242 research outputs found
A note on chiral fermions and heterotic strings
An off-shell manifestly (8,0) worldsheet supersymmetric formulation of a
multiplet describing physical chiral fermions is given. The multiplet can be
used to complete the doubly supersymmetric (twistor-like) action for the
heterotic string. Correction of technical errors.Comment: 10 page
Intersecting branes and Supersymmetry
We consider intersecting M-brane solutions of supergravity in eleven
dimensions. Supersymmetry turns out to be a powerful tool in obtaining such
solutions and their generalizations.Comment: 6 pages, Latex, Presented at Supersymmetry and Quantum Field Theory,
International Seminar dedicated to the memory of D. V. Volkov, Kharkov, 199
Lorentz-Covariant Green-Schwarz Superstring Amplitudes
In a recent paper, the BRST formalism for the gauge-fixed N=2 twistor-string
was used to calculate Green-Schwarz supersring scattering amplitudes with an
arbitrary number of loops and external massless states. Although the
gauge-fixing procedure preserved the worldsheet N=2 superconformal invariance
of the twistor-string, it broke the target-space SO(9,1) super-Poincar\'e
invariance down to an SU(4)xU(1) subgroup. In this paper, generators for the
SO(9,1) super-Poincar\'e transformations, as well as manifestly covariant
vertex operators, are explicitly constructed out of the gauge-fixed matter
fields. The earlier calculated amplitudes are then expressed in manifestly
Lorentz-covariant notation.Comment: 11 pages plain Tex, KCL-TH-92-
The Heterotic Green-Schwarz Superstring on an N=(2,0) Super-Worldsheet
By defining the heterotic Green-Schwarz superstring action on an N=(2,0)
super-worldsheet, rather than on an ordinary worldsheet, many problems with the
interacting Green-Schwarz superstring formalism can be solved. In the
light-cone approach, superconformally transforming the light-cone
super-worldsheet onto an N=(2,0) super-Riemann surface allows the elimination
of the non-trivial interaction-point operators that complicate the evaluation
of scattering amplitudes. In the Polyakov approach, the ten-dimensional
heterotic Green-Schwarz covariant action defined on an N=(2,0) super-worldsheet
can be gauge-fixed to a free-field action with non-anomalous N=(2,0)
superconformal invariance, and integrating the exponential of the covariant
action over all punctured N=(2,0) super-Riemann surfaces produces scattering
amplitudes that closely resemble amplitudes obtained using the unitary
light-cone approach.Comment: 33 page
On superembedding approach and its possible application in search for SO(32) heterotic five-brane equations
We elaborate the superembedding description of 'simple' D = 10, N = 1
five-brane and discuss the possible application of the superembedding approach
in search for the equations of motion of the mysterious SO(32) heterotic five
brane on this basis.Comment: 9 pages, LaTeX, w-art styl
String theory triplets and higher-spin curvatures
Unconstrained local Lagrangians for higher-spin gauge theories are bound to
involve auxiliary fields, whose integration in the partition function generates
geometric, effective actions expressed in terms of curvatures. When applied to
the triplets, emerging from the tensionless limit of open string field theory,
the same procedure yields interesting alternative forms of geometric
Lagrangians, expressible for both bosons and fermions as squares of
field-strengths. This shows that higher-spin curvatures might play a role in
the dynamics, regardless of whether the Fronsdal-Labastida constraints are
assumed or forgone.Comment: 14 pages. Eqs. (2.13) and (3.7) added. Footnotes 8 and 14 and
corresponding references included. Additional minor changes. To appear in
Phys. Lett.
An Assessment of the Model of Concentration Addition for Predicting the Estrogenic Activity of Chemical Mixtures in Wastewater Treatment Works Effluents
The effects of simple mixtures of chemicals, with similar mechanisms of action, can be predicted using the concentration addition model (CA). The ability of this model to predict the estrogenic effects of more complex mixtures such as effluent discharges, however, has yet to be established. Effluents from 43 U.K. wastewater treatment works were analyzed for the presence of the principal estrogenic chemical contaminants, estradiol, estrone, ethinylestradiol, and nonylphenol. The measured concentrations were used to predict the estrogenic activity of each effluent, employing the model of CA, based on the relative potencies of the individual chemicals in an in vitro recombinant yeast estrogen screen (rYES) and a short-term (14-day) in vivo rainbow trout vitellogenin induction assay. Based on the measured concentrations of the four chemicals in the effluents and their relative potencies in each assay, the calculated in vitro and in vivo responses compared well and ranged between 3.5 and 87 ng/L of estradiol equivalents (E2 EQ) for the different effluents. In the rYES, however, the measured E2 EQ concentrations in the effluents ranged between 0.65 and 43 ng E2 EQ/L, and they varied against those predicted by the CA model. Deviations in the estimation of the estrogenic potency of the effluents by the CA model, compared with the measured responses in the rYES, are likely to have resulted from inaccuracies associated with the measurement of the chemicals in the extracts derived from the complex effluents. Such deviations could also result as a consequence of interactions between chemicals present in the extracts that disrupted the activation of the estrogen response elements in the rYES. E2 EQ concentrations derived from the vitellogenic response in fathead minnows exposed to a series of effluent dilutions were highly comparable with the E2 EQ concentrations derived from assessments of the estrogenic potency of these dilutions in the rYES. Together these data support the use of bioassays for determining the estrogenic potency of WwTW effluents, and they highlight the associated problems for modeling approaches that are reliant on measured concentrations of estrogenic chemicals
Reducible higher-spin multiplets in flat and AdS spaces and their geometric frame-like formulation
We consider the frame-like formulation of reducible sets of totally symmetric
bosonic and fermionic higher-spin fields in flat and AdS backgrounds of any
dimension, that correspond to so-called higher-spin triplets resulting from the
string-inspired BRST approach. The explicit relationship of the fields of
higher-spin triplets to the higher-spin vielbeins and connections is found. The
gauge invariant actions are constructed including, in particular, the reducible
(i.e. triplet) higher-spin fermion case in AdS_D space.Comment: 1+49 pages, This is an essentially extended version of the
contribution to the volume dedicated to the 60th birthday anniversary of
Joseph Buchbinder; v2 FIAN Preprint No and references adde
BPS preons and tensionless super-p-brane in generalized superspace
Tensionless super-p-branes in a generalized superspace with additional
tensorial central charge coordinates may provide an extended object model for
BPS preons, i.e. for the hypothetical constituents of M-theory preserving 31 of
32 supersymmetries [hep-th/0101113].Comment: 11 pages, LaTeX, no figures. V.2: discussions in sec. 5 extended,
references added, to appear in Phys. Lett.
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