Phys.Rev. D54 (1996) 2814-2828 In the presence of fermionic matter the topologically distinct vacua of the
standard model are metastable and can decay by tunneling through the sphaleron
barrier. This ...process annihilates one fermion per doublet due to the anomalous
non-conservation of baryon and lepton currents and is accompanied by a
production of gauge and Higgs bosons. We present a numerical method to obtain
local bounce solutions which minimize the Euclidean action in the space of all
configurations connecting two adjacent topological sectors. These solutions
determine the decay rate and the configuration of the fields after the
tunneling. We also follow the real time evolution of this configuration and
analyze the spectrum of the created bosons. If the matter density exceeds some
critical value, the exponentially suppressed tunneling triggers off an
avalanche producing an enormous amount of bosons.
Phys.Lett. B378 (1996) 194-200 High-density fermion matter is meta-stable due to the anomalous
non-conservation of baryon and lepton numbers in the electroweak theory. The
meta-stable state decays by ...penetrating the sphaleron barrier separating
topologically different vacua. The decay happens locally, and results in an
annihilation of twelve fermions, accompanied by a production of gauge and Higgs
bosons. We find numerically local bounce solutions determining the decay rate,
which are classical paths in imaginary time, connecting two adjacent
topological sectors. We also follow the real-time evolution of the bosonic
fields after the tunneling and analyze the spectrum of the created bosons.
Phys.Rev. D49 (1994) 6864-6882 In this revised version we have improved the treatment of the top and bottom
quark mass. This leads to slight changes of the numerical results, especially
of those ...presented in Fig.4. The discussion of the numerical procedure and
accuracy has been extended.
In the presence of fermionic matter the topologically distinct vacua of the standard model are metastable and can decay by tunneling through the sphaleron barrier. This process annihilates one ...fermion per doublet due to the anomalous non-conservation of baryon and lepton currents and is accompanied by a production of gauge and Higgs bosons. We present a numerical method to obtain local bounce solutions which minimize the Euclidean action in the space of all configurations connecting two adjacent topological sectors. These solutions determine the decay rate and the configuration of the fields after the tunneling. We also follow the real time evolution of this configuration and analyze the spectrum of the created bosons. If the matter density exceeds some critical value, the exponentially suppressed tunneling triggers off an avalanche producing an enormous amount of bosons.
High-density fermion matter is meta-stable due to the anomalous non-conservation of baryon and lepton numbers in the electroweak theory. The meta-stable state decays by penetrating the sphaleron ...barrier separating topologically different vacua. The decay happens locally, and results in an annihilation of twelve fermions, accompanied by a production of gauge and Higgs bosons. We find numerically local bounce solutions determining the decay rate, which are classical paths in imaginary time, connecting two adjacent topological sectors. We also follow the real-time evolution of the bosonic fields after the tunneling and analyze the spectrum of the created bosons.
In this revised version we have improved the treatment of the top and bottom quark mass. This leads to slight changes of the numerical results, especially of those presented in Fig.4. The discussion ...of the numerical procedure and accuracy has been extended.
Phys.Lett.B336:457-463,1994 The baryon number dissipation rate due to sphaleron transitions at high
temperatures in the minimal standard model is evaluated. We find that this rate
can be considerably ...suppressed by one loop contributions of bosonic and
fermionic fluctuations which are particularly important for a small mass of the
Higgs boson and a large top quark mass. Fixing the latter to its recently
stated value of 174 GeV the complete erasure of the baryon asymmetry is
prevented within the framework of the minimal standard model if the Higgs mass
is less than about 66 GeV.
The baryon number dissipation rate due to sphaleron transitions at high temperatures in the minimal standard model is evaluated. We find that this rate can be considerably suppressed by one loop ...contributions of bosonic and fermionic fluctuations which are particularly important for a small mass of the Higgs boson and a large top quark mass. Fixing the latter to its recently stated value of 174 GeV the complete erasure of the baryon asymmetry is prevented within the framework of the minimal standard model if the Higgs mass is less than about 66 GeV.
The planned expansion of biofuel plantations in Brazil could potentially cause both direct and indirect land-use changes (e.g., biofuel plantations replace rangelands, which replace forests). In this ...study, we use a spatially explicit model to project land-use changes caused by that expansion in 2020, assuming that ethanol (biodiesel) production increases by 35 (4) x 10⁹ liter in the 2003-2020 period. Our simulations show that direct land-use changes will have a small impact on carbon emissions because most biofuel plantations would replace rangeland areas. However, indirect land-use changes, especially those pushing the rangeland frontier into the Amazonian forests, could offset the carbon savings from biofuels. Sugarcane ethanol and soybean biodiesel each contribute to nearly half of the projected indirect deforestation of 121,970 km² by 2020, creating a carbon debt that would take about 250 years to be repaid using these biofuels instead of fossil fuels. We also tested different crops that could serve as feedstock to fulfill Brazil's biodiesel demand and found that oil palm would cause the least land-use changes and associated carbon debt. The modeled livestock density increases by 0.09 head per hectare. But a higher increase of 0.13 head per hectare in the average livestock density throughout the country could avoid the indirect land-use changes caused by biofuels (even with soybean as the biodiesel feedstock), while still fulfilling all food and bioenergy demands. We suggest that a closer collaboration or strengthened institutional link between the biofuel and cattle-ranching sectors in the coming years is crucial for effective carbon savings from biofuels in Brazil.
Land-use and land-cover change are important drivers of global environmental change, affecting the state of biodiversity, the global carbon cycle, and other aspects of the earth system. In this ...article we describe the development of the land-use model LandSHIFT, which aims to simulate land-use and land-cover change on the continental and global scale. The model is based on a “land-use systems” approach, which describes the interplay between anthropogenic and environmental system components as drivers of land-use change. LandSHIFT’s modular structure facilitates the integration of different components that cover key parts of land-use systems. The model prototype combines a module for the simulation of land-use change dynamics with a module for calculating crop yields and net primary productivity of grassland. LandSHIFT is driven by country-level model inputs including time-series of socio-economic variables as well as agricultural production data. This information is regionalized to land-use grid maps with a cell size of 5 arc-minutes. Here, the model clearly differentiates between the land-use activities settlement, crop cultivation and grazing. By using standardized input–output formats, LandSHIFT can be combined with other models for conducting complex simulation studies.
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