3,908 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
Dark Matter and Pseudo-flat Directions in Weakly Coupled SUSY Breaking Sectors
We consider candidates for dark matter in models of gauge mediated
supersymmetry breaking, in which the supersymmetry breaking sector is weakly
coupled and calculable. Such models typically contain classically flat
directions, that receive one-loop masses of a few TeV. These pseudo-flat
directions provide a new mechanism to account for the cold dark matter relic
abundance. We discuss also the possibility of heavy gravitino dark matter in
such models.Comment: 16 pages, 2 figures. v2: comments, refs adde
Planar limits of three-dimensional incompressible flows with helical symmetry
Helical symmetry is invariance under a one-dimensional group of rigid motions
generated by a simultaneous rotation around a fixed axis and translation along
the same axis. The key parameter in helical symmetry is the step or pitch, the
magnitude of the translation after rotating one full turn around the symmetry
axis. In this article we study the limits of three-dimensional helical viscous
and inviscid incompressible flows in an infinite circular pipe, with
respectively no-slip and no-penetration boundary conditions, as the step
approaches infinity. We show that, as the step becomes large, the
three-dimensional helical flow approaches a planar flow, which is governed by
the so-called two-and-half Navier-Stokes and Euler equations, respectively.Comment: 30 page
Vanishing Viscosity Limits and Boundary Layers for Circularly Symmetric 2D Flows
We continue the work of Lopes Filho, Mazzucato and Nussenzveig Lopes [LMN],
on the vanishing viscosity limit of circularly symmetric viscous flow in a disk
with rotating boundary, shown there to converge to the inviscid limit in
-norm as long as the prescribed angular velocity of the
boundary has bounded total variation. Here we establish convergence in stronger
and -Sobolev spaces, allow for more singular angular velocities
, and address the issue of analyzing the behavior of the boundary
layer. This includes an analysis of concentration of vorticity in the vanishing
viscosity limit. We also consider such flows on an annulus, whose two boundary
components rotate independently.
[LMN] Lopes Filho, M. C., Mazzucato, A. L. and Nussenzveig Lopes, H. J.,
Vanishing viscosity limit for incompressible flow inside a rotating circle,
preprint 2006
Neutral Pion Photoproduction on Nuclei in Baryon Chiral Perturbation Theory
Threshold neutral pion photoproduction on light nuclei is studied in the
framework of baryon chiral perturbation theory. We obtain a general formula for
the electric dipole amplitude in the special case of neutral pion
photoproduction on a nucleus. To third order in small momenta, the amplitude is
a sum of 2- and 3-body interactions with no undetermined parameters. With
reasonable input from the single nucleon sector, our result for neutral pion
photoproduction on the deuteron is in agreement with experiment.Comment: 24 pages, 4 uuencoded postscript figures, uses LaTex and epsf.tex.
Added footnote and references. Minor changes in text and forma
An innovative approach on directed energy deposition optimization: A study of the process environment's influence on the quality of Ti-6Al-4V Samples
Blown powder additive manufacturing technologies are not restricted to the use of a process chamber. This feature allows to build larger components with respect to conventional powder bed processes. This peculiarity is mostly promising for manufacturing large components or repairing/rebuilding parts of large systems. The main downside of using an open environment, even if a protective shielding gas system is adopted, is the lack of control of process atmosphere. This is particularly critical for titanium alloys which are very sensitive to oxygen/nitrogen pick-up; they have a detrimental effect on ductility, by causing embrittlement and possibly leading to the formation of cracks. It is then important to address how environmental factors, such as process atmosphere and platform temperature, impact not only on the processability but also on the final component properties, both from a compositional and mechanical point of view. The correlations between these environmental factors and microstructure, interstitials content, grain size, and hardness were investigated. Moreover, the Hall-Petch equation was then adopted to additive manufacturing microstructures, characterized by a columnar grain morphology, and used to further investigate the relationship intercurring between grains and hardness and how different microstructures might influence this correlation
Super-Group Field Cosmology
In this paper we construct a model for group field cosmology. The classical
equations of motion for the non-interactive part of this model generate the
Hamiltonian constraint of loop quantum gravity for a homogeneous isotropic
universe filled with a scalar matter field. The interactions represent topology
changing processes that occurs due to joining and splitting of universes. These
universes in the multiverse are assumed to obey both bosonic and fermionic
statistics, and so a supersymmetric multiverse is constructed using superspace
formalism. We also introduce gauge symmetry in this model. The supersymmetry
and gauge symmetry are introduced at the level of third quantized fields, and
not the second quantized ones. This is the first time that supersymmetry has
been discussed at the level of third quantized fields.Comment: 14 pages, 0 figures, accepted for publication in Class. Quant. Gra
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