5,147 research outputs found
Ground state entanglement in quantum spin chains
A microscopic calculation of ground state entanglement for the XY and
Heisenberg models shows the emergence of universal scaling behavior at quantum
phase transitions. Entanglement is thus controlled by conformal symmetry. Away
from the critical point, entanglement gets saturated by a mass scale. Results
borrowed from conformal field theory imply irreversibility of entanglement loss
along renormalization group trajectories. Entanglement does not saturate in
higher dimensions which appears to limit the success of the density matrix
renormalization group technique. A possible connection between majorization and
renormalization group irreversibility emerges from our numerical analysis.Comment: 26 pages, 16 figures, added references, minor changes. Final versio
The flavor of neutrinos in muon decays at a neutrino factory and the LSND puzzle
The accurate prediction of the neutrino beam produced in muon decays and the
absence of opposite helicity contamination for a particular neutrino flavor
make a future neutrino factory the ideal place to look for the lepton flavor
violating (LFV) decays of the kind \mu^+\ra e^+\nuebar\numu and lepton number
violating (LNV) processes like \mu^-\ra e^-\nue\numu. Excellent sensitivities
can be achieved using a detector capable of muon and/or electron identification
with charge discrimination. This would allow to set experimental limits that
improve current ones by more than two orders of magnitude and test the
hypothesis that the LSND excess is due to such anomalous decays, rather than
neutrino flavor oscillations in vacuum.Comment: 19 pages, 4 figure
Teología en América Latina, vol. III. El siglo de las teologías latinoamericanistas (1899-2001). [Reseña]
Reseña de: Josep Ignasi SARANYANA (dir.)- Carmen-José
ALEJOS GRAU (coord.), Teología en América
Latina, vol. III. El siglo de las teologías latinoamericanistas
(1899-2001), Iberoamericana-
Vervuert, Madrid-Frankfurt am Main 2002,
774 pp
Isolation mediates persistent founder effects on zooplankton colonisation in new temporary ponds
Understanding the colonisation process in zooplankton is crucial for successful restoration of aquatic ecosystems. Here, we analyzed the clonal and genetic structure of the cyclical parthenogenetic rotifer Brachionus plicatilis by following populations established in new temporary ponds during the first three hydroperiods. Rotifer populations established rapidly after first flooding, although colonisation was ongoing throughout the study. Multilocus genotypes from 7 microsatellite loci suggested that most populations (10 of 14) were founded by few clones. The exception was one of the four populations that persisted throughout the studied hydroperiods, where high genetic diversity in the first hydroperiod suggested colonisation from a historical egg bank and, no increase in allelic diversity was detected with time. In contrast, in another of these four populations, we observed a progressive increase of allelic diversity. This population became less differentiated from the other populations suggesting effective gene flow soon after its foundation. Allelic diversity and richness remained low in the remaining two, more isolated, populations, suggesting little gene flow. Our results highlight the complexity of colonisation dynamics, with evidence for persistent founder effects in some ponds, but not in others, and with early immigration both from external source populations, and from residual, historical diapausing egg banks
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