73,097 research outputs found
String Unification and Leptophobic in Flipped SU(5)
We summarize recent developments in the prediction for ,
self-consistent string unification and the dynamical determination of mass
scales, and leptophobic gauge bosons in the context of stringy flipped
SU(5). [To appear in Proceedings of Fourth International Conference on
Supersymmetry (SUSY96), University of Maryland (May 1996).]Comment: 5 pages, LaTeX (uses espcrc2.sty), 5 figures (included
A Layman's guide to SUSY GUTs
The determination of the most straightforward evidence for the existence of
the Superworld requires a guide for non-experts (especially experimental
physicists) for them to make their own judgement on the value of such
predictions. For this purpose we review the most basic results of Super-Grand
unification in a simple and clear way. We focus the attention on two specific
models and their predictions. These two models represent an example of a direct
comparison between a traditional unified-theory and a string-inspired approach
to the solution of the many open problems of the Standard Model. We emphasize
that viable models must satisfy {\em all} available experimental constraints
and be as simple as theoretically possible. The two well defined supergravity
models, and , can be described in terms of only a few
parameters (five and three respectively) instead of the more than twenty needed
in the MSSM model, \ie, the Minimal Supersymmetric extension of the Standard
Model. A case of special interest is the strict no-scale
supergravity where all predictions depend on only one parameter (plus the
top-quark mass). A general consequence of these analyses is that supersymmetric
particles can be at the verge of discovery, lurking around the corner at
present and near future facilities. This review should help anyone distinguish
between well motivated predictions and predictions based on arbitrary choices
of parameters in undefined models.Comment: 25 pages, Latex, 11 figures (not included), CERN-TH.7077/93,
CTP-TAMU-65/93. A complete ps file (1.31MB) with embedded figures is
available by request from [email protected]
Exploring Discourse Ethics for Tourism Transformation
The 'critical turn' in tourism studies is defined as a research perspective that explores social transfor- mation in and through tourism by facing the negative impact of strategic-instrumental rationality on this activity. This work explores the features of discourse ethics that may normatively support tourism transformation, a gap that has not been thoroughly discussed in tourism research. For this purpose, the study combines the use of critical and ethical theory with an analysis of discourse ethics in tourism literature to demonstrate that the use of Habermasian discourse ethics needs to be complemented with the Apelian approach. Through these steps the work reveals the theoretical bases of discourse ethics to discuss whether understandings between stakeholders guided by strategic-instrumental rationality can be reached not only in the political sphere âHabermasâ, but also in the ethical field âApel
Vanishing Str M^2 in the presence of anomalous U_A(1)
We show that the presence of an anomalous factor in the gauge
group of string-derived models may have the new and important phenomenological
consequence of allowing the vanishing of in the
``shifted" vacuum, that results in the process of cancelling the anomalous . The feasibility of this effect seems to be enhanced by a vanishing
vacuum energy, and by a ``small" value of in the
original vacuum. In the class of free-fermionic models with vanishing vacuum
energy that we focus on, a necessary condition for this mechanism to be
effective is that in the original vacuum. A vanishing
ameliorates the cosmological constant problem and is a
necessary element in the stability of the no-scale mechanism.Comment: 7 pages, no figures, LaTe
M-theory Inspired No-scale Supergravity
We propose a supergravity model that contains elements recently shown to
arise in the strongly-coupled limit of the heterotic string
(M-theory), including a no-scale--like K\"ahler potential, the identification
of the string scale with the gauge coupling unification scale, and the onset of
supersymmetry breaking at an intermediate scale determined by the size of the
eleventh dimension of M-theory. We also study the phenomenological consequences
of such scenario, which include a rather constrained sparticle spectrum within
the reach of present-generation particle accelerators.Comment: 8 pages, LaTeX, 3 figures (included
New Precision Electroweak Tests of SU(5) x U(1) Supergravity
We explore the one-loop electroweak radiative corrections in supergravity via explicit calculation of vacuum-polarization and
vertex-correction contributions to the and
parameters. Experimentally, these parameters are obtained from a global fit to
the set of observables , and . We
include -dependent effects, which induce a large systematic negative shift
on for light chargino masses (m_{\chi^\pm_1}\lsim70\GeV). The
(non-oblique) supersymmetric vertex corrections to \Zbb, which define the
parameter, show a significant positive shift for light chargino
masses, which for can be nearly compensated by a negative
shift from the charged Higgs contribution. We conclude that at the 90\%CL, for
m_t\lsim160\GeV the present experimental values of and
do not constrain in any way supergravity in
both no-scale and dilaton scenarios. On the other hand, for m_t\gsim160\GeV
the constraints on the parameter space become increasingly stricter. We
demonstrate this trend with a study of the m_t=170\GeV case, where only a
small region of parameter space, with \tan\beta\gsim4, remains allowed and
corresponds to light chargino masses (m_{\chi^\pm_1}\lsim70\GeV). Thus
supergravity combined with high-precision LEP data would
suggest the presence of light charginos if the top quark is not detected at the
Tevatron.Comment: LaTeX, 11 Pages+4 Figures(not included), the figures available upon
request as an uuencoded file(0.4MB) or 4 PS files from [email protected],
CERN-TH.7078/93, CTP-TAMU-68/93, ACT-24/9
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