22,482 research outputs found
Particle production in string cosmology models
We compute spectra of particles produced during a dilaton-driven kinetic
inflation phase within string cosmology models. The resulting spectra depend on
the parameters of the model and on the type of particle and are quite varied,
some increasing and some decreasing with frequency. We use an approximation
scheme in which all spectra can be expressed in a nice symmetric form, perhaps
hinting at a deeper symmetry of the underlying physics. Our results may serve
as a starting point for detailed studies of relic abundances, dark matter
candidates, and possible sources of large scale anisotropy.Comment: 20 pages, no figures, latex, RevTe
General Rotating Black Holes in String Theory: Greybody Factors and Event Horizons
We derive the wave equation for a minimally coupled scalar field in the
background of a general rotating five-dimensional black hole. It is written in
a form that involves two types of thermodynamic variables, defined at the inner
and outer event horizon, respectively. We model the microscopic structure as an
effective string theory, with the thermodynamic properties of the left and
right moving excitations related to those of the horizons. Previously known
solutions to the wave equation are generalized to the rotating case, and their
regime of validity is sharpened. We calculate the greybody factors and
interpret the resulting Hawking emission spectrum microscopically in several
limits. We find a U-duality invariant expression for the effective string
length that does not assume a hierarchy between the charges. It accounts for
the universal low-energy absorption cross-section in the general non-extremal
case.Comment: 33 pages, latex; minor typos corrected; version to appear in PR
Searching by approximate personal-name matching
We discuss the design, building and evaluation of a method to access theinformation of a person, using his name as a search key, even if it has deformations. We present a similarity function, the DEA function, based
on the probabilities of the edit operations accordingly to the involved
letters and their position, and using a variable threshold. The efficacy
of DEA is quantitatively evaluated, without human relevance judgments,
very superior to the efficacy of known methods. A very efficient
approximate search technique for the DEA function is also presented
based on a compacted trie-tree structure.Postprint (published version
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