15,212 research outputs found
A Mathematica Package for Computing N=2 Superfield Operator Product Expansions
We describe a general purpose Mathematica package for computing Superfield
Operator Product Expansions in meromorphic superconformal field theory.
Given the SOPEs for a set of ``basic" superfields, SOPEs of arbitrarily
complicated composites can be computed automatically. Normal ordered products
are always reduced to a standard form. It is possible to check the Jacobi
identities, and to compute Poisson brackets (``classical SOPEs''). We present
two explicit examples: a construction of the ``small'' superconformal
algebra in terms of superfields, and a realisation of the
superconformal algebra in terms of chiral and antichiral fermionic superfields.Comment: 15 pages, LaTeX. Minor corrections, particularly to Mathematica
output Out[6],Out[9] in section 4. Available through anonymous ftp from
ftp://euclid.tp.ph.ic.ac.uk/papers/ or on WWW at
http://euclid.tp.ph.ic.ac.uk/Papers
On the two-loop divergences of the 2-point hypermultiplet supergraphs for , SYM theory
We consider , supersymmetric Yang-Mills theory
formulated in harmonic superspace and analyze the structure of
the two-loop divergences in the hypermultiplet sector. Using the superfield background field method we study the two-point supergraphs
with the hypermultiplet legs and prove that their total contribution to the
divergent part of effective action vanishes off shell.Comment: 8 pages, 2 figure
Supergraph analysis of the one-loop divergences in , and gauge theories
We study the one-loop effective action for
supersymmetric Yang--Mills (SYM) theory with hypermultiplets and SYM theory as a subclass of the former, using the off-shell
formulation of these theories in harmonic superspace. We
develop the corresponding supergraph technique and apply it to compute the
one-loop divergences in the background field method ensuring the manifest gauge
invariance. We calculate the two-point Green functions of the gauge superfield
and the hypermultiplet, as well as the three-point gauge-hypermultipet Green
function. Using these Green functions and exploiting gauge invariance of the
theory, we find the full set of the off-shell one-loop divergent contributions,
including the logarithmic and power ones. Our results precisely match with
those obtained earlier in [1,2] within the proper time superfield method.Comment: 32 pages, 5 figure
New approach to nonlinear electrodynamics: dualities as symmetries of interaction
We elaborate on the duality-symmetric nonlinear electrodynamics in a new
formulation with auxiliary tensor fields. The Maxwell field strength appears
only in bilinear terms of the corresponding generic Lagrangian, while the
self-interaction is presented by a function E depending on the auxiliary
fields. Two types of dualities inherent in the nonlinear electrodynamics models
admit a simple off-shell characterization in terms of this function. In the
standard formulation, the continuous U(1) duality symmetry is nonlinearly
realized on the Maxwell field strength. In the new setting, the same symmetry
acts as linear U(1) transformations of the auxiliary field variables. The
nonlinear U(1) duality condition proves to be equivalent to the linear U(1)
invariance of the self-interaction E. The discrete self-duality (or
self-duality by Legendre transformation) amounts to a weaker reflection
symmetry of E. For a class of duality- symmetric Lagrangians we introduce an
alternative representation with the auxiliary scalar field and find new
explicit examples of such systems.Comment: Latex file, 21 page
Nonlinear Realization and Weyl Scale Invariant p=2 Brane
The action of Weyl scale invariant p=2 brane which breaks the target super
Weyl scale symmetry in the N=1, D=4 superspace down to the lower dimensional
Weyl symmetry W(1,2) is derived by the approach of nonlinear realization. The
dual form action for the Weyl scale invariant supersymmetric D2 brane is also
constructed. The interactions of localized matter fields on the brane with the
Nambu-Goldstone fields associated with the breaking of the symmetries in the
superspace and one spatial translation directions are obtained through the
Cartan one-forms of the Coset structures. The covariant derivatives for the
localized matter fields are also obtained by introducing Weyl gauge field as
the compensating field corresponding to the local scale transformation on the
brane world volume.Comment: 20 page
Colliders and Brane Vector Phenomenology
Brane world oscillations manifest themselves as massive vector gauge fields.
Their coupling to the Standard Model is deduced using the method of nonlinear
realizations of the spontaneously broken higher dimensional space-time
symmetries. Brane vectors are stable and weakly interacting, and therefore
escape particle detectors unnoticed. LEP and Tevatron data on the production of
a single photon in conjunction with missing energy are used to delineate
experimentally excluded regions of brane vector parameter space. The additional
region of parameter space accessible to the LHC as well as a future lepton
linear collider is also determined by means of this process.Comment: 12 pages, 13 figure
The evolution of the structure and mechanical properties of aluminum during accumulative roll bonding
The dependence of microstructure, microhardness, and strength properties in tensile strain tests of commercially pure aluminum on strain during accumulative roll-bonding was studied. The methods of transmission electron microscopy and electron back scattered diffraction patterns analysis were used to establish that a lamellar ultrafine structure is formed in aluminum after accumulative roll bonding. The reasons for the difference in the structure and mechanical properties of the aluminum studied from the ones relevant for the aluminum deformed by equalchannel angular pressing are discusse
Chirality tunneling in mesoscopic antiferromagnetic domain walls
We consider a domain wall in the mesoscopic quasi-one-dimensional sample
(wire or stripe) of weakly anisotropic two-sublattice antiferromagnet, and
estimate the probability of tunneling between two domain wall states with
different chirality. Topological effects forbid tunneling for the systems with
half-integer spin S of magnetic atoms which consist of odd number of chains N.
External magnetic field yields an additional contribution to the Berry phase,
resulting in the appearance of two different tunnel splittings in any
experimental setup involving a mixture of odd and even N, and in oscillating
field dependence of the tunneling rate with the period proportional to 1/N.Comment: 4 pages + 2 figures, references correcte
Optical Camera with high temporal resolution to search for transients in the wide field
The wide field optical camera with high temporal resolution for the
continuous monitoring of the sky in order to catch the initial stages of GRBs
is described.Comment: 4 pages, 4 figures. To be published in "Il Nuovo Cimento",
Proceedings of the 4th Rome Workshop on Gamma-Ray Bursts in the Afterglow
Era, eds. L. Piro, L. Amati, S. Covino, B. Gendr
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