1,249 research outputs found
On the logarithmic behaviour in N=4 SYM theory
We show that the logarithmic behaviour seen in perturbative and non
perturbative contributions to Green functions of gauge-invariant composite
operators in N=4 SYM with SU(N) gauge group can be consistently interpreted in
terms of anomalous dimensions of unprotected operators in long multiplets of
the superconformal group SU(2,2|4). In order to illustrate the point we analyse
the short-distance behaviour of a particularly simple four-point Green function
of the lowest scalar components of the N=4 supercurrent multiplet. Assuming the
validity of the Operator Product Expansion, we are able to reproduce the known
value of the one-loop anomalous dimension of the single-trace operators in the
Konishi supermultiplet. We also show that it does not receive any
non-perturbative contribution from the one-instanton sector. We briefly comment
on double- and multi-trace operators and on the bearing of our results on the
AdS/SCFT correspondence.Comment: 18 pages, Late
Properties of the Konishi multiplet in N=4 SYM theory
We study perturbative and non-perturbative properties of the Konishi
multiplet in N=4 SYM theory in D=4 dimensions. We compute two-, three- and
four-point Green functions with single and multiple insertions of the lowest
component of the multiplet, and of the lowest component of the supercurrent
multiplet. These computations require a proper definition of the renormalized
operator and lead to an independent derivation of its anomalous dimension. The
O(g^2) value found in this way is in agreement with previous results. We also
find that instanton contributions to the above correlators vanish. From our
results we are able to identify some of the lowest dimensional gauge-invariant
composite operators contributing to the OPE of the correlation functions we
have computed. We thus confirm the existence of an operator belonging to the
representation 20', which has vanishing anomalous dimension at order g^2 and
g^4 in perturbation theory as well as at the non-perturbative level, despite
the fact that it does not obey any of the known shortening conditions.Comment: 23 pages, latex, no figure
Correlation Functions of Conserved Currents in Four Dimensional Conformal Field Theory
We derive a generating function for all the 3-point functions of higher spin
conserved currents in four dimensional conformal field theory. The resulting
expressions have a rather surprising factorized form which suggest that they
can all be realized by currents built from free massless fields of arbitrary
(half-)integer spin s. This property is however not necessarily true also for
the higher-point functions. As an illustration we analyze the general 4-point
function of conserved abelian U(1) currents of scale dimension equal to three
and find that apart from the two free field realizations there is a unique
possible function which may correspond to an interacting theory. Although this
function passes several non-trivial consistency tests, it remains an open
challenging problem whether it can be actually realized in an interacting CFT.Comment: 20 pages, LaTeX, references adde
Neutrinos: the Key to UHE Cosmic Rays
Observations of ultrahigh energy cosmic rays (UHECR) do not uniquely
determine both the injection spectrum and the evolution model for UHECR sources
- primarily because interactions during propagation obscure the early Universe
from direct observation. Detection of neutrinos produced in those same
interactions, coupled with UHECR results, would provide a full description of
UHECR source properties.Comment: three pages, three figures. corrected typo
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