16,167 research outputs found
Heterotic Anomaly Cancellation in Five Dimensions
We study the constraints on five-dimensional N=1 heterotic M-theory imposed
by a consistent anomaly-free coupling of bulk and boundary theory. This
requires analyzing the cancellation of triangle gauge anomalies on the
four-dimensional orbifold planes due to anomaly inflow from the bulk. We find
that the semi-simple part of the orbifold gauge groups and certain U(1)
symmetries have to be free of quantum anomalies. In addition there can be
several anomalous U(1) symmetries on each orbifold plane whose anomalies are
cancelled by a non-trivial variation of the bulk vector fields. The mixed U(1)
non-abelian anomaly is universal and there is at most one U(1) symmetry with
such an anomaly on each plane. In an alternative approach, we also analyze the
coupling of five-dimensional gauged supergravity to orbifold gauge theories. We
find a somewhat generalized structure of anomaly cancellation in this case
which allows, for example, non-universal mixed U(1) gauge anomalies. Anomaly
cancellation from the perspective of four-dimensional N=1 effective actions
obtained from E_8xE_8 heterotic string- or M-theory by reduction on a
Calabi-Yau three-fold is studied as well. The results are consistent with the
ones found for five-dimensional heterotic M-theory. Finally, we consider some
related issues of phenomenological interest such as model building with
anomalous U(1) symmetries, Fayet-Illiopoulos terms and threshold corrections to
gauge kinetic functions.Comment: 46 pages, Late
Computation of generalized equivariant cohomologies of Kac-Moody flag varieties
In 1998, Goresky, Kottwitz, and MacPherson showed that for certain projective
varieties X equipped with an algebraic action of a complex torus T, the
equivariant cohomology ring H_T(X) can be described by combinatorial data
obtained from its orbit decomposition. In this paper, we generalize their
theorem in three different ways. First, our group G need not be a torus.
Second, our space X is an equivariant stratified space, along with some
additional hypotheses on the attaching maps. Third, and most important, we
allow for generalized equivariant cohomology theories E_G^* instead of H_T^*.
For these spaces, we give a combinatorial description of E_G(X) as a subring of
\prod E_G(F_i), where the F_i are certain invariant subspaces of X. Our main
examples are the flag varieties G/P of Kac-Moody groups G, with the action of
the torus of G. In this context, the F_i are the T-fixed points and E_G^* is a
T-equivariant complex oriented cohomology theory, such as H_T^*, K_T^* or
MU_T^*. We detail several explicit examples.Comment: 19 pages, 6 figures, this is a new and completely modified version of
DG/040207
Single-inclusive production of large-pT charged particles in hadronic collisions at TeV energies and perturbative QCD predictions
The single inclusive spectrum of charged particles with transverse momenta
pT=3-150 GeV/c measured at midrapidity by the CDF experiment in
proton-antiproton (p-pbar) collisions at sqrt(s)=1.96 TeV is compared to
next-to-leading order (NLO) perturbative QCD calculations using the most recent
parametrizations of the parton distributions and parton-to-hadron fragmentation
functions. Above pT~20 GeV/c, there is a very sizeable disagreement of the
Tevatron data compared to the NLO predictions and to xT-scaling expectations,
suggesting a problem in the experimental data. We also present the predictions
for the pT-differential charged hadron spectra and the associated theoretical
uncertainties for proton-proton (p-p) collisions at LHC energies
(sqrt(s)=0.9-14 TeV). Two procedures to estimate the charged hadron spectra at
LHC heavy-ion collision energies (sqrt(s)=2.76,5.5 TeV) from p-p measurements
are suggested.Comment: 23 pages, 9 figures. A few text additions. Accepted for publication
in JHE
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