246 research outputs found
The anomalous current multiplet in 6D minimal supersymmetry
For supersymmetric gauge theories with eight supercharges in four, five and
six dimensions, a conserved current belongs to the linear multiplet. In the
case of six-dimensional Poincar\'e supersymmetry, we present a
consistent deformation of the linear multiplet which describes chiral
anomalies. This is achieved by developing a superform formulation for the
deformed linear multiplet. In the abelian case, we compute a nonlocal effective
action generating the gauge anomaly.Comment: 27 pages; V2: published versio
Chiral anomalies in six dimensions from harmonic superspace
We develop a superfield approach to compute chiral anomalies in general
supersymmetric gauge theories in six dimensions. Within the
harmonic-superspace formulation for these gauge theories, the anomalous
contributions to the effective action only come from matter and ghost
hypermultiplets. By studying the short-distance behaviour of the propagator for
the hypermultiplet coupled to a background vector multiplet, we compute the
covariant and consistent chiral anomalies. We also provide a superform
formulation for the non-abelian anomalous current multiplet in general supersymmetric gauge theories.Comment: 33 page
Superconformal field theory in three dimensions: Correlation functions of conserved currents
For N-extended superconformal field theories in three spacetime dimensions
(3D), with N=1,2,3, we compute the two- and three-point correlation functions
of the supercurrent and the flavour current multiplets. We demonstrate that
supersymmetry imposes additional restrictions on the correlators of conserved
currents as compared with the non-supersymmetric case studied by Osborn and
Petkou in hep-th/9307010. It is shown that the three-point function of the
supercurrent is determined by a single functional form consistent with the
conservation equation and all the symmetry properties. Similarly, the
three-point function of the flavour current multiplets is also determined by a
single functional form in the N=1 and N=3 cases. The specific feature of the
N=2 case is that two independent structures are allowed for the three-point
function of flavour current multiplets, but only one of them contributes to the
three-point function of the conserved currents contained in these multiplets.
Since the supergravity and super-Yang-Mills Ward identities are expected to
relate the coefficients of the two- and three-point functions under
consideration, the results obtained for 3D superconformal field theory are
analogous to those in 2D conformal field theory.
In addition, we present a new supertwistor construction for compactified
Minkowski superspace. It is suitable for developing superconformal field theory
on 3D spacetimes other than Minkowski space, such as S^1 x S^2 and its
universal covering space R x S^2.Comment: 81 pages; v2: reference added, typos correcte
Implications of N=4 superconformal symmetry in three spacetime dimensions
We study implications of N=4 superconformal symmetry in three dimensions,
thus extending our earlier results in arXiv:1503.04961 devoted to the N=1,2,3
cases. We show that the three-point function of the supercurrent in N=4
superconformal field theories contains two linearly independent forms. However,
only one of these structures contributes to the three-point function of the
energy-momentum tensor and the other one is present in those N=4 superconformal
theories which are not invariant under the mirror map. We point out that
general N=4 superconformal field theories admit two inequivalent flavour
current multiplets and show that the three-point function of each of them is
determined by one tensor structure. As an example, we compute the two- and
three-point functions of the conserved currents in N=4 superconformal models of
free hypermultiplets. We also derive the universal relations between the
coefficients appearing in the two- and three-point correlators of the
supercurrent and flavour current multiplets in all superconformal theories with
N=1,2,3,4 supersymmetry. Our derivation is based on the use of Ward identities
in conjunction with superspace reduction techniques.Comment: 75 page
Bi-harmonic superspace for N=4 d=4 super Yang-Mills
We develop N=4 d=4 bi-harmonic superspace and use it to derive a novel form
for the low-energy effective action in N=4 super Yang-Mills theory. We solve
the N=4 supergauge constraints in this superspace in terms of analytic
superfields. Using these superfields, we construct a simple functional that
respects N=4 supersymmetry and scale invariance. In components, it reproduces
all on-shell terms in the four-derivative part of the N=4 SYM effective action;
in particular, the F^4/X^4 and Wess-Zumino terms. The latter comes out in a
novel SO(3) x SO(3)-invariant form.Comment: 1+19 pages; minor corrections, references adde
Elastic properties of mono- and polycrystalline hexagonal AlB2-like diborides of s, p and d metals from first-principles calculations
We have performed accurate ab initio total energy calculations using the
full-potential linearized augmented plane wave (FP-LAPW) method with the
generalized gradient approximation (GGA) for the exchange-correlation potential
to systematically investigate elastic properties of 18 stable, meta-stable and
hypothetical hexagonal (AlB2-like) metal diborides MB2, where M = Na, Be, Mg,
Ca, Al, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ag and Au. For monocrystalline
MB2 the optimized lattice parameters, independent elastic constants (Cij), bulk
modules (B), shear modules (G) are obtained and analyzed in comparison with the
available theoretical and experimental data. For the first time numerical
estimates of a set of elastic parameters of the polycrystalline MB2 ceramics
(in the framework of the Voigt-Reuss-Hill approximation), namely bulk and shear
modules, compressibility, Young's modules, Poisson's ratio, Lame's coefficients
are performed.Comment: 24 pages, 3 figure
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