4,030 research outputs found
Supersymmetric Adler-Bardeen anomaly in N=1 super-Yang-Mills theories
We provide a study of the supersymmetric Adler--Bardeen anomaly in the super-Yang--Mills theories. We work in the component formalism that
includes shadow fields, for which Slavnov--Taylor identities can be
independently set for both gauge invariance and supersymmetry. We find a method
with improved descent equations for getting the solutions of the consistency
conditions of both Slavnov--Taylor identities and finding the local field
polynomials for the standard Adler--Bardeen anomaly and its supersymmetric
counterpart. We give the explicit solution for the ten-dimensional case.Comment: 9 pages ; references adde
Constant Froude number in a circular hydraulic jump and its implication on the jump radius selection
The properties of a standard hydraulic jump depend critically on a Froude
number Fr defined as the ratio of the flow velocity to the gravity waves speed.
In the case of a horizontal circular jump, the question of the Froude number is
not well documented. Our experiments show that Fr measured just after the jump
is locked on a constant value that does not depend on flow rate Q, kinematic
viscosity {\nu} and surface tension {\gamma}. Combining this result to a
lubrication description of the outer flow yields, under appropriate conditions,
a new and simple law ruling the jump radius RJ : , in excellent agreement
with our experimental data. This unexpected RJ result asks an unsolved question
to all available models.Comment: 5 pages, 3 figure
Twisted Superspace
We formulate the ten-dimensional super-Yang-Mills theory in a twisted
superspace with 8+1 supercharges. Its constraints do not imply the equations of
motion and we solve them. As a preliminary step for a complete formulation in a
twisted superspace, we give a superspace path-integral formulation of the N=2,
d=4 super-Yang-Mills theory without matter. The action is the sum of a
Chern--Simons term depending on a super-connection plus a BF-like term. The
integration over the superfield B implements the twisted superspace constraints
on the super-gauge field, and the Chern-Simons action reduces to the known
action in components
Apodized phase mask coronagraphs for arbitrary apertures. II. Comprehensive review of solutions for the vortex coronagraph
With a clear circular aperture, the vortex coronagraph perfectly cancels an
on-axis point source and offers a 0.9 or 1.75 lambda/D inner working angle for
topological charge 2 or 4, respectively. Current and near-future large
telescopes are on-axis, however, and the diffraction effects of the central
obscuration, and the secondary supports are strong enough to prevent the
detection of companions 1e-3 - 1e-5 as bright as, or fainter than, their host
star. Recent advances show that a ring apodizer can restore the performance of
this coronagraph by compensating for the diffraction effects of a circular
central obscuration in a 1D modeling of the pupil. We extend this work and
optimize apodizers for arbitrary apertures in 2D in order to tackle the
diffraction effects of the spiders and other noncircular artefacts in the
pupil. We use a numerical optimization scheme to compute hybrid coronagraph
designs that combine the advantages of the vortex coronagraph (small in IWA)
and of shaped pupils coronagraphs (robustness to central obscuration and pupil
asymmetric structures). We maximize the apodizer transmission, while
constraints are set on the extremum values of the electric field that is
computed in chosen regions of the Lyot plane through closed form expressions.
Optimal apodizers are computed for topological charges 2 and 4 vortex
coronagraphs and for telescope apertures with 10-30% central obscurations and
0-1% thick spiders. We characterize the impacts of the obscuration ratio and
the thickness of the spiders on the throughput and the IWA for the two
topological charges.Comment: 23 pages, 12 figures, 2 table
Structural properties of silicon dioxide thin films densified by medium-energy particles
Classical molecular-dynamics simulations have been carried out to investigate
densification mechanisms in silicon dioxide thin films deposited on an
amorphous silica surface, according to a simplified ion-beam assisted
deposition (IBAD) scenario. We compare the structures resulting from the
deposition of near-thermal (1 eV) SiO particles to those obtained with
increasing fraction of 30 eV SiO particles. Our results show that there
is an energy interval - between 12 and 15 eV per condensing SiO unit on
average - for which the growth leads to a dense, low-stress amorphous
structure, in satisfactory agreement with the results of low-energy ion-beam
experiments. We also find that the crossover between low- and high-density
films is associated with a tensile to compressive stress transition, and a
simultaneous healing of structural defects of the {\em a-}SiO network,
namely three- and four-fold rings. It is observed, finally, that densification
proceeds through significant changes at intermediate length scales (4--10 \AA),
leaving essentially unchanged the ``building blocks'' of the network, viz. the
Si(O) tetrahedra. This latter result is in qualitative agreement
with the mechanism proposed to explain the irreversible densification of
amorphous silica recovered from high pressures ( 15--20 GPa).Comment: 12 pages including 10 postscript figures; submitted to Phys. Rev. B;
related publications can be found on web site
http://www.centrcn.umontreal.ca/~lewi
Orbits and reversals of a drop rolling inside a horizontal circular hydraulic jump
We explore the complex dynamics of a non-coalescing drop of moderate size
inside a circular hydraulic jump of the same liquid formed on a horizontal
disk. In this situation the drop is moving along the jump and one observes two
different motions: a periodic one (it orbitates at constant speed) and an
irregular one involving reversals of the orbital motion. Modeling the drop as a
rigid sphere exchanging friction with liquid across a thin film of air, we
recover the orbital motion and the internal rotation of the drop. This internal
rotation is experimentally observed.Comment: 5 pages, 6 figure
L’abandon du traducteur : Prolégomènes à la traduction des « Tableaux parisiens » de Charles Baudelaire
L'abandon du traducteur — Un des jalons majeurs pour la traductologie contemporaine, l'essai sur la traduction de Walter Benjamin est aussi un texte central dans son oeuvre et dans la pensée moderne par ses liens à la philosophie du langage et à la philosophie de l'histoire. C'est dans cet éclairage que L. Lamy et A. Nouss proposent cette nouvelle traduction enrichie d'un important appareil de notes destiné à la fois à en faciliter la compréhension et à lui restituer toute sa densité conceptuelle.L'abandon du traducteur — A major landmark for contemporary translation studies, Walter Benjamin's essay on translation is also a text central to his body of work and to modern reflection by way of its links to the philosophy of language and the philosophy of history. It is in this perspective that L. Lamy and A. Nouss offer this new translation accompanied by a comprehensive critical apparatus intended to facilitate its understanding and to restore its conceptual density
Holomorphic Superspace
We give a twisted holomorphic superspace description for the super-Yang-Mills
theory, using holomorphic and antiholomorphic decompositions of twisted
spinors. We consider the case of the N=1 super-Yang-Mills theory in four
dimensions. We solve the constraints in two different manners, without and with
a prepotential. This might have further application for an holomorphic
superspace description of N=1,d=10 theory. We also explain how the N=1 and N=2
holomorphic superspaces are related.Comment: 17 pages, revised versio
- …