49,672 research outputs found
Quark and lepton masses from top loops
Assuming that the leptons and quarks other than top are massless at tree
level, we show that their masses may be induced by loops involving the top
quark. As a result, the generic features of the fermion mass spectrum arise
from combinations of loop factors. Explicitly, we construct a renormalizable
model involving a few new particles, which leads to 1-loop bottom and tau
masses, a 2-loop charm mass, 3-loop muon and strange masses, and 4-loop masses
for first generation fermions. This realistic pattern of masses does not
require any symmetry to differentiate the three generations of fermions. The
new particles may produce observable effects in future experiments searching
for mu to e conversion in nuclei, rare meson decays, and other processes.Comment: 29 pages; Introduction expanded, references adde
Two monopoles of one type and one of another
The metric on the moduli space of charge (2,1) SU(3)
Bogomolny-Prasad-Sommerfield monopoles is calculated and investigated. The
hyperKahler quotient construction is used to provide an alternative derivation
of the metric. Various properties of the metric are derived using the
hyperKahler quotient construction and the correspondence between BPS monopoles
and rational maps. Several interesting limits of the metric are also
considered.Comment: 48 pages, LaTeX, 2 figures. Typos corrected. Version in JHE
Spatio-temporal variation in the structure of a deep water Posidonia oceanica meadow assessed using non-destructive techniques
The Malta-Comino Channel (Maltese islands, central Mediterranean), supports
extensive meadows of the seagrass Posidonia oceanica that in some places
extend to a depth of around 43 m, which is rare for this seagrass. To assess
spatial and temporal variation in the state of the deeper parts of the P. oceanica
meadow with time, data on the structural characteristics of the seagrass meadow
at its lower bathymetric limit were collected during the summers of 2001,
2003 and 2004 from four stations (two stations within each of two sites)
located at a similar depth, over a spatial extent of 500 m. Shoot density was
estimated in situ, while data on plant architecture (number of leaves, mean leaf
length, and epiphyte load) were successfully obtained using an underwater photographic
technique that was specifically designed to avoid destructive sampling
of the seagrass. Results indicated that P. oceanica shoot density was lower than
that recorded from the same meadow during a study undertaken in 1995; the
observed decrease was attributed to the activities of an offshore aquaculture
farm that operated during the period 1995â2000 in the vicinity of the meadow.
ANOVA indicated significant spatial and temporal variations in meadow structural
attributes at both sites during the 3-year study; for example, shoot density
values increased overall with time at site A; a indication of potential recovery
of the meadow following cessation of the aquaculture operations. Lower shoot
density values recorded from site B (compared with site A) were attributed to
higher epiphyte loads on the seagrass, relative to those at site A. The findings,
which include new data on the structural characteristics of P. oceanica occurring
at depths >40 m, are discussed with reference to the use of the nondestructive
photographic technique to monitor the state of health of deep water
seagrass meadows.peer-reviewe
Collapse of the quantum correlation hierarchy links entropic uncertainty to entanglement creation
Quantum correlations have fundamental and technological interest, and hence
many measures have been introduced to quantify them. Some hierarchical
orderings of these measures have been established, e.g., discord is bigger than
entanglement, and we present a class of bipartite states, called premeasurement
states, for which several of these hierarchies collapse to a single value.
Because premeasurement states are the kind of states produced when a system
interacts with a measurement device, the hierarchy collapse implies that the
uncertainty of an observable is quantitatively connected to the quantum
correlations (entanglement, discord, etc.) produced when that observable is
measured. This fascinating connection between uncertainty and quantum
correlations leads to a reinterpretation of entropic formulations of the
uncertainty principle, so-called entropic uncertainty relations, including ones
that allow for quantum memory. These relations can be thought of as
lower-bounds on the entanglement created when incompatible observables are
measured. Hence, we find that entanglement creation exhibits complementarity, a
concept that should encourage exploration into "entanglement complementarity
relations".Comment: 19 pages, 2 figures. Added Figure 1 and various remarks to improve
clarity of presentatio
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