19,199 research outputs found
Three-Loop Calculation of the Anyonic Full Cluster Expansion
We calculate the perturbative correction to every cluster coefficient of a
gas of anyons through second order in the anyon coupling constant, as described
by Chern-Simons field theory.Comment: 10 pages, PlainTex with macro 'manumac', include
On Core Collapse Supernovae in Normal and in Seyfert Galaxies
This paper estimates the relative frequency of different types of
core-collapse supernovae, in terms of the ratio f between the number of type
Ib--Ic and of type II supernovae. We estimate f independently for all normal
and Seyfert galaxies whose radial velocity is <=14000 km/s, and which had at
least one supernova event recorded in the Asiago catalogue from January 1986 to
August 2000. We find that the ratio f is approx. 0.23+/-0.05 in normal
galaxies. This value is consistent with constant star formation rate and with a
Salpeter Initial Mass Function and average binary rate approx. 50 %. On the
contrary, Seyfert galaxies exceed the ratio f in normal galaxies by a factor
approx. 4 at a confidence level >= 2 sigma. A caveat is that the numbers for
Seyferts are still small (6 type Ib-Ic and 6 type II supernovae discovered as
yet). Assumed real, this excess of type Ib and Ic with respect to type II
supernovae, may indicate a burst of star formation of young age (<= 20 Myr), a
high incidence of binary systems in the inner regions (r <= 0.4 R25) of Seyfert
galaxies, or a top-loaded mass function.Comment: Accepted for Publication in MNRA
Decaying warm dark matter and neutrino masses
Neutrino masses may arise from spontaneous breaking of ungauged lepton
number. Due to quantum gravity effects the associated Goldstone boson - the
majoron - will pick up a mass. We determine the lifetime and mass required by
cosmic microwave background observations so that the massive majoron provides
the observed dark matter of the Universe. The majoron DDM scenario fits nicely
in models where neutrino masses arise a la seesaw, and may lead to other
possible cosmological implications.Comment: 4 pages, 3 figures. Replaced to match published version. Minor
changes made to address referees' comments. References adde
Status of three-neutrino oscillations after the SNO-salt data
We perform a global analysis of neutrino oscillation data in the framework of
three neutrinos, including the recent improved measurement of the neutral
current events at SNO. In addition to all current solar neutrino data we take
into account the reactor neutrino data from KamLAND and CHOOZ, the atmospheric
neutrino data from Super-Kamiokande and MACRO, as well as the first spectral
data from the K2K long baseline accelerator experiment. The up-to-date best fit
values and allowed ranges of the three-flavour oscillation parameters are
determined from these data. Furthermore, we discuss in detail the status of the
small parameters alpha = Delta_m^2_Sol / Delta_m^2_Atm and sin^2(theta_13),
which fix the possible strength of CP violating effects in neutrino
oscillations.Comment: 16 pages, LaTeX file using RevTEX4, 10 figures and 1 table included.
The conclusions reached in version 1 regarding the restriction on
sin^2(theta_13) are now corrected, the solar bound is weaker than that from
reactors even after the inclusion of the SNO salt data. In addition the full
data set has now been reanalized using the pull method instead of the
standard chi-square approach. A few references have also been adde
Planck-scale effects on WIMP dark matter
There exists a widely known conjecture that gravitational effects violate
global symmetries. We study the effect of global-symmetry violating
higher-dimension operators induced by Planck-scale physics on the properties of
WIMP dark matter. Using an effective description, we show that the lifetime of
the WIMP dark matter candidate can satisfy cosmological bounds under reasonable
assumptions regarding the strength of the dimension-five operators. On the
other hand, the indirect WIMP dark matter detection signal is significantly
enhanced due to new decay channels.Comment: 12 pages, 4 figures. Version accepted for publication in Frontier
Concepts and Actors in Organic Livestock Husbandry in Bolivia
Traditional smallholder livestock production is expected to correspond widely with principles of organic livestock farming. Though, the real magnitude of livestock under organic and alike management is unknown. From stakeholder analysis and structured interviews with key persons in Bolivia it is deduced that similarities are widely given, whereas it is questioned whether a formal individual certification approach for livestock products will match the farmer interests and consumer demands
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