137,263 research outputs found
Determination of the String Scale in D-Brane Scenarios and Dark Matter Implications
We analyze different phenomenological aspects of D-brane constructions.
First, we obtain that scenarios with the gauge group and particle content of
the supersymmetric standard model lead naturally to intermediate values for the
string scale, in order to reproduce the value of gauge couplings deduced from
experiments. Second, the soft terms, which turn out to be generically non
universal, and Yukawa couplings of these scenarios are studied in detail.
Finally, using these soft terms and the string scale as the initial scale for
their running, we compute the neutralino-nucleon cross section. In particular
we find regions in the parameter space of D-brane scenarios with cross sections
in the range of -- pb, i.e. where current dark matter
experiments are sensitive. For instance, this can be obtained for .Comment: Figures improved, misprints corrected, results basically unchange
F-structures and integral points on semiabelian varieties over finite fields
Motivated by the problem of determining the structure of integral points on
subvarieties of semiabelian varieties defined over finite fields, we prove a
quantifier elimination result for certain modules over finite simple extensions
of the integers given together with predicates for orbits of the distinguished
generator of the ring.Comment: 33 pages, correction made to authors' informatio
From probabilities to categorical beliefs: Going beyond toy models
According to the Lockean thesis, a proposition is believed just in case it is highly probable. While this thesis enjoys strong intuitive support, it is known to conflict with seemingly plausible logical constraints on our beliefs. One way out of this conflict is to make probability 1 a requirement for belief, but most have rejected this option for entailing what they see as an untenable skepticism. Recently, two new solutions to the conflict have been proposed that are alleged to be non-skeptical. We compare these proposals with each other and with the Lockean thesis, in particular with regard to the question of how much we gain by adopting any one of them instead of the probability 1 requirement, that is, of how likely it is that one believes more than the things one is fully certain of
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