250 research outputs found
Graded Contractions of Affine Kac-Moody Algebras
The method of graded contractions, based on the preservation of the
automorphisms of finite order, is applied to the affine Kac-Moody algebras and
their representations, to yield a new class of infinite dimensional Lie
algebras and representations. After the introduction of the horizontal and
vertical gradings, and the algorithm to find the horizontal toroidal gradings,
I discuss some general properties of the graded contractions, and compare them
with the In\"on\"u-Wigner contractions. The example of is discussed
in detail.Comment: 23 pages, Ams-Te
Production of Pairs of Sleptoquarks in Hadron Colliders
We calculate the cross section for the production of pairs of scalar
leptoquarks (sleptoquarks) in a supersymmetric model, at hadron
colliders. We estimate higher order corrections by including terms
induced by soft-gluon corrections. Discovery bounds on the sleptoquark mass are
estimated at collider energies of 1.8, 2, and 4 TeV (Tevatron), and 16 TeV
(LHC).Comment: 8 pages, REVTEX, (1 fig. available on request),
LAVAL-PHY-94-13/McGILL-94-26/SPhT-94-07
On the electrodynamics of moving bodies at low velocities
We discuss the seminal article in which Le Bellac and Levy-Leblond have
identified two Galilean limits of electromagnetism, and its modern
implications. We use their results to point out some confusion in the
literature and in the teaching of special relativity and electromagnetism. For
instance, it is not widely recognized that there exist two well defined
non-relativistic limits, so that researchers and teachers are likely to utilize
an incoherent mixture of both. Recent works have shed a new light on the choice
of gauge conditions in classical electromagnetism. We retrieve Le
Bellac-Levy-Leblond's results by examining orders of magnitudes, and then with
a Lorentz-like manifestly covariant approach to Galilean covariance based on a
5-dimensional Minkowski manifold. We emphasize the Riemann-Lorenz approach
based on the vector and scalar potentials as opposed to the Heaviside-Hertz
formulation in terms of electromagnetic fields. We discuss various applications
and experiments, such as in magnetohydrodynamics and electrohydrodynamics,
quantum mechanics, superconductivity, continuous media, etc. Much of the
current technology where waves are not taken into account, is actually based on
Galilean electromagnetism
Galilei invariant theories. I. Constructions of indecomposable finite-dimensional representations of the homogeneous Galilei group: directly and via contractions
All indecomposable finite-dimensional representations of the homogeneous
Galilei group which when restricted to the rotation subgroup are decomposed to
spin 0, 1/2 and 1 representations are constructed and classified. These
representations are also obtained via contractions of the corresponding
representations of the Lorentz group. Finally the obtained representations are
used to derive a general Pauli anomalous interaction term and Darwin and
spin-orbit couplings of a Galilean particle interacting with an external
electric field.Comment: 23 pages, 2 table
Casimir invariants for the complete family of quasi-simple orthogonal algebras
A complete choice of generators of the center of the enveloping algebras of
real quasi-simple Lie algebras of orthogonal type, for arbitrary dimension, is
obtained in a unified setting. The results simultaneously include the well
known polynomial invariants of the pseudo-orthogonal algebras , as
well as the Casimirs for many non-simple algebras such as the inhomogeneous
, the Newton-Hooke and Galilei type, etc., which are obtained by
contraction(s) starting from the simple algebras . The dimension of
the center of the enveloping algebra of a quasi-simple orthogonal algebra turns
out to be the same as for the simple algebras from which they come by
contraction. The structure of the higher order invariants is given in a
convenient "pyramidal" manner, in terms of certain sets of "Pauli-Lubanski"
elements in the enveloping algebras. As an example showing this approach at
work, the scheme is applied to recovering the Casimirs for the (3+1)
kinematical algebras. Some prospects on the relevance of these results for the
study of expansions are also given.Comment: 19 pages, LaTe
Amplitude Zeros in Radiative Decays of Scalar Particles
We study amplitude zeros in radiative decay processes with a photon or a
gluon emission of all possible scalar particles(e.g. scalar leptoquarks) which
may interact with the usual fermions in models beyond the standard model. For
the decays with a photon emission, the amplitudes clearly exhibit the
factorization property and the differential decay rates vanish at specific
values of a certain variable which are determined only by the electric charges
of the particles involved and independent of the particle masses and the
various couplings. For the decays with a gluon emission, even though the zeros
are washed away, the differential decay rates still have distinct minima. The
branching ratios as a function of leptoquark masses are presented for the
scalar leptoquark decays. We also comment on the decays of vector particles
into two fermions and a photon.Comment: Revtex, 17 pages + 6 figures (available upon request), Preprint,
OITS559. Several typos with tex file were correcte
On the bicrossproduct structures for the family of algebras
It is shown that the family of deformed algebras has a different bicrossproduct
structure for each in analogy to the undeformed case.Comment: Latex2e file. 14 page
Leptoquark pair production at the Fermilab Tevatron: Signal and backgrounds
We perform a Monte-Carlo simulation of scalar leptoquark pair production at
the Tevatron (energy =1.8 TeV and luminosity =100 pb^{-1}) with ISAJET. We also
investigate the dominant sources of Standard Model background: Z*jj, ZZ
production and heavy quark top-antitop. We find that the top-antitop background
is the most important except near the Z pole where the Z*jj background is
peaked. We also evaluate the signal-to-background ratio and find a discovery
reach of 130 GeV (170 GeV) for a branching ratio of B(LQ-> eq)=0.5 (B=1).Comment: 8 pages, 6 figures, latex (revtex
Flux moduli stabilisation, Supergravity algebras and no-go theorems
We perform a complete classification of the flux-induced 12d algebras
compatible with the set of N=1 type II orientifold models that are T-duality
invariant, and allowed by the symmetries of the T^6/(Z_2 x Z_2) isotropic
orbifold. The classification is performed in a type IIB frame, where only H_3
and Q fluxes are present. We then study no-go theorems, formulated in a type
IIA frame, on the existence of Minkowski/de Sitter (Mkw/dS) vacua. By deriving
a dictionary between the sources of potential energy for the three moduli (S, T
and U) in types IIA and IIB, we are able to combine algebra results and no-go
theorems. The outcome is a systematic procedure for identifying
phenomenologically viable models where Mkw/dS vacua may exist. We present a
complete table of the allowed algebras and the viability of their resulting
scalar potential, and we point at the models which stand any chance of
producing a fully stable vacuum.Comment: Version published in JHE
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