241 research outputs found
La valorisation du sang d'abattoirs en Belgique.
peer reviewedCet article comprend une analyse sommaire des possibilités de valorisation du sang recueilli dans les abattoirs d'animaux de boucherie. Après un bref exposé sur la législation belge en la matière et sur les techniques qui permettent un traitement du sang, les auteurs ont estimé les quantités produites au départ des abattoirs belges et qualifié le réseau de collecte en Wallonie
Holographic renormalization and supersymmetry
Holographic renormalization is a systematic procedure for regulating
divergences in observables in asymptotically locally AdS spacetimes. For dual
boundary field theories which are supersymmetric it is natural to ask whether
this defines a supersymmetric renormalization scheme. Recent results in
localization have brought this question into sharp focus: rigid supersymmetry
on a curved boundary requires specific geometric structures, and general
arguments imply that BPS observables, such as the partition function, are
invariant under certain deformations of these structures. One can then ask if
the dual holographic observables are similarly invariant. We study this
question in minimal N = 2 gauged supergravity in four and five dimensions. In
four dimensions we show that holographic renormalization precisely reproduces
the expected field theory results. In five dimensions we find that no choice of
standard holographic counterterms is compatible with supersymmetry, which leads
us to introduce novel finite boundary terms. For a class of solutions
satisfying certain topological assumptions we provide some independent tests of
these new boundary terms, in particular showing that they reproduce the
expected VEVs of conserved charges.Comment: 70 pages; corrected typo
A topologically twisted index for three-dimensional supersymmetric theories
We provide a general formula for the partition function of three-dimensional (formula presented) gauge theories placed on S2
7S1 with a topological twist along S2, which can be interpreted as an index for chiral states of the theories immersed in background magnetic fields. The result is expressed as a sum over magnetic fluxes of the residues of a meromorphic form which is a function of the scalar zero-modes. The partition function depends on a collection of background magnetic fluxes and fugacities for the global symmetries. We illustrate our formula in many examples of 3d Yang-Mills-Chern-Simons theories with matter, including Aharony and Giveon-Kutasov dualities. Finally, our formula generalizes to \u3a9-backgrounds, as well as two-dimensional theories on S2 and four-dimensional theories on S2
7 T2. In particular this provides an alternative way to compute genus-zero A-model topological amplitudes and Gromov-Witten invariants
Seiberg duality for Chern-Simons quivers and D-brane mutations
Chern-Simons quivers for M2-branes at Calabi-Yau singularities are best
understood as the low energy theory of D2-branes on a dual type IIA background.
We show how the D2-brane point of view naturally leads to three dimensional
Seiberg dualities for Chern-Simons quivers with chiral matter content: They
arise from a change of brane basis (or mutation), in complete analogy with the
better known Seiberg dualities for D3-brane quivers. This perspective
reproduces the known rules for Seiberg dualities in Chern-Simons-Yang-Mills
theories with unitary gauge groups. We provide explicit examples of dual
theories for the quiver dual to the Y^{p,q}(CP^2) geometries. We also comment
on the string theory derivation of CS quivers dual to massive type IIA
geometries.Comment: 32 pages+appendix; v2: added a referenc
Higgs branch localization in three dimensions
We show that the supersymmetric partition function of three-dimensional N =2 R-symmetric Chern-Simons-matter theories on the squashed S 3 and on S 2
7 S 1 can be computed with the so-called Higgs branch localization method, alternative to the more standard Coulomb branch localization. For theories that could be completely Higgsed by Fayet-Iliopoulos terms, the path integral is dominated by BPS vortex strings sitting at two circles in the geometry. In this way, the partition function directly takes the form of a sum, over a finite number of points on the classical Coulomb branch, of a vortex-string times an antivortex-string partition functions. \ua9 2014 The Author(s)
Twisted characters and holomorphic symmetries
We consider holomorphic twists of arbitrary supersymmetric theories in four
dimensions. Working in the BV formalism, we rederive classical results
characterizing the holomorphic twist of chiral and vector supermultiplets,
computing the twist explicitly as a family over the space of nilpotent
supercharges in minimal supersymmetry. The BV formalism allows one to work with
or without auxiliary fields, according to preference; for chiral superfields,
we show that the result of the twist is an identical BV theory, the holomorphic
system with superpotential, independent of whether or not
auxiliary fields are included. We compute the character of local operators in
this holomorphic theory, demonstrating agreement of the free local operators
with the usual index of free fields. The local operators with superpotential
are computed via a spectral sequence, and are shown to agree with functions on
a formal mapping space into the derived critical locus of the superpotential.
We consider the holomorphic theory on various geometries, including Hopf
manifolds and products of arbitrary pairs of Riemann surfaces, and offer some
general remarks on dimensional reductions of holomorphic theories along the
-sphere to topological quantum mechanics. We also study an
infinite-dimensional enhancement of the flavor symmetry in this example, to a
recently-studied central extension of the derived holomorphic functions with
values in the original Lie algebra that generalizes the familiar Kac--Moody
enhancement in two-dimensional chiral theories
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