19,443 research outputs found
Chern-Simons number asymmetry from CP violation at electroweak tachyonic preheating
We consider the creation of non-zero Chern-Simons number in a model of the
early Universe, where the Higgs field experiences a fast quench at the end of
inflation and subsequently rolls down its potential barrier. Neglecting the
expansion, we perform numerical lattice simulations in the Abelian Higgs model
in 1+1 dimensions with an added phenomenological C and P violating term during
this stage of so-called tachyonic preheating. The results suggest that even the
sign of the Chern-Simons and thus baryon number is dependent on the ratio of
the Higgs to W mass. We also discuss the appropriate choice of vacuum initial
conditions for classical simulations.Comment: 24 pages, 17 figures, added references, published versio
Real-time dynamics in the 1+1 D abelian Higgs model with fermions
In approximate dynamical equations, inhomogenous classical (mean) gauge and
Higgs fields are coupled to quantized fermions. The equations are solved
numerically on a spacetime lattice. The fermions appear to equilibrate
according to the Fermi-Dirac distribution with time-dependent temperature and
chemical potential.Comment: LATTICE99 (electroweak) talk presented by J. Smit, 3 pages, 4
figures, LaTex, espcrc2.st
Finite ma corrections for sea quark matrix elements
We discuss the finite corrections associated with the computation of sea
quark matrix elements. We find them to differ from the standard normalization
used for valence quarks and to depend strongly on the Lorentz structure of the
current under consideration. Phenomenological implications of these results are
briefly discussed in two examples. We also mention how the magnitude of the
correction factors can be reduced by using a 2-link improved action.Comment: 3 pages, contribution to LATTICE'94, uuencoded compressed tar file
(square root removed in equation (1)
Sphaleron transition rate at high temperature in the 1+1 D abelian Higgs model
New results for the rate are presented using the canonical ensemble in the
classical approximation on a spatial lattice. We find that the rate at high
temperatures is proportional to , and strongly dependent on the lattice
spacing . We conclude that a better effective action is needed for the
classical approximation.Comment: 3 pages, uuencoded compressed postscript file, contribution to the
Conference Proceedings "LATTICE 94", Bielefeld- German
Sphaleron transition rate in the classical 1+1 dimensional abelian Higgs model at finite temperature
We compute the sphaleron transition rate in the 1+1 dimensional abelian Higgs
model at finite temperature, by real time simulation using the classical
canonical ensemble.Comment: 3 pages to appear in the Proceedings of Lattice '93, Dallas, Texas,
12-16 October 1993, comes as a single postscript file (LaTeX source available
from the authors), ITFA 93-3
Impact and extinction signatures in complete Cretaceous-Tertiary (K-T) boundary sections
The Zumaya, Caravaca and Agost sections in Spain, the El Kef section in Tunisia and the Negev (Nahal Avdat) sections in Israel are among the most continuous, expanded and complete K-T boundary sections. The distribution patterns of the planktic faunas were quantitatively analyzed in closely spaced samples across the K-T boundary in these sections, in conjuction with the geochemistry, stable isotopes, mineralogy and magnetostratigraphy. Three hundred foraminiferal specimens were randomly selected and determined. Reliable estimates for the foraminiferal productivity changes across the K-T boundary and for the 1 to 2 Ma interval preceding the K-T boundary were made from the numbers of individuals/gram of sediment corrected for the sedimentation rates (calculated from magnetic reversals and lithology). No gradual or stepwise extinction is seen below the K-T boundary nor any productivity decrease. Stable isotope analyses show a warming just after deposition of the ejecta layer, not cooling as predicted by nuclear winter scenarios, although the duration of such cooling may be too short to be observed even in these complete sections. Low REE values and cpx spherules with quench textures idential to quench-textures in diagenetically altered spherules, strongly indicate an oceanic site of (one of) the impactor(s)
Lattice Computation of a Magnetic Monopole Mass
A single magnetic monopole in pure SU(2) gauge theory is simulated on the
lattice and its mass is computed in the full quantum theory. The results are
relevant for our proposed realization of the dual superconductor hypothesis of
confinement.Comment: 3 pages PostScript, to appear in the Proceedings of IMACS93 (St.
Louis, USA, Oct. 1993). Registration numbers ITFA-93-38 (Amsterdam),
DFTUZ/93/21 (Zaragoza
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