
area-preserving diffeomorphisms (APDs) breaks down to a rigid subgroup SL(2,R).
Here we present explicit results for the APD symmetry breaking at finite gauge
coupling and finite non-commutativity. They are based on lattice simulations
and measurements of Wilson loops with the same area but with a variety of
different shapes. Our results are consistent with the expected loss of
invariance under APDs. Moreover, they strongly suggest that non-perturbatively
the SL(2,R) symmetry does not persist either.Comment: 28 pages, 15 figures, published versio
A failure mode and effect analysis (FMEA)-based approach for risk assessment of scientific processes in non-regulated research laboratories
AbstractNowadays, Quality Management tools such as failure mode and effect analysis (FMEA) are widely used throughout the aeronautical, automotive, software, food services, health care and many other industries to sustain and improve quality and safety. The increasing complexity of scientific research makes it more difficult to maintain all activities under control, in order to guarantee validity and reproducibility of results. Even in non-regulated research, scientists need to be supported with management tools that maximize study performance and outcomes, while facilitating the research process. Frequently, steps that involve human intervention are the weak links in the process. Risk analysis therefore gives considerable benefit to analytical validation, assessing and avoiding failures due to human error, potential imprecision in applying protocols, uncertainty in equipment function and imperfect control of materials. This paper describes in detail how FMEA methodology can be applied as a performance improvement tool in the field of non-regulated research, specifically on a basic Life Sciences research process. We chose as "pilot process" the selection of oligonucleotide aptamers for therapeutic purposes, as an example of a complex and multi-step process, suitable for technology transfer. We applied FMEA methodology, seeking every opportunity for error and its impact on process output, and then, a set of improvement actions was generated covering most aspects of laboratory practice, such as equipment management and staff training. We also propose a useful tool supporting the risk assessment of research processes and its outputs and that we named "FMEA strip worksheet." These tools can help scientists working in non-regulated research to approach Quality Management and to perform risk evaluation of key scientific procedures and processes with the final aim to increase and better control efficiency and efficacy of their research
Gauge-Invariant Resummation Formalism and Unitarity in Non-Commutative QED
We re-examine the perturbative properties of four-dimensional non-commutative
QED by extending the pinch techniques to the theta-deformed case. The explicit
independence of the pinched gluon self-energy from gauge-fixing parameters, and
the absence of unphysical thresholds in the resummed propagators permits a
complete check of the optical theorem for the off-shell two-point function. The
known anomalous (tachyonic) dispersion relations are recovered within this
framework, as well as their improved version in the (softly broken) SUSY case.
These applications should be considered as a first step in constructing
gauge-invariant truncations of the Schwinger-Dyson equations in the
non-commutative case. An interesting result of our formalism appears when
considering the theory in two dimensions: we observe a finite gauge-invariant
contribution to the photon mass because of a novel incarnation of IR/UV mixing,
which survives the commutative limit when matter is present.Comment: 30 pages, 2 eps figure, uses axodraw. Citations adde
An example of localized D-branes solution on PP-wave backgrounds
In this note we provide an explicit example of type IIB supersymmetric
D3-branes solution on a pp-wave like background, consisting in the product of
an eight-dimensional pp-wave times a two-dimensional flat space. An interesting
property of our solution is the fully localization of the D3-branes (i.e. the
solution depends on all the transverse coordinates). Then we show the
generalization to other Dp-branes and to the D1/D5 system.Comment: 14 pages, 1 table; v2. references adde
- …